CROJFE - Volume 27, Issue 2

27

Issue 2

2006

2

Editorial

At the end of the second (27th) volume Dear Readers!

At the end of the second year of publishing the journal CROJFE, the Editorial Board of the journal and I myself as the Editor-in-Chief are expected to draw the line and pose some questions: what have our past activities been like and what are their results; have we achieved most of our plans and goals; why some good ideas planned by the journal management failed to be achieved or have been achieved only partly despite great efforts and endeavours of many people engaged in its everyday life; has CROJFE reached the expected quality both in terms of content and form; are we pursuing the right and the best possible way; how can we be better, more successful, more efficient, more interesting, more actual, more global, more identifiable, etc.

Our calendar year is also nearing its end so time has come to settle the outstanding issues and enter into the New Year without any burdens, with clear visions and possibly without past pledges (which consume human creative energy).

The posed questions, as well as those implied, ask for an answer. However, it is not always easy to give the right answer. We will try to be fair and true to you, our readers, and to ourselves. This is not the guarantee, but it can absolutely be the basis for a brighter and better future of your and our journal.

The journal CROJFE relies (legally and formally) on past tradition, experience and topics (which have been broadened, up-dated and adapted to contemporary events) of the journal of Forest Mechanisation. Together with our designers, we have tried to choose the solutions of current visual identity of the journal as a logical historical and development sequence. The new Editorial Board of the journal proved to be a good productive combination of youth, fresh and new ideas, creative energy and enthusiasm on one hand and experience, thorough knowledge, rationality and peace on the other.

The Editorial Board is mostly made of people from the Department of Forest Techniques and Technologies of the Faculty of Forestry of the University of Zagreb. It is, however, hard to imagine the activities of the Editorial Board without the Editor, MSc. @eljko Toma{i}, Head of the Development Department of the company »Croatian Forests» Ltd. Zagreb, who is the connection between the scientific aspect of publishing and operational practice, which has to recognise the results of the published papers and apply them as much as possible (we can easily agree that researches carried out in the field of forest engineering are mostly applicable). The Editorial Adviser, who gives a significant contribution to the final version of CROJFE by his proposals, suggesCroatian Journal of Forest Engineering 27(2006)2

tions and ideas, Professor in retirement Stanislav Sever (in the past also a member of our Department) is an undisputed authority in the area of publishing journals dealing with biotechnological science in Croatia.

Editor-in-Chief and Technical Editor as well as the members of the Technical Editorial Board are primarily university teachers and colleagues who, along with their everyday obligations related to teaching and scientific work at the Faculty, find time for editing the journal CROJFE and preparing it for printing. And we must admit that it is not always easy. It is often necessary to take a lot of free time to meet the required deadlines, work is often done in the afternoon, during weekends and in the final phase before printing we also spent many nights together working at the Faculty of Forestry.

However, we are not complaining. We are just presenting facts. Still, all problems are forgotten the very moment a new issue of the journal is released from print or when a new paper arrives for review in the Editor’s Office or when an enquiry is received by e-mail on the possibility of subscription to the journal or when some of our colleagues, scientists or practitioners, praises by phone some article as interesting or useful. A member of the Editorial Board has recently asked »Has the baby arrived from the printing house« thinking of course of the new issue of CROJFE. Further comments regarding the attitude of the members of the Editorial Board toward the journal and its place in our hearts are not required.

In the near future, with the support of the Ministry of Science, Education and Sport (that has started co-financing the publication of CROJFE this year, for which we are particularly thankful), we hope to be able to engage a promising young specialist in our Department, who would primarily deal with the publications of the Department and not with teaching and scientific research (in the specification of jobs this is the position of Junior Editor – Assistant to the Editor-in-Chief).

All issues of the journal CROJFE have so far been released on time, and the evaluation process has been initiated for introducing the journal into scientific citation databases Current Contents and Science Citation Index Expanded. We are aware that this is a demanding and time-consuming process and however this is one of our basic goals and hence it will be fulfilled. If some additional modifications, changes and improvements of the journal are required, in accordance with the recommendations of the assessment committees, they will be taken into consideration as soon as possible. The journal is also regularly quoted in bibliographic databases as referred to in the journal’s contents page. In

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future we will absolutely try to broaden the list of bibliographic databases referring to CROJFE. In two years, more than 20 papers of renounced domestic and foreign authors have been published in four issues of CROJFE. All papers were reviewed by international leading experts recognised in their respective fields, and hence their quality usually meets the set requirements. The lists of reviewers are large and they are regularly up-dated with new reviewers. In this way the best possible assessment of an individual scientific paper submitted for publishing is provided by competent experts, and the time period from receiving the paper and sending the results of review to the authors is never more than two months.

CROJFE’s WEB has been designed (mostly thanks to Mr. Igor Stanki}, dipl. ing. for., member of the Technical Editorial Board of the journal) presenting a lot of useful information on the journal as well as each issue of the journal in PDF format completely free of charge. The Editorial Board had the dilemma whether to charge the access to the electronic version of the journal or not.

However, we have chosen the latter option, even though our financial situation is not the best (we are aware that it never is), as we have estimated that the promotional effect of the journal will, in the long run, highly exceed the financial effect that would be achieved by downloading texts from the WEB page of the journal. And we were right. The number of enquiries for the submission of papers to be published in CROJFE showed a daily increasing tendency after the introduction of the electronic version of the journal, as well as the number of enquires on conditions and procedure of subscription and finally the number and quality of articles sent for review.

Our intent is to modernise and regularly up-date the WEB page of the journal, as well as to complete it with the articles published before in the issues of the journal of Forest Engineering (the legal predecessor of CROJFE). This journal has a 27-year long history. In this way the continuity will be provided of the electronic version of the journal as well as its completeness.

Although we are aware that this job is very complex and time consuming, and we know well that this proposed project will interfere with our everyday activities related to the current issues of the journal CROJFE, we are also aware of the fact that the journal with no past or no respect for its past cannot have a bright future.

Most of our goals for 2005 and 2006 set in the Plan and Programme of Activities of the journal CROJFE for the period from 2005 to 2009 have already been reached. Minor deviations from the Plan are the result of circumstances thoroughly or mostly beyond our control.

The same applies to wishes and ideas of the journal management that could not be fulfilled or have been fulfilled only partly. The reasons lie primarily in the lack of funds for financing additional activities (e.g. more frequent meetings of the Editorial Board and International Editorial Board with the aim of upgrading the journal, more frequent participation of the members

At the end of the second (27th) volume (67–68)

of the Editorial Board at domestic and international conferences, larger editions, etc.).

In our opinion, the journal CROJFE reached an enviable quality both in terms of content and form, by which we are satisfied considering the fact that this team has only worked together for a year now, but still we want to be better and achieve more as soon as possible.

Our wish is to provide as many as possible papers of good quality by domestic, European and world leading experts in the field of forest engineering, who should recognise our journal as one of the most significant journals in this segment of forestry within Europe. If we had at our disposal a larger number of reviewed and accepted scientific papers in time, we would be able to publish thematic issues of the journal.

We will do our best to improve the use of English in our journal, contributing thus to the globalisation of CROJFE. We will insist on extended abstracts in Croatian at the end of the papers, with the aim of promoting the journal in the Croatian forestry and in order to increase the possibilities of implementation of research results.

The cooperation with the company »Croatian Forests« Ltd. Zagreb is at a rather enviable level. This company provides the funds for financing our journal and without this support CROJFE would not exist. The management of the company is aware of our needs and problems and they meet our requirements all the time in accordance with their possibilities and with short-term and long-term business policy of the company. However, we hope for an even better and more frequent communication in future, which should result in further improvement of cooperation between the Editorial Board of the journal CROJFE and »Croatian Forests« Ltd. Zagreb, especially now when the »debts« of the old Editorial Board have been settled. It should be emphasised that these debts were mostly a result of serious and unpredictable problems of as far as 5 years ago.

To be specific a special edition of the journal New Forest Mechanisation 2001–2004 was released in the English and Croatian version in late October of the current year and it included 41 papers (a four-year volume that due to legal reasons could not have the title Forest Mechanisation, and these are in fact the Proceedings of the International Conference – Emerging Harvesting Issues and Technology Transition at the End of the Century, held under the sponsorship of IUFRO in Opatija from September 27 to October 1, 1999.

Although much more could be written about the present topic, in my opinion what has been written so far is quite enough for a critical analysis of the achievements of the journal CROJFE with the basic guidelines for its future activities.

And at the end of this Editorial, dear readers, contributors, colleagues and friends, the Editorial Board of the journal CROJFE wishes you and your families a Merry Christmas and a very happy and successful New Year 2007 with plenty of health, peace, happiness, prosperity and success in life.

Tibor Pentek

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Croatian Journal of Forest Engineering 27(2006)2

Uvodnik

Na kraju drugoga (dvadesetsedmoga) godi{ta Po{tovani ~itatelji!

Na izmaku druge godine izla`enja ~asopisa CROJFE du`nost je Uredni{tva ~asopisa, ponajprije mene kao glavnoga urednika, podvu}i crtu i postaviti odre|ena pitanja: kakve su nam bile dosada{nje aktivnosti i kojim su one plodovima urodile; jesmo li ostvarili ve}i dio zacrtanih planova i postavljenih ciljeva; za{to odre|ene planirane i `eljene ideje ~elni{tva ~asopisa unato~ velikomu trudu i anga`manu brojnih ljudi uklju~enih u njegov svakodnevni `ivot nisu ostvarene ili su ostvarene djelomi~no; je li CROJFE dostigao `eljenu kakvo}u sadr`ajem i formom, idemo li pravim, najboljim mogu}im putem; kako biti jo{ bolji, uspje{niji, u~inkovitiji, zanimljiviji, aktualniji, prisutniji u svijetu, prepoznatljiviji itd. Tako|er je i kalendarski kraj godine kada je uvijek dobro srediti ra~une te u idu}u godinu u}i rastere}en, s jasnim vizijama i po mogu}nosti bez hipoteka iz pro{losti (koje rasipaju kreativnu energiju ~ovjeka).

Navedena, ali i ona nenabrojena pitanja tra`e odgovore. A njih nije uvijek lako ispisati. Poku{ajmo biti objektivni te prema vama, ~itateljima, i prema sebi samima iskreni. To je, ne}u re}i, jamstvo, ali zasigurno zalog i dobar temelj jo{ svjetlije i ljep{e budu}nosti va{ega i na{ega ~asopisa. ^asopis CROJFE naslonjen je (i pravno i formalno) na tradiciju, iskustvo i tematiku (koja je ipak donekle pro{irena, aktualizirana te prilago|ena vremenu i suvremenim doga|anjima) ~asopisa Mehanizacija {umarstva. Nastojali smo, u dogovoru s grafi~kim dizajnerima, odabrati ona rje{enja aktualnoga vizualnoga identiteta ~asopisa koja su logi~an povijesni i razvojni slijed. I novo je Uredni{tvo ~asopisa tako|er jedna, pokazalo se zahvalna i produktivna, kombinacija mladosti, svje`ih i novih ideja, stvarala~ke energije i poleta, s jedne strane, te iskustva, bogatoga znanja, racionalnosti i smirenosti, s druge strane.

Uredni{tvo ~ine ve}inom ljudi iz Zavoda za {umarske tehnike i tehnologije [umarskoga fakulteta Sveu~ili{ta u Zagrebu, ali je uspje{an rad Uredni{tva nezamisliv bez odgovornoga urednika mr. sc. @eljka Toma{i}a, rukovoditelja Razvojne slu`be poduze}a »Hrvatske {ume« d.o.o. Zagreb, koji je spona izme|u izdava~ke sastavnice znanosti i operative koja mora prepoznati rezultate objavljenih radova te u suglasju s mogu}nostima to i primijeniti u praksi (slo`it }emo se da su istra`ivanja iz {umarskoga in`enjerstva ponajvi{e primjenjiva karaktera). Savjetnik je Uredni{tva, koji svojim prijedlozima, sugestijama i idejama uvelike doprinosi kona~noj ina~ici CROJFE-a, umirovljeni prof. dr. sc. Stanislav Sever (prije tako|er ~lan na{ega Zavoda), zasigurno ~ovjek koji je neprijeporni autoritet u podru~ju publiciranja ~asopisa iz podru~ja biotehni~kih znanosti u Hrvatskoj.

Croatian Journal of Forest Engineering 27(2006)2

Glavni su i tehni~ki urednik te ~lanovi tehni~koga uredni{tva sveu~ili{ni nastavnici i suradnici, koji uz svoje obveze u nastavnoj i znanstvenoj sastavnici fakultetske svakodnevnice pronalaze vremena za ure|ivanje i pripremu za tisak ~asopisa CROJFE. A moramo re}i kako to nije uvijek lako. ^esto je potrebno izdvojiti dobar dio svoga slobodnoga vremena kako bi se ispunili zadani rokovi, radi se poslije podne, vikendima, a u zavr{noj fazi pripreme ~asopisa za tisak nisu bile rijetke i no}i koje smo zajedno probdjeli na [umarskom fakultetu.

No, ne `alimo se. Samo iznosimo ~injenice. Ipak, na sve se probleme zaboravi onoga trenutka kada iz tiska izi|e novi broj ~asopisa, ili kada na recenziju u Uredni{tvo stigne novi rad, ili onda kada e-po{tom stigne upit o mogu}nosti pretplate na ~asopis, ili kada telefonski netko od kolega iz znanstvenih krugova odnosno prakse pohvali poneki ~lanak, njegovu zanimljivost ili primjenjivost. Netko je od ~lanova Uredni{tva nedavno pitao: »Je li iz tiskare stigla zavodska beba«, misle}i naravno na novi broj CROJFE-a. Daljnji komentari u svezi s odnosom ~lanova Uredni{tva prema ~asopisu te njegovu mjestu u na{im srcima nisu potrebni.

U skorijoj se budu}nosti nadamo kako }emo uz potporu Ministarstva znanosti, obrazovanja i {porta (koje od ove godine sufinancira izdavanje CROJFE-a, na ~emu smo mu posebno zahvalni) biti u mogu}nosti anga`irati sposobnoga mladoga stru~njaka u na{em Zavodu koji bi se primarno bavio ne nastavom, ne istra`ivanjima, ve} tiskovinama Zavoda (u sistematizaciji radnih mjesta to je radno mjesto mladoga urednika – asistenta glavnoga urednika).

Svi su dosada{nji brojevi ~asopisa CROJFE izi{li na vrijeme, a pokrenut je i postupak uklju~ivanja ~asopisa u bibliografske baze podataka Current Contents i Science Citation Index Expanded. Svjesni smo kako je to zahtjevan i dugotrajan postupak, no to je jedan od na{ih osnovnih zacrtanih ciljeva od kojega ne}emo odstupiti.

Eventualno potrebne dorade, preinake i pobolj{anja ~asopisa, sukladno preporukama prosudbenih povjerenstava, odradit }emo u najkra}em mogu}em roku. ^asopis se uredno citira i u sekundarnim bazama podataka kako je navedeno u njegovu impresumu. Zasigurno }emo u idu}em razdoblju nastojati pro{iriti popis sekundarnih baza podataka koje }e referirati CROJFE. U dvije je godine, u ~etiri broja CROJFE-a, objavljeno vi{e od 20 radova uglednih doma}ih i stranih autora. Svi su radovi pro{li stroge me|unarodne recenzije vode}ih stru~njaka iz podru~ja kojim se tematski bave te su na taj na~in prili~no ujedna~ene, propisane kakvo}e. Recenzentski su popisi opse`ni i svakim se danom dopunjuju novim imenima. Time je osigurano

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da kompetentni strani stru~njaci {to je najbolje mogu}e procijene pojedini znanstveni rad koji je pristigao radi objave, a razdoblje od primitka rada do slanja rezultata recenzije autorima iznosi najvi{e dva mjeseca.

Dizajnirana je mre`na stranica CROJFE-a (za {to je ponajvi{e zaslu`an Igor Stanki}, dipl. in`. {um., ~lan tehni~koga uredni{tva ~asopisa) na kojoj se osim mno{tva korisnih informacija o samom ~asopisu mo`e prona}i svaki pojedini broj ~asopisa u pdf formatu, i to potpuno besplatno. Postojala je dvojba Uredni{tva ho}e li se napla}ivati ili ne napla}ivati pristup elektroni~koj verziji ~asopisa, no odlu~ili smo se, unato~ nepovoljnoj financijskoj situaciji (svjesni smo da ona nigdje nije sjajna), za ovu drugu opciju jer smo procijenili da }e u~inak promid`be ~asopisa, dugoro~no gledano, vi{estruko nadma{iti financijski u~inak koji bi se ostvario od prihoda dobivenoga od skidanja tekstova s mre`ne stranice ~asopisa. I bili smo u pravu. Broj upita o mogu}nosti slanja radova za objavu u CROJFE-u, broj upita o uvjetima i proceduri pretplate i kona~no broj pristiglih ~lanaka na recenziranje i njihova kakvo}a rasli su, nakon uvo|enja elektroni~ke verzije ~asopisa, iz dana u dan.

Mre`nu }emo stranicu ~asopisa osuvremeniti, nastojimo ju redovito a`urirati, a `elimo ju dopuniti ~lancima objavljenima u svim dosada{njim brojevima ~asopisa Mehanizacija {umarstva (koje je CROJFE pravni sljednik). Radi se o 27-godi{njoj povijesti ~asopisa. Tako }e se osigurati kontinuitet i cjelovitost elektroni~ke verzije ~asopisa. Iako smo svjesni slo`enosti i dugotrajnosti toga posla, a znamo kako }e taj predvi|eni projekt kolidirati sa svakodnevnim aktivnostima povezanima s aktualnim brojevima ~asopisa CROJFE, poznata nam je i ~injenica kako ~asopis koji nema ili ne cijeni svoju pro{lost ne mo`e imati svjetlu budu}nost.

Ve}inu smo ciljeva za 2005. i 2006. godinu, zacrtanih u Planu i programu aktivnosti ~asopisa CROJFE u razdoblju od 2005. do 2009, ispunili. Manja odstupanja od Plana rezultat su objektivnih okolnosti na koje nismo mogli ili smo mogli vrlo malo utjecati. Isto se odnosi na neostvarivanje ili djelomi~no ostvarivanje odre|enih `elja i ideja manad`menta ~asopisa. Uzroci su ponajprije le`ali u manjku financijskih sredstava za dodatne aktivnosti (npr. ~e{}i sastanci uredni~koga i me|unarodnoga uredni~koga vije}a radi unapre|ivanja ~asopisa, ~e{}e sudjelovanje ~lanova Uredni{tva na doma}im i me|unarodnim skupovima, ve}a naklada ~asopisa i dr.). ^asopis je CROJFE po na{oj, nadajmo se, objektivnoj procjeni dostigao zavidnu razinu i sadr`ajem i formom kojom smo, s obzirom na to da ovaj tim zajedno radi tek godinu dana, zadovoljni, no mi ipak `elimo vi{e i bolje, i to {to prije.

Na kraju drugoga (dvadesetsedmoga) godi{ta (69–70)

@elja nam je osigurati ve}i broj vrsnih radova doma}ih i stranih, europskih i izvaneuropskih vode}ih stru~njaka u podru~ju {umarskoga in`enjerstva koji bi na{ ~asopis trebali prepoznati kao jedan od vode}ih i klju~nih ~asopisa iz ovoga segmenta {umarstva u Europi. Temeljem pravodobne ve}e mogu}nosti izbora recenziranih i prihva}enih znanstvenih radova bili bismo u mogu}nosti tiskati tematske brojeve ~asopisa.

Nastojat }e se jo{ pobolj{ati engleski jezik u ~asopisu i time pridonijeti globalizaciji CROJFE-a. Inzistirat }emo na {irim hrvatskim sa`ecima na kraju radova radi promid`be ~asopisa u hrvatskoj {umarskoj praksi, radi pove}anja mogu}nosti primjene rezultata istra`ivanja te radi izgra|ivanja stru~noga hrvatskoga nazivlja.

Suradnja s glavnim financijerom ~asopisa tvrtkom »Hrvatske {ume« d.o.o. Zagreb, bez koje bi opstojnost CROJFE-a bila nezamisliva, vrlo je uspje{na, manad`ment poduze}a ima sluha za na{e potrebe i probleme te nam u svakoj prilici, prema svojim mogu}nostima, kratkoro~nom i dugoro~nom poslovnom politikom dru{tva izlazi ususret. No, ipak se u budu}nosti nadamo jo{ boljoj i ~e{}oj me|usobnoj komunikaciji, koja bi trebala iznjedriti daljnji pomak u suradni~kim odnosima na relaciji Uredni{tvo ~asopisa CROJFE – »Hrvatske {ume« d.o.o. Zagreb, poglavito sada kada smo ra{~istili »dugove« staroga Uredni{tva (koji su, to se mora naglasiti, nastali vi{e kao rezultat objektivnih, nepredvidljivih i u vremenima od prije pet godina te{ko rje{ivih problema).

Naime, u posebnom izdanju ~asopisa Nova mehanizacija {umarstva 2001 – 2004. (~etverogodi{njak koji zbog formalno-pravnih razloga ne mo`e nositi naslov Mehanizacija {umarstva, a u biti je Zbornik me|unarodnoga savjetovanja Iskrsli problemi u iskori{tavanju {uma pri tranziciji tehnologija na kraju stolje}a, odr`anoga pod pokroviteljstvom IUFRO-a u Opatiji od 27. rujna do 1. listopada 1999. godine), koji je u engleskoj i hrvatskoj ina~ici izi{ao iz tiska krajem listopada ove godine, objavljen je 41 rad.

Iako bi se o predmetnoj tematici dugo moglo promi{ljati i misli pretakati na papir, smatramo da je za jednu kriti~ku analizu dosada{njega rada i djelovanja ~asopisa CROJFE uz osnovne smjernice budu}ih aktivnosti ovo {to je napisano prava mjera.

I na kraju ovoga uvodnika, po{tovani ~itatelji, suradnici, kolege i prijatelji, Uredni{tvo ~asopisa CROJFE iskreno vama i va{im obiteljima od srca `eli blagoslovljen Bo`i}, sretnu i uspje{nu novu, 2007. godinu, uz obilje zdravlja, mira, sre}e, veselja, blagostanja i uspjeha u `ivotu.

Tibor Pentek

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Croatian Journal of Forest Engineering 27(2006)2

Original scientific paper

Natural composition of tree species as a basis for model development of stumpage price Bo{tjan Ko{ir, @ivko Ko{ir, Janez Kr~ Abstract – Nacrtak Model development and use play a significant role in research and forest management of Slovenian forests. As co-natural and sustainable forest management is traditional, it is essential to rely on available knowledge of the composition of natural plant associations.

This paper describes the need for stumpage price modelling, and the basic concept of developing models which can behave dynamically as forest structure approaches the final goal – tree composition close to nature. The main plant associations in Slovenia and their characteristic tree structure represent the so called model goal. Input data are taken from forest inventory base and are compared with the model goal. The difference between the model and true tree structure together with growth and other variables gives the intensity and structure of prescribed annual cut and consequently the value of wood assortments. The model produced several possible scenarios for the next decades, and this has already proved to be a good basis for decision making.

Keywords: plant associations, stumpage price, forest management, model

1. Introduction – Uvod Forest inventory base in Slovenia comprises a vast collection of data, which is barely used for more complex analyses. On the other hand there is vast interest in long term forecasts at different levels. The greatest interest is shown by some forest companies and large forest owners. The Forest Act prescribes co-natural, sustainable and multifunctional forest management, which should also support biodiversity and have respect for the social aspect of forests.

Obviously the knowledge of the natural state of the forest vegetation is essential in searching the best alternatives of the future forest development.

The picture of the tree composition of natural forest vegetation association in the past can only be got with two groups of variables. In the first group intensive human-related factors are found with the related erosion processes. At the beginning these factors had been connected with existential needs of settlers, but later the commercial use of forest became more important. The demands have also been influenced by today’s silvicultural concepts. The second group of factors is presented by natural ability of forest regeneration, which has been restored in dependence on the natural forest plant association, Croatian Journal of Forest Engineering 27(2006)2

and that still happens in recent succession. During this progressive process not all of the past stand structures have been reconstructed, and the differences in their age structure still remain visible. Changed age structures strongly influence the share of tree species with shorter life span.

The central part of Slovenia has always been heavily covered with the natural forest. Regeneration of the forest is very strong, and within the natural vegetation associations, also very fast. The mosaic of the stand development phases can indicate their succession stages, thus making possible the following of their whole recent succession. The small-scale ownership structure of Slovenian forest have contributed a lot to the knowledge about succession stages, as small parts of the forest mix together with known historical development.

Studies of potential forest vegetation have always been based on the knowledge of their succession. However, the definition of single association has been based on studies of the most undisturbed forest stands, which were the closest to their original natural structure and form (Ko{ir 1979, Ko{ir 1992, Ko{ir 1994). Today these forests belong to commercial forests of different silvicultural concepts, but mostly in optimal development phases. Such

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Natural composition of tree species as a basis for model development of stumpage price (71–80)

studies can provide very limited knowledge about their further development toward the original virgin forest forms, but as forests are managed with essentially shortened natural cyclic time rotation – one half or even less – the figures of the characteristic natural composition of potential forest vegetation become even more important. The results of such studies are an excellent base for the estimate of natural tree structure of forest vegetation associations in present silvicultural forms.

2. The need for modeling – Potreba za modeliranjem Forest management is closely and traditionally related to natural development of forest stands. Despite many man-made changes, the potential state of forest has recently been the most important basis for making short and long term decisions. For many years, traditional methods of forest inventory had been sufficient for obtaining data needed for making decisions about allowed annual cut, intensity and frequency of thinnings, the beginning of regeneration and many other specific measures in the forest.

These methods are not sufficient for developing projections of forest development for a longer period of time and accordingly for providing the necessary investments in the forest as the basis for technologic solutions of prescribed measures. The revenues from the forest and stumpage values on a larger time scale can only be computed with the help of an appropriate model. There are yet many other possibilities which are available through model employment and, however, they are not within the scope of this paper (Kr~ 1995, Kr~ 1999b).

The number of variables which have significant influence on making decisions is also increasing, as there is a growing demand for including different forest functions into our decisions. The need to build tools for decision making is therefore very urgent, and it demands the skill of computer programming, understanding the forest management general demands, technological knowledge and an excellent knowledge of the potential natural state of forests (Ko{ir 1997).

3. Methods – Metode The basic assumption was that the model could be used for describing nondeterministic system with many stochastic variables, and it triggered the beginning of the research. Such work demands the involvement of the experts from different fields of forest science, but the expected result is worth the effort. Complexity, flexibility and dynamics are the

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main characteristics to be met during the model development. Dynamics plays a special role as it depends on the input status of the chosen variables, final goal to be achieved and procedures to be applied for achieving the goal.

In the Slovenian co-natural forest management the final long-term goal is determined by the composition of tree species which is close to the potential natural state of forest stand (Ko{ir 1975, Ko{ir 1976).

Plant associations that are the most important from the forest management point of view, as well as some others that cover larger areas in the Submediterranean part of Slovenia or have very narrow ecological scope, are presented in Appendix 1.

In accordance with the task, this paper presents the potential tree structure of plant associations with the stress on the carriers of the growing stock. Tree species, which are minorities with similar growth and life span, are summoned in separate groups. The group of high value broadleaf trees that are common in mountainous terrain consists of the following species: Acer pseudoplatanus L., Acer platanoides L., Ulmus glabra Huds., Fraxinus excelsior L. and rarely Tilia platyphyllos Scop. In the forests of flatland and hills we can find in the same group: Ulmus laevis Pallas, Fraxinus oxycarpa Willd. (F. angustifolia), Alnus glutinosa (L.) Gaertn. and Tilia cordata Mill. In the group of hard broadleaf species of the low land forest, there are: Carpinus betulus L. and beside also Acer campestre L., Prunus avium L. and Sorbus torminalis (L.) Cr. On slightly higher altitudes the following species in the same group prevail: Ostrya carpinifolia Scop., Sorbus aria (L.) Cr., Quercus cerris L. and Sorbus aucuparia L. A separate group of soft broadleaf trees, which appear as followers from lowland to the lower mountains, consists of the following species: Popupus tremula L., Populus alba L., Salix alba L., Betula pendula Roth. and Alnus incana (L.) Moench. The share of the most important tree species in the growing stock is defined separately. These species are: Picea abies (L.) Karst., Abies alba Mill., Larix decidua Mill., Pinus sylvestris L., Pinus nigra Arnold, Fagus sylvatica L., Quercus robur L., Quercus petraea (Matt.) Liebl. in Acer pseudoplatanus L. The tree species structure, which is the closest to the structure of some associations in the neighbouring countries is that of prealpine beech forest and mixed forests of silver fir and beech. There are, however, significant differences in the structure of tree species shown in Appendix 1 and similar associations in Switzerland and Austria (Zukrigel 1973, Mucina et al. 1993, Oberdorfer 1992a, Oberdorfer 1992b, Ellenberg 1996). Let us look at some examples. In the Slovenian mixed silver fir–beech forests on limestone the share of spruce is significantly lower, the Croatian Journal of Forest Engineering 27(2006)2

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Fig. 1 Differences among potential and current shares in growing stock of joined groups of tree species Slika 1. Razlike izme|u mogu}ih i sada{njih udjela u drvnoj zalihi skupina vrsta drve}a share of silver fir is higher, and only in some varieties of the association the beech prevails. In Eastern Alps the similar association of silver fir–beech (besides higher share of Norway spruce) gets also some Scots pine. The Norway spruce in Slovenia on the other hand does not cover vast Subalpine areas as it does in neighbouring countries, but we can find it on extreme sites, on silicate or dolomite bedrock, on rocky ground all the way to the lowland. On some sites the Scots pine appears making mixed forests together with spruce trees. The forests of high value broadleaf lack Tilia platyphyllos Scop. On the other hand Acer platanoides L. gets a more important role and can in some cases even prevail in the tree structure of a certain site. A special structure is also characteristic of beech forest on extreme silicates where Norway spruce has a good natural vitality. Such forest can in other cases have similarities with lowland silver fir forests on silicate bedrock. In the Western Slovenia in the coast direction the share of Illyric tree species becomes encreasingly larger, but these

are already the specialities of the Submediterranean area.

Input data for each forest stand have been taken from the Slovenian forest data base, which is maintained by the Slovenian Public Forest Service and comprises 78,667 entries for the area of 1,116,206 ha of forests. Many of the forest stands have been drastically changed by the management in the history because of different reasons. Some privately owned areas have been overexploited or changed according to the needs of forest owners; on the other hand some areas have been changed into merely spruce stands or influenced in many other ways. Despite such changes, the majority of forests have remained in more or less co-natural state, which is especially true for the state forests.

4. Results – Rezultati The examination of the differences between the current and potential vegetation cover is of great

Table 1 Determination of scenarios for approaching natural stand structures varying thinning intensities and rotation period Tablica 1. Odre|ivanje nacrta gospodarenja za prevo|enje sastojina u prirodnu strukturu mijenjanjem intenziteta proreda i duljina ophodnji Thinning Intensity – Intenzitet prorede Weak – Slab Mean – Umjeren Strong – Jak

120 years – 120 godina Scenario 1 – Nacrt 1 Scenario 4 – Nacrt 4 Scenario 7 – Nacrt 7

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Rotation period – Duljina ophodnje 140 years – 140 godina Scenario 2 – Nacrt 2 Scenario 5 – Nacrt 5 Scenario 8 – Nacrt 8

160 years – 160 godina Scenario 3 – Nacrt 3 Scenario 6 – Nacrt 6 Scenario 9 – Nacrt 9

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Fig. 2 Model predicting average growing stock development in forest management unit according to different scenarios Slika 2. Model predvi|anja prosje~noga razvoja drvne zalihe gospodarske jedinice pri razli~itim nacrtima gospodarenja interest since it is important for the model behaviour. The greater the difference, the longer the period of adaptation to the closer-to-nature state of forests. The intensity of thinning also depends upon this difference, as well as many other outputs of the model. The differences among the potential and current shares in growing stock of the joined groups of tree species are shown in Figure 1 (source of the current vegetation shares: The Forest Development Programme of Slovenia, 1995).

Briefly, as shown in Fig. 1, the greatest difference is caused by the disproportion of the Norway spruce share in growing stock in the past. If the final goal is the co-natural forest structure, more intensive cuttings are expected in spruce stands in the next decades. The priorities should be given to those tree species, which are at present almost minorities, but with great natural potential (Kr~ 1999a, Kr~ 1999b).

The final goal of forest development dynamics in the model is determined in Appendix 1. The input status is determined by the forest inventory base, and there is only the question of procedures, which are built into the model. Those procedures are out of the scope of this paper, but we wish to emphasise the fact that various paths to the final goal have been researched within the time range of 90 years. Alternative forest management scenarios were defined by the rotation period and thinning intensity (Table 1), which was controlled by the target state of stand

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structure. The target stand structure was defined by the tree species volume composition suitable for the specific site plant association and with respect to the current forest development phase.

The model has been tested so far in a case study of one forest management unit in the Alpine region, and we tested the impact of rotation period and thinning intensity on the final result. Simulations showed that the intensity of cuttings and given priorities influence the final success (Kr~ 1999). The influence of the length of rotation period has also an important impact on higher or lower stumpage values. One of the elementary figures is shown in Fig. 2. The best scenarios for obtaining the highest growing stock in the period up to 2080 are 3, 6 and 9, which means (Table 1) a very long rotation period of 160 years. Within this choice weak thinning intensity will yield the best results – the highest growing stock with the tree composition, which will not differ very much from the present one. »Volume« and »Value« are many times on the opposite sides of the formula.

It is hard to predict which option is the best from the point of view of stumpage price. Further analysis must still be done with a more detailed consideration of the technology costs and trends of market prices.

Dependence of stumpage value on cost and stand value is broadly known (Winkler 1996) and will not be discussed in this paper. Our interest was focused Croatian Journal of Forest Engineering 27(2006)2

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Table 2 Proportions between cutting volumes according to different rotation periods and thinning intensities Tablica 2. Odnosi izme|u obujma posje~enoga drva za razli~ite duljine ophodnji i intenzitete proreda Thinning Intensity – Intenzitet prorede Rotation period – Duljina ophodnje Thinning – Proreda Final cutting – Dovr{na sje~a Total – Ukupno

120 100 100 100

Weak – Slab 140 171 84 105

160 250 65 110

120 100 100 100

Mean – Umjeren 140 160 170 244 82 62 106 113

120 100 100 100

Strong – Jak 140 170 83 106

160 246 63 112

Fig. 3 Model predicting stumpage prices according to different scenarios Slika 3. Model predvi|anja cijena drva na panju pri razli~itim nacrtima gospodarenja on stand development as a basis for stumpage price and other calculations. Simple, but not precisely accurate assumptions are: higher increment = more wood = higher stumpage price and to be specific: more softwood = higher stumpage price.

It can be seen in Table 2 that there are not very big differences between thinning intensities within the same rotation period. A longer production period nevertheless means greater cutting volume. The structure of the cutting volume gives very different results in the first several decades (Fig. 3). At the end of modelled time span the differences between scenarios will decrease and will be less than 20% of the basic stumpage price. This final period will also be the time where co-natural structure of the forest will be normal and the differences in production periods in the majority of stands will not be crucial. The Croatian Journal of Forest Engineering 27(2006)2

similarity between scenarios in this light is therefore normal/expected.

The whole forecasting period can be divided into three time intervals, the results of which are influenced by current (initial) strand structures (year 2010), where older development phases in Forest Management Unit prevail: 1. From 2010 to 2050 where the best result is obtained by short rotation scenarios and the worst by long rotation period scenarios; 2. From 2050 to 2070 where the differences between different scenarios are small, but short production periods are already in the worst position; 3. From 2070 to 2100 where the differences between scenarios go up and down following the tendency that the lowest stumpage prices are achieved by short rotation periods.

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5. Discussion – Rasprava Models of forest development dynamics can be/ constitute an excellent base for many other calculations, but their accuracy depends upon the procedures and input data. In our case the crucial base of the model is the natural state of tree species according to the main vegetation types. This table was developed on the basis of broad knowledge about the vegetation composition and succession of natural plant associations in Slovenia. Discrepancies between the goal and the actual state of a specific stand can be very large in extremes, but the problem of co-natural forest management for the majority of forests can be solved with satisfying accuracy. Despite this, further investigations of plant association succession on sensitive or devastated sites are still needed. The model showed that the worst case for the owner (lowest stumpage price) in the next decades is the case with long production periods, the best are scenarios with short rotation periods, where unnatural spruce stand are converted to co-natural structure in three decades. In the far future the situation will change when longer production periods show slightly higher stumpage prices. Further model development and promotion of their use are also of the outmost importance. Additionally, there is urgent need for future research of the forest stumpage correlated with technological development and investment in the forest.

Ko{ir, B., 1997: Building a Tool for Multilevel Planning. A Preliminary Report Seminar IUFRO S3.04, 16. –20. 6. 1997, Madrid.

Ko{ir, @., 1975 and 1976: Vrednotenje gozdnega prostora po varovalnem in lesnoproizvodnem pomenu na osnovi naravnih razmer. Zasnova uporabe prostora – gozdarstvo, Zavod SR Slovenije za dru`beno planiranje in In{tituta gozdno in lesno gospodarstvo pri Biotehni{ki fakulteti, Ljubljana, 145 p.

Ko{ir, @., 1979: Ekolo{ke, fitocenolo{ke in gozdnogospodarske lastnosti Gorjancev v Sloveniji. University of Ljubljana, Biotechnical Fac., Dep. of Forestry and Forest Resources, Research Rep. 17, Ljubljana, 242 p.

Ko{ir, @., 1992: Vrednotenje proizvodne sposobnosti rasti{~ in ekolo{kega zna~aja fitocenoz. Ministry of Agriculture, Forestry and Food, Ljubljana, 58 p.

Ko{ir, @., 1994: Ekolo{ke in fitocenolo{ke razmere v gorskem in hribovitem jugozahodnem obrobju Panonije. Forestry Publ., Ljubljana, 149 p.

Kr~, J., 1995: Model napovedovanja oblik spravila lesa.

University of Ljubljana. Biotechnical Fac., Dep. of Forestry and Forest Resources, Master of Sc. Thesis, Biotehni{ka fakulteta, Ljubljana, 114 p.

Kr~, J. 1999a: Analiza spremenjenosti koli~inske in vrstne sestave gozdov po dveh razli~nih metodah ter njuna primerjava. University of Ljubljana, Biotechnical Fac., Dep. of Forestry and Forest Resources, Research Rep. 60, Ljubljana, 211–236.

Kr~, J., 1999b: Ve~kriterialno dinami~no vrednotenje tehnolo{kih, ekonomskih, socialnih in ekolo{kih vplivov na gospodarjenje z gozdovi. Doctor thesis, Ljubljana, University of Ljubljana, Biotechnical Fac., Dep. of Forestry and Forest Resources, 173 p.

6. References – Literatura

Oberdorfer, E., 1992a: Süddeutsche Pflanzengesellschaften.

Wälder und Gebüsche, Teil IV., Stuttgart – New York, 282 p.

Anon., 1995: The Forest Development Programme of Slovenia. Ministry of Agriculture, Forestry and Food, Ljubljana, 1995, 9 p.

Oberdorfer, E., 1992b: Süddeutsche Pflanzengesellschaften-Tabellenband. Wälder und Gebüsche, Teil IV, Stuttgart – New York, p. 580.

Ellenberg, H., 1996: Vegetation Mitteleuropas mit den Alpen. 5. Auflage, Stuttgart, 1094 p.

Winkler, I., 1996: Vrednotenje gozdov in gozdnih {kod.

Biotehni{ka fakulteta, Odd. za gozd., Ljubljana, 35 p.

Mucina, L., Grabherr, G., Wallnöfer, S., 1993: Die Pflanzengesellschaften Österreichs. Teil III, Stuttgart, 353 p.

Zukrigel, K., 1973: Montane und subalpine Waldgesellschaften am Alpenrand. Wien, 386 p.

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Appendix 1 Potential natural composition of the tree species according to the vegetation association, % Dodatak 1. Mogu}i prirodni sastav vrsta drve}a po biljnim zajednicama, %

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Appendix 1 Potential natural composition of the tree species according to the vegetation association, % Dodatak 1. Mogu}i prirodni sastav vrsta drve}a po biljnim zajednicama, %

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Appendix 1 Potential natural composition of the tree species according to the vegetation association, % Dodatak 1. Mogu}i prirodni sastav vrsta drve}a po biljnim zajednicama, %

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Sa`etak

Prirodni sastav vrsta drve}a kao osnova razvoja modela cijena drva na panju Razvoj i kori{tenje modela imaju va`nu ulogu u istra`ivanju i gospodarenju {umama u Sloveniji. Kako se {umama potrajno gospodari na na~in blizak prirodnomu, nu`no je osloniti se na postoje}a znanja o sastavu biljnih zajednica. Rad opisuje potrebu za modeliranjem cijena drva na panju, te osnovnu zamisao razvoja modela koji se mo`e pona{ati dinami~no kako se struktura {uma pribli`ava kona~nomu cilju – strukturi vrsta drve}a koja je bliska prirodnoj. Glavne biljne zajednice u Sloveniji i njihova svojstvena struktura drve}a predstavljaju tzv. ciljni model.

Ulazni podaci preuzeti su iz baze podataka nacionalne inventure {uma i uspore|eni s ciljnim modelom. Razlika izme|u modelom oblikovane i stvarne strukture drve}a, zajedno s rastom i drugim varijablama, daje intenzitet i strukturu propisanoga godi{njega sje~noga obujma drva (etat) te samim time i vrijednost drvnih sortimenata. Pomo}u modela razvijeno je i nekoliko mogu}ih nacrta gospodarenja za sljede}a desetlje}a, a modeli su se pokazali kao dobra osnova za dono{enje odluka. Pojedini nacrt gospodarenja odre|en je intenzitetom prorede (slaba, umjerena, jaka) i duljinom ophodnje (120, 140, 160 godina).

Modeli kretanja razvoja {uma mogu biti, odnosno ~ine izvrsnu osnovu za mnoge druge prora~une, ~ija to~nost ovisi o procedurama i ulaznim podacima. U prikazanom je slu~aju va`na osnova za model prirodan sastav vrsta drve}a prema glavnim vegetacijskim tipovima. Tablica u dodatku napravljena je na osnovi znanja o sastavu vegetacije i sukcesiji prirodnih biljnih zajednica u Sloveniji. Odstupanja izme|u ciljnoga i stvarnoga stanja pojedinih sastojina mogu u ekstremnim slu~ajevima biti vrlo velike, ali problem gospodarenja sastojinama koje su bliske prirodnima za ve}inu se mo`e rije{iti sa zadovoljavaju}om to~no{}u. Usprkos navedenomu potrebna su daljnja istra`ivanja sukcesije biljnih zajednica na osjetljivim ili o{te}enim stani{tima.

Modeli pokazuju da je u sljede}im desetlje}ima najnepovoljnija situacija za {umovlasnika (najni`a cijena drva na panju) ona s najduljim vremenom ophodnje, a najpovoljniji je nacrt gospodarenja kratke ophodnje, gdje se smrekove kulture prevode u sastojine koje su po sastavu bliske prirodnima u razdoblju od tri desetlje}a. Pretpostavka je da }e se u budu}nosti situacija promijeniti, pa }e dulje ophodnje sastojina prouzro~iti porast cijena drva na panju.

Daljnji razvoj modela i promicanje njihova kori{tenja imaju najve}e zna~enje za gospodarenje {umama. Tako|er je potrebno hitno istra`iti povezanost vrijednosti drva stoje}ega stabla s tehnolo{kim razvojem i investicijama u {umarstvu.

Klju~ne rije~i: biljne zajednice, cijena drva na panju, gospodarenje {umama, model

Authors' address – Adresa autorâ: Assoc. Prof. Bo{tjan Ko{ir, PhD. e-mail: bostjan.kosir@bf.uni-lj.si Asst. Prof. Janez Kr~, PhD. e-mail: janez.krc@bf.uni-lj.si University of Ljubljana, Biotechnical Faculty Department of Forestry and Forest Resources Ve~na pot 83 1000 Ljubljana SLOVENIA

Received (Primljeno): September 11, 2006 Accepted (Prihva}eno): November 28, 2006

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@ivko Ko{ir, PhD. Turjak 34 1311 Turjak SLOVENIA Croatian Journal of Forest Engineering 27(2006)2

Original scientific paper

Economic Comparison of the Use of Tyres, Wheel Chains and Bogie Tracks for Timber Extraction Antti Suvinen Abstract – Nacrtak Many logging operators in Finland use bogie tracks and wheel chains all the year round and under all terrain conditions. The hypothesis tested here is that bogie tracks and wheel chains increase the resistance forces, and thus fuel consumption, when operating in summer conditions and on a hard-earth forest floor. Fuel consumption was measured under such conditions using the CAN bus and GPS techniques and models were generated to simulate it in different forms of terrain and types of logging work. It was found that both wheel chains and bogie tracks increased fuel consumption under all simulated terrain conditions, the difference being quite marginal for wheel chains, but much more significant for bogie tracks.

A site size of 5 hectares was the break-even value reached in three out of four simulated terrain types that made the removal and re-installation of bogie tracks profitable when the average extraction distance was more than 600 metres.

Keywords: Tyre, wheel, bogie track, wheel chain, fuel consumption, forwarder

1. Introduction – Uvod Many logging operators in Finland use bogie tracks all year round and under all terrain conditions. The common explanation for this is that the removal and re-installation of these takes a lot of time and is too costly. In addition, the following benefits of using bogie tracks and wheel chains are quoted: Þ improved bearing capacity because of the increased tyre contact area Þ better thrust Þ the tyres remain cleaner, which improves thrust.

All these benefits are achieved especially when operating on soft terrain, e.g. on peatlands. In addition, bogie tracks and wheel chains are often necessary in winter in order to make movement possible at all.

Bearing capacity, thrust and tyre cleaning are no problem for forest tractors on hard, mineral soil terrain, and the hypothesis to be tested here is that bogie tracks and wheel chains only increase the reCroatian Journal of Forest Engineering 27(2006)2

sistance forces, and thus fuel consumption, when operating under such conditions. This is because the mass of the tractor and its internal and external friction are increased. If this hypothesis proves to be correct, the removal of bogie tracks and wheel chains might well be profitable in some cases. I will take only the economic viewpoint into account here and ignore ecological aspects such as soil disturbance and compaction. I will, however, consider the question of the conditions under which it would be economic to take bogie tracks or wheel chains off, and analyse the behaviour of various ground contact devices under different terrain conditions, so that the reasons behind the fuel consumption models can be appreciated.

This paper starts with the review of earlier work on the topic, followed by a description of the materials and methods used, including the measuring system, test programme, test tractor and its equipments. The next part introduces the results, and the discussion section at the end of the paper reviews the results and takes a look at prospects for further studies.

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Economic Comparison of the Use of Tyres, Wheel Chains and Bogie Tracks ... (81–102)

List of symbols and abbreviations – Lista simbola i kratica: a acceleration – ubrzanje, m/s2 A forest stand size – povr{ina sastojine, ha daverage average extraction distance – srednja udaljenost izvo`enja drva, m dloaded loaded drive distance – udaljenost optere}enoga kretanja, m dloading loading drive distance – udaljenost premje{tanja pri utovaru drva, m dunloaded unloaded drive distance – udaljenost neoptere}enoga kretanja, m FT total resistance – ukupni otpor, N FR rolling resistance – otpor kotrljanja, N FS slope resistance – otpor uspona, N FO obstacle resistance – otpor povr{inskih prepreka, N FW steering resistance, winding resistance – otpor upravljanja vozilom, N FL snow resistance – otpor snje`noga pokriva~a, N FI slip resistance – otpor klizanja, N hc height of the tractor’s cabin – visina kabine forvardera, mm hgc ground clearance – prohodnost vozila, mm ht height of the tractor – visina forvardera, mm i slip – klizanje kota~a, % l length of the tractor – duljina forvardera, mm m tractor mass – masa forvardera, kg npulpwood number of cycles for pulpwood – broj turnusa pri izvo`enju celuloznoga drva nsawn-timber number of cycles for sawn-timber – broj turnusa pri izvo`enju tehni~ke oblovine P power, recorded gross power on drive line – bruto snaga motora, kW rR rolling radius – polumjer kotrljanja, mm S skid – negativno klizanje kota~a, % tv vehicle tread – trag kota~a, mm v horizontal velocity of the tractor – vodoravna brzina kretanja forvardera, m/s Vha average volume of growing stock per hectare – prosje~na drvna zaliha, m3/ha Vload load volume – obujam tovara, m3 Vst sawn timber percentage – obujamni udio tehni~ke oblovine, % Vsr timber volume along the strip road – obujam izra|enoga drva uzdu` vlake, [m3/100 m] w width of the tractor – {irina forvardera, mm

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w

angular velocity of the wheel – kutna brzina kota~a, s–1

CAN

Controller Area Network – mre`ni protokol Global Positioning System – globalni pozicijski sustav Value Added Tax – porez na dodanu vrijednost

GPS VAT

Definition – definicija: site size the group of forest stands, which can be operated without translocation of forest machines by truck – skupina {umskih sastojina (radili{ta) na kojima se drvo privla~i bez premje{tanja forvardera kamionom

2. Earlier research – Prija{nja istra`ivanja There are a lot of studies of the performance of wheeled or tracked vehicles, but only a few compare ground contact devices under given terrain conditions. Wong and Huang (2006) evaluated wheels and tracks performance from a traction perspective, while Bygdén et al. (2004) studied rut depth, soil compaction and rolling resistance when using wheels or two models of bogie tracks, and reported that the relative rolling resistance did not increase when using bogie tracks but the mass of the test vehicle did, by 10–12%. They also reported that the rut depth decreased by up to 40% when using bogie tracks, although the ruts that they measured were relative shallow (2.2–8.0 cm). The effects of wheel chains and bogie tracks on fuel consumption of forwarders are a new research topic.

Fuel consumption is traditionally measured with flow meters, e.g. (Nordfjell et al. 2003), but new technologies, especially the CAN bus technique, allow more accurate, less expensive and easier test arrangements, e.g. (Rieppo and Örn 2003). The CAN bus technique makes it easier to analyse fuel consumption at a certain moment, which is crucial when defining the most important factors for fuel consumption. The development of more economical and ecological logging is possible only by identifying these crucial factors. Rieppo and Örn (2003) calculated that a 5% reduction in fuel consumption of forest tractors and timber extraction vehicles in Finland would yield savings of five million euros annually.

Favreau and Gingras (1998) reported that fuel costs account for about 10% of total harvesting costs Croatian Journal of Forest Engineering 27(2006)2

Economic Comparison of the Use of Tyres, Wheel Chains and Bogie Tracks ... (81–102)

in fellings carried out by the CTL method in Canada, while according to Johansson (2001) fuel costs can reach 20% in Sweden, where fuel prices are much higher than in North America. Fuel prices have in any case increased dramatically since the beginning of the new millennium, so that fuel costs as a proportion of total costs are nowadays probably even higher. Nordfjell et al. (2003) estimated that forwarders consumed 0.23–0.38 litre per 100 metres driven and that consumption increased by only 10% when loaded as compared with an unloaded vehicle. They also reported the average fuel consumption to be 13.3 litres per hour during final fellings and 10.5 litres per hour during thinning. Rieppo and Örn (2003) quoted average consumption for forwarders of 10.5 litres per hour, while Nordfjell et al. (2003) reported that 61–62% of fuel was consumed during loading and driving in connection with loading.

The results presented by both Rieppo and Örn (2003) and Nordfjell et al. (2003) are based on average parameters for a wide body of data, whereas detailed analyses of the effects of the conditions of the terrain and ground contact device on fuel consumption are practically ignored. Nordfjell et al. (2003) did assume, however, that under more difficult terrain conditions the use of bogie tracks and wheel chains would probably increase fuel consumption.

A. SUVINEN

3. Materials and methods – Materijal i metode 3.1 Test forwarder – Ispitivani forvarder The tractor was an 8-wheeled Timberjack 1110 forwarder registered in 1997, with about 6500 engine hours on its log. This model is powered by a sixcylinder turbo-charged diesel engine and has a hydrostatic-mechanical power transmission system which can generate a maximum pull of 150 kN. The maximum engine power is 114 kW at 37 s–1 and the maximum torque 620 Nm at 25 s–1. The dimensions of the forwarder are presented in Figure 1.

3.2 Tyres, bogie tracks and wheel chains – Gume, polugusjenice i lanci The forwarder was equipped with Nokian 710/45– 26.5 16 Forest King F SF tyres (Nokian Tyres, No year), with an inflation pressure of 350 kPa on the front bogie and 440 kPa on the rear one.

The wheel chains were manufactured from 16millimetre chain and had a mass of 400 kg per pair.

The ECO-TRACK bogie tracks, manufactured by Olofsfors (Olofsfors, No year), had a mass of 1850 kg per pair. The wheel chains were fitted to the tyres on the second and third axles, whereas the bogie tracks

Fig. 1 Dimensions of the test forwarder Slika 1. Dimenzije ispitivanoga forvardera Croatian Journal of Forest Engineering 27(2006)2

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were placed on the rear bogie (3rd and 4th axles) and were used in conjunction with wheel chains on the tyres of the second axle.

3.3 Measuring system – Mjerni sustav The measuring system consisted of a 12-channel Trimble ProXR GPS receiver with external antenna and a CAN bus data logging system. The point accuracy of the GPS receiver has been examined by Naesset (1999), who reported a mean error of 1.17 metres and a standard error of 1.07 metres below the forest canopy after a 30-minute observation period.

Veal et al. (2001), who studied the suitability of the ProXR for tracking forest machines, reported a three-dimensional mean positional error of 1.26 metres in open areas and 1.77 metres under a light forest canopy. They also reported that the tractor’s ground speed had only marginal effects on the positional error. It should be noted that a part of positional error is systematic, so that the accuracy of horizontal speed measurement is normally better than the absolute positional accuracy of the same instrument.

The present GPS data were collected in line generic mode in order to define the tractor velocity.

The data collection rate was set at one observation per second. Post-processed differential correction was applied using a base station located at Evo about 70 kilometres from the test area.

The CAN bus data logging system, which enables simultaneous measurements from three CAN buses placed in the engine’s pressure sensors, indicates the

gross power on the tractor’s drive line and the rotational speed of the drive motor.

A more detailed description of the measuring system and its sensitivity is presented by Suvinen and Saarilahti (2006). The accuracy of Trimble GeoXT GPS receiver used by Suvinen and Saarilahti (2006) is slightly inferior to that of the Trimble ProXR used here.

3.4 The test programme and conditions – Mjerni postupci i uvjeti Field tests were carried out in September 2005 near the Jämsänkoski Forest Machine School. The test trajectory, presented in Figure 2, was levelled at intervals of 2.5 metres in order to obtain an accurate terrain profile. The leveled profile is also presented in Figure 2. This profile is in fact too accurate for the terramechanical analyses, as the test tractor was almost 10 metres long, and thus an interval of 10 metres was used to construct the terrain profile for the total resistance, motion resistance coefficient, slip and fuel consumption models. Conditions during the test period were fairly constant, the weather and terrain were dry and the temperature was above zero. Since the tests were carried out in final felling areas, the forest canopy did not disturb the GPS signal reception.

A cone penetrometer was used to assess the bearing capacity of the soil. As the penetrometer measurements were made after the driving tests, the test points were located less than half a metre to one side

Fig. 2 Geographic position and profile of the test lane with penetrometer measurement points Slika 2. Zemljopisni polo`aj i profil ispitne izvozne vlake forvardera s mjestima izmjere penetrometrom 84

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of the test lane, thus representing the penetration resistance on undisturbed soil. The measurements were repeated 2–4 times at each test site and the cone index values presented in Figure 3 represent average values for one test cluster. According to Murfitt et al.

(1975), a cone index value higher than 662 kPa means that there will be no mobility problems for heavy earth-movers. This value, indicated with a vertical line in Figure 3, is exceeded at a depth of 10 cm everywhere except at measuring point F. On the other hand, the cone index values even at point F are very close to this limit value, so that it can be said that the bearing capacity on the test site was very

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high. It was in fact slightly lower on the section with an even terrain (points D, E, F and G) than on two sloping sections (points A, B, C, H, I and J), so that the cone index values support the visual observations concerning the terrain.

Based on the levelling data, penetrometer results and visual classification of the terrain, the test trajectory was split into homogeneous sections, as presented in Figure 4. This enabled more precise analysis of the influence of the terrain on the tractor mobility.

The test driver was an experienced forwarder operator who was briefed to drive through the whole

Fig. 3 Average cone penetrometer indices for ten test points Slika 3. Srednji konusni indeksi tla na deset mjernih mjesta Croatian Journal of Forest Engineering 27(2006)2

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trajectory with the same gear and at the same engine speed (number of revolutions), so that the velocity during one test drive would be more or less constant. This was done with the tractor both unloaded and loaded with spruce logs (the same quantity in all tests). The tractor was weighted unloaded and loaded, but without bogie tracks and wheel chains, using an extraction vehicle weighbridge. The mass of the bogie tracks and wheel chains was determined separately (see section 3.2).

3.5 Fuel consumption factors – ^imbenici potro{nje goriva Fuel consumption depends on the power on the drive line, with negative power readings implying that the fuel feed has stopped. Actual fuel consumption is not absolutely linear, however, as the efficiency of the engine varies a little depending on the power level. Since the engine efficiency curve for this tractor at different power levels was not known exactly, a constant specific fuel consumption of 240 g kWh–1 was used here. The actual power on the drive line is obtained four times per second from the CAN bus measurements.

The field data were used for developing fuel consumption models using the slope percentage as an explanatory variable. Fuel consumption was simulated under two sets of terrain conditions: terrain A, consisting of mild slopes (–5% to +5%), and terrain B, consisting of slopes of up to ±25%, see Figure 5.

The terrain of type A was handled by dividing the uphill and downhill slopes equally between the loaded and unloaded drives, while type B was handled in three subsets: Þ B1: Uphill and downward slopes divided equally between loaded and unloaded drives Þ B2: Unloaded drives on the downhill slope and loaded drives on the uphill slope Þ B3: Unloaded drives on the uphill slope and loaded drives on the downhill slope.

The other variables for the simulation model were: Þ forest stand size (A, ha) Þ average volume of growing stock per hectare (Vha, m3/ha) Þ sawn timber percentage (Vst, %) Þ average extraction distance (daverage, m).

The simulation models enable fuel consumption to be examined under different forest and terrain conditions using different ground contact devices.

Fuel consumption is converted to monetary values by means of a fixed unit price. Once the costs of removal and installation of the wheel chains and bogie tracks have been defined, an economic comparison of the various operational models is possible.

The calculations of the total driving distance for the forwarder are based on the report by Väkevä et al. (2001). The field data consist of unloaded drives and loaded drives with 70% of the maximum load

Fig. 4 Three sections of the test lane, an uphill slope, even terrain and a downward slope Slika 4. Tri dijela ispitne vlake: uzbrdo, ravan teren i nizbrdo 86

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Fig. 5 Distribution of slopes between the two types of simulation terrain A and B Slika 5. Distribucija nagiba kod dva tipa modeliranoga terena

mass. The maximum load mass as such is rarely reached, because the solid volume of a bunch of logs is less than the frame volume. The loading drive distance for one full load was calculated by Väkevä et al. (2001): dloading = Vload ⋅

64.864 Vsr

(1)

where the variable Vload is the load size in m3, and Vsr is the timber volume along the strip road in m3/100 m (combined volume of all roundwood assortments).

Väkevä et al. (2001) reported that under average Finnish logging conditions this value is 8–25 m3/100 m in the case of thinnings and 15–50 m3/100 m for final fellings. For the present purpose the value was fixed at 30 m3/100 metres.

According to Väkevä et. al. (2001) the loaded and unloaded drives can be calculated as follows: dloaded = daverage –

dloading 2

dloaded = 2 ⋅ daverage – dloading

(2) (3)

As the present field data do not include any information on driving with a smaller load size, no reliable information for a loading drive is available.

The loading drive distance is divided in half, and one half is included in the unloaded drive and the other in the loaded drive. Thus, based on Eqs. 1, 2 Croatian Journal of Forest Engineering 27(2006)2

and 3, the unloaded and loaded drive distances can be calculated by means of Eq. 4: dloaded = dunloaded = daverage +

dloading 2

(4)

The number of driving times is obtained by dividing the total volume by the average solid volume of one load. This is calculated for both sawlogs and pulpwood. In the present case the average solid volume of one load is 12 m3 for sawlogs and 8 m3 for pulpwood. nsawn-timber = npulpwood =

A ⋅ Vha ⋅ Vst 12

A ⋅ Vha ⋅ (1 − Vst ) 8

(5) (6)

Using Eqs. 4, 5 and 6, the total driving distance on the site can be calculated for both unloaded and loaded drives. The total distance driven under different slope conditions can be derived by simulation, and fuel consumption per metre can be modelled based on field data. This information is enough for the fuel consumption simulations, after which the results can be converted to monetary values. This enables comparisons to be made between the fuel costs and removal and installation costs of the ground contact devices, which in turn consist of the capital and labour costs of these operations.

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3.6 Handling of the GPS and CAN bus results – Obrada GPS i CAN bus podataka The GPS receiver was placed on the top of the tractor’s cabin, but as the tractor’s centre of gravity is located about 3 metres further back (depending slightly on the load size and the length of the logs), the GPS data should be shifted to match the trajectory of the tractor’s centre of gravity (Suvinen and Saarilahti 2006).

Since the measuring frequency is four times per second for the CAN data logger and once per second for the GPS receiver, every four consecutive CAN bus observations are averaged in order to synchronize these measurements.

Although Suvinen and Saarilahti (2006) reported that acceleration and deceleration cause some inaccuracy in the measuring system, these phases are ignored here as no reliable data are available on them.

For accurate analysis of the performance of various ground contact devices, momentary total resistance data are needed. This total resistance can be divided into components, which enables monitoring of the interaction between the soil and the ground contact devices.

The GPS receiver gives the horizontal velocity (v) of the forwarder, and the CAN bus system gives the gross power of the tractor’s drive line (P). The total resistance to the motion of the tractor can be derived by dividing the gross power of the drive line by the horizontal velocity of the tractor: FT =

P v

(7)

The total resistance of a forwarder can normally be divided into seven components: FT = FR +FS + FO + FW + FL + FI + a ⋅ m

(8)

It should be noted that the gross power of the drive line also includes some internal friction, which should be subtracted from the total resistance force before it is divided into its components.

The angular velocity of a wheel (w) is calculated from the CAN bus data referring to the tractor’s drive line. Based on the horizontal velocity of the forwarder (v), the angular velocity of the wheel (w) and the rolling radius of the wheel, the slip or travel reduction (i) can be calculated. This indicates the extent to which the speed of the tyres differs from the speed of the vehicle, and can be calculated using the equation (ISTVS 1977): i=

88

v − rR ⋅ w v

(9)

For a braked tyre the slip indicator is named skid (S) and can be calculated using the equation (ISTVS 1977): S=

rR ⋅ w − v rR ⋅ w

(10)

On steep downhill slopes, when the wheels are in skid mode, the tractor adjusts its power transmission to keep the velocity suitable, which often means that the direction of hydraulic transmission is opposed. This can be seen in the CAN bus data in the form of negative values for the gross power on the tractor’s drive line. In that case unfortunately, the fuel feed for the test tractor falls to zero and decreases reliabilty of consumption model at wheel skid. It is on account of this that the percentage differences in gross power on the drive line are not equal to the fuel consumption.

The components of the total resistance to the forwarder’s movement are described in Eq. 8. As the present analysis does not include acceleration or deceleration parts, the inertia resistance can be omitted, as can the snow resistance, as all the tests were carried out under summer conditions. The data were not suitable for analysing the winding resistance, because the trajectory that included only a few turns and effects of the turning radius on the winding resistance could not be analysed. Thus the effects of winding resistance are considered to belong to the background noise. Eq. 8 can be reduced to the following form: FT = FR + FS + FO + FI

(11)

The main factors which cause these four resistance forces are the micro- and macrotopographies of the terrain, soil type and conditions, performance of the tractor and its equipment, and the driver’s decisions. The terrain conditions were easy during the whole test route, and the test was carried out so that the driver’s decisions (e.g. microrouting, acceleration and deceleration) were limited as far as possible. Thus the variation between the total resistance forces can be considered to be a consequence of the modifications made to the forwarder’s equipment.

Modification of the forwarder’s ground contact device brings about changes in factors such as: Þ slip between the ground contact devices and terrain Þ transformation of the soil and ground contact devices Þ contact area between the terrain and ground contact devices Þ internal slip in ground contact devices Croatian Journal of Forest Engineering 27(2006)2

Economic Comparison of the Use of Tyres, Wheel Chains and Bogie Tracks ... (81–102)

Þ internal friction in ground contact devices Þ forwarder’s overall mass Þ forwarder’s kinetic energy Þ forwarder’s turning and steerability characteristics.

Changes in the above variables can be seen in variations in the total resistance to tractor’s movement.

4. Results – Rezultati 4.1 Total resistance, motion resistance coefficient, slip and skid – Ukupni otpor, koeficijent otpora kretanja, klizanje The test trajectory consisted of three parts, as presented in Figure 4, and the total resistance in each

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section when driving with an unloaded tractor is shown in Table 1. It can be seen that tyres alone were better than tyres with wheel chains in every section, and that the latter were better than tyres with bogie tracks and wheel chains. The resistance force on the downward slope was as much as about 50% greater with wheel chains and bogie tracks than without them. It should be noted, however, that the absolute values for the total resistance were quite small on the downward slope, so that even small changes will affect the result substantially in percentage terms.

The total resistance forces for a loaded tractor are shown in Table 2. The results are quite similar to those with an unloaded tractor, the only significant differences being that the total resistance with bogie tracks on even terrain was 4% lower and that with wheel chains 19% lower.

Table 1 Total resistances in three sections of the test lane with an unloaded tractor Tablica 1. Ukupni otpori na tri sekcije ispitne izvozne vlake pri kretanju neoptere}enoga forvardera Unloaded forwarder Neoptere}eni forvarder Velocity – Brzina m/s Mass – Masa t Slope Nagib Uphill – Uzbrdo Even terrain – Ravan teren Downhill – Nizbrdo Total – Ukupno

Tyres – Gume 1.15 16.2

Section length Duljina sekcije

Sum of total resistance Ukupni otpor

m 65 85 115 265

kN 4008 2230 850 7061

Chains – Lanci 1.08 17.0 Difference relative Sum of total to tyres resistance Razlika u odnosu Ukupni otpor na gume kN % 4373 9 2281 4 1242 46 7896 12

Tracks and Chains Polugusjenice i lanci 1.01 18.5 Difference relative Sum of total to tyres resistance Razlika u odnosu Ukupni otpor na gume kN 5109 2538 1280 8927

% 27 15 50 26

Table 2 Total resistances in three sections of the test lane with a loaded tractor Tablica 2. Ukupni otpori na tri sekcije ispitne izvozne vlake pri kretanju optere}enoga forvardera Loaded forwarder Optere}eni forvarder Velocity – Brzina m/s Mass – Masa t Slope Nagib Uphill – Uzbrdo Even terrain – Ravan teren Downhill – Nizbrdo Total – Ukupno

Tyres – Gume 0.85 20.9

Section length Duljina sekcije

Sum of total resistance Ukupni otpor

m 65 85 115 265

kN 6458 3427 1020 10905

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Chains – Lanci 0.99 21.7 Difference relative Sum of total to tyres resistance Razlika u odnosu Ukupni otpor na gume kN % 7093 10 2763 –19 1514 48 11370 4

Tracks and Chains Polugusjenice i lanci 0.85 23.2 Difference relative Sum of total to tyres resistance Razlika u odnosu Ukupni otpor na gume kN 8126 3286 1493 12905

% 26 –4 46 18

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Table 3 Motion resistance coefficients in three sections of the test lane with an unloaded tractor Tablica 3. Koeficijenti otpora kretanja na tri sekcije ispitne izvozne vlake pri kretanju neoptere}enoga forvardera Unloaded forwarder Neoptere}eni forvarder Velocity – Brzina m/s Mass – Masa t Slope Nagib Uphill – Uzbrdo Even terrain – Ravan teren Downhill – Nizbrdo Total – Ukupno

Section length Duljina sekcije m 65 85 115 265

Tyres – Gume

Chains – Lanci

1.15 16.2 Motion resistance coefficient Koeficijent otpora kretanja – 0.39 0.17 0.05 0.17

1.08 17.0 Motion resistance Difference relative coefficient to tyres Koeficijent otpora Razlika u odnosu kretanja na gume – % 0.40 4 0.16 –1 0.06 39 0.18 6

The increase in the mass of the unloaded tractor when using wheel chains was 5% and that when using bogie tracks and wheel chains was 14%, but the difference in total resistance relative to the use of tyres alone was in most cases greater than that, as can be seen in Tables 1 and 2. The motion resistance coefficients for an unloaded tractor, obtained by dividing the total resistance by the weight of the tractor and the driving distance, are shown in Table 3, where it can be seen that the motion resistance is almost the same on even terrain regardless of the ground contact device. Thus it is the increased mass that explains a higher total resistance. The motion resistance was even slightly smaller when using wheel chains and bogie tracks. On the uphill slope the total resistance increased by 4% when using wheel chains and by 12% when using bogie tracks and wheel chains, but on the downhill slope the increment was about one third of this in both cases. The general effect of the downhill slope section on the overall traction results was small, although it is clear that the increased mass does not explain the whole of the rise in total resistance on the downhill and uphill slopes.

The increase in the mass of the loaded tractor when using wheel chains was 4% and when using bogie tracks it was 11%. The results for the unloaded and loaded tractor on the uphill and downhill slopes were quite similar, and the same conclusion can be reached – that the increment in mass explains only about a half of the increase in total resistance. On even terrain, however, the total resistance was lower when using wheel chains and bogie tracks, and as can be seen in Table 4, the difference was even greater in terms of motion resistance coefficients.

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Tracks and Chains Polugusjenice i lanci 1.01 18.5 Motion resistance Difference relative coefficient to tyres Koeficijent otpora Razlika u odnosu kretanja na gume – % 0.43 12 0.16 –1 0.06 32 0.19 11

The slip percentages on a different section of the test lane and with different ground contact devices are presented in Table 5. When the mass of the tractor (with all its ground contact devices) and the slip are taken into account, the total resistance coefficients on the uphill slope and on even terrain are almost the same. The difference between the results is less than 6%, i.e. less than the measurement error of the system as reported by Suvinen and Saarilahti (2006).

Slip percentages and rolling resistance coefficients for the loaded tractor, with the slip effects deducted, are shown in Table 6. The results are very similar to those in Table 5 for an unloaded tractor, the only notable differences being that wheel chains and bogie tracks reduced the motion resistance coefficient on on even terrain and that the difference was so significant when using wheel chains that it did not fit within the limits of the measurement error. Probably as a result of a greater slip and increased mass relative to the unloaded tractor, the tyres penetrated deeper into the soil, and thus the rolling resistance increased. At the same time the bearing capacity of the soil was slightly lower on even terrain than on slope sections (see Figure 3).

It should be noted that the slip was very much smaller on the uphill slope section when using tyres rather than wheel chains and bogie tracks, with both a loaded and unloaded tractor. It is likely that the slip in that case consisted mostly of slip between the tyre and the wheel chain or bogie-track, which increases as the power on the drive line becomes greater, but unfortunately these data do not allow to distinguish the slip between the ground contact device and the terrain from the internal slip in the ground Croatian Journal of Forest Engineering 27(2006)2

Economic Comparison of the Use of Tyres, Wheel Chains and Bogie Tracks ... (81–102)

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Table 4 Motion resistance coefficients in three sections of the test lane with a loaded tractor Tablica 4. Koeficijenti otpora kretanja na tri sekcije ispitne izvozne vlake pri kretanju optere}enog forvardera Loaded forwarder Optere}eni forvarder Velocity – Brzina m/s Mass – Masa t Slope Nagib

Uphill – Uzbrdo Even terrain – Ravan teren Downhill – Nizbrdo Total – Ukupno

Section length Duljina sekcije m 65 85 115 265

Tyres – Gume

Chains – Lanci

0.85 20.9 Motion resistance coefficient Koeficijent otpora kretanja – 0.48 0.20 0.04 0.20

0.99 21.7 Motion resistance Difference relative coefficient to tyres Koeficijent otpora Razlika u odnosu kretanja na gume – % 0.51 6 0.15 –22 0.06 43 0.20 0

Tracks and Chains Polugusjenice i lanci 0.85 23.2 Motion resistance Difference relative coefficient to tyres Koeficijent otpora Razlika u odnosu kretanja na gume – % 0.55 13 0.17 –14 0.06 32 0.21 7

Table 5 Slip and motion resistance coefficients exclusive of travel reduction and slip on three sections of the test lane with an unloaded tractor Tablica 5. Postotak klizanja i koeficijent otpora kretanja umanjen za otpor klizanja na tri sekcije ispitne izvozne vlake pri kretanju neoptere}enoga forvardera Unloaded forwarder Neoptere}eni forvarder Velocity – Brzina m/s Mass – Masa t

Slope Nagib

Uphill – Uzbrdo Even terrain – Ravan teren Downhill – Nizbrdo Total – Ukupno

Tyres – Gume

Chains – Lanci

1.15 16.2

1.08 17.0 Motion resistance coefficient Koeficijent otpora kretanja – 0.366 0.157 0.066 0.174

Section length Duljina sekcije

Slip Klizanje

m 65 85 115 265

% 5.2 7.4 0.7 3.9

Motion resistance coefficient Koeficijent otpora kretanja – 0.367 0.151 0.046 0.161

Slip Klizanje

% 9.2 2.4 –1.4 2.4

contact device. The bearing capacity of the soil was slightly lower on on even terrain than on the uphill slope section, and that is probably the reason why the slip was about three times greater without wheel chains and bogie tracks.

The increment in the total resistance coefficient when using wheel chains or bogie tracks on the downward slope was greater than could be explained by the growth mass and slip. The steerability and turning characteristics of the vehicle are probably better with skid tyres than with skid tyres fitted with wheel chains and bogie tracks, and inflexibility in steering naturally means an increased resistance force.

More rigid ground contact devices (i.e. tyres with Croatian Journal of Forest Engineering 27(2006)2

Difference relative to tyres Razlika u odnosu na gume % 0 4 42 8

Slip Klizanje

% 10.1 2.6 –2.3 2.3

Tracks and Chains Polugusjenice i lanci 1.01 18.5 Motion Difference resistance relative to coefficient tyres Koeficijent Razlika u otpora odnosu na kretanja gume – % 0.389 6 0.160 6 0.063 29 0.181 13

wheel chains and bogie tracks) also penetrate deeper into the soil during deceleration, which increases the rolling resistance. These data cannot exhaustively explain why the motion resistance coefficient was so high on the downward slope when using wheel chains and bogie tracks as compared with tyres, but it should be remembered that the absolute value for the total resistance on the downward slope is relatively small, so that it is of relatively minor significance for the total model. Also, the low absolute values mean that even small measurement errors can cause a notable error in comparisons expressed in percentage terms.

The slip is not constant, but increases as the power increases (e.g. on uphill slopes) and asymptotically

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Table 6 Slip percentages and motion resistance coefficients exclusive of travel reduction and slip in three sections of the test lane with a loaded tractor Tablica 6. Postotak klizanja i koeficijent otpora kretanja umanjen za otpor klizanja na tri sekcije ispitne izvozne vlake pri kretanju optere}enoga forvardera Loaded forwarder Optere}eni forvarder Velocity – Brzina m/s Mass – Masa t

Slope Nagib

Uphill – Uzbrdo Even terrain – Ravan teren Downhill – Nizbrdo Total – Ukupno

Tyres – Gume

Chains – Lanci

0.85 20.9

0.99 21.7 Motion resistance coefficient Koeficijent otpora kretanja – 0.457 0.148 0.063 0.197

Section length Duljina sekcije

Slip Klizanje

m 65 85 115 265

% 6.3 6.8 –2.1 2.8

Motion resistance coefficient Koeficijent otpora kretanja – 0.454 0.183 0.044 0.195

Slip Klizanje

% 10.8 2.8 –2.7 2.4

Difference relative to tyres Razlika u odnosu na gume % 1 –19 44 1

Tracks and Chains Polugusjenice i lanci 0.85 23.2 Motion Difference resistance relative to Slip coefficient tyres Klizanje Koeficijent Razlika u otpora odnosu na kretanja gume % – % 9.9 0.495 9 2.2 0.166 –9 –2.1 0.058 32 2.2 0.209 7

approaches a limit value that depended on the soil conditions as well as the performance of the tractor and its equipment. On the other hand, the slip does

not increase in a linear fashion depending on the gradient of the slope, but rather the increment is greater on steeper gradients. The same pattern is

Fig. 6 Slip percentages for an unloaded forwarder as a function of the percentage gradient Slika 6. Postotak klizanja neoptere}enoga forvardera u ovisnosti o nagibu terena

Fig. 7 Slip percentages for a loaded forwarder as a function of the percentage gradient Slika 7. Postotak klizanja optere}enoga forvardera u ovisnosti o nagibu terena

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Fig. 8 Fuel consumption for an unloaded forwarder as a function of gradient Slika 8. Jedini~na potro{nja goriva neoptere}enoga forvardera u ovisnosti o nagibu terena

Fig. 9 Fuel consumption for a loaded forwarder as a function of gradient Slika 9. Jedini~na potro{nja goriva optere}enoga forvardera u ovisnosti o nagibu terena

recognized for negative slip or skid on the downward slope. On the other hand, slip does not give way to skid until the gradient is steep enough to compensate for the traction. Thus the relationship between gradient and slip or skid can be described best by means of a third-degree polynomial function.

Third-degree functions are fitted to the slip measurements in Figures 6 and 7, where it can be seen that the slip on even terrain was low when using wheel chains and bogie tracks but the difference evened out on the uphill slope, although admittedly the coefficients of determination for tyres are lower. The performance of wheel chains on the loaded tractor become progressively worse as the slope became steeper.

When using wheel chains on an unloaded tractor the slip turns to skid almost immediately as the gradient becomes negative, whereas the turning point for a loaded tractor with wheel chains is at a gradient of about –10%. When using bogie tracks the turning point is at about –10% for both an unloaded and loaded tractor. With tyres alone the slip turns to skid only at a gradient of about –15%, and this turning point is almost the same for a loaded and unloaded tractor. This is probably one of the reasons why the

total resistance is much higher for bogie tracks, and especially for wheel chains, than it is for tyres alone on a downward slope – since skid may affect the resistance to the tractor’s movement more than does a minor amount of slip.

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4.2 Fuel cost analysis – Analiza tro{kova goriva 4.2.1 Consumption models – Modeli potro{nje goriva An interval of 10 metres distance was used to define the terrain profile, and as the power sums and times for these 10-metre intervals were known and specific fuel consumption was set at 240 g/kWh (see section 3.5), the fuel consumption per metre could be modelled based on the gradient data. The fuel consumption figures per metre for the unloaded and loaded tractor based on measured wattages for different slope conditions, together with linear models based on these measurements, are presented in Figures 8 and 9. The coefficients of determination attached to these figures are very high. For an unloaded tractor the fuel consumption is almost the same for tyres with wheel chains as for tyres alone, but it is about 6–7% higher for tracked tyres on an uphill slope. In the case of a loaded tractor the differences are clearer,

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tracked tyres in particular being substantially worse, with a difference of about 40–60% relative to tyres alone on uphill slopes. On downhill slopes the difference is still greater in percentage terms, but as the absolute fuel consumption is less, this is not so critical as far as total fuel consumption is concerned.

The linear models presented in Figures 8 and 9 can be used to calculate the fuel consumption for four types of terrain introduced in Chapter 3.5. (A, B1, B2, B3), the other variables in the sensitivity analyses being the size of the site (A, ha), average volume of growing stock on the site (Vha, m3 ha–1), the percentage of sawlogs (Vst, %), which depends

on the average volume of growing stock and the average extraction distance (daverage, m).

4.4.2 Consumption when using tyres – Potro{nja goriva pri primjeni guma The total fuel consumption per hectare when using tyres is presented separately in Figure 10 for four terrain types as a function of extraction distance and average volume of the growing stock (in this simulation the percentage of sawlogs is taken to vary between 50% and 80% depending on the volume of the growing stock). Here the figure is seen to be about 10% higher on terrain type B3, about 20% higher on

Fig. 10 Simulated fuel consumption for a forwarder with tyres as a function of extraction distance and total volume of the growing stock in four types of terrain Slika 10. Modelirana potro{nja goriva forvardera bez lanaca i polugusjenica u ovisnosti o udaljenosti izvo`enja i drvnoj zalihi na ~etiri vrste terena 94

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type B1 and 30% higher on type B2 than on terrain type A. Steep terrain, and especially driving on uphill slopes when loaded, will naturally increase fuel consumption substantially.

4.2.3 Fuel consumption using wheel chains and/or bogie-tracks in relation to tyres alone – Potro{nja goriva pri primjeni lanaca i/ili polugusjenica u odnosu na primjenu guma The differences in total fuel consumption relative to tyres when using wheel chains or bogie tracks and wheel chains are presented in Figures 11 and 12. It

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can be seen that these combinations increase fuel costs in all simulated terrain types, the extra costs being about four times greater when using bogie tracks and chains than with chains alone.

The increase in costs is greater when driving on even terrain (A) than on steep terrain (B1), because as it was previously mentioned, fuel consumption measurement is false on steep downward slopes when it falls to zero. The absolute value for the total resistance on the downward slope is relatively small and has relatively minor significance for the total model. On the other hand, loaded driving on uphill

Fig. 11 Differences in simulated fuel consumption when using wheel chains relative to tyres alone in four types of terrain Slika 11. Razlike u modeliranoj potro{nji goriva forvardera s lancima u odnosu na primjenu guma na ~etiri vrste terena Croatian Journal of Forest Engineering 27(2006)2

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Fig. 14 Break-even points for the profitability of removal and re-installation of bogie tracks and chains as a function of average extraction distance and total volume of the growing stock Slika 14. Povr{inska prekretnica isplativosti skidanja i postavljanja polugusjenica u ovisnosti o srednjoj udaljenosti izvo`enja i drvnoj zalihi

per hectare, are presented in Figures 13 and 14. As can be seen in Figure 13, these break-even points are relative high for the removal of wheel chains. For terrain type B3 the break-even point for a growing stock of 450 m3/ha and an extraction distance of 1000 metres is as much as 90 hectares, so that the values do not even fit on the same scale and have had to be left out of Figure 13.

The abandonment of bogie tracks (Figure 14) becomes profitable at much smaller site sizes than

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the abandonment of wheel chains. On terrain type B2, for example, the five-hectare break-even point is reached at an extraction distance of less than 500 metres if the average volume of growing stock is more than 350 m3/ha. On the other hand, the breakeven values for terrain type B3 are relatively high in every alternative. On even terrain the five-hectares break-even point is reached at extraction distances between 500 and 1000 metres depending on the volume of the growing stock.

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As any percentage changes in the fuel price devolve directly on total fuel costs, it is easy to calculate the impacts of fuel price on these break-even points. If the fuel price increases by 15%, for example, the original break-even point will be 15% higher than that calculated using the new, higher fuel price.

5. Discussion – Rasprava The hypothesis examined here was that wheel chains and bogie tracks increase the fuel consumption of a forwarder on soils with a high bearing capacity. Models based on the field tests described in this paper prove that the hypothesis is true. The extra fuel consumption was fairly marginal in the case of wheel chains, but the economic effects of using bogie tracks were considerable.

On even terrain the measured fuel consumption was around 2 grams per metre for an unloaded tractor regardless of its ground contact devices, while for a loaded tractor it was just over 2 grams per metre with tyres and wheel chains and almost 4 grams per metre with bogie tracks. Nordfjell et al.

(2003) reported that forwarders consumed 0.23–0.38 litre per 100 metres of driving and that the difference between an unloaded and loaded vehicle was only 10%. They carried out their measurements without bogie tracks, however. The present results support their findings, although the difference in fuel consumption between an unloaded and loaded tractor is clearly greater when using bogie tracks.

The most important factors behind the rise in fuel consumption when using wheel chains and bogie tracks seem to be: Þ increased tractor mass Þ slip on uphill slopes.

The data obtained here did not enable us to analyse whether the latter was a matter of slip between the soil and the ground contact devices or internal slip within the ground contact devices. A significant result, however, was that the slip turns to skid on a much more gentle downhill slope when using wheel chains or bogie tracks than with just tyres. This was probably the reason why the extra total resistance and fuel consumption were so high when using wheel chains or bogie tracks on downward slopes.

The conclusion to be reached here is that the removal and reinstallation of wheel chains is not an economic proposition under normal logging conditions, although the removal of bogie tracks may become profitable on relatively small sites if: Þ the bearing capacity of the soil is high throughout Þ the total volume of the timber to be harvested is high Croatian Journal of Forest Engineering 27(2006)2

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Þ the extraction distance is long.

If the forwarder is loaded when driving uphill the removal of bogie tracks becomes even more profitable. In any case, the removal of bogie tracks does not allow a single operator to achieve any huge cost savings and savings are in general restricted to certain soil types, but it should be remembered that even small cost reductions in logging operations can amount to significant savings at the national level.

Rieppo and Örn (2003) have estimated, for example, that a reduction of 5% in the fuel consumption of forest tractors and timber extraction vehicles in Finland would yield annual savings of five million euros. Reduced fuel consumption also means more sustainable wood harvesting.

The present data were collected on soils with a high bearing capacity and within a relatively small area, so that the work has its limitations. The finding that the removal of bogie tracks is profitable cannot be extrapolated to soils of low bearing capacity, as bogie tracks are still necessary on soft terrain and under winter conditions. Further research will be needed to define exactly what the limit values for the break-even points are. The limit value for the cone index at which removal is profitable, for example, cannot be specified exactly on the basis of the present results. This study nevertheless provides clear evidence that the use of bogie tracks is not always justified. It has also been shown that it is not only the selection of a suitable forest tractor but also the selection of suitable ground contact devices on certain logging sites that is needed in order to achieve economies in wood harvesting.

A larger data bank on the effects of ground contact devices on fuel consumption would enable this information to be combined with digital maps, which would then allow logging operators to choose suitable ground contact devices. An off-road routing method which supports this kind of approach has been presented by Suvinen (2006), for example.

The measuring method presented here is suitable for other terramechanical research, except measuring of fuel consumption at wheel skid. A comparison of tyre types, for example, is easy to arrange, and can serve as a useful development tool for tyre, wheel chain and bogie track manufacturers. In addition, logging operators and timber procurement companies can use these results in their planning work, and can exploit them to find the best logging order for forest stands and to gather together forest stands with similar soil conditions to form a work site on which logging is possible with a single type of ground contact device.

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Nokian Tyres, (No year). <http://raskaatrenkaat.nokiantyres.com/> (Accessed 30 March 2005)

Acknowledgements – Zahvala The participants in this research project are the University of Helsinki, Jämsänkoski Forest Machine School, Nokian Tyres Plc and John Deere Forestry Ltd and its subsidiary Plustech Ltd. I would like to thank Dr. Martti Saarilahti for his comments on the study and manuscript.

6. References – Literatura Bygdén, G., Eliasson, L., Wästerlund, I., 2004: Rut depth, soil compaction and rolling resistance when using bogie tracks. Journal of Terramechanics 40(3): 179–190.

Favreau, J., Gingras, J. F., 1998: An analysis of harvesting costs in eastern Canada. Forest Engineering Research Institute of Canada, Special Report SR-129.

ISTVS, 1977: International Society for Terrain-Vehicle Systems Standards. Journal of Terramechanics 14(3): 153–182.

Johansson, A., 2001: Forestry Costs and Revenues 2000, A year of storms and floods. Forestry Research Institute of Sweden, Results nr. 4, Uppsala, Sweden.

Nordfjell, T., Athanassiadis, D., Talbot, B., 2003: Fuel Consumption in Forwarders. International Journal of Forest Engineering 14(2): 11–20.

Olofsfors, (No year). <http://www.olofsfors.se/default. asp?id=1155&ptid=3173> (Accessed 28 September 2006).

Rieppo, K., Örn, J., 2003: Metsäkoneiden polttoaineen kulutuksen mittaaminen (Measuring the fuel consumption of forest machines). Metsätehon raportti 148, 19.5.2003.

Esitutkimus (in Finnish).

Suvinen, A., Saarilahti, M., 2006: Measuring the Mobility Parameters of Forwarders using GPS and CAN Bus Techniques. Journal of Terramechanics 43(2): 237–252.

Suvinen, A., 2006: A GIS-based simulation model for terrain tractability. Journal of Terramechanics 43(4): 427–449.

Veal, M. W., Taylor, S. E., McDonald, T. P. McLemore, D. K., Dunn, M. R., 2001: Accuracy of Tracking Forest Machines with GPS. American Society of Agricultural Engineers 44(6): 1903–1911.

Murfitt, A., McMullen, W. B., Baker Jr, M., McPhail, J. F., 1975: Design and construction of roads in Muskeg in artic and subartic regions. Proceedings of the 16th Muskeg Research Conference, October 7, 1977, NRCC, ACGR TM 116, 152–185.

Väkevä, J., Kariniemi, A., Lindroos, J., Poikela, A., Rajamäki, J., Uusi-Pantti, K., 2001: Puutavaran metsäkuljetuksen ajanmenekki (Time consumption of timber haulage). Metsätehon raportti 123, 7.9.2001, Korjattu versio 7.10.2003 (in Finnish).

Naesset, E., 1999: Point accuracy of combined pseudorange and carrier phase differential GPS under forest canopy. Canadian Journal of Forest Research 29: 547–553.

Wong, J. Y., Huang, W., 2006: »Wheels vs. tracks« – A fundamental evaluation from the traction perspective.

Journal of Terramechanics 43(1): 27–42.

Sa`etak

Usporedba ekonomi~nosti primjene guma, lanaca i polugusjenica pri izvo`enju drva forvarderom U Finskoj se pri izvo`enju drva forvarderima vrlo ~esto tijekom cijele godine, neovisno o uvjetima terena, koriste polugusjenice na bogi ovjesu. Osnovni razlog tomu su pove}ani tro{kovi rada zbog utro{ka vremena na skidanju i postavljanju polugusjenica. Prednosti se uporabe polugusjenica i lanaca isti~u pri radu na slabo nosivim tlima. Primjena polugusjenica ili lanaca smanjuje dodirni tlak vozila na tlo pove}avaju}i dodirnu povr{inu izme|u gume i tla, pri ~emu se izme|u rebara gume ne nakuplja blato.

Postavka se istra`ivanja odnosi na rad forvardera na ~vrstim tlima, pri ~emu primjena polugusjenica i lanaca jedino pove}ava otpore te time i potro{nju goriva. Pri tome bi skidanje lanaca ili polugusjenica s kota~a s ekonomskoga gledi{ta bilo isplativo, ako zanemarimo okoli{nu pogodnost (o{te}ivanje tla). U radu se analiziraju uvjeti ekonomske opravdanosti skidanja polugusjenica i lanaca s kota~a te njihov utjecaj na radne zna~ajke forvardera pri razli~itim terenskim uvjetima.

Istra`ivanje je provedeno na forvarderu Timberjack 1110 (slika 1) koji je bio opremljen na tri na~ina: Þ 1. gumama Nokian 710/45–26.5, pri ~emu je tlak zraka u gumama prednjega bogi ovjesa iznosio 350 kPa, a u stra`njima 440 kPa, Þ 2. lancima na kota~ima koji su pri istra`ivanju bili postavljeni na stra`nje kota~a oba bogi ovjesa. Ukupna masa para lanaca iznosi 400 kg, dok je njihova debljina 16 mm,

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Þ 3. polugusjenicama ECO-TRACK proizvo|a~a Olofsors, koje su bile postavljene samo na stra`njem bogi ovjesu uz lance na stra`njim kota~ima prednjega bogi ovjesa.

Mjerni sustav ~ini GPS ure|aj Trimble ProXR s antenom i CAN bus sustav za prikupljanje podataka koji omogu}uje mjerenje izlazne snage i broja okretaja motora pri radu. Nagibi su terena na izvoznoj vlaci forvardera odre|eni metodom niveliranja. Konusnim je penetrometrom izmjerena nosivost tla na 10 mjernih mjesta uzdu` izvozne vlake nakon prolaska forvardera. Radi odre|ivanja stanja nosivosti tla mjerenja su obavljena konusnim penetrometrom na neizga`enom tlu pored mjernih mjesta na izvoznoj vlaci. Tijekom istra`ivanja nije bilo oborina, temperatura se kretala oko 0 °C te je tlo bilo suho i ~vrsto.

Voza~ je tijekom izvo`enja odr`avao stalni broj okretaja motora u istom prijenosnom stupnju transmisije kako bi brzina kretanja forvardera bila vi{e ili manje stalna. Mjereno je pri vi{e prolazaka neoptere}enoga i optere}enoga forvardera s tri opreme voznoga sustava. U svakom se prolasku izvozio isti tovar smrekovih trupaca. Masa neoptere}enoga i optere}enoga forvardera bez polugusjenica i lanaca odre|ena je pomo}u kolne vage. Masa je polugusjenica i lanaca preuzeta iz podataka proizvo|a~a te pribrojena masi neoptere}enoga i optere}enoga forvardera ovisno o njihovoj primjeni tijekom istra`ivanja.

Ukupni su otpori definirani kao suma otpora kotrljanja, otpora uspona, otpora klizanja kota~a, otpora povr{inskih prepreka, snje`noga pokriva~a, otpora upravljanja i otpora inercije (izraz 8). Ukupni je otpor odre|en dijeljenjem izlazne snage motora i brzine kretanja forvardera izmjerene GPS ure|ajem (izraz 7). Istra`ivanje je provedeno pri vo`nji forvardera stalnom brzinom kretanja u ljetnom razdoblju te su stoga iz ukupnih otpora izba~ene veli~ine otpora snje`noga pokriva~a, otpora inercije i otpora upravljanja (izraz 11).

Izvozna vlaka forvardera podijeljena je u tri dijela (uzbrdo, ravan teren i nizbrdo) te su ukupni otpori za svaki dio puta neoptere}enoga i optere}enoga forvardera prikazani u tablicama 1 i 2. Vidljivo je da su ukupni otpori najmanji pri vo`nji neoptere}enoga forvardera bez lanaca ili polugusjenica u svim dijelovima. Kod optere}enoga forvardera jedino je na ravnom terenu manji otpor pri primjeni polugusjenica i lanaca.

Koeficijent je otpora kretanja odre|en dijeljenjem ukupnoga otpora s te`inom forvardera i udaljenosti izvo`enja. Za prazni forvarder koeficijent je otpora kretanja pri kretanju uz nagib ve}i za 4 % kod primjene lanaca odnosno za 12 % kod primjene polugusjenica u odnosu na primjenu guma. Pri kretanju niz nagib koeficijenti su mnogo ve}i pri primjeni lanaca ili polugusjenica (tablica 3). Osnovni razlog le`i u znatnom pove}anju mase forvardera primjenom lanaca ili polugusjenica. Pri primjeni lanaca i polugusjenica kod optere}enoga forvardera ve}i su koeficijenti na nagnutnom terenu te manji na ravnom terenu, pri ~emu su razlike zna~ajnije nego pri usporedbi ukupnih otpora (tablica 4).

Mjerenjem brzine okretaja motora ustanovljena je kutna brzina kota~a, tj. mno`enjem s dinami~kim polumjerom kota~a, i obodna brzina kota~a. Usporedbom obodne brzine kota~a i brzine kretanja forvardera odre|en je postotak klizanja (izrazi 9 i 10).

Postoci klizanja kota~a neoptere}enoga i optere}enoga forvardera prikazani su u tablicama 5 i 6. Klizanje je kota~a neznatno manje pri kretanju uz nagib bez primjene lanaca ili polugusjenica i kod neoptere}enoga i kod optere}enoga forvardera. Pri tome se klizanje najvi{e odnosi na unutra{nje klizanje izme|u lanaca ili polugusjenica i gume kota~a. Ve}e vrijednosti ukupnoga otpora pri primjeni lanaca i polugusjenica pri kretanju niz nagib ne mogu se samo objasniti ve}om masom i klizanjem kota~a, ve} lanci i polugusjenice dublje prodiru u tlo, {to pove}ava otpor kotrljanja. Nosivost tla na ravnom terenu bila je manja nego na nagnutnom terenu, {to je razlog ve}ega klizanja kota~a bez primjene lanaca i polugusjenica.

Izjedna~ene vrijednosti (slika 6 i 7) pokazuju da je klizanje kota~a na ravnom terenu malo pri primjeni lanaca i polugusjenica. Optere}eni forvarder s lancima na kota~ima ima znatno pove}anje klizanja s rastom nagiba terena.

Pri primjeni polugusjenica negativno klizanje kota~a neoptere}enoga i optere}enoga forvardera po~inje pri nagibu terena od –10 %, a bez lanaca i polugusjenica negativno klizanje kota~a po~inje pri nagibu terena –15 %.

Na osnovi mjernih podataka odre|en je model potro{nje goriva, pri ~emu je kori{tena specifi~na potro{nja goriva od 240 g/kWh. Izvozni je pravac s obzirom na nagib terena podijeljen u 2 razreda: teren s blagim nagibom A (–5 % do 5 %) i teren B s nagibom ve}im od 25 % uzbrdo i nizbrdo. Na terenu B su razmatrana 3 na~ina vo`nje forvardera s obzirom na smjer kretanja: natovareni se forvarder kre}e podjednako uz nagib i niz nagib (B1), natovareni se forvarder kre}e uz nagib (B2), natovareni se forvarder kre}e niz nagib (B3). Ostale varijable kori{tene u modelu su povr{ina {umske sastojine, drvna zaliha, obujam izra|enoga drva uzdu` traktorskoga puta, udaljenost izvo`enja drva te postotni udio tehni~ke oblovine u sortimentnoj strukturi. Udaljenosti su vo`nje forvardera izra~unate prema izrazima 1, 2 i 3.

Potro{nja goriva po prije|enom metru prikazana je na slikama 8 i 9. Za prazan forvarder potro{nja je pribli`no jednaka potro{nji forvardera s lancima i bez lanaca, dok je s polugusjenicama potro{nja za 6 do 7 % ve}a pri kretanju uz nagib. Kod optere}enoga forvardera potro{nja je goriva za 40 do 60 % ve}a pri primjeni polugusjenica u odnosu prema primjeni guma pri kretanju uz nagib.

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Preliminary note

Comminution of logging residues with a tub grinder: Calculation of productivity and procurement cost of wood chips Takuyuki Yoshioka, Rin Sakurai, Kazuhiro Aruga, Toshio Nitami, Hideo Sakai, Hiroshi Kobayashi Abstract â&#x20AC;&#x201C; Nacrtak An experiment on comminution of logging residues with a tub grinder was carried out in order to calculate the productivity and procurement cost of wood chips. At the investigated site, the tub grinder had a hammer mill crusher at the bottom of the tub, and a grapple loader and a bucket loader worked as auxiliary machines for the grinder. As a result, the productivity of the tub grinder was 60.0 loose m3/PMH0, and the total comminuting cost was calculated as 5.637 US$/m3, indicating that the comminuting cost of a large-sized crusher was lower than that of a small-sized chipper. The percentage of the cost of loaders, that of carrying in, installing, and carrying out the machines, and that of constructing a landing was 53% of the total comminuting cost. When a truck with the capacity of 40 m3 transported wood chips three times a day, the costs of comminution and transportation were 71.2 US$/t (DM1), which is almost on a par with those of European countries in which the energy utilization of logging residues is making steady progress. As a result of the discussion about the balance between the processing capacity of the tub grinder and that of other machines, it seemed reasonable for Japanese forestry to consider the use of one tub grinder at several logging sites.

Keywords: biomass, logging residues, tub grinder, productivity, cost of comminution and transportation

1. Introduction â&#x20AC;&#x201C; Uvod As one of the major woody biomass resources, logging residues, i.e., tree tops and branches which are generated during limbing and bucking, are expected to be a source of energy and an alternative to fossil fuels. The annual available amount of logging residues in Japan is currently estimated to be 3 million t/y on a dry-weight basis (Yoshioka et al. 2005), with a calorific value of 60 PJ (16.7 TWh). With respect to a harvest of logging residues, for instance, an experiment on hauling them with a forwarder was carried out by the authors of this paper (Yoshioka et al. 2000). In order to utilize logging residues for

1

energy, however, it is necessary to comminute them so that their forwarding and transporting efficiency can be enhanced. In addition, for pretreatment in an energy-conversion plant, residues should be chipped or crushed before being converted into usable energy, e.g., heat, electricity, liquid fuel.

Logging residues can be comminuted in a forest, at a landing of the roadside, or at an energy-conversion plant. Various kinds of chippers and crushers for logging residues have been developed and examined worldwide under field conditions (Asikainen and Pulkkinen 1998, Delgado and Giraldo 1995, Desrochers et al. 1993, Hall et al. 2001). In several countries, the technique has been already finalized, and

Dry matter (DM); refers to biomass that has been dried Suha tvar (ST); odnosi se na biomasu u suhom stanju

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operating manuals have been published (Alakangas et al. 1999, FAO 1976, Folkema 1989). On the other hand, chippers and crushers for comminuting logging residues and unmerchantable thinned trees have been diffused in recent Japanese forestry. The increasing nationwide interest in bioenergy utilization is one reason, and some small-sized and medium-sized chippers have been tested at the local government level in order to define the productivity of these machines and the quality of the chips obtained.

When a large-sized chipper or crusher is introduced, economies of scale will be achieved, i.e., the comminuting cost of a large-sized chipper or crusher is expected to be lower than that of a small-sized one. However, few trials on comminuting logging residues by a large-sized chipper or crusher with an engine output higher than ca. 150 kW have been carried out in Japan. The previous study by the authors of this paper, which discussed the appropriate site for comminuting logging residues from the viewpoint of the total procurement cost of wood chips, showed that the comminuting cost of a large-sized crusher was lower than that of a small-sized chipper (Yoshioka et al. 2002). As for comminution by the large-sized crusher, the study in which the performance of a tub grinder (TG400A, Vermeer Manufacturing Company, United States) was investigated at a grading site was referred to. Concerning the cost calculation of the tub grinder, however, only the labour cost, the machine cost (expenses for depreciation and supplies), and the fuel cost incurred by the operation of the tub grinder itself were considered in the study. On the other hand, Moriguchi et al. (2004), in a study about comminution by a medium-sized chipper with an engine output of 60.3 kW, showed that the cost of a grapple loader related to feeding logging residues into the chipper, cost of carrying in, installing, and carrying out the chipper and the loader, and that of constructing a landing for the operation accounted for a considerably high proportion of the total chipping cost (Moriguchi et al. 2004), suggesting that those additional costs should be considered, essentially, in the case of calculating the cost of comminuting logging residues with a large-sized crusher such as a tub grinder.

Therefore, the objective of this study was to investigate the following items by experimenting on comminution of logging residues with a tub grinder: Þ Productivity of a large-sized crusher; Þ Proportion of the cost of auxiliary machines, e.g., a grapple loader, that of carrying in, installing, and carrying out the crusher and auxiliary machines, and that of constructing a landing to the total cost;

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Þ Calculation of the cost of comminuting logging residues collected at a landing and transporting wood chips; Þ Balance of the processing capacity between the large-sized crusher and other machines, e.g., a yarding machine and auxiliary ones.

2. Materials and methods – Materijal i metode 2.1 Experimental site – Mjesto istra`ivanja The experiment was conducted at a site where pulpwood was extracted from scrap trees generated in the course of building a dam and residual material was comminuted by a tub grinder. In other words, the residual material was regarded as logging residues in this study. This was the building site of the Fukashiro Dam of Yamanashi Prefecture, which is to the west of Tokyo. The site is located at the upper reaches of the Kazuno River, which belongs to the system of the Sagami River. The scrap trees, which had to be disposed of properly according to local government regulations, were collected from an area of 18 ha of stands of Japanese cedar (Cryptomeria japonica D. Don) and broad-leaved trees, which were to be submerged.

2.2 System description – Opis sustava The Operation was divided into two systems, that is, a 'COLLECT and SORT' system and a 'COMMINUTE and TRANSPORT' one. After a certain amount of logging, residues were collected and comminuting operation was carried out.

In the 'COLLECT and SORT' system, felling was carried out with chain saws, extraction with a yarder (cable yarding system: endless Tyler system; maximum yarding distance: 460 m), bucking with chain saws, and sorting with a grapple loader. Pulpwood and logging residues were sorted, and a pile of pulpwood and a heap of residues were made. Logging residues, in this study, were considered as by-products of pulpwood production. In this sense, all the costs associated with this system are attributed to produced pulpwood. Time study of a yarder was carried out, and the balance of the processing capacity between this system and the 'COMMINUTE and TRANSPORT' one was discussed.

In the 'COMMINUTE and TRANSPORT' system, a grapple loader fed logging residues into a tub grinder, a tub grinder comminuted the logging residues (the screen size opening of a tub grinder was set at 5.0 cm), a bucket loader (a digging bucket of an excavator was replaced with a larger-sized bucket Croatian Journal of Forest Engineering 27(2006)2

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Fig. 1 Tub grinder Slika 1. Bubnjasti ivera~ for the purpose of loading wood chips) loaded wood chips onto a truck, and a truck transported the wood chips. Therefore, these two loaders were regarded as auxiliary machines for the tub grinder in this system.

The tub grinder was equipped with a conveyor to take wood chips directly into a truck. However, a bucket loader for loading chips was introduced because interest was focused on the truck mobility.

Time studies were conducted of the tub grinder and two loaders, and the volume of the processed chips and fuel (light oil) consumption of each machine was measured. A bin (0.60 meters long, 0.50 m wide, 0.60 m high, and 3.6 kg weight) was filled with chips, and the weight of the bin was also measured (scales: MODEL DS–261, Teraokaseiko Co., Ltd., Japan). Consequently, the green weight of the chips per unit volume could be calculated. In order to define the moisture content of the chips, ten chip samples were taken. The green mass of each sample was measured, and the samples were then dried at 103 degrees Celsius for more than 24 hours. The moisture content was determined by dividing the mass of water contained within the sample by the dry mass of the sample.

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2.3 Machine description – Opis strojeva The tub grinder (HD–9 Industrial Tub Grinder, DuraTech Industries International, Inc., United States, Figure 1) is 7.72 m long, 2.49 m wide, and 2.62 m high and weighs 8,760 kg. Its engine (275 HP John Deere) has an output of 205.1 kW. The tub is 1.02 m deep, and its diameter at the top and at the bottom is 2.91 m and 2.29 m, respectively. It has a hammer mill crusher at the bottom of the tub.

The grapple loader (base machine: EX120–5, Hitachi Construction Machinery Co., Ltd., Japan; grapple: GS90LHV, Iwafuji Industrial Co., Ltd., Japan, Figure 2) is 7.58 m long, 2.50 m wide, and 2.72 m high and weighs 11,800 kg. Its engine output is 67.1 kW. The bucket loader (312B, Shin Caterpillar Mitsubishi Ltd., Japan, Figure 3) is 7.57 m long, 2.89 m wide, and 2.83 m high and weighs 12,300 kg. Its bucket capacity and its engine output are 0.5 m3 and 66.9 kW, respectively. The maximum load volume of the truck was 40 m3. The operators of the machines shown above had a significant amount of relevant work experience, and the landing was large enough for the operators to maneuver the machines at will.

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Fig. 2 Grapple loader Slika 2. Utovariva~ s hvatalom

Fig. 3 Buchet loader Slika 3. Utovariva~ s korpom 106

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2.4 Cost calculation – Kalkulacija tro{ka The total comminuting cost per m3 of the processed wood chips, TC (US$/m3), is expressed as:  LA + M i + Fi CAi  CO + TC = ∑  i +  Pi W  W i 

(1)

where LAi (US$/PMH), Mi (US$/PMH), and Fi (US$/PMH) are the labour, machine, and fuel costs per PMH of each machine, respectively (i represents each machine, i.e., a tub grinder, a grapple loader, and a bucket loader); Pi (m3/PMH) is the productivity of each machine; CAi (US$) is the cost of carrying in, installing, and carrying out each machine; W (m3) is the whole amount of wood chips processed at the investigated site; CO (US$) is the cost of constructing a landing. The machine cost (expenses for depreciation and supplies), Mi, and the fuel cost, Fi, are calculated on the basis of the following two equations: Mi =

MPi × 0.9 H i × D i × LI i

+ Si

Fi = FCi × 0.76

(2) (3)

where MPi (US$), Hi (h/d), Di (d/y), and LIi (y) are the machine price, hours of operation a day, days of operation a year, and life of each machine, respectively; Si (US$/PMH) is the expense for supplies; FCi (dm3/h) is the fuel (light oil) consumption; 0.76 (US$/dm3) is the unit fuel price. Pi and FCi were calculated based on the results of the field experiment. LAi, CAi, W, CO, Hi, and Si were gathered by means of a questionnaire (the expense for supplies of a tub grinder, essentially, should have been investigated in detail, for instance, the frequency of replacing old worn-out hammers with new ones; concerning this, further discussion is required).

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60.0 m3/PMH0. On the other hand, the effective working time of the grapple loader and that of the bucket loader were 112.98 minutes and 118.78 minutes, respectively. Consequently, the performances were calculated to be 63.7 m3/PMH0 for the grapple loader and 60.6 m3/PMH0 for the bucket one. Details about the calculation of the total comminuting cost are listed in Table 1 (the exchange rate is roughly 105 yen to the U.S. dollar). The cost of constructing the landing per m3 of chips in Table 1, 0.732 US$/m3, was calculated by dividing the cost of constructing the landing, 2,857 US$, by the whole amount of wood chips processed at the investigated site, 3,903 m3.

However, 361.8 m3 of pulpwood was also produced at the site, so the cost of constructing the landing, essentially, should have been distributed between those of pulpwood and wood chips according to their economic values. In order to collect materials for the time study of the tub grinder and the two loaders, the yarder was in operation for 657.07 minutes, and the amount of the collected materials was equivalent to 40 m3 of pulpwood in addition to 120 loose m3 of wood chips.

The bin filled with the processed wood chips (Figure 4) weighed 61.4 kg at the experimental site.

The bin was 0.18 m3 volume and 3.6 kg weight, so the green weight of the chips per unit volume was calculated as 321 kg/m3. Finally, the average moisture content of chips was 120.4% (on a dry-mass basis, with a standard deviation of 12.6%), and the dry weight of chips per unit volume was estimated to be 146 kg/m3 (DM).

Although the moisture content of logging residues to be comminuted and the screen size opening of a tub grinder would influence the productivity of the tub grinder, only one instance (120.4% of mois-

3. Results – Rezultati The time study finished when the tub grinder had comminuted almost all of the logging residues collected at the landing and the truck had transported three full loads of wood chips. Therefore, every quantity processed by the tub grinder and the two loaders during the time study was considered to be 120 m3 in terms of the loose volume of chips (the volume of chips is expressed in loose measures in this study).

During the time study, the effective working time of the tub grinder was 119.93 minutes; thus, the productivity of the grinder was calculated as Croatian Journal of Forest Engineering 27(2006)2

Fig. 4 Processed wood chips Slika 4. Izra|ena drvna sje~ka 107

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Table 1 Details about the calculation of the total comminuting cost Tablica 1. Pojedinosti kalkulacije ukupnoga tro{ka usitnjavanja

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ture content and 5.0 cm of screen size opening) was examined in this study. Moreover, from the viewpoint of the quality of wood chips, the issue of whether the processed wood chips in this study shown in Figure 4 are suitable for energy or not must be discussed further.

4. Discussions – Rasprava 4.1. Total comminuting cost – Ukupni tro{ak usitnjavanja drva When only the labour cost, machine cost, and fuel cost of the tub grinder were considered on the basis of the previous study by the authors of this paper (Yoshioka et al. 2002), the comminuting cost per m3 of the processed wood chips was calculated as 2.663 US$/m3 (Table 1). This value corresponds to 18.2 US$/t (DM) (= 2.663 (US$/m3) × 1,000 (kg/t)/146 (kg/m3 DM); 1,000 kg/t is the conversion coefficient) in terms of the cost per dry mass of chips, showing a lower comminuting cost than that of the previous study, i.e., 22.7–45.5 US$/t (DM) (Yoshioka et al. 2002). The moisture content observed in this study, 120.4%, was quite similar than that in the previous study by the authors of this paper, 119.3% (Yoshioka et al. 2002), and typical of green logging residues (Asikainen and Pulkkinen 1998). On the other hand, the bulk density, 146 kgDM/m3 (DM), was higher than that in the previous study, 113.9 kg/m3 (DM) (Yoshioka et al. 2002). This is because the processed wood chips included coniferous and broad-leaved species, while the chips in the previous study included only Japanese cedar. In general, a broad-leaved tree is heavier than a coniferous one from the viewpoint of the weight per unit volume. Consequently, the higher bulk density is supposed to be one of the reasons why the comminuting cost in this study was lower than that of the previous study in terms of cost per dry mass of chips.

The cost of the two loaders, that of carrying in, installing, and carrying out the machines, and that of constructing the landing are also listed in Table 1 and the breakdown of total comminuting cost is shown in Figure 5. The percentage of the cost of loaders, that of carrying in, installing, and carrying out the machines, and that of constructing the landing is 53% of the total comminuting cost. These costs have to be reduced in order to improve the total comminuting cost. The cost of the two loaders makes up 30% of the total cost (Figure 5). Instead of the operational system examined in this study, however, other operation patterns such as different combination of machines could have been adopted at the experimental site. With respect to this, it is necessary Croatian Journal of Forest Engineering 27(2006)2

Fig. 5 Breakdown of the total comminuting cost Slika 5. Ra{~lamba ukupnoga tro{ka usitnjavanja to make a comparison between total cost of this study and the cost of the cases described below: Þ Case One: Instead of a grapple loader, the operator of a tub grinder manipulates a grapple by installing it in the tub grinder or introducing another chipper or crusher equipped with a grapple; Þ Case Two: Instead of a bucket loader, a tub grinder takes wood chips directly into a truck with its conveyor; Þ Case Three: Instead of two loaders (and a truck), a chipper truck, which can comminute logging residues and transport chips, is introduced. When only one machine works at the landing, there is no interaction between machines. Therefore, the operator of the chipper truck can control the entire 'COMMINUTE and TRANSPORT' system. Although the operation rates of both of the chipping and transporting functions of the chipper truck will be lower than those of a tub grinder and a truck, it is easier to plan and carry out the operation of one machine than those of two or three machines from the point of view of management.

The cost of carrying in, installing, and carrying out the machines (10%) and that of constructing the landing (13%) shown in Figure 5 are calculated by dividing their original cost by the whole amount of wood chips processed at the investigated site. In order to reduce these two costs, therefore, it is necessary to produce as many wood chips as possible at one landing, in other words, as many logging

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Fig. 6 Dependance of comminution and transportation costs per dry mass of chips vs. number of daily instances Slika 6. Ovisnost tro{kova usitnjavanja i prijevoza drvne sje~ke o broju dnevnih odredi{ta kamiona

residues as possible should be collected at one landing. For instance, when a 10% more amount of wood chips was produced at the landing, the percentage of the two costs to the total cost would decrease to 21.3% and the total cost would decrease by 2.1%.

Moreover, if 10,000 m3 of wood chips was produced, the percentage of the two costs would decrease to 11.2% and the total cost would decrease by 13.3%.

The total comminuting cost is calculated as 5.637 US$/m3 (Table 1). In a Finnish case study, the cost of comminution with a tub grinder was 1.7 US$/m3 although its productivity was similar to that of this study (Asikainen and Pulkkinen 1998).

The reason for this seems to be that there was only one machine in the Finnish system. The tub grinder was equipped with both a grapple and a conveyor.

The grapple put logging residues into the tub, and the conveyor took wood chips directly into a truck; in other words, the tub grinder required no auxiliary machines. On the other hand, the mobility of a truck for transportation was probably restricted. This study and the Finnish one should have been compared from the standpoint of the sum of costs of comminution and transportation. Incidentally, the total comminuting cost in this study, 5.637 US$/m3, corresponds to 38.6 US$/t (DM) in terms of the cost per dry mass of chips. The cost of a small-sized chipper, which would be suitable for tree tops and branches with a maximum diameter of 15 cm, was calculated as 66.5 US$/t (DM) in the previous study by the

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authors of this paper (Yoshioka et al. 2002). Therefore, the comminuting cost of a large-sized crusher is lower than that of a small-sized chipper.

From personal communication, the cost of a truck was shown to be 571 US$ per day at the investigated site. Figure 6 shows the relationship between the number of daily instances of truck transportation and the costs of comminution and transportation per dry mass of chips. The sums of the costs of comminution and transportation were 136.4 US$/t (DM), 87.5 US$/t (DM), and 71.2 US$/t (DM) when the truck transported wood chips once a day, twice a day, and three times a day, respectively (a truck will transport three times a day when its running speed, hours of operation a day, operation time of loading and unloading per cycle, and one-way running distance is 30 km/h, 6 h/d, 40 minutes per cycle, and 20 km, respectively). The cost of 71.2 US$/t (DM), for instance, corresponds to 3.56 US$/GJ or 12.8 US$/MWh in terms of the cost per calorific value of chips, and it is almost on a par with those of European countries in which the energy utilization of logging residues is making steady progress (Yoshioka et al. 2002). For the energy utilization of logging residues, Figure 6 may also be used in designing the arrangement of landings around an energy-conversion plant and the order of truck transportation, while the cost of a truck must be investigated and analyzed in detail.

4.2. Balance of the processing capacity between a tub grinder and other machines – Ravnote`a proizvodnih kapaciteta bubnjastoga ivera~a i ostalih strojeva The productivity of a tub grinder ranges from 14–24 to 100–150 m3/PMH in the existing studies (Asikainen and Pulkkinen 1998). The difference in the results is said to be due to difficulties in feeding logging residues into the tub grinder. The productivity of the tub grinder during the time study, 60.0 m3/PMH0, is quite similar to that of the Finnish case study, 60–70 m3/PMH (Asikainen and Pulkkinen 1998), showing high performance of the tub grinder investigated in this study.

In order to collect data for the experiment, the yarder was in operation for about 11 hours (657.07 minutes), while the tub grinder comminuted the sorted logging residues for almost 2 h (119.93 minutes). During the whole period (361.8 m3 of pulpwood and 3,903 m3 of wood chips were processed), the yarder and tub grinder operated for 105 days and 21 days, respectively. All operating hours of the yarder were not only used for wood chips because the yarder collected pulpwood material at the same time by whole-tree yarding. However, the yarder had to work for a much longer time than the tub grinder to Croatian Journal of Forest Engineering 27(2006)2

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cope with the relatively higher productivity of the grinder.

The percentages of idling time of the grapple loader and bucket loader were 6.2% and 4.6% of the total observed time, respectively. There was little time for both machines to idle, so it is supposed that the two loaders were running almost non-stop to cope with the high performance of the tub grinder.

From personal communication, the net productivity of the tub grinder during the whole period was 26.6 m3/PMH0, which is 44% of the productivity based on the time study, 60.0 m3/PMH0. It can be interpreted that the rate of operation of the tub grinder was below 50% even when the grinder worked at the site. This should be due to a relatively higher productivity of the tub grinder than that of the yarder. As a result, the rate of operation of the tub grinder will not be enhanced unless large amounts of logging residues are collected for comminution. Accordingly, a comparison of the costs of comminution and transportation between the two cases described below should be made and further discussion is required: Þ Case One: A large amount of logging residues is collected to counterbalance the high productivity of the tub grinder. The total comminuting cost will be reduced because a larger amount of wood chips will be produced at one landing and the cost of carrying in, installing, and carrying out the machines and that of constructing a landing will be reduced.

However, a landing that is large enough to operate the auxiliary machines for the tub grinder and accommodate large amounts of collected logging residues and processed wood chips must be constructed. Moreover, it would be necessary to build a network of high-grade forest roads on which large-sized trucks that can carry loads of as much as 40 m3 of wood chips can travel directly to the landing; Þ Case Two: Another smaller-sized tub grinder is introduced. In order to keep the rate of operation of the tub grinder high, the size of the grinder should be determined in accordance with the amount of logging residues that can be collected at one landing, the processing capacity of a yarding (or skidding) machine and auxiliary ones, and the degree of preparation of the network of high-grade forest roads.

In both cases presented above, the productivity of a tub grinder is expected to be still higher, so it would be reasonable for Japanese forestry to consider the use of one tub grinder at several logging sites. In this case, planning and management of an Croatian Journal of Forest Engineering 27(2006)2

operational system at each site considering the transfer of machines from one site to another will influence the total comminuting cost, since it has been clarified in this study that the proportion of the sum of the cost of carrying in, installing, and carrying out machines and that of constructing a landing in the total cost is not small.

5. Conclusions – Zaklju~ak In this study, an experiment on the comminution of logging residues with a tub grinder was carried out in order to calculate the productivity and procurement cost of wood chips, and the following conclusions have been drawn from the results and discussions: Þ The productivity of the tub grinder was 60.0 m3/PMH0, and the total comminuting cost was calculated as 5.637 US$/m3, indicating that the comminuting cost of a largesized crusher was lower than that of a small-sized chipper; Þ The percentage of the sum of the cost of a grapple loader and a bucket loader, that of carrying in, installing, and carrying out the machines, and that of constructing a landing was 53% of the total comminuting cost. Concerning the cost of the loaders, there seemed to be room for improvement, from the point of view of operational efficiency in comminution, in the combination of the tub grinder and loaders, so three alternatives were proposed (on the other hand, as many wood chips as possible should be produced at one landing in order to reduce the cost of carrying in, installing, and carrying out the machines and that of constructing the landing); Þ When a truck with a capacity of 40 m3 transported wood chips three times a day, the sum of the costs of comminution and transportation was 71.2 US$/t (DM), which is almost on a par with those of European countries in which the energy utilization of logging residues is making steady progress; Þ As a result of the discussion about the balance between the processing capacity of the tub grinder and that of other machines, it seemed to be reasonable for Japanese forestry to consider the use of one tub grinder at several logging sites.

Acknowledgement – Zahvala This study was supported in part by the National Fund for Forest Greenery and Waters from the National Land Afforestation Promotion Organization of

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Japan. The authors gratefully thank Mr. Kiichi Fukushima, the former Executive Director of the Forest Mechanization Society of Japan, for his great cooperation and valuable advice. A part of this study was orally presented at the International Seminar on Synergistic Approach to Appropriate Forestry Technology for Sustaining Rainforest Ecosystems (March 7 – 9, 2005, Bintulu, Sarawak, Malaysia).

6. References – Literatura Alakangas, E., Sauranen, T., Vesisenaho, T., 1999: Production techniques of logging residue chips in Finland: training manual. VTT Energy, Jyväskylä, 1–84.

Asikainen, A., Pulkkinen, P., 1998: Comminution of logging residues with Evolution 910R chipper, MOHA chipper truck, and Morbark 1200 tub grinder. Journal of Forest Engineering 9(1): 47–53.

Delgado, J. B., Giraldo, G. A., 1995: Energy possibilities from forest residues in the region of Castilla y León in Spain. Biomass and Bioenergy 8(1): 21–28.

Desrochers, L., Puttock, D., Ryans, M., 1993: The economics of chipping logging residues at roadside: a study of three systems. Biomass and Bioenergy 5(5): 401–411.

FAO, 1976: Wood chips: production, handling, transport (second (updated) edition). Food and Agriculture Organization of the United Nations, Rome, 1–136.

Folkema, M. P., 1989: Handbook for small-to-medium size fuelwood chipping operations. Forest Engineering Research Institute of Canada, Pointe Claire and Vancouver, 1–48.

Hall, P., Gigler, J. K., Sims, R. E. H., 2001: Delivery systems of forest arisings for energy production in New Zealand.

Biomass and Bioenergy 21(6): 391–399.

Moriguchi, K., Suzuki, Y., Gotou, J., Inatsuki, H., Yamaguchi, T., Shiraishi, Y., Ohara, T., 2004: Cost of comminution and transportation in the case of using logging residue as woody biofuel (in Japanese with English abstract). Journal of the Japan Forestry Society 86(2): 121–128.

Yoshioka, T., Iwaoka, M., Sakai, H., Kobayashi, H., 2000: Feasibility of a harvesting system for logging residues as unutilized forest biomass. Journal of Forest Research 5(2): 59–65.

Yoshioka, T., Aruga, K., Sakai, H., Kobayashi, H., Nitami, T., 2002: Cost, energy and carbon dioxide (CO2) effectiveness of a harvesting and transporting system for residual forest biomass. Journal of Forest Research 7(3): 157–163.

Yoshioka, T., Hirata, S., Matsumura, Y., Sakanishi, K., 2005: Woody biomass resources and conversion in Japan: The current situation and projections to 2010 and 2050. Biomass and Bioenergy 29(5): 336–346.

Sa`etak

Usitnjavanje otpada pri sje~i i izradbi drva bubnjastim ivera~em: kalkulacija proizvodnosti i tro{ak pridobivanja drvne sje~ke [umski ostatak, tj. otpad pri sje~i i izradbi drva (grane i ovr{ine), jedan je od glavnih izvora biomase od koje se o~ekuje da bude izvor energije, odnosno zamjena uporabi fosilnih goriva. Godi{nja dostupna koli~ina {umskoga ostatka u Japanu trenuta~no se procjenjuje na 3 ´ 106 t/god. (ST), s kalorijskom vrijedno{}u od 60 PJ (16,7 TWh).

Uporaba {umskoga ostatka u energetske svrhe zahtijeva njegovo usitnjavanje i transport prije nego {to se pretvori u korisnu energiju – toplinu, struju ili teku}e gorivo. [umski se ostatak mo`e usitnjavati na mjestu sje~e stabala (sastojini), pomo}nom stovari{tu uz {umsku cestu ili na stovari{tu energane. [irom svijeta razvijene su i u terenskim uvjetima istra`ene razne vrste strojeva (sje~kalice, iveralice) za usitnjavanje {umskoga ostatka, ~ija je djelotvornost (proizvodnost i tro{kovi rada) veoma va`na za uporabu u operativnom {umarstvu.

Cilj je ovoga rada istra`iti zna~ajke usitnjavanja {umskoga ostatka bubnjastim ivera~em kroz: Þ proizvodnost velikoga ivera~a Þ izradu kalkulacije tro{kova usitnjavanja {umskoga ostatka na pomo}nom stovari{tu i prijevoza drvne sje~ke krajnjemu korisniku Þ strukturu tro{kova pomo}nih strojeva (utovariva~i), tro{kova gradnje stovari{ta te tro{kova dopreme, postavljanja i otpreme strojeva na stovari{te u ukupnom tro{ku pridobivanja drvne sje~ke

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Þ utvr|ivanje ravnote`e proizvodnih kapaciteta bubnjastoga ivera~a i ostalih strojeva u sustavu usitnjavanja {umskoga ostatka.

Istra`ivanje usitnjavanja {umskoga ostatka bubnjastim ivera~em provedeno je na pomo}nom stovari{tu sje~ine japanske kriptomerije (Cryptomeria japonica D. Don.) i primije{anih lista~a.

Bubnjasti je ivera~ (HD–9 Industrial Tub Grinder, DuraTech Industries International Inc.) konstrukcijski postavljen na prikolicu (priklju~no, vu~eno vozilo) duljine 7,72 m, {irine 2,49 m i visine 2,62 m. Snaga pogonskoga motora iznosi 205,1 kW, a ukupna masa agregata 8,76 t. Bubanj je dubine 1,2 m, s gornjim promjerom 2,91 m, odnosno donjim 2,29 m. Na dnu bubnja nalaze se ~eki}i kojima se usitnjava {umski ostatak. Ivera~ je opremljen i konvejerom za dobavu sje~ke u tovarni prostor kamiona.

Sustav pridobivanja drvne sje~ke na pomo}nom stovari{tu ~ine utovariva~ s hvatalom za utovar {umskoga ostatka u bubanj ivera~a i utovariva~ s korpom za utovar drvnoga ivera s tla u kamion. Unato~ opremljenosti bubnjastoga ivera~a konvejerom razlog uklju~ivanja utovariva~a s korpom u sustav pridobivanja drvne sje~ke jest postavljanje zahtjeva kretnosti kamiona za prijevoz sje~ke krajnjemu korisniku kao prioriteta.

Gusto}a sje~ke u svje`em stanju iznosila je 321 kg/m3, uz prosje~nu vla`nost 120,4 ± 12,6% mase sje~ke u suhom stanju. Gusto}a je suhe tvari usitnjenoga {umskoga ostatka iznosila 146 kg/m3.

Rezultati istra`ivanja pokazuju da: Þ proizvodnost bubnjastoga ivera~a iznosi 60 m3 rasute sje~ke po efektivnom satu rada uz ukupni tro{ak iveranja od 5,637 US$/m3, {to upu}uje na tro{kovnu pogodnost usitnjavanja drva ve}im ivera~ima u odnosu na manje ivera~e Þ udio tro{kova rada utovariva~a, gradnje stovari{ta te dopreme, postavljanja i otpreme strojeva na stovari{te iznosi 53% od ukupnoga tro{ka usitnjavanja {umskoga ostatka Þ u slu~aju prijevoza drvne sje~ke kamionima kapaciteta 40 m3 tri puta dnevno, ukupni tro{ak usitnjavanja i prijevoza iznosi 71,2 US$/t (ST), {to je pribli`no podjednako kao i u europskim zemljama koje u kori{tenju energije iz {umskoga ostatka ostvaruju zna~ajan napredak Þ analizom proizvodnih mogu}nosti bubnjastoga ivera~a i ostalih strojeva, u sustavu pridobivanja drvne sje~ke, mo`e se realno o~ekivati da se bubnjasti ivera~ izmjenjuje na vi{e radili{ta.

Klju~ne rije~i: biomasa, otpad pri sje~i i izradbi drva, bubnjasti ivera~, proizvodnost, tro{ak usitnjavanja i prijevoza

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Authors' address – Adresa autorâ: Takuyuki Yoshioka, PhD. Laboratory of Forest Utilization and Housing Department of Forest Science and Resources College of Bioresource Sciences, Nihon University 1866 Kameino, Fujisawa 252-8510 JAPAN e-mail: yoshioka@brs.nihon-u.ac.jp Rin Sakurai, PhD. Department of Forest Sciences Graduate School of Agricultural and Life Sciences The University of Tokyo 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657 JAPAN e-mail: sakurai@fr.a.u-tokyo.ac.jp Assoc. Prof. Kazuhiro Aruga, PhD. Department of Forest Science Faculty of Agriculture, Utsunomiya University 350 Mine, Utsunomiya 321-8505 JAPAN e-mail: aruga@cc.utsunomiya-u.ac.jp Assoc. Prof. Toshio Nitami, PhD. Department of Forest Sciences Graduate School of Agricultural and Life Sciences The University of Tokyo 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657 JAPAN e-mail: nitami@fr.a.u-tokyo.ac.jp Prof. Hideo Sakai, PhD. University Forest in Hokkaido Graduate School of Agricultural and Life Sciences The University of Tokyo Aza-yamabe 2 jyo Kita 1, Furano 079-1561 JAPAN e-mail: sakaih@fr.a.u-tokyo.ac.jp

Received (Primljeno): January 18, 2006 Accepted (Prihva}eno): September 21, 2006

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Emer. Prof. Hiroshi Kobayashi, PhD. Department of Forest Sciences Graduate School of Agricultural and Life Sciences The University of Tokyo 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657 JAPAN e-mail: hirosi_koba@yahoo.co.jp Croatian Journal of Forest Engineering 27(2006)2

Preliminary note

Road Traffic in Protected Forest Areas – Case Study in Triglav National Park, Slovenia Igor Poto~nik Abstract – Nacrtak The paper deals with traffic management strategy in the preserved forest area of the Pokljuka highland in the centre of the Triglav National Park in Slovenia. The idea of traffic management was raised by an increased number of visitors especially during the high tourist season. The management includes public and forest roads with special emphasis on ownership issues. The strategy foresees two-step management regulation of transport – parking and soft approach – informing. The strategy proposes the regulation of parking lots in the valley and on the plateau of Pokljuka, introducing alternative public transport, fees, providing wider tourist offer on the plateau and providing visitors with information about the natural environment, protected natural and forest areas, national park itself, code of behaviour in the natural environment, etc. The proposed traffic management strategy should be accepted by all sectors concerned in the studied area.

Keywords: traffic, forest roads, Pokljuka highland, Triglav National park, Slovenia

1. Introduction and research problem – Uvod i problematika istra`ivanja In recent years the Rousseau’s saying »Back to the Nature« has become actual due to the change of lifestyle not only in developed countries. Popularization of free-time activities in nature (mostly in forests) also increased the number of visitors in the regions of protected nature. In the case of Slovenia the only national park, Triglav National Park, is over visited especially during the high summer season.

The development of mass winter tourism in the Alps since 1960 has also raised the question in Slovenia: How to involve mountain areas into tourism? It seems that locations between 1,200 m and 1,500 m above the sea level are the most suitable for alpine tourist development where climate conditions make winter and summer season equally attractive (Jer{i~ 2001).

Beside the above mentioned, several different interests can be met in this picturesque area, such as tradition, intentions, visions of development. Traditionally forestry and agriculture are permanently present in the whole Alpine region and not only in the protected area of Triglav National Park. Inside the National Park a Military Training Centre is located on the plateau of Pokljuka with all facilities for biathlon competitions. Reference should also be made Croatian Journal of Forest Engineering 27(2006)2

to the interest of land owners – forest and pasture owners, Association of Mountaineers etc.

The regulation of traffic is absolutely required, as the area of protected nature is obviously overcrowded during the high season. It is not only a problem of parking; it is a problem of noise, disturbance of natural environment. The role of foresters is to propose such traffic regulation that would involve interests of visitors and protected nature.

2. Working methods and research object – Metode rada i podru~je istra`ivanja Such a complex problem as is the case of the area of protected nature requires complex working methods. Studying of References is just a beginning followed by field work using methods of observing and inquiring (Albinini 2003).

The research object is the plateau of Pokljuka which is a part of the Triglav National Park. Areas and roads (public and forest roads) with the most intensive traffic were taken into consideration. The study area of 6,703 ha is mostly covered by mountain forest with Norway spruce as a dominant tree species in associations Abieti-Fagetum prealpinum and Piceetum subalpinum. The average altitude of Pokljuka

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Fig. 1 Location of the Triglav National Park (www.sigov.si/tnp) Slika 1. Polo`aj Nacionalnoga parka Triglav (www.sigov.si/tnp)

Fig. 2 The plateau of Pokljuka as an area studied within the Triglav National Park (www.sigov.si/tnp) Slika 2. Visoravan Pokljuka – istra`ivano podru~je u Nacionalnom parku Triglav (www.sigov.si/tnp) 116

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ranges between 1,200 and 1,700 m above the sea level.

Firstly we established the capacity of the existing parking spaces on the plateau of Pokljuka and identifed the most intensively visited areas. These areas have lately been recognized as suitable or non suitable for visiting. Finally we determined the future development strategy for all suitable locations.

The existing parking spaces had various shapes so it took some time to survey all of them correctly.

Several smaller existing parking spaces were later recognized as unsuitable because their location was too close to the trees, places with possible erosion etc. We used Technical Guidelines (Anon. 1991) for projecting of urban traffic areas to establish the real capacity of parking spaces on the plateau of Pokljuka.

3. Results – Rezultati istra`ivanja 3.1 State of the Art – Posljednja dostignu}a Visitors of Pokljuka are: Þ Stationary visitors from cottages, inns, hotel on the plateau, Þ Owners of summer cottages (only on the Goreljek mountain more than 120 cottages), Þ Daily visitors: coming from tourist centres like Bled and Bohinj and other parts of Slovenia and neighbouring countries, Þ Land owners.

The most important and popular activities are: Þ Hiking and picking up mushrooms, blueberries etc., Þ Mountaineering: plateau is an ideal starting point for mountaineering to Triglav group mountains, Þ Mountain biking: for an average biker the plateau with several roads is suitable because of gentle road slopes and low traffic mainly on forest roads, Þ Cross country skiing: suitable for winter sports because of the natural shape of plateau, numerous unplugged forest roads and paths, Þ Free skiing: increasingly popular in recent years.

Here are some data to get an impression of the number of visitors during the summer season: in summer 1997 ([olar 2002) on an average working day 1,850 persons visited Pokljuka, 3,880 on an average weekend day and more than 182,000 during the season. The problem should be considered thoroughly because we deal with traffic in protected natural environment.

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On the basis of answers of 21 different local communities, associations and services concerned about Pokljuka and Triglav National Park it can be concluded that 90% of persons concerned believe that the situation on Pokljuka is problematic. According to their answers the responsibility is to be given to the Triglav National Park Organization (100%), local community (infrastructure – 90%), state (Ministry of Transport and Communications and Ministry of Defence – 60%), Slovenian Forest Service (forest roads – 60%) etc.

One of the questions was also which professions (professionals) should be involved into the working group in order to prepare the proposal of the plateau management. The answers focused on foresters, biologists, lawyers, economists, etc. Therefore foresters are the professionals who are supposed to be the most qualified to prepare the guidelines for traffic regulation.

3.2 Proposal of Traffic Regulation – Prijedlog regulacije prometa Every traffic regulation should comprise: Þ Determination of preferential directions and traffic management, Þ Limitations of road usage according to the type of traffic, Þ Speed limits and measures in order to slow down the traffic, Þ Regulation of parked vehicles, Þ Determination of low-speed zones and pedestrian zones, Þ Determination of other commitments.

There is no transit traffic on Pokljuka so parking places are necessary. Traffic should be directed toward several organized parking lots away of zones of quietness. In the first phase of regulation the existing locations are determined (considering the capacity and proximity of locations with higher level of protection) as suitable or non suitable for parking. If the location is suitable it should be equipped with information tables (maps, current location, free-touse and closed roads, places of natural heritage, important objects, etc.

In the second phase of traffic regulation on Pokljuka the possibility is considered of larger central parking on the plateau and in the valley as well, along with the implementation of the public transport system from the valley to the plateau. Here there are two possibilities: Þ To enable access to the plateau until the parking lots are filled and later use the parking spaces in the valley,

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Þ Parking only in the valley and use of public transport system from the valley to the plateau.

The basic purpose of this strategy is to convince visitors as much as possible to leave their cars in the valley.

Another point of view is the time aspect. The traffic limitations could be: Þ Permanent, Þ Temporary during the summer and winter season, Þ Temporary during the sport events.

Introducing of high parking fee on the plateau and free parking in the valley with free public transport (included in the entrance fee) might bring adequate results in high season. Permanent traffic limitations might be non productive because traffic out of the season is very limited and not problematic to the environment.

We should also consider road barriers, meaning that roads are only used for bikes and pedestrians.

Positive aspects of barriers are: Þ Effective protection of nature and zones of quietness, Þ Efficient utilization of forest functions, Þ Safe implementation of forest operations.

Beside positive effects, road barriers also bring negative effects. This measure should be introduced thoroughly and only be limited to the high season.

The last step in traffic regulation is the so-called »soft approach«. Traffic regulation strategy foresees soft approach where restrictive measures are not suitable. The purpose is to inform and to advice visitors especially at the locations of private property. Signs of wood or other natural material with symbols of expected behaviour should be used. Soft approach is an alternative for road barriers during the low season when the barriers are not necessary.

4. Discussion – Rasprava The proposed strategy is based on the understanding that investing in the areas of protected nature – in our case traffic regulation – is an investment and not consumption. Natural environment and spending spare time in pure nature will be increasingly demanded. The intensity of growth and locations can hardly be predicted; we expect increased visit to the most popular and attractive locations. Traffic and environmental problems of over-visited locations of the Pokljuka plateau are limited to the high season.

In our opinion it is crucial to provide thorough infor-

Fig. 3 Road barriers are an effective means of traffic regulation if implemented thoroughly Slika 3. Rampe su u~inkovito sredstvo regulacije prometa ako su propisno postavljene 118

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Fig. 4 Symbols of expected behaviour in natural environment Slika 4. Znakovi o~ekivanoga pona{anja u prirodnom okru`enju

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paper are based on the estimation and traffic counting on rush days. Another problem is related to forest roads: basically forest roads are opened for tourist traffic along with forest traffic. The problem is how to ensure higher standard of transportability (better maintenance, traffic signs, etc.), which is necessary for safe traffic and however not required by the forest management. In future years an increasing number of visitors may be expected as well as disturbance of the natural environment. The index of motorization (relation between population and number of personal cars) shows a trend of intensive decreasing, which means more vehicles and visitors not only in towns but also in regions like Pokljuka.

The funds allocated for the maintenance of forest roads are insufficient although the contribution of the state budget for the maintenance of forest roads is as high as 35%. It seems that the introduction of the toll, entrance ticket, tourist tax, environmental tax, necessary. We should all be aware that pure nature and its protection are simply not free.

5. References – Literatura Anon., 1991: Technical Guidelines for Projecting of Urban Traffic Area. Traffic Technical Institute, Faculty of Civil and geodetic Enginering, University of Ljubljana, p. VII/11– VII/22.

Anon., 2000: Guidelines for Protected Area Management Categories (Interpretation and Application of the Protected Area Management Categories in Europe). Grafenau, IUCN/ Europarc Federation, 46 pp.

Albinini, M. 2003: Traffic Management Strategy for Protected Areas – Case Study Pokljuka. Graduation thesis, University of Ljubljana Biotechnical Faculty Dep. of Forestry and Renewable Forest Resources, 106 pp. http://www.sigov.si/tnp/. Triglav National Park (in English). http://www.statsi/engrindex.asp. Statistical office of the Republic of Slovenia (in English). http://www.uradni-list.si/index.jsp. Official Gazette of Republic of Slovenia (in Slovene).

Fig. 5 Trend of index of motorization in Slovenia Slika 5. Prikaz indeksa motoriziranosti stanovni{tva u Sloveniji

mation to visitors and this should be involved in the strategy already at the very beginning. Traffic regulation also brings some other information: distribution of visitors during the season and migration during the working days and weekend days, information on visitors’ expectations, social distribution of visitors, etc. Information and data used in this

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Jer{i~, M., 2001: National Park and Regional Development.

In [olar M. (ed.): Triglav National Park – 20 years later.

Bled, 51–58.

McNelly, J. A. et all., 1994: Guidelines: Development of National Parks and Protected Areas for Tourism. Madrid, WTO, UNEP, 53 pp. [olar, M., 2002: Principles of Adjustment of Recreational Use in Protected Areas – Case Study Triglav National Park. Master thesis, University of Ljubljana Biotechnical Faculty Dep. of Forestry and Renewable Forest Resources, 160 pp.

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Sa`etak

Cestovni promet u za{ti}enim {umskim podru~jima – studija za Nacionalni park Triglav Moderan ~ovjek velik dio svoga slobodnoga vremena provodi u prirodi bave}i se raznim aktivnostima. Zbog toga stalno raste broj posjetitelja u {umskim, a poglavito u za{ti}enim {umskim podru~jima, koja svojom primarnom {umskom prometnom infrastrukturom (javne i {umske ceste s pripadaju}im cestovnim objektima) nisu dimenzionirana za takav promet. Tijekom ljeta 1997. godine radnim je danom prosje~no 1850 osoba posjetilo Pokljuku, u dane vikenda taj je broj bio 3880. Te je godine zabilje`eno ukupno 182 000 posjetitelja.

Osim problema parkirnih mjesta javlja se i problem one~i{}enja okoli{a, uznemiravanja `ivotinja bukom i dr.

Zada}a je {umara da predlo`e regulaciju prometa koja }e s jedne strane usuglasiti interese posjetitelja, a s druge strane osigurati opstojnost za{ti}enih {umskih podru~ja.

Istra`ivanja prikazana u ovom radu provedena su na visoravni Pokljuka, sastavnom dijelu Nacionalnoga parka Triglav u Sloveniji (slika 1 i slika 2). Istra`ivani se objekt povr{ine 6703 ha nalazi na nadmorskoj visini izme|u 1200 i 1700 m te kao takav predstavlja izuzetno pogodno podru~je za razvijanje i zimskoga i ljetnoga planinskoga turizma. Najpro{irenija je obi~na smreka (Picea abies L.), koja raste u {umskim zajednicama Abieti-Fagetum prealpinum i Piceetum subalpinum.

Sastavljen je kompleksan upitnik koji je ispunio 21 ispitanik (lokalna zajednica, udruge, slu`be) koji su na razli~ite na~ine povezani s Pokljukom i Nacionalnim parkom Triglav. Oko 90 % anketiranih smatra kako je situacija na Pokljuki problemati~na i da zahtjeva odre|ene aktivnosti. Kao stru~njaci koji bi trebali biti uklju~eni u radnu skupinu za izradu prijedloga gospodarenja visoravni Pokljuka navedeni su na prvom mjestu {umari, zatim biolozi, pravnici, ekonomisti i dr.

Snimljena je postoje}a situacija na terenu te odre|en kapacitet postoje}ih parkirnih mjesta. Locirana su naj~e{}e posje}ivana podru~ja koja su zatim klasificirana u ona pogodna i u ona nepogodna za posje}ivanje.

Parkirali{ta su bila dosta razbacana i razli~ita oblika te je trebalo prili~no vremena kako bi se ona valjano prikazala.

Mnoga manja parkirali{ta prepoznata su kao nepovoljna ponajprije zbog blizine stabala (mogu}nost o{te}ivanja), zbog smje{taja na erozivnim povr{inama itd. Kori{tenjem Tehni~kih uvjeta za projektiranje u urbanim prometnim podru~jima (Anon. 1991) utvr|en je stvarni kapacitet povoljnih parkirnih mjesta na visoravni Pokljuka.

Posjetitelji Pokljuke razdijeljeni su na: Þ stacionirane posjetitelje koji vi{e dana provode u planinskim ku}ama, apartmanima i hotelima Þ jednodnevne posjetitelje koji dolaze iz turisti~kih sredi{ta u blizini (Bled, Bohinj), iz ostalih krajeva Slovenije, ali i iz susjednih zemalja (Austrija, Hrvatska, Italija) Þ vlasnike ljetnih planinskih ku}a Þ vlasnike {umskih i poljoprivrednih povr{ina.

Najva`nije i najpopularnije aktivnosti kojima se bave posjetitelji Pokljuke jesu: planinarenje, skupljanje {umskih plodova (gljiva, borovnica i dr.), brdski biciklizam, skija{ko tr~anje, slobodno skijanje (izvan ure|enih skija{kih staza) i ostalo.

Sukladno prijedlogu regulacije prometa na Pokljuki, u prvoj fazi promet treba usmjeriti prema nekoliko ve}ih parkirali{ta, smje{tenih na povoljnim mjestima i udaljenih od podru~ja pod najve}om za{titom (zones of quietnnes).

Parkirali{ta treba urediti te opremiti informativnim tablama (zemljovidi, postoje}i polo`aj, provozne i zatvorene ceste, zna~ajna prirodna podru~ja i objekti itd.). U drugoj fazi predvidjeli smo mogu}nost velikoga sredi{njega parkirali{ta na visoravni, ali i parkirali{ta u dolini uz uvo|enje javnoga transportnoga sustava iz doline na visoravan. Izra|ene su dvije ina~ice: Þ parkiranje na visoravni do popunjenosti kapaciteta sredi{njega parkirali{ta, a nakon toga slijedi zatvaranje prilazne ceste za visoravan te usmjeravanje vozila na parkirali{te u dolini uz uvo|enje javnoga prijevoza do visoravni Þ parkiranje samo u dolini uz javni transportni sustav iz doline na visoravan.

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Vremenska sastavnica ograni~enja prometovanja tako|er je vrlo bitna. Zabrana prometovanja mo`e biti stalna (tijekom ~itave godine), povremena tijekom ljetne i zimske turisti~ke sezone (ili samo u glavnoj sezoni) te povremena samo tijekom ve}ih sportskih doga|anja. Uvo|enje visoke cijene parkiranja na visoravni te slobodnoga parkiranja u dolini uz isto tako slobodan javni prijevoz (cijena kojega je uklju~ena u ulaznicu) moglo bi donijeti dobre rezultate u glavnoj turisti~koj sezoni. Stalna zabrana prometovanja nije potrebna jer je promet izvan turisti~ke sezone ograni~en i nije {tetan za okoli{.

Razmatrana je i uporaba rampi na cestama, ~ime one postaju upotrebljive samo za bicikliste i pje{ake. Uz pozitivne strane te mjere, kao {to su u~inkovita za{tita prirode i podru~ja pod najve}im stupnjem za{tite od prometa, sigurno provo|enje {umskih radova i dr., definirane su i negativne strane. Stoga rampe treba primjenjivati mjestimi~no te samo tijekom glavne turisti~ke sezone.

U kombinaciji s restriktivnim mjerama regulacije prometa, a posebno tamo gdje takve mjere nisu pogodne, treba primijeniti tzv. »mekani pristup» (soft approach). Cilj je tih mjera informirati i obavijestiti posjetitelje odgovaraju}im znakovima {to u prirodi nije dopu{teno ~initi (slika 4). Znakovi trebaju biti izra|eni od drva ili kojega drugoga prirodnoga materijala kako bi se {to bolje uklopili u prirodno okru`enje, a dobra su zamjena za primjerice rampe izvan glavne turisti~ke sezone.

Predlo`ene mjere regulacije prometa u za{ti}enom {umskom podru~ju visoravni Pokljuka u Nacionalnom parku Triglav predstavljaju investiciju u budu}nost o~uvanja prirodnosti i ljepota {uma. Problem pove}anoga prometa uo~en je samo u glavnoj turisti~koj sezoni. Neizbje`an je daljnji rast broja posjetitelja za{ti}enim {umskim podru~jima. To je s jedne strane uvjetovano `eljom ljudi za provo|enjem slobodnoga vremena u {to prirodnijem okru`enju daleko od svakodnevne gu`ve i buke, a s druge strane stalnim smanjivanjem indeksa motoriziranosti stanovni{tva (predstavlja odnos izme|u broja stanovnika i broja motornih vozila), ~ime za{ti}ena {umska podru~ja postaju dostupna sve ve}emu broju ljudi (slika 5).

Poseban je problem povezan s javnom uporabom {umskih cesta te time iniciranom potrebom pove}anja njihova postoje}ega standarda (~e{}e i zahtjevnije odr`avanje, dodatni cestovni objekti, prometni znakovi i dr.) koji je dostatan za potrebe gospodarenja {umom, ali je nedovoljan za siguran javni promet. Iako dr`ava sufinancira odr`avanje {umskih cesta s 35 % potrebnoga godi{njega iznosa, financijska su sredstva potrebna za teku}e i periodi~no odr`avanje {umskih cesta nedovoljna. Stoga treba razmisliti o sufinanciranju radova odr`avanja primarnih {umskih prometnica iz npr. ulaznica u nacionalni park, turisti~kih taksi, davanja za za{titu okoli{a i drugih izvora. Trebamo biti svjesni kako o~uvanje prirodnih bogatstava ne mo`e biti besplatno.

Klju~ne rije~i: promet, {umske ceste, visoravan Pokljuka, Nacionalni park Triglav, Slovenija

Author's address – Autorova adresa:

Received (Primljeno): September 15, 2006 Accepted (Prihva}eno): November 28, 2006 Croatian Journal of Forest Engineering 27(2006)2

Assoc. Prof. Igor Poto~nik, PhD. University of Ljubljana, Biotechnical Faculty Department of Forestry and Forest Resources Ve~na pot 83 1000 Ljubljana SLOVENIA e-mail: igor.potocnik@bf.uni-lj.si

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Preliminary note

Technological and Environmental Parameters of Helicopter Timber Extraction in Slovakia Valéria Messingerová, Jozef Tajbo{ Abstract – Nacrtak This paper summarises the results of the research whose aim was to evaluate technical, technological, ergonometric and environmental parameters of timber air extraction. Ground based extraction technologies are localised to land routes where the possibilities of development are partially exhausted. Searching the way to eliminate the consequences of extraction technologies on the environment was carried out by use of three dimensional technologies.

The aim of this work was to elaborate a design of technological procedures for timber transportation by helicopters depending on the type of felling, terrain configuration, technical aids, assessment of performance characteristics, design of work safety and assessment of noise level in the forest environment.

Keywords: timber extraction, helicopter, mountain forest

1. Introduction – Uvod The idea of the use of air transportation was born in 1911 by the Prussian forester Alfred Zimmermann (Dykstra 1976). The first experiments on timber extraction by helicopters were carried out in Caucasus in 1954 (Gordijenko 1987), and a few years later in Scotland, in 1956. In late 60s and early 70s experiments with air timber extraction were carried out in North America (Heinimann 1995). Other experiments were carried out in Norway, Canada, the former USSR, and the USA. The first experiments in former Czechoslovakia were performed by Kostroò (1972).

At present the technology of timber extraction by helicopter is used in many forestry-developed European countries, e.g. Switzerland, France, Austria, and Germany. In the USA and Canada the share of this technology in overall capacity of the extracted timber is even more significant. In economically and ecologically developed countries the air transportation is being shifted from the position of emergency measures to common operation technology.

In the mountain forests of Switzerland, the use of helicopter accounts for up to 20% of timber extraction. Interest was also shown by the Forestry Commission from Great Britain, which visited Switzerland Croatian Journal of Forest Engineering 27(2006)2

in 1995 and they are now researching the possibility of its use in Britain. The work is carried out by private companies. In Austria and Germany the latest helicopter K-Max is being used and it is owned

by AHT Company in Innsbruck. The researches of French authors focus their interest on the use of helicopters for home production. In the USA a Helicopter Logging Committee has been established just for the purpose of supporting the use of helicopters in aerial logging.

As in Slovakia there is a high rate of forest acreage in mountain areas, this topic is interesting and shows the possibilities of decreasing the damage to forest ecosystems. In Slovakia the contribution for the support of such an environmentally friendly technology in mountain areas is well recognized, especially in the forests with a high-level of legislative protection. The objective was to elaborate the review of effectiveness, norms and directives related to the stated technology and lay good theoretical basis for technologies of timber air transportation as well as other activities in forestry that use helicopters e.g. protection of forests and support to all tasks that provide good prospects for timber extraction by helicopters and elaboration of technological procedures, work safety rules and environmental conditions.

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2. Research methods – Metode istra`ivanja

not been used in any known literature so far nor has the noise spreading model in the nature during helicopter timber extraction.

Methodology was elaborated in several areas: A) Assessment of technical possibilities and properties of various types of helicopters used for timber extraction Based on studied literary resources, a review was prepared of helicopters used in timber extraction, and a list of technical parameters was prepared for better orientation focusing on the most important parameters such as performance, useful load, speed, and other design characteristics of individual helicopters during timber extraction. For clarifying the technical scope, the basic helicopter flight operation was elaborated and lifting capacity of Mil Mi-8 helicopter used in Slovakian conditions was determined.

B) Designing a technological procedure according to the type of felling Based on the results gained from the use of helicopter in timber extraction at several sites in the forests of the Slovak Republic and especially based on results and experience in organising helicopter timber extraction in the intended regeneration felling, a technological procedure was designed with the emphasis on improving overall efficiency while observing and adhering to safety at work regulations. The technological procedure was designed for the preparation and organisation of work in key stages of the working cycle (stand, landing, air operations).

C) Assessment of efficiency characteristics of Mil Mi-8 helicopter The efficiency of helicopter timber extraction was evaluated by chronometric measurements of Mill Mi-8 helicopter used in the mountain areas of the Slovak Republic. During processing of the salvage timber (Belianske Tatry mountains, Javorina mountain range, Srdie~ko mountain area of Ru`omberok), time consumption was evaluated for a working cycle and for individual work operations, as well as shift efficiency, size of load, number of logs in a load and the same parameters indicating efficiency of Mil Mi-8 helicopter during regeneration felling in the protected area of Po¾ana.

D) Helicopter noise stress of forest and work environment In particular conditions at several sites (Belianske Tatry, Po¾ana, Muráò), measurements were carried out of noise affecting workers and the surrounding nature. The methodology of processing by DTM has

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3. Results – Rezultati 3.1 Evaluation of technical possibilities and properties of various helicopters used in timber extraction – Procjena tehni~kih mogu}nosti i zna~ajki razli~itih helikoptera kori{tenih za izno{enje drva Regarding the properties of helicopters they present a practical and irreplaceable means of transportation. The possibility of vertical flight and flight down without dependence on long take-off and flight down runway gives incredibly wide operational space to helicopters, because flight down and taking-off do not need large and especially designed area. Another important quality – »hanging« – (possibility to remain in the air at one place for a necessary time) enables the transportation of a load in the areas with low bearing capacity or at places which are not accessible by other means of land transportation. Untraditional manoeuvring properties enable helicopters to fly at a distance very close to land. Lower speed, compared to other means of air transport, is an advantage in case of timber extraction. Due to these properties, their use is the most common technology in air extraction. Table 1 shows some selected types and selected technical characteristics of helicopters used in timber extraction.

3.2 The design of technological procedures in accordance with the type of felling – Oblikovanje tehnolo{kih postupaka prema vrsti sje~e The choice of technological procedure should be adapted to technical equipment, terrain and climatic conditions, type of felling, volume of extracted logs.

It is possible to extract whole trees, logs, or assortments by helicopter. The transportation of logs is the most profitable; if the weight is exceeded, they must be shortened to assortments. Trees are extracted in case of e.g. bark-beetle salvages when stand sanitation is required.

Highly effective technology of helicopter timber extraction requires thorough technological preparation of a workplace and perfect team work of all involved partners.

Technological procedure can be divided into several work stages which can be prepared individually and however they must be compiled into one harmonious corpus.

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Table 1 The review of parameters of selected helicopters used in wood extraction Tablica 1. Pregled zna~ajki odabranih helikoptera za izno{enje drva

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From the viewpoint of work management it is necessary to plan in detail as follows: Þ preparation and work in a stand, Þ establishment of sufficient number and suitable position of landings, Þ meeting technical requirements of helicopter operation.

The efficiency of helicopter technology for timber extraction is significantly influenced by quality and extent of preparation work in a stand. Due attention must be given to this stage as this might be the stage to decide on the result of the whole operation and namely on economic parameters and occupational safety. Different approach to preparation work is influenced by the type of felling.

Work in a stand during salvage cutting requires preparation according to the type of salvage (storm, insect) and if required initial work shall include debranching and bucking of tree trunks from the root system.

Processing of salvage proceeds from the upper part of a hill slope and preparation work should be carried out before the beginning of timber extraction. Small sized logs should be piled at the sites meeting the requirements of safe log fastening and take-off of a helicopter. Referring to a strewed salvage mass in a standing stand, this means that a helicopter can easily manage to lift the logs even in this stand.

Technological work progress in the stand will significantly influence the technology of helicopter transportation of cut timber (intended regeneration cutting).

When directional felling is provided, it is possible to achieve an optimal load weight for a helicopter according to useful load. Compared to processing of salvage timber, in most cases it is not necessary to pile logs in a stand. For logs of higher volume, it is necessary to shorten them because of allowed loading of a helicopter. The length of assortment is influenced by timber species, volume weight of timber, moisture contents and type of assortments.

The preparation of loads for a helicopter during felling influences the time consumption needed for fastening the load as well as the time of the whole working cycle. Compiling the load and fastening the burdens as well as unfastening the loads at the landing is carried out by workers (fasteners), who are trained specifically for working with loads under a helicopter.

The efficiency of a helicopter depends on the time of a return, on the size of a load per cycle and on compulsory idle time. The time of a working cycle depends on the efficiency of fasteners working in a

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stand, who if they manage to assess the load weight correctly and fasten logs quickly can avoid repeated unfastening for overweight. To check the correct load weight, every helicopter is equipped with a weighting gauge for measuring the weight. A helicopter can extract timber from any place. It is better if timber is in an open area, e.g. at the edge of a stand, but it can also easily manage to lift a load above a stand from among the trees.

From the technological point of view the most demanding part is fastening loads in a stand. This operation must be carried out quickly and at the same time safely. The conditions of fastening are demanding especially in processing salvage timber.

It is advisable to have at least two workplaces with two fasteners at the stand being processed, thus creating conditions for the preparation of further loads.

The load size depends mainly on the carrying capacity of a helicopter, season of the year, and time of the day in dependence on temperature conditions. It is more profitable if the load consists of fewer logs as this shortens the time of fastening up.

The load is fastened to a helicopter either by a winch rope or more often by a helicopter fixed rope because lifting the load by winch is slower than by lifting via fixed rope.

Work procedures and technical devices common in industry dealing with load transportation are applied. Coordination of the whole working team is managed by using transmitters.

The form of forest management is not a limiting factor for using this technology. From the point of view of technical and technological managing it is possible to take into account the use of this method not only in clear cutting and partial felling but in selective cutting shelterwood system if the economic conditions are acceptable for both contractual parties.

Regarding time consumption per cycle, a larger freely accessible area or a kettle-shaped area is better than a selective cutting method. The best option is if the area has been prepared and branches cut off, but if necessary it is possible to extract the trees. The hill slope enables the pilot better orientation in hanging against a hill. If the crew has a possibility to fly over the area from the bottom part, the pilot has a perfect picture of the prepared timber. Lowering down of underslung equipment hooks is done quickly, the fasteners are in an visual contact with the crew, so as to move off at a safe distance from the timber. Lifting the timber and its taking off can be performed without avoiding obstacles and the departure can be made without rising which is made possible by the hill slope. The departure is possible in every azimuth from a slope. When applying a selection method, all Croatian Journal of Forest Engineering 27(2006)2

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Table 2 Time consumption per working components and basic data about timber extracted by helicopter in Belianske Tatry for an average extraction distance of 700 m (Messingerová 1994) Tablica 2. Utro{ak vremena sastavnica rada i osnovni podaci o izne{enom drvu helikopterom u Belianskim Tatrama pri srednjoj udaljenosti privla~enja drva od 700 m (Messingerová 1994) No. Br.

Working components Radne sastavnice Flight without load into stand 1 Let bez tereta u sastojinu Flying down into stand 2 Let prema dolje u sastojinu Load fastening 3 Vezanje tereta Lifting of load in stand 4 Podizanje tereta u sastojini Flight with load 5 Let s teretom Flying down into landing 6 Let prema dolje do stovari{ta Load unfastening 7 Odvezivanje tereta Flying up the landing 8 Uzdizanje sa stovari{ta Cycle time 9 Trajanje radnoga ciklusa Average volume of load, m3 Prosje~an obujam tovara, m3 Average number of logs per load, pcs Prosje~an broj trupaca u tovaru, kom.

Average volume of extracted logs, m3 Prosje~an obujam privu~enih trupaca, m3

Arithmetic mean, min Aritmeti~ka sredina, min

Mean error, min Srednja pogre{ka, min

No. of observations Broj opa`anja

1.53 ± 1.66

0.24

49

0.56 ± 0.35

0.05

60

0.69 ± 0.42

0.06

58

0.74 ± 0.62

0.08

63

2.10 ± 0.72

0.10

55

0.26 ± 0.21

0.03

57

0.34 ± 0.19

0.03

57

0.24 ± 0.13

0.02

57

5.92 ± 1.24

0.19

49

2.87 ± 0.71

0.09

69

5.3 ± 2.4

0.3

69

0.54 ± 0.38

0.05

69

these positive circumstances do not appear because it is necessary to push hooks into a stand. The most demanding situation is at the flat surface, where there is no advantage of a contra-hill and it is necessary to look for fasteners in a stand. Yet, an advantage of this method is that a helicopter can work effectively also in selection felling although the time consumption for the working cycle of this method is a bit higher.

In the technological preparation of the workplace, the selection of sufficient time and accessibility of landings play an important role. Unfastening a load can be done at roadside landing manually, mechanically, automatically. Manual unfastening increases time requirements because workers can approach the load after its stabilisation on the ground. Automatic unfastening shortens the length of the whole cycle.

Croatian Journal of Forest Engineering 27(2006)2

The place of unfastening, landing, must be chosen so that the load can be put down without time and space limitations. The size of landing depends on the amount of timber and the requirement of timber sorting, e.g. according to timber species or assortments. The storage area must provide the conditions for a continuous work operation in terms of its size and position. Inappropriate landings are those which are small and have uneven surface, large obstacles or »untouchable« obstacles at the edge.

During processing salvage timber, it is difficult to carry out the requirement for sorting timber, and however, when the work of timber extraction from the intended felling is well organised, it is possible to sort out the timber into piles by requirements.

Regarding the fact that in Slovakia there are no generally applicable safety laws for the technology of helicopter timber extraction compared to ground

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Table 3 Quantity of timber extracted by helicopter in the Pol'ana protected area Tablica 3. Koli~ina iznesenoga drva helikopterom u za{ti}enom podru~ju Polana Date Datum 8. IX 9. IX 10. IX 11. IX 12. IX 13. IX Total – Ukupno

Conifers ^etinja~e 43.20 149.14 36.43 30.17 33.97 114.33 407.24

Broadleaves Lista~e m3 136.10 76.74 156.89 150.27 96.18 45.09 661.27

Total Ukupno 179.30 225.88 193.32 180.44 130.15 159.42 1068.51

Table 4 Time consumption per working components in timber extraction by helicopter in Pol'ana protected area for an average extraction distance of 800 m Tablica 4. Utro{ak vremena sastavnica rada pri izno{enju drva helikopterom u za{ti}enom podru~ju Polana pri srednjoj udaljenosti privla~enja drva od 800 m No. Br.

Working components Radne sastavnice

Flight without load into stand Let bez tereta u sastojinu Flying down into stand 2 Let prema dolje u sastojinu Load fastening 3 Vezanje tereta Lifting of load in stand 4 Podizanje tereta u sastojini Flight with load 5 Let s teretom Flying down into landing 6 Let prema dolje do stovari{ta Load unfastening 7 Odvezivanje tereta Flying up the landing 8 Uzdizanje sa stovari{ta Cycle time 9 Trajanje radnoga ciklusa Number of flights per day Broj letova dnevno Time consumption per fuelling Utro{ak vremena pri to~enju goriva Time consumption per daily maintenance of helicopter Utro{ak vremena dnevnoga odr`avanja helikoptera 1

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Time consumption Utro{ak vremena min

Percentage Postotni udio %

1.16

23

0.29

6

0.62

13

0.38

8

1.61

33

0,33

7

0.29

6

0.18

4

4.83

100

72 11.23

45.20

based timber extraction technologies and the requirements in this area are higher, a design of safety principles has been drawn. The design is based on safety in flight operations and considers specific conditions of helicopter use in forestry.

3.3 Performance characteristics for helicopter Mil Mi-8 – Radne zna~ajke helikoptera Mil Mi-8 The most important parameters in timber extraction at various sites in the mountain forests in Slovakia are shown in Tables 2, 3, 4 and 5.

3.4 Effects of helicopter noise stress on forest and working environment – Optere}enje {umskoga i radnoga okoli{a bukom helikoptera The intensity of outer noise was not only measured directly at the workplace but also in the surrounding area in a hectare network at a 2 km distance. The measuring equipment of the firm Bruel and Kjaer was used with a built-in A weight filter.

The noise level was measured at a different distance from the helicopter during hanging and during the flight.

The level of the machine noise is assessed in accordance with the relative directives from two viewpoints. For people directly involved in the work with the machine, the noise at the workplace is relevant and for the others the outside noise is relevant.

In the first case, the highest possible level accounts for LP = 80 dB(A), and as the work of fasteners can be considered physically demanding in terms of accuracy and concentration, the correction of the basic level –5dB will be applied. In the second case the value of 55 dB(A) is applied as the highest accepted value for the air operation noise (Konrád 1973, Kon-

Table 5 Indicators of efficiency in timber extraction by helicopter Tablica 5. Pokazatelji djelotvornosti pri izno{enju drva helikopterom Efficiency indicator Pokazatelj djelotvornosti Average daily volume of extracted timber, m3 Prosje~an dnevni obujam privu~enoga drva, m3 Average number of logs per load, pcs Prosje~an broj trupaca u tovaru, kom.

Average volume of load, m3 Prosje~an obujam tovara, m3 Average volume of extracted logs, m3 Prosje~an obujam privu~enih trupaca, m3 Time consumption per 1 m3 of timber, min Utro{ak vremena po 1 m3 drva, min

Average value Srednje vrijednosti 178.08 1.61 2.10 1.38 2.48

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Table 6 Noisy and silent intervals during helicopter’s operation Tablica 6. Bu~ni i tihi intervali rada helikoptera Working components Radne sastavnice

%

Helicopter operation: 100 Rad helikoptera: Above a fastening place 32.2 Iznad mjesta vezanja tereta Above an unfastening place 14.4 Iznad mjesta odvezivanja tereta

Cycle Shift Ciklus Smjena intervala Noise Silence Noise Silence Buka Ti{ina Buka Ti{ina min 5.92

–

300.0

–

1.91

4.01

96.6

203.4

0.85

5.07

43.2

256.8

rád 1993, Konrád et al. 1993, Messingerová et al.

2000).

The measurements were processed into noise maps. In this paper, the results are presented from the High Tatra – The TANAP report, LS Javorina, Pod Muráòom locality. The model of noise propagation was developed from 180 values measured at 35 spots. For comparison, the results of measurements in Pol'ana, prepared in the environment of a digital terrain model, are also presented.

The helicopter timber extraction is 8–10 times more effective than ground based skidding technologies and as much as 20 times more efficient than cable yarding. This is the result of the fact that the forest environment and workers are exposed to the noise produced by helicopter for a much shorter time, which is particularly important in protected areas. During the research the noise was measured in the most severe conditions, at minimum distance from the helicopter (under the helicopter, or at the helicopter’s level on the slope). During a routine operation the noise values at the ground are usually lower.

The analysis was carried out of time consumption of individual operations and time of exposure to direct noise of the workers on the ground (Konrád and Messingerová 1993), and noisy and silent intervals were calculated for the staff working on the ground (Table 6). The load fasteners and unfasteners are exposed to an excessive noise only during a short part of a working cycle. During a shift a fastener is exposed in total to the noise for 97 minutes and an un-fastener for only for 43 minutes.

The measurements were evaluated by a topographic programme ATLAS. On the noise map (Fig. 1 – one square represents dimensions: 100 ´ 100 m) the three significant peaks stand out: Croatian Journal of Forest Engineering 27(2006)2

V. MESSINGEROVÁ and J. TAJBO[

Þ A – the place of fastening logs in a stand, Þ B – the place of fastening logs in free space (salvage place), Þ C – the landing where the load was unfastened.

The map was produced by synthesis of noise fields and it is not real, because a helicopter cannot appear at three different places at the same time.

This procedure was established to identify the area where the highest noise values at the workplace are exceeded.

The results show that the noise shortly exceeds the allowed limits, but they are likewise exceeded by tractors used for skidding timber. The excess is less significant, the changes of the level are not so rapid and the mentioned noise was only found in the vicinity of the tractor. However, it is present during the whole time of the tractor’s operation. At the distance of 2 m from the tractor the noise is 90–95 dB(A), at the distance of 20 m it is approximately 75 dB(A) (Konrád 1973)

Fig. 1 The map of noise intesity in the immediate helicopter’s surrounding in dB(A) Slika 1. Karta intenziteta buke u neposrednoj okolici helikoptera u dB(A) 129

V. MESSINGEROVÁ and J. TAJBO[

Technological and Environmental Parameters of Helicopter ... (123–133)

Fig. 2 The map of helicopter’s noise intensity isolines Slika 2. Karta izolinija intenziteta buke helikoptera u dB(A) If the helicopter is »hanging« above a working place (rope length: 30–50 m) the noise below it is 93–100 dB(A). The acceptable level of 80 dB(A) is at the distance ranging between 100 and 200 m depending on the terrain configuration. This is why the workers must use hearing protectors. The noise layout in a broken terrain has better spreading than in an open area due to the formation of noise traps (behind the ridge, in thick vegetation). In Figure 2 it can be seen that the noise is spreading over a wider area around Ke`marský {tít – a peak, Muráò – a mountain area, and in the Belianske Tatry – a mountain range.

The last measurements were carried out in the High Tatra, locality Javorina – Muráò. They were used to determine the noise model depending on the distance and elevation of helicopter’s flight.

The results of regression analysis in the following gradients of decreasing noise intensity are shown in Figures 3 and 4.

The significance of distance, flight height and terrain configuration was analyzed by the method of

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Fig. 3 Linear model of helicopter's noise intensity Slika 3. Linearni model intenziteta buke helikoptera Croatian Journal of Forest Engineering 27(2006)2

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V. MESSINGEROVÁ and J. TAJBO[

Table 8 Average values of intensity noise at different factor levels Tablica 8. Srednje vrijednosti intenziteta buke pri razli~itim razinama ~imbenika Distance – Udaljenost

Fig. 4 Power model of helicopter's noise intensity Slika 4. Eksponencijalni model intenziteta buke helikoptera Table 7 Factors significance Tablica 7. Zna~ajnost razlika ~imbenika Factor – ^imbenik Distance – Udaljenost Flight height – Visina leta Terrain configuration – Konfiguracija terena Total – Ukupno

F a P1 – a 66.812 0.000 00 1.000 00 11.866 0.000 00 1.000 00

b –0.64 –0.41

5.9585 0.003 38 0.996 62

–0.12

20.581 0.000 00 1.000 00 R = 0.87

one- and multi-factor analysis. The following classification was used for a terrain: Þ 1 – open terrain, plain Þ 2 – broken terrain in a slope Þ 3 – a valley off the flight route.

Table 7 shows that the distance influence and flight height are significant practically with a 100% probability and the influence of terrain brokenness has likewise a 99.62% probability.

Where: F – calculated value of F–division, a – significance level, P1-a – reliability degree, ß – partial coefficients of correlation (calculated by the method of multiple regressions), R – coefficient of multiple correlation.

(For the number of measurements n = 122, Ftab,0,05 ≈ 3.08) Croatian Journal of Forest Engineering 27(2006)2

Factor – ^imbenik Flight height – Visina leta

m

dB(A)

m

dB(A)

0 100 200 300 400 1200

95 81 74 69 65 50

0 35 40 45 50 60

112 83 80 78 77 71

Terrain configuration – Konfiguracija terena Class – dB(A) Razred 1 80 2 74 3 70

The values of b coefficients can be interpreted as the intensity of impact of individual factors within their synergic effect. Table 8 presents the average values of noise intensity at various factor levels. The average noise intensity during measuring was 77 dB(A).

To get a general perception of noise, several criteria must be taken into consideration, similarly to other physiological perception, resulting from physiology of perception organs. Various subjective noise perceptions depending on sound frequency of oscillation are processed into standardized curves of identical loudness levels – Fletcher-Munson curves (Smetana 1987).

4. Conclusion – Zaklju~ci The air transportation of timber is the most environmentally friendly technology of all current extraction technologies. The advantages of helicopter technology can be summarized as follows: Þ possibility to decrease requirements for making access into complicated terrain conditions of mountain stands, Þ possibility to improve the structure of mountainous forests, Þ fast processing of salvage felling requiring an immediate solution, Þ prevention of salvages in stands which are not considered accessible by traditional technologies, Þ minimum damage to soil by minimisation of the contact between the load and soil, Þ inhibition of consequential rainfall erosion, Þ no soil disturbances compared to ground based technologies,

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Technological and Environmental Parameters of Helicopter ... (123–133)

Þ as a result of avoiding ground based technologies, better hydrological conditions in mountain terrains, Þ minimised damage to remaining trees, Assuming that good planning and work organization are provided, taking into consideration safety and noise impact on the environment, it is possible to obtain good results in spite of the fact that compared to traditional technologies helicopter logging is the most risky one.

5. References – Literatura Abel, P., Sauloquin, S., 1991: Perestroika forestière: Les hélicoptères soviétiques se recyclent dans le débardage du bois, Arborenscences, No 31 – Janvier-Fevrier, Office National des Forêts, 14–16.

Dykstra, D. P.; 1976: Production rates and costs for yarding by cable, balloon, and helicopter compared for clearcuttings and partial cuttings. Forest Research Laboratory, School of Forestry, Oregon State Univ. Res. Bull. 22. Corvallis. 44 pp.

Dykstra, D. P., Heinrich, R., 1996: FAO model code of harvesting practice. FAO, Rome, 1–85.

Gordijenko, V., A., 1986: Helicopter timber logging. 18th IUFRO world congress, Division 3, 190–201.

Heinemann, H. R., 1995: Schreittechnologie – Perspektiven für die Forsttechnik. Oesterrreichische Forstzeitung 106(9): 56–59.

Heinimann, H. R., 1998: Holzrücken mit Helikoptern [Timber extraction with helicopters]. Wald und Holz 79(3): 7–10.

Heinemann, H. R., Caminada, L., 1996: Helicopter Logging in Switzerland, Analysis of Selective Logging Operations.

In Proceedings of IUFRO 3.06 Forest Operations under

Mountainous Conditions and the 9th Pacific Northwest Skyline Symposium (ed. I. B. Hedin), FERIC SR 116, 1–6.

Kaluckij, K. K., Lekarkin, I. J., D`aparidze, T. M., 1988: Technologija gornych lesozagotovok s primenenijem na transportirovke drevesiny vertoletov, Les. Choz. 61(6): 45–47.

Konrád, V., 1993: Za a`enie lesného prostredia hlukom vrtu¾níka (Charging the forest environment by helicopter noise). In: Zborník Jubilejná konferencia LVÚ, 2. sekcia ekológia pestovania lesa a lesná technika, 118–124.

Konrád, V., 1973: Vplyv hluku a vibrácií na pracujúcich pri sústreïovaní dreva traktormi (Noise and vibrations impact on workers at wood skidding by tractors). Referát ku skú{ke z a{pirantského minima, Zvolen, 71 pp.

Konrád, V., Messingerová, V., 1993: Rozbor technológie, spotreby ~asu a hluku pri pribli`ovaní dreva vrtu¾níkom (Analysis of the technology, time consumption, and noise during helicopter wood logging). AFF, TU Zvolen, 321– 333.

Kostroò, L., 1972: Výsledky ovìøení vrtu¾níku MI-8 pøi dopravì døeva v ^SSR. Lesnictví 18(2): 101–115.

Lambert, M. B., 1995: Computer supported planning for helicopter logging, USDA, Forest Service Paciffic Northwest Research Station, Portland, Oregon, USA, 1–10.

Messingerová, V., 1994: Sústreïovanie dreva vrtu¾níkom (Helicopter wood logging). Vedecko-pedagogická aktualita ~. 6, 1–50.

Messingerová, V., Tajbo{, J., 2000: Za a`enie pracovného a prírodného prostredia hlukom pri doprave dreva vrtu¾níkom Mi-8. (Charging the working and natural environment by noise during the Mi- 8 helicopter wood transportation) AFF, 42, TU Zvolen, 309–322.

Smetana, C., 1987: Ozvu~ování. SNTL Praha, 1–215.

Stampfer, K., Gridling, H., Visser, R., 2002: Analyses of Parameters Affecting Helicopter Timber Extraction. International Journal of Forest Engineering 13(2): 61–68.

Sa`etak

Tehnolo{ki i okoli{ni parametri izno{enja drva helikopterima u Slova~koj Rad prikazuje rezultate istra`ivanja tehni~kih, tehnolo{kih, ergonomskih i okoli{nih zna~ajki primjene helikoptera na izno{enju drva iz brdsko-planinskih {uma u Slova~koj. Pregled najva`nijih tehni~kih zna~ajki helikoptera koji se upotrebljavaju za izno{enje drva dan je u tablici 1.

Cilj je rada utvrditi tehnolo{ke postupke, pravila sigurnosti rada te okoli{ne uvjete koji }e osigurati pravilnu primjenu i u~inkovitost postupaka izno{enja drva helikopterom. Stru~no izvo|enje izno{enja zahtijeva visoku kakvo}u tehnolo{ke pripreme radnoga mjesta i savr{enu organizaciju rada. Tehnolo{ke postupke valja prilagoditi tehni~kim sredstvima, terenskim i klimatskim uvjetima, vrsti sje~e i obujmu drva za izno{enje. ^itava stabla, debla ili trupci mogu se iznositi helikopterima. Dulji se trupci moraju skratiti kako bi bili sukladni dopu{tenomu optere}enju helikoptera. Duljina je trupaca uvjetovana vrstom i specifi~nom te`inom drva, sadr`ajem vlage u drvu i vrstom sortimenta.

Priprema tovara u sastojini utje~e na smanjenje utro{ka vremena za vezanje tovara i time na trajanje cijeloga radnoga turnusa. Uvjeti za vezivanje osobito su zahtjevni i te{ki pri izvla~enju drva dobivenoga sanitarnim sje~ama. Racionalnije je na odre|enoj ~estici postaviti dva radili{ta (s po dva radnika koji ve`u teret na svakom

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V. MESSINGEROVÁ and J. TAJBO[

radili{tu). Time se u{tedi vrijeme za pripremu sljede}ega tereta. Koordinacija ~itavoga tima obavlja se uz pomo} prijenosnika. Pripremu tovara u sastojini, njegovo vezanje na vu~no u`e helikoptera te odvezivanje tovara na stovari{tu obavljaju radnici kop~a{i posebno pripremljeni za siguran rad u blizini helikoptera.

Trajanje radnoga ciklusa ovisi o spretnosti radnika koji ve`u tovar, njihovoj sposobnosti da odrede te`inu tovara, da brzo ve`u trupce i sprije~e odvezivanje u slu~aju prevelikoga optere}enja. Svaki je helikopter opremljen dinamometrom, ure|ajem za mjerenje te`ine tereta. Teret se mo`e odvezivati ru~no, mehani~ki ili automatski. Veli~ina tereta ovisi o kapacitetu nosivosti helikoptera, godi{njem dobu i dobu dana s obzirom na vremenske uvjete. Teret je uz helikopter privezan u`etom preko vitla ili ~e{}e pri~vr{}enim u`etom jer je podizanje tereta vitlom sporije nego fiksiranim u`etom. [tovi{e, vitlo smanjuje korisnu nosivost helikoptera. Fiksirano je u`e duga~ko 30 – 50 m.

Izbor dovoljno prostranoga stovari{ta i njegov smje{taj igra va`nu ulogu u tehnolo{koj pripremi radili{ta.

Lokacija stovari{ta mora omogu}iti spu{tanje tereta bez pote{ko}a. Veli~ina stovari{ta ovisi o koli~ini drva i zahtjevima razvrstavanja, npr. po vrstama ili sortimentima.

U slova~kom se {umarstvu za privla~enje drva koristi helikopter Mill MI-8 te su u tablicama 2, 3, 4 i 5 prikazni utro{ci vremena sastavnica rada i osnovni podaci o iznesenom drvu na dva mjesta istra`ivanja.

Izno{enje je drva helikopterima u~inkovitije 8 – 10 puta od privla~enja drva traktorima i do 20 puta od izno{enja drva `i~arama. Iz toga slijedi da je {umski ekosustav izlo`en buci za vrijeme rada helikoptera znatno kra}e vrijeme. Ta je ~injenica posebno zna~ajna u za{ti}enim podru~jima.

Mjerenja razine buke koja djeluje na radnike i okoli{ provedena su izravno na radili{tu te okolnom podru~ju u krugu 2 km. Buka je mjerena Bruelovom i Kjaerovom opremom s filterom »A« pri razli~itim udaljenostima od helikoptera pri njegovu letu i lebdenju. Promatran je utjecaj buke na radnike (buka na radnom mjestu) i na ostale (buka izvan radnoga mjesta). U prvom je slu~aju najvi{a dopu{tena razina buke Lp = 80 dB(A) s ispravkom temeljne razine 5 dB jer je rad koji obavljaju radnici ve`u}i tovar naporan i zahtijeva visoku koncentraciju. U drugom slu~aju mo`emo govoriti o vrijednosti od 55 dB(A) kao najvi{oj dopu{tenoj razini buke (Konrad i Messingerová 1993).

Ra{~lanjen je utro{ak vremena za pojedine radne zahvate i izra~unati su intervali buke i ti{ine kojima su izlo`eni radnici na tlu. Rezultati prikazani u tablici 6 pokazuju kako su radnici samo kratko vrijeme radnoga ciklusa, dok ve`u i odvezuju teret, izlo`eni prekomjernoj buci.

Na karti intenziteta buke (slika 1) nazna~ena su mjesta vezanja tovara u sastojini (A), na otvorenoj povr{ini (B) i odvezivanja tovara na stovari{tu (C) te je vidljivo da buka samo kratkotrajno prekora~uje dopu{teno ograni~enje.

Buka na radnom mjestu iznad kojega je helikopter iznosi 93 – 100 dB(A). Dopu{tena razina od 80 dB(A) na udaljenosti je od 100 do 200 m u skladu s konfiguracijom terena. Raspodjela buke na razvedenom terenu sa zvu~nim preprekama (iza brda, u gustoj sastojini) druga~ija je nego na otvorenom prostoru (slika 2). Stoga u tom prostoru radnici moraju nositi {titnike za u{i.

Linearni i eksponencijalni model razine buke, dobiven iz rezultata u ovisnosti o udaljenosti i visini helikoptera, odre|en je regresijskom analizom (slika 3 i 4). U tablici 8 prikazane su srednje vrijednosti intenziteta buke pri razli~itim radnim ~imbenicima: udaljenost od helikoptera, visina leta i konfiguracija terena. Konfiguracija je terena razdijeljena na ravni otvoreni teren (1), brdoviti teren (2) i doline izvan linije leta helikoptera (3).

Prednosti izno{enja drva helikopterima vidljive su u mogu}nosti rada na te{ko pristupnim terenima, u visokoj u~inkovitosti na sanitarnim sje~ama, smanjenju o{te}enja tla, dube}ih stabala, one~i{}enja vodotokova i opasnosti od erozija tla.

Klju~ne rije~i: izno{enje drva, helikopter, planinske {ume

Authors' address – Adresa autorâ:

Received (Primljeno): September 13, 2006 Accepted (Prihva}eno): December 4, 2006 Croatian Journal of Forest Engineering 27(2006)2

Assoc. Prof. Valéria Messingerová, PhD. e-mail: messin@vsld.tuzvo.sk Jozef Tajbos, PhD. e-mail: tajbos@vsld.tuzvo.sk Department of Forest exploatation and Mechanization Tehnical University in Zvolen, Faculty of Forestry T. G. Masaryka 24 960 53 Zvolen SLOVAKIA

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Subject review

Current state and development possibilities of wood chip supply chains in Austria Karl Stampfer, Christian Kanzian Abstract – Nacrtak The importance of forest wood chips as fuel for energy production will increase relative to sawmill by-products. The additional production is not a question of potential (harvesting residues, wood from thinning, coppice stands and short rotation forests) but more so a question of economic feasibility. The analyses of different chip production systems resulted in the identification of two major challenges: (1) the design of the chipping and transport interface, and (2) the need to reduce transportation costs.

Chipping and transportation are the key processes for production and can be completed in closed or interrupted work chains. Direct chipping into the transportation machine requires larger operating areas and results in operational delays of the chipper (20% of the total work time) and the truck. In mountainous areas the separation of chipping and transportation can be appropriate and reduce costs by 24–32%.

The increasing fuel demand will result in a larger supply area for the energy producer and lead to increasing transportation costs. An improved utilization of the load volumes can be achieved through drying the material, compressing of harvesting residues as well as higher payloads. Drying wood on storage areas near the forest increases the transportation productivity by 50%. Bundling of harvesting residues pays off especially by larger transportation distances.

Keywords: wood chip supply, chipping, energy wood transport, bundling technology

1. Introduction – Uvod Austria is currently experiencing a boom in the area of woody biomass for energy production. The Green-Energy-Law of 2002, as amended in 2006, caused a planning and building euphoria of energy production capacities. The feed-in tariffs are secured by law and their value is related to the type of renewable resources. In addition to subsidies for energy production from wind and solar and small hydro stations, thermal energy production using bio-fuels is also subsidized. The goal of these laws is to provide 10% of electricity production from renewable resources by 2006, excluding electricity produced by hydropower (Green-Energy-Law – as amended in 2006). An increase ranging between 1.6 and 5.0 million cubic meters is expected in energy wood demands for combined heating plants (CHP) by 2007. The total use of fuel wood in 2000 was 10 million cubic meters and according to some estiCroatian Journal of Forest Engineering 27(2006)2

mates it should be double by 2010 (Katzensteiner and Nemestothy 2006).

Sawmill by-products and residues have been the primary source of energy fuel; however the importance of forest wood chips as a fuel source will increase in future. The reasons lie in decreasing volumes of available sawmill byproducts as well as in attractive subsidy conditions for energy production.

An increase of woody biomass, ranging between 28% and 56% of the total demand of wood resources, is expected in the regions of Lower Austria and Vienna. There are various options as to where this increase should come from. Potential woody material sources include thinning and coppice stands as well as harvesting residues. Additional materials can also come from short rotation forests.

The additional production is not a question of potential but rather of the economic feasibility. Difficult terrain conditions – a large part of Austria’s forest is located on very steep terrain – small harvest

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volumes driven by silvicultural requirements and small farmer-based forest ownership structures result in high production costs (Rohrmoser and Stampfer 2003, Stampfer et al. 1997). The use of information on systems found in Scandinavia (Hakkila 2004) is of limited applicability under these conditions. Systematic comparison for wood chip production systems is available for Scandinavian conditions; for the mountainous area, however, such comparison may only be made on the basis of case studies.

The purpose of this paper is to analyze wood chip production in mountainous areas and to discuss the most important future development challenges.

2. Production Systems â&#x20AC;&#x201C; Sustavi pridobivanja iverja A wood chip production system is a series of various steps, including processing, transportation and decision making, with the goal of converting forestry woody biomass into fuel and providing transport of this resource from the forest to the plant.

Woody biomass can be differentiated as harvest residue and energy wood (Figure 1). Harvest residue (branches, tops and waste wood) is a by-product of

conventional timber harvesting and its advantage is that the extraction costs are covered by roundwood products. The volume of forest residue relative to the volume of timber harvested is very variable. In deciduous stands the biomass component was 6 to 26% of the total harvest (Kanzian et al. 2006). In forest stands dominated by softwoods, Kanzian (2005) determined a range of 10 to 15%. A Finnish study showed the harvest residue in pine and spruce stands to be 20 to 30% in thinning, but only 4 to 5% in the final harvest (Hakkila 2004).

The utilization of harvest residues can result in ecological risks (Krapfenbauer 1983) as well as in poor regeneration (Sterba 2003), as valuable nutrients are removed from the forest. Based on this consideration, 30% of the harvest residue should remain in the stand as a general rule in Finland (Hakkila 2004).

Comparison of energy wood is possible when all materials harvested are used for the purpose of generating thermal energy. The first thinning in both softwood and hardwood stands falls into this category, as well as silvicultural measures in coppice stands.

Efficient biomass production is typically difficult due to small dimensions of wood, but such harvests are often required for improving forest stands.

Fig 1. Forest biomass production systems based on source, location of chipping and type of biomass in transportation Slika 1. Sustavi pridobivanja {umske biomase prema porijeklu, mjestu iveranja i vrsti prevezene biomase 136

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Wood chip production systems are typically organized around the chipping operation. The position of the chipper within the whole system determines the type of biomass to be transported, and whether or not the subsequent machines can work independently of the chipper. Chipping location can be in the forest, at the forest roadside, at a separate central storage area or at the plant. This biomass can be transported in the form of harvesting residues, roundwood, pressed bundles and chips. The resulting load density and transport distance are the factors that will determine success.

Chipping in the forest stand is seldom used in mountainous conditions. In Denmark however this system is often used in thinning and small tree diameter harvests (Talbot and Suadicani 2005). The felling and bunching of trees is carried out by a feller-buncher in the extraction corridors. After being dried for about 20 weeks, the material is chipped with a chipper capable of operating in the stand and transported to the forest road with an integrated container, or with machines carrying separate containers. From there it is transported to the plant with truck containers. Silversides and Sundberg (1989) suggest that the greatest advantage may be realized in chipping of multiple stems simultaneously. In this case the chipper is less susceptible to the negative cost-effects of the »piece-volume-law« (which states that increasing piece size typically results in increased production).

The most common option in the production of woody biomass is chipping at the forest roadside and transportation of chips. About 70% of the annual woody biomass production in Finland is produced in this way (Ranta and Rinne 2006, Junginger et al. 2005). In the largest Central-European combined heating plant in Simmering, Vienna, 50% of the total volume will be delivered as roundwood and 50% as chips. Direct chipping into the truck that is to be used for transportation is widely used. This closed work chain results in the dependence between individual machines. Operational delays can be caused by the chipper waiting for the truck, as well as the truck waiting for the chipper. The challenge from a logistical point of view is to organize the whole process in such a way as to minimize these operational delays.

A further problem in mountainous conditions is the limited space available on forest roads. Loading the truck directly with the chipper requires the machines to be positioned next to one another, so sufficient space is required. One solution is the separation of the work process (interrupted work chain), whereby the machines become independent from one another. However, additional costs occur in the Croatian Journal of Forest Engineering 27(2006)2

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loading of the truck. Another solution is the preconcentration of material to be chipped at a central landing area.

Provision of centralized processing areas close to the forest that can be provided with minimum infrastructure changes makes good sense. This is especially true in mountainous conditions and with small ownership structure of Austria forests. The primary purpose of these centralized storage areas is the concentration of quantities, drying of material and securing a more continuous supply of chips to the energy plants. Larger quantities have a positive effect on both productivity and utilization of the chipper. Drying results in a quality improvement of chips as well as increased utilization of truck volume in transportation. Central landings near to the public road infrastructure also enable the use of non-specialized means of transportation (e.g. semi-trailer configurations with containers) for the transportation of woody biomass. The buffering effect of the centralized processing area is especially important in winter in the mountainous areas. The additional cost of preparing the centralized processing / storage area can be covered by these positive effects.

In Scandinavia the harvest residues are bundled with special machines so as to increase the load density for transportation and to increase productivity when chipping. The bundlers are built on forwarder chassis and work is carried out in the forest stand (Johansson et al. 2006, Kärhä and Vartiamäki 2006, Ranta and Rinne 2006, Cuchet et al. 2004). In mountainous conditions the bundler was designed and built for a truck chassis to work on the forest road (Kanzian 2005). In Scandinavia the wood chip preparation with bundler technology is very common and a viable economic alternative (e.g. 18% of forest wood biomass is produced in this way in Finland), but an Austrian study showed the opposite (Kanzian 2005). The low production level of just 9–13 bundles per PSH15 is however based on a study with an inexperienced operator and partially unorganized preparation of harvesting residues (e.g. impurity of materials, quality of the residue piles).

Scandinavian studies typically achieve higher production ranging between 13 and 26 bundles per PSH15 (Johansson et al. 2006, Kärhä and Vartiamäki 2006).

Different hourly machine rates are significant and they are often just 40–50% of the Central European level (Johansson et al. 2006, Kärhä and Vartiamäki 2006, Ranta and Rinne 2006, Kanzian 2005, Cuchet et al. 2004). Reasons for this lie in a higher level of machine utilization, shorter relocation distances and larger harvest areas. The less than satisfactory machine utilization is a general problem in the production of roundwood and energy-wood in Austria.

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Chipping at the plant makes the chipping and transportation processes independent of one another. The biomass is transported in the form of harvesting residues, whole trees or cut-to-length form.

Low residue load densities are a significant system disadvantage. The use of stationary large scale chippers allows all types of biomass to be chipped at high production rates. This advantage increases with the number of roundwood used, but it is also related to high up-front capital costs (Hakkila 2004).

3. Principle system representation – Osnovni sustavi pridobivanja iverja 3.1 Harvesting Residues – Whole Tree Extraction – Pridobivanje {umskih ostataka pri stablovnoj metodi izradbe Whole tree extraction with a cable yarder or skidder system is carried out on the forest road. The

remaining residues are transported with a timber truck that has been fitted with sides (steel or wood mesh panels). Residues are then taken to an appropriate location where they can be concentrated into large piles. The chipped material is blown directly into a chip truck and transported to the plant (Figure 2). Storage of the harvesting residues and air-drying over the summer months proved to be good. It has been shown by Kanzian et al. (2006) that through summer storage moisture content was reduced from 40–50% to 15–29% and a positive effect was observed on the increased loading capacity.

The advantage of this system is that the felling and extraction costs are associated with the conventional harvest, and therefore they are relatively inexpensive for the biomass. Also when considering forest protection it is reasonable to remove material that is susceptible to bark beetle infestation. Disadvantages are the removal of nutrients, and therefore this system cannot be used in all locations (e.g. forest stands with nutrient deficient soils).

Fig. 2 Utilization of harvesting residues after cable extraction of whole-trees; concentration of materials with timber truck; direct chipping into chip trucks Slika 2. Kori{tenje {umskih ostataka nakon izno{enja stabala `i~arom, skupljanje {umskih ostataka kamionima, neposredno iveranje u kamione za iverje 138

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Fig. 3 Utilization of harvesting residues after fully mechanized harvesting in cut-to-length extraction; direct chipping into chip trucks Slika 3. Kori{tenje {umskih ostataka nakon potpuno mehaniziranoga pridobivanja drva sortimentnom metodom, neposredno iveranje u kamione za iverje 3.2 Harvesting Residues – Cut-to-length extraction – Pridobivanje {umskih ostataka pri sortimentnoj metodi izradbe The remaining harvest residues resulting from harvester felling and forwarder extraction is pulled by the forwarder to the forest road. A truck mounted larger-sized chipper blows the material directly into a chip truck that transports the chips to the power plant (Figure 3).

Since the material is still in the stand, additional costs are incurred for the extraction to the roadside.

The pros and cons with regard to forest protection and nutrient removal are the same as for harvest residues – whole-tree extraction. The system is limited to trafficable terrain.

3.3 Energy Wood – Cut-to-length extraction – Pridobivanje drva za energiju pri sortimentnoj metodi izradbe All material harvested in a thinning operation is converted to wood chips. The felling and processing Croatian Journal of Forest Engineering 27(2006)2

is carried out with a harvester (Figure 4). The logs as well as residues are taken by the forwarder to the processing area at the road-side. After a storage period of one month the material is chipped by use of a tractor-driven chipper. Trucks with roll-off system and roll-on / roll-off containers are loaded directly and finally the chips are transported to the energy plant.

The energy wood production from thinning in small diameter trees is only marginally economic, and in Scandinavia this is subsidized as a silvicultural treatment (Hakkila 2004).

3.4 Energy Wood – Whole Tree Extraction – Pridobivanje drva za energiju pri stablovnoj metodi izradbe All material extracted in a first thinning, mainly small diameter trees, is used to produce woody biomass. A shear-head mounted on a tractor with a trailer fells the trees, and lays them on the forest floor in bunches (where required, the trees are cut again in

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Fig. 4 Utilization of energy wood with harvester and forwarder in cut-to-length extraction; direct chipping into truck with roll-on/roll-off containers Slika 4. Kori{tenje drva za energiju pri sortimentnoj metodi izradbe u sustavu harvester – forvarder, neposredno iveranje u kamione s kontejnerom the middle) and then the trees are loaded directly into the trailer. When fully loaded the material is transported to a road-side processing area and stored for 3–4 months to facilitate drying. A larger sized mobile chipper blows the chips directly into a chipvan, which is then directly transported to the energy station (Figure 5). In Finland they are convinced that felling heads with multi-tree processing function are the only efficient solution for the production of wood chips in small diameter forest (Kärhä et al. 2005, Hakkila 2006), however there is little experience with these machines in Central Europe.

The utilization of small diameter trees is also possible in cable terrain. The felling is carried out with chainsaw and the extraction with the cable yarder.

This system is in most cases not economically viable.

4. Future Challanges – Budu}i izazovi 4.1 Operational delays of the chipper – Prekidi rada ivera~a Empirical studies were carried out to establish chipper productivity in relation to various raw ma-

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terial options as well as to establish the operational delays when chipping directly into waiting chip transporters. In total 118 hours (PSH15) of chipping were recorded and a total of 9246 m3 of chips was produced. The productivity varied between 52 and 111 m3/PSH15 (Figure 6). The highest production was achieved by chipping bundles and roundwood.

Figure 6 also shows the increased potential with reduced operational delays. The chipper spent 20% of the total work time for waiting on the truck. 90% of the waiting times ranged between 9 and 16 minutes, with an average of 12.6 per loaded truck.

4.2 Closed and interrupted work chains – Zatvoreni i prekinuti proizvodni lanac One solution for the reduction of operational delays is the separation of chipping and transportation (interrupted work chain). In this way, the process steps become independent from one another and therefore the space requirement is less, however additional costs occur because of the loading process.

Table 1 shows the comparison of technical data for two chip truck systems. Higher tare weight of the chip truck with loader, in comparison to the conCroatian Journal of Forest Engineering 27(2006)2

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Fig. 5 Utilization of energy wood with shears and tractor trailer in whole-tree extraction; direct chipping into chip trucks Slika 5. Kori{tenje drva za energiju pri stablovnoj metodi izradbe pri radu traktorske ekipa`e sa sje~nom glavom, neposredno iveranje u kamione za iverje

Fig. 6 Chipper productivity in relation to various raw material options with and without operational delays Slika 6. Proizvodnost ivera~a u ovisnosti o razli~itim izvorima drvnoga materijala, s prekidom rada i bez prekida Croatian Journal of Forest Engineering 27(2006)2

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Table 1 Comparison of chip trucks (Kanzian et al. 2006) Tablica 1. Usporedba kamiona za iverje (Kanzian i dr. 2006)

Fig. 7 Costs for various production systems of softwood-tree landing residues Slika 7. Tro{kovi za razli~ite sustave pridobivanja {umskih ostataka drva ~etinja~a 142

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Cuchet, E., Roux, P., Spinelli, R., 2004: Performance of a logging residue bundler in the temperate forests of France.

Biomass and Bioenergy 27(1): 31–39.

Friedl, K., Kanzian, C., Stampfer, K., 2004: Netzwerk Holz.

Forschungsbericht, Institut für Forsttechnik, Universität für Bodenkultur Wien, 1–109.

Hakkila, P., 2004: Developing technology for large-scale production of forest chips – Wood Energy Technology Programme 1999–2003. Research report, VTT Processes, 1–99.

Hakkila, P., 2006: Factors driving the development of forest energy in Finland. Biomass and Bioenergy 30(4): 281–288.

Johansson, J., Liss, J., Gullberg, T., Bjorheden, R., 2006: Transport and handling of forest energy bundles – advantages and problems. Biomass-and-Bioenergy 30(4): 334– 341.

Fig. 8 Productivity in relation to the bulk density of the material transported and the maximum allowable total truck mass Slika 8. Proizvodnost kamiona za iverje u ovisnosti o nasipnoj gusto}i prevezenoga drvnoga materijala i najve}oj dopu{tenoj masi kamiona the required supply area and therefore results in an increase of transportation distances and costs. The utilization of truck capacity must therefore be maximized. Dry woody-biomass can increase the productivity of the truck by 50%. On the basis of this consideration, the introduction of central storage areas makes sense. In addition, these centralized storage areas increase product volume and ensure a more continuous supply, also in the winter months.

Bundling of landing residues is a further possibility to increase the loading density for transportation. In Scandinavia the production systems based on bundling technology are clearly advantageous in longer transportation distances. These systems have not been cost-effectively demonstrated in mountainous conditions. The production levels and calculated hourly rates are clearly different between Scandinavia and Austria. Lower hourly rates result from an increased machine utilization and fewer relocation costs and both of these factors are considerable problems in Central Europe.

Junginger, M., Faaij, A., Bjorheden, R., Turkenburg, W. C., 2005: Technological learning and cost reductions in wood fuel supply chains in Sweden. Biomass-and-Bioenergy 29(6): 399–418.

Kanzian, C., 2005: Bereitstellung von Waldhackgut – Verfahren Energieholzbündel im Gebirge. 1–32. http://www. fpp.at/pics/download/energieholzbuendel_2005_endbe richt.pdf Kanzian, C., Fenz, B., Holzleitner, F., Stampfer, K., 2006: Waldhackgut aus Schlagrücklass – Fallbeispiele im Laubund Nadelholz. 1–29.

Kanzian, C., Holzleitner, F., 2006: Wertschöpfungsketten für Waldhackgut – Einsatz eines selbstladenden Lkw für den Transport. Vortrag im Rahmen: »FORMEC 2006 – 39th International Symposium on Forestry Mechanization« am 25. 09. 2006 in Sofia, Bulgarien.

Kärhä, K., Vartiamäki, T., 2006: Productivity and costs of slash bundling in Nordic conditions. Biomass and Bioenergy 30(12): 1043–1052.

Kärhä, K., Jouhiaho, A., Mutikainen, A., Mattila, S., 2005: Mechanized Energy Wood Harvesting from Early Thinnings. Journal of Forest Engineering 16(1): 15–26.

Katzensteiner, K., Nemestothy, K. P., 2006: Energetische Nutzung von Biomasse aus dem Wald und Bodenschutz – ein Widerspruch? Mitteilungen der Österreichischen Bodenkundlichen Gesellschaft 74: 1–10.

Krapfenbauer, A., 1983: Von der Streunutzung zur Ganzbaumnutzung. Centralblatt für das Gesamte Forstwesen 100(2–3): 143–174.

Ranta, T., Rinne, S., 2006: The profitability of transporting uncomminuted raw materials in Finland. Biomass and Bioenergy 30(3): 231–237.

5. Literature – Literatura Asikainen, A., Ranta, T., Laitila, J., 2001: Large-scale forest fuel procurement. In: Pelkonen, P., Hakkila, P., Karjalainen, T., Schlamadinger, B., Woody Biomass as an Energy Source – Challenges in Europe, European Forest Institute (EFI): 73–78.

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Rohrmoser, C., Stampfer, K., 2003: Optimierung der Bereitstellungskette von Waldhackgut. Forschungsbericht, Österreichische Bundesforste AG – Consulting, Institut für Forsttechnik, 1–96.

Silversides C. R., Sundberg, U., 1989: Operational efficiency in forestry. Vol. 2: practice, 1–169.

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Stampfer, E.; Stampfer, K., Trzesniowski, A., 1997: Rationalisierung der Bereitstellung von Waldhackgut Österr.

Elektrizitätswirtschafts-Aktienges. (Verbundges.), 1–70.

Sterba, H., 2003: Growth after biomass removal during precommercial thinning. In: Limbeck-Lilineau, B., Steinmüller, Th., Stampfer, K. (Hrsg.), »Austro2003: High Tech

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Forest Operations for Mountainous Terrain«, Institute of Forest Engineering, 1–9.

Talbot, B., Suadicani, K., 2005: Analysis of two simulated in-field chipping and extraction systems in spruce thinnings. Biosystems Engineering 91(3): 283–292.

Sa`etak

Sada{nje stanje i mogu}nosti razvoja lanca dobave drvnoga iverja u Austriji Cilj je rada analiza sada{njega stanja pridobivanja drvnoga iverja u Austriji. Zahtjevi za pove}anjem energije znatno pridonose va`nosti {umskoga drvnoga iverja, koji se pridobiva u prvom redu iz {umskih ostataka, drva iz prorednih sje~ina i {uma niskoga uzgojnoga oblika. Pri tome je glavni cilj pridobivanje drvnoga iverja na tro{kovno najisplativiji na~in.

Mjesto iveranja odre|uje vrstu {umske biomase za daljinski prijevoz. Iveranje na {umskoj cesti te daljinski prijevoz iverja naju~estaliji je sustav pridobivanja. Najve}a je proizvodnost ivera~a zabilje`ena pri iveranju obloga drva i sve`njeva {umskih ostataka. Neposredno iveranje u kamione uvjetuje prekide rada ivera~a do 20 % od ukupnoga vremena rada. Tako|er, neposredno iveranje zahtijeva blisko postavljanje ivera~a i kamiona, {to nije uvijek mogu}e u planinskim podru~jima. Zbog navednih se razloga preporu~uje skupljanje i iveranje drvnoga materijala na glavnom stovari{tu, ali se time stvaraju i dodatni tro{kovi.

Ako se iveranje i prijevoz iverja odvijaju neovisno, dodatni se tro{kovi pojavljuju pri utovaru drvnoga iverja, ali se smanjuju prekidi rada uz mogu}nost rada na uskim {umskim cestama s ograni~enim radnim prostorom.

Primjenom ovoga sustava pridobivanja iverja tro{kovi se smanjuju od 24 % do 32 %.

U Austriji se neprestano pove}ava broj bioenergetskih postrojenja, {to pove}ava podru~je dobave iverja te time udaljenost prijevoza iverja i tro{kove. Stoga je potrebno koristiti potpuni kapacitet kamiona. Su{enje {umske biomase mo`e pove}ati proizvodnost kamiona za 50 %. U tom se smislu organizacija glavnog stovari{ta ~ini opravdanom. Tako|er glavno stovari{te osigurava pove}anje proizvedene koli~ine drvnoga iverja i kontinuiranu dobavu iverja u energanu tijekom zimskih mjeseci.

Izradba sve`njeva od drvnih ostataka jedna je od mogu}nosti pove}anja nasipne gusto}e tovara. U Skandinaviji je navedeni sustav pridobivanja najprihvatljiviji pri duljim udaljenostima prijevoza, ali nije tro{kovno isplativ u planinskim uvjetima u Austriji. Razina proizvodnosti i tro{ak strojnoga rada bitno se razlikuju izme|u Skandinavije i Austrije. Manji tro{ak strojnoga rada pove}ava godi{nju iskoristivost stroja te oba ~imbenika ~ine zna~ajni organizacijski problem pridobivanja drvnoga iverja u zemljama sredi{nje Evrope.

Klju~ne rije~i: dobava drvnoga iverja, iveranje, prijevoz drva za energiju, izradba sve`njeva

Authors’ address – Adresa autorâ:

Received (Primljeno): October 16, 2006 Accepted (Prihva}eno): December 4, 2006 Croatian Journal of Forest Engineering 27(2006)2

Assoc. Prof. Karl Stampfer, PhD. karl.stampfer@boku.ac.at Christian Kanzian, MSc. christian.kanzian@boku.ac.at Institute of Forest Engineering Department of Forest and Soil Sciences University of Natural Resources and Applied Life Sciences Vienna Peter Jordan Strasse 82 1190 Vienna AUSTRIA

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Editorial - Uvodnik TIBOR PENTEK At the end of the second (27th) volume ........................................... 67 Na kraju drugoga (dvadesetsedmoga) godi{ta

Original scientific papers - Izvorni znanstveni radovi BO[TJAN KO[IR, @IVKO KO[IR, JANEZ KR^ Natural composition of tree species as a basis for model development of stumpage price ...... 71 Prirodni sastav vrsta drve}a kao osnova razvoja modela cijena drva na panju ANTTI SUVINEN Economic Comparison of the Use of Tyres, Wheel Chains and Bogie Tracks for Timber Extraction .................................................................. 81 Usporedba ekonomi~nosti primjene guma, lanaca i polugusjenica pri izvo`enju drva forvarderom

Preliminary notes – Prethodna priop}enja TAKUYUKI YOSHIOKA, RIN SAKURAI, KAZUHIRO ARUGA, TOSHIO NITAMI, HIDEO SAKAI, HIROSHI KOBAYASHI Comminution of logging residues with a tub grinder: Calculation of productivity and procurement cost of wood chips ........................................... 103 Usitnjavanje otpada pri sje~i i izradbi drva bubnjastim ivera~em: kalkulacija proizvodnosti i tro{ak pridobivanja drvne sje~ke IGOR POTO^NIK Road Traffic in Protected Forest Areas – Case Study in Triglav National Park, Slovenia ..... 115 Cestovni promet u za{ti}enim {umskim podru~jima – studija za Nacionalni park Triglav VALÉRIA MESSINGEROVÁ, JOZEF TAJBO[ Technological and Environmental Parameters of Helicopter Timber Extraction in Slovakia ... 123 Tehnolo{ki i okoli{ni parametri izno{enja drva helikopterima u Slova~koj

Subject review – Pregledni ~lanak KARL STAMPFER, CHRISTIAN KANZIAN Current state and development possibilities of wood chip supply chains in Austria ........ 135 Sada{nje stanje i mogu}nosti razvoja lanca dobave drvnoga iverja u Austriji

ISSN 1845-5719

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