Impact of the ditches to ecological functionality of bogs Ain Kull J. Paal, M. Kohv, A. L채채nelaid, K. Sohar, G. Veber, T. Tampuu, J.-O. Salm, V. Kuusemets, A. Liivam채gi, A. Kull
University of Tartu Institute of Ecology and Earth Sciences Ain.Kull@ut.ee
Introduction • Inventory of Estonian mire habitats indicates that: – peatlands cover more than 22% (1,009,101 ha) of Estonian area, – area of mires nowadays forms up to 245,000 ha or 5.5% • The main threat to Estonian mires has come over the centuries from drainage. Total area of mires has decreased nearly 2.8 times (662,000 ha) since intensive drainage started in 1950s. • In Estonia about 338,400 ha has been ameliorated (mainly drained) for forestry and 584,400 ha for agriculture.
Some examples of drainage types of peatland areas
•
Loss of mires occurred mainly on account of minerotrophic and mixotrophic mires.
•
Large-scale amelioration is not a considerable threat any more in Estonia while silviculture and peat industry requires still close attention and wise planning.
•
To assess long term effect of drainage on mire ecosystems an extensive nation-wide research project was initiated in Estonia in 2012.
Objectives The main objective of the study is to clarify to what extent the drainage influence mire ecosystem structure and functions. We aim to quantify long-term drainage effects on mires and to study what is the spatial extent and intensity of the drainage influence on particular biotic or abiotic components based on landscape ecological parameters and integral indicators: * water level, physical and chemical properties; * peat physical and chemical properties, infiltration rate; * emissions of greenhouse gases; * vegetation pattern and growth parameters of trees; * insectifauna composition and distribution
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Location of study areas
Study areas I group: old overgrown ditch across the bog dug only into peat layer • Maarjapeakse: ombrotrophic bog • Ullika: treed ombrotrophic bog • Kauru-E: ombrotrophic bog
Study areas II group: silvicultural intensively draining ditch cut through bog peatlayer • Tellissaare • Vedelsoo • Selisoo
Study areas III group: hollow-ridge-pool bog with deep intensively draining double ditches • Laukasoo peat extraction area • Umbusi peat extraction area
Study areas IV group: mixotrophic bogs • • • • •
Tuhu E Tuhu W Tuudi Hindaste Kassisaare
Study areas V group: deep intensively draining marginal cutoff ditch at bog margin • Allipa • Essaku • Mõksi
● ● ●
Koordi Kauru W Musa
Study transect and sampling areas layout with nodes and sampling plots along the sub-transects. Distance increment order: 0 – 5 – 10 – 25 – 50 – 100 – 250 – 250 m.
water level:
Water table (cm) from ground
In mires it is all about water ...
Tellissaare
20.0 0.0 -20.0
0
5
15
40
90
190
440
-40.0 -60.0 -80.0 -100.0 -120.0 -140.0 Min
Mean
manually in water sampling wells (1 per month) automatic piesometers (24 h) water properties: pH, t째, ORP, EC, O2, soil t째 water chemistry (NO3, NO2, Ntot, PO4, Ptot, Ca, K, Mg, DOC, DIC, DC) Water table dynamics and pressure level
Max
718
Peat properties • Peat deposit mapping by georadar. • Peat coring incl. peat sampling: – peat type – decomposition rate, – bulk density, – C-content
• In situ infiltration measurements in each sampling point by 30 cm layers throughout the peat profile.
Georadar profile Sphagnum peats Wooded peats Phragmites, carex etc peats
Moraine Sand Gyttja Ash, carbon
Surface subsidience: mineralization and compaction
Surface subsidience: mineralization and compaction m
m
m
m
Water flow: 2 extreme cases
Maarjapeakse, old overgrown ditch
Umbusi, intensively drained peat extraction area
Surface water flow direction determined based on highresolution LIDAR elevation data by 8 point of the compass
Changes in landscape structure
Pore water properties
Dependency of peat water dissolved O2 and dry matter content on log-distance from the cutoff ditch shows similar result.
With the minimal water level, the logdistance from the cutoff ditch is correlated modestly (rSpearman=0.41) and the drawdown effect of the cutoff ditch subsides about at the 310 meters.
Nitrogen availability
Maarjapeakse, old overgrown ditch
Umbusi, intensive drainage
Changes in tree height and cover in bogs 9
Puude keskmine k천rgus (m) (m) Mean tree height
8
Tellissaare
7
Vedelsoo
6
Selisoo
5
Keskmine
4 3 2 1 0 0
50
0.6
100
150
200
250
300
Puude keskmine v천rakatvus (m2/m2) Mean projected tree canopy cover (m2/m2)
0.5
350
400
Tellissaare Vedelsoo Selisoo
0.4
Keskmine
0.3 0.2 0.1 0 0
100
200
300
Main changes: increased number, density, canopy cover and height
400
Changes in tree height and canopy cover in mixotrophic mires
Main changes: increased number of saplings, canopy cover and height
Dendrological study Integral indicator, reflecting dynamics of drainage effect by expressing response to the change of water regime (quick response in annual growth increment) and consequent long term effect due to increased mineralization (slow steady increase in growth increment) Dendrological analysis is prolonged along the transect toward the mineral soils to consider local regional effects.
Umbusi and Laukasoo (peat extraction area) Umbusi mändide juurdekasv 10-yr before and 10 a. enne ja 20 a. 20-yr pärastafter 1966.drainage aastat
Umbusibog, mändide juurdekasv 7 postis Umbusi radial increment 1.5 Mediaan radiaaljuurdekasv [mm]
Radiaaljuurdekasv [mm]
3 2.5 2
1966
1.5 1 0.5
10 aastat enne 1966
0.5
0 1870 Post 1
1890 Post 2
1910 Post 3
1930year1950 Aastad Post 4
1970 Post 5
1990 Post 6
Hindaste mändide juurdekasv 7 postis Hindaste mire, radial increment
50
100
150
200
250
300
350
400
Distance Kaugus from kraavistditch [m] (m)
Post 7
Hindaste mändide juurdekasv 10 a. before enne jaand 20 pärast 1965. aastat 10-yr 10-yr before anda.20-yr 20-yr after after drainage drainage 2.5 Mediaan radiaaljuurdekasv [mm]
Radiaaljuurdekasv [mm]
0 0
2010
5 4
1965 1976
3 2 1 0
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Post 1
20 aastat pärast 1966
1
Post 2
Post 3
Aastad Post 4
Post 5
Post 6
Post 7
10 aastat enne 1965 2
20 aastat pärast 1965
1.5 1 0.5 0 0
50 100 150 200 250 300 350 400 450 500 550 600 650 700 750
Distance Distance from ditch from ditch (m) Kaugus kraavist [m] (m)
Greenhouse gases fluxes Field data on fluxes of CO2, CH4 and N2O are collected monthly since June 2012 using the closed chamber method in 3 replicates per measurement site following the gaschromatograph analysis. CO2, CH4 and N2O emissions and CH4/CO2/N2O ratio are the integral indicators reflecting water level change and concurrent mineralization (N2O), change in pH and vegetation
250.0 Tuhu 1 CO2-C (mg C m-2 h-1)
Tuhu 2 CO2-C (mg C m-2 h-1)
350.0 Tuhu 3 CO2-C (mg C m-2 h-1)
300.0 Tuhu 4 CO2-C (mg C m-2 h-1)
Tuhu 5 CO2-C (mg C m-2 h-1)
50.0
0.0
35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0 -5.0 20 1 20 2 J 20 12 uuli 12 Au Se gu 20 pte st m 12 b 20 Ok er 12 too be 20 No r 12 ve m D et b er 20 sem 13 be r 20 Ja 13 anu Ve a r e 20 bru 13 ar M 20 ärt 13 s A 20 prill 13 20 Ma 13 i J 20 uun i 1 20 3 J u 1 u 20 3 13 Au li Se gu 20 pte st m 13 b 20 Ok er 13 too b N o v er em be r
400.0
20 1 20 2 Ju ul 20 12 Au i 12 Se gu st 20 pte m 12 b 20 Ok er 12 too be 20 No r v 12 em D et ber 20 sem 13 be 20 Jaa r 13 nu Ve ar e 20 bru 13 ar M 20 ärts 13 Ap ri 20 13 ll 20 Ma i 13 Ju u 20 13 ni 20 Ju u 20 13 Au li 13 Se gu st 20 pte m 13 be r 20 Okt oo 13 b N ov er em be r
20 1 20 2 J 20 12 uul i 12 A Se u gu s 20 pte t 12 m be O 20 r k 12 too 20 No b er 12 ve D mb et e 20 sem r 13 be r 20 Ja 13 an u Ve ar e 20 bru 13 ar M 20 ärt 13 s A 20 p ril 13 l 20 M 13 ai J 20 uun 13 i 20 J 20 13 uul i 13 A Se ugu 20 pte st 13 m b 20 Ok er 13 too b N ov er em be r
Annual dynamics of GHG emissions 12000 Tuhu 1 CH4-C (µg C m-2 h-1)
10000 Tuhu 3 CH4-C (µg C m-2 h-1)
8000 Tuhu 4 CH4-C (µg C m-2 h-1)
200.0 6000
150.0 4000
100.0 2000
Tuhu 2 CH4-C (µg C m-2 h-1)
Tuhu 5 CH4-C (µg C m-2 h-1)
0
Tuhu 1 N2O-N (µg N m-2 h-1)
Tuhu 2 N2O-N (µg N m-2 h-1)
Tuhu 3 N2O-N (µg N m-2 h-1)
Tuhu 4 N2O-N (µg N m-2 h-1)
Tuhu 5 N2O-N (µg N m-2 h-1)
CO2 emission 60 40
Maarjapeakse
20 0 -20
0
5
15
40
90
190
440
-40 -60 CO2-C (mg C m-2 h-1) 80 60 40 20 0 -20 -40 -60 -80 -100
0
10
16
26
CO2-C (mg C m-2 h-1)
Kesk_Veetase (cm)
51
101
201
365
Kesk_Veetase
Umbusi
CH4 emission in transitional bogs Kassisaare
30000
35.0
25000 20000
30.0
Tuhu 2
20000
0.0 -10.0
15000
-20.0
10000
15000 10000
25.0
5000 0 190
440
2000 1000 0 0
5 15 40 CH4-C (µg C m-2 h-1)
90
190
440 C/N
-60.0 0
5
15
40
90
CH4-C (µg C m-2 h-1)
29 27 25 23 21 19 17 15
3000
-50.0
0
690 C/N
Tuhu 1
4000
-40.0
5000
20.0 15 25 35 90 CH4-C (µg C m-2 h-1)
-30.0
7000 6000 5000 4000 3000 2000 1000 0 -1000
190
Kesk_Veetase
Tuudi
0
5
15
CH4-C (µg C m-2 h-1)
40
90
190
440 C/N
Water table level affects methane emission more than 10x, C/N ratio is important
55 50 45 40 35 30 25 20 15
N2O emission in transitional bogs Hindaste
50.0
3.00
40.0
2.80
30.0
2.60
20.0 2.40
10.0
2.20
0.0 15
-10.0
25
35
90
190
N2O-N (µg N m-2 h-1)
440
690
4 3 2.5 2 1.5 1
5
15
40
N2O-N (µg N m-2 h-1)
90
190
440
N%_muld
0
5
15
40
3 90
190
340
2.5 2 1.5 1 0.5 N2O-N (µg N m-2 h-1)
3.5
0
Kassisaare
-0.4 -0.5 -0.6 -0.7 -0.8
N%_muld
Tuhu 1
8 7 6 5 4 3 2 1 0
2.00
0 -0.1 -0.2 -0.3
N%_muld
Tuhu 2
1.5
3 2.5
1
2
0.5
1.5 0 -0.5
0
5
15
40
90
190
1 0.5
-1
0 N2O-N (µg N m-2 h-1)
N%_muld
Flux of N2O has high temporal variability, higher in case of fluctuating water table. Stable high water level suppress N 2O emission.
Change of GHG in intensively drained bog in relation to the distance from cutoff ditch 120.0 100.0 80.0 60.0 40.0 20.0 0.0 -20.0 -40.0 -60.0 -80.0
Laukasoo
Laukasoo
7.0
3.00
6.0
2.50
5.0 2.00
4.0 3.0
1.50
2.0
3
13
28
38
50
75
125
1.00
1.0 0.50
0.0 -1.0
3
13
Mean water level Kesk_Veetase
CO2-C (mg C m-2 h-1)
28
100.00 90.00 80.00 70.00 60.00 50.00 40.00 30.00 20.00 10.00 0.00
7000.0 6000.0 5000.0 4000.0 3000.0 2000.0 1000.0 0.0 3
13
28
CH4-C (Âľg C m-2 h-1)
38
50
75
125 C/N
50
75
125
0.00
N-tot % in soil N%_muld
N2O-N (Âľg N m-2 h-1)
Laukasoo
8000.0
38
Geobotanical analysis • In each sampling area vegetation releves in 2 replications (1 x 4 m) • Number and height of bush stems (4 replications, on sample quadrates of 2 m diameter) • Height and diameter of trees within 2 m wide and 28 m long strip across the transect
DCA ordination biplot of raised bog species and main environmental variables.
The most principal variables determining the vegetation structure and environmental conditions demonstrate a striking gradient driven by minimal water level in peat layer and by variables tightly correlated with it (dry matter content and total-N content in soil). DCA biplot of sampling areas, main variables determining the vegetation structure and environmental conditions.
Dependency of different vegetation layers coverage on minimal water level.
Where the minimal water level is higher than -50 cm, a rapid increase of Sphagnum spp. and moss layer coverage is induced.
Insectifaunistic diversity • Insects are studied as an indicator of biological diversity. Species richness of insects depends on vegetation/water level but also management of the surrounding area (peat extraction dust, pesticides, fertilizers, forest management) • In each sampling area scoopnet catch of insects (100 strikes) across the transect is carried out. • Trap catch. In each sampling point ground trap and vegetation level traps are applied. • Malaysese trap
Change of the invertebrates number in relation to the distance from cutoff ditch
Malaysese trap
Ground trap Ă˜ = 5 cm
Scoopnet 100 strikes
Agonum ericeti
Canopy cover, m2/m2
Insectifauna 300
0,7
Araneae (spiders) ämblikulised
250
0,6
katvus
0,4 150
katvus
arvukus
0,5
canopy cover
200
Clear correlation with vegetation and thereby by water level
0,3 100 0,2
50
0,1
0 0
100
200
300
400
500
600
700
400
0 800
50 sipelglased
Formicidae (ants)
350
45
min veetase
40
250 arvukus
35
Min water level
30
200
25 20
150
15 100 10 50
5
0 0
100
200
300
400
500
600
700
0 800
min veetase maapinnast
300
Main factors affecting insectifauna: •min. water level •tree height •canopy cover •mosses •grasses
New species found:
Conclusions • Landscape ecological indicators have different sensitivity and shows different width of drainage affected zone but the zone can be quantitatively distinguished. • Depth of drainage system is an important but not the decisive factor. • The simplest indicators are the minimum water level and from vegetation parameters the mean tree height and canopy cover. According to preliminary estimates: most sensitive parameters are affected up to 400m from the ditch; significant impact of drainage on all parameters can be observed at least 100m distance; most parameters are affected up to distance of 200m.
Conclusions * Variation of vegetation in mixotrophic bogs is remarkable larger than in ombrotrophic bogs, * the main factors affecting the species richness of same vegetation layers in mixotrophic and ombrotrophic bogs are usually different, * in mixotrophic bogs the impact of cutoff drainage ditch on vegetation structure (species content and abundance proportions) extends up to 300-400 m towards bog undrained central area, * in raised bogs the impact of cutoff drainage ditch on vegetation structure extends at least up to 200 m towards bog undrained central area.