Forestry bulletin no 16 silviculture of slash pine by Greg Bailey

BULLETIN 16

APRIL, 1968

SILVICULTURE OF SLASH PINE (Fourth of a Series on the Silviculture of Southern Forests)

LAURENCE C. WALKER

and HARRY V. WIANT, JR.

Stephen F. Austin State College SCHOOL OF FORESTRY NACOGDOCHES, TEXAS

STEPHEN F. AUSTIN STATE COLLEGE SCHOOL OF FORESTRY FACULTY Dean of School and Professor of Forestry Professor of ROBERT D. BAKER, Ph.D. Forestry Professor of Forestry M. VICTOR BILAN, D.F. Professor of Forestry NELSON T. SAMSON, Ph.D. Professor of Forestry ARTHUR VERRALL, Ph.D. Visiting Professor BILL HOWARD WILFORD, Ph.D. of Forestry Associate Professor of LEONARD BURKART, Ph.D. Forestry Associate Professor of HARRY V. WIANT, JR., Ph.D. Forestry Assistant Professor of EUGENE HASTINGS, Ph.D. Forestry Assistant Professor of ELLIS V. HUNT, JR., M.S. Forestry DAVID LENHART, Ph.D. Assistant Professor of Forestry THOMAS MCGRATH, Ph.D. Assistant Professor of Forestry Assistant Professor of J. ROBERT SINGER, Sc.D. Forestry D. Assistant Professor KENNETH G. WATTERSTON, Ph, of Forestry Instructor CARLTON S. YEE, M.F. Part-Time Instructor LOWELL K. HALLS, M.S. Part-Time Instructor JOHN J. STRANSKY, M.S. Research Technologist K. KADAMBI, Ph.D., Sc.D. Forestry Librarian MARY Jo LINTHICUM, B.S. Editor, GEORGE STEPHENSON, M.F. Forestry Publications LAURENCE C. WALKER, Ph.D.

BULLETIN 16

APRIL, 1968

139967

BULLETIN 16

APRIL, 1968 Price $1.00

SILVICULTURE OF SLASH PINE

LAURENCE C. WALKER and HARRY V. WIANT, JR.

Sponsored by the Conservation Foundation (A preface to this series is given in the first issued. Silviculture of Shortleaf Pine, S.F.A. Bui. No. 9.)

Stephen F. Austin State College SCHOOL OF FORESTRY NACOGDOCHES, TEXAS

TABLE OF CONTENTS

Silviculture of Slash Pine Distribution

5 5

Climatic Effect South Florida Slash Pine

6 6

Growth

Seasonal Growth Drought Effects Species Comparisons

ÂŤ

Site Index

Site Quality

Reproduction Establishment Natural

17 17

Drainage Flowers and Seeds Flower Development Seed Production Cone-Counting

Sprouting

Planting (Other than Sandhills and South Florida Slash Pine)

8 10 10

19 21 *.

21 21 23

Drainage Fertilization Site Potential

26 27 31

Spacing Summer Planting Cultivation

32 37 37

Planting (Sandhills)

Site Preparation Roots and Soil

Planting (South Florida Slash Pine) Old-Field vs. Cutover Forest

Direct Seeding Seed Grades

Tree Improvement Genetics

39 42

43 44

45 47

47 47

Inheritance

Vegetative Propagation

Cuttings Air Layering Grafting Rooting Dwarf Shoots

52 53 53 56

Sexual Propagation Injurious Agents in Seed Orchards Bark Beetle Thrips Worms Cone Rust

HRHRT STEPHEN F. AUSTIN STATE COLLEGE

57 57 57 59 59 59

Intermediate Management

Thinning

Density Crowns Basal Area Fusiform Rust Pre-commereial Thinning

60 61 62 63 64

Pruning

Bud Pruning

Fire Pruning

Undesirable Species Control Prescribed Burning Endurance

67 67 ,

Technique Other Effects

69 69

Integrated Management

Gum Naval Stores

Silvicultural Relations

Growth and Yields Acid Effect Methods Fusarium Lateritium

70 72 74 74

2,4-D and Fertilizer Black Turpentine Beetles Dry F'ace

Range Management Prescribed Burning Cattle Repellent South Florida Slash Pine Hogs

Destructive Agents Diseases Fusiform Rust Cycle

Fomes Annosus Evidence Control

Black Root Rot Red Root and Butt Rot Atropellis Tingens Pitch Canker Needle Casts

Insects Reproduction Weevils Moths Crickets Black and Red Turpentine Beetles Control

74 75 76

76 78 78 78 79

80 80 80 82

82 84 85

86 86 86 87 87

87 87 87 88 89 92

Town Ants Cone Insects Nematodes

Rodents Storms Ice .. Wind

Literature Cited Appendix

92 92 92

93 93 93 94

95 113

Silviculture of Slash Pine

SILVICULTURE OF SLASH PINE Distribution Slash pine 12 is found naturally in the drainages of Coastal Plain longleaf pine forests east of the Mississippi Eiver; in the moderately drained flatwoods of the Southeast; and in sandy soils of the middle Coastal Plain. As a rule, the range is limited to within 125 miles of salt water. Exceptions include the high, relatively dry hill land of south Georgia. The type spreads because of the species' frequent and abundant seed production, rapid growth, relative tolerance to shade in contrast to longleaf pine after the grass stage, ability to withstand hogs and fire once beyond the sapling stage, and adaptability to a wide range of site and environmental conditions. The unusual ability for planted seedlings to survive and become established also favors its spread. Because of successful artificial regeneration, the range has been expanded to include East Texas and the Piedmont province of Georgia and South Carolina. Thus, as Bennett (1963) pointed out, slash pine, with the most limited natural range of the major southern pines, has been planted more than any other timber species in North America. Slash pine stands inhabit creek drainages principally because seed sources have been available at just the timeâ&#x20AC;&#x201D;during severe droughtsâ&#x20AC;&#x201D; when burning took place, perhaps one in 15 or 20 years. For the same reason, it replaces longleaf pine in poorly drained sandy flatwoods. In the middle Coastal Plain, slash pine aggressively crowds out the less active longleaf pine. A 2:1 ratio of longleaf pine to slash pine has been reduced to a 1:1 ratio during a 10-year period without purposeful discrimination against the former. Slash pine often occurs in dense patches at the edges of swamps, ponds, and bays for a distance of 25 to 200 feet or until the species gives way to the more fire-resistant longleaf pine on higher and.drier ground. With continued improvement in fire protection, slash pine forests are expected to increase at the expense of longleaf pine. [Gansel (1967) found no evidence that the invasion of slash pine onto dry sites has produced wet- and drysite ecotypes.] Sonderegger pine is probably unsuited as a replacement for slash pine on fine sands of the southeastern flatwoods. On these sites, Hoekstra (1957) considers loblolly pine satisfactory, but inferior to slash pine. In zones with few hardwoods, pure slash pine is a more or less permanent type, for it can reproduce under a canopy. Frequently, however, hardwoods invade and, unless controlled, replace slash pine. Less likely to have hardwood associates than most southern pines, slash pine-hardwood types are found on moist sites, principally where swamp and black tupelo and red maple are prominent. As encroachment of deciduous trees gains momentum following cutting, coniferous regeneration is eventually excluded. On very wet sites, slash pine-swamp tupelo, slash pine-cabbage palmetto, and slash pine-loblolly pine subclimax types occur. 'Pomeroy and Cooper (1956) authored a Farmers Bulletin on this species. Silvical characteristics are reviewed in Agr. Handbook No. 271 (USFS, 1965). ^Scientific names of species mentioned are Driven in the Appendix.

Stephen F. Austin State College Climatic Effect

The natural distribution of slash pine is related to climatic conditions. Rainfall frequency in summer amounts to 4.05 days per month inside the range in contrast to 3.35 in adjoining areas outside the range. Bethune (1960) believes the occurrence of the species may be associated with the frequency of heavy rains which effectively replenish soil moisture during the growing season. Years of infrequent summer rains result in poor firstyear survival, and inadequate soil moisture during the growing season may limit flower bud formation and retard development of cones and seed. On the other hand, winter rains occur more frequently in areas just outside than within the natural range. That is noteworthy, as heavy rains in late winter can inhibit or even prevent pollination of flowers (Fig. 1). In south Florida, within the range of the South Florida slash pine variety, almost threefourths of the rain occurs in summer. Water tables there are low in late winter, quite in contrast to the situation elsewhere.

WIUTFB\ WINTtR M

OUTSIDE NATURAL RANGF--

FREQUENCY OF PRECIPITATION (DAYS PER MONTH)

Figure 1â&#x20AC;&#x201D;Average temperature and frequency of precipitation within the natural range of slash pine and immediately outside of the range (from Bethune, 1960). South Florida Slash Pine

Little and Dorman (1954) distinguished South Florida slash pine as a separate variety. This variety ranges in southern and south central Florida and along both coasts in the north central

Silviculture of Slash Pine

part of the state (Langdon, 1963a). Bethune and Langdon (1966) found seedlings from a northerly source had morphological characteristics more closely resembling typical slash pine than those from a southerly source. Until recently, little attention was given to silvical differences between the variety and the typical species, or even to which was being used in reforestation. South Florida slash pine once grew in pure evenaged stands on more than 2 million acres (Fig. 2).

Figure 2â&#x20AC;&#x201D;A virgin stand of South Florida slash pine. The unevenaged stand contains trees from 70 to 140 years old. Average dbh is 12 inches.

Now it is found mostly in poorly stocked stands or lands otherwise denuded because of wildfire, overcutting, and livestock farming. Bethune (1966) concluded that South Florida slash pine planted in South Florida was more resistant to fire (thicker bark), insects and diseases (except brown spot), and cattle damage than typical slash pine. However, the typical species survived better, made better early growth, and was more resistant to wind damage. Growth

On an average old-field site (index 65, 25-year basis), planted slash pine will grow about 3 feet annually for the first 15 years.

Stephen F. Austin State College

Growth is one-half to three-quarters of a foot the first year, about 2 feet the second, and 3 feet the third year; then, for a period, as much as 4 feet per year may occur. During the 20- to 25-year period, growth will average about 1.5 feet. Little effective height growth is expected after age 35 (Bennett, 1965). Growth of slash pine on land of SI 90 may exceed 2 cords per acre annually at age 15, declining to about 1.3 cords, or 500 board feet, at age 60 (Forbes, 1955). A plantation in central Louisiana produced 50.6 rough cords per acre at age 26*/2 years (So. For. Exp. Sta., 1962). Chappelle (1962) developed financial maturity guides for some slash pine stands in the middle coastal plain of Georgia. He found merchantable cubic-foot volume growth increased as dbh, crown ratio, and crown class increased; the value growth rate, however, decreased as average stand dbh increased. Mattoon (1940) scaled a 21-year-old slash pine stand at 10 MBM (Int.) or 3.7 MBM (Doyle), a 25-year-old stand at 14 (Int.) and 6 (Doyle) MBM, and a 50-year-old stand of 220 trees per acre at 15 (Int.) or 6 (Doyle) MBM on good sites. Lehocky and Lee (1954) noted that on old-fields adjacent to the Sandhills, basal area of a slash pine plantation was 127 square feet at 16 years of age. The stand contained 32 cords, and the average tree was over 5 inches dbh. Seasonal Growth Height growth for slash pine in lower Mississippi begins between March 1 and 15, is more than half through by May 1, and is 90 percent complete by July 1 (Smith, I960),. The average growing season there is 152 days. In the Georgia Coastal Plain, 20 percent of the height growth occurs in March, 40 percent in April, and from then on constantly decreases until growth ceases in winter (Bennett, 1956). Records from the second, third, and fourth growing seasons showed that 25 percent of the height growth of young slash pine is completed by the end of March, 52 percent by the end of April, 85 percent by the end of June, and 95 percent by mid-August. About 1 percent of the total growth occurs in October (Bennett, 1963). Kaufman (1965) charted the seasonal growth of young slash pine trees on SI 70 land (25-year basis) in Florida (Fig. 3). Many 1-year-old trees make twice the height growth in the month from mid-October to mid-November as they do in the 4l/2 months prior to midOctober in the southeastern flatwoods. Subsequent tallies showed that complete dormancy never occurs, as some height growth takes place even in February (Walker, Green, and Daniels, 1961). Slash pine has been grown until frost by exposure to long photoperiods (Kramer, 1943) (Fig. 4).

AVERAGE

a* <: w

§ I

o sr W o

so S' S. c- o *1

"3 W o

2. •a3 ^2 5, g ^ so

3. 3M (-1. M ,__! O

3 S5 £•

ag« e "rt §' 3 g &• 3

3 g o <B ct 4

|*t§: !1

N. e.

U. HI w

i-flo a. 3' | 2 ^ O o 3. -1

»• 09

?f g'l

r S. o 2 s H»

3^ 3§

ct & sr

o »• 2

II »• 3

Ul O

1 01 * §

/•^ s

INCHES

0 03 5 rere p

« o.

DAILY GROWTH

HEIGHT GROWTH (IN.)

w «• S

3 ? £? 3 5" h-> P

50 "1

*- -O co

Stephen F. Austin State College Drought Effects

Severe droughts appreciably affect growth of slash pine. In the Georgia Coastal Plain, as a result of rainfall 56 percent of normal, increment was 42 percent of normal. The influence, according to Hey ward (1959), was felt again the next year when growth was still only one-half of normal, though rainfall was 73 percent of its average. The width of latewood—important because of its relation to wood strength—is affected by late season rainfall (Foil, 1961). In southern Louisiana, the width of the band is strongly associated with soil moisture during October and, less strongly, with soil moisture from July through September. That relationship seems atypical, for soil moisture is generally lowest in late summer and early fall and this moisture stress, combined with shortening photoperiods, may be a factor in advancing dormancy prematurely. Species Comparisons Slash pine generally grows faster than longleaf pine for the first 25 years, and equals longleaf pine in 35 years on most sites. In contrast to longleaf pine, slash pine has an increasing range in diameter with advancing age, depending upon site. Slash pine diameter growth in old-growth forests is as much as 40 percent better than loblolly pine at 20 years of age, but only 24 percent better at 50 years on highest quality land. On lesser sites, growth is about equal (Mattoon, 1916). On well-drained sandy loam soils in central Louisiana, slash pine is inferior to loblolly pine, but not on poorly drained sites (Mann, 1953; Muntz, 1948a). In the flatwoods of the southeastern Coastal Plain, characterized by poorly drained fine sands underlain by a hardpan, slash pine is superior to both loblolly and Sonderegger pines in the sapling stage (Hoekstra, 1957). In Alabama plantations of the major southern pines at Auburn, slash pine, except on moist sites, outgrew and out-produced loblolly pine, its closest competitor, over a period of at least 36 years (Livingston, 1964). A state-wide survey in the same state showed no significant difference in annual diameter growth of loblolly and slash pines. However, slash pine grew significantly better than shortleaf pine (Judson, 1965). In the eroded loess soils of north Mississippi, slash pine generally has poorer survival than loblolly pine, but growth is equal—6 feet in 5 years where released. Growth is faster for slash pine than for shortleaf pine in that zone. While slash pine survival is improved by release the first year, the unusual lack of uniformity provides an early expression of dominance, and suppression of many stems is notable (Broadfoot, 1951; Williston and Huckenpahler, 1958). A slash pine plantation averaged 2 inches dbh and 20 feet height growth in the 10-year period beginning at age 20 (Williston, 1959). Loblolly and shortleaf pines are somewhat inferior, and longleaf and Monterey pines are much poorer than slash pine in the west Florida Sand-

Silviculture of Slash Pine

hills. Sand pine makes comparably good growth, but survival is erratic, while Virginia pine is characterized by good survival, though poorer growth (Scheer, 1959). Slash pine grew three times as fast as North Carolina pond pine when planted on wet sites in southern Mississippi. However, pond pine survived better than slash in these 7-year-old plantings (Allen and Scarbrough, 1960). Site Index

The average site index for the Coastal Plain in South Carolina and Georgia is about 70. For Florida, it is 62 (Cruikshank, 1954). Coile (1952) states that most natural stands fall in the SI 80 to 90 class, while Bennett (1953) finds slash pine in the uplands of the Coastal Plain of Georgia averages SI 74, ranging from SI 69 to 80. The wide range is due to soil drainage. Where internal and external drainage is very slow, site index varies from 76 to 90, and averages 83. The greater growth potential here than in the uplands is attributed to the greater amount of water available during droughts and to the greater depth of the A horizon to retain that water in available form. Thus, drainages are the best sites for slash pine, and there the slower-growing longleaf pine will rarely invade. For all sites, slash pine is 9 to 15 site index units higher than longleaf pine. Indexes for slash pine on badly gullied sites are 30 units lower than on uneroded sites (Kittredge, 1952). Standard growth curves (Fig. 5) for natural slash pine are 1 10

X 100

100 90 80 o c

'i o

â&#x20AC;˘o -C.

o> ffi

50 40 30 ?c\

X 90

Z ^^> / </,2/^ ^ /)/ K^ /

o IT)

r/ '

age-years

SLASH Figure 5â&#x20AC;&#x201D;Site index curves for natural slash pine (from Anonymous, 1929).

Stephen F. Austin State College

adequate for the flatwoods of northeastern Florida. Cobb (1957) notes, however, that those curves may slightly overestimate heights for 15- to 30-year-old stands, and McGee and Clutter (1967) question assumptions commonly made in construction of site index curves. The site index for slash pine generally rises with increasing amounts of silt and clay in the subsoil. Coile (1952) found the range to be from SI 75 for sands and loamy sand to SI 90 for silty clays and other fine-textured classes. Thus, site productivity can be estimated on the basis of subsoil texture, as most sites in which the species grows are too level for accelerated erosion and, therefore, have sufficient surface soil for normal growth (Table 1). Turpentined trees have slightly lower apparent site indexâ&#x20AC;&#x201D; about 2 units. TABLE 1. RELATION OF SOIL PROPERTIES TO SITE INDEX OF SLASH PINE (from Coile, 1952) Texture of subsoil

Sands and loamy sands Sandy loam and sandy clay loam Loam, clay loam, sandy clay, and light clay Silty clay, heavy clay, silty clay loam, and silt loam

Site index

75 80 85 90

Site index for flatwoods slash pine is somewhat greater than at higher elevations. There are exceptions, usually due to the presence of either a hardpan or deep, excessively drained sands, on which slash pine may not exceed half the growth it makes on imperfectly drained sandy loams in the upper Coastal Plain. In south Alabama, muck or peat topsoils, or soils with mottling in the surface horizon, generally produce poorer slash pine than that indicated in Table 1 (Hodgkins, 1956). Site Quality

The site quality curves of Figure 6 for old-field plantations are applicable for the middle Coastal Plain of Georgia and the Carolina Sandhills. They are reasonably accurate throughout the balance of the Coastal Plain (McGee and Bennett, 1959; Bennett, McGee, and Clutter, 1959). Where trees are absent, site quality determinations are based on the thickness of the Al horizon and the depth to fine-textured soil (B2) (McGee, 1961) (Tables 2 and 3).

Silviculture of Slash Pine

=> o Ld H C/>

10 10

AGE

Figure 6—Site quality curves for old-field slash pine plantations for the middle Coastal Plain of Georgia and the South Carolina Sandhills. Age refers to years since planting and not from seed (from McGee and Bennett, 1959). TABLE 2. SITE QUALITY (TOTAL HFJGHT AT AGE 25) FOR THE MIDDLE COASTAL PLAIN OF GEORGIA (from McGee, 1961) Thickness of Al horizon (in inches) 1

3 6 9 12 TABLE 3.

Depth to a fine-textured soil layer (in inches) 20 30 40 50 60 80 100 Feet

110

46 57 65 67 —

47 60 66 70 74

30 37 42 44 47

47 60 67 71 74

46 59 66 70 73

45 57 64 67 72

43 56 62: 66 69

38 50 55 57 61

33 42 47 49 52

SITE QUALITY (AGE 25) FOR SLASH PINE PLANTATIONS ON OLD-FIELDS OF THE CAROLINA SANDHILLS (after Bennett, McGee, and Clutter, 1959) Depth to fine-textured horizon (in inches)

Thicknes 3 Of the Al heirizon (inche;3)

3 6 9

58 62 66

58 62 66 70

58 61 65 69

57 61 65 69

56 60 64 68

55 58 62 67

100

Feet

45 56 60 64

Stephen F. Austin State College

In northern Florida, better growth is obtained on imperfectly and poorly drained soils than on well-drained soils, provided the A horizon is more than 20 inches deep. Soils with shallower depths to fine-textured material are slightly better adapted for this species if well-drained (Fig. 7). Differences in depth of A horizon greater than 20 inches are not nearly so important as in shallower soils. Depth to mottling is influential to about 20 inches, site quality increasing rapidly with increasing depth (Barnes and Ralston, 1955; Ralston, 1951; Ralston and Barnes, 1955) (Table 4).

DEPTH

TO FINE-TEXTURED

HORIZON ( I N )

Figure 7â&#x20AC;&#x201D;Relation of slash pine site quality in the upper Coastal Plain of Georgia to depth of Al horizon and depth to fine-textured horizon (from Ralston and Barnes, 1955).

TABLE 4. SITE QUALITY '(HEIGHT AT 25 YEARS) FOR SLASH PINE PLANTATIONS IN FLORIDA AS INFLUENCED BY DEPTH TO MOTTLING AND DEPTH TO A FINE-TEXTURED HORIZON (from Barnes, 1955) Depth to mottling (inches)

Depth to fine-textured horizon (in inches) 5

27 47 61 66 65 63 60

25 44 56 61 60 58 55

100

Feet

5 10 20 40 60 80 100

20 36

46 50 49 47 45

26 45 59 64 63 61 58

'Add 3 feet if an old-field. Subtract 4 feet if forest land.

29 51 65 71 70 67 64

28 49 64 70 69 66 63

23 40 52 57 56 54 51

! Silviculture of Slash Pine

Barnes and Ralston (1955) described general characteristics and estimated site quality of common Florida soils. McGee (1961) did likewise for the middle Coastal Plain of Georgia. Thickness of the Al horizon may exceed 12 inches, according to the standard definition of the Al as "a dark colored mineral horizon containing a relatively large amount of humified organic matter thoroughly mixed with the inorganic layer." The amount of organic matter is relative. Thus, in those sands, the Al may have only 1 to 2 percent organic matter, but that is appreciably more than the trace in the A2. The darker color of the Al usually sharply delineates it from the A2 zone. Depth to the fine-textured horizon refers to the total A horizon, sometimes exceeding 8 feet. Soils having deepest Al layers are at the upper edge of the lower Coastal Plain. Depth to the B horizon may be difficult to ascertain. It generally contains more clay; and with sandy surface soils, it frequently is a sandy loam or silt loam. In the Carolina Sandhills SQ (1) increases with an increase in thickness of the Al horizon, (2) decreases with depth to finetextured horizons greater than 10 inches, and (3) is only slightly less than for slash pine in the middle Coastal Plain of Georgia (Row, 1960) (Fig. 8). The detrimental effect of shallow B hori-

20 40 60 80 100 DEPTH TO FINE TEXTURE (INCHES)

120

Figure 8â&#x20AC;&#x201D;Site index curves for old-field plantations in the Carolina Sandhills. These may not be satisfactory for scrub oak sites (from Row, 1960).

Stephen F. Austin State College

zons is somewhat less than for the Coastal Plain. The Al in the Sandhills, gray to yellow sand and loamy sand, is 1 to 10 feet deep. The loamy sand to sandy clay loam subsoils are darker than the A, being yellowish to reddish brown. Beneficial effects of the Al are probably due to the organic matter and its consequent favorable moisture and nutrient relations. Linnartz (1961, 1963) developed a guide for estimating site indices for slash, loblolly, and longleaf pines in southeastern Louisiana using the soil series and mapping units utilized by the Soil Conservation Service. He recommended the following regression be used for predicting the site index of slash pine where soil survey maps are not available: Site index = 59.998 + 0.8639 (DLPL) — 0.0209 (DLPL) 2 —0.004268 (SA)2 + 0.4788 (SB) + 1.601 (ID) — 0.03181 (ID) 2 where DLPL = depth to least permeable layer in inches, SA = percent sand in topsoil, SB = percent sand in subsoil, and ID = degree of internal drainage. This equation accounted for 45 percent of the total variation in site index, with a standard error of estimate equal to ± 4.7. For the Alabama Piedmont, poor slash pine sites are those with less than 2 inches of topsoil, fair sites with 2 to 4 inches, and good sites with 4 to 8 inches. Excellent land—that with more than 8 inches of topsoil—includes well-drained bottomlands. Thus, the regression equation for estimating heights of the tallest trees for slash pine plantations between 5 and 16 years of age is: H = —11.94 + 5.11 (A) + 0.000929 (DxSC) — 0.1127 (A2) where H = height of tallest trees, A = age, D = depth of topsoil, and SC = silt plus clay content of topsoil. The equation is valid for well-drained sites of the Alabama upper Coastal Plain, including the Black Belt (Goggans, 1951). For practical purposes, stand density usually can be ignored in judging site potential for slash pine. Mann and Whitaker (1952) found little effect on height growth of plantations ranging from 250 to 2500 trees per acre. However, in dense, un-

Silviculture of Slash Pine

thinned, natural stands, Collins (1967) found dominant height is not a true indicator of productive potential for a managed stand on the same site. Ralston and Barnes (1955) found survival in plantations at age 25 to be appreciably affected by site quality (Fig. 9).

60 SITE QUALITY (HEIGHT IN 25 YEARS)

Figure 9â&#x20AC;&#x201D;Site quality, as shown by tree heights at age 25, appreciably affects slash pine survival (after Ralston and Barnes, 1955).

The economic significance of the variation in wood production by site is also demonstrable. The difference between 10 and 30 inches to a fine-textured horizon in poorly drained soils exceeds 25 feet in height for 25-year-old plantations and amounts to a difference of about 20 cords of pulpwood per acre (Ralston and Barnes, 1955) (Fig. 10). South Florida slash pine growth rates are dissimilar to those for the typical species. Hence, Figure 11 is presented. Reproduction Establishment Natural

Reproduction silviculture of the pure slash pine type is relatively simple, consisting of (1) prescribed burning for rough reduction, to expose mineral seedbeds; (2) seed-tree cutting, leaving 4 or more trees, totalling 1 MBM per acre; (3) hardwood control, to release seedlings; and

Stephen F. Austin State College

100

DEPTH TO FINE TEXTURE (IN.)

Figure 10â&#x20AC;&#x201D;Height and yield of slash pine plantations at age 25 on welldrained and poorly drained sites in the lower Coastal Plain as influenced by depth to a fine-textured layer (after Ralston and Barnes, 1955). 120

100

AGE (YRS)

Figure 11â&#x20AC;&#x201D;Site quality curves (age 25) for South Florida slash pine in unmanaged stands (from Langdon, 1959, 1961).

! Silviculture of Slash Pine

(4) harvest of seed trees before reproduction is 12 feet tall. Strip clearcutting in bands less than 350 feet wide and with uncut stands 30 to 60 feet wide is an alternative. Selection harvest cutting may be employed where undesirable hardwoods present no problem, since seedlings are not too intolerant of seed trees; but for maximum efficiency, particularly in forests managed for pulpwood, evenaged stands are best (Bennett, 1965a). Group selection or two-cut shelterwood harvests are also applicable. With the latter, the second cut is made 7 to 10 years after the first, leaving 3 or 4 small seed trees for insurance (SAF, 1945). On shallow, hardpan-underlain soils, considerable windthrow results among residual seed trees. Regeneration by isolated seed trees may not be too successful on upland sites, as reseeding takes place chiefly along stand borders where maximum protection from drought-producing effects of sun and wind is accorded. Hence, group cuttings are employed, the direction thereof being oriented to obtain maximum benefit of borders. In northeastern Florida, clearcutting in parallel strips running east to west is suggested where timbered ponds are interspersed with ridges supporting young stands. The strips, 10 feet wide and 100 feet apart, lead to the pond edges and serve as access roads and fire lanes to intermediate areas. In using this system, Schaeffer (1954) found strips taking 9 percent of a stand, by area, caused no reduction in crown canopy beyond normal thinning. Gallberry and titi accompany slash pine in wet areas and, before regeneration can be established, must be controlled. Truck-mounted spray equipment is generally used; hand equipment and aerial applications are not feasibleâ&#x20AC;&#x201D;the former because of the jungle-like nature of the shrubs, the latter because of the sporadic location of the drainages. For seedbed preparation Squires (1947) suggests prescribed burning with winds of 3 to 10 mph from the NE to NW. Those are steady and, therefore, reliable winds. Winter fires are recommended, although only 30 to 50 days each year are suitable. Areas of 400 to 600 acres are burned, for birds devour the seed on smaller blocks. Drainage Slash pine replaces baldcypress in areas where surface water is drained from ponds. Drainage is essential for conversion, even where seed sources

Stephen F. Austin State College

are present and vegetative competition absent, since excess water prevents establishment of slash pine (Fig. 12). r4

80 -

-3

I -2 I

40 -

20-

SLASH SURVIVAL GROWTH__ O- 1

PERIOD OF FLOODING - WEEKS

Figure 12â&#x20AC;&#x201D;Survival and growth of slash pine seedlings 18 weeks after flooding treatments ceased (from Walker, Green, and Daniels, 1961).

A ditch cut through a site typical of a cypress pond, about 600 feet from a seed-tree group averaging 12 inches dbh and 60 feet tall, enabled satisfactory natural restocking of 50 percent or more, but only within 100 feet of the seed source. Farther away, stocking was inadequate. Seedlings on a drained site must be established within 1 year of treatment due, perhaps, to the competition of broomsedge and other grasses which later invade (Olson et al., 1954). In the coastal area of North Carolina, a ditch affecting the water table for 1000 feet improved height growth for over 500 feet, and a definite association between height growth and depth to water table occurred. The response of slash pine to deep-water drainage was less than that of loblolly pine, but the former held its growth rate better in areas farthest away from the ditch (Pruitt, 1947). Early height growth response of pole-size slash pine to drainage of wet, sandy flatwoods in northwest Florida has been encouraging also (Klawitter, 1966),. Tests of soil moisture effects on the rate of seedling growth indicated that slash pines under moist conditions require more water than do longleaf pines to build a unit of dry matter. Slash pine root elongation

Illll

Silviculture of Slash Pine

is good in damp soils, but decreases when soil is saturated (Pessin, 1938). Mycorrhizae also occur more abundantly in moist environments, and trees so infected appear more vigorous than fungus-free stems. Flowers and Seeds Flower Development

A knowledge of flowering and fruiting cycles is essential for employment of cultural methods for seed production. Female flowers occur mostly in the upper branches on apical portions of current year's growth close to the terminal bud. Male flowers, sometimes absent in the upper crown, occur most abundantly at the basal portion of current year's growth. Thus, when on the same branch, male and female flowers are separated by more than 5 inches. Male strobili begin to form in June, initiation of all flowers is complete within 6 weeks, and flowers become visible to the naked eye in middle to late October. Growth is arrested during winter. Female strobili initiation, several weeks behind males, begins between late August and mid-September. [Female flower buds prior to their emergence and other reproductive and vigor conditions may be detected by electrophysiological techniques (Asher, 1964).] The flowers are visible in December and continue to grow during the winter. Staminate flowers, recognized by clusters of up to 8 aments arranged spirally around the axis of a branch, are up to 2 inches long at the time pollen is shed in late January and February (in northern Florida). Pistillate flowers are in groups of 1 to 6. They are receptive to pollen in late January and in February for a period of from several hours to 1 week, depending on the weather. Female flowers are 1-inch long and flesh colored at pollination time. Cones mature in the fall, about 20 months after pollination. Seed Production

Slash pine seeds are generally produced on 3-year cycles, although some are borne almost every year. They are abundant on trees at least 15 to 18 years of age.1 Dispersal is two to three times the heights of trees and up to 1,000 feet in strong winds. Germination is usually in the spring but may occur within a month of seedfall in autumn (Mattoon, 1940). Even o n g ullied u l e sites ss 140 miles mes n north or o of thee sas slash p pine range, seed production has been noted on trees as young: young as 16 years (Rosenkrans. 1944).

I 22

Stephen F. Austin State College

Cone production is increased by releasing seed trees. In one instance almost 3 times as many seeds (7,000 versus 20,000 per tree) and cones (20 versus 55) were produced after release. In uncut stands, where cone production may be light but constant, openings increase flower fertilization the first growing season after cutting. Substantial increases in cones occur the third season after cuttingâ&#x20AC;&#x201D;from 5 to 50 cones per treeâ&#x20AC;&#x201D;and the effect of release is carried to the fourth year (Halls and Hawley, 1954). For optimum seed production, release precedes final harvest by 2 to 3 years, assuming ground cover conditions are satisfactory for germination after seeds fall. Mergen and Koerting (1957) noted an instance of high frequency of male and female flowers in the same strobili on trees in which increased flowering had been brought about by a heavy application of nutrient fertilizer. But in Louisiana, nutrient fertilization failed to induce more flowering except when accompanied by cultivation. Time of application also seemed important. Where half of the fertilizer was applied in March and the rest in May, more flowers were produced than where the same total amount of fertilizer was applied at one time in either month (SFES, 1957). Early and abundant flowering of 6-year-old slash pine on sandy soils in northern Florida was stimulated through an application of 3-12-6 fertilizer at rates of 5, 10, and 15 pounds per tree. Applications were in 5-pound increments beginning in April and repeated at 6-week intervals. With 7-7-7 and 3-18-6 fertilizers at 20 pounds per tree applied in April and repeated in 6 weeks, the 7-7-7 fertilizer produced more flowers on 21year-old trees. Nitrogen probably plays the most important role in stimulation (Hoekstra and Mergen, 1957). Fair to good slash pine reproduction requires at least 800 to 1,500 cones per acre (Wakeley, 1947), and a fair to good seed year provides 50,000 to 100,000 seeds per acre (Cooper and Perry, 1956). Fertilization, cultivation, cutting to convert stands to seed production areas, harvest cutting, pruning to induce a large number of potential flower-bearing branchesâ&#x20AC;&#x201D;each of those operations should precede initiation of strobili in June. Yields of full seeds exposed by slicing cones in half longitudinally can be estimated by the formula: Y = 4.93 + 7.49X where Y = total number of sound seeds per cone, and X = average number of seeds per cone exposed in slicing.

Silviculture of Slash Pine

At least 2 cones from each of 30 trees should be sampled. Gross estimates of pounds of seeds per bushel of cones are made by assuming 200 cones per bushel and 14,500 seeds per pound (McLemore, 1961, 1962). Cone-Counting A technique for counting cones on standing trees was developed by Hoekstra (1960). The observer, using 7x50 binoculars, stands with the sun behind and far enough from the tree so' that all of one side of the crown can be clearly seen. Systematically counting all visible cones up one side and down the other, he does not change position, even though some cones will be missed. The actual number is then computed from the regression: Y = 2.244X where Y = actual number of cones, and X = the count when 7x50 binoculars are held by hand. The number of conelets also can be determined, using a constant of 2.719 when the instrument is held freehand and 2.428 when it is mounted on a tripod. As the constant indicates, more conelets are counted with a tripod mount. No difference occurs between counts of 2 or more observers, nor is the precision of the estimate substantially improved with tripodmounted field-glasses. Sprouting Slash pine basal sprouts from 3-year-old seedlings developed in the spring following a winter fire in Mississippi (Olden, 1954). The area was a low wet flat in which water stood among the rough at the time of burning. Coppice reproduction is unusual except for such circumstances. Planting (Other than Sandhills and South Florida slash pine)

The species is so successfully planted that "clearcut and plant" operations are common.1 Survival of over 80 percent can be expected in years of reasonable weather conditions. A 3-year study in Georgia showed most mortality of slash and loblolly pines occurred during the first year; survival there averaged 71 percent for slash pine and 72 percent for loblolly pine (Jones and Thacker, 1965). Planting should immediately follow harvesting, lest encroachment of undesirable competing vegetation impede early growth of seedlings. In Louisiana, site preparation2 is essential for good survival, but the intensity of the operation is immaterial. Scalped, disked, shallow-furrowed, or deep-furrowed areas respond simi'Malac (1965) reviewed knowledge available on planting and direct seeding slash and loblolly pines. 'Wilhite and Harrington (1965) have summarized the information available on site preparation for planting and seeding slash and loblolly pines.

Stephen F. Austin State College

larly (Shoulders, 1958). Sandhill planting has been good in furrows 14 inches wide and 3 to 4 inches deep (Hatcher, 1957), but this is not universally recommended. Where hardwoods are a problem, only grades 1 and 2 should be planted, the first characterized by a top 6 to 14 inches long and a stem at least 3/16 inch in diameter at the root collar. Grade 2 stock is 6 to 12 inches tall with diameters of 1/8 to 3/16 inch (Hatcher, 1957). Oversize seedlings do not necessarily maintain height superiority for long periods after outplanting, and Foulger (1960) concluded that seedbed selection of superior stock may not be justified. Bengtson (1963) stated that nursery bed selection as currently practiced is of low efficiency in selection of planting material for use on forest sites of average or low quality and gave suggestions for improving procedures. Swearingen (1963) found larger seedlings survive and grow better for the first 2 years. Outstanding slash pine seedlings selected from nursery beds grew about 20 percent taller than control seedlings after 4 years in Georgia and Florid?, (SEFES, 1961; Barber and VanHaverbeke, 1961). An 8-year study by Bengtson (1963) showed the relative height superiority of select slash pine seedlings over controls declined from 83 to 23 percent. Bethune and Langdon (1966) found large seedlings of South Florida slash pine survived better and grew faster than smaller seedlings 6 years after outplanting. Seed size had no lasting effect on height growth of seedlings. Reduction in nursery bed density improved growth of outplanted slash and loblolly pines for 4 growing seasons (Shipman, 1964). Seedlings grown at low densities tend to display morphological and physiological features associated with improved field growth. Although stock from low-density bedsâ&#x20AC;&#x201D;down to 10 per square footâ&#x20AC;&#x201D;survived best when planted in dry years, when all factors were considered, a bed density of 40 per square foot was deemed more efficient by Shoulders (1961) than lower densities. Jorgensen and Shoulders (1967) determined from field studies in northwestern Louisiana that the presence of visible mycorrhizae had a significant and important beneficial effect on survival of slash pine seedlings of all grades. They concluded the greatest opportunity for improving survival potential of seedlings of that species appears to be through increasing the proportion of mycorrhizal stock. Several species of pH-sensitive mycorrhizal fungi are associated with slash pine roots (Zak and Marx, 1964; Marx and Zak, 1965). Root pruning in the nursery is not a re-

Silviculture of Slash Pine

liable method for increasing field survival of slash pine seedlings (Shoulders, 1963). Deep plantingâ&#x20AC;&#x201D;with the base of terminal buds at the ground levelâ&#x20AC;&#x201D;does not appreciably improve survival in a wet year, but height growth is significantly improved in the western Gulf Coastal Plain (Koshi, 1960). Deep planting increased height growth but not survival in southwestern Alabama and southeastern Mississippi (Swearingen, 1963). In the eastern Coastal Plain, on the other hand, planting with half the stem in the soil increased survival but had little effect on height growth (Malac and Johnson, 1957). Two Louisiana studies showed slash and loblolly pine seedlings planted with half their stems below the surface survived as well as those planted with root collars at groundline. Therefore, Shoulders (1962) indicated the advisability of a crew's setting seedlings slightly deeper than root collar depth to reduce chance of shallow planting. On droughty Carolina Sandhills, deep-planting to the bud gave best fifth-year survival, and planting halfway between root collar and bud was better than standard planting. Best 5-year height growth was obtained by planting halfway between root collar and bud. Although large seedlings survived and grew better than smaller ones, grade of stock caused no significant difference in survival when seedlings were planted to the bud (McGee and Hatcher, 1963). Frost pockets should be avoided in slash pine planting north of its natural range. There, south-facing slopes with good air drainage and deep soil are preferred. Damage from sleet and snow, along with poor survival, generally preclude planting slash pine in north Mississippi and west Tennessee, although it has been planted with success as far north as central North Carolina. However, survival and growth are usually inferior to loblolly pine in the Piedmont of that state ^Claridge, 1933). Mattoon (1936), observing the northward migration of slash pine, reported good early growth on stiff clay in the Georgia and South Carolina Piedmont, 100 miles from the natural range. A survey of over 8,000 acres of pulpwood-size, erosion-control pine plantations on eroded sites in north Mississippi showed a survival of 38 percent for loblolly, 48 percent for shortleaf, and 29 percent for slash pine. Annual growth averaged 0.89 cord for loblolly, 0.58 cord for shortleaf, and 0.88 cord for slash pine (Williston, 1963). Slash pine has outgrown loblolly pine in mixtures

Stephen F. Austin State College

planted on a poorly drained, cutover long-leaf pine site in southwestern Louisiana. Two rows of slash alternated with two of loblolly proved more successful than four-row mixtures (Box, Linnartz, and Applequist, 1964). Bennett (1956b) reported on a plantation spaced 17x17 feet producing annually l!/2 cords and 5 square feet of basal area per acre, and a 19-year-old stand that yielded 26 cords per acre. Sawtimber volume almost doubled from ingrowth in two growing seasons. Nelson (1952) measured annual diameter growth of 0.3 inches and upwards for the first through seventh years in the Piedmont. Height growth can be expected to approach 3 feet per year between the third and tenth years. When subfreezing temperatures are anticipated, baled seedlings should be stored in buildings or at least covered with plastic or canvas tarpaulins. It is probably best to discard unprotected slash and loblolly seedlings that have been subjected to temperatures of 20 째F and below for more than 48 hours (Byrd and Peevy, 1963). Drainage Good growth is best in moist depressions at pond margins which are temporarily flooded almost every year, but excess water in plantations should be removed to depths of 4 inches below ground level for optimum growth (Fig. 13). Inundation as frequent as once in 3 weeks to a depth of 3 inches is too severe (Walker, Green, and Daniels, 1961). For young planted seedlings to survive, terminal buds must be above water. One-year-old trees can survive 2 weeks of total immersion. Continuous flooding to depths of 4 inches may not cause severe mortality the first year, but heavy losses can be expected if sites are not drained by the end of the second growing season (Fig. 14), Eight inches of water, even though not overtopping seedlings, causes much greater losses (Walker and Green, 1961). Swamps in Florida, however, have been cleared of small slash pines when water depth exceeded seedling height. Indeed, muddy, stagnant water is lethal. "Tussock seeding," where 6 or 8 treated seeds are pressed into rotten pine or cypress stumps, cypress knees, dead snags, tussocks of bamboo vines, windfalls, and almost anything else lying on the ground above water, has proved useful on swampy sites. Planting slash pine seedlings on mounds or ridges formed by bulldozers or tractors on poorly drained sites has improved growth and survival also (Cooper, 1961; Langdon, 1962). When excessive water is drained to 4 inches below ground level in highly reduced plastic clay loam soils of the tidewater zone, growth is appreciably improved for at least the first 2 years by a single fertilizer application in the spring following planting of 1000 pounds of 8-8-8 plus 100 pounds of a mixture of trace elements per acre (Fig. 15). Where not

Silviculture of Slash Pine

Figure 13â&#x20AC;&#x201D;Slash pine seedlings after 2 years in the field with water controlled at (left to right) ground level, 4 inches above ground level, 8 inches below ground level, and without control (from Walker, Green, and Daniels, 1961). drained, supplemental nutrients increased mortality, probably because of toxic salt absorption of the soluble elements. Needle length, foliage color, and foliar nitrogen, phosphorus, and potassium were influenced by the various combinations of water and fertilizers applied (Walker, 1962, 1962a). Third- and fourth-year results indicate slash pine is more responsive to these treatments than loblolly pine (Walker, 1967). Fertilization1

Seedling growth is improved when fertilization in the spring accompanies cultivation. It is doubtful if cultivation alone appreciably stimulates growth of larger seedlings due to inevitable destruction of the feeder roots in the surface soil. In some cases single applications of *^> and 2 tons of colloidal phosphate per acre at time of planting resulted in significant diameter increases over a 15-year period on acid flatwoods soils. Neither survival nor wood density was influenced. Volume in the J/i-ton per acre plots averaged 45 percent greater than in untreated areas at the end of the period and was substantially increased by disking-in the phosphate (Pritchett and Swinford, 1961). 'See review by Walker (1965).

Stephen F. Austin State College

is it

41 68 101 133 166 206 NUMBER OF DAYS AFTER FLOODING

Figure 14â&#x20AC;&#x201D;Relation between height of seedlings above water and their survival with respect to time since flooding began (numbers in parentheses indicate water level treatments; from Walker, Green, and Daniels, 1961).

Symptoms of nitrogen deficiency for this species are common in sandy soils (Pritchett and Perry, 1959). Diameter and basal area responses to nitrogen fertilization at age 9 were obtained in a slash pine plantation in deep sandy soils of the lower Coastal Plain. Response to applications of 100 pounds per acre of nitrogen occurred for each of the first 3 years after treatment, but maximum stimulation followed a 1-year delay. Height growth was apparently not affected, nor did phosphorus at a rate of 44 pounds (100 pounds of P205) improve growth. Thus, foliar and soil analyses after 3 years indicate that, at the rate of fertilizer used, nutrient cycling is ineffective for sustaining growth stimulation due to fertilization in the Lakeland soil type (Walker and Youngberg, 1962). Nitrogen, however, continued to influence diameter

Silviculture of Slash Pine

100

SLASH

LOBLOLLY!

-4

±0

NO FERTILIZER

-4

±0

DOUBLE FERTILIZER

22 20 1816-

|2 14-ton 108 6 4 2

-4

±0

NO FERTILIZER

-4 DOUBLE

±0

FERTILIZER

Figure 15—Survival and growth of seedlings at the end of the second growing season for 3 water and 2 fertilizer treatments (from Walker, 1962a).

Stephen F. Austin State College

growth; phosphorus was still ineffective 5 years after treatment (Walker, 1967). For this slash pine stand, Williams and Hamilton (1961) noted that specific gravity was decreased by 6.7 percent over a 2-year period following nitrogen application. The decrease in specific gravity, however, was more than offset by the increased volume growth. Fertilizing slash pine in Florida was responsible for increasing growth 37 percent during a 7-year period in a 12-year-old stand, where applications were made three times a year over a 4-year period, each year totaling 500 pounds per acre of nitrogen and varying amounts of phosphorus, potassium, and minor elements (McGregor, 1957). Boggess and Stahelin (1948a) found that cultivated and fertilized plantations in Alabama, where each tree received 0.3 pound of a complete fertilizer of 1-5-4 analysis, equivalent to 200 pounds per acre, produced I1/* times the volume of untreated stands. Side dressings of over 0.1 pound of nitrogen (67 pounds per acre of sodium nitrate) were made after growth started. Surface treatments in the Piedmont of 200 pounds per acre of ammonium nitrate applied during the first spring produced an appreciable increase in stem growth during the first growing season (Jackson and Cloud, 1958). Walker and Morcock (1965) report increased diameter growth in a 21-year-old plantation from nitrogen supplements. Barnes and Ralston (1953) report improved height growth for slash pine in Florida from 1- to 2-ton per acre applications of colloidal phosphate, a material which, as mined in Florida, contains 2 to 4 percent acid-soluble P205 and up to 24 percent total phosphoric acid. The phosphate should be spread in alternate 4foot strips with rows centering the strips. Disking at time of planting tends to improve growth, but not all plantations respond to such treatment or to the placement of phosphate in planting holes. Pritchett and Perry (1959) also found growth responses to phosphorus. Experience with slash pine in Australia indicates responses to fertilization at rates of over 300 pounds per acre of rock phosphate (40 percent P205) and 700 pounds of superphosphate (21 percent P205) (Young, 1948; Richards, 1956; Moulds and Applequist, 1957). In Alabama, phosphorus in soil and litter was still highest on fertilized plots and lowest on non-treated areas 19 years after adding nutrients (Gilmore and Livingston, 1958).

I 31

Silviculture of Slash Pine

Phosphorus at a rate of 50 pounds per acre was the most effective of several fertilizer elements and rates tested by Hughes and Jackson (1962). They also found some evidence of interaction between nutrients when slash pines were fertilized for 2 years on Lynchburg loamy sand in Georgia, observing that potash without nitrogen, and nitrogen without potash, retarded growth. Although response to complete fertilization was good, the low cost and good vigor obtained by phosphate alone indicated that to be the most efficient treatment in their tests. McGee (1963) conducted a nutritional study of slash pine seedlings grown in sand culture for 4 months. Nitrogen influenced fresh weights most, and potassium exerted the most influence on dry weights and seedling elongation. Maximum growth response occurred when nitrogen and potassium were greater than 125 ppm but less than 625 ppm. Maximum response to phosphorus was not reached at 125 ppm, the highest supplied. The ability to absorb nutrients may vary by seed source (Walker and Hatcher, 1965). Site Potential

Growth increases, as expected, with site index in all age classes, but the degree of this growth rate diminishes after age 20 (Table 5). TABLE 5. PERIODIC ANNUAL HEIGHT GROWTH OF DOMINANT SLASH PINE TREES ON VARIOUS SITES (after Bennett, 1960) Annual height growth by site index class

Age period

20-25 25-30 30-35 35-40 40-45 45-50 50-55 55-60

1.0 0.8 0.5 0.3 0.2 0.15 0.05 0.05

1.3 1.0 0.5 0..4 0.3 0.2 0.10 0.05

1.7 1.1 0.7 0.5 0.3 0.2 0.10 0.10

1.9 1.3 0.8 0.7 0.3 0.2 0.10 0.10

2.2 1.5 0,9 0.7 0.4 0.2 0.15 0.10

2.4

1.8 1.1 0.9 0.4 0.2 0.20 0.10

Thus, 20-year-old trees grow 2.4 times as much on SI 90 as on SI 40 land, but 60-year-old trees only double their height growth. After a certain age, crown length cannot be appreciably increased through additional height growth. This, in turn, means crown length: tree height ratios cannot be materially increased by release, but since release prevents loss at the base of the crown, the ratio is more readily maintained (Bennett, 1960).

I 32

Stephen F. Austin State College

Slash pine plantations ranging from 9 to 25 years of age in the flatwoods of Florida and Georgia provided data for regression analysis of growth in relation to age, site, and stand density. Three factors accounted for 89 percent of the variation in cubicfoot growth, as calculated from the equation: P = 0.589 (s) â&#x20AC;&#x201D;0.033 (b) 2 + 0.051 (sb) + 0.0003 ( a x b 2 ) â&#x20AC;&#x201D;3.085 where P = periodic annual growth, s = site index, b = basal area in square feet per acre, and a = stand age. The interrelationship of site index and stand density is significant, indicating that maximum growth occurs at a higher stand density on good sites than on poor sites (SEFES, 1960). In Georgia, optimum growth of plantations was found on sites having a depth to a fine-textured horizon of 28 to 30 inches. On sites where depth to a fine-textured horizon is greater than 30 inches, moisture becomes limiting because of the poor water-holding capacity of the surface horizons (SEFES, 1960). Sites in southwestern Mississippi, where a rainfall deficiency of 7 to 23 inches per year accrued in 4 of 5 consecutive years, were compared (Smith, 1960). On upland sites abandoned from agricultural use after 25 years of cropping, SQ is 70 and annual height growth 4 feet. On a similar upland site, but cutover, SQ is 65 and annual growth 3.7 feet. A cutover swamp with some drainage but with a muck surface soil and an organic loamy sand subsoil has a SQ 55 and an annual growth of 2.7 feet. In contrast, a sandy wet meadow of sedges and grass, without drainage, was of SQ 30, and the trees grew 1.2 feet per year. Foliage in the wet meadow was pale and stunted in contrast to the dark, thrifty-appearing foliage of the cutover swamp. Poor growth in the meadow, a site low in nitrogen and phosphorus, could have been due to infertility or to a deficiency of oxygen. Spacing

Spacing ranging from 6x6 to 15x15 feet has been recommended, depending on the ultimate crop: close for pulpwood rotations, intermediate for early sawlog production, and wide for naval stores. Average annual dbh growth for slash pines through the first 15 years varies from 0.4 to 0.7 inch. Trees at 8x8 feet grew 4 inches in 14 years and those at 16x16 feet grew almost 6

Silviculture of Slash Pine

inches. An 8x8-foot stand produced about 500 board feet per acre while 17xl7-foot placement had a sawlog volume of 2,700 board feet (Bennett, 1956b) (Fig. 16). Volumes and basal area per acre at age 10 generally seem to increase with spacing up to 11x11 feet and then decrease.

Figure 16â&#x20AC;&#x201D;A 19-year-old slash pine plantation spaced at 15x15 feet. Average dbh is 10 inches, and the stand contains 7.5 MBM per acre. Stumps in foreground are from the initial thinning which removed 6 cords per acre (from Bennett, 1956b).

Twenty-year yields from 3 spacings of planted slash pine in Louisiana were as follows: 5x5 = 30 cords 6x6 = 27 cords 8x8 = 26 cords. At 30 years, the dense stand still produced the greatest volume (Bull, 1947). Smith (1967) reported similar findings for a 21year-old plantation in southern Mississippi. Russell (1958a) studied the relation of plantation spacing to

Stephen F. Austin State College

growth west of the Mississippi River. A 14-year-old stand on a cutover longleaf pine site with good surface drainage and moderately slow internal drainage produced the greatest volumes with 4-foot spacing, as opposed to 5, 6, and 13 feet. Average dbh, however, was 4 inches in contrast to 7 inches in the widest spacing. Stands 6x6 feet had almost as many trees 7 inches dbh in 14 years as those spaced at 13 feet, and stands 4x4 feet had almost as many 5-inch dbh stems as the 13-foot stands. Although only for trees over 8 inches dbh does the wider spacing really show superiority by age 14, about 17 years is needed to fully utilize sites at 13-foot spacing. At that wide spacing, too, height to the lowest live branches is considerably less, and therefore ultimate sawlog quality is diminished. Harms and Collins (1965) found the average tree diameter of slash pine through the seventh year has a positive linear relationship with spacing. Hawley (1953) reported on an 18-year-old plantation from natural 2-year-old stock lifted from drainage areas and planted at 15-foot spacing in an abandoned field. Two hundred trees per acre were 5 inches or larger, and 140 were sawtimber size. The average dbh was 10 inches, basal area 100 square feet per acre, and volume growth 1.7 cords or 370 board feet per acre per year. After age 18, volume growth is expected to increase greatly due to ingrowth into sawtimber size classes. In contrast, crowded stands on similar sites, but occurring naturally, were growing about one-third of normal or 0.4 cord per acre annually (Bennett, 1955). A plantation in west central Florida established on abandoned farm land fertilized with barnyard manure and planted to cowpeas during the fall before winter reforestation with 3-year-old wildlings required thinning at age 11 (from planting) to reduce basal area from 180 to 100 square feet per acre. Now at 25 years, the trees average 12 inches dbh and over 75 feet tall. The original spacing, from 6x6 to 10x10 feet, resulted in yield differences at early ages, from which it appears that 8x8-foot spacing can produce sawtimber and poles in 35 years with 3 intermediate thinnings (Arlen, 1959) (Table 6). The volume at the end of the rotation, however, is not expected to vary appreciably by spacing, nor will the total yield. Yet, yields of unthinned slash and South Florida slash pines increase as stands become denser, mean annual growth generally culminating later in the lower stand densities than in well-stocked forests (SEFES, 1960).

Silviculture of Slash Pine

TABLE 6. THINNING AND VOLUME AT AGE 25 OF SLASH PINE PLANTATIONS IN WEST CENTRAL FLORIDA (after Arlen, 1959) Volume

Total

1956

per acre

volume

12.2 12.4 11.6 13.3 13.2 13.1 12.9

36 31 29 32 35 32 29

56 47 54 59 60 61 58

Yield/acre Spacing

1947

1952 Cords

10 x 10 9 x 10 8 x 10 8x8 7x7 6x6 5x5

15.7 16.3

7.6 4.0 13.6 13.6 11.4 â&#x20AC;&#x201D; â&#x20AC;&#x201D;

Competition for slash pine develops at a density of 500 to 550 trees per acre during the fifth growing season and has an increasing effect during the sixth and seventh years, according to tests in the middle Coastal Plain of Georgia. An example of the increasing effect of stand density is the expanding difference between the mean diameter of 15x15- and 6x6-foot spacings. Trees at the wide spacing were only 4 percent larger than those spaced 6x6 feet at the end of the fourth year, but over 23 percent larger at the end of the fifth year. After 9 years, the 6x6-foot spacing had about three times more square feet of basal area than the 15x15 spacing. For the first 20 years, mean annual diameter growth on an average old-field site will be about one-half inch for a 15x15 spacing and one-third inch for a 6x6 spacing. Height growth is not correlated with stand density; but crown ratios after 7 years are in direct proportion to crown density (SEFES, 1960; Bennett, 1963). Harms (1962) concluded that competition for light had begun at 6x6 spacing during the fifth year. Root competition, and therefore competition for soil moisture, was not yet apparent during the sixth and seventh years. Bennett (1963) has summarized yield studies of slash pine plantations done by various workers in several states. Studies in Florida show that although the closer spacings (e.g., 6x6) give the greatest cordwood yield on sites 50 and above, spacing has little effect on yields at lower site classes. It appears that only a few trees can efficiently utilize the potential of poor sites. Volumes on the better sites indicate a limit beyond which added stocking contributes little to the total yield. From age 15 upward, 200 trees produce over half the yield of 1000 trees, and 600 trees produce more than 90 percent of the 1000-tree yield (Bennett, 1962). Depending on stocking, mean annual growth of plantations in Florida culminates on sites of index 50 or more at 18 to 25 years

Stephen F. Austin State College

of age, although such early culmination was not found in studies in other states. Yield in relation to site is described in detail by Bennett (1963, 1965) also. Fusiform rust occurrence may be related to density. Almost one-third of the trees at wide spacing had living fusiform rust cankers in contrast to 15 percent in dense stands. As most infection originates on side branches where current year's needles prevail, this probably is due to early natural pruning in dense stands, killing infected branches before mycelia reach boles. Slash pine must not be interplanted. Even a one-year delay is sufficient to stagnate permanently the later-planted trees (Schultz, 1961, 1965). Also, residual pines, as well as hardwoods, must be removed from plantations before or shortly after planting. Spacing does not affect early survival. Burns (1962) concluded from a plantation study on an upland site in north Mississippi that the southern pines and sweetgum do not mix, as the pines soon outgrew and overtopped the gums.

D.B.H. (INCHES) Figure 17â&#x20AC;&#x201D;Diameters of planted slash pine for various spacings at age 14 and over (from Bennett, 1956b).

Hawley (1965) pointed out that the standard 6x6 spacing recommended in the past is not prescribed so confidently today. One must consider the productive potential of the land, the product desired, and whether thinnings are to be made, along with other economic and biological influences. A compromise recom-

Silviculture of Slash Pine

mendation to get an optimum stand when all characteristics are considered together is to plant at a spacing of 6x8 feet, or 900 trees per acre (Russell, 1958). Summer Planting Recent studies indicate summer plantings may be successful (Schultz and Wilhite, 1967). Survival success of such planting may be explained: although summer temperatures are generally higher than winter temperatures, the rainfall is greater and more evenly distributed in summer, at least in the eastern part of the range. Even though seedlings planted in August stopped growing after out-planting, they more than made up for that loss the following spring. Thus, food was stored during the first full growing season in the field for growth the following year (SEFES, 1959). Wilhite (1966) tentatively recommended that summer planting of slash pine in northeastern Florida be done between late June and late September when rainfall is normally adequate and soil is moist. He advised that nursery beds sowed in late November produced satisfactory seedlings, averaging at least 6 inches in height and with numerous secondary needles, by late June; sowing in early March produced them by early August. While it is best that seedlings be planted within a day after lifting, refrigeration above freezing temperature appears to be beneficial if longer storage is necessary. Cultivation

Cultivation before planting, a type of site preparation, on freshly abandoned agricultural land stimulates growth by holding vegetative competition in check. Its use in the lower Coastal Plain and elsewhere is described by Anderson (1958), Meyer (1960), Stevenson and Schores (1961), and Hughes (1965a). For instance, in an East Texas loamy fine sand more than 4 feet deep, previously in watermelons, a 13-year-old slash pine plantation produced 26 cords per acre; the trees, then averaging 6 inches dbh and 40 feet tall, were ready for thinning (Wallace, 1960). Where wet though not flooded sites in the Southeast were cultivated, slash pine height growth was doubled, exceeding 9 feet in 4 years. Survival was not affected (Jones, 1959). Elsewhere, cultivation after planting increased survival as well as diameter and height growth for at least 4 years (Table 7). Worst (1964) obtained similar results from site preparation studies in the Coastal Plain of southeast Georgia. For no apparent reason TABLE 7. CULTIVATION INCREASES SLASH PINE GROWTH AND SURVIVAL AFTER FOUR GROWING SEASONS (after Balthis and Anderson, 1944) Not cultivated

Survival—percent Heights—feet D.b.h.—inches

Cultivated

98 11 2

Stephen F. Austin State College

ground-line forking also increased after cultivation; a possible cause for the increase is that dormant buds are stimulated by greater vigor or by damage to roots in periodic treatment (Balthis and Anderson, 1944). Spring fertilization in conjunction with cultivation improved height growth of 4-year-old seedlings in central Alabama (Westberg, 1949, 1951). In spite of those findings, cultivation is not generally recommended, for the fine feeding roots are periodically destroyed and the low infiltration rate of freshly tilled land encourages water runoff and soil movement. A puddled soil condition also decreases aeration for root growth. Planting (Sandhills)

The site classes most in need of understanding for intensive forest management are the very dry and the very wet. The Sandhills along the Fall Line dividing the Piedmont Province from the Coastal Plain and most of west Florida are among the driest sites. Once, these areas carried open stands (4 MBM per acre) of slowgrowing longleaf pine of relatively high quality, but now the sites are scrub oak-wiregrass barrens, unless intensively managed (Hebb, 1957) (Fig. 18). Slash pine is the principal species to

Figure 18â&#x20AC;&#x201D;The original longleaf pine-scrub oak vegetation of the Sandhills (from Hebb, 1957).

Silviculture of Slash Pine

plant in west Florida (Hebb, 1955) and is also important for reforestation in the Fall Line Sandhills. Intensive management requires that pines be given a couple of year's advantage over brush species through site preparation. Recommended spacing then is about 7x7 feet. Ralston and McGee (1962) point out that planting slash pine on turkey oak lands of the Carolina Sandhills may not pay in many instances. Average site index was submarginal for growing slash pine on those lands, the site index (25-year basis) averaging 29 as compared to 52 for old-field plantations. Landowners should use discretion in scrub oak clearing and planting, for some Sandhill soils do have a high potential (Fig. 19).

Figure 19â&#x20AC;&#x201D;Slash pine plantation, age 14 years, thinned at age 12. Growth was 21 cords per acre, 1.5 cords per acre per year. Another Sandhills old-field plantation produced 19 cords in 13 years (Hebb, 1957; USFS photo). Site Preparation

Because of the extreme importance of soil water in Florida's Sandhillsâ&#x20AC;&#x201D;the greater the moisture during drought periods, the better the survivalâ&#x20AC;&#x201D;complete denuding prior to planting is the

Stephen F. Austin State College

only acceptable method of site preparation (Woods, 1956, 1958). Common methods for controlling the scrub hardwoods include use of heavy machinery, such as tractor-pulled undercutters, choppers, and shredders. Bulldozers are employed for removing grass â&#x20AC;&#x201D;and top soilâ&#x20AC;&#x201D;as well as scrub oaks, since grass roots are serious competitors with pine for moisture.1 Woods (1959) recommends an 11-ton double-drum brush chopper treatment in late April to early May when carbohydrate root reserves are minimal and sprouting vigor is low. A second treatment is made 6 weeks later; slash pine is planted the following winter. Another sequence is to precede chopping with prescribed burning about May 1. The two chopping treatments to control sprouts are then made in the middle of June and in August or September (Woods, Cassady, and Rossoll, 1958). Chopping does not remove the organic matter but, rather, works it in, thereby improving water-holding and cation exchange capacities. Brendemuehl (1967) found reduced growth of potted seedlings with simulated removal of topsoil was correlated with the decreased nitrogen and organic matter content of the soil. Woods (1959) notes that as the deep sands of west Florida have only 1 percent organic matter in the upper foot, even small increases may be helpful. Moisture equivalent, closely correlated to organic matter, is as low as 3V-> percent, and wilting coefficient 1 percent or less. In another system, all vegetation is pushed into windrows, roots are then cut, soil and roots harrowed, and the area redisked after resprouting of hardwood roots,. Organic matter is, of course, removed; but seedlings planted in denuded sandy subsoil are more vigorous than those competing with wiregrass in the slightly organic surface soils. This moisture-cultivation relationship is exhibited by the considerably longer time lapses for soil 3 to 9 inches deep to reach the wilting point when the land is completely denuded by heavy equipment than when vegetation is eradicated without mechanically disturbing the soil (Fig. 20). Planting in furrows has given similar results to complete denuding with heavy equipment in a favorable year (Woods, 1956). Bulldozing all vegetation and several inches of topsoil into windrows and then leveling the site with a road-grader gave 85 percent survival after 3 years in contrast to 36 percent where oaks were chemically controlled and 61 percent where trees were planted in plowed furrows. Height growth was also most favorable under bulldozed conditions (Scheer and Woods, 1959). 'The influence of grass and weed competition was demonstrated in a study made by Stransky and Wilson (1966) in East Texas. UsinR a transparent plastic shelter to simulate drought, they found 99 percent of the slash, loblolly, and shortleaf pine seedlings survived 7 months on scalped plots compared to 30 percent on Krass- and weed-covered plots. Shortleaf pine, generally considered the more drought resistant, survived sod competition better than slash or loblolly pine.

Silviculture of Slash Pine No treatment

ÂŁ

Oaks chemically controlled

Plowed furrows

Completely denuded

~ 6 = 5

15 20

0 5

0 5 10 15 20

D a y s since last

0 5 10 15

rainfall

Figure 20â&#x20AC;&#x201D;Soil moisture depletion in differently prepared sites, 3- to 9-inch soil depth (after Woods, 1956). Lehocky and Lee (1954) recommend the following technique for the South Carolina Pall Line Sandhills: (1) reduce scrub oaks in May and June with heavy machinery; (2) allow scrub oaks to sprout; (3) double plow 10 inches deep in July and August with fire plows pulling 28-inch disks; (4) allow scrub oaks to sprout; (5) level area in September with a gang disk plow with 18-inch disks; (6) machine plant in December and February. Some owners have profited by having Sandhill land cleared and cultivated for two watermelon crops, after which pines are planted. (A watermelon disease precludes more than two subsequent crops on the same soil, yet crops provide sufficient revenue for clearing and planting.) Actually, survival increases as the carbohydrate food reserves in root cuttings, from which hardwoods sprout, are further reduced by each succeeding cultivation. The use of sawdust or woodchips in furrows is suggested as a means of increasing organic matter content and its coincident moisture-holding capacity. That, however, necessitates fertilizing with nitrogen to satisfy demands of both the cellulose-decomposing bacteria, which digest woody material, and the seedlings. One-hun,dred pounds of ammonium nitrate per ton of dry wood waste are required. The fertilizer should be applied in two or more applications, as nitrogen is lost by leaching faster than organic materials break down. Underplanting scrub oaks is not recommended; but where it has been done, pines should be immediately released. All hardwoods probably will have to be deadened. Silvicides are used either in conjunction with mechanical eradication or alone for hardwood control. Fire is an ineffective tool for controlling weed trees and grass in the Sandhills, as sprouting is vigorous and wiregrass un-

Stephen F. Austin State College

inhibited (Hebb, 1957). Nor is light farm equipment satisfactory for this operation, since the prolific sprouting which follows a relatively mild treatment causes greater competition than does the pre-treatment vegetation. Roots and Soil

Pines have shallow roots, most feeders being less than 3 inches deep, on those deep sands. Frequent light summer rains replenish soil moisture in the surface layer, but leaching is rapid. In addition to rainfall distribution, factors limiting root penetration in deep sands include low nitrogen and calcium levels, soil temperature, and rate of organic matter decomposition. Woods (1957) found 3 to 4 times more nitrogen and 8 times more calcium in the upper 3 inches of soil than in the layer at 9 to 12 inches. The organic matter in the surface soil, in which the nitrogen is contained and the calcium held on colloidal particles, decomposes rapidly. Thus, some nitrogen is lost to the atmosphere and the calcium leached. High winter temperatures in the surface soil result in root growth of succulent tips up to 3/4 inch long in December and January. Because this winter root growth begins within a week of the planting season, it probably accounts in part for good plantation survival (Woods, 1957, 1959b). Within 2 weeks after a rain, soil moisture in the west Florida Sandhills drops below the wilting coefficient in undisturbed sites. Even where furrowed, burned, harrowed, chopped and burned, or where scrub oaks are chemically controlled, the wilting point is rapidly reached. Only where vegetation is completely removed, as when bulldozed, is soil moisture above the wilting range as long as 2 weeks after rain (Scheer and Woods, 1959). While it appears that removal of all vegetation would seriously expose newly planted seedlings to high temperatures, it has been shown otherwise: reflection of the sun's rays from light-colored sands combined with heat absorption is not sufficient to cause high mortality, even though frequently rising to 125 째F. The lethal temperature for seedlings is 130-135 째F. Mulching apparently is not beneficial to seedlings from a thermal standpoint, even in bulldozed and scalped sands, as temperature within the mulch exceeds 160째F. However, the soil surface under the mulch may be 60 째F cooler than within the mulch. Thus, neither soil temperatures in the surface of bare sand nor under mulches ever reach the lethal point. Soil moisture is not improved by mulching those sites, nor does the small amount of

Silviculture of Slash Pine

moisture lost to evaporation differ appreciably under mulched and unmulched conditions (Woods, Hebb, and Fassnacht, 1956). The ability for plants to transfer moisture through intertwined, but not grafted, root systems may be important in delaying, or even preventing, wilting in those sands. Bormann (1957) found the transfer occurs only after some critical moisture tension is achieved. Thus, roots from plants in moisture pockets can effectively absorb water for use of plants in drier, microclimatic conditions. Moisture pockets may be separated from dry areas by several feet in horizontal distance and a couple of inches vertically in xeric sites. Planting (South Florida Slash Pine)

Ridges and furrows left by cultivation provide a miniature topography important to survival of pines on flat, wet land typical of the lower peninsula. There, even 6 inches elevation governs water level and hence markedly affects plantation establishment. Water standing in furrows too long during a rainy season for 2 or more consecutive years is injurious, and most mortality is noted during such periods of inundation. Langdon (1956) found 3-year survival on ridges to be three times greater than in furrows: 94 vs. 26 percent. Growth of South Florida slash pine at the end of 3 years was 51 and 33 inches for ridge and furrow. Planting on ridges prepared by a fire plow may be better than chopping or complete brush eradication in South Florida for both forms of slash pine. Palmetto requires 60 to 80 years to reinvade once completely cleared from the land. Three-fourths of the 50 inches of rainfall in South Florida occurs during the growing season, while November to April is relatively dry. The frequent droughts that take place in the winter cause considerable mortality among newly planted seedlings. Clipping needles to reduce transpiration does not aid survival but, rather, has an adverse effect, possibly because South Florida slash pine needles, remaining healthy green in the dormant season, are apparently photosynthesizing and respiring. Either of those processes is, of course, disturbed by clipping (Langdon, 1955). The winter color of the foliage of this variety is in contrast to the yellow hues during the winter of other southern pine foliage for which needle clipping may improve survival. For prepared sites on high elevation palmetto, low elevation palmetto, and wet prairie land, survival is best on the high pal-

Stephen F. Austin State College

metto. But the kind of site preparation, whether bulldozed, chopped, or disked, is unimportant. In the flatwoods, saw-palmetto density is a key to drainage. Denser stands of the stemless palm occur where drainage is most rapid on the higher and drier sites. Where saw-palmetto cover is light to only moderately dense, soil moisture is continuously maintained at a relatively high degree and, therefore, seldom limits seedling growth. Survival and growth are best with large seedlings. Nursery stock should be graded at time of planting, the small stems discarded, and the largest favored. Large seedlings are 0.4 foot, medium 0.3 foot, and small 0.2 foot tall. As survival may be best with large seeds, it could be desirable to offset expected mortality of stock produced from seeds known to be small by planting at reduced spacing. Silviculturists may consider collecting average size cones, grading seeds by size to facilitate survival, and planting only the largest in nurseries. Neither seed nor cone size influences seedling growth for long. In spite of the belief that South Florida slash pine is as large as the typical species in 10 years, slash pine from north Florida is planted even in the southern end of the peninsula. Wood from the South Florida variety, too hard and dense for receiving nails, is not on the lumber market except in Miami where it is marketed as Bade County pine. South Florida slash pine plantings in the sapling stage also appear more susceptible to hurricane windthrow than the typical species. That could be due to poorer planting for the former, as its comparatively long roots make proper placement difficult. This may not hold true for rootpruned stock. Old-Field vs. Cutover Forest Trees in old-field plantations grow twice as rapidly as on cutover land for the first 5 years after planting. Survival is also superior where sites have been prepared through agricultural cropping and is poorest where roughs are heaviest. As previously discussed, Ralston and McGee (1962) found site index of plantations on old-fields averaged much higher than on scrub oak sites in the Carolina Sandhills. Conjectured reasons are the effects of tillage in reducing competition, residual fertilizer, and inherently different sites which, in the first place, caused some to be selected for farming. The moisture regime is probably involved, as water infiltrates more rapidly on cutover areas than in abandoned old-fields, even after several years of lying idle (Bennett, 1956a). Faster growing old-field trees may also have greater infection of fusiform rust than those in cutover forests.

Silviculture of Slash Pine

Direct Seeding

Direct seeding of slash pine was accomplished as early as 1920, using 2 pounds of seed per acre on poorly drained "crawfish" land in the f latwoods (Mattoon, 1936). Slash pine is better adapted than loblolly pine for broadcasting on cutover longleaf pine flatwoods sites of the western zone, even though out of its natural habitat (Silker and Goddard, 1953). Koenig (1962) found direct seeded slash pine has for the first 4 or 5 years developed equally as well, if not slightly better than, planted stands in southeast Georgia and north Florida. Seed should be covered with Va to %, inch of soil for best germination (Jones, 1963; Shipman, 1963). Also, damp cold storage stratification or perhaps soaking in water or hydrogen peroxide for several hours improves germination (Jones, 1963; Varnell and Bennett, 1966). While unstratified seed treated with repellents can be stored for several weeks in sacks in a well-ventilated, unheated building, stratified seed can be kept that way for only a week; they can, however, be stored longer at 34°-42°F (Mann, 1966). Germination of seed with a high moisture content may be reduced by the fumigation with methyl bromide usually given lots that are imported (Jones, Barber, and Mabry, 1964). Seed coating consists of Arasan 42-S to repel birds, Endrin 50-W for rodent protection, Dow Latex 612 to hold repellents to the seed, and an aluminum overcoating to make seeds flow freely through sowing mechanisms (Mann, 1965, 1966). Unstratified slash pine seed treated with anthraquinone (a bird repellent) and Stauffer's Endrin 50-W had good viability after 1 year of storage at 38°F in sealed glass jars; unstratified seed did not decrease in viability after 60 days' storage at room temperature (70-80°F). Germination was adversely affected by Arasan-75 treatment, although viability was diminished little more by storage for up to 60 days at 38 and 70-80°F (Jones, 1963). General recommendations for time of sowing were summed up by Mann (1966) and Mann and Derr (1965) as follows: (1) sow in October and November on sites within 50 miles of the Gulf Coast, and in interior Florida; (2) sow in mid-February in the upper Gulf Coastal Plain; and (3) if in doubt, sow in mid-February, provided that early spring droughts are not common. Varnell and Bennett (1966) concluded the optimum season for sowing slash pine in the flatwoods of the Atlantic Coastal Plain lies between the first of February and the middle of March.

Stephen F. Austin State College

Sowing, at rates which vary around 1 pound (14,000 seeds) per acre, can be done by: (1) hand—efficient on small areas of disked strips or plowed furrows: one man can cover 15-20 acres per day; (2) hand-operated "cyclone" seeders—useful for broadcast sowing on tracts up to 200 acres: one man can sow about 20 acres a day; (3) spotting—specific number of seeds are placed in raked or hoed spots; useful for areas under 200 acres: with 1,000 spots per acre, one man can sow 2-4 acres daily; (4) airplanes or helicopters—a light plane can cover up to 1,500 acres per day and a helicopter 3,000 acres; and (5) tractor-drawn machines—several models are available which prepare a seedbed and sow seed in rows at a single pass. Sowing rates also vary with site, cover, seedbed preparation, local hazards such as livestock, stocking goals, and climatic conditions (Mann, 1966). If feasible, partial shading is helpful in spring and summer sowing (Varnell and Bennett 1966). Disking before seeding slash pine improves survival and growth and is preferred to furrowing, especially on wetter sites. Five years after seeding, stands averaged 5 feet in height where sites were burned, 7 feet in plowed furrows, and 8 feet on disked strips. The difference between the first and last is equal to at least a year's growth. Survival at the end of the fifth year, based on stocking at the end of the initial growing season, was 97 percent for furrows, 83 percent for disked strips, and 64 percent on burned areas (Russell and Rhame, 1960). Flooding and washing often cause excessive seed losses in furrows on wet sites. Insurance against adverse weather effects, as well as providing for superior growth, more than justify strip disking of sites for seeding. Malac (1960) found that disking with a heavy harrow or a fireline plow resulted in milacre stocking twice as high as in areas freshly burned or untreated. Stocking by the former methods was satisfactory, by the latter less than adequate. Sowing rates of I1/) pounds per acre are satisfactory. Annual plants provide the most favorable vegetative type for direct seeding following site preparation. Perennial grasses, especially sods, are less desirable, while woody plants offer severest competition to young seedlings. Dead ground cover or organic debris on the forest floor is also influential, for heavier accumulations, regardless of the type of debris, lower milacre stocking.

Silviculture of Slash Pine

In the flatwoods, site preparation is not required for establishment of a stand of South Florida slash pine by direct seeding except where saw-palmetto is dense, indicating the site may be fairly dry during periods of drought. For South Florida, Langdon (1957) recommended IVa pounds of treated seed, the treatment for 25 pounds of seed consisting of a mixture of 4 ounces of 50 percent Endrin powder, 10 ounces of Arasan-75, 2i/2 ounces of aluminum powder, and 1 quart of Dow Latex 512R diluted 10 times with water. Satisfactory seeding has been obtained in a burned-over pond that is usually under water during seasons of normal rainfall (Johnson, 1956). However, Mann and Derr (1965), M a n n (1966), and Miller (1957) cautioned against seeding sites where seed is apt to be submerged in water, including slowly draining surface water on uplands. Brief submergence weakens the repellents, and periods of several weeks or so sharply reduce viability. Stephens (1956) found new seed lost viability following 14 days of soaking in water at room temperature; year-old seed lost viability after any soaking. Hot water, above 95 °F, such as might be found standing in puddles in the summer, is especially damaging (Bengtson, 1955). Excellent guides for direct seeding of slash pine have been published by Mann and Derr (1964). Woods (1959a) also edited a symposium providing much useful information. Seed Grades Superior initial growth of seedlings of the typical species has been obtained with medium-size slash pine seeds, but the advantage is so small that sorting is not recommended (Shoulders, 1961a). One year after planting South Florida slash pine in the field, survival was significantly different, depending upon seed grades as determined by cone length. Large seeds gave the best survival (Langdon, 1958). Tree Improvement Genetics

Nature does its share in rehabilitation of tree quality following man's depredation through overcutting and other practices. For slash pine, in the portion of the species' range where climate —principally rainfall and length of growing season—is optimum, the trees grow faster than elsewhere, and the fastest growing of these dominate in numbers and may produce superior seed for the next crop. If some stems outgrow others when all are subjected to identical environmental conditions, trees inherently

Stephen F. Austin State College

superior in growth could result through natural selection. This is assumed to b& the case in the development of seed production areas for collection of cones from phenotypically superior stems. Trees not in the optimum climatic zone probably favor natural selection of traits associated with survival. To the north, cold winters result in more rigid selection for resistance to frost, with less stringent selection for rapid growth. Likewise, selection for drought hardiness can occur in areas where rainfall is deficient during critical periods in the life of trees. Seeds collected in drought areas may also be superior to local seeds in wetter climes. Hence, it is suggested that local seeds are not always best. A source in the optimum growth zone may be superior even when planted in other climates (Squillace and Kraus, 1959). Studies to date suggest that trees from the northern portion of the species' range can be moved successfully practically anywhere within the species' range. Movement of seed from coastal to interior areas or from south to north entails more risk, but the latter is not commonly done because of inherently slow growth of south Florida trees (Squillace, 1966). Self-fertilization in slash pine has been found to detrimentally influence height growth. Seeds from female flowers pollinated by pollen from the same tree, in one case, produced seedlings a foot shorter at age 5 than were those from cross-pollinated sources (Mergen, 1954a). Lone trees frequently bear heavy crops of cones, but the yield of viable seeds per cone is usually low. A seed orchard spacing of 30x30 feet has been found most conducive to flowering and seed production (Texas Forest Service, 1966). In reproduction harvests, the effects of selfing likely can be reduced by leaving small groups rather than isolated seed trees. In silvicultural cuttings, trees of good phenotypic qualities should be left to enable cross-pollination of stems with favorable characteristics. The collection of cones for seed should be limited to good phenotypes; in other words, the decision to gather cones from certain trees should be influenced less by economy in cone harvesting (e.g., ease of climbing) and more by the characteristics of the future crop (Dorman, 1966; Barber, 1965). Foresters should be aware of the occurrence of abnormally formed seedlings. Mergen (1958) found those due to polyploidy rare, a frequency of 0.0002 percent. External symptoms of polyploid cells are depressed root and shoot growth, empty seeds due to abortive pollen grains, and low capacity for survival, especially in the forest (Fig. 21).

Silviculture of Slash Pine

Figure 21â&#x20AC;&#x201D;Abnormal slash pine seedlings, due to polyploidy (from Mergen, 1958).

Stephen F. Austin State College

50 Inheritance

Mergen, Snyder, and Burley (1966) cite literature showing geographic variation in slash pine for rate of seed germination, insect resistance, survival and height growth, and various morphological characters; latitudinal and longitudinal gradients have been found for wood specific gravity, but there appears to be little variation in resin yield (Barrett and Bengtson, 1964). Mergen and co-workers found variations from north to south among numerous needle, twig, bud, and cone characters from several island, coastal, and inland collections. Evidence to date, however, indicates less variation in slash pine than in other southern pines (Wakeley, 1961). A 22-year-old plantation of 7 sources in central Louisiana revealed no significant differences in growth and yield, fusiform infection, specific gravity, or tracheid length (Derr and Enghardt, 1960). Greene (1962a) detected no significant differences in survival, height growth, and fusiform infection between 5 Georgia seed sources. Barrett (1963) found slash pine gum flow unaffected by seed origin. An introduction of slash pine into the lower peninsular area was found to be significantly different in survival and growth among 5 sources 3 years after planting.1 Trees more than 3 feet tall ranged from 6 to 46 percent, and heights among the 5 sources varied from 2 to 3 feet. Nantucket pine tip moth infestation varied by source of stock but seemed to center on the more vigorous or faster-growing trees (Langdon, 1958a). In addition to survival and growth, characteristics of slash pine demonstrated as inherited include crown width, stem form (Fig. 22), oleoresin yield and viscosity, specific gravity, tracheid length, etc. (see Table 8) (Barber, Dorman, and Jordan, 1955; Echols, 1955; Mergen, 1955b; Jackson and Greene, 1957, 1958; Squillace and Dorman, 1959; Squillace and Bengtson, 1961; Jackson and Warren, 1962). Susceptibility to chlorosis among seedlings in a nitrogen-deficient nursery, chlorophyll deficiencies of the cotyledon, and hypocotyl color were genetically controlled, according to studies by Snyder, Squillace, and Hamaker (1966). (Among studies concerning variation in tracheid lengths and fibril angles in slash pines are: JarBergs, 1963; Hiller, 1964; Jackson and Morse, 1965). Breeding for desired characteristics is, therefore, possible. A slash x shortleaf cross shows more resistance to the Nantucket pine tip moth and grows faster than shortleaf pine 'The results hold for 5 years.

Silviculture of Slash Pine

(Grigsby, 1959). These hybrids also show great promise for developing rust resistance provided both parents are properly selected to incorporate the high resistance of most shortleaf pines and the moderate resistance of some slash pine selections (Jewell, 1961, 1966). The principal hybrid involving slash pine is the slash x longleaf cross. These hybrids have produced one tree with the typical longleaf pine grass-stage habit to two trees which make good early height growth of 1 to 4 inches the first year (Harkin, 1957). Seven-year-old longleaf x slash hybrids planted in central Louisiana demonstrate desirable characteristics of both parent species, resembling longleaf pine in form and branching habit but starting height growth immediately and growing almost as fast as slash pine. They appear less susceptible than their parents to the brown spot needle blight of longleaf pine and the fusiform rust of slash pine (Derr, 1966). Vigorous and wellformed hybrids of longleaf and slash pines are being tested in Texas, and crosses of slash and loblolly pines have shown some promise of drought resistance (Texas Forest Service, 1961). Nursery bed selection of superior phenotypes has been discussed (see Planting).

,•,

,: , - > ; ; f-? '

•-',,-

* •")" j" ';-

» » - f ^-^s --->•.

;'^f:"'?^*>:'"f:.;.,\e 22—Inherited crook in slash pine.

Stephen F. Austin State College

TABLE 8â&#x20AC;&#x201D;HERITABILITY ESTIMATES OF DIFFERENT TRAITS IN 15-YEAR-OLD SLASH PINE AT LAKE CITY, FLORIDA (SEFES, 1961) Trait Oleoreein yield

Heritabihty Method used to estimate heritability percent' Selection experiment 45 Parent offspring regression of cross-pollinated progenies 56 Female parent offspring regression of wind-pollinated 62 progenies Components of variance with all wind-pollinated progenies 45-90 Components of variance among clones 2 90

Wood specific gravity 21-42 2

Components of variance using wind-pollinated progenies Components of variance using cross-pollinated progenies Components of variance from clones of rooted cuttings

18-35

Components of variance using wind-pollinated progenies Components of variance using cross-pollinated progenies

48 31

Height

8-16 13

Diameter at breast height

29-58 33

Crown width

24-48

Bark thickness

33-67

Oleoresin

viscosity

Components of variance using wind-pollinated progenies Components of variance using cross -pollinated progenies Components of variance from clones of rooted cuttings

8-16

Summerwood percent Cubic-foot volume

12 57 58 100

Oleoresin exudation pressure

Needle length

Needle divergence

Needles per bundle

Needle bundle volume

Fascicle sheath length

Bud scale length

Components of variance using wind-pollinated progenies Components of variance using cross-pollinated progenies Components of variance using wind-pollinated progenies Components of variance using cross-pollinated progenies Components of variance using wind-pollinated progenies Components of variance using cross-pollinated progenies Components of variance using wind- pollinated progenies Components of variance using cross-pollinated progenies Parent offspring regression using wind-pollinated progenies and clones Parent offspring regression using cross-pollinated progenies and clones Parent offspring and clones Parent offspring and clones Parent offspring and clones Parent offspring and clones Parent offspring and clones Parent offspring and clones Parent offspring and clones

regression using cross-pollinated

progenies

regression using cross-pollinated progenies regression using cross-pollinated progenies regression using cross-pollinated progenies regression using cross-pollinated progenies regression using cross-pollinated progenies regression using cross-pollinated progenies

'Narrow sense heritability unless indicated otherwise. Only additive genetic effects are included. 3 Broad sense heritability includes nonadditive genetic effects (dominance and epistatic deviations) in addition to additive ones.

Vegetative Propagation

Many of the same techniques applicable for propagating longleaf pine are satisfactory for slash pine, and a greater percentage of grafts "take." Johansen and Kraus (1958) present details of techniques. Cuttings Mergen and Rossoll (1954) illustrate techniques for rooting of vegetative cuttings. Pine cuttings, especially from older trees, may be difficult to root because of the "shock" sustained when sections are removed from

Silviculture of Slash Pine

trees. Apparently large amounts of carbohydrates are needed to form callus tissue and to develop roots on cuttings that temporarily must rely on stored foods within tissues for further development. There is little reason to root cuttings from seedlings, as only fairly large trees exhibit the characteristics that one would generally wish to propagate. However, cuttings from 2- and 3-year-old trees were successfully rooted when taken in January, trimmed to 8 inches, and wounded at the base by slicing 2 inches of bark from one side. Cuttings taken during other months give highly inferior rooting. It is conjectured that food storage and consumption during the dormant and growing seasons may influence rooting (Reines and Bamping, 1960), although no statistical correlation was established between rooting response and carbohydrate level of slash and loblolly cuttings (Reines and Bamping, 1962). Cuttings collected! in June rooted well for Curry (1943) when soaked for 24 hours in a mixture of 50 ppm traumatic acid, 10 ppm Vitamin B,, complete nutrient solution, and 5 percent sugar, and dusted with Hormodin No. 2 just before planting in well-drained sand. Air temperatures were maintained at 75 to 90 째F and humidity was kept high. Air Layering Air layering, illustrated in Figure 23, reduces the "shock" sustained by cuttings. Air layers are left on trees until rooting is satisfactory. If necessary, water may be added with a hypodermic syringe. Roots arise from the basal part of the girdle. Mergen reported 85 percent "take" in 5 months. Upon rooting, layers are cut from parents, potted, watered, and fertilized with 1 pint per pot of a 3 percent solution of about 8-10-20 formulation. Height growth does not occur until severance, but it is then rapid due to the nutritional supplement. Hoekstra (1957) was able to increase the number of (1) rooted layers on 6- and 23year-old trees treated in July and September and (2) roots per rooted branch by increasing indolebutyric acid concentration in talcum powder up to 1.2 percent, but no higher. July is the optimum time for rooting (Fig. 24). It is noteworthy that trees 23 years old gave satisfactory rooting. Greenhouse growth is superior to the nursery bed only if air layers are made in the fall. Distal tips of branches in the upper third of the crown are perhaps the best. Napthaleneacetic acid growth regulator treatments killed branches. Greene (1962) air layered lateral and terminal branches of 4-year-old seedlings. Laterals rooted better than terminals, but all were making rapid symmetrical growth 3 years after out-planting, indicating air-layered branches of slash pine will develop into straight trees. Grafting1 Grafting, the main technique employed in vegetative propagation, may be intra-specific or inter-specific. Southern pines are successfully grafted with cleft, side, veneer, soft-tissue, bottle, bark-patch, and bud grafts. The 'See Mergen and Rossoll (1954), Mergen (1954, 1955a), Nienstaedt et al. (1958), and Johansen and Kraus (1958) for details.

Stephen F. Austin State College

Figure 23â&#x20AC;&#x201D;Air layering a slash pine branch: a '/$- to '/2-inch ring of bark and cambium is removed, the wound is wrapped in moss, and waterproof plastic is wrapped around the ball of moss and fastened tightly with tape at each end (from Mergen, 1955). widely used cleft graft "takes" when made any time of year, but success is greatest for spring treatments (Perry, 1955). Bottle grafting can be used in the greenhouse any time of the year. Scions can be obtained from mature trees for field grafting on 2- to 3year-old stock in plantations in early February. These are shaded with a sack over a post during the hottest part of the day. To bottle graft, cuts

Silviculture of Slash Pine

Figure 24â&#x20AC;&#x201D;Rooted air layers from 6-year-old slash pine made in July using 1.2 percent indolebutyric acid (from Hoekstra, 1957). are made in the side of scion and stock in the current year's growth. Cambium layers are matched, and scion and stock tied firmly with rubber grafting bands, coated with wax; then the scion is inserted into a 6-inch glass vial filled with water. Ferbam added to the water prevents fungi and bacterial growth. After 6 weeks and at 2-week intervals thereafter, the stock stem and branches are cut back about 3 inches. Using that technique, Greene and Reines (1958) grafted slash on loblolly pines. Transferring grafted plants from greenhouses to the field causes a "shock" frequently never overcome. Pot-grown grafted trees additionally are often root-bound, the roots continuing to grow in circles after outplanting in seed orchards, even though the pot has been removed. Windthrow is then severe. Survival of slash pine grafts in the field is improved appreciably by fertilizing with 1 pound of a 5-10-5 formulation (or approximate ratio) broadcast at time of transplanting around trees within a 15to 18-inch radius, leaving a small circle of about 4-inch radius around the stem to prevent possible burning. Survival is further aided by mulching fertilized trees with pine needles. The fertilizer improves vigor of the rootstock and thus hastens healing at the graft (Allen and Scarbrough, 1961).

Stephen F. Austin State College

Cone-bearing twigs of slash pine grafted in August retained cones and flowered again the following January. Thus, two sets of cones on 8-month-old grafts are evidence that cone-bearing scions may continue to flower uninterruptedly (Perry, 1955). Possibly, however, the primordia was laid down prior to severance of scion, as the majority of scions stop flower initiation after grafting and do not resume flowering for 2 or more years. Stock overgrowing the scion often gives rise to a flattened milk-bottle shaped stem which dies the first year or so after transplanting to seed orchards, Perry (1960) noted the high correlation between the absence of healthy branches on the stock and the presence of overgrowth and, therefore, reasoned that a phloem block is induced as a result of grafting. Stock growth matches the scion growth as long aa food supply to the stock is adequate, but when the phloem is blocked, downward food movement is interrupted until normal phloem growth is established. Although firstyear pruning should be designed to force the development of the scion, for slash and loblolly pines especially, some healthy "feeder" branches should be left on the understocks until the graft-union has completely healed. Then, after several years in the field, the feeder branches on the stock can be removed. When scion material must be collected at a great distance from the place of grafting, shipping and storage of the cuttings until use is important. Perry and Wang (1957), working with slash and loblolly pines, recommend wrapping cuttings in the shade immediately upon severing from source trees. Large turkey-size polyethylene bags, with 15 to 20 ^-inch holes, are used. As water of condensation retained within the container serves to magnify the sun's rays, it is essential that the wrapped stock be shaded. A handful of sphagnum moss immersed in water and then squeezed to release free water and placed loosely among the cuttings in the plastic bag permits air circulation and serves as a humidifier, keeping the relative humidity at 100 percent. The bags of cuttings are placed in perforated boxes and are kept cool but not permitted to freeze. Rooting Dwarf Shoots The use of dwarf shoots (small needle bundles or foliar spurs) for propagating slash pine has been explored by Reines and Me Alpine (1959). Removing these short shoots does not damage parent trees, in contrast to propagation by cuttings. The dwarf shoots sometimes arise in the axil of a scale leaf borne on the branch. Needles appear only on the spur and, with the needle bases, are covered by bractlike scales.. After a month or more in greenhouse sand cultures, roots originate from finger-like protuberances of the callus, although excessive callus impedes root growth. Buds develop from the apical meristem in advance of root development, but only rarely do new stems form. Those that first break express no apical dominance, but are branched and broad-crowned. Soon, one of those branches assumes dominance, and the progeny takes on the appearance of a typical seedling. Individual needles may likewise be rooted, accomplished most easily when inserted 2 inches into sand, given 24 hours of light, and regularly atomized (Zak and Me Alpine, 1957; Reines and Me Alpine, 1959). While

Silviculture of Slash Pine

needle bundles rooted more readily from 3-year-old than 18-year-old slash pine trees, about 30 percent of those bundles collected in December from the older age class rooted (Reines, 1963). Slash pine, believed superior to loblolly pine in its ability to root, established radicals most readily in January. The capacity, diminishing until May, is aided by Rootone growth stimulators (Reines and Damping, I960). Sexual Propagation

Stages of development of female strobili, covering about 15 days in the Coastal Plain and 30 days in the Georgia Piedmont, are pictured in Figure 25. Stage I is the best time to bag for controlled breeding; Stage II represents the latest satisfactory time. Optimum development for pollination occurs in Stage III, and in Stage IV bags may be safely removed. Unpollinated strobili remain in Stage III for longer periods than those which have been pollinated. Bagging should be delayed until strobili are recognizable (Snow, Dorman, and Schopmeyer, 1943; Greene, 1959). VanHaverbeke and Barber (1961) failed to significantly increase flowering by changing the angle of slash pine branches. Increasing the degree of down sweep of branches did decrease branch elongation. Annually fertilizing heavily thinned, cultivated 22-year-old slash pine in central Louisiana with 1,000 pounds per acre of 15-25-10 markedly increased female flower and cone production. Flowering was related also to March-through-July rainfall in the previous year and to the size of the flower crop 2 years earlier, with more flowers 2 years after a poor crop and vice versa (Shoulders, 1968). Injurious Agents in Seed Orchards

The actual yield of sound seed in seed orchards in any one year may be less than 50 percent of the potential due to insects, disease, birds, and rodents (Merkel, 1961). The most serious injuring agents are discussed below. Bark Beetle

A bark beetle, Pityophthorus pulicarius, damages scions of grafted trees. (The insect, 1.3 to 2 mm long, usually attacks tips of dying pines and branches in the process of natural pruning.) The symptom of its presence is frass pushed out as it bores into tips at needle bases or through old needle scars.

Stephen F. Austin State College

N Figure 25â&#x20AC;&#x201D;Stages of development of female strobili; Stage I (upper), Stage II (lower left), Stage III (lower right) (from Snow, Dor man and Schopmeyer, 1943).

Silviculture of Slash Pine

Needles die, beginning at the bottom of the scion. The life cycle of the insect is less than 2 months. Eggs are laid in the pith, larvae feed in wood, and adults bore through the bark to the outside. Attacks are most serious in March and April just above the union in old-growth of scions bottle-grafted in January and February. A relation is apparent between the source of the scion and its susceptibility to attack (Smith and Mergen, 1954, 1954a). Benzene hexachloride is a recommended insecticide. Thrips

Thrips feed on scales and bracts of flowers and conelets, leaving tiny, barely visible punctures and abrasions marked by beads of resin. Severe injury causes necrosis of scales and bracts, often shriveling the whole flower. The dark brown or black insect, 1/16 inch long, is found on vegetative buds in early January; on female flowers, flower buds, and vegetative buds during February, and may continue to appear on young cones and vegetative buds until mid-May. Shoots are attacked but not damaged (Ebel, 1961). Worms

Coneworms and seedworms, of the genera Dioryctria and Laspeyresia, respectively, may be very prolific in seed orchards. While the number of cones infested by the two is about the same, coneworms cause the loss of nine times as many seeds as do seedworms (Merkel, 1961). Studies in north Florida showed coneworms can be controlled by hydraulic sprays of BHC (4 Ibs. gamma isomer/100 gal. water) or Guthion (1.5 Ibs./lOO gal. water) applied during March 15-31, May 1-15, June 1-15, and July 10-20. A single application of the Guthion formulation between May 5 and 15 controlled seedworms (Merkel, 1964). Cone Rust

Heavy damage due to Cronartium strobilinum, a cone rust pathogen, has been observed in north Florida, south Georgia, and the Gulf Coast of Alabama and Mississippi. Because live oak is the principal alternate host, seed orchards and seed production areas should be restricted to sites beyond the range of this and other evergreen oaks. Conelets are susceptible to infection

Stephen F. Austin State College

from the time of twig budding until just after the period of pollen receptivity. The rust is increasing in frequency of infection due to an increase in slash pine, its favored host. Ferbam is recommended for control during the period of susceptibility in areas of high rust hazard. It is used at a concentration of 2 pounds of the 76 percent wettable powder per 100 gallons of water with a spreader-sticker at 5-day intervals from the time female strobili begin to emerge and continued for 5 or 6 applications (Matthews, 1964). Ferbam also stimulates pollen germination. Other fungicides tested are toxic to strobili. The favorable effect of Ferbam may be due to the presence of iron in the formula, as slash pine pollen germinates best when in the presence of organic ferrous complexes (Matthews and McLintock, 1958; SEFES, 1959). Intermediate Management Thinning

Thinnings remove "worked-out" naval stores trees and diseased or otherwise undesirable stems to open the stand for increased diameter growth. Crowns should be maintained at one-third the total tree length. Sapling and pole-size stands may require thinning as frequently as every 4 years, and sawtimber stands every 10 years. A decision as to the final product (e.g., sawtimber or pulpwood) should be made early as it influences the intensity and type of thinnings required (McMinn, 1965). However, until effective economical methods for control of annosus root rot are developed, thinnings may have to be limited to some extent (Bennett, 1965b). Also, Shoulders (1967) reported volume growth of slash pines of pulpwood and sawlog size was decreased by heavy thinning (leaving insufficient -stocking for maximum growth) and disking (probably disrupting root systems near the surface and thereby reducing water and nutrient uptake). Fertilization increased both volume and diameter growth, but diameter growth, although boosted by heavy thinning, was decreased by disking. Density

There is a rather weak relation of cubic foot volume growth to stand density in young, unmanaged, evenaged stands regen-

Silviculture of Slash Pine

erated after logging and developed in the absence of fire- Hence, for flatwoods protected from fire, maximum growth occurs at less than full stocking and is least on poorest sites (Gruschow and Evans, 1959). In older forests, volume growth is equal over a wide range of stocking. Lower stand density than that producing maximum cubic foot growth favors maximum value production by reducing the time required for growing large trees. Density increases with time in all stands having less than 100 percent theoretical stocking. The rate of increase tends to be greatest in the middle densities of 40 to 50 percent stocking (Gruschow and Evans, 1959). In Piedmont plantations, competition begins as early as the third year after planting when spaced at 6 x 6 feet; but height growth is not affected after 7 years. Thus, alternate row thinning when stands begin to close is recommended to increase growth (Nelson, 1952). Crowns

The importance of maintaining 35 to 40 percent crown length : height ratios was illustrated on a deep loamy sand, with SI 76, and in a stand so dense that crowns averaged less than one-fourth of tree heights. Reducing basal area from 85 to 55 square feet per acre in trees over 5 inches dbh failed to provide a satisfactory response in the ensuing 5 years. Even the dominants grew only 0.12 inch dbh and Vs foot in height per year. Growth of intermediates and suppressed trees in this 45-year-old stand was virtually nil; after 5 years of release crowns were still less than 70 percent of the length required for desirable growth, and height increment was one-half of normal (Bennett, 1955a). Such dense stands, perhaps, should be clearcut and replanted, as in this case, 3 to 5 cords per acre were sacrificed in the 5-year post-thinning period. Thinning in dense, sawlog stands does not result in an increase in crown length : height ratio, as height growth is not likely to be increased to any measurable degree. However, loss of crown at its base is prevented and the ratio thus maintained. A marked buildup in the ratio results only if thinning is done during the period of greatest height growth, perhaps up to age 30. Since after age 35 responses in height growth are negligible, it is desirable that this period be entered with sufficient crown for optimum diameter growth through the years which

Stephen F. Austin State College

follow to the end of the rotation. Bennett (1960) found the crown length : height ratio upon thinning to vary very little between sites. The shape of the crown of slash pine may change from a cone to a paraboloid during the younger years, although few stems ever have conical crowns. That also indicates the opportunity for increasing crown area during restricted height growth is limited, even though crown density and needle length may increase after release. Since crown volume is not increased by thinning, growth is stimulated by reduction in competition for moisture and nutrients and, possibly, by photosynthesis increasing as a result of additional light reaching needles on the residual crown. For dominant stems, photosynthesis can increase little, as there is negligible change in the amount of light getting to the foliage. A principal concern of the forester working with sandy soils is the accumulation and conservation of organic matter. That is particularly difficult in the South where warm temperatures hasten oxidation and prevent, even under favorable conditions, the accumulation of more than lJ/2 percent organic content (in contrast to 5 percent in colder climates). Other than by encouraging hardwood invasion, this is best done by thinnings intended to reduce the canopy vertically rather than horizontally. Thus, in pine stands, suppressed trees of understories should be cut so that as little of the ground as possible will be exposed to the sun's rays. Invasion of grasses as well as decomposition of plant remains are thereby retarded, and this is important nutritionally because of the prevalent deficiency of available phosphorus, much of which occurs in the organic matter of the surface soil. The amount of mineral matter leached may be greater than that retained in the biotic life-decay cycle (Odum, 1960). Basal Area

The basal area of a fully stocked stand at a given average diameter, ascertained from yield tables for second-growth southern pines, assumes that harmonized yield data are reliable and that the area required by the average tree is a function of the mean diameter. Unit area for the average tree can then be converted to the number of trees per acre and to basal area. For slash pine, the relation to dbh of trees of average basal

Silviculture of Slash Pine

area varies but little with site and age in fully stocked stands under 60 years old. Stahelin's (1949) Table 9 for thinning is derived from the equation: x / d ,2 A V 0.044765 + 0.073895d ) where X = the basal area in percent of full stocking for trees 2 inches dbh and over, and d = dbh. Hence, to thin to a given density, or percent of full stocking, basal area is computed for the corresponding desired density. If the average tree is 10 inches dbh and desired density is 80 percent of full stocking, the basal area cut would equal 162.8 â&#x20AC;&#x201D; 0.8(162.8) = 32.6 square feet. In timber marking, the tally of trees to be cut is entered into proper diameter class columns alongside an original stand table. It is then easy to estimate whether the average diameter of the residual stand will be the same as that of the original stand, and to make adjustments in the basal area cut. Marking continues until the desired basal area per acre is reached (Table 9). Thinning a 20-year-old plantation in Georgia, reducing basal areas from 118 and 138 to 85 square feet, increased the basal area growth rate for about 8 years (Jackson, 1968). TABLE 9. BASAL AREA PER ACRE FOR 100 PERCENT STOCKING OF SLASH PINE (after Stahelin, 1949) Average dbh Inches

4 5 6 7 8 9 10 11 12 13 14 15 16

Basal area Sq. ft. 138.2

145.7 151.1 155,1 158.3 160.8 162.8 164.5 165.9 167.2 168.2 169.2 170.0

Fusiform Rust The sanitation value of removing fusiform-infected trees is negligible because of the impossibility of eradicating the alternate host. From a risk standpoint, trees with stem cankers extending more than 50 percent

Stephen F. Austin State College

of the circumference of the trunk, deeply sunken canker faces, or trunks with bends at the canker are harvested. Those with branch galls more than 15 inches from the trunk are good risks and should not be removed because of the rust (Lindgren, 1948). Derr and Enghardt (1957) found thinning to 70 square feet basal area per acre leaves pole-size stands in the Gulf Coast area too open to avoid windthrow from hurricanes. Generally, where not thinned so severely, plantations on well-drained soil suffered little loss; breakage was most apparent where more than 50 percent of the bole circumference was cankered by fusiform rust or where low cankers occurred on windward sides of trees. Pre-commercial Thinning

Pre-commercial thinning of slash pine is frequently desirable. For instance, on a 6 x 8-foot spacing, basal areas may exceed 125 square feet per acre when trees average less than 6 inches dbh. One-sixth of the stems may be less than 5 inches dbh, the minimum merchantable size. When most trees reach merchantable size, stand basal areas approach 150 square feet per acre, and stagnation has likely occurred. For wide spacing, pre-commercial thinning is not needed. Pre-commercial thinning is recommended for crowded stands when trees are 10 to 18 feet tall. Thinning to 700 stems per acre hopefully provides an increase in yield sufficient to cover the cost of treatment. Stands thinned to 400 trees per acre at 8 to 10 years of age give an operable pulpwood cut before sawlog size is reached. Lighter thinningâ&#x20AC;&#x201D;to between 700 and 800 stemsâ&#x20AC;&#x201D;yields considerable pulpwood before trees reach sawlog size. By age 22, 25 cords are attained in stands thinned early to 200 trees per acre (15 x 15 feet) (Gruschow, 1949). McMinn (1965) reported the history of a 35-year-old slash pine stand (SI 90, 50-year basis) in north Florida which was thinned at age 7. Four levels of thinning were used, leaving 700 (light), 400 (moderate), and 200 (heavy) residual trees per acre, with an unthinned check plot of 3500 trees per acre. The lightest thinning yielded the greatest merchantable cubic-foot volume for a wide range of rotation ages, whereas the heaviest thinning resulted in greater sawtimber volume and the best potential net return from naval stores (Table 10). Thinning between ages 5 and 12 is recommended for naval stores stands to assure good turpentine trees at age 15. As a rule of thumb, minimum distance of 10 feet between trees provides 200 trees per acre. After dominants are selected, all trees

Silviculture of Slash Pine

TABLE 10. TOTAL MERCHANTABLE-WOOD YIELD BY PRODUCT AND THINNING TREATMENT (McMinn, 1965) Degree of thinning

Product

Volume

Heavy

Pulpwood Sawtimber Topwood

12.3 cords 12.9 mbf 6.3 cords

Moderate

Pulpwood Sawtimber Topwood

18.9 cords 11.5 mbf 9.4 cords

Pulpwood Sawtimber Topwood Pulpwood Sawtimber Topwood

40.2 cords 9.1 mbf 10.7 cords

Light Check

44.6 cords 4.5 mbf 4.8 cords

within 5 feet are removed. Thus, the proportion of crown length and width to height is maintained as follows (Ackerman, 1929) : Age

Length

Width

60 50 40

10 15

20 17

Heavy windfall, however, occurs in previously dense stands opened to this degree. McMinn (1963) reported on results of pre-commercial thinning in Florida in a slash pine stand originating from a bumper seed crop in 1933. Half of the stand, containing 3500 trees per acre, was thinned to 1200 trees per acre (approximately 6 by 6 feet) in 1944. Two merchantable cuts have been made since that time in the thinned portion. After 29 years, the thinned half of the stand had produced 29.8 cords per acre (merchantable cuts plus standing timber) and the unthinned portion, 29.2 cords per acre. Thus, while thinning did not appreciably increase total merchantable wood production, merchantable wood was available earlier and periodically, and the larger stems in the thinned portion can be tapped for oleoresin before the harvest felling. Studies in Alabama indicate early thinnings (at age 8 or 12) reduce total pulpwood yield (Livingston, 1964). Pruning

Where pruning is profitable, Garin (1965) suggests 150 fast growing, well-formed trees per acre be selected, providing about 125 trees by the time of harvest. Trees selected should be

Stephen F. Austin State College

free of defects, in the dominant and codominant classes, and spaced 15 to 25 feet apart. Pruning up to 80 percent of the live crown has little or no effect on height growth of slash pine. Bennett (1955) reported, however, that diameter growth of 5-year-old trees is significantly reduced when more than half of the live crown is pruned. For trees 11 years old, removing 35 percent resulted in significant reductions. Pruning, therefore, is recommended at age 5 to 6, or when trees are 15 to 18 feet tall and the crown ratio is 85 percent or more. Eight feet should be treated at this time, provided the crown ratio is not reduced to less than 50 percent. Then, at age 10 to 12, or when trees are 33 to 36 feet tall, and the crown ratio about 60 percent, limbs are pruned to 17 feet. Again a 50 percent crown ratio is maintained. No more than 35 percent of the live crown should be removed in either treatment. Twophase pruning gives more clear lumber than does a single operation, as the diameter difference in the lower half-log between 5- and 11-year old trees is about 4 inches. The knotty core thereby is held to a minimum diameter of 5 inches (Bennett, 1956). Also, as knots are smaller in younger trees, they heal faster. Boggess' (1950) observation for 6-year-old trees in south Alabama are similar to those of Bennett, except that pruning 50 percent of the total height reduced height growth. Garin (1955), noting that slash pines keep lower branches up to 25 years, about half as long as loblolly and shortleaf and equal to longleaf pines, suggests pruning to 17 feet in three steps, but never cleaning more than half the total height. Pruning is effective in aiding recovery of ice-bent slash pines. If pruned to the leader within one month of a storm, most trees bent at angles of from 30 to 90 degrees straighten to less than a 10 degree lean. Since unpruned trees bent less than 60 degrees straighten relatively well, Roberts and Clapp (1956) recommend pruning only if the angle from the vertical exceeds that. Diameter growth losses are expected for the first year only. Pruning is advisable for branches on which fusiform rust galls occur within 15 inches of the main stem. Bud Pruning European bud pruning, removing all lateral buds around the terminal bud from small trees after each growth flush, to produce knot-free lumber is ineffective. Rowland (1950) found dbh growth decreased the second

Silviculture of Slash Pine

year after treatment of 2- and 3-year-old stems. Each year's needles on the branches retained close to the ground are longer than those of the preceding year, indicating that during the early life of pruned trees, the food-producing capacity of lower branches is supplemented by needles along the main stem. Fire Pruning Fire pruning is not recommended. Natural pruning of unburned 9year-old trees 23 feet tall caught up with that on burned trees in about 3 years. A loss of % year's height growth is sustained by burning (Bruce, 1952). Undesirable Species Control

Slash pine stands generally have little invasion of undesirable hardwoods except in drainages, although the species responds well to release (Malac, 1962). Control includes chemical, fire, and mechanical techniques. Smith (1963) notes that prescribed burning is often impractical, because the soil usually is too wet for winter burning, and summer fires hot enough to kill the shrubs are likely to damage seed trees. He achieved good control by cutting stems near groundline and spraying the fresh stumps with 2,4,5-T in diesel oil. Prescribed Burning Endurance

The ability for pole-size and larger slash pines to endure hot fires arises from the insulating capacity of bark. While the outside bark temperature may reach 1000 째F, the cambium heats only to 150 째F. However, the growing tissue maintains this temperature 8 to 10 minutes after the outer bark has returned to normal (SFES, 1960). The heat tolerance of 1-yearold seedling roots is between 116째F and 120째F (Gentile and Johansen, 1956). Roots are about as resistant to fire damage as above-ground parts. Slash pine mortality for trees up to 6 inches dbh increases as the amount of crown burned (expressed as the percent of crown length) increases. McCulley (1950) states that, with equal crown burning, mortality decreases linearly with increasing diameter. Kill is greater when some needles are destroyed than when none is consumed. Slash pines more than 5 feet tall seldom die unless more than 70 percent of the crown is burned. Prediction data, helpful for salvage decisions for burned-over stands, are given in Figure 26 and Tables 11 and 12.

Stephen F. Austin State College

CROWN SCORCH LINE

STEM CHAR

LINE'-

CROWN CONSUMPTION LINE

BARE

STEM CHAR

LIMBS

LINE

Figure 26â&#x20AC;&#x201D;Types of crown and stem damage. In figure at right, the stem char line is higher than the crown consumption line. The tree on the left would live; the one on the right, in all probability, would die (from Storey and Merkel, 1960). TABLE 11. MORTALITY

BY DIAMETER CLASSES A WINTER FIRE (after Storey and Merkel, 1960)

Dbh

Longleaf

Slash

FOLLOWING

Longleaf and slasl

Percent

4- 6

7- 9 10-12

28 22 21

30 24 21

31 28 17

TABLE 12, MORTALITY BY STEM DAMAGE CLASSES (after Storey and Merkel, 1960) Stem damage class Percent char

Heavy (81-100) Medium (61-80) Moderate (41-60) Light (0-40)

Longleaf

88 53 9 0

Slash Percent

Longleaf and slash

88 24 13 0

88 39 11 0

In a Louisiana test, prescribed fires running against the wind in late winter did little damage to slash pines at least 8 feet tall. Over one-half of the seedlings under 3 feet were killed (Mann and Rhame, 1955). In the north Florida flatwoods, some trees over 12 feet tall were killed by headfires in litter fuel types, but very few trees less than 11 feet were killed by

Silviculture of Slash Pine

backfires. Many trees less than 11 feet tall in a grass fuel type, however, had height and diameter growth reduced with headfires. Hence, slash pines should be 10 to 15 feet tall before prescribed burning is attempted, at which time they will be about 2 inches dbh, or 4 to 8 years of age (Lemon, 1946). South Florida slash pine is more fire resistant than typical slash pine (Ketcham and Bethune, 1963). Also, the fire resistance of South Florida slash pine seedlings may vary with seed source, partially due to variations in bark thickness (McMinn, 1967). Technique Prescribed burning for hardwood control is sometimes desirable early in the life of a stand, even before thinning, as undesirable trees are well established by the time pines are 10 to 20 years of age. Beyond that, the broadleaf stems are too large for control with prescribed fire. In the East Texas area, strip headfires in 20- to 12'0-foot bands are recommended for cutover pine-hardwood stands with basal areas less than 70 square feet per acre and where there is no fresh logging slash. Fires should be set when fuel moisture is 3 to 8 percent, relative humidity 20 to 40 percent, and the wind is steady at 1 mph from north or south. Burning may be done in fall, winter, or spring. In heavy to normal fuels in East Texas, only 45 to 60 work days per year are satisfactory; for light fuels, only 30 days (Silker, 1956, 1956a). Slash pine plantations require damper conditions—8 to 20 percent fuel moisture and 50 to 95 percent relative humidity. Fires are prescribed only for winter and spring, and when the wind is low — 1 mph — and steady from north or south. [Krueger and Pachence (1961) have analyzed monthly wind directions for prescribed burning at various locations in the Southeast.] In plantations with heavy draped fuel, backfires only are employed. Otherwise, the initial burn is against the wind, and burning is then repeated wih headfires in 10- to 40-foot wide strips. For all of those prescriptions, the flame is kept at a height of 3 feet or less. Stands should not be burned if air temperature is above 50 °F, or 40°F for plantations with heavy, draped fuel (Silker, 1956a, 1961). Like other southern pines, this species tolerates a fire of much greater intensity when temperatures are just above freezing than on warm summer days (Byram, 1948). Other Effects Hogs apparently avoid burned areas for reasons as yet unknown. Possibly (1) rooting is made difficult by the drier ground of exposed sites, (2') burned areas are unfavorable habitat for grubs and worms, or (3) ashes irritate delicate snouts (Mann and Whitaker, 1955),. Tims, among stands less than 4 years old in Louisiana, hogs kill as many slash pines on unburned areas as fires do on burned sites.

Stephen F. Austin State College

No erosion follows prescribed burning in coastal flatwoods, as litter and humus are not consumed and the land is relatively flat. When ponds or swamps dry out and organic matter above the mineral soil is destroyed by wildfire, new feeding roots develop (Heyward, 1934). Integrated Management Gum Naval Stores Todd and Yoho (1962) point out that slash and longleaf pine, separately and in association, characterize the Florida peninsula and most of a coastal area about 100 miles wide extending from East Texas to South Carolina. The type, containing about 26 million acres, constitutes the naval stores belt which has supplied a large portion of the world's demand for rosin and turpentine since colonial times. Silvicultural Relations

For gum naval stores operations to be integrated with silviculture, only some of the trees are usually treated, and these over short periods. Two years is maximum in some cases, as insect infestations increase with declining yields beyond that time. Treatment for gum production should precede either final harvests or intermediate cuttings made a decade before the stand is to be regenerated. Naval stores operations are not recommended prior to pulpwood thinnings except when selective cupping is employed. If crown length : height ratios are less than 40 percent and diameter growth is slower than 8 rings per inch, thinning should generally proceed without a naval stores operation (Schopmeyer and Larson, 1955). The best criterion is the number of workable-size trees per acre. Trees 9 inches dbh (10 inches on poor sites) or larger are worked in selective cupping. These are selected 3 to 8 years prior to cutting to enable production of the highest possible quality and volume of gum commensurate with pulpwood, poles, piling, and sawtimber yields. Economic operations have been conducted in plantations 13 years of age and thereafter on 6 year cycles. Gum production probably averages 10 barrels per acre on 30 trees treated at each cycle (Jones, 1961). Growth and Yields' Current growth rate is reduced as a result of turpentining. Schopmeyer (1955) found that a, 26 percent loss for convenional front-face chip'See Bensrtson and Schopmeyer (1959) for EUm yield tables.

Silviculture of Slash Pine

ping is a function of wound width (Fig, 27). Yields of oleoresin are not correlated with concurrent growth, site index, or tree age (Bengtson and Schopmeyer, 1959; Schopmeyer, 1955).

11-25

Figure 27â&#x20AC;&#x201D;Bimonthly growth increments of turpentined and unturpentined trees during the first year of turpentining, showing accelerated growth reduction as the growing season progresses (from Schopmeyer, 1955). First-year gum yields with conventional 3/4-inch acid-treated streaks on slash pine depend primarily on diameter, but also to a lesser degree on crown ratio (Bengtson and Schopmeyer, 1959). Thus, trees with crown ratios less than 40 percent should be passed over for oleoresin production except where they are to be intensively streaked for a short period before harvesting, though this is probably economically unsound. In addition to size, the characteristics of high gum-yielding slash pines are determined by (1) size of radial resin ducts exposed by chipping, (2) number of resin ducts per square inch of fresh streak, (3) crown size, (4) viscosity of gum (Fig. 28), and possibly (5) exudation pressures within trees forcing gum outward. Schopmeyer (1953) states that high yielding trees have only one or two of those factors favorable, never all. Schopmeyer, Mergen, and Evans (1954) note that the product of the reciprocal of viscosity of the oleoresin,1 the number of resin ducts, and the size of the IBishop and Marckworth (1933) found reduced flow of resin in cold weather due to decreasing resin production and concentration within the tree, rather than to increased viscosity. From this they reasoned that the best time to harvest pines for papermakingâ&#x20AC;&#x201D;if resin in wood is important to the processâ&#x20AC;&#x201D;is during or immediately following a sudden sharp drop in temperature during winter.

Stephen F. Austin State College lOOr

S 60

^ 40 v 20

100

150

200 250 VISCOSITY

300

350

400

Figure 28â&#x20AC;&#x201D;The relation of gum yield to viscosity of oleoresin. Lower yields were associated with higher viscosities (after Mergen, Hoekstra, and Echols, 1955). ducts accounted for 83 percent of the variation in flow rate between trees. As air temperature has been held accountable for much variation within and between seasons, chipping is begun only when the average temperature for a 2-week period exceeds 60Â°F (Clements, 1961). In selection and breeding for oleoresin production, those criteria should be considered since viscosity and, consequently, gum yield are inherited (Mergen, Hoekstra, and Echols, 1955). However, since the number and size of radial resin ducts appear to be inversely related due to genetic linkage and change rapidly with increasing age, there is little opportunity to improve gum yield by breeding for these attributes. High gum yielders producing two and one-half times the normal flow have been found (Curry, 1943) (Fig. 29). Accuracy in prediction of gum yields may be improved by considering the crown length : height ratio in addition to dbh (Fig. 30). An increase in dbh of 1 inch increases gum yield by 27 barrels per crop of 10,000 faces: an increase of 0.01 inch in average width of annual rings in the last inch of radial growth increases yields by 11 barrels per crop. But increasing the crown length : total height ratio by 10 percent increases gum yields by 38 barrels per crop (Schopmeyer and Larson, 1954, 1955). The rate of flow of oleoresin during the first 24 hours after wounding1 also appears to be correlated with the annual yield. Acid Effect Repeated wounding at weekly intervals partially avoids crystallization of resin or distention of epithelial cells into the lumen of resin canals, thereby encouraging sustained flow. Sulfuric acid also enables more continuous flow as radial ducts are probably opened up by dissolving action. Resin in the ducts is released through the phloem by collapsing or disin-

Silviculture of Slash Pine

90r

30 29

28 <£ 27

70-

N 25 W5

24 23

50L

10 AGE

(YRS.)

AGE (YRS)

Figure 29—Effect of age on number (left) and size (right) of radial resin ducts in parent trees (after Mergen, Hoekstra, and Echols, 1955).

350

300

250 o K.

J200 O

• 150

100

DBH. ( I N )

Figure 30—The effect of diameter and crown length: height ratio on gum yields. The middle line on the graph represents the mean crown length: height ratio of the sample trees (from Schopmeyer, 1955).

Stephen F. Austin State College

tegrating the ray parenchymaâ&#x20AC;&#x201D;cells which occlude or line radial resin ducts. Killed tissue is limited to a zone of 3/4 inch as the cell sap effectively buffers the strong acid. Evidence that sulfuric acid does not stimulate internal resin production but, rather, enhances its flow has been advanced by Ostrom, True, and Schopmeyer (1958). Greater response to acid treatment is in otherwise low-yielding trees. In spite of higher gum yield with acid, food reserves in stems and root bark are greater in acid-treated trees than in non-turpentined and nonacid-treated stems (Ostrom and Waring, 1946). Methods Snow (1953), Bengtson (1959), and Clements (1960) recommend methods for efficient turpentining. Briefly, these include smoothing bark and attaching gutters and aprons with double-headed nails for convenient removal prior to logging. Two-quart or larger cups are hung on trees with single faces only, raising tins and cups at thel end of the first year. Bark streaks are made 3/4 inch high at 2-week intervals over a 16-streak period to trees 9 to 14 inches dbh (12 to 14 inches for peak yields). Chipping, rather than hacking, is employed to preserve the round trunk for future lumber, and 1 ml of 50 percent concentrated sulfuric acid is sprayed on the streaks. Growth is reduced if the face is wider than the tree diameter. (For highly intensive practice, iy4-inch high streaks and 65 percent sulfuric acid are used over shorter seasons, the higher streak being necessary because the strong acid penetrates and kills tissues high above the point of application. Those tissues must be removed for continuous gum flow, leaving1 faces 40 to 50 inches high at the end of the second year. Gum production may be increased by up to 20 percent with the concentrated acid.) Two faces may be treated on the bi-weekly schedule if trees are at least 14 inches dbh. Yields from 2 faces on the same tree are about 70 percent of the yield from 1 face each on 2 separate stems of the same size. Live bark-bars on 2-faced trees totalling at least 7 inches of circumference should be maintained and no trees worked with 2 faces which will not meet this requirement. Fusarium Lateritium Fusarium lateritium f. pini., a fungus, has been shown to induce gum flow when fresh wounds are inoculated. The normal flow of slash and longleaf pines was increased from one to several weeks. In nature, pitch-soaked wood in both species is caused by the fungus, from which cankers reportedly arise only on Virginia pine (True and Snow, 1949). 2, 4-D and Fertilizer Snow (1953) noted that a 2 percent 2,4-dichlorophenoxyacetic acid solution1 equalled HjSO4 for stimulating gum flow of slash pine. He also observed that fertilizers increase gum yields, but did not elaborate. 'This dosage killed longleaf pine.

Silviculture of Slash Pine

Black Turpentine Beetles'

Up to 10 percent of a naval stores stand may be attacked by the black turpentine beetle in a single season, and more than 70 percent of attacked stems die. Virgin faces installed with broad axes seem especially vulnerable to attack. A high level of activity often persists for 3 or more years, particularly in active naval stores operations. Attack the first month is generally below 18 inches, increasing to 3 feet after several months. While less than 8 attacks can be expected in the first month, up to 40 may be expected in each of the next 3 to 6 months (Fig. 31). Masses of pitch on the bark surface are 60

5040UNSPRAYED

30-

20-

10-

0 JULY

SEPT.

NOV

JAN.

MAR.

MAY

JULY

SEPT.

Figure 31â&#x20AC;&#x201D;Monthly incidence of black turpentine beetle attacks Smith, 1958).

NOV.

(after

usually solid, and sometimes flow downward. Gum-flow is not related to resistance to attack. Smith (1958) recommends salvaging infested trees and promptly spraying residuals with 1 gallon of 1.0 percent gamma isomer solution of BHC in 14 gallons of diesel oil. One gallon applied with a garden sprayer treats seven 12-inch trees. The toxicant has a long residual preventive action. Non-salvagable trees are sprayed as soon as possible to the height of the 'These insects are discussed in more detail in a later section.

Stephen F. Austin State College

highest pitch tube, and resprayed at the ground line. Although naval stores operations are generally not disrupted, there is some evidence that BHC may inhibit gum flow (Lee and Smith, 1955). Thus, trees with faces sprayed should, perhaps, be passed up for two chippings to allow time for recovery (Smith, 1955). Because naval stores operators are reluctant to salvage during the chipping season, infestations are often bypassed until losses are sizeable. "Sweetening" the salvage harvest by cutting healthy trees, according to Smith, could result in an aggravated situation and is, therefore, not recommended. Worked-out trees should be promptly harvested, and stumps of trees removed in thinnings should be sprayed shortly after cutting. Dry Face Dry face of naval stores pines, a condition in which gum permanently ceases to flow for no known reason, occurs mostly on back-faced trees. The first recognizable symptom is pitch soaking of the inner bark and wood above the face. In severe cases, pitch-soaked areas, called cambial blisters or internal lesions, occur above and beside dry areas. Prompt harvest of trees with severe dry face is necessary to avoid attacks by insects and fungi which cause stain and decay to considerable heights above the face. When mild symptoms appear in dry weather, trees frequently can be saved by discontinuing chipping until a heavy rain occurs. The malady is aggravated by drought, mechanical damage associated with poor streaking techniqueâ&#x20AC;&#x201D;which has the effect of drought upon a tree, and extracting gum from stems with short crowns (Schopmeyer and Maloy, 1960). Range Management While slash pine forests are frequently grazed, little is known of proper techniques for integrating range and forest management. Slash pine seedlings have a remarkable ability to recover from browse damage (Pig. 32). However, cattle rarely graze pine foliage where other green vegetation is available, therefore limiting pine browsing to late winter and early spring. Few trees are killed, but early growth may be retarded (Hughes, 1965). Trampling is to be expected in seedling stands, especially near water holes, feeding grounds, and on overgrazed, burned, and disked areas. Rubbing injury is severe on trees 2 to 6 feet tall. Form and vigor as well as height growth are affected by cattle browsing. Growth may be reduced by a third the first year, with three-fourths of the trees grazed displaying multiple leaders (Hopkins, 1950). Cassady, Hopkins, and Whitaker (1955) recommend delaying grazing in young stands until after May 1, and then controlling the herd so that one-half of the green forage is left at the end of the season. That permits a grazing capacity of 1 cow per acre per month where stands

Silviculture of Slash Pine

Figure 32â&#x20AC;&#x201D;Slash (and loblolly) pine seedlings have remarkable ability to recover from cattle damage. Cattle browsed nearly one-half of these trees when they were a year old. Now, at age 7, the trees have recovered and average 16 feet tall (from Cassady, Hopkins, and Whitaker, 1955). are relatively open and grass is good. Grazing should be prohibited for at least the first year following seedfall to avoid trampling of seedlings. Slash pine plantations at 6 x 8-foot spacing annually produce over 1400 pounds (air dry) of grasses per acre for the first 5 yearsâ&#x20AC;&#x201D;almost as much as in open fields. This diminishes to 1300 pounds for the next 5, and to about 250 pounds between ages 11 and 15, when canopies close and litter collects on the forest floor. After age 15, herbage likely will not exceed 100 pounds per acre per year (Campbell and Cassady, 1947;

Stephen F. Austin State College

Cassady, 1951). Grazing capacity is, of course, dependent upon the green weight of grass (Table 13).

TABLE 13. APPROXIMATE GRAZING CAPACITY IN RELATION

TO AMOUNT OF GRASS PER ACRE (GREEN WEIGHT) (after Campbell and Cassady, 1955) Grass per acre (pounds)

Acres per cow month

200 400 600 800 1000 1200 1667 2000 3000

15.0 7.5 5.0 3.75 3.0 2.5 1.8 1.5 1.0

Prescribed Burning

Prescribed burning during the winter is often necessary for maximum cattle weight gains. However, if employed more frequently than every 5 or 6 years, slash pine reproduction is impaired. Once trees are above 10 to 15 feet tall, more frequent burning is not injurious to the pines. During the period that fire is excluded, grazing is desirable to reduce fuel accumulations. Cattle, however, must be controlled, as they migrate to areas most recently burned where they may do excessive damage (Squires, 1947; Halls, Southwell, and Knox, 1952). Cattle Repellent The use of copper carbonate as a cattle repellent is postulated. Although effective, some discoloration of foliage results when seedlings are treated. The chemical is prepared by mixing 3 pounds of 12 percent asphalt emulsion (Flintkote C-13-HPC) in 3 quarts of water, then adding 2 pounds of copper carbonate (55% metalic copper), and diluting the mixture with 8 more quarts of water. The solution must be constantly agitated and not used when more than 2 days old. One gallon is sufficient to bundledip about 2500 seedlings. As the chemical is toxic to roots, seedlings are immersed only to within several inches of the root collar. They must be planted on the day treated (Duncan and Whitaker, 1959). South Florida Slash Pine

Since much of the land in which South Florida slash pine grows is also ranged by cattle, integration of the two crops is frequently desirable. South Florida slash pines are severely damaged by browsing where cattle concentrations are highâ&#x20AC;&#x201D;15 acres per cow per yearâ&#x20AC;&#x201D;and grass is insufficient (Fig. 33).

Silviculture of Slash Pine

Figure 33â&#x20AC;&#x201D;South Florida slash pine. Note tufted form in grazed and burned areas.

Where the acreage per cow is 20 or more, early injury to seedlings does not appear severe (SEFES, 1959). Winter feeding supplements are essential. Rock phosphate applications of 1 and 2 tons per acre in grazed areas, accompanied by site preparation prior to planting, result in heavy cattle concentration and seedling injury, but seedling growth may be improved. Prescribed burning is widely used for improving the south Florida forest range. As little forage is produced shortly after burning, a range ordinarily supporting 100 cows for 8 weeks is expected to support only 20 cows for the first 3 weeks following fire. At that time an acre carries a cow for a maximum of 4 days. By the end of 2 months, an acre will carry a cow for almost 10 days. The maximum forage yield of about 1 ton per acre, according to Rummell (1958), is attained 9 months after winter burning; but it is nutritionally poor. Hogs In contrast to long-leaf pine, slash pine ia not damaged by hogs. Peevy (1953) noted a case where 1 percent of the seedlings were injured in an area in which 88 percent of the longleaf pines were damaged.

Stephen F. Austin State College

Destructive Agents Diseases Fusiform Rust

The most serious pest of slash pine is the fungus Cronartium fusiforme, which frequently results in spindle-shaped swellings of trunks and branches called fusiform cankers. Stem infections in slash pine, more frequently than in loblolly pine, form true sunken cankers, leading to wind breakage (Verrall, 1958). Often, more than 80 percent of the seedlings in plantations and well-stocked natural stands are attacked, and the disease is an obstacle to the establishment of grafted slash and loblolly pine seed orchards (Campbell, Darby, and Barber, 1962). Trees infected in nurseries seldom survive more than 2 years in the field (Sleeth, 1940). Henry (1955) concluded that basal branches on slash pine nursery seedlings are not a sign of infection by the southern fusiform rust; branched seedlings should be culled only if they have the globular or fusiform stem swellings that characterize the rust. Trees of all sizes are attacked, but most damaging infections occur in seedlings and saplings rather than in older trees. Goggans (1949) noted that incidence of the disease is lower in mixed plantations than where slash pine occurs alone; he suggests alternate row planting with loblolly pine. But in the Piedmont, slash pine grows less rapidly than loblolly pine, and conversely in the Coastal Plain. Thinning out loblolly pine rows at a later date is suggested where slash pine is the desired final crop. Box and Applequist (1961) report Cronarimm-infested slash pine survived more poorly than loblolly pine in a plantation in southeastern Louisiana. When slash and loblolly pines occurred pure, no difference in infection was found by Goggans, but Siggers (1955) noted less infection on loblolly than slash pine seedlings because the former has a long-drawn-out germination period so that some germination occurs after the period of maximum rust spore production and thus some seedlings escape infection. Planting the best sites to slash pine may be undesirable, as trees of rapid growth are more susceptible to infection. Spring cultivation seems to increase infection, probably because it hastens breaking of dormancy in the early spring. Treated and untreated plantations had 14 and 9 percent of

Silviculture of Slash Pine

trees infected, respectively (Westberg, 1951; Balthis and Anderson, 1944). Westberg (1949) found that infections in Alabama increased from a range of 6 to 43 percent on untreated plots to a range of 11 to 67 percent on plots fertilized with nitrogen, phosphorus, and potassium. Apparently those treatments encourage trees to break dormancy earlier in the spring and thus allow a longer optimum period for infection through needles (Boggess and Stahelin, 1948a; Gilmore and Livingston, 1958). Fires which kill foliage, but not the tree, also increase infection. New lush needles form earlier than normal, prolonging the period during which inoculation takes place. Fires among large trees, where needles are not likely to be killed, probably will not result in more infections. Since eradication of the oak alternate hosts in the area is impractical, a check of disease incidence before planting is recommended. Where the disease is prolific, species substitution is suggested; density of stocking should be increased to a spacing of 4 x 4 feet, with a pre-comniercial thinning anticipated. The disease is more prevalent in widely spaced stands where there is little natural pruning, and many infected branches persist until the rust reaches the trunk (Muntz, 1948). Where crowns close quickly, the fungus dies with the branches before reaching the stem. Detrimental effects of rust can be lessened by pruning infected branches before infections reach trunksâ&#x20AC;&#x201D;when stands are 2 to 5 years old or less than 10 feet tall. Pruning is desirable if galls are less than 15 inches from the main stem, unless the stems are also infected,. Branches with galls more than 15 inches from the main stem should be removed if those branches are growing vigorously (Harms, 1961). Stem galls grow as much as 5 inches per year on slash pine. That is more rapid than for other susceptible southern pines and may account in part for the greater mortality of the species (Siggers, 1955). The difference in growth rate, however, does not apply to branch infection (Verrall, 1961). When the cambium is reached by the fungus, apparently a hormonal type reaction takes place, giving rise to rapid wood growth and the typical spindle or fusiform shaped gall. The gall is composed entirely of low density earlywood (Jackson, 1958). In slash pine, galls originate from an increase in both the size and number of cells in the cortex, phloem, and xylem. Uniseriate and fusiform rays are more numerous, wider, and longer; xylem tracheids are shorter and distorted; and there are more vertical resin ducts (Jewell, True, and Mallett, 1962),. An indication of inherited resistance to the rust was noted by Barber, Dorman, and Bauer (1957), who found infection varied by source of seed from 20 to 50 percent. Jewell (1966) found that natural resistance is transmitted to open-pollinated progenies. He hypothesized that resistance is controlled by a dominant gene, and that susceptibility is completely recessive in nature.

Stephen F. Austin State College Cycle

The alternate hosts for the rust are chiefly members of the red and black oak subgenus. Siggers (1955) listed these in descending order of susceptibility as water, willow, laurel, bluejack, blackjack, scarlet, southern red, turkey, and live oak. Wind disseminates spores to oaks in March, and yellow fungal spots soon appear on lower leaf surfaces where spores are produced. Oak to oak spread increases the amount of inoculum for dissemination to pine, which occurs from the middle of March to the middle of June. Most infection, except in areas where local site conditions are optimum for spread of the disease, appears to be confined to years when unusual climatic conditions favor production, dissemination, and germination of spores (Siggers, 1949, 1955). Temperatures between 60 and 80 째F and relative humidity near saturation for 18 hours are necessary for extensive infection. Urediospores occur on oak leaves, and telia soon develop in the same pustules or independently. These telia produce sporidia which infect pine. Uredial buildup takes place mainly in March, especially if the weather is warm (Verrall, 1958). Since aeciospores produced on pines and urediospores produced on oaks cannot infect hard, mature oak leaves, intensity of infection on oaks depends on a race in development between the pathogen and the oak foliage. Yet, as Siggers (1949) states, for the disease to become epidemic on pines, a considerable amount of inoculum must first be formed on oaks early in the season. Pines are infected through new needles or succulent stems before bark is formed; thus, infections on the main stem are usually within 2 feet of the ground, generally forming during the first 4 years of seedling growth. In Mississippi, Siggers (1949) found peak telia production from about April 15 to May 7, about the time pines start growth. Femes Annosus

Slash pines are often killed by Fames annosus, and it is probable that all of our native conifers are susceptible to infection under some conditions (Powers, 1962). Much windthrow from hurricanes is due to this root rot. Apparently and ironically, intensive management increases the amount of attack because the fungus infects fresh stumps (see Astin and Driver, 1962) in thinned areas, spreading through roots to nearby

Silviculture of Slash Pine

healthy trees and causing death in 2 years. With close spacings, more stumps are probably exposed to infection, and the closeness of the root systems helps spread the disease. Natural stands generally have less infection than plantations, but for them, too, more infection occurs in thinned stands. An extensive survey from Virginia to Texas revealed the proportion of trees dead or dying from the root rot was 2.8 percent in planted loblolly pine, 2.2 percent in planted slash pine, and 0.07 percent in natural slash pine stands (Verrall, 1962). The greater infection in plantations may be due to their establishment on drier, higher, sandier sites than those on which the species is likely to occur naturally. As infection occurs in stands with good growth, annosus root rot is not an off-site malady; and trees of all crown classes are equally susceptible. However, Malac and Saranthus (1967) did find more infection in Georgia.and South Carolina plantations on slopes and lower quality sites. Froelich, Dell, and Walkinshaw (1966) used discriminant analysis procedures with mineral soil samples to a 6-inch depth and grass cover in slash and loblolly pine plantations to develop the equations: Z, = 0.05029 (% organic matter) —0.05338 (pH) —0.00432 (% clay) —0.00089 (% sand) Z2 = 0.06076 (% organic matter) —0.05874 (pH) —0.00472 ( % clay) —0.00074 ( % sand) + 0.00071 ( % grass cover). Z,-values from —0.310 and Z2-values from —0.293 toward zero indicated low disease potential, more negative values indicating high disease potential. Summarily, severely damaged plantations on cutover and former agricultural lands were on sites with less organic matter, higher pH, more sand or clay, and less grass cover than healthy stands. Verrall (1962) and Powers and Verrall (1962) reported losses from the disease were also greater on former croplands and increased with years since thinning and with number and frequency of thinnings. Losses increased in plots with deep litter and coarse textured and deep A-horizons. Plots on slopes suffered more than those on flat sites. It is premature to state how damaging the disease eventually may be, since infection follows thinning and only now are plantations beginning to be thinned. It is possible that slash pine on susceptible sites may need to be grown on short ro-

I 84

Stephen F. Austin State College

tations, with a minimum of thinning, at the end of which stands will be clearcut. Fifty year rotations are probably too long. Planting at wide spacing reduces the need for thinnings and resultant losses from the root rot, but the possibility of damage from fusiform rust increases with width of spacing. Thinning with silvicides to avoid creating stumps may prove useful. Other measures not adequately tested in this country include planting conifers only on sites to which they are well adapted and planting in mixtures with hardwoods and other conifers (Powers and Boyce, 1963). The interval necessary between clearcutting and planting, and the behavior of the pathogen in this interval, are unknown. A delay in planting of 2 to 3 years after cutting may be necessary to permit decomposition of stumps and roots (Driver and Ginns, 1964). Hendrix et al. (1964) reported serious losses of seedlings of several pine species from this disease when planted after clearcutting. Clearcutting diseased stands should be delayed until it is obvious that the losses cannot be offset by the increased growth of remaining trees. Where stands are accessible, dead and dying pines should be salvaged as they are found, but unnecessary cutting should be avoided and the first thinning delayed as long as possible. Evidence

Crowns thinning out before death is a diagnostic symptom about half of the time; and even now death of trees in many plantations is blamed on drought or insects when F. annosus is really responsible. The stringy appearance of the decayed wood is best observed where roots have broken off from trees toppled by wind (Boyce, 1959). Conks are brown on top and white beneath. They most frequently occur under needle litter at the base of infected trees or on stumps or roots and are seldom readily visible (Fig. 34). They occur throughout the year. The pattern of killing trees in groups closely resembles that caused by bark beetles, and careful examination is necessary to determine the agent responsible. Conks on living trees attacked by bark beetles are strong evidence that root rot developed first and bark beetles followed (Powers and Boyce, 1963).

Silviculture of Slash Pine

Figure 34â&#x20AC;&#x201D;The conk of Fames annosus. Control

Several silvicultural measures have been discussed. Coal-tar creosote of wood preservative grade applied to stumps as soon as trees are cut may reduce stump infection (Powers and Boyce, 1963). Stumps should be treated immediately after cutting and all exposed wood surfaces liberally covered; however, results so far have not been generally satisfactory. Other chemicals are being tested (Campbell, 1965). Borate compounds, such as borax or borate powder applied in a 10 percent water solution or powder form, are currently recommended (Driver, 1963). Biological control, through competition or antagonism with other fungi, may be possible with stump surface inoculation

Stephen F. Austin State College

by a spore suspension of certain other species. Also, the opportunity for infection may be reduced by conducting thinning operations during the summer when fewer basidiospores of the fungus occur in the air (Campbell, 1965) and conditions are more favorable for growth of competing fungi (Driver and Ginns, 1964a). Recently, Malac and Saranthus (1967) reported finding only plantations thinned during the "summer" were infected in Georgia and South Carolina. Since their "summer" included the spring months (March-June), this report cannot be accepted as invalidating the findings of Driver and Ginns. Black Root Rot

A black root rot, a serious nursery disease caused by a fungus complex of Sclerotium bataticola and Fusarium species, has recently been found in pine plantations on deep sandy soils of western Florida (Smalley and Scheer, 1963). Though all species of pines in the area are susceptible, mortality was found only in young plantations of slash pine. The percentage of dead and dying trees ranged from 3 to 59 for entire plantations. Drought appeared to be the direct cause of foliage loss and mortality, the effects accentuated by the destruction of roots (particularly fine feeder roots). Red Root and Butt Rot

Red root and butt rot, caused by Polyporus tomentosus var. circinatus, occurs in trees with basal cankers caused by fusiform rust. The rot, detected in planted slash pine in the South in 1963, reduced 5-year radial growth of infected slash pines in some Georgia stands by up to 24 percent. Removal of all basal cankered slash pines during thinning is recommended (Boyce, 1967). Atropellis Tingens Atropellis tingens, a twig and branch girdling fungus, periodically attacks slash pine. Diller (1943) recorded epidemics in 1933 and 1943, with almost complete absence of infection in the interim. Inoculation occurs within the fascicles or at bases of needle sheaths and is evidenced by dead needles in the center of the small incipient cankers. The fascicle sheath enables maintenance of temperature and humidity conditions suitable for development of the fungus,. Generally restricted to seedlings which by spring or early summer after infection have conspicuous "flags" of brown branches, the fungus attacks slash pines within and without the

Silviculture of Slash Pine

natural range. Damage is usually negligible, and silvicultural measures are unnecessary. Pitch Canker Pitch canker, caused by the fungus Fusarium lateritium f. pini, is the principal disease affecting South Florida slash pine. Studies in pulpwoodsize stands showed a rapid increase in incidence over a 5-year period which was not correlated with tree crown class or diameter. The disease originated in the leaders of young trees more often than in the branches, perhaps related to dissemination of the fungus by tip moths (Matthews, 1962), reducing diameter growth and causing mortality and malformed trees. Removal of all diseased trees from plots did not reduce the rate of infection of remaining trees. While cankered trees should be salvaged during thinnings, that is not to be considered a sanitation operation in the sense of reducing further infection (Bethune and Hepting, 1963). Needle Casts Hypoderma lethale and H. hedgcockii cause dieback and premature shedding of slash pine foliage. Many of these trees, which look bad from February to April, are mistakenly harvested as victims of Fames annosus. Lophodermium pinastri may be found on dead tips of living needles, but it is mostly saprophytic. Insects Reproduction Weevils

Pales weevils and Pachylobius picivorus are reported to have damaged first-year slash pine plantations following a severe fire late in the summer and a salvage clearcutting operation which provided freshly cut stumps for breeding (Sentell, 1949). Feeding begins on tender bark near buds. Insects then work downward, stripping bark from roots to depths in the soil of 5 inches. Mortality depends on the amount of pine debris in the area: up to 90 percent of seedling stands have been killed (SFES, 1958; Speers, 1958). Weevil larvae of Hylobius spp. infest root systems and kill young slash pines in south Georgia, especially on disturbed soils (Ebel and Merkel, 1967). Moths

A common pine moth (Dioryctria clarioralis) in the Atlantic coastal area was recently noted in slash pine stands of the Gulf Coast. Larvae mine and kill terminals of stems and branches for 6 to 24 inches from the tips. This pest may become important in plantations (Beal, 1960). Rhyacionia subtropica, a pine

Stephen F. Austin State College

tip moth whose range coincides with that of slash pine, is also a potential pest (Merkel, 1963). Mattoon (1936) reported that the Nantucket pine tip moth does not attack slash pine. However, the species is susceptible although rated as quite resistant (Yates and Beal, 1962), and studies in south Florida indicate South Florida slash pine is more resistant than typical slash (Bethune, 1963). Resistance of slash and longleaf pines may be related to the inability of the larvae to bring about a rapid crystallization of the oleoresins of these species (Yates, 1962). Crickets

Crickets clip slash pine seedlings near the ground. Up to 95 percent of natural as well as planted trees may be destroyed within a month- The chief distinguishing symptom is the type of burrow, a main tunnel connected to the surface by a narrow passage, where the fragments of seedlings are dragged in and stored. At the burrow entrance is a mound about 3 inches across which often contains subsoil particles and resembles a pile of earthworm casts (Fig. 35). Disked areas have more cricket damage than grass roughs. The insects are active in fall, late winter, and spring, but may work at any season when a few warm dry days occur. In Louisiana, Russell (1958) observed the attacks cease with the inception of November rains.

Figure 35â&#x20AC;&#x201D;A cricket mound and burrow (from Russell, 1958).

Silviculture of Slash Pine

Black and Red Turpentine Beetles

The black and red turpentine beetles are among the more serious pests of the four principal southern pines, although before 1950 they were relatively unimportant. Infestation was first noted in 1948. Their importance now is probably due to logging practices: heavy machines churn up the ground, bruise and crush roots, and skin more trees than did mules of earlier days. Black turpentine beetles seem to increase with logging damage, and heaviest concentrations of the insect occur on low poorly drained sites logged during wet seasons. From there, they spread to higher elevations. Consequently, low areas should not be harvested in wet seasons, and ground disturbance should be held to a minimum. These beetles usually breed in stumps and roots and attack the lower 6 feet of the trunks of weak pines. Adult beetles (Fig. 36), !/i to 1/3 inch long, bore through the outer corky bark into the cambium, making a large distinctive pitch tube on the bark surface of trees more than 3 inches dbh; they usually push small particles of granular, dried, whitish resin from the galleries to the ground (Fig. 37). Resin flow may, rarely, drown attacking beetles. (The resin pushed from breeding galleries appears "pitched out" of very resinous trees.) Tubes are about 1 inch in diameter and, when older, have a sugar-like texture. When the adult reaches the soft phloem, a vertical gallery between V-> and % inch wide is made; eggs are laid in large groups along its side. The eggs hatch after 10 days. Larvae feed gregariously in the soft phloem, working away from the egg gallery, forming an irregular fanshaped pattern in the phloem. This larval gallery may be 12 inches across. If a sufficient number of attacks occur, trees are girdled and die. Larvae go into the pupal, or resting, stage for 10 to 14 days in cells made between wood and bark, or sometimes completely within the hard bark (Fig. 38). New adults then bore through the bark and fly to other trees to begin a new generation. Attacks, which may be made on a tree over a period of several months, are usually confined to a small percentage of the stand at any one time. As a result, only a few red-foliaged trees may be found. However, over a period of 2 years this number can increase to 20 to 30 percent of the stand. As these lose their red needles, others begin to fade, and an outbreak may be more

Stephen F. Austin State College

Figure 36â&#x20AC;&#x201D;Black turpentine beetle adult (USFS).

Figure 37â&#x20AC;&#x201D;Turpentine beetle attacks at the base of slash pine trees are usually below 18 inches the first month. After several months, they are concentrated in the basal 36 inches, as shown (from Smith, 1958).

Silviculture of Slash Pine

severe than it appears (Smith, 1954; Lee and Smith, 1955). When ambrosia beetles follow, death of trees is inevitable. Ips engraver beetles also do extensive damage. Smith's (1956) description of the killing of a pine by black turpentine beetles is helpful in estimating whether salvage is feasible. If pitch tubes and ambrosia dust are present, the tree is about to begin fading. About 1% months after fading, foliage

Figure 38â&#x20AC;&#x201D;A near-mature brood of black turpentine beetles exposed by removing the bark of this infested pine. Pupal cells and a few pupae can be seen (from Smith, 1954).

is red and blue stain appears in the wood. Salvage is yet possible. At 3 months, three-fourths of the needles are gone, infestation of blue stain fungus is heavy, secondary borers are active, and salvage may or may not be practical. All needles are lost 5 months after attack, though twigs persist. By then, blue stain is severe and borers so active that salvage is rarely possible. After 10 months, most twigs have fallen, wood rot is extensive and, soon after, trunks break.

I 92

Stephen F. Austin State College Control

Stands should be inspected twice a year. Control can be had with applications of BHC. A 0.5 percent concentration of gamma isomer in diesel oil remains effective for at least 7 months when applied to freshly cut stumps and skinned trees as a preventative measure. Three pounds of ethylene dibromide should be added to each 5 gallons as a remedial control. One gallon treats 40 to 50 square feet of bark surface. Generally, spraying the lower 3 feet of trunks is sufficient, but where attacks are high, it may be necessary to treat the lower 12 feet. Leaves should be raked away from bases of trees before spraying in order that toxicants may contact and kill broods which develop in bark and roots to a depth of 5 feet below ground. Likewise, loose bark should be sloughed away from stumps prior to spraying. As the majority of attacks are in the basal 2 feet of trunks, effective salvage necessitates harvesting infested trees at the ground line, else many insects will be left in the woods. Wahlenberg (1946) notes that cessation of logging operations may encourage attacks on living trees and necessitate the peeling or burning of bark from surrounding stumps. Town Ants

Defoliation by the town ant, Atta texana, seriously reduced survival of slash pine in a plantation in central Louisiana. While cull grade seedlings suffered the greatest mortality, seedlings of all grades are damaged窶馬eedles clipped, terminal buds removed, and stems partially debarked (Shoulders, 1960). Cone Insects

Tetyra bipunctata and Leptoglossus corculus, two sucking insects, feed on cones of slash and longleaf pines (DeBarr, 1967). Seed is damaged, and control of the insects may become necessary in seed orchards. BHC sprays have proved useful (Cole, 1958). Nematodes

Nematodes may infest slash pine seedlings at nurseries, subsequently causing death to out-planted stock. Control is achieved by dipping roots in water baths of 116ﾂｰF to 120ﾂｰF for 25 minutes prior to field planting (Gentile and Johansen, 1956).

Silviculture of Slash Pine

Rodents

Some attacks by cotton rats have been noted for slash pines less than 2 feet tall. Damage is rare and is more probable in rough and brush areas than in freshly burned or otherwise prepared planting sites. Pocket gophers are a serious threat to young plantations in the Coastal Plain (Hughes, 1965) ; their control is discussed in Bui. 11, this series. Cone losses to squirrels were greater on fertilized (8-8-8, 18 Ibs./tree) than unfertilized slash pine trees in a seed-production area in Florida. Squirrels destroyed 11.7 percent of the cones on fertilized trees and 1.3 percent on the unfertilized (Asher, 1963). Storms Ice

Although ice damage is destructive to southern pines, there is little chance of it in slash pine except where the species' is introduced north of its natural range. Temperatures to 5째F in the absence of sleet, wind, or rain do not injure year-old seedlings (Webster, 1931), and many badly bent stems recover by the end of the growing season following an ice storm. As ice storms were noted by McKellar (1942) to be about seven times more severe on slash pine than loblolly pine in the Piedmont, and because ice storms can be expected in this area once every 5 years, loblolly pine may be preferred. Another severe glaze storm in this section caused 3 percent of the slash pine stems to lean permanently in the loose soil, in contrast to less than 1 percent of the loblolly pines (Brender and Nelson, 1952). In central Louisiana, too, loblolly pine is six times more resistant than slash pine to ice damage up to age 10 (Muntz, 1948a.) Dense pulpwood stands are extremely vulnerable soon after thinning to damage from glaze. In areas subject to frequent glaze storms, loblolly pine should be planted instead of slash pine, no spacing closer than 6 x 8 feet should be used, stands should be thinned early and frequently (removing no more than one-third of the basal area at a time), and row thinning or thinning from above should be avoided. Severely bent trees may be saved by prompt, drastic pruning (Brender and Romancier, 1965). Slash pine is not always more susceptible to ice breakage than loblolly pine, and early observations of ice injury generally

Stephen F. Austin State College

predict a situation more serious than is indicated by tallies a year later. Trees bent less than 60 degrees from vertical generally straighten satisfactorily without pruning. The wood of young slash pine characteristically possesses a relatively high density summerwood, which may enable it to escape stem injury by sleet. Its shallow root system, however, makes it susceptible to partial or complete uprooting by heavy ice (Mattoon, 1936). Wind

Slash pine, generally without a strong taproot, is subject to windthrow, the severity depending upon soil depth, density of stand, frequency of thinning, and amount of water in the soil. When the ground is watersoaked and shallow, seedlings, saplings, and poles may lean much more than other southern pines (Cockrell, 1936; Derr and Enghardt, 1957), and South Florida slash pine is more susceptible to windfall than the typical species. Hurricane damage in East Texas plantations is directly related to thinning intensity. Larger trees suffer most, tending to windthrow and break to a greater degree than small stems in unthinned stands (Nelson and Stanley, 1959) (Table 14). Less damage would probably occur if there were time for crown closure following thinning. TABLE 14. PLANTATION DAMAGE BY HURRICANE AUDREY IN 1957 (after Nelson and Stanley, 1959) Thinning degree Light

Trees before thinning—number/acre Trees after thinning—number/acre Trees removed—percent BA after thinning—sq. ft./acre Trees damaged—number/acre B A damaged—sq. ft./acre

580 411 18 92 6

Medium

Heavy

547 376 31 74 11

584 304 48 65 17

f. AUSTIN STATE COLLEGE

Silviculture of Slash Pine

LITERATURE CITED Akerman, A. 1929. Thinning slash pine. J. For. 27:714-719. Allen, R. M., and N. M. Scarbrough. 1960. Growth of slash pine and pond pine on wet sites. So. For. Notes 125. Allen, R. M., and N. M. Scarbrough. 1961. Fertilizer and mulch aid grafting of slash pine, J. For. 59:294. Anderson, G. 1958. Economics of site preparation and land regeneration in the South: example of an industry concept. J. For. 56:754-756. Anonymous. 1929. Volume, yield, and stand tables for second-growth southern pines. USDA Misc. Pub. 50. Arlen, W. H. 1959. Growth of slash pine plantations on flatwoods in west central Florida. J. For. 57:436. Asher, W. C. 1963. Squirrels prefer cones from fertilized trees. USFS Ees. Note SE-3, Asher, W. C. 1964. Electrical potentials related to reproduction and vigor in slash pine. For. Sci. 10:116-121. Astin J. S., Jr., and C. H. Driver. 1962. The natural occurrence of Fames annosus and associated fungi in slash pine stumps. Plant Disease Reporter 46:738-741. Balthis, R. p., and D. A. Anderson. 1944. Effect of cultivation in a young slash pine plantation on the development of Cronartium cankers and forked trees. J. For. 42:926-927. Barber, J. C. 1965. Seed. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.) Ga. For. Res. Council Rept. 14. Barber, J C., K. W. Dorman, and E. Bauer. 1957. Slash pine progeny tests indicate genetic variation in resistance to rust. Southeastern For. Exp. Sta. Res. Note 104. Barber, J. C., K. W. Dorman, and R. A. Jordan. 1955. Slash pine crown width differences appear at early age in 1-parent progeny tests. Southeastern For. Exp. Sta. Res. Note 86. Barber, J. C., and D. F. VanHaverbeke. 1961. Growth of outstanding nursery seedlings of Pinus elliottii Engelm. and Finns taeda L. Southeastern For. Exp. Sta. Paper 126. Barnes, R. L. 1955. Growth and yield of slash pine plantations in Florida. Univ. Fla. Sch. For. Res. Rept. 3. Barnes, R. L., and C. W. Ralston. 1953. The effect of colloidal phosphate on height growth of slash pine plantations. Univ. Fla. Sch. For. Res. Note 1. Barnes, R. L., and C. W. Ralston. 1955. Soil factors related to growth and yield of slash pine plantations. Univ. Fla. Agr. Exp. Sta. Bui. 559. Barrett, J. J. 1963. Slash pine gum flow unaffected by seed origin. For. and People 13 (2) :18-19. Barrett, J. P., and G. W. Bengtson. 1964. Oleoresin yields for slash pines from seven seed sources. For. Sci. 10:159-164. Beal, R. H. 1960. Pine pitch moth in Mississippi. So. For. Notes 130. Bengtson, G. W. 1955. Effects of flooding and water temperature on root growth and survival of slash pine seedlings. Unpub. Rept., Duke Univ.

Stephen F. Austin State College

Bengtson, G W. 1963. Slash pine selected from nurserybeds: 8-year performance record. J. For. 61:422-425. Bengtson, G. W., R. W. Clements, P. R. Larson, and C. S. Schopmeyer. 1959. Intensive gum extraction. For. Farmer 18(9>:8 et f o l . Bengtson, G. W., and C. S. Schopmeyer. 1959. A gum yield table for 3/4inch acid treated streaks on slash pine. Southeastern For. Exp. Sta. Res. Note 138. Bennett, F. A. 1953. Site indexes of the soil series on the George Walton Experimental Forest. Southeastern For. Exp. Sta. Res. Note 34. Bennett, F. A. 1955. The effect of pruning on the height and diameter growth of planted slash pine. J. For. 53:636-638. Bennett, F. A. 1955a. Growth of crowded 45-year-old slash pine after release. Southeastern For. Exp. Sta. Res. Note 77. Bennett, F. A. 1956. Financial aspects of pruning planted slash nine. Southeastern For. Exp. Sta. Paper 64. Bennett, F. A. 1956a. Growth of planted slash pines on cutover lands and old fields. J. For. 54:267-268. Bennett, F. A. 1956b. Growth of slash pine plantations on the George Walton Experimental Forest. Southeastern For. Exp. Sta.. Paper 66. Bennett, F. A. 1960. Height growth pattern and thinning of slash pine (Pinus elliottii var. elliottii). J. For. 58:561-562. Bennett, F. A. 1962. Growth and yield of planted conifers in relation to initial spacing and stocking. Proc. Soc. Amer. For. Bennett, F. A. 1963. Growth and yield of slash pine plantations. USFS Res. Paper SE-1. Bennett, F. A. 1965. Growth and yield of planted slash pine. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Bennett, F. A. 1965a. Harvesting slash pine. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Bennett, F. A. 1965b. Thinning slash pine. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Bennett, F. A., C. E. McGee, and J. L. Clutter. 1959. Yield of old-field slash pine plantations. Southeastern For. Exp. Sta. Paper 107. Bethune, J. E. 1960. Distribution of slash pine as related to certain climatic factors. For. Sci. 6:11-17. Bethune, J. E. 1963. Pine tip moth damage to planted pines in south Florida. USFS Res. Note SE-7. Bethune, J. E. 1966. Performance of two slash pine varieties planted in south Florida. USFS Res. Paper SE-24. Bethune, J. E., and G. H. Hepting. 1963. Pitch canker damage to South Florida slash pine. J. For. 61: 517-522. Bethune, J. E., and 0. G. Langdon. 1966. Seed source, seed size, and seedling grade relationships in South Florida slash pine. J. For. 64:120124.

Silviculture of Slash Pine

Bishop, G. N., and G. Marckworth. 1933. Some factors influencing resin concentration in loblolly and slash pines. J. For. 31:953-960. Boggess, W. R. 1950. The effect of repeated pruning on diameter and height growth of planted slash pine. J. For. 48:352-353. Boggess, W. R., and R. Stahelin. 1948. Incidence of cronartium rusts on slash pine plantations. Ala. Agr. Exp. Sta. 56th Ann. Rept. Boggess, W. R., and R. Stahelin. 1948a. The incidence of fusiform rust in slash pine plantations receiving cultural treatments. J. For. 46: 683-685. Bormann, F. H. 1957. Moisture transfer between plants through intertwined root systems. Plant Physiol. 32:48-55. Box, B. H., and M. B. Applequist. 1961. Comparison of loblolly and slash pine growth in a twelve-year-old plantation in southeastern Louisiana. LSU For. Note 49. Box, B. H., N. E. Linnartz, and M. B. Applequist. 1964. Growth of slash and loblolly pine in a mixed plantation in southwestern Louisiana.. LSU For. Note 58. Boyce, J. S., Jr. 1959. Root rot in pine plantations. For. Farmer 19(3>:8 et f o l . Boyce, J. S., Jr. 1967. Red root and butt rot in planted slash pines. J. For. 65:493-494. Brendemuehl, R. H. 1967. Loss of topsoil slows slash pine seedling growth in Florida sandhills. USFS Res. Note 50-53. Brender, E. V., and T. C. Nelson. 1952. Re-establishing pine on Piedmont cut-over land. Southeastern For. Exp. Sta. Paper 18. Brender, E. V., and R. M. Romancier. 1965. Glaze damage to loblolly and slash pine. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Broadfoot, W. M. 1951. Forest planting sites in north Mississippi and west Tennessee. So. For. Exp. Sta. Occ. Paper 120. Bruce, D. 1952. Fire pruning of slash pine doesn't pay. So. For. Notes 78. Bull, H. 1947. Yields from 3 spacings of planted slash pine. So. For. Notes 51. Burns, R. M. 1962. Southern pines and sweetgums do not mix. So. For. Notes 141. Byram, G. M. 1948. Vegetation temperature and fire damage in the southern pines. Fire Control Notes 9(4) :34-36. Byrd, R. R., and C. E. Peevy. 1963. Freezing temperatures affect survival of planted loblolly and slash pine seedlings. Tree Planters' Notes 58: 18-19. Campbell, R. S., and J. T. Cassady. 1947. Grazing cattle in pine plantations. So. For. Notes 48. Campbell, R. S., and J. T. Cassady. 1955. Forage weight inventories on southern forest ranges. So. For. Exp. Sta. Occ. Paper 139. Campbell, W. A. 1965. Reducing losses from diseases in pine plantations. In: A guide to loblolly and slash pine plantation management in

139967

Stephen F. Austin State College

southeastern USA. W. G. Wahlenberg (ed.>. Ga. For. Res. Council Kept. 14. Campbell, W. A., S. P. Darby, and J. C. Barber. 1962. Fusiform rust, an obstacle to the establishment of grafted slash and loblolly pine seed orchards. Ga. For. Res. Paper 11. Cassady, J. T. 1951. Bluestem range in the piney woods of Louisiana and East Texas. J. Range Mgmt. 4:173-177. Cassady, J. T., W. Hopkins, and L. B. Whitaker. 1955. Cattle grazing damage to pine seedlings. So. For. Exp. Sta. Occ. Paper 141. Chappelle, D. E. 1962. Value growth of pine pulpwood on the George Walton Experimental Forest. Southeastern For. Exp. Sta. Paper 140. Claridge, F. H. 1933. Observation on slash pine in North Carolina. J. For. 31:98-100. Clements, R. W. 1960. Modern gum naval stores methods. Southeastern For. Exp. Sta. Manual. Clements, R. W. 1961. Air temperature and gum yield. Southeastern For. Exp. Sta. Res. Note 168. Cobb, F. W., Jr. 1957. A test of the application of existing site-index curves to the flatwoods slash pine type. Southeastern For. Exp. Sta. Res. Note 111. Cockrell, R. A. 1936. Susceptibility of the southern pines to wind damage. J. For. 34:394. Coile, T. S. 1952. Soil and the growth of forests. Adv. in Agron. 4:329-398. Coile, T. S. 1952a. Soil productivity for southern pines. For. Farmer 11 (7): 10 e t f o l . , 11(8) :11 et f o l . Cole, D. E. 1958. Aerial application of benzene hexachloride for the control of cone insects on a slash pine seed production area. J. For 56:768. Collins, A. B., III. 1967. Density and height growth in natural slash pine. USFS Res. Paper SE-27. Cooper, E. N. 1961. Tussock seeding and mound planting. Tree Planter's Notes 46:5-7. Cooper, R. W., and J. H. Perry, Jr. 1956. Slash pine seedling habits. So. Lbrmn. 193 (Dec. 15) :198-199. Cruikshank, J. W. 1954. Site index of the major pine forest types in the southeast. Southeastern For. Exp. Sta. Res. Note 50. Curry, J. R. 1943. Selection, propagation, and breeding of high-yielding southern pines for naval stores production. J. For. 41:686-687. DeBarr, G. L. 1967. Two new sucking insect pests of seed in southern pine seed orchards. USFS Res. Note SE-78. Derr, H. J. 1966. Longleaf X slash hybrids at age 7: survival, growth, and disease susceptibility. J. For. 64:236-239. Derr, H. J., and H. Enghardt. 1957. Some forestry lessons from hurricane Audrey. So. Lbrmn. 195(Dec. 15) :142-144. Derr, H. J., and H. Enghardt. 1960. Is geographic seed source of slash pine important? So. Lbrmn. 201 (Dec. 15) : 95-96. Diller, J. D. 1943. A canker of eastern pines associated with Atropellis tingens. J. For. 41:41-51.

Silviculture of Slash Pine

Dorman, K. W. 1962. Forest tree improvement for Georgia. Ga. For. Res. Council Rept. 9. Dorman, K. W. 1966. We can double the volume of slash pine growth. For. Farmer 26(2) :22-23. Driver, C. H. 1963. Further data on Borax as a control of surface infection of slash pine stumps by Fames annosus. Plant Disease Reporter 47: 1006-1009. Driver, C. H., and J. H. Ginns, Jr. 1964. Annosus root-rot in young southern pines planted on an infested site. Plant Disease Reporter 48:803-807. Driver, C. H., and J. H. Ginns, Jr. 1964a. The effects of climate on occurrence of annosus root-rot in thinned slash pine plantations. Plant Disease Reporter 48:511. Duncan, D. A., and L. B. Whitaker. 1959. Cattle repellents for planted pines. Tree Planters' Notes 36:9-12. Ebel, B. H. 1961. Thrips injure slash pine female flowers. J. For. 59:374. Ebel, B. H., and E. P. Merkel. 1967. Hylobius weevil larvae attack roots of young slash pines. For. Sci. 13:97-99. Echols, R. M. 1955. Linear relation of fibrillar angle to tracheid length and genetic control of tracheid length in slash pine. Trop. Woods 102:11-22. Foil, R. R. 1961. Late season soil moisture shows significant effect on width of slash pine summerwood. LSU For. Note 44. Forbes, R. D. (ed.). 1955. Forestry Handbook. Soc. Am. For. Foulger, A. N. 1960. Growth of oversize slash pine seedlings following outplanting. Union Bag-Camp Paper Corp. Woodland Res. Note 7. Froelich, R. C., T. R. Dell, and C. H. Walkinshaw. 1966. Soil factors associated with Fames annosus in the Gulf States. For. Sci. 12:356-361. Gansel, C. R. 1967. Do wet- and dry-site ecotypes exist in slash pine? USFS Res. Note SE-69. Garin, G. I. 1955. Pruning southern pine. For. Farmer 15(2) :7-8. Garin, G. I. 1965. Pruning. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Gentile, A. C., and R. W. Johansen. 1956. Heat tolerance of slash and sand pine seedlings. Southeastern For. Exp. Sta. Res. Note 95. Gilmore, A. R., and K. W. Livingston. 1958. Cultivating and fertilizing a slash pine plantation: effects on volume and fusiform rust. J. For. 56:481-483. Goggans, J. F. 1949. Cronartium fusiforme on slash and loblolly pine in the Piedmont region of Alabama. J. For. 47:978-980. Goggans, J. F. 1951. Topsoil and pine trees in Alabama's Piedmont. Ala. Agr. Exp. Sta. Leaflet 31. Greene, J. T. 1959. The control pollination of slash pine. Minnesota Acad. Sci. 27:116-117. Greene, J. T. 1962. Air-layered branches of slash pine will develop into straight trees. J. For. 60:135.

100

Stephen F. Austin State College

Greene, J. T. 1962a. A seed source study of slash pine within the state of Georgia. Tree Planters' Notes 51:11-14. Greene, J. T., and M. Reines. 1958. A preliminary report on field grafting. J. For. 56:127-128. Grigsby, H. C. 1959. Two promising pine hybrids for the mid-South. So. Lbrmn. 198(Jan. 1) :32-33. Gruschow, G. F. 1949. Results of a pre-commercial thinning in slash pine. So. Lbrmn. 179(Dec. 15) :230-232. Gruschow, G. F., and T. C. Evans. 1959. The relation of cubic-foot volume growth to stand density in young slash pine stands. For. Sci. 5:49-55. Halls, L. K., and N. R. Hawley. 1954. Slash pine cone production is increased by seed-tree release. Southeastern For. Exp. Sta. Res. Note 66. Halls, L. K., B. L. Southwell, and F. E. Knox. 1952. Burning and grazing in Coastal Plain forests. U. Ga. Agr. Exp. Sta. Bui. 51. Harkin, D. A. 1957. Every seedling from selected seed. J. For. 55:842-843. Harms, W. R. 1961. Growth of fusiform cankers on young slash pine. Southeastern For. Exp. Sta. Res. Note 159. Harms, W. R. 1962. Spacing-environmental relationships in a slash pine plantation. So. For. Exp. Sta. Paper 150. Harms, W. R., and A. B. Collins, III. 1965. Spacing and twelve-year growth of slash pine. J. For. 63:909-912. Hatcher, J. B. 1957. Prescription planting. For. Farmer 16(5) :4-6. Hawley, N. R. 1953. Rapid growth of planted slash pine in the middle coastal plain of Georgia. Southeastern For. Exp. Sta. Res. Note 32. Hawley, N. R. 1965. Initial spacing of slash pine. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Hebb, E. A. 1955. Slash pineâ&#x20AC;&#x201D;promising sandhills species. So. For. Notes 100. Hebb, E. A. 1957. Regeneration in the sandhills. J. For. 55:210-212. Hendrix, F. F., Jr., E. G. Kuhlman, C. S. Hodges, Jr., and E. W. Ross. 1964. Fames annosusâ&#x20AC;&#x201D;a serious threat to regeneration of pine. USFS Res. Note SE-24. Henry, B. W. 1955. Basal branches no sign of rust on slash pine seedlings. So. For. Notes 100. Heyward, F. D. 1934. Comments on the effect of fire on feeding roots of pine. Naval Stores Rev. 44(19) :4. Heyward, F. D. 1959. Effect of the 1954 drought on pine growth. For. Farmer 19(1) :8 et f o l . Hiller, C. H. 1964. Estimating size of the fibril angle in late wood tracheids of slash pine. J. For. 62:249-252. Hodgkins, E. J. 1956. Testing soil-site index tables in southwestern Alabama. J. For. 54:261-266. Hoekstra, P. E. 1957. Air-layering of slash pine. For. Sci. 3:344-349. Hoekstra, P. E. 1957a. A case study of species comparison on flatwoods soil. So. Lbrmn. 195(Dec. 15) : 158-159.

Silviculture of Slash Pine

101

Hoekstra, P. E. 1960. Counting cones on standing slash pine. Southeastern For. Exp. Sta. Res. Note 151. Hoekstra, P. E., and R. W. Johansen. 1957. Growth of planted slash pine air layers. J. For. 55:146. Hoekstra, P. E., and F. Mergen. 1957. Experimental induction of female flowers on young slash pine. J. For. 55:827-831. Hopkins, W. 1950. Grazing damages newly planted slash pine. So. For. Notes 65. Hughes, R. H. 1965. Animal damage. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Hughes, R. H. 1965a. Cultivation in pine plantations. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Hughes, R. H., and J. E. Jackson. 1962. Fertilization of young slash pine in a cultivated plantation. Southeastern For. Exp. Sta. Paper 148. Jackson, L. W. R. 1958. Anatomy of fusiform rust galls. Ga. Acad. Sci. 16(4):73-76. Jackson, L. W. R. 1968. Effect of thinning on growth and specific gravity of loblolly and slash pine. Ga. For. Res. Paper 50. Jackson, L. W. R., and M. C. Cloud. 1958. Nitrogen fertilizer increases growth of stem of slash and longleaf pine. Naval Stores Rev. 68(7) : 4-5. Jackson, L. W. R., and J. T. Greene. 1957. Hereditary variations in slash pine tracheids. Fourth So. Conf. For. Tree Improvement Proc. Jackson, L. W. R., and J. T. Greene. 1958. Tracheid length variation and inheritance in slash and loblolly pine. For. Sci. 4:316-318. Jackson, L. W. R., and W. E. Morse. 1965. Tracheid length variation in single rings of loblolly, slash, and shortleaf pine. J. For. 63:110-112. Jackson, L. W. R., and B. J. Warren. 1962. Variation and inheritance in specific gravity of slash and loblolly pine progeny. Ga. For. Res. Paper 14. JarBergs, K. A. 1963. Determining fiber length, fibrillar angle, and springwood-summerwood ratio in slash pine. For. Sci. 9:181-187. Jewell, F. F. 1961. Artificial testing of intra- and inter-species southern pine hybrids for rust resistance. Sixth So. Conf. For. Tree Improvement, So. For. Exp. Sta. Jewell, F. F. 1966. Inheritance of rust resistance in southern pines. In: Breeding pest-resistant trees. Proc. NATO and NSF Symposium, Pergamon Press, New York. Jewell, F. F, R. P. True, and S. L. Mallett. 1962. Histology of Cronartium fusiforme in slash pine seedlings. Phytopathology 52:850-858. Johansen, R. W., and J. F. Kraus. 1958. Propagation techniques applicable to longleaf pine. J. For. 56:664. Johnson, J. W. 1956. Results of an empirical study of direct seeding. Union Bag & Paper Corp. Woodland Res. Note 2.

102

Stephen F. Austin State College

Jones, E. P., Jr., 1959. Wet site survival and growth. Southeastern For. Exp. Sta. Res. Note 130. Jones, E. P., Jr. 1961. Wide spacing of slash pine produces early gum and sawtimber yields. Southeastern For. Exp. Sta. Res. Note 169. Jones, E. P., Jr. 1963. A test of direct seeding depths for slash and longleaf pine. USFS Res. Note SE-5. Jones, L., J. C. Barber, and J. E. Mabry, Jr. 1964. Effect of methyl bromide fumigation on germination of longleaf, slash, and loblolly pine seed. J. For. 62: 737-739. Jones, L., and S. Thacker. 1965. Survival. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Jorgensen, J. R., and E. Shoulders. 1967. Mycorrhizal root development vital to survival of slash pine nursery stock. Tree Planters' Notes 18(2):7-11. Judson, G. M. 1965. Tree diameter growth in Alabama. USFS Res. Note SO-17. Kaufman, C. M. 1965. Growth of young slash pine. For. Farmer 24(13) :8 et f o l . Ketcham, D. E., and J. E. Bethune. 1963. Fire resistance of South Florida slash pine. J. For. 61: 529-530. Kittredge, J. 1952. Deterioration of site quality by erosion. J. For. 50:554556. Klawitter, R. A. 1966. Early response of pole-sized slash pine to drainage. USFS Res. Note SE-63. Koenig, R. L. 1962. Comparison of early development of planted and direct seeded slash pine. Union Bag-Camp Paper Corp. Woodland Res. Note 13. Koshi, P. T. 1960. Deep planting has little effect in a wet year. Tree Planters' Notes 40:7. Kramer, P. J. 1943. Amount and duration of growth of various species of tree seedlings. Plant Physiol. 18:239-251. Krueger, D. W., and A. M. Pachence. 1961. Wind directions for prescribed burning in southeastern United States. Southeastern For. Exp. Sta. Paper 131. Langdon, O. G. 1955. Clipping needles adversely affects survival of South Florida slash pine. Southeastern For. Exp. Sta. Res. Note 74. Langdon, 0. G. 1956. Elevation and tree growth. So. Lbrmn. 193 (Dec. 15) : 191-192. Langdon, O. G. 1957. The first successful direct seeding in south Florida. So. Lbrmn. 195 (Dec. 15) : 180-181. Langdon, 0. G. 1958. Cone and seed size of South Florida slash pine and their effects on seedling size and survival. J. For. 56:122-127. Langdon, O. G. 1958a. Early trends in a slash pine seed source study in south Florida. Southeastern For. Exp. Sta. Res. Note 123. Langdon, O. G. 1959. Site index curves for South Florida slash pine. Southeastern For. Exp. Sta. Res. Note 133.

Silviculture of Slash Pine

103

Langdon, O. G. 1961. Yield of unmanaged slash pine stands in south Florida. Southeastern For. Exp. Sta. Paper 123. Langdon, 0. G. 1962. Ridge planting improves early growth of South Florida slash pine. J. For. 60: 487. Langdon, O. G. 1963. Growth patterns of Pinus elliottii var. densa. Eco. 44: 825-827. Langdon, 0. G. 1963a. Range of South Florida slash pine. J. For. 61: 384-385. Lee, R. E., and R. H. Smith. 1955. The black turpentine beetle, its habits and control. So. For. Exp. Sta. Occ. Paper 138. Lehocky, A. A., and R. B. Lee. 1954. South Carolina sandhills can grow pine timber. J. For. 52: 280-281. Lemon, P. C. 1946. Prescribed burning in relation to grazing in the longleaf-slash pine type. J. For. 44:115-117. Lindgren, R. M. 1948. Thinning pines cankered by fusiform rust. So. For. Notes 55. Linnartz, N. E. 1961. Pine site index is related to soil classification in southeastern Louisiana. LSU. For. Note 48. Linnartz, N. E. 1963. Relation of soil and topographic characteristics to site quality for southern pines in the Florida Parishes of Louisiana. J. For. 61:434-438. Little, E. L., Jr., and K. W. Dorman. 1954. Slash pine (Pinus elliottii), including South Florida slash pine, nomenclature and description. Southeastern For. Exp. Sta. Paper 36. Livingston, K. W. 1964. Slash pine at Auburnâ&#x20AC;&#x201D;a case history. Auburn U. For. Dept. Series 1. McCulley, R. D. 1950. Management) of natural slash pine stands in the flatwoods of south Georgia and north Florida. USDA Cir. 845. McGee, C. E. 1961. Soil site index for Georgia slash pine. Southeastern For. Exp. Sta. Paper 119. McGee, C. E. 1963. A nutritional study of slash pine seedlings grown in sand culture. For. Sci. 9:461-469. McGee, C. E., and F. A. Bennett. 1959. Site index curves for old field slash pine plantations. Southeastern For. Exp. Sta. Res. Note 127. McGee, C. E., and J. L. Clutter. 1967. A study of site index for planted slash pine. J. For. 65:491-493. McGee, C. E., and J. B. Hatcher. 1963. Deep-planting small slash pine on old field sites in the Carolina Sandhills. J. For. 61:382-383. McGregor, W. H. D. 1957. Fertilizer increases growth rate of slash pine. Southeastern For. Exp. Sta. Res. Note 101. McKellar, A. D. 1942. Ice damage to slash pine, longleaf pine, and loblolly pine plantations in the Piedmont section of Georgia. J. For. 40:794-797. McLemore, B. F. 1961. Estimating pine seed yields. So. For. Notes 134. McLemore, B. F. 1962. Predicting seed yields of southern pine cones. J. For. 60:639-641. McMinn, J. W. 1963. Precommercial thinning of slash pine. USFS Res. Note SE-6.

104

Stephen F. Austin State College

McMinn, J. W. 1965. Pre-commercial thinning in dense young slash pine of north Florida. For. Farmer 24(12) :10-11. McMinn, J. W. 1967. Comparative fire resistance of two seed sources of South Florida slash pine. USFS Res. Note SE-68. Malac, B. F. 1960. Effects of site preparation on success of direct seeding of slash pine. Union Bag-Camp Paper Corp. Woodland Res. Note 6. Malac, B. F. 1962. Slash pine responds to release from hardwood competition. Union Bag-Camp Paper Corp. Woodland Res. Note 12. Malac, B. F. 1965. Planting and direct seeding. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Malac, B. F., and J. W. Johnson. 1957. Deep planting increases survival of slash pine on sandy site. Union Bag & Paper Corp. Woodland Res. Note 5. Malac, B. F., and H. M. Saranthus. 1967. Survey of Fames annosus infection in thinned pine plantations. Union Camp Corp. Woodlands Res. Note 17. Mann, W. F., Jr. 1953. Loblolly outgrows slash on good sites. So. For. Notes 86. Mann, W. P., Jr. 1965. Progress in direct-seeding the southern pines. Proc. "Direct seeding in the Northeastâ&#x20AC;&#x201D;a symposium." U. Mass. Exp. Sta. Bui. Mann, W. F., Jr. 1966. Direct-seeding slash pine. So. Lbrmn. 213 (2656) : 147-150. Mann, W. F., Jr., and H. J. Derr. 1964. Guides for direct-seeding slash pine. USFS Res. Paper SO-12. Mann, W. F., Jr., and H. J. Derr. 1965. How to direct-seed slash pine. For. Farmer 24(11) :6 et fol. Mann, W. F., Jr., and T. Rhame. 1955. Prescribed-burning planted slash pine. So. For. Notes 96. Mann, W. F., Jr., and L. B. Whitaker. 1952. Stand density and pine height growth. So. For. Notes 81. Mann, W. F., Jr., and L. B. Whitaker. 1955. Effects of prescribe-burning 4-year-old planted slash pine. Fire Control Notes 16(3) :3. Marx, D. H., and B. Zak. 1965. Effect of pH on mycorrhizal formation of slash pine in aseptic culture. For. Sci. 11:66-74. Matthews, F. R. 1962. Pitch canker-tip moth damage association on slash pine seedlings. J. For. 60:825-826. Matthews, F. R. 1964. Some aspects of the biology and control of southern cone rust. Phytopathology 62:881-884. Matthews, F. R., and T. F. McLintock. 1958. Effects of fungicides on pollen germination of slash and longleaf pine. Southeastern For. Exp. Sta. Res. Note 122. Mattoon, W. R. 1916. Some characteristics of slash pine. For. Quart. 14:578-588. Mattoon, W. R. 1936 Twenty years of slash pine. J. For. 34:562-570. Mattoon, W. R. 1940. Slash pine. USDA Farmers' Bui. 1256.

Silviculture of Slash Pine

105

Mergen, F. 1954. Heteroplastic micrografting of slash pine. Southeastern For. Exp. Sta. Paper 47. Mergen, F. 1954a. Self-fertilization in slash pine reduces height growth. Southeastern For. Exp. Sta. Res. Note 67. Mergen, F. 1955. Air-layering of slash pines. J. For. 53:265-270. Mergen, F. 1955a. Grafting slash pine in the field and in the greenhouse. J. For. 53:836-842. Mergen, F. 1955b. Inheritance of deformities in slash pine. So. Lbrmn. 190(2370) :30-32. Mergen, F. 1958. Natural polyploidy in slash pine. For. Sci. 4:283-295. Mergen, F., P. E. Hoekstra, and R. M. Echols. 1955. Genetic control of oleoresin yield and viscosity in slash pine. For. Sci. 1:19-30. Mergen, F., and L. E. Koerting. 1957. Initiation and development of flower primordia in slash pine. For. Sci. 3:145-155. Mergen, F., and H. Rossoll. 1954. How to root and graft slash pine. Southeastern For. Exp. Sta. Paper 46. Mergen, F., E. B. Snyder, and J. Burley. 1966. Variation in coastal and insular slash pine of Mississippi and Alabama. Am. Midi. Nat. 76: 482-495. Merkel, E. P. 1961. A study of losses in the 1960 slash pine cone crop. Southeastern For. Exp. Sta. Res. Note 164. Merkel, E. P. 1963. A new southern pine tip moth. J. For. 61:226-227. Merkel, E. P. 1964. Hydraulic spray applications of insecticides for the control of slash pine cone and seed insects. USFS Res. Paper SE-9. Meyer, W. H. 1960. Impressions of industrial forestry in southeastern United States. J. For. 58:179-187. Miller, S. R. 1957. Germination of slash pine seed following submergence in water. Union Bag & Paper Corp. Woodland Res. Note 3. Moulds, F. R., and M. B. Applequist. 1957. Fertilizers successful in stimulating growth of pine plantations in Australia. LSU For. Note 13. Muntz, H. H. 1948. Close spacing reduces fusiform rust. So. For. Notes 53. Muntz, H. H. 1948a. Slash pine versus loblolly in central Louisiana. J. For. 46:766-767. Muntz, H. H., and H. J. Derr. 1949. Early release helps underplanted pines. So. For. Notes 64. Nelson, T. C. 1952. Early competition in slash pine plantations. Southeastern For. Exp. Sta. Res. Note 10. Nelson, T. C., and G. W. Stanley. 1959. Hurricane damage related to thinning intensity in East Texas slash pine plantations. J. For. 57:39. Nienstaedt, H., F. C. Cech, F. Mergen, C. Wang, and B. Zak. 1958. Vegetative propagation in forest genetics research and practice. J. For. 56:826839. Odum, E. P. 1960. Organic production and turnover in old field succession. Ecol. 41:34-49. Olden, J. S. 1954. Slash pine sprouts. J. For. 52:41.

106

Stephen F. Austin State College

Olson, D. F., Jr., R. W. Cooper, N. E. Sands, and S. Krock. 1954. Drainage can create new slash pine sites. So. Lbrmn. 189 (Dec. 15) :112-114. Ostrom, C. E., R. P. True, and C. S. Schopmeyer. 1958. Role of chemical treatment in stimulating resin flow. For. Sci. 4:296-306. Ostrom, C. E., and W. Waring. 1946. Effect of chemical stimulation of gum flow on carbohydrate reserves in slash pine. J. For. 44:1076-1081. Peevy, F. A. 1953. Hogs still prefer longleaf. So. For. Notes 87. Perry, T. 0. 1955. A grafting technique for forest genetics research. J. For. 53:33. Perry, T. O. 1960. Pruning of slash and loblolly pine grafts. J. For. 58:323. Perry, T. O., and C. Wang. 1957. Collection, shipping, and storage of slash and loblolly pine cuttings. J. For. 55:122-123. Pessin, L. J. 1938. Effect of soil moisture on the rate of growth of longleaf and slash pine seedlings. Plant Physiol. 13:179-189. Pomeroy, K. B., and R. W. Cooper. 1956. Growing slash pine. USDA Farmers' Bui. 2103. Powers, H. R., Jr. 1962. Fusiform rust and Annosus root rotâ&#x20AC;&#x201D;the South's most serious plantation diseases. Proc. Soc. Am. For. Powers, H. R., Jr., and J. S. Boyce, Jr. 1963. Annosus root rot in eastern pines. USDA For. Pest Leaflet 76. Powers, H. R., and A. F. Verrall. 1962. A closer look at Fames annosus. For. Farmer 21(13) :8 et fol. Pritchett, W. L., and T. 0. Perry. 1959. Fertilizing slash pine plantations. For. Farmer 18 (6) :6 et fol. Pritchett, W. L., and K. R. Swinford. 1961. Response of slash pine to colloidal phosphate fertilization. Soil Sci. Soc. Am. Proc. 25:397-400. Pruitt, A. A. 1947. A study of the effects of soils, water tables, and drainage on the height growth of slash and loblolly pine plantations on the Hofmann Forest. J. For. 45:836. Ralston, C. W. 1951. Some factors related to the growth of longleaf pine in the Atlantic Coastal Plain. J. For. 49:408-412. Ralston, C. W., and R. L. Barnes. 1955. Soil properties related to the growth and yield of slash pine plantations in Florida. Soil Sci. Soc. Am. Proc. 19:84-85. Ralston, C. W., and C. E. McGee. 1962. Planting turkey oak sites with slash pine may not pay. J. For. 60:719-724. Reines, M. 1963. The influence of age of clonal parent on rooting of needle bundles. Ga. For. Res. Paper 16. Reines, M., and J. H. Bamping. 1960. Seasonal rooting responses of slash and loblolly pine cuttings. J. For. 58:646-647. Reines M., and J. H. Bamping. 1962. Carbohydrates and seasonal rooting of cuttings. Ga. For. Res. Paper 9. Reines, M., and R. G. McAlpine. 1959. The morphology of normal, callused, and rooted dwarf shoots of slash pine. Bot. Gaz. 121:118-124. Richards, B. N. 1956. The effect of phosphate on slash and loblolly pine in Queensland. Queensland For. Serv. Res. Note 5:1-11.

Silviculture of Slash, fvne

107

Roberts, E. G., and R. T. Clapp. 1956. Effect of pruning on the recovery of ice bent slash pines. J. For. 54:596-597. Rosenkrans, D. B. 1944. Slash pine produces viable seed north of its natural range. J. For. 42:685. Row, C. 1960. Soil-site relations of old field slash pine plantations in Carolina Sandhills. J. For. 58:704-707. Rowland, C. A., Jr. 1950. Early results of bud-pruning in slash pine. J. For. 48:100-103. Rummell, R. S. 1958. Cattle stocking and herbage yield on burned flatwoods ranges. Southeastern For. Exp. Sta. Res. Note 118. Russell, T. E. 1958. Cricket hazard. For. Farmer 17 (12): 12 et fol. Russell, T. E. 1958a. Spacingâ&#x20AC;&#x201D;its role in the growth of planted slash pine. So. Lbrmn. 197 (Dec. 15) : 115-117. Russell, T. E., and T. E. Rhame. 1960. Disk before seeding slash pine. So. For. Notes 130. Schaeffer, G. K. 1954. Strip cutting in dense pine stands on Oceola National Forest. Fire Control Notes 15(1) : 12-13. Scheer, R. L. 1959. Comparison of pine species on Florida sandhills. J. For. 57:416-419. Scheer, R. L., and F. W. Woods. 1959. Intensity of preplanting site preparation required for Florida's sandhills. So. For. Exp. Sta. Occ. Paper 168. Schopmeyer, C. S. 1953. The characteristics of a high-gum-yielding tree. Southeastern For. Exp. Sta. Res. Note 39. Schopmeyer, C. S. 1955. Effects of turpentining on growth of slash pine: first-year results. For. Sci. 1:83-87. Schopmeyer, C. S., and P. R. Larson. 1954. Gum-yield tables for slash and longleaf pine on poorer than average sites. Naval Stores Rev. 65(11) : 14-15. Schopmeyer, C. S., and P. R. Larson. 1955. Effects of diameter, crown ratio, and growth rate on gum yields of slash and longleaf pine. J. For. 53:822-826. Schopmeyer, C. S., and O. C. Maloy. 1960. Dry face of naval stores pines. USDA For. Pest Leaflet 51. Schopmeyer, C. S., F. Mergen, and T. C. Evans. 1954. Applicability of Poiseuille's law to exudation of oleoresin from wounds of slash pine. Plant Physiol. 29:82-87. Schultz, A. J. 1961. A second report on interplanted slash pine. Southeastern For. Exp. Sta. Res. Note 154. Schultz, A. J. 1965. Replacement planting. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Schultz, R. P., and L. P. Wilhite. 1967. Operational summer planting of slash pine. USFS Res. Note SE-80. Sentell, N. W. 1949. Pales weevil damages plantations in Louisiana. J. For. 47:741.

108

Stephen F. Austin State College

Shipman, R. D. 1963. Seedling depthâ&#x20AC;&#x201D;its influence on establishment of direct-seeded pine in the South Carolina Sandhills. J. For. 61:907-912. Shipman, R. D. 1964. Low seedbed densities can improve early height growth of planted slash and loblolly pine seedlings. J. For. 62:814-817. Shoulders, E. 1958. Scalping. For. Farmer 17(10) : 10-11. Shoulders, E. 1960. Town ants damage slash pine plantation. So. For. Notes 125. Shoulders, E. 1961. Effect of nursery bed density on loblolly and slash pine seedlings. J. For. 59:576-579. Shoulders, E. 1961a. Effect of seed size on germination, growth, and survival of slash pine. J. For. 59:363-365. Shoulders, E. 1962. Deep-planted seedlings survive and grow well. So. For. Notes 140. Shoulders, E. 1963. Root-pruning southern pines in the nursery. USFS Res. Paper SO-5. Shoulders, E. 1967. Growth of slash and longleaf pines after cultivation, fertilization, and thinning. USFS Res. Note SO-59. Shoulders, E. 1968. Fertilization increases longleaf and slash pine flower and cone crops in Louisiana. J. For. 66:193-197. Siggers, P. V. 1949. Weather and outbreaks of the fusiform rust of southern pines. J. For. 47:802-806. Siggers, P. V. 1955. Control of the fusiform rust of southern pines. J. For. 53:442-446. Silker, T. H. 1956. Prescribed burning in the silviculture and management of southern pine-hardwood and slash pine stands. Proc. Soc. Am. For. Silker, T. H. 1956a. Procedures for prescribed burning in pine-hardwood stands and slash pine plantations for the control of undesirable hardwoods on flatwood sites. Texas For. Serv. Cir. 47. Silker, T. H. 1961. Prescribed burning to control undesirable hardwoods in southern pine stands. Texas For. Serv. Bui. 51. Silker, T. H., and R. E. Goddard. 1953. Direct seeding tests with slash, loblolly and longleaf pine in southeast Texas. Texas For. Serv. Rept. 7. Sleeth, B. 1940. Mortality of slash pine seedlings infected by Cronartium fusiforme. So. For. Exp. Sta. Note 35. Smalley, G. W., and R. L. Scheer. 1963. Black root rot in Florida sandhills. Plant Disease Reporter 47:669-671. Smith, L. F. 1960. Early growth of slash pine on upland and wet sites. J. For. 58:720-725. Smith, L. F. 1963. Controlling shrubs on wet slash pine sites. USFS Res. Note SO-4. Smith, L. F. 1967. Effects of spacing and site on the growth and yield of planted slash pine. USFS Res. Note SO-63. Smith, R. H. 1954. Benzene hexachloride controls black turpentine beetle. So. Lbrmn. 189(Dec. 15) =155-157. Smith, R. H. 1955. A control for the black turpentine beetle in South Georgia and North Florida. Southeastern For. Exp. Sta. Res. Note 76.

Silviculture of Slash Pine

109

Smith, R. H. 1956. Death of a pine. For. Farmer 15(12) :7. Smith, R. H. 1958. Control of the turpentine bettle in naval stores stands by spraying attacked trees with benzene hexachloride. J. For. 56:190194. Smith, R. H., and F. Mergen. 1954. A bark beetle attacking scions of grafted slash pines. J. For. 52:864-865. Smith, R. H., and F. Mergen. 1954a. Pityophthorus pulicarius (Zimm.), a bark beetle attacking scions of grafted slash pines. Southeastern For. Exp. Sta. Res. Note 64. Snow, A. G., Jr. 1953. Progress in development of efficient turpentining methods. Southeastern For. Exp. Sta. Paper 32. Snow, A. G., Jr., K. W. Dorman, and C. S. Schopmeyer. 1943. Developmental stages of female strobili in slash pine. J. For. 41:922-923. Snyder, E. B., A. E. Squillace, and J. M. Hamaker. 1966. Pigment inheritance in slash pine seedlings. Proc. 8th So. Conf. For. Tree Improvement. Soc. Am. For., Appal. Section. 1945. Cutting practices for the Carolinas. J. For. 43:861-870. Southeastern For. Exp. Sta. 1959, 1960, 1961. Annual reports. So. For. Exp. Sta. 1957, 1958, I960, 1962. Annual reports. Speers, C. F. 1958. Pales weevil rapidly becoming serious pest of pine reproduction in the South. J. For. 56:723-726. Squillace, A. E. 1966. Racial variation in slash pine as affected by climatic factors. USFS Res. Paper SE-21. Squillace, A. E., and G. W. Bengtson. 1961. Inheritance of gum yield and other characteristics of slash pine. Proc. 6th So. Conf. For. Tree Improvement. Squillace, A. E., and K. W. Dorman. 1959. Selective breeding of slash pine for high oleoresin yield and other characters. Proc. 9th Int. Bot. Cong. Squillace, A. E., and J. F. Kraus. 1959. Early results of a seed source study of slash pine in Georgia and Florida. Proc. 5th So. Conf. For. Tree Improvement. Squires, J. W. 1947. Prescribed burning in Florida. J. For. 45:815-819. Stahelin, R. 1949. Thinning even-aged loblolly and slash pine stands to specified densities. J. For. 47:538-540. Stephens, E. J. 1956. The effects of duration of flooding upon seed viability. Unpub. M. F. Thesis, Duke Univ. Stevenson, D. D., and D. D. Schores. 1961. A case history of industrial forest management in north central Florida. J. For. 59:411-416. Storey, T. G., and E. P. Merkel. 1960. Mortality in a longleaf slash pine stand following a winter fire. J. For. 58:206-210. Stransky, J. J., and D. R. Wilson. 1966. Pine seedling survival under simulated drought. USFS Res. Note SO-30. Swearingen, J. W. 1963. Effects of seedling size and depth of planting on early survival and growth of slash pine. Tree Planters' Notes 58:16-17.

110

Stephen F. Austin State College

Texas For. Serv. 1961. Ninth progress report of cooperative forest tree improvement program of the Texas Forest Service. Cir. 67. Texas For. Serv. 1966. 14th progress report of cooperative forest tree improvement program. Cir. 104. Todd, A. S., Jr., and J. G. Yoho. 1962. Forestry in the southern economy. J. For. 60:696-697. True, R. P., and A. G. Snow, Jr. 1949. Gum flow from turpentine pines inoculated with the pitch canker Fusarium. J. For. 47:894-899. U.S. For. Serv. 1965. Silvics of forest trees of the United States. Agr. Handbook 271. VanHaverbeke, D. F., and J. C. Barber. 1961. Less growth and no increased flowering from changing slash pine branch angle. So. For. Exp. Sta. Res. Note 167. Varnell, R. A., and F. A. Bennett. 1966. Direct seeding on flatwood sites. For. Farmer 25(5) :8 et fol. Verrall, A. F. 1958. Fusiform rust of southern pines. USDA For. Pest Leaflet 26. Verrall, A. F. 1961. Spread of Cronartium fusiforme branch infections. Phytopathology 51:646. Verrall, A. F. 1962. Annosus root rot survey. So. For. Notes 141. Wahlenberg, W. G. 1946. Longleaf pine. Chas. Lathrop Pack For. Foundation. Wakeley, P. C. 1947. The 1947 cone crop and forest fires. So. For. Notes 51. Wakeley, P. C. 1961. Results of the Southwide Pine Seed Source Study through 1960-61. So. For. Exp. Sta. Walker, L. C. 1962. Fertilizing flooded forests. Better Crops with Plant Food 46(l):40-43. Walker, L. C. 1962a. Water and fertilizer effects on loblolly pine and slash pine seedlings. Soil Sci. Soc. Am. Proc. 26:197-200. Walker, L. C. 1965. Fertilization for pine plantations. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Kept. 14. Walker, L. C. 1967. Effects of water level and fertilizer combinations on loblolly and slash pine seedlings. Tree Planters' Notes 18(1) : 10-12. Walker, L. C. 1967a. Nitrogen benefits slash pine for 5 years. Tree Planters' Notes 18(1) :21-22. Walker, L. C., and R. L. Green. 1961. Draining pine forests. For. Farmer .20(6) :8 et fol. Walker, L. C., R. L. Green, and J. M. Daniels. 1961. Flooding and drainage effects on slash pine and loblolly pine seedlings. For. Sci. 7:2-15. Walker, L. C., and R. D. Hatcher. 1965. Variation in the ability of slash pine progeny groups to absorb nutrients. Soil Sci. Soc. Am. Proc. 29:616-621. Walker, L. C., and J. C. Morcock, Jr. 1965. Fertilization of a 21-year-old slash pine stand. Castanea 30:81-84. Walker, L. C., and C. T. Youngberg, 1962. Response of slash pine to nitrogen and phosphorus fertilization. Soil Sci. Soc. Am. Proc. 26:399-401.

Silviculture of Slash Pine

111

Wallace, R. J. 1960. Growth and yield on an East Texas slash pine plantation. For. Farmer 19 (11) :14. Webster, C. B. 1931. Notes on growth of slash pine in Texas. J. For. 29:425-426. Westberg, D. L. 1949. Fusiform rust on plantations of cultivated and fertilized pine. Ala. Agr. Exp. Sta. 60th Ann. Rept. Westberg, D. L. 1951. Cultivating boosts fusiform rust infection. J. For. 49:253. Wilhite, L. P. 1966. Summer planting of slash pine shows promise in Florida. USFS Res. Paper SE-23. Wilhite, L. P., and T. A. Harrington. 1965. Site preparation. In: A guide to loblolly and slash pine plantation management in southeastern USA. W. G. Wahlenberg (ed.). Ga. For. Res. Council Rept. 14. Williams, R. F., and J. R. Hamilton. 1961. The effect of fertilization on four wood properties of slash pine J. For. 59:662-665. Williston, H. L. 1959. Growth of four southern pines in west Tennessee. J. For. 57:661-662. Williston, H. L. 1963. Early yield of erosion-control plantations in north Mississippi. USFS Res. Note SO-1. Williston, H. L., and B. J. Huckenpahler. 1958. Response of six conifers in north Mississippi underplantings. J. For. 56:135-137. Woods, F. W. 1956. Relation of soil moisture and temperature to weed control. Proc. So. Weed Conf. Woods, F. W. 1957. Factors limiting root penetration in deep sands of the southeastern Coastal Plain. Ecol. 38:357-359. Woods, F. W. 1958. Some effects of site preparation on soil moisture in sandhills of west Florida. Soil Sci. 85:148-155. Woods, F. W. 1959. Converting scrub oak sandhills to pine forests in Florida. J. For. 57:117-119. Woods, F. W. (ed.). 1959a. Direct seeding in the South, a symposium. Duke Univ. School of For. Woods, F. W. 1959b. Slash pine roots start growth soon after planting. J. For. 57:209. Woods, F. W., J. T. Cassady, and H. Rossoll. 1958. How to prepare Gulfcoast sandhills for planting pines. So. For. Exp. Sta. Occ. Paper 161. Woods, F. W., E. A. Hebb, and D. L. Fassnacht. 1956. Mulch not beneficial to seedlings on deep sands. J. For. 54:595. Worst, R. H. 1964. A study of effects of site preparation and spacing on planted slash pine in the Coastal Plain of southeast Georgia. J. For. 62:556-560. Yates, H. 0. 1962. Influence of tip moth larvae on oleoresin crystallization of southern pines. So. For. Exp. Sta, Res. Notes 174. Yates, H. O., and R. H. Beal. 1962. Nantucket pine tip moth. USDA For. Pest Leaflet 70. Young, H. E. 1948. The response of loblolly and slash pines to phosphate manures. Queensland J. Agr. Sci. 5:77-105.

112

Stephen F. Austin State College

Zak, B., and R. G. McAlpine. 1957. Rooting of shortleaf and slash pine needle bundles. Southeastern For. Exp. Sta. Res. Note 112. Zak, B., and D. H. Marx. 1964. Isolation of mycorrhizal fungi from roots of individual slash pines. For. Sci. 10:214-221.

Silviculture of Slash Pine APPENDIX Common and scientific names of species mentioned in the text. Baldcypresa Maple, Red Oak, Blackjack Bluejack Laurel Live Scarlet Southern Red Turkey Water Willow Pine, Loblolly Longleaf Monterey Sand Shortleaf Slash Sonderegger South Florida Slash Virginia Tupelo, Black Swamp

Trees Taxodium distichum Acer rubrum Quercus marilandica incana laurifolia virginiana coccinea falcata laevis nigra phellos Pinus taeda palustris radiata clausa echinata elliottii sondereggeri elliottii var..densa virginiana Nyssa sylvatica 'sylvatica var. biflora

Gallberry, Big Bitter Titi, Black White

Shrubs Ilex coriacea glabra Cliftonia monophylla Cyrilla racemiflora

Broomsedge Pea, Cow Watermelon Wiregrass

Herbs, Vines, and Grasses Andropogon virginicus Vigna sinensis Citrullus vulgaris Andropogon scoparius

Gopher, Pocket Rat, Cotton Squirrel Beetle, Ambrosia Black Turpentine Red Turpentine Pine Engraver Bark Cricket Moth, Nantucket Pine Tip Thrips

Mammals Geomys spp. and Cratogeomys spp. Sigmodon spp. Sciurus spp. Insects Monarthrum spp. Dendroctonus terebrans valens Ips spp. Anurgryllus muticus Rhyacionia frustrana Gnophothrips piniphilus

113

— NOTES —

PREVIOUS BULLETINS 1. References of value in studies of insects affecting the southern pines, an annotated list, by R. C. Thatcher. 1957. (Out of print.) 2. Directory of wood-using and related industries in East Texas, by N. T. Samson. 1957. (Out of print.) 3. Bibliography of forestry films and filmstrips, by N. T. Samson. 1958. (Out of print.) 4. Root development of loblolly pine seedlings in modified environments, by M. V. Bilan. 1960. 5. Continuous forest inventory with punched card machines for a small property, by R. D. Baker and E. V. Hunt, Jr. 1960. 6. Point-sampling from two angles, by E. V. Hunt, Jr., R. D. Baker, and L. A. Biskamp. 1964. (Out of print.) 7. Films and filmstrips on forestry, by N. T. Samson. 1965. (Out of print.) 8. Soil moisture and soil temperature under a post oak-shortleaf pine stand, by G. Schneider and J. J. Stransky. 1966. 9. Silviculture of shortleaf pine, by L. C. Walker and H. V. Wiant, Jr. 1966. Price $1. 10. Texas pulpwood production, by N. T. Samson. 1966. 11. Silviculture of longleaf pine, by L. C. Walker and H. V. Wiant, Jr. 1966. Price $1. 12. Pine seedling survival and growth response to soils of the Texas Postoak Belt, by M. V, Bilan and J. J. Stransky. 1966. 13. Directory of wood-using and related industries in East Texas, by N. T. Samson. 1966. Price $2. 14. Practical point-sampling, by E. V. Hunt, Jr. and R. D. Baker. 1967. Price $1. 15. Silviculture of the minor southern conifers, by L. C. Walker. 1967. Price $1.