Forest floor and soil nutrient conditions in the Georgia Sandhills / by Charles E. Pehl and Henry E. Shelnutt, Jr

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GEORGIA FOREST 62

RESEARCH PAPER

1ARCH, 1986

v.

V

FOREST FLOOR And SOIL NUTRIENT CONDITIONS

In The Georgia Sandhills

Received

By
Charles E. Pehl
and Henry E. Shellnuttjr.

MAY 30 1988
DOCUMENTS UGA LIBRARIES

A
r GEORGIA ^

FORESTRY,
%M#

RESEARCH DIVISION

GEORGIA FORESTRY COMMISSION

AUTHORS

Charles E. Pehl was Assistant Professor,

Forest Soils, School of Forest Resources,

University of Georgia from August 1980

to June 1985. He received a Bachelor of

Science from the United States Naval

Academy and a Master's and PHD in

A&M forestry at Texas

University.

Henry E. Shelnutt, Jr. is a Research Technician, level III, Tissue Culture Laboratory, School of Forest Resources, University of Georgia. He is a graduate of Athens Technical College and is currently working on a Bachelor's Degree in Micro-
biology.

FOREST FLOOR
And
SOIL NUTRIENT CONDITIONS
In The Georgia Sandhills
ABSTRACT
The forest floor and soil were sampled beneath a slash pine plantation and longleaf pine-turkey oak association in the Georgia Sandhills of Marion County. Concentration of nutrients in the forest floor and the relatively low soil extractable nutrient levels demonstrated the importance of the forest floor to the nutrient cycle on excessively drained Sandhill sites. Site preparation methods, such as chopping and herbicides which minimize surface soil disturbance were recommended as optimal for dry Sandhills sites.
Charles E. Pehl
and Henry E. Shelnutt, Jr,

Introduction

The Georgia Sandhills occur in a narrow band, just south of the Piedmont, extending from Augusta to Columbus. Relief is rolling to hilly (Giddens et al., 1960). Native vegetation consists primarily of the longleaf-scrub oak association. Longleaf pine once formed pure open stands, but logging and fire control reduced the pine component in favor of scrub oak (Van Lear, 1980). Poor survival, slow growth and high regeneration costs have prevented extensive longleaf regeneration. Other pine species, slash, loblolly and sand pine have been planted with varying results (Van Learet al., 1977; Hebb, 1981).
Sandhill soils are deep, infertile, well drained sands, fairly
productive agriculturally when fertilized and irrigated frequent-
ly. For such nutrient poor soils, the forest floor is an importaat

source of added nutrient to the available soil nutrient pool (Armson, 1977). Through uptake and deposition, forest vegetation concentrates limited nutrients at the soil surface. Decomposition of the floor eventually releases these nutrients for plant uptake. Pine forests normally develop an evenly distributed floor; in the longleaf scrub oak association, however, the floor is often incomplete with large areas of open sand (Wharton, 1978).
The objective of this study was to contrast within a Sandhills site, the influence of a slash pine plantation and a longleaf-scrub oak association on the forest floor and available soil nutrient pool. Such information could then be used by forest managers
to evaluate the long-term inflences of various site preparation methods on Sandhills site productivity.

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Typical V'-Blade installed on crawler tractor to do site preparation work

>4/-ea of harvested forest land prior to site preparation and replanting.

Procedures

The study was located in Marion County, Georgia. The area

had an average of 127 cm (50 in) evenly distributed, annual

rainfall (Giddens, et al., 1960). The site was a long, broad, sandy

ridge with a portion regenerated to slash pine, and adjacent

areas of scrub oak. From field descriptions, the soil was deter-

mined to be a Lakeland series (Typic Quartzipsamment).

The slash plantation, regenerated on an abandoned peanut

field was 22 years old. Stand density was 800 trees/ha (320
trees/acre). Average diameter at breast heaight was 19.5 cm

(7.6 in); average height of dominants and codominants was 7.4
m cm (62 ft) for a site index at base age 25 of 22 (72 ft). The

scrub oak association was predominantly turkey oak with only a

few scattered longleaf pine.

Forest floor and soils were sampled for both associations in

early June, 1984. Three 0.04 ha (0.1 acre) measurement plots

were established in each association for a total of six sample

plots.

Within

each

plot,

ten o.25m 2

(2.7

2
ft )

quadrats were

ran-

domly located. The forest floor (to mineral soil) was removed in

two layers. Both layers were oven-dried (70C), weighed and
ground. A lower layer subsample (3.0 g) was ashed (600C) to
determine percent soil contaminant for each quadrat. The floor

samples were wet ash digested using a 7:1 concentration nitric/

perchloric acid solution (Chapman and Pratt, 1961). Forest

floor Ca, Mg and K were determined by atomic adsorption spectrophotometry (Perkin-Elmer, 1976). Total N was deter-
mined with a sulfuric and selenous acid, hydrogen peroxide digestion using a technicon II unit (Issac and Johnson, 1976).
The soil was sampled at four depths; 0-8 cm, 8-15 cm, 15-46
cm and 46-91 cm. The first two depths were sampled beneath each forest floor quadrat for 10 samples per plot. The last two
depths were sampled beneath the 3rd, 6th and 9th quadrats for three samples per plot. Bulk densities at each depth were determined in three pits in the slash plantation using the core method
(Blake, 1965). Soils were sieved (2 mm) and extracted with a
Melich I solution (University of Georgia, 1983) and analyzed
for organic matter, total N, P, K, Ca, Mg and pH. Organic matter was determined by the Walkley-Black Method (Jackson,
1958). Total nitrogen was determined by the macro-kjeldahl method using a Technicon autoanalyzer (Technicon, 1975). Extractable Ca, Mg, Na and K were determined by atomic adsorption spectrophotometry (Perkin-Elmer, 1976). Extractable P was determined using a Technicon autoanalyzer II (Technicon, 1975). Soil pH was determined using a 1:1 soil/ water paste (Peech, 1965). Nutrients weights (kg/ha) were calculated from extractable concentrations and bulk densitites.

Results

Forest Floor Conditions
Based on field observation and measurement, the forest floor beneath the slash pine plantation was continuous with an average thickness of 3.1 (0.4) cm. The scrub oak association floor was generally discontinuous with average thickness 1.3
(0.2) cm with about 38% of the area either bare or with little
litter cover. Total floor weights under the slash pine were significantly larger (a = 0.05 level) than under the scrub oak (Table 1), resulting in higher total nutrient weight concentrated in the forest floor under the slash plantation after 22 years.
Forest floor nutrient weights for the Sandhills slash pine plantation were similar to values reported for loblolly pine in the U. S. Coastal Plain and Piedmont as well as mixed hard-
woods in the Piedmont and Douglas-fir in the Pacific Northwest (Table 2). The scrub oak forest floor weights were lower, particularly for P, K and Mg.

Soil Conditions
The soil beneath the forest floor of both associations was strongly acid throughout with low cation exchange capacity (CEC) and low base saturation (BS) (Table 3). Organic matter in the upper 15 cm was significantly higher under the scrub
oak. Although organic matter has a CEC of 200 meq/100g,
the increase was not sufficient to significantly influence the overall CEC.
With the exception of P, extractable nutrient concentrations were low, reflecting the general low fertility associated with the Sandhills and did not differ significantly with forest association (Table 4). Extractable P was significantly higher in the top 15
cm of the slash plantation, but that probably reflected the long
term effects of residual fertilization. Extractable Ca was higher
in the surface 8 cm under the scrub oak and Mg higher under
the scrub oak at 46 to 91 cm.

Table 1. Forest floor total biomass and mean nutrient weights for two forest associations in the Georgia Sandhills.

Association Floor Weights

N

(ton/ha)

Slash Pine

28.5(4.4)

303(62)

10.2(1.9)

ScrubOak 11.7(2.5)

143(47)

3.0(1.1)

Means given with 95% confidence intervals.

K
(kg/ha) 10.6(1.9)
3.6(1.4)

Ca
157.7(42.1) 34.1(14.3)

Mg
7.9(1.5) 2.9(1.1)

Table 2. Comparison of forest floor nutrient weights for various species and regions.

Association

Region

N

P

K

Ca

Mg

-(kg/ha)-

Loblolly

Coastal Plain

171

8

14

84

14

Loblolly Pine

Coastal Plain

124

9

16

80

15

Loblolly Pine

Piedmont

351

21

27

202

42

Loblolly Pine

Piedmont

307

30

28

Mixed hardwoods Piedmont

408

16

21

366

40

Douglas-fir

Pacific Northwest

175

26

32

137

Slash Pine
Scrub Oak

Sandhills Sandhills

303

10

11

153

8

143

3

4

34

3

Source
Tuttle, 1978 Switzer and Nelson, 1972 Bandaratillake, 1985 Jorgensen et al.. 1975 Bandaratillake, 1985 Coleet al., 1968 Present Study Present Study

Table 3. Soil chemical properties for two forest associations in the Georgia Sandhills.

Association

Soil Properties

pH

Organic

Cation

Base

matter

Exchange

Saturation

(CEC)

(BS)

(%)

(meq/100g)

(%)

Depth 1 (0-8 cm)

Slash Pine
Scrub Oak

5.1 (0.10) 5.2 (0.12)

1.17(0.19) b 1.92(0.20)
a

5.5(0.7) 4.5(0.7)

Depth 2 (8-15 cm)

6.0(1.3) 9.4 (2.3)

Slash Pine
Scrub Oak

5.3 (0.13) 5.3 (0.12)

0.66 (0.07) b 1.03(0.09L
d

4.3 (0.5) 3.5(0.6)

Depth 3 (15-46 cm)

6.6(1.4) 5.7 (0.9)

Slash Pine
Scrub Oak

5.5 (0.22) 5.2 (0.23)

0.44(0.12) 0.54(0.23)

3.8(1.2) 2.6(1.0)

5.9(1.8) 8.4 (2.6)

Depth 4 (46-91)

Slash Pine
Scrub Oak

5.3 (0.08) 5.2 (0.17)

0.39(0.34) 0.42(0.17)

3.5(1.3) 2.6(1.1)

5.9 (2.8) 7.4(1.9)

Means given with 95% confidence intervals.
Means with different subscripts differ significantly (0.05)

Table 4. Extractable soil nutrients means for two forest associations in the Geo rgia
Sandhills.

Association

Extractable Nutrients

N

P

K

Ca

Mg

(ug/g)-

Slash pine Scrub oak
Slash pine Scrub oak
Slash pine Scrub oak

368 (44) 418 (52)
280 (32) 304 (29)
206 (49) 223(53)

Depth 1 (0-8 cm)

15.2(2.5) 1.0(0.2) b

5.1 (0.9) 6.2 (0.9)

29.3 (7.0) b 47.1 (16.0)
a

Depth 2 (8-15 cm)

4.5 (0.7) 6.0(1.0)

12.6(2.9) 1.1 (0.2) b

2.8 (0.5) 4.9 (4.0)

28.9(10.3) 9.7 (1.6)

Depth 3 (15-46 cm)

3.1 (0.6) 2.4 (0.3)

1.8(1.1) 1.0(0.2)

1.7 (0.8)
3.0(1.1)

19.6(11.6) 14.7 (5.3)

2.6(1.0) 2.9(1.1)

Depth 4 (46-91 cm)

Slash pine
Scruboak

182(67) 177(46)

1.7(0.4) 1.3(1.0)

1.4(0.4) 1.8(0.7)

12.0(2.7) 9.6(2.8)

Means given with 95% confidence intervals.
Means with different subscripts differ significantly (a = 0.05)

1.6(0.3) b 2.7(0.9)
3

-

Conversion of extractable concentrations and organic matter to kg/ha illustrates the relative importance of the top few centi-
meters of soil. Although 8% of the total soil (0-91 cm) by
weight, the surface (0-8 cm) accounts for 24, 15, 17, 16 and
13% respectively of the percent organic matter, N, K, Ca, Mg
(Table 5). Surface soil P was only 7%. The general infertility of the Sandhills' soil nutrient pools
from the apparent in comparison with extractable soil nutrient pools from the Georgia Piedmont (Table 6). The soil for both Sandhills forest associations is low particularly in N, P, K, which may be limiting on these sites. Increased annual growth was re-

ported for similar slash pine Sandhills sites in Florida (Typic and
Aquic Quartzipsamments) when fertilized with an NPK treat-
ment (Pritchett and Comerford, 1982).
Comparison of nutrient weights in the soil and forest floor of both Sandhills associations emphasizes the importance of the forest floor to the stand's capacity for resupply of the soil available nutrient pool -(Figure 1). Forest floor N levels for both associations are nearly 100 times the levels extracted from the soil (0-91 cm). For these sites, the forest floor is also a major source of P, K, Ca and Mg.

Table 5. Mean nutrient weights for soil beneath a Long leaf-Scrub Oak associa-
tion in the Georgia Sandhills.

Depth

Organic

Matter

N

Extractable Nutrients

P

K

Ca

Mg

(cm)

- - -fkn/hal-

0-8 0-91

194.1 802.8

4.2 28.3

0.01 0.15

0.06 0.36

0.30 1.82

0.05 0.38

Table 6. Comparison of soil extractable nutrients from the Piedmont and Sandhills of Georgia.

Species

Region

Depth

N

+ P

K

Ca

Mg

- -(kg/ha)

Source

Loblolly pine

Piedmont

(0-60 cm)

2984

13

Mixed hardwood

Piedmont

(0-60 cm)

3239

16

466 503

569 199

464 565

Bandaratillake, 1985 Bandaratillake, 1985

Slash pine
Scrub Oak

Sandhills Sandhills

(0-91 cm) (0-91 cm)

27

0.5

28

0.2

0.2

2.2

0.3 Present Study

0.4

1.8

0.4 Present Study

Melich I extraction used for both studies.

Conclusions

The contributions of the forest floor to the Sandhills nutrient cycle and the generally low soil nutrient levels have important silvicultural implications when regenerating these sites for forest production. Research on Lakeland series sites in the western Florida Sandhills reported that mechanical site preparation gave consistently good results when sites were completely denuded. However, growth was better on double chop treatment areas than on root raked areas in which much of the surface soil had been removed as a result of the operation (Woods, 1959). Furthermore, soil organic matter was consistently higher on the chopped sites.
Site preparation increases seedling survival and growth through control of non-crop vegetation which competes with the crop species for light, water and nutrients (Prtichett, 1979).
On excessively drained sites such as the Sandhills, water and

nutrients are critical. Methods such as shearing or root raking which scrape the site and pile vegetation in windrows produce the most intense competition control but also remove much of the limited nutrients available for stand generation. Chopping retains organic material on site by incorporating organic material into the surface, but results in less intensive vegetation control. Choice of site preparation method then becomes a tradeoff between control of competing vegetation, available water and nutrient resupply. The optimal site preparation prescription for excessively drained Georgia Sandhills sites would be similar to those recommended for sandhills in Florida, double chop with some additional vegetation control from herbicides (Brendemuehl, 1981; Hebb, 1981; Burns and Hebb, 1972). Competing vegetation control is optimized with minimal surface soil
disturbance.

300

N

^O 200

40

oo

^

Ll_ 10.0

w 8.0

o
Li. 3.0 -

0.0
^1.0 O 2.0
3.0
^
& 20

30

Ca
Q

K
Mg
kH

MM

MM

Slash Pine
I, Jl Scrub Oak ,

Figure 1 . Forest floor and soil nutrient weights (kg/ha) for two forest types in the Georgia Sandhills.

Digitized by the Internet Archive in 2013
http://archive.org/details/forestfloorsoiln62pehl

3 2106 DMSSM E5A2

Literature Cited

Armson, K. A. 1977. Forest soils: properties and processes. University of Toronto Press, Toronto and Buffalo. 390p.

Bandaratillake, H. M. 1985. The influence of forest vegetation on soil characteristics in the Georgia Piedmont.
Unpublished Master's Thesis, University of Georgia, Athens, GA 77p.

Blake, G. R. 1965. Bulk density. In Methods of Soil Analysis, Part I, (C. A. Black, ed.) Agronomy Monograph No. 9

Amer. Soc. of Agronomy, Inc., Madison, Wisconsin. 770p.

Brendemuehl, R. H. 1981. Options for management of Sandhill forest land. So. J. of Applied For. 5(4) :21 6-222.
Burns, R. M. and E. A. Hebb. 1972. Site preparation and reforestation of droughty, acid sands. USDA For. Serv.

Agric. Handb. 426. 61 p. Chapman, H. D. and P. F. Pratt. 1961. Methods of analysis for soils, plants and waters. University of California,

Berkeley, California.

Cole, D. W., S. P. Gessel and S. F. Dice. 1968. Distribution and cycling of nitrogen, phosphorus, potassium and

calcium in a second-growth Douglas-fir ecosystem. In Primary Productivity and Mineral Cycling in Natural Eco-

systems. Univ. of Maine, Orono. pp. 197-232.

Giddens, J., H. F. Perkins and R. L. Carter. 1960. Soils of Georgia. Soil Science 89(4) :229-238.

Hebb, E. A. 1981 . Choctawhatchee sand pine growth on a chemically prepared site--10 year results. So. J. of Applied

For.5(4):208-211.

Issac, R. A. and W.C.Johnson. 1976. Determination of total N in plant tissue. JAOAC 59(1):98-100.

Jackson, M. L. 1958. Soil chemical analysis. Prentice-Hall, Inc., Englewood Cliffs, pp. 219-220. Jorgensen, J. R., C. G. Wells, and L. J. Metz. 1975. The nutrient cycle: key to continuous forest production. J.

Forestry 73:400-403.

Peech, M. 1965. Hydrogen ion activity. In (C. A. Black, ed.) Methods of Soil Analysis, Part 2, Amer. Soc. Agron.,

Madison, Wis. pp. 914-925.

Perkin-Elmer. 1976. Analytical methods for atomic adsorption spectrophotometry. Perkin-Elmer Co., Norwalk,

Conn.

Pritchett, W. L. 1979. Properties and management of forest soils. John Wiley and Sons, New York. 500 p.

Pritchett, W. L. and N. B. Comerford. 1982. Long-term response to phosphorus fertilization on selected southeastern

Coastal Plain soils. Soil Sci. Soc. Am. J. 46:640-644.

Switzer, G. L. and L. E. Nelson. 1972. Nutrient accumulation and cycling in loblolly pine plantation ecosystems, the

first twenty years. Soil Sci. Soc. Amer. Proc. 36:143-147.

Technicon. 1975. Industrial methods no. 328-74A for technicon autoanalyzer II. Technicon industrial systems,

Tarrytown, NY.

Tuttle, C. L. 1978. Root biomass and nutrient content of a 25-year-old loblolly pine (Pinustaeda L.) plantation in

A&M east Texas. Unpublished Master's Thesis, Texas

University, College Station, Texas. 70p.

University of Georgia. 1983. Reference soil test methods for the southern region of the United States. Southern

Cooperative Series Bulletin 289. 40p.

Van Lear, D. H. 1980. Longleaf pine - Scrub oak. In Forest Cover Types of the United States and Canada (F. H.

Eyre, ed.). Society of Am. For., Washington, D. C, 148p. Van Lear, D. H., N. B. Gobel and J. G. Williams, Jr. 1977. Performance of unthinned loblolly and slash pine planta-

tions on three sites in South Carolina. So. J. of Applied For. 1 (7) :8-10. Warton, C. H. 1978. The natural environments of Georgia. Georgia Department of Natural Resources, Atlanta,

Georgia. 227p.

Woods, 1959. Converting scrub oak sandhills to pine forests in Florida. J. of For. 57:1 17-1 19.

11

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