Bulletin 588 October 1987 Alabama Agricultural Experiment Station Auburn University Lowell T. Frobish, Director Auburn University, Alabama

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CONTENTS
Page
INTRO DUCTION ...................................................................... M ETHODS ...................................................... ....................

3
4

RESULTS AND DISCUSSION .....................................................

7
7

Effects on Nonpine Vegetation ...................................

Effects on Loblolly Pine Seedlings .............................. 9 Effect of Soil Removal on Soil Chemical Properties ....... 11 ...................... 16 Surface Bulk Density .....................
SUMMARY AND CONCLUSIONS ................ 18

REFERENCES .......................

.....................

...................... 21

FIRST PRINTING 3M, OCTOBER 1987

Information contained herein is available to all persons without regard to race, color, sex, or national origin.

Effect of Soil Removal and Herbicide Treatment on Soil Properties and Early Loblolly Pine Growth
1 C.L. Tuttle, M.S. Golden, and R.S. Meldahl

INTRODUCTION

THE PAST few decades, forestry and the forest products industry have increased their economic importance in Alabama. This has involved intensifying forestry operations, including the use of large, heavy machinery for harvesting and site preparation. In the South, mechanical site preparation treatments are used primarily to facilitate planting operations and to reduce competition. However, mechanical treatments may severely impact a site (4, 19, 22). During harvesting and mechanical site preparation, the litter layer is commonly removed or destroyed and the surface soil may be compacted. With raking and piling, the surface soil layers may be severely disturbed or pushed into windrows (10, 21). This not only physically displaces soil, but bares the soil surface to potential damage from raindrop impact and possible accelerated erosion (5, 30). Many southern pine plantation establishment systems employ some form of mechanical site preparation, which may result in surface soil displacement. However, observation of site-prepared areas indicates that the degree of soil movement is highly variable. Factors such as the amount and nature of rooted vegetation, topography, the quantity and size of stumps and logging debris, soil texture, and soil moisture all affect the degree of soil movement. The major causes of surface soil
' Respectively, Research Associate, Associate Professor, and Assistant Professor of Forestry.

OVER

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ALABAMA AGRICULTURAL EXPERIMENT STATION

disturbance, however, are the size and design of the machinery used and the skill and care of the machine operator. Early studies of raking and piling (a popular site preparation system used during the 1950's, 1960's, and 1970's) showed that pine seedling growth and survival could be increased through intensive treatment. Survival increases of 15 to 38 percent were found on raked and piled areas in the Florida sandhills (11, 13), while a 33 percent increase in seedling height was found by McMinn in south Florida (20). Increases in survival and seedling height were partially attributed to competition reductions. Other research indicates that although early survival and growth may be improved by raking and piling, long-term site productivity may have been reduced. Glass (10) reported that a 25-year-old raked and piled loblolly pine plantation where 1 inch of soil was lost had a site index (base age 50) 8 to 10 feet lower than adjacent nonraked and piled plantations. Coile and Schumacher (3) found a 2-inch reduction in the surface soil depth could reduce loblolly pine 50-year site index 3 to 15 feet. It has generally been accepted that surface soil loss from forest or agricultural land will negatively impact site productivity. However, most investigations into soil losseffects have been conducted on agricultural land which frequently remains bare for long periods of time or on forest land in mountainous areas. Since some soil movement and exposure are inevitable with mechanical site preparation, an important issue is the relationship between the degree of soil movement and potential negative impacts on site productivity. This study was established to determine the effects of surface soil loss on soil properties and on loblolly pine seedling establishment by simulating the levels of soil loss normally occurring during intensive mechanical site preparation. METHODS Five sites were selected for study, two in the Piedmont and three in the Hilly Coastal Plain regions of Alabama (14). Sites 1 and 2 were Piedmont old field situations, with site 1 being on a gently sloping upper hillside and site 2 on a lower hillside. Soils on both sites were members of the Gwinnett sandy clay loam series (clayey, kaolinitic, thermic Typic Rhodudult) having a sandy clay loam Ap surface horizon 2 to 5 inches thick

EFFECT OF SOIL REMOVAL AND HERBICIDES ON SOIL AND PINES

5

over a clay subsoil 7 to 23 inches thick. Both Piedmont old field sites had been fertilized and limed during the mid-1970's while used as pasture, but no additions had been made in the 3 years prior to this study. Sites 3, 4, and 5 were in the Hilly Coastal Plain. Site 3 was used as deer range in wildlife research, but had not been fertilized in over 30 years, while site 4 was a recently cutover loblolly pine stand and site 5 was composed of log decks (loading areas) used during the harvest of site 4. Soils on all three Coastal Plain sites are in the Marvyn loamy sand series (fine-loamy, siliceous, thermic Typic Hapludult) with a loamy sand Ap surface horizon 4 to 8 inches thick over a sandy loam B1 horizon 7 to 15 inches thick. Slopes on all five sites were less than 5 percent. Since sites 1 and 2 were both Piedmont old fields on the same soil series located near each other, they were combined for analysis, resulting in six replications for this "previous use" class, while the other three areas each had three replications. Also, due to land area restrictions on the Piedmont old fields, one replication was installed without a control plot. Vegetation on the Piedmont old fields was composed primarily of Coastal bermudagrass (Cynnodon dactylon), asters (Asteraceae), and sedges (Cyperaceae), with scattered small sweetgum (Liquidambarstyraciflua L.), dogwood (CornusfloridaL.), sumac (Rhus copallina L. and Rhus glabra L.), and oaks (Quercus spp.). The Coastal Plain old field contained primarily these same species, along with blackberry (Rubus spp.) and privet (Ligustrum spp.). Vegetation on the cutover area included oaks, sweetgum, asters, sedges, smilax (Smilax hispida Muhl.), sassafras (Sassafras albium Nutt.), and loblolly pine. Three levels of surface soil removal were studied on each site: a control where no soil was removed, a 1-inch removal ("light"), and a 3-inch ("heavy") removal. Three replications, each containing a control and the two levels of soil removal, were installed in a randomized complete block design on each site. The two soil removal treatments were installed using a D-7 crawler tractor. Treatment areas were 40 feet X 75 feet, with 20-foot X 67-foot measurement plots. During the winter of 1981, the treatment areas were hand planted with 1-0 loblolly pine seedlings at a 6- X 8-foot spacing. After planting, the treatment areas were split and one-half of each treated with a tank mix of glyphosate (Roundup®), trichlopyr (Garlon®), and oxyflurfen (Goal®) during May of

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ALABAMA AGRICULTURAL EXPERIMENT STATION

the first season and glyphosate alone during May of the second year. Herbicide rates were 2.44 pounds glyphosate, 3.34 pounds trichlopyr, and 1.67 pounds oxyflurfen acid equivalent per acre. The pine seedlings were covered during herbicide applications. Surface bulk density and soil chemical levels were determined on each plot immediately after planting and at the end of each of the first three growing seasons. Surface soil bulk density was found by collecting five randomly placed 3-inch X 3-inch cylindrical cores from each plot. At each sampling time, three points were randomly selected where the upper 12 inches of soil was collected for chemical analysis in four consecutive 3-inch increments, using a specially designed soil sampling tube (28). The three chemical analysis points on each plot were composited by depth increment prior to soil analysis. Total nutrient concentration for the surface 12 inches was found by summing the incremental values. The depth increments compared are based on post-treatment soil conditions, since this is the rooting environment of planted seedlings. The soil samples were analyzed for extractable calcium (Ca), magnesium (Mg), potassium (K), and manganese (Mn) using 1.0 N ammonium acetate (pH 7.0) and atomic absorption spectrophotometry; extractable soil phosphorus (P) was determined using a dilute fluoric acid extracting solution (Bray #2) and the chlorostannous-reduced molybdophosphoric blue color method (16). Nitrogen determinations were by block digestion and colorimetric assay (15). Soil organic matter content was determined using the Walkley-Black procedure. Total seedling heights and survival were determined at the end of each of the first three growing seasons. Seedling ground line diameter (GLD) was taken after the second and third seasons. From GLD and total seedling height, stem volume for each seedling was calculated as an index of potential biomass. During July of the second season, nonpine vegetation was estimated as percent cover using a point intercept approach along three systematically placed lines on each plot. General linear models procedures (GLM) of SAS were used to perform analyses of variance since the study design was not balanced (8). When significant differences were observed (0.05 percent level), Duncan's New Multiple Range Tests were performed to compare the means.

EFFECT OF SOIL REMOVAL AND HERBICIDES ON SOIL AND PINES

7

RESULTS AND DISCUSSION Effects on Nonpine Vegetation Surface soil removal and herbicide treatments were both generally effective in reducing the quantity of nonpine vegetation. Soil removal alone did not reduce the levels of herbaceous cover, table 1. However, where the soil removal and herbicide treatments were used in combination, there were significant reductions of 30 percent and 36 percent in the levels of herbaceous cover for the light and the heavy removal treatments, respectively. This implies that the herbaceous reductions were due to herbicide applications and not the removal treatments, although average vegetation levels on the spray-only controls do not support this. The lack of herbaceous reduction on the spray-only is due primarily to an increase in the bermudagrass levels on the Piedmont old fields where herbaceous cover doubled during the first two seasons. The chemical rates used were not high enough to kill bermudagrass, and in fact released it. Removing the Piedmont old fields from the analysis results in an average herbaceous cover on the spray-only controls of 18 percent, supporting the theory that most of the herbaceous reductions were due to the herbicide applications. Woody stems (most commonly sumac, sweetgum, dogwood, and oaks) were greatly reduced by the soil removal treatments. Woody cover ranged from 21 percent to 11 percent to 9 percent for the control, light, and heavy removal treatments respectively, table 1. During soil removal, roots, stems, stumps,
TABLE 1. EFFECT OF SOIL REMOVAL AND SPRAY TREATMENTS
SEASONS

ON

COMPETING

VEGETATION AFTER TWO GROWING

Spray and soil removal treatment

Competition, percent of total cover Grasses and forbs Vines Woody vegetation Total' competition
Coastal Plaint

competition

Nonspray Control ................. 42.6 A3 29.0 A 21.4 A 93.1 A 91.4 A 1-inch removal ...... 46.0 A 18.2 AB 10.6 B 74.8 B 76.8 AB 3-inch removal ...... 39.1 A 17.4 AB 9.0 B 65.6 BC 64.4 B SPoray control ................. 39.9 A 7.9 AB 6.6 BC 54.4 C 32.2 C 1-inch removal ...... 12.8 B 2.9 C 2.4 C 18.1 D 12.0 D 3-inch removal ...... 6.1 B 3.8 C .9 C 10.9 D 12.0 D 'All sites. 2 Coastal Plain sites only. 'Means with the same letter are not significantly different at the 0.05 level.

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ALABAMA AGRICULTURAL EXPERIMENT STATION

and seeds were physically removed from the study areas similar to removal which occurs during raking and piling operations. When herbicides were used in combination with soil removal, most of the woody vegetation was eliminated from the treated areas. Total nonpine cover was reduced from 93 percent to below 75 percent by the soil removal treatments alone, table 1. However, they were most effective when applied in combination. Nonpine competition levels were directly related to the intensity of the soil removal/spray treatment combination. Total cover decreased as soil removal/spray treatment intensity increased. The nonspray control had the highest degree of vegetation cover. The light soil removal alone significantly
TABLE 2. EFFECTS OF SOIL REMOVAL AND HERBICIDE SPRAY TREATMENTS ON COMPETING VEGETATION AFTER TWO SEASONS, BY PREVIOUS LAND USE

Competition, percent of total cover Spray treatment Soil removal | treatment treatment' Grasses and forbs Vines Woody vegetation 19.6 11.1 12.7 10.2 1.0 1.2 A AB AB AB B B Total competition 96.3 A 71.9 B 67.3 B 94.1 A 27.1 C C 9.2 99.9 A 88.8 AB 64.2 B 66.1 B 22.9 C 19.6 C 87.7 A 54.4 B 53.1 B 19.6 C 7.8 C 5.2 C

Piedmont old field 47.4 B2 Control Nonspray 38.9 B 1-inch removal Nonspray 40.4 B 3-inch removal Nonspray 80.4 A Control Spray 22.9 BC 1-inch removal Spray 3.3 C 3-inch removal Spray Coastal Plain old field 8.6 B Control Nonspray 33.3 AB 1-inch removal Nonspray 20.4 AB 3-inch removal Nonspray 41.8 A Control Spray 15.0 AB 1-inch removal Spray 10.5 B 3-inch removal Spray Coastal Plain cutover 40.1 AB Control Nonspray 42.6 A 1-inch removal Nonspray 21.4 AB 3-inch removal Nonspray 2.6 A Control Spray 1.3 B 1-inch removal Spray 3.9 AB 3-inch removal Spray Coastal Plain log deck 71.6 A Nonspray Control 76.5 A 1-inch removal Nonspray 72.8 A 3-inch removal Nonspray 7.9 B Control Spray 2.0 B 1-inch removal Spray 9.8 B 3-inch removal Spray 'n=3 for all treatments on the Coastal Plain controls, and n=6 for the Piedmont old field 2 Means within a use with the same letter are level.

29.3 A 21.9 A 14.2 AB 3.5 B 3.3 B 4.3 B 61.7 40.7 34.0 22.9 7.2 9.1 24.7 3.7 24.7 6.6 .0 .0 A AB AB AB B B A A A A A A

29.6 A 14.8 B 9.9 B 1.3 B .7 B .0 B 22.8 A 8.0 B 6.8 B 10.5 AB 6.5 B 1.3 B

14.8 A 86.4 A .0 A 87.1 A 8.1 AB 2.5 A 75.9 A 3.1 B .0 A 11.1 B 2.0 B 1.3 A 5.3 B .7 A 2.6 B 11.1 B .0 B 1.3 A sites, n=5 for the Piedmont old field removal treatments. not significantly different at the 0.05

EFFECT OF SOIL REMOVAL AND HERBICIDES ON SOIL AND PINES

9

reduced competing vegetation (20 percent), while the heavy removal resulted in a 28 percent reduction. However, use of soil removal and herbicides in combination resulted in an additional 40 percent and 60 percent reduction (over soil removal alone) in nonpine cover. Vegetation patterns were found to be similar for all four previous land uses, table 2. Nonsprayed controls had the highest nonpine competition level, while the sprayed removal treatments had the lowest. The Piedmont and Coastal Plain old fields had higher competition levels than did the Coastal Plain cutover and log deck sites. Soil removal also significantly reduced the level of competing vegetation with the amount of total nonpine reduction similar on all sites. Total cover reductions of up to 35 percent occurred due to soil removal alone and averaged 17 percent on the light and 28 percent on the heavy removals, table 2. In addition, total competition decreased on each site as the level of soil removal increased. Increasing the depth of soil removal removed more of the roots and seeds which could sprout. This was particularly evident by the reduction in woody vegetation on the scraped areas.

Effects on Loblolly Pine Seedlings
The soil removal treatment/site interaction was nonsignificant for pine seedling survival or growth after three growing seasons. Therefore, all five study sites were pooled for the seedling analyses. Soil removal increased seedling survival after three seasons, table 3. Survival was increased 17 percent and 27 percent by
TABLE 3. EFFECT OF SOIL REMOVAL AND SPRAY TREATMENTS ON TOTAL SEEDLING HEIGHT, SURVIVAL, AND VOLUME AFTER THE THIRD GROWING SEASON

Spray and soil removal treatment

Mean ~ln
seedling

Seedlin seedlingln Ground survival diameter

Mean seling oue
volume/

Pct. In. Cu. Ft. Nonspray 1.02 C 148 D 54 C 58.3 B Control .................................... 203 CD 75.0 AB 1.26 BC 55 BC 1-inch removal ........................ CD 1.27 BC 228 56 BC 85.0 A 3-inch removal ........................ Spray 332 BC 58.3 B 1.52 AB ...................... 63 ABC Control 75.6 AB 1.65 A 491 A 1-inch removal................71 A 1.61 A 448 A 65 AB 77.8 AB 3-inch removal ........................ 'Means with the same letter are not significantly different at the 0.05 level.

heightaacre In.

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ALABAMA AGRICULTURAL EXPERIMENT STATION

the light and heavy removals, respectively, similar to survival increases previously reported where intensive mechanical site preparation had been used. Stafford et al. (23) reported loblolly pine survival increases of 18 percent following raking and piling at three Piedmont sites. Grelen (11) similarly reported a 20 percent increase in slash pine (Pinus elliottii Engelm.) survival following intensive site preparation in the Florida sandhills. Herbicide use had no effect on loblolly pine seedling survival after three seasons. A direct relationship was found between the soil removal treatment and seedling height, ground line diameter (GLD), and volume after three seasons, table 3. In general, as treatment intensity increased, seedling growth also increased. Soil removal alone significantly increased mean seedling volume 38 percent and 55 percent for the light and heavy removal treatments, respectively. However, when herbicides were used in conjunction with soil removal, seedling height and volume were affected the most. Volume increases exceeding 200 percent occurred on the removal areas when compared to nonsprayed controls. Mean seedling height and GLD were also increased but to a lesser degree. Three-year-old loblolly pine height and volume were found to be negatively correlated with the nonpine vegetation cover, table 4. Generally, as nonpine vegetation increased, seedling growth decreased, a previously reported relationship (1, 2, 17). Past research has reported that reducing competing vegetation drastically influences the quantity of water available to tree seedlings. Water depletion rates have been reported to be much higher on areas with heavy competition (7, 24, 29, 31). The reduction in competition resulting from soil removal
TABLE 4. CORRELATIONS OF LOBLOLLY PINE SEEDLING HEIGHT AND VOLUME AFTER THREE GROWING SEASONS, WITH THE PERCENT COVER OF VARIOUS NONPINE COMPETITION CLASSES AFTER TWO SEASONS

Correlation with competition

Grasses and forbs Seedling height .................... -0.2605 * Average seedling volume .....- 0.2611 * Total seedling volume ......... -0.2402 * * Significant at the 0.05 level. ** Significant at the 0.01 level.

Pine measurement

Vines Vines 0.1651 -0.0911 -0.0519

Woody vegetation 0.0825 -0.1679 -0.1696

Total competition -0.0952 -0.3043 ** -0.2670 *

EFFECT OF SOIL REMOVAL AND HERBICIDES ON SOIL AND PINES

11

and herbicide treatment leads to the inference that the moisture available to the planted seedlings was increased. Increases in young seedling growth and survival have been found on other areas where severe soil disturbance has occurred. On a sandhills site in northwest Florida (11), slash pine seedlings on raked and piled areas (much of the topsoil in windrows) were taller and had higher survival after two seasons than those on control plots. Lantagne and Burger (18) reported that intensive site preparation on sandy loam soils resulted in better survival and growth of loblolly pine after one season.

Effect of Soil Removal on Soil Chemical Properties
Herbicide use had no effect on soil chemical properties in the upper 12 inches of soil or on surface bulk density after three seasons, table 5. At no time during the 3 years of study did herbicide application significantly alter soil properties. Therefore, the split plots were pooled for all soil analyses. Soil removal significantly reduced concentrations of organic matter and all nutrients except Mg in the upper 12 inches after three seasons, table 6. Although there was no difference between the light and heavy removal treatments, as more soil was removed, nutrient levels tended to decrease; most of this decrease occurred during the removal of the surface inch. Surface soil removed during treatment was high in organic matter. The light removal treatment reduced the organic
TABLE 5. EFFECT OF HERBICIDE TREATMENT ON SOIL CHEMICAL PROPERTIES IN THE UPPER 12 INCHES OF SOIL AND SURFACE BULK DENSITY AT THE END OF THE THIRD GROWING SEASON

Soil and spray treatpmenty Ca

Soil nutrients/acre Mg K Mn P N Lb.

Soil Soil organic bulk matter density Pct. g/cc

Lb. Lb. Lb. Lb. Lb. No soil removal (control) 1,030A' Nonspray ............. 235A 159A 70A 13A 1,020A 228A 152A 59A 14A Spray ................... 1-inch removal 230A 127A 52A 10A Nonspray ............ 882A 224A 127A 48A 11A Spray ................. 900A 3-inch removal 9A 200A 127A 41A 773A Nonspray ............ 8A 868A 205A 135A 50JA Spray ..................... 'Means within a treatment with the same letter are not the 0.05 level.

2,179A 1.54A 1.13A 2,124A 1.55A 1.16A 1,428A 1,464A .97A 1.24A .90A 1.31A

1,199A .80A 1.32A 1,149A .63A 1.34A significantly different at

[ABLE 6.

CHANGE

IN SOIL NUTRIENTS

AND ORGANIC

MATTER IN THE UPPER REMOVAL TREATMENT

12 INCHES OF SOIL THROLGH

LIME FOR EACH SOIL

Soil removal treatment and time of treatment

Ca

Mg Lb. 241 228 221 232 A A A A

Soil nutrients/acre K Mn Lb. 163 158 158 156 A A A A Lb. 42 C 46 BC 53 AB 61 A 37 C 40 C 45 B 50 A

P Lb. 12 C 12 C 15 A 13 B 9 A 8 B 10 A 10 A

N Lb. 2,048 AB 1,834 B 1,984 AB 2,152 A 1,692 A 1,349 B 1,226 C 1,446 B 1,284 A 1,145 B 980 C 1,174 AB

Lb. No soil removal (control) At planting ............... 919 BC' After 1 season 876 C After 2 seasons ......... 963 B After 3 seasons ......... 1,025 A 1-inch removal At planting............. 812 B Afteri1season ..... 900 A After 2 seasons..... 913 A After 3 seasons..... 891 A 3-inch removal At planting............. 774 B After 1 season ..... 745 B After 2seasons..... 802 AB After 3 seasons..... 821 A 'Means within a treatment with the same 2
Control n=14; 1-inch removal

organic matter Pct. 1.26 B 1.16 1 1.16 B 1.55 A C) .93 A .77 B .80 B .93 A .71 A .64 AB .60 B .72 A
c

261 A 240 B 219 B 227 B

154 A' 154 A 136 B 127 B

n-15; 3-inch removal

237 A 137 A 34 C 8A 232 A 137 A 37 BC 8 A 205 B 136 A 40 B 9A 203 B 131 A 45 A 9 A letter are not significantly different at the 0.05 level.
n=15.

m

x

mU

m

z
-a

0

z

EFFECT OF SOIL REMOVAL AND HERBICIDES ON SOIL AND PINES

13

content 26 percent at planting when compared to the controls and the heavy removal reduced it by 44 percent, table 6. These reductions were 40 percent and 54 percent for the light and heavy removals, respectively, after three seasons. Although not significantly different from the light removal, the heavy removal treatment had the lowest nutrient concentrations after 3 years. Removing 1 inch of soil reduced nitrogen (N) concentration 33 percent. An additional 2-inch soil removal (total of 3 inches of soil removed) reduced N an additional 273 pounds per acre, a total reduction of 45 percent. Similarly, after 3 years, P was reduced 27 percent and 33 percent and Ca 13 percent and 20 percent for the light and heavy soil removal treatments, respectively. Potassium and Mn also were significantly reduced by soil removal, but to lesser degrees than N, Ca, or P. Therefore, where the surface soil layers were removed, nutrients needed by the planted seedlings were also reduced. Examination of the nutrient concentrations through the first three seasons shows three separate patterns of change occurring, table 6. Calcium and Mn both increased through the study on the removal treatments. Their increases are thought to be associated with release from feldspars and other minerals, abundant on the study areas. These minerals were exposed during treatment application, resulting in more rapid weathering that released Ca and Mn. Nitrogen, however, dropped during the first 2 years on both removal treatments and then increased during the third. Since in forest situations most soil N is associated with organic material, the early N losses are related to organic residue decomposition and subsequent N loss due to volatilization or leaching. By the third season, developing vegetation increased soil organic matter and consequently soil N. The decrease in soil organic matter has several other detrimental effects on forest sites. Besides the loss of nutrients through decomposition, a reduction in soil organic matter may reduce soil structure and water holding capacity. This reduces the water available to young seedlings and therefore may reduce early growth. On any sandy site, a significant organic matter reduction may substantially reduce soil cation exchange capacity (CEC). Organic matter in the surface layers supplies a large portion

TABLE 7. EFFECT OF SOIL REMOVAL ON SOIL NUTRIENT CONCENTRATIONS AND ORGANIC AND AFTER 3 SEASONS o

MATTER FOR EACH DEPTH AT PLANTING

depth' At planting 1

ireoval treatment

Ca Lb.

Mg Lb.

Soil nutrients/aCreoi K Mn Lb. Lb.

Soi P Lb. N Lb. 860A 680 B 390 C 481A 386 B 333 B 367A 330A 287 B 340A 297AB 273 B 819A 423 B 323 B 566 A 386 B 292. B 408 A 325 B 284 B 360 A 313 AB 275 B level. organi Pct. 1.97A 1.36 B 1.07 C 1.33A 1.07 A .71 B .96A .68 B .55 B .76A .60 B .50 B 2.08A 1.10 B .84 B 1.63 A 1.05 B .79 B 1.33 A .85 B .64 B
1.i5A

Control 308 A2 71 AB 46 A 14A 4A 1-inch removal 232 B 75 A 44 A 12 B 3 B 3-inch removal 213 B 57 B 27 B 10 C 3 B Control 222 A 61 A 40 A 11 A3A 2 1-inch removal 203 AB 62 A 39 A 10 A 3 A 3-inch removal 178 B 65 A 35 A 10A 3A Control 192 A 56 B 37 A 10 A 3A 38 A 8 AB 2 B 187 A 64 A 3 1-inch removal 3-inch removal 178 A 57 AB 35 A 7 B 2 B Control 198A 53A 39A 8A 3A 4 1-inch removal 190 A 60 A 33 A 8A 1 B 3-inch removal 175 A 58 A 34 A 7A 2AB After 3 seasons Control 322 A 69 A 44 A 18 A 4A 1 1-inch removal 208 B 49 B 29 B 14 B 4A 3-inch removal 173 B 40 B 29 B 12 B 3 B 4A 16 A 39 A 59 A 254 A Control 2 1-inch removal 207 B 52 AB 29 B 12 B 3 B 2 B 12 B 30 B 38 B 186 B 3-inch removal Control 230 A 53 A 36 A 14 A 3A 3 1-inch removal 238 A 61 A 34 A 12AB 3 B 3-inch removal 219 A 61 A 36 A 11 B 2 B 3A 12 A 36 A 52 B 218 A Control 3 AB 12 A 36 A 67 A 238 A 1-inch removal 4 3-inch removal 242 A 63 A 36 A 11A 2 B 'Soil depths: 1= 0 to 3 inches, 2 = 3 to 6 inches, 3 = 6 to 9 inches, and 4 = 9 to 12 inches. 2 Means within a soil depth/time category with the same letter are not significantly different at the 0.05

>

)

c

>
C

m

M !

x

z
0 Z

.73 .62

B B

co

EFFECT OF SOIL REMOVAL AND HERBICIDES ON SOIL AND PINES

15

of the CEC sites (12). Reducing the organic matter level 26 percent on the light removal and 44 percent on the heavy removal treatment (1.26 percent to 0.93 percent to 0.71 percent) undoubtedly resulted in a CEC reduction, since 25 to 40 percent of the CEC sites are normally organic in nature. With the low CEC levels throughout much of the South (less than 10 milliequivalents per 100 grams of soil), the loss of organic exchange sites is important. By reducing soil CEC, the soil's ability to retain mobile nutrients is also reduced, thus leaching may result. Magnesium and K both show steady decreases where soil removal has occurred, probably due to leaching. The loss of mobile nutrients is further supported by examination of the incremental samples. At planting, the highest Ca, Mg, and K levels on the controls and both removal treatments occurred in the surface soil layer and the concentrations decreased as depth increased, table 7. In contrast, after three seasons, the pattern had reversed on both the removal treatments; the highest Ca, Mg, and K levels were found in the lower soil layers, while the surface layer concentrations had decreased. The reduction in nutrient concentrations in the surface layers would be reduced in part due to vegetation absorption. However, the large increases (over the initial concentrations) at the lower depths, which occurred only on the removal plots, are most readily attributable to leaching. The areas where the surface soil was removed had less vegetation, thus reducing the cycling of nutrients through vegetation and possibly increasing soil water percolation through reduced transpiration and interception loss. The control plots showed little downward movement of the mobile nutrients. After three seasons, all land uses showed the control areas had higher nutrient concentrations than the removal treatments, table 8. On the old fields and the cutover sites, Ca, Mg, and N concentrations were significantly reduced by soil removal. The nutrients were removed primarily during soil removal treatment, and in the cases of the mobile nutrients, additional losses occurred due to leaching. The log deck areas showed little change in nutrient concentration. Apparently this is due to the severe disturbance occurring during their use as decks. The soil was "churned" by skidders and loaders, mixing the surface layers. High variation in nutrient concentration occurred between

16

ALABAMA AGRICULTURAL EXPERIMENT STATION

TABLE 8. EFFECT OF SOIL REMOVAL ON SOIL NUTRIENT CONCENTRATIONS AND ORGANIC MATTER IN THE UPPER 12 INCHES OF SOIL AT THE END OF THE THIRD GROWING SEASON, BY PREVIOUS LAND USE

Soil removal treatment

Soil Ca Lb. Mg Lb. 513 A 485 AB 431 B 154 A 83 B 86 B 40 A 31 B 31 B Soil nutrients/acre K Mn Lb. Lb. 216 A 176 A 185 A 200 A 167 A 157 A 92 A 60 B 57 B A A A letter 106A 81 B 75 B 63 A 52A 45A 19A 15A 13A
orga

P Lb.

N Lb.

matter Pct.

Piedmont old field Control .............. 1,790 A' 1-inch removal ..1,673 AB 3-inch removal .. 1,463 B Coastal Plain old field Control ........... 1,248 A 1-inch removal .. 668 B 3-inch removal .. 797 B Coastal Plain cutover Control ........... 331 A 1-inch removal .. 202 B 3-inch removal'.. 167 B Coastal Plain log deck Control ........... 220 A 1-inch removal .. 219 A 3-inch removal .. 216 A 'Means within a land use 0.05 level.

5A 3,056A 1.85A 3 AB 1,856 B 1.25 AB 2 B 1,380 B .89 B 29 A 24A 25A 11 A 8 A 6A 1.58 A 2,454 A 1,357 B .87 B 1,147 B .60 B 1,348A 1.40A 1,010 B .59 B 821 B .50 B

74 31 B 51 A 60 35 B 69 with the same

23A 14A 1,145A 1.17A 22A 12A 1,149A .70A 19 A 8 A 1,141 A .72 A are not significantly different at the

former uses, table 6. The old fields were found to have higher nutrient concentrations than the other areas. On these sites, even the most intensive removal treatment had higher concentrations than the controls on the cutover and log deck sites. Because of high variation within a use, however, no significant differences among sites could be ascertained. Examination of the former forest land uses shows that the controls on the cutover sites have nutrient concentrations similar to those reported in other southern pine plantations. Loblolly pine plantations on an east Texas sandy site had 273 pounds Ca, 18 pounds P, and 1,357 pounds N per acre in the surface 12 inches (27). Similarly, Switzer et al. (26) found N levels of 1,742 pounds per acre in the surface 6 inches on a Mississippi clay loam soil. After three seasons, soil removal resulted in nutrient concentrations below these reported levels. Surface Bulk Density Soil removal significantly increased soil bulk density, table 9. The D-7 tractor used in soil removal compacted the treatment areas, increasing bulk density. This is similar to bulk

EFFECT OF SOIL REMOVAL AND HERBICIDES ON SOIL AND PINES

17

TABLE 9. TREATMENT EFFECTS ON SURFACE SOIL BULK DENSITY AT EACH SAMPLING

TIME ACROSS ALL SITES

Soil removal treatment At planting Control ................................ 1-inch removal ..................... 3-inch removal ..................... After 1 season Control ................................. 1-inch removal ..................... 3-inch removal ..................... After 2 seasons Control ........................... 1-inch removal .................... 3-inch removal ..................... After 3 seasons Control .............................. 1-inch removal ..................... 3-inch removal ..................... 'Means within a time with the same 0.05 level.

Soil nbulk density

g/cc

14 15 15 14 15 15 14 15 15

1.46 C' 1.56 B 1.63 A 1.31 C 1.48 B 1.55 A 1.21 C 1.31 B 1.41 A

14 1.14 C 15 1.27 B 15 1.33 A letter are not significantly different at the

density increases commonly occurring during site preparation (9, 25). After three seasons, bulk densities on the light and the heavy removal treatments were still significantly higher than the controls, although the values had significantly decreased. During the first three growing seasons, the relative drop in bulk density was not affected by soil removal treatment. Bulk density reductions from the initial measurements to the end of the third season are similar (near 0.30 gram per cubic centimeter) for the control and both removal treatments. Vegetal root growth is thought to be the primary cause of the bulk density reductions. Previous land use exhibited little effect on soil bulk density patterns, but did affect the degree of change, table 10. Both the old fields and the cutover forest site were significantly compacted during soil removal. However, soil removal on the log decks caused only slight bulk density increases. The former log decks, which were heavily compacted during harvesting, had the least increases (1.61 grams per cubic centimeter to 1.72 grams per cubic centimeter), while the Piedmont old fields (lowest initial bulk density) showed the largest increases. Previous land use had no effect on the recovery rate as all areas showed similar recovery patterns.

18
TABLE

ALABAMA AGRICULTURAL EXPERIMENT STATION
10. EFFECT OF SOIL REMOVAL TREATMENT ON BULK DENSITY BY EACH PREVIOUS LAND USE AT PLANTING AND AT THE END OF THIRD GROWING SEASON

Time Piedmont old field At planting

Soil removal treatment Control 1-inch removal 3-inch removal Control 1-inch removal 3-inch removal Control 1-inch removal 3-inch removal Control 1-inch removal 3-inch removal Control 1-inch removal 3-inch removal Control 1-inch removal 3-inch removal

n

Soil bulk density
/ g cc

After 3 seasons Coastal Plain old field At planting After 3 seasons Coastal Plain cutover At planting

1.36 B 1 1.46 AB 1.57 A .99 B 1.18 A 1.24 A 1.48 1.63 1.68 1.19 1.31 1.42 1.47 1.59 1.62 1.19 1.36 1.40 B A A B AB A A A A B A A

After 3 seasons Coastal Plain log deck

1.61 A Control 1-inch removal 1.67 A 3-inch removal 1.72 A Control 1.30 A After 3 seasons 1-inch removal 1.30 A 3-inch removal 1.35 A 'Means within a land use and time with the same letter are not significantly different at the 0.05 level. At planting

Bulk density on the control plots also significantly decreased through time. The controls on the cutover and log deck sites were compacted during harvesting, while the old fields were compacted by grazing animals. These compaction causes have been well documented (6, 22). As with the removal treatments, bulk density decreases were largely due to vegetative root growth loosening the soil. SUMMARY AND CONCLUSIONS Surface soil removal and herbicide treatment resulted in significant loblolly pine seedling survival and growth increases after three seasons. The intensive treatments reduced nonpine vegetation, thereby increasing moisture available to the young

EFFECT OF SOIL REMOVAL AND HERBICIDES ON SOIL AND PINES

19

seedling. Pine growth increases following both woody and herbaceous competition reductions have been previously documented (2, 17). After three seasons, significant reductions in Ca, K, Mn, P, N, and organic matter concentrations occurred where topsoil was removed. In addition, Ca, Mg, and K appeared to be moving through the upper soil profile during the study period. Nitrogen levels of southern forested areas have been reported to range between 1,750 and 2,500 pounds per acre in forest stands on flatwoods soils (Arenic Paleudults and Ultic Haploquads) and various clay loam soils, respectively (21, 26). The N concentration on the control plots falls within this range, but the concentrations on the soil removal treatments are both below these reported values. Soil bulk density increased due to the removal of surface soil. Use of a D-7 crawler to scalp 1 inch or 3 inches of soil compacted the remaining soil and reduced soil organic matter (reducing soil structure). By the end of the third growing season, bulk densities had decreased relatively consistently on all treatments. During the 1950's, scalping 1 to 3 inches of surface soil was used to reduce competition, resulting in increased early survival and growth. The possible long-term problems that scalping could create were largely ignored. This study supports these older findings, i.e., competition reduction does increase seedling growth. Although severe site damage occurs during scalping, this damage has little effect on loblolly seedling growth during the first three seasons when soil moisture is the limiting growth factor. However, when the soil nutrient and organic matter changes are considered, it is quite likely that the early seedling growth gains on scalped areas will be temporary, particularly where heavy removal occurs. The significant nutrient and organic matter reductions (to levels below those typically found on southern forest sites) imply a reduction in total site productivity. This reduction may become evident later in the rotation (25-40 years), when vegetal site occupation reaches a point where nutrient supplies become limiting to tree growth. An implication of the soil, competition, and tree growth data taken together is that interpretation of the important effects of site manipulation on forest growth may be misleading

20

ALABAMA AGRICULTURAL EXPERIMENT STATION

if based solely on early seedling responses. Changes in the basic resource, the soil, indicate that long-term results may be the reverse of the short-term ones. Intensive vegetation management procedures are a necessary part of southern forestry, particularly during regeneration. However, the use of intensive mechanical treatments may severely damage a forest site, resulting in surface soil loss. Therefore, on many sites consideration must be given to utilizing either a less intensive mechanical treatment (e.g. chopping) or the use of chemicals along with burning to reduce competing vegetation. The quantity of soil lost from forest areas must be reduced to insure long-term site productivity.

EFFECT OF SOIL REMOVAL AND HERBICIDES ON SOIL AND PINES

21

REFERENCES (1)
CAIN, M.D. AND W.F. MANN. Early Growth of Planted Loblolly Pine

Increased with Annual Brush Control. So. J. Appl. For. 4:67-70. (2) CLASON, T.R. 1978. Removal of Hardwood Vegetation Increases Growth and Yield of a Young Loblolly Pine Stand. So. J. Appl. For. 2:96-97. (3) COILE, T.S. AND F.X. SCHUMACHER. 1953. Relation of Soil Properties to Site Index of Loblolly and Shortleaf Pines in the Piedmont Region of the Carolinas, Georgia, and Alabama. J. For. 51:739-744. (4) DICKERSON, B.P. 1972. Logging Disturbance on Erosive Sites in Northern Mississippi. U.S.F.S. Res. Note SO-72. (5) DISSMEYER, G.E. AND G.R. FOSTER. 1980. A Guide for Predicting Sheet and Rill Erosion on Forest Land. U.S.F.S. State and Priv. For. Tech. Pub. SA-TP 11.

(6)

FEDERER, C.A., G.H. TENPAS, D.R. SCHMIDT, AND C.B. TANNER.

(7)
(8)

1961. Pasture and Soil Compaction by Animal Traffic. Agron. J. 53:53-54. FERGUSON, E.R. 1956. Causes of First-year Mortality of Planted Loblolly Pines in East Texas. Pages 89-92 in Proc. 1956 Soc. Am. For.
FREUND, R.J. AND R.C. LITTELL. 1982. SAS for Linear Models. A

Guide to the ANOVA and GLM Procedures. SAS Institute, Inc., Cary, N.C. (9) GENT, J.A., JR., R. BALLARD, AND A.E. HASSAN. 1983. The Impact of Harvesting and Site Preparation on the Physical Properties of Lower Coastal Plain Forest Soils. Soil Sci. Soc. Am. J. 47:595-598. (10) GLASS, G.G., JR. 1976. The Effects from Rootraking on an Upland Piedmont Loblolly Pine (Pinus taeda L.) Site. Tech. Rep. No. 56. School of For. Resour., N.C. State Univ., Raleigh. (11) GRELEN, H.E. 1959. Mechanical Preparation of Pine Planting Sites in Florida Sandhills. Weeds 7:184-188. (12) HARTER, R.D. 1977. Reactions of Minerals with Organic Compounds in the Soil. Pages 709-740 in J.B. Dixon and S.B. Weed (eds.). Minerals in Soil Environments. Soil Sci. Soc. Am., Inc., Madison, Wis. (13) HEBB, E.A. 1957. Regeneration in the Sandhills. J. For. 53:210-212.

(14)

HODGKINS, E.J., M.S. GOLDEN, AND W.F. MILLER. 1979. Forest Hab-

itat Regions and Types on a Photomorphic-physiographic Basis: A Guide to Forest Site Classification in Alabama-Mississippi. South. Coop. Series Bull. No. 210. Ala. Agr. Exp. Sta., Auburn Univer., Ala.

(15) (16)

ISAAC, R.A. AND W.C. JOHNSON. 1976. Determination of Total Ni-

trogen in Plant Tissue Using a Block Digestor. JOAC 59:98-100. M.L. 1958. Soil Chemical Analysis. Prentice-Hall, Inc., Englewood Cliffs, N.J. (17) KNOWE, S.A., L.R. NELSON, AND D.H. GJERSTAD. 1982. Third Year Growth Response of Loblolly Pine to Herbaceous Weed Control. Page 159 in Proc. Southern Weed Science Society, 35th Annual Meeting. New Perspectives in Weed Science. Atlanta, Ga.
JACKSON,

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ALABAMA

AGRICULTURAL

EXPERIMENT

STATION

(18)

LANTAGNE, D.O. AND J.A. BURGER. 1983. First-year Survival and Growth of Loblolly Pine (Pinus taeda L.) As Effected by Site Preparation on the South Carolina and Georgia Piedmont. Pages 5-10 in E.P. Jones (ed.). Proc. Second Biennial So. Silvicultural Res. Conf. U.S.F.S. Gen. Tech. Rep. SE-24. (19) MCCLURKIN, D.C. AND D.M. MOEHRING. 1978. Consequences of Site Disturbance in the Upper Coastal Plain. Pages 73-84 in T. Tippin (ed.). Proc.: A Symposium on Principles of Maintaining Productivity on a Prepared Site. U.S.F.S., New Orleans. (20) MCMINN, J.W. 1969. Preparing Sites for Pine Plantings in South Florida. U.S.F.S. Res. Note SE-117.

(21)

MORRIS, L.A., W.L. PRITCHEETT, AND B.F. SWINDEL. 1983. Displace-

ment of Nutrients into Windrows During Site Preparation of a Flatwood Forest. Soil Sci. Soc. Am. J. 47:591-594. (22) SHOULDERS, E. AND T.A. TERRY. 1978. Dealing with Site Disturbances from Harvesting and Site Preparation in the' Lower Coastal Plain. Pages 95-97 in T. Tippin (ed.). Proc.: A Symposium on Principles of Maintaining Productivity on a Prepared Site. U.S.F.S., New Orleans. (23) STAFFORD, C.W., J.L. TORBERT, AND J.A. BURGER. 1985. An Evaluation of Site Preparation Methods for Loblolly Pine Regeneration on the Piedmont. Pages 57-60 in E. Shoulders (ed.). Proc. Third Biennial So. Silvicultural Res. Conf. U.S.F.S Gen. Tech Rep. SO-54. (24) STRANSKY, J.J. 1961. Weed Control, Soil Moisture, and Loblolly Pine Seedling Behavior. J. For. 59:282-290. (25) STRANSKY, J.J. 1981. Site Preparation Effects on Soil Bulk Density and Pine Seedling Growth. So. J. Appl. F. 5:176-180.

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SWITZER, G.L., L.E. NELSON, AND W.H. SMITH. 1968. The Mineral

Cycle in Forest Stands. Pages 1-9 in G.W. Bengston (ed.). Forest Fertilization-Theory and Practice. TVA, Muscle Shoals, Ala. TUTTLE, C.L. 1978. Root Biomass and Nutrient Content of a 25year-old Loblolly Pine (Pinus taeda L.) Plantation in East Texas. Unpublished MS thesis. Texas A&M Univ., College Station.
M.S. GOLDEN, AND D.L. SIROIS. 1984. A Portable Tool for Obtaining Soil Cores in Clayey or Rocky Soils. Soil Sci. Soc. TUTTLE, C.L.,

Am. J. 48:1453-1455.

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WILLISTON, H.L. 1978. The Case for Understory Hardwood Control to Improve Soil Moisture Availability. Soil Sci. Soc. Am. Proc. 33:131-

136.
WISCHMEIER, W.H. AND D.D. SMITH. 1978. Predicting Rainfall Erosion Losses-A Guide to Conservation Planning. USDA Agri. Hand-

book 537. (31) ZAHNER, R. 1958. Hardwood Understory Depletes Soil Water in Pine
Stands. For. Sci. 4:178-184.

Alabama's Agricultural Experiment Station System AUBURN UNIVERSITY

With an agricultural research unit in every major soil area,
v

2

Auburn University serves the needs of field crop, livestock, forestry, and horticultural producers in each region in Alabama. Every citizen of the State has a stake in this research program, since any advantage from new and more economical ways of producing and handling farm products directly benefits the consuming public.

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0
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Research Unit Identification

® Main Agricultural Experiment Station, Auburn.
SE. V. Smith Research Center, Shorter.
Tennessee Valley Substation, Belle Mina. Sand Mountain Substation, Crossville. North Alabama Horticulture Substation, Cullman. Upper Coastal Plain Substation, Winfield. Forestry Unit, Fayette County. Chilton Area Horticulture Substation, Clanton. Forestry Unit, Coosa County. Piedmont Substation, Camp Hill. Plant Breeding Unit, Tallassee. Forestry Unit, Autauga County. Prattville Experiment Field, Prattville. Black Belt Substation, Marion Junction. The Turnipseed-Ikenberry Place, Union Springs. Lower Coastal Plain Substation, Camden. Forestry Unit, Barbour County. Monroeville Experiment Field, Monroeville. Wiregrass Substation, Headland. Brewton Experiment Field, Brewton. Solon Dixon Forestry Education Center, Covington and Escambia counties. 20. Ornamental Horticulture Substation, Spring Hill. 21. Gulf Coast Substation, Fairhope. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.