United States 

Department of Ten-Year Effect of Six 

Site-Preparation Treatments 

Forest Senrice on Piedmont Loblolly Pine Survival 

and Growth 

Southeastern Forest 

Experiment Station M* ~~~d ~d~~~d~ 

Rewarch Paper 

SE-288 
Ten-Year Effect of Six 

Site-Preparation Treatments 

on Piedmont Loblolly Pine Survival 

and Growth 

M. Boyd Edwards 

ABSTRACT 

Limited information is available on growth responses to 

different levels of intensity for site preparation in the 

Piedmont. h the present study, six intensities of site 

preparation were compared for their effect on survival, 

height ad &meter growth, total volume produced, and 

basal area per acre for the ht 10 years after treatment. 

Rates of survival and growth were lower for pines in 

the control plots than for any ohhers. Ln general, tree 

performance improved as the intensity of site preparation 

increased. 

Keywords: Pinas taeda, yield, 

The need to evaluate and understand the benefits 

of site preparation is critical to forest managers 

who daily must make decisions that provide results 

in terms of pine survival and growth for their 

customers. There are few long-term studies on 

loblolly pine (Pings taeda L.) in the Piedmont that 

can be utilized for this purpose. 

The present study compares pine survival, height 

and diameter growth, total volume produced, and 

basal area after 10 growing seasons for a variety 

of site-preparation treatments. This information 

will benefit foresters and land managers, as well as 

private landowners in the Piedmont as they select 

site-preparation treatments that help maximize 

survival and "snefit growth of their planted pines. 

Methods 

The study is on an 84-acre tract in the lower 

Piedmont sf Georgia, at the Witchiti Experimental 

Forest. The original stand of loblolly pine (Pinus 

taeda L,) mixed with dogwood (Cornus florida 

L.) and sweetgum (Liquidambar styraczfiua L.) 

was harvested in 1984. and planted with improved 

loblolly pine seedlings in early 1982 on a spacing of 

6- by 10-feet. Site index for the whole study area 

averaged 80 feet at base age 50 years. neatment 

plots were arranged in blocks to reduce the variation 

of site within blocks. 

The following six site-preparation treatments were 

randomly assigned to the treatment plots and are 

listed in order of increasing intensity. 

1. Clearcvt only (control)-No site preparation. 

2. Chainsaw-All residual trees greater than 1-inch 

d. b. h. were removed by chainsawing in August 198 1. 

3. Shear and chop-Shearing was performed with a 

KG-blade mounted on a D7 tractor in September 

1981. Between September and November 1981, a 

single pass was made with a single-drum chopper. 

4, Shear, chop, and herbicide-In addition to 

shearing and chopping as in treatment 3, 0.5 cm3 

Velpar Gridball pellets (hexazinone) with 10-percent 

a.i. were applied in a 1.9- by-1.9-foot grid at a rate 

of 25 pounds per acre in March 1982. 

5. Shear, rootmke, bgrn, and disk-Vegetation was 

sheared and rootraked into windrows in September 

1981. Most of the material in the windrows was 

consumed By burning in October 1981, and the 

remaining debris and ash were scattered over the 

plot with a dozer blade. Plots were disked with an 

offset harrow to a depth of 6 to 8 inches in October 

'1981. 

6. Shear, r~otrake, burn, disk, fer;tilize, and 

herbicide--Site preparation was the same as 

described in treatment 5, except that ammonium 

nitrate (34-0-0) was broadcast by hand at the rate 

of 300 pounds per acre in March 1983 and Oust 

weed killer, containing 75-percent sulfometuron 

methyl, was applied at a rate of 8 ounces per acre 

in April 1983, with backpack sprayers. Herbaceous 

weeds were essentially absent during most of the 

1983 growing season. 
Study Design and h4easurements 

Tlle study design was a randomized complete block. 

Each treatment plot covered 2 acres, and each of 

the six treatments was replicated five times. The 

five blocks were located by topographic position to 

avoid obvious site-quality differences and to ensure 

reasonable uniformit'y within blocks. Two or three 

soil series occur on the area, and there is much 

variation in surface texture and organic matter 

content (Miller and Edwards 1985). Each treatment 

plot had a 0.2-acre internal measurement plot. 

Every tree in each measurement plot was measured 

for d.b.h. with a diameter tape and measured for 

total height with a telescoping height pole. Every 

tree was examined for tip moth and fusiform rust 

infection. Since little or no damage was found 

when these conditions were measured at the 5-year 

interval, no further measurements were taken at the 

10-year interval (Edwards 1990). 

Trees were measured annually for the first 5 years 

and again after the 8th and 10th growing seasons. 

Analysis of variance procedures were used to test 

for significance by treatment differences in height, 

diameter, percentage survival, and volume growth. 

Duncan's multiple range test was used to determine 

whether differences among means were significant 

at the 0.05 level. All data analyses were performed 

with the Statistical Analysis System (SAS 1985). 

Results and Discussion 

Survival 

At the conclusion of the first growing season, 

the only significant difference in survival among 

site-preparation treatments was for treatment 4 

(table 1). Survival in treatment 4 was significantly 

Table 1--Loblolly pine survival at 1, 3, 5, 8, and 10 years after reestablishment 

with six site-preparation treatments 

-- - 

Survival afterTreatment a 1 year 3 years 5 years 8 years 10 years 

Percent 

Within growing seasons, means followed by the same letter are not significantly different 

(P = 0.05). 

al = Clearcut only 

2 = Chainsaw 

3 = Shear and chop 

4 = Shear, chop, and apply herbicide 

5 = Shear, rootrake, burn, and disk 

6 = Shear, rootrake, burn, disk, fertilize, and apply herbicide 

b~hirty-five percent of planted pines in treatment 4 were killed in the first year by hexazinone in 

combination with too much rain immediately after application. Mortality was replaced in the 

second year. 
reduced because about 3 inches of rain fell in a short 

period and rapidly distributed a large quantity of 

hexazinone on the soil surface. The hexazinone 

killed about 35 percent of the planted pines. The 

herbicide also provided approximately 80-percent 

control of the herbaceous and woody plants after 

the first growing season. Replacement pines were 

planted on treatment 4 plots the following winter so 

that this treatment could remain part of the study. 

After three growing seasons, a survival trend became 

evident: survival was higher on treated plots than 

on colltrol (untreated) plots. At this time, survival 

was highest (98 percent) after treatment 5. 

Survival through five growing seasons was a 

respectable 84 percent on control plots. The three 

most intensive treatments significantly improved 

survival, and the best results (97 percent) were from 

treatments 5 and 6. At this time, it was evident 

that surviva! iscreased somewhat ;as intensity of site 

preparation increased. 

In the eighth growing season, survival was highest 

(96 percent) after treatment 5. akeatment 6, which 

provided the highest intensity of site preparation, 

ranked next with 93-percent survival. Rankings of 

the remaining three site-preparation treatments and 

the control were as they had been at the end of the 

fifth growing season. 

After 10 growing seasons, survival averaged 72 

percent on control plots. That average was lower 

than any of the treated averages. As intensity 

of site-preparation treatment increased, survival 

percentr;~ge gradually improved. Between years 8 

and 10, survival of trees in treatments 5 and 6 

declined by only 2 percentage points. Both of these 

treatments show excellent levels of survival, and 

their difference is only of statistical significance 

and not of any practical significance. In fact, even 

on control plots, the overall survival of 72 percent 

equates to 523 trees per acre after 10 years. Many 

land managers would be satisfied with this stocking 

level, and most foresters would characterize survival 

as excellent after all of the treatments. 

The fate of seedlings in treatment 4 is instructive. 

Some 35 percent of them were replants for spots 

where hexazinone had killed seedlings. Survival of 

originals and replants was better than on control 

plots and those receiving lesser intensities of 

treatment. At least in this instance, replanting was 

successful. 

Tree Heights 

By the end of the third growing season, mean 

tree height and height growth were beginning to 

conform to a trend of increasing as intensity of site 

preparations increased, At this time, mean height 

for all treatments except treatment 4 exceeded that 

of the control (table 2). Treatment 6, the rnost 

intensive site-preparation treatment, had the tallest 

trees and the most height growth. At the end of the 

fifth growing season, heights and height growth of 

all treatments exceeded those of the control plots. 

In general, the trend toward better tree-height 

growth with increasing intensity of treatment 

continued, and treatment 6 yielded the largest mean 

tree height and the greatest mean height growth. 

Shearing and chopping (treatment 3) and shearing, 

windrowing, burning and disking (treatment 5) 

produced the second-tallest trees. 

In general, trees in all treatments approximately 

doubled their heights between ages 5 and 8. On 

treatment 3 (shear and chop) tree heights increased 

from 10.2 to 21.4 feet. The treatment average was 

the third largest after eight growing seasons. Results 

of this treatment are of special interest because this 

treatment may be the rnost common site-preparation 

procedure utilized on Piedmont sites today. Trees in 

treatment 6 had the greatest average height at 24.2 

feet, but this average was not significantly better 

than the 22.1 feet from treatment 5. 

After 10 growing seasons, the trend of increasing 

height and height growth (except treatment 4) with 

increasing intensity of site preparation was clear. 

The control trees had the least height growth since 

the end of the eighth growing season, when mean 

height was 20.8 feet. 'llreatment 4 (shear, chop and 

herbicide) yielded the next-shortest trees at 23.9 feet 

but the third-largest increase in growth since year 8 

at 6.0 feet. Remember that one-third of treatment 4 
Table %-Effects of six site-preparation treatments on mean height and periodic height growti1 at 

1, 3, 5, 8, and 10 years after establishment 

Height Height Growth Height Growth Weight Growth Weight Growth 

?Ireatmenta 1 year 3 years 5 years 8 years 10 years 

Feet 

FVitbin growing seasons, means followed by the sam letter are nod significantly different (P = 0.05). 

a 1 = Clearcut only 

2 = Chainsaw 

3 = Shear and chop 

4 = Shear, chop, and apply herbicide 

5 = Shear, rootrake, burn, and disk 

6 = Shear, rootrake, burn, disk, fertilize, and apply herbicide. 

trees were a year younger. Results from treatment After 10 growing seasons, trees in treatment 2 

3 (shear and chop) are only slightly less than from (chainsaw) were still growing faster in height than 

treatments 5 and 6, which yielded the best mean control trees. This site-preparation treatment may 

tree height after 10 growing seasons. Height growth interest landowners who do not wish to invest in 

since year 8 was similar for treatments 3, 5, and 6. more costly treatments or landowners who want to 

minimize the impacts of site preparation. 
By the end of the fifth growing season, trees were 

tall enough to measure diameters at breast height 

(table 3). At all three measurement times, mean 

diameters from all site-preparation treatments 

exceed those from control plots. Also, at all three 

measurement times, the trees in the most intensive 

treatment (treatment 6) had the largest diameters. 

Again, with exception of treatment 4, diameters 

tended to increase with increasing intensity of site 

preparation. 

Table 3-Effect s of six site-preparation treatments on. individual 

tree d.b.h, at 5, 8, and 10 years after establishment 

Diameter breast height atTreatment & 5 years 8 years 10 years 

Inches 

0.8d 1.9d 

1. lcd 2.2cd 

P .5b 3. lab 

1.2bc 2.8bc 

1.5b 3.5ab 

1.9a 3.7a 

Within growing seasons, means followed by the same letter are not 

significantly different (P = 0.05). 

a1 = Clearcut only 

2 = Chainsaw 

3 = Shear and chop 

4 = Shear, chop, and apply herbicide 

5 = Shear, rootrake, burn, and disk 

6 = Shear, rootrake, burn, disk, fertilize, and apply herbicide 
Cubic Volume 

Total cubic volume at ages 5, 8, and 10 were 

calculated with a simultaneous total and 

merchantable stand volume equation developed by 

Bailey and others (1985): 

Where V = total volume (ft3), 

D = diameter breast height, and 

H = total height. 

Beatment 6 had 20 percent more volume than 

treatment 5 after 8 growing seasons and 11 percent 

more volume after 10 growing seasons (table 4). 

This treatment yielded 4.8 times more volume per 

acre than the control after 8 growing seasons and 

4.3 times more after 10 growing seasons (fig. 1). 

The benefits of fertilizing and herbicide application 

in treatment 6 over treatment 5 continued to 

accumulate through age 10. At that time, volume 

growth for all treatments exceeded that of the 

control. Treatment 2 (chainsaw) was the only one 

that did not provide significantly more volume 

growth than the control (table 4). 

Table 4-Mean total volume per a c r e a f t e r 5, 8, and 10 growing seasons and periodic 

volume growth between 5 to 8 and 8 to 10 growing seasons, by treatment 

Volume at end of- Growth betweenTreatmenta 5 years 8 years 10 years 5-8 years 8-10 years 

-- -- 

Cubic feet 

Within growing seasons, means followed by the same letter are not significantly different 

(P = 0.05). 

"1 = Clearcut only 

2 = Chainsaw 

3 = Shear and chop 

4 = Shear, chop, and apply herbicide 

5 = Shear, rootrake, burn, and disk 

6 = Shear, rootrake, burn, disk, fertilize, and apply herbicide 
Volume 

(ft3/acre) 

1400 

3 4 

Treat rnents 

Figure 1-Mean total volume per acre by treatment at 5, 8, and 10 years after establishment, by six site-preparation 

treatments: (1) clearcut only (control); (2) chainsaw; (3) shear and chop; (4) shear, chop, and herbicide; (5) shear, 

rootrake, burn, and disk; and (6) shear, rootrake, burn, disk, fertilize, and herbicide. 
Basal Area 

Table 5 shows average basal area per acre for the 

different treatments by ages, and figure 2 shows 

the results in the form of a histogram, Chopping 

after shearing (treatment 3) doubled the basal 

area over that of the control (treatment 1) and 

chainsaw (treatment 2) after 8 years. Treatment 4 

shows similar results. Tkeatment 5 had 3.4 times 

as much basal area, and the additional fertilization 

and herbaceous weed control (treatment 6) had 

3.8 times more basal area. After 10 growing 

seasons, significance among treatments levels out 

into two groups: (1) treatments 3, 4> 5, and 6, 

and (2) treatments 1 and 2. Group 1 treatments 

are all significantly better than the less intensive 

treatments. Likewise, basal area growth from end of 

year 8 to end of the 10th growing season is in two 

distinct groupings of significance. 

Table 5---Mean basal area per acre, by treatment, at end of years 8 and 

10, and mean basal area growth from year 8 to end of year 10 

Basal area at end ofTreatment t~ 8 years 10 years Growth 

14. lc 

19.0~ 

37.5b 

36.5b 

48. lab 

54.0a 

Sqzrare feet 

Within growing seasons, means followed by the same letter are not significantly 

different (P = 0.05). 

al = Clearcut only 

2 = Chainsaw 

3 = Shear and chop 

4 = Shear, chop, and apply herbicide 

5 = Shear, rootrake, burn, and disk 

6 = Shear, rootrake, burn, disk, fertilize, and apply herbicide 
Baal 

Area (fi2) 

3 4 

Treatments 

Figure 2-Mean basal area per acre by treatment at end of years 8 and 10, by six site-preparation treatments: (1) 

clearcut only (control); (2) chainsaw; (3) shear and chop; (4) shear, chop, and herbicide; (5) shear, rootrake, burn, 

and disk; and (6) shear, rootrake, burn, disk, fertilize, and herbicide. 
Conclusions Literature Cited 

The plots receiving the highest intensive 

site-preparation treatments had the most survival 

after 10 growing seasons. Shearing, rootraking, 

burning, and disking (treatment 5) was better than 

the others with 94 percent survival after 10 years. 

All treatments improved survival. Height growth 

and volume production were best for the most 

intensive treatments (5 and 6). Trees in treatment 6 

bad 2.2 inches more diameter at 10 years than the 

control trees. 

It was previously reported (Edwards and Shiver 

1991) that at the end of eight growing seasons 

total volume per acre for the most intensive 

treatment was 3.8 times more than for the control 

and all site-preparation treatments resulted in 

more growth than the control. After 10 growing 

seasons, treatment 5 with shear, rootrake, burn, and 

disk yielded 1,158.7 cubic feet per acre. The most 

intensive treatment (treatment 5), with additional 

fertilization and herbaceous weed control, yielded 

an additional 128 cubic feet per acre. The chainsaw 

treatment (treatment 2) was not significantly better 

than the control but appeared to yield an additional 

116.6 cubic feet per acre. 

Arguably, we will not know the full effects of 

the imposed treatments until the plantings reach 

rotation age. We plan to continue the study, and 

results at later ages will be reported. Results 

through age 10, however, appear to provide a fairly 

good basis for choosing among treatments. The 

cheapest and lowest intensity treatments permitted 

establishment of loblolly pine plantations after 

harvest of a pine stand. By age 10, it is clear, that 

yields can be increased a great deal by preparing 

sites more intensively. Whether intensive site 

preparation is the best choice will depend on the 

objectives and the financial st atus of the individual 

Iandowner . 

Bailey, Robert L.; Gsider, Galen; Rheney, John VV.; 

Pienaar, Leon. 1985. Stand structure and yields 

for site-preparation of loblolly pine platations in the 

Piedmont and upper Coastal Plain of Alabama, Georgia, 

and South Carolina. Res. Bull. 328. Athens, GA: 

University of Georgia, College of Agriculture Experiment 

Station. 118 pp. 

Edwards, M. Boyd 1990. Five-year responses of Piedmont 

loblolly pine to six site-prepsation treatments. Southern 

Journal of Applied Forestry 14(6): 3-6. 

Edwards, M. Boyd; Shiver, Barry B. '1991. Evaiuatioln 

of six site-prepmation treatments on growth and survivd 

of loblolly pine in the Georgia Piedmont. In: Coleman, 

Sandra S.; Neary, Daniel C., comps., eds. Proceedings of 

the 6th bienraial southern silvicultural researd~ conference; 

1990 October 30-November 1; Memphis, TN. Gen. 

Tech. Rep. SE-70. Asheville, NC: U.S. Departmer~t 

of Agriculture, Forest Service, Southeasteni Forest 

Experiment Station: 147-1 54. 

Miller, Janres W.; Edwards, M. Boyd. 1985. Impacts of 

various intensities of site preparation on Piedmont soils 

after 2 years. In: Shoulders, Eugene, ed. Proceedings of 

the 3rd biennial southern silvicultufal research conference; 

1984 November 7-8; Atlanta, GA. Gen. Tech. Rep. SO-54. 

New Orleans, LA: U.S. Department of Agriculture, 

Forest Service, Southern Forest Experiment Station: 65-73. 

SAS Institute Inc. 1985. SAS user's guide: Statistics. 

5th ed. Cary, NC: SAS Institute hc. 956 pp. 
Edwards, M. Boyd. 1994. Ten-year effect of six-site preparation treatments on I 

Piedmont loblolly pine survival and growth. Res. Pap. SE-288. Asheville, NC: 1 

U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment I 

Station. 10 pp. I 

Limited information is available on growth responses to differed levels of intensity 

I 

for site preparation in the Piedmont. In the present study, six intensities of I 

site preparation were compared for their effect on survival, height and diameter I 

growth, total volume produced, and basal area per acre for the first 10 years after I 

treatment. Rates of survival and growth were lower for pines in the control plots I 

than for any others. In general, tree performance improved as the intensity of site I 

preparation increased. I 

I 

Edwards, M. Boyd. 1994. Ten-year effect of six-site preparation treatments on I 

Piedmont loblolly pine survival and growth. Res. Pap. SE288. Asheville, NC: I 

U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment I 

Station. 10 pp. 1 

Limited information is available on growth responses to different levels of intensity I 

for site preparation in the Piedmont. In the present study, six intensities of I 

site preparation were compared for their effect on survival, height and dimeter I 

growth, total volume produced, and basal area per acre for the first 10 years after I 

treatment. Rates of survival and growth were lower for pines in the control plots 1 

thm for any others. In general, tree performance improved as the intensity of site I 

preparation increased. I 

I Keywords: Growth response, loblolly pine growth, pine survival, Pinua taeda , I Keywords: Growth response, loblolly pine growth, ~ine survival, Pinur Iaeda , 1 

I treatment intensity, yield. I treatment intensity, yield. 

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