United States

Department of

Agriculture Sawtimber by

Forest Service

Southern Forest

Experiment Station

New Orleans,

Louisiana

Research Paper

so-1 79

February, 1982

PrescriptionThe Sudden Sawlog

Story Through Age 33

J. D. Burton
Sawtimber by Prescription-The Sudden Sawlog Story

Through Age 33

J. D. Burton

INTRODUCTION

Even-aged loblolly pine stands on good sites can

grow sawtimber to a dbh of 17 to 18 inches in 33 years,

with a standing volume of 13.1 M bm International

i/4-inch rule to an B-inch top d.i.b. The requirements

for achieving this are ample growing space and green

pruning for selected highrvalue individual trees, followed by understory control. The landowner must sacrifice some of the small-diameter roundwood that

could be harvested in intermediate cuttings. Stumpage value of small-diameter roundwood today is low,

and this sacrifice may not be painful. This paper reports yield, standing volume, and stand structure

through age 33, obtained in a continuing study near

Crossett, Arkansas.

METHODS

Plot Establishment

An old-field loblolly pine plantation was selected for

the study. The stand had been bar-planted at a spacing

of 6 x 6 feet, rows following contours. In February 1954

the stand was 9 years old (10 years from seed germination) and contained 1,100 pine trees/acre. Basal area

in pines at least 1.0 inch dbh was 71 ft?/aFre. Dominant

and codominant trees averaged 22 feet m height and 4

inches dbh. Nearly all trees were in the I- through

&inch dbh classes. There was very little understory

vegetation. The 58year site index for the loblolly pine

plantation was determined to be between ‘90 and 100

feet.

Twelve 0.25acre square plots, each with a 0.5

chain-wide isolation zone, were established and organized into 3 blocks on the twin bases of basal area

and suspected differences in site quality. Researchers

selected and tagged 100 crop trees/acre (25/plot) that

were well spaced, vigorous, and well formed. Four

treatments were assigned randomly within each

block. Wo treatments began immediately and two

began at age 12, when the average tree had attained

merchantable pulpwood size (at least 4.6 inches dbh,

containing at least two 63-inch bolts to a 3-inch top

d.i.b.). The four treatments were:

Sawtimber-only.--AlI but the crop trees were cut at

age 9, which reduced basal area to 10 fi?/acre (table 1,

fig. 1). Stands were thinned to 76 trees/acre at age 19,

64 trees/acre at age 24,48 trees/acre at age 27, and 41

trees/acre at age 30.

Sawtimber-pulpwood.-Thinnings at ages 9 and 12

removed noncrop trees whose crowns were within 5

feet of crop tree crowns. The last noncrop trees were

removed at age 15. Further thinning left 80 trees/acre

at age 19,63 trees/acre at age 27, and 52 trees/acre at

age 30.

Delayed-sawtimber-All but the 100 crop trees/acre

were removed at age 12. The 0.25-acre plots were

thinned to 80 trees/acre at age 24,53 trees/acre at age

27, and 45 trees/acre at age 30.

Control.-Plots were thinned, mainly from below, to

a basal area of 85 ft*/acre at age 12 and every 3 years

afterward through age 30. The thinnings reduced

stand density to 712 stems/acre at I.2 years, 468 at 15

years, 333 at 18 years, 251 at 21 years, 193 at 24 years,

148 at 27 years, and 116 at 30 years.

Thinnings at age 9 were precommercial. Thinnings

at age 12 were largely commercial. After all noncrop

trees were removed from the intensive treatment plots

(sawtimber-only, sawtimber-pulpwood, and delayedsaw-timber), the prescriptions for thinning specified

the stand to be retained in terms of trees/acre through

age 24 and in basal area from age 27 onward The

timing and severity of thinnings were based on

periodic dbh growth. The intent was to keep trees in

the intensive treatments growing markedly and consistently faster than crop trees in control plots and to

keep sawtimber-only trees growing distinctly faster

than sawtimber-pulpwood and delayed-sawtimber

trees.

Crop trees in the intensive treatments were pruned

to about half their total height after the tirst thinning

in the treatment and every 3 years afterward through

J. D. Burton is Soil Scientist, Alexandria Forestry Center, Southern forest Experiment Station, Forest Service-USDA, Pineville, Louisiana.

The Crossett Division, Georgia-Pacific Corporation, provided land and technical assistance.
Cubic-foot volume to a 3-inch d.i.b. was obtained from

a standard volume table entered by dbh and total

height (U.S. Dep. of Agric. For. Serv. 1976) from age 12

to age 18. Beginning with age 21, cubic-foot and boardfoot volumes were calculated by the STX Program

(Grosenbaugh 19671.

Pulpwood volumes in this paper are in cunits. One

cunit = 100 ft3 of peeled wood.

Board-foot volumes, Int. %-inch rule and Doyle rule,

were reckoned for two utilization thresholds: (1) stems

at least 9.6 inches dbh containing one or more 16-foot

logs to an 8-inch top d.i.b., and (2) stems at least 7.6

inches dbh containing one or more 16-foot logs to a

6-inch top d.i.b. Differences between estimates to

these two thresholds represented material in small

sawlogs suitable for conversion by a chipping headrig,

pruning to an awmge height of 11 feet at age 9.

age 24; pruned bole length then equaled two 16-foot

logs plus trimming allowance (fig. 2). Initial pruning

went to a minimum height of 9 feet; pruned length on

some trees was 10 or I2 feet because of internode

length, and height to base of live crown before pruning

at age 9 was 5 to 7 feet. Pruning at age 9 removed about

35 percent livecrown length from the average dominant-stand tree and left a crown 13 feet long.

Beginning at age 19, the woody understory (hardwood sprouts,’ vines and shrubs) in intCnsive-culture

plots was controlled by mowing at 2-year intervals. . The aim of heavy thinning and understory control was

1

to reduce competition for soil moisture and thus to ii

accelerate the growth of crop trees.

Except for frequency of thinnings, the control treat- i

ment simulated conventional industrial silviculture

as was in practice when the study began, with no

pruning at all and no understory control before age 27.

I.b:; ‘. . .>7:

.- .I

Measurements and Analysis I%sI i .

&

The dbh of all trees was measured every 3 years,

beginning at age 9. Total and merchantable heights

were measured from age 12. Upper-stem measurements were made, beginning at age 21, which permitFigure 2.-T& sawtimber-pulpwood plot had just i& it+ fin&

pruning to an avenge height of2 logs (92 fee) wken the

photograph was taken in March 1969. Pruned branches

were kft to decompose where they fell. The open area in

the background is a utility right-of-way.

2
Table I.-Basal area before and after thinning, ages P-33

& e Stand condition

Sawtimberonly

Treatment

Sawtimber- Delayedpulpwood sawtimber Control

yrS. ___________.____-___-___---_--- square feet/acre - .------ -- ---------______

9 Before cut 71 70 6 9 74 After cut 10 31 1 1

1 2 Before cut 25 65 118 124

After cut 1 29 15 85

15 Before cut 47 56 33 119

After cut 1 37 1 84

18 Before cut 69 57 55 113

After cut 1 i 1 85

19 Before cut 75 63 61 90 After cut 60 52 1 1

21 Before cut 69 63 73 103

After cut 1 1 1 85

2 4 Before cut 82 78 8 8 103

After cut 70 75 7 5 85

2 7 Before cut 84 89 8 9 104

After cut 65 76 63 85

3 0 Before cut 76 88 74 101

After cut 65 75 65 82

3 3 Before cut 70 81 73 97

AtIer cut I I I 1

‘Plots in this treatment were not thinned at this time.

Standing volume is defined as cubic-foot or boardfoot volume of stemwood per acre in living trees before

thinning, at any specified age. Yield to any age consists of standing volume plus volume in all previous

merchantable thinnings plus any volume in natural

mortality occuring in merchantable trees after age 12.

Two measures of stem form were calculated, Girard

form class and absolute form quotient (AFQ). The latter is obtained (Husch et al. 1972) as:

AFQ = (bole d.o.b. midway between

breast height and apex)

dbh

Differences in some of the tree and stand attributes

due to treatment were evaluated by analysis of

variance and Duncan’s Multiple Range ‘I&t. Significance was preset at the 0.05 level.

RESULTS

Growth in Dhh

At age 33, mean dbh was 17.1 to 18.0 inches (by

treatment means) in the intensive treatments and

12.3 inches in the control. These diameters reflect both

differences in growth rate due to treatment and

changes in mean stand diameter associated with thinning. For crop trees remaining at age 33, mean dbh

growth after initial thinning averaged 0.57 inch/year

in sawtimber-only, 0.54 inch/year in sawtimberpulpwood, 0.56 inch/year in delayed-sawtimber, and

0.34 inch/year in control. Periodic growth rates for

crop trees in each treatment were:

Treatment

Stand

ai9

years

9-12

12-15

15-18

18-21

21-24

24-27

27-30

30-33

Sawtimber- Sawtimber- Delayedonly pulpwood sawtimber’ Control

__-.__------_---_------- inchlyear-------------------------

0.87 0.60 . . . . . . . . . . . . . . . . . .

0.90 0.80 0.93 0.37

0.70 0.73 0.80 0.37

0.47 0.57 0.57 0.30

0.43 0.50 0.43 0.30

0.43 0.43 0.43 0.40

0.40 0.37 0.43 0.27

0.33 0.30 0.33 0.33

In other loblolly pine thinning studies, researchers

found very little difference in mean dbh of the 50

largest trees/acre between thinned and unthinned

plots for ages 25 to 60 (Andrulot and Williston 1974),

or between levels of thinning for ages 20 to 45 (Feduccia and Mosier 1977). In this study, however, betweentreatment differences in growth of larger trees developed early and persisted through age 33 (fig. 3).

Comparisons were based on the largest 48 trees/acre

from age 15 through 30; after age 30 the basis was 36
I9

17 -

16 -

-\‘5-

2

s l4-

2

: 13 -

x

: 12-

2

z

,I2 IO -

TI SAWTIMBER-ONLY

9- TP SAWTIMBER-PULPWOOD

T3 DELAYED-SAWTIMBER

*-

T‘l/

T4 CONTROL

7-

0 1 I ! 8 I 8

IS I8 21 24 27 30 33

AGE OF STAND (YEARS)

Figure X-Quadratic mean dbh by treatment and age of the 48

largest trees per acre (36 trees at age 33).

trees/acre because one plot had been reduced to that

level. At age 15, all four treatment means were significantly different. From age 18 through age 21 the sawtimber-pulpwood and .delayed-sawtimber means were

not different, but they were significantly smaller than

sawtimber-only and significantly greater than the

control. From age 24 through age 33, mean dbh was

not significantly different among the intensive treatments, but it was significantly greater than in the

control. Thinning levels in these intensive treatments

differed more from the control than in the other studies cited.

Diameter Distribution

Following initial thinning at age 9,99 percent of the

sawtimber-only trees were in the 3-inch, 4-inch, and

&inch dbh classes. The first thinning left 452 stems/

acre in the sawtimber-pulpwood plots, with 16 percent

of them in the l-inch and 2-inch classes. At age 12,

before thinning, 95 percent of the sawtimber-only

trees were in the 6-inch class and larger (fig. 41, compared to 39 percent of the control trees.

At age 21, before thinning, all of the sawtimber-only

trees, 98 percent of the sawtimber-pulpwood, 97 percent of the delayed-sawtimber trees, and 4 percent of

the control trees were in the IO-inch class and larger.

Before thinning at age 27,98 percent of the sawtimber-only trees were in the 13-inch dbh class or larger.

Ninety-five percent of the sawtimber-pulpwood, 90

percent of the delayed-sawtimber, and 2 percent of the

AGE 21 AGE 2 7 AGE 33

40-

DBti CLASS

Figure I.--Stnnd structure by treatment before thinning at ages 12,

21,27, and 33.

control trees were in the 13-inch class and up. Fortythree percent of the control trees were less than 10

inches in dbh.

At age 33, all the sawtimber-only trees, all the sawtimber-pulp.wood trees, and 97 percent ofkhe delayedsawtimber trees were 15 inches or more in dbh. In the

control plots, 99 percent of the trees were in the loinch or larger classes, but only 2 percent were as large

as 15 inches.

Cunit Volumes, Standing and Harvested

Standing stemwood volume to a 3-inch top was always significantly greater in control plots than intensive culture plots, except at age 12, when delayedsawtimber plots had the greatest volume (table 2).

Neither delayed-sawtimber nor control plots had yet

been thinned; the difference at age 12 was a random

consequence of pretreatment stand density, not a result of treatment. Sawtimber-only plots, having been

drastically thinned at age 9, contained very little

volume. At age 18, they supported 12.35 cunits/acre.

At age 27, the plots in the three intensive treatments

averaged 22 cunitslacre and control plots 26. Because

of periodic thinnings, standing volumes at ages 30 and
Table P-Standing pulpwood volumes before thinning and volumes removed in commercial thinnings plus natural mortality: merchaniable stemwood in cunits to a 3-inch top d.i.b.’

Sawtimber- Sawtimber- Delayed

Age (years) only pulpwood sawtimber Control

________-__--_--___------*----------------.--- cunits/acre____-_------._--_-__-------------------

Standing Volume

12 2.15 4.75 7.65 6.83

1 5 6.30 7.30 4.21 13.94

18 12.35 9.82 9.11 18.78

21 13.40 12.16 13.48 18.97

24 18.97 17.85 19.64 22.54

27 20.87 22.51 22.54 26.24

3 0 20.23 23.45 20.29 25.68

33 21.04 24.04 21.92 28.05

Volumes cut and mortality

12 0 .96 6.40 1.93

15 0 2.32 0 3.72

18 0 0 0 4.15

19 2.33 1.82 0 0

21 0 0 0 3.063

24 2.68 ,662 2.88 3.92

27 4.51 3.39 6.28 4.33

3 0 2.74 3.27 2.68 4.42

30-332 .63 .54 0 0

Total volumescut 12.89 12.96 18.24 25.53

‘One cunit = 100 ft3 of peeled wood.

Wolume by mortality alone.

31ncludes .I3 cunit mortality.

Table 3.-Standing volumeper acre before thinning in different classes ofproduct, ages21 through 33

Sawtimber- Sawtimber- DelayedAge Product Unit only pulpwood sawtimber Control

21

24

27

30

33

Pulpwood Cunit .83 .82 1.05 12.71

SS’ M bm Int. % .95 1.17 1.92 2.74

cs2 M bm Int. % 6.14 5.03 4.77 .06

ss M bm Doyle .30 .36 .60 .65

cs M bm Doyle 3.19 2.45 2.32 .03

Pulpwood Cunit .86 .85 1.03 8.63

ss M bm Int. % .84 .91 1.24 .5.11

cs M bm Int. % 9.84 8.94 9.37 1.46

ss M .bm Doyle .28 .32 .38 1.32

cs , M bm Doyle 5.60 4.88 5.00 .59

Pulpwood Cunit .75 .98 1.04 4.77

ss M bm Int. % 51 .67 .75 5.35

cs M bm Int. % 11.71 12.19 11.94 5.31

ss M bm Doyle .ll .14 .16 1.35

cs M bm Doyle 7.13 7.18 6.87 2.34

Pulpwood Cunit .44 .64 .54 2.95

S S M bm Int. % .44 .58 .49 4.93

cs M bm Int. % 11.95 13.43 11.64 6.69

ss M bm Doyle .09 .12 .lO 1.32

cs M bm Doyle 7.81 8.42 7.30 3.11

Pulpwood Cunit .40 53 .49 1.78

S S M bm Int. % .38 .46 .44 2.60

cs M bm Int. % 12.89 14.39 13.13 11.76

ss M bm Doyle .08 .lO .09 .61

cs M bm Doyle 8.87 9.56 8.78 5.99

‘SS (small sawlogs): Trees between 7.6 and 9.5 inches dbh to a 6-inch top d.i.b., also between the

8-inch and g-inch d.i.b. in upper stems of trees containing conventional sawlogs.

2CS (conventional sawlogs): Trees at least 9.6 inches dbh containing at least one 16-foot log to an

8-inch top d.i.b.
33 years were not much different from those at age 27;

&at was different was number and average size of

trees.

Total volume of stemwood to a 3-inch top in commer-

-ial thinnings, from age 12 onward, averaged 12.93

cunits/acre in sawtimber-only and sawtimberpulpwood, 18.24 cunits in delayed-sawtimber, and

25.53 cunjts in the control (table 2); these totals were

significantly different.

Natural mortality was slight. One tree was salvaged

jn a control plot at age 20, two trees in a sawtimberpulpwood plot at age 24, and one tree each in a sawtimber-only and a sawtimber-pulpwood plot between ages

30 and 33.

Sawtimber Standing Volume

Sawtimber first appeared in standing volumes at

age 21. Nearly every tree in the intensive treatments

included a conventional sawlog in the butt and some

pulpwood in the upper stem. Control plots contained

only 12 trees/acre that were at least 10 inches dbh.

The pulpwood, small-sawlogs, and conventionalsawlogs volumes in table 3 from age 21 through 33 are

additive. At age 21, for example, sawtimber-only plots

contained 0.83 cunit/acre of pulpwood plus 6.14 M bm

(Int. %) of conventional sawlogs plus 0.95 M bm in

small sawlogs, or 0.83 cunit/acre plus (6.14 + 0.95) M

bm to a 6-inch top. Board-foot volumes are also given

in Doyle-rule equivalents; thus, sawtimber-only plots

at age 21 contained (3.19 + 0.30) M bm (Doyle) to a

6-inch top plus 0.83 cunit/acre of pulpwood to a 3-inch

topAnalysis of variance in board-fdot standing volumes

and yields, to the two thresholds of merchantability,

was done only with Int. % values. Sawtimber-only

plots contained more volume than sawtimberpulpwood and delayed sawtimber at age 21; control

plots contained less at the same age (table 3). At age

30, volumes in intensive treatments were greater than

those in control but not different from each other. At

age 33, the only significant difference %vas between

sawtimber-pulpwood and control.

In board feet to a 6-inch top (trees at least 7.6 inches

dbh), standing volume at age 21 averaged 6.67 M bm

(Int. %) in intensive treatments and differed significantly from the 2.80 M bm in control. At age 30, only

the sawtimber-pulpwood plots had significantly greater standing volume than control. At age 33, there was

no difference between treatments. The initial effect of

drastic thinning on board-foot growth was dramatic,

but it diminished rapidly.

Sawtimber Yield

Board-foot yield to ages 21 and 24 consisted entirely

of standing volume. From age 24 onward, total yield in

conventional sawlogs was nearly equal in all three

intensive treatments (table 4). Conventional sawlog

yield from intensive culture was 6 times that of control

at, age 24,2.4 times at age 27,2.3 times at age 30, and

1.5 times at age 33. In trees at least 7.6 inches dbh to a

6-inch top, total yield from intensive culture was 1.6

times that ofcontrol at age 24,1.2 times control at ages

27 and 30, and 1.09 times control at age 33, using Int.

l/4 values.

Sawtimber Volume in Thinnings

The first sawtimber thinnings removing at least 1 M

bm were in the sawtimber-only and,the delayedsawtimber at age 24 (table 5). The sawtimberpulpwood plots first produced sawlogs in thinnings at

age 27, and the control plots never did produce as much

as 1 M bm (Int. l/4) in conventional sawlogs in a thinning. No thinning was done at age 33.

Other Stand Attributes at Age 33

Girard form class averaged 81 percent at age 33.

Differences between treatments were not significant

at age 21 or any time since.

The AFQ was 71 percent at age 33 with no differences between treatments. Taper in the lower half of

the bole apparently was not much affected by thinning

intensity.

Mean height to an El-inch d.i.b. was 52 feet in all

three intensive treatments and 36 in the control. This

difference was significant. Mean height to a 6-inch

d.i.b. was 60 to 62 in intensive treatments and 51 in

control. Mean height to a S-inch d.i.b. was 70 feet in

sawtimber-only and delayed-sawtimber, 69 feet in

sawtimber-pulpwood, and 64 feet in control. Only the

difference between 70 feet and 64 feet was significant.

Total height at 33 years averaged 77 feet in control

and 79 to 80 feet in the intensive treatments; there

were no significant differences.

Mean live crown percent at age 33 was 50 in the

intensive treatments and 38 in control; the difference

was significant.

DISCUSSION AND CONCLUSIONS

Which of the four treatments is best? The answer

depends on the objective of management. The three

intensive treatments were intended to grow sawtimber in a very short time, and they did. Intensive culture’s advantage over control, in sawtimber yield to an

&inch top, rapidly diminished after age 30.

If growing sawtimber to an 8- or 6-inch top in the

shortest possible time is the landowner’s objective, and

production of small-diameter roundwood is not important, then precommercial thinning is called for, and
Table 4.- Total yield per acre of merchantable stemwood in different classes of product, ages 21

through 33.

Sawtimber- Sawtimber- DelayedAge Product Unit only pulpwood sawtimber Control

21

24

27

30

33

Pulpwood

SS’

CSZ

ss

c s

Pulpwood

s s

c s

ss

CS

Pulpwood

ss

c s

ss

c s

Pulpwood

ss

CS

ss

c s

Pulpwood

s s

CS

ss

c s

Cunit

M bm Int. %

M bm Int. %

M bm Doyle

M bm Doyle

Cunit

M bm Int. 1/4

M bm Int. ‘/s

M bm Doyle

M bm Doyle

Cunit

M bm Int. %

M bm Int. %

M bm Doyle

M bm Doyle

Cunit

M bm Int. %

M bm Int. %

M bm Doyle

M bm Doyle

Cunit

M bm Int. %

M bm Int. %

M bm Doyle

M bm Doyle

3.16 5.92 7.45 22.64

.95 1.17 1.92 2.74

6.14 5.03 4.78 .06

.30 .36 .60 .64

3.19 2.45 2.32 .03

3.19 5.95 7.43 21.49

.84 .91 1.24 5.18

9.84 8.94 9.37 1.46

.28 .32 .38 1.33

5.60 4.88 5.00 .59

3.23 6.10 7.65 20.22

.67 .70 1.13 5.93

13.00 12.55 13.03 5.41

.16 .16 .28 1.48

7.82 7.40 7.44 2.38

3.12 5.92 7.53 20.17

.I4 .74 1.16 6.54

15.65 15.48 15.81 6.94

.18 .16 .29 1.72

9.88 9.53 9.51 3.21

3.14 5.95 7.56 19.92

.75 .73 1.17 5.26

18.57 18.52 18.80 12.70

.18 .16 .29 1.28

12.22 11.89 11.88 6.41

‘SS (small sawlogs): Trees between 7.6 and 9.5 inches dbh to a 6-inch top d.i.b., also between the

El-inch and B-inch d.i.b. in upper stems of trees containing conventional sawlogs.

%S (conventional sawlogs): Trees at least 9.6 inches dbh containing at least one l&foot log to an

8-inch top d.i.b.

Table 5-Volume per acre harvested in commercial thinningsplus volume in &ad trees in different

classes of product, ages 24 through 30’

-

Sawtimber- Sawtimber- Delayed-

& e Product Unit only pulpwood sawtimber Control

24 Pulpwood Cunit .15 .02 .21 2.59

ss3 M bm Int. % .16 .03 .38 .51

cs3 M bm Int. % 1.29 .36 1.09 .I0

s s M bm Doyle .06 .Ol .12 .12

c s M bm Doyle .69 .21 .56 .03

21 Pulpwood , Cunit -20 .I6 .38 1.77

ss M bm Int. % .14 .13 .28 1.03

c s M bm Int. % 2.40 1.68 3.08 .16

ss M bm Doyle .03 .03 .06 .26

c s M bm Doyle 1.38 .90 1.65 .07

3 0 Pulpwood Cunit .06 .I4 .08 .92

ss M bm Int. % .07 .I2 .07 1.05

cs M bm Int. % 1.99 2.08 1.50 .68

ss M bm Doyle .02 .02 -02 .28

cs M bm Doyle 1.28 1.21 .a9 .32

Total Pulpwood Cunit .41 .32 .67 5.28

(Ages) SS M bm Int. % -37 .28 .73 2.59

24-30 cs M bm Int. % 5.68 4.12 5.67 .94

ss M bm Doyle .ll .06 .20 .66

c s M bm Doyle 3.35 2.32 3.10 .42

‘No cutting was done at age 33.

Y$S (small sawlogs): Trees between 7.6 and 9.5 inches dbh to a 6-inch top d.i.b., also between the

a-inch and g-inch d.i.b. in upper stems of trees containing conventional sawlogs.

3CS (conventional sawlogs): Trees at least 9.6 inches dbh containing at least one 16-foot log to an

d-inch top d.i.b.

7
the sawtimber-only treatment is the best of the four

treatments. It had the greatest dbh at every inventory,

and the greatest sawtimber yield at age 21.

If the main objective is to grow sawtimber quickly,

and a heavy early cut of merchantable pulpwood is an

important secondary consideration, then delayedsawtimber is the best of the four treatments. It produced the largest single pulpwood cut very early, its

sawlog yield from age 24 onward was not significantly

different from that of the sawtimber-only treatment,

and it involved one less pruning.

The intensive treatments used in this study could be

improved and their costs reduced. Results would not

necessarily be identical to those actually attained;

from a silvicultural standpoint, they might even be

better.

If old fields or prepared sites are to be planted for fast

growth of loblolly pine sawtimber, a spacing of 6 x 6

feet is too close, unless factors other than tree growth

are considered. Loblolly pine spacing trials in

Louisiana at Homer (Shepard 1974), Woodworth

(Feduccia and Mosier 1977), and Merryville (Campbell

and Mann 1974); and at Union, South Carolina (Balmer et al. 1975); showed that spacings of 10 x 10 or

12 x 12 feet produced sawtimber much earlier than did

spacings of 6 x 6 or 8 x 8 feet. Excessively wide spacings also are undesirable. Planting only the number of

crop trees desired, at a spacing of 21 x 21 feet, avoids

precommercial thinning, but creates other problems.

A landowner who plants at wide spacings will find that

planting costs are less, larger trees will be grown in a

shorter time, and percentage ofjuvenile corewood will

be greater (Zobel et al. 1958). TheIimbs will be coarser,

percentage of compression wood will be greater

(Haught 1957), pruning will be needed earlier, and

understory control will be needed earlier and more

often. The impact of tipmoth infestation and fusiform

rust stem infection probably will be greater than they

were in this study.

Selection of the 100 crop trees/acre at age 9 in this

study was difficult and time-consuming because many

of the more vigorous trees were forked?as a result of

tipmoth attack) or had stem galls. Many compromises

had to be made. Incidence of fusiform rust is difficult to

predict, but even minor occurrences can ruin a widely

spaced sawtimber planting. A spacing of 8 x 8 or 7 x 9

feet will offer more trees from which to choose than a

10 x 10 foot spacing.

Mowing is not the only way to control woody understory. Fire or chemicals may be cheaper. In loblolly

pine plantations, prescribed burning may be done as

early as age 12 (Crow 1970).

Pruning can be very expensive, and some landowners may be inclined to omit it. But if the trees have

undergone drastic thinning to as few as 100 trees/acre,

pruning is necessary. Without it, fast-growing young

trees at wide spacings form numerous large knots and

much compression wood. With today’s labor costs,

pruning should be restricted to the butt log and done in

one or two steps. It should leave a crown whose length

is equal to 50 percent of the total height of the tree and

be completed before d.o.b. at 17.3 feet is much greater

than 4 inches. Table 1 of Mesavage and Girard (1946)

indicates that 42 percent of the board-foot volume of a

3log tree is in the first 16-foot log.

With understory control, green pruning, and ample

growing space for selected crop trees, sawtimber can

be grown in less than 30 years. Sudden sawlogsculture

is recommended for land ranging from gently sloping

to nearly level, where site index is 90 feet or more at 50

years, and where the risk of erosion is slight.

LITERATURE CITED

Andrulot, E. A. and H. L. Williston.

1974. Growth and yield of second-growth loblolly in

central Louisiana. In Proc. Sympos. on Mgmt,. of

Young Pines, p. 116-120. U.S. Dep. Agric. For.

Serv., Southeast. Area, State and Private For. and

South. and Southeast. For. Exp. Stns., Alexandria,

La. and Charleston, S.C.

Balmer, W. E., E. G. Owens, and J. R. Jorgensen.

19’75. Effects of various spacings on loblolly pine

growth 15 years after planting. U.S. Dep. Agric.

For. Serv. Res. Note SE-211, 7 p. Southeast. For.

Exp. Stn. Asheville, N.C.

Campbell,‘T. E. and W. F. Mann, Jr.

19’74. Growth in a loblolly pine spacing study in

southwest Louisiana. In Proc. Sympos. on Mgrnt.

of Young Pines, p. 108-115. U.S. Dep. Agric. For.

Serv., Southeast. Area, State and Private For. and

South. and Southeast. For. Exp. Stns. Alexandria,

La. and Charleston, S.C.

Crow,, A. B.

1970. Prescribed burning in Lousiana pinelands. La.

State Univ. Coop. Ext. Pub. 1618. 17 p. Baton

Rouge, La.

Feduccia, D. and J. Mosier.

1977. The Woodworth spacing and thinning study:

an obituary. Forests 8z People 27(1):18-21.

Grosenbaugh, L. R.

1976. STX-FORTRAN-4 program for estimates of

tree populations from 3P sample-tree measurements. U.S. Dep. Agric. For. Serv. Res. Pap. PSW13, rev., 76 p. Pac. Southwest. For. and Range Exp.

Stn. Berkeley, Ca.

Haught, E.

1957. Distribution and extent of compression wood

in loblolly pine. In First Forest Tree Improvement

Progress Report. 14 p. N.C. State College School of

Forestry. Raleigh, N.C.

8
Husch, B., C. I. Miller, and T W. Beers.

1972. Forest mensuration, 2nd ed. Ronald Press,

New York, 410 p.

Mesavage, C. and J. W. Girard.

3946. Tables for estimating board-foot volume of

timber. U.S. Dep. Agric., Washington, D.C.

[Unnumbered Publ.] 94 p.

Shepard, R. F., Jr.

1974. An initial spacing study. In Proc. Sympos. on

Mgmt. of Young Pines, p. 121-128. U.S. Dep. Agric.

For. Serv., Southeast. Area, State and Private For.

and South. and Southeast. For. Exp. Stns., Alexandria, La. and Charleston, S.C.

U.S. Dep. Agric. For. Serv.

1976. Volume, yield, and stand tables for secondgrowth southern pines. U.S. Dep. Agric. Misc. Pub.

50, rev., 202 p., Washington, D.C.

Zobel, Bruce J. and Robert L. McElwee.

1958. Natural variations in wood specific gravity of

loblolly pjne, and an analysis of contributing factors. Tappi 41(4):158-161.

Conversion to Metric Units

1 inch =

1 foot =

1 acre * I

1 tree/acre =

1 square foot/acre =

1 cubic foot/acre =

1 cubic foot =

1 cunit =:

2.54 centimeters

0.3048 meter

0.4047 hectare

2.47 trees/hectare

0.2296 square meters/hectare

0.06997 cubic meters/hectare

0.0283 cubic meter

2.83 cubic meters of

peeled wood
j

BURTON, J. D.

1981. Sawtimber by prescription-the sudden sawlog story

through age 33. U.S. Dep. Agric. For. Serv. Res. Pap. SO-179,

9 p. South. For. Exp. Stn., New Orleans, La.

Presents total and net yield, standing volume, volume harvested, and natural mortality, in cubic feet i.b. to a S-inch top

d.i.b., and in board feet Int. % to an 8-inch and to a 6-inch top,

together with dbh distribution at various ages.

Additional keywords: Pinus taeda L., stand structure, diameter

distribution, stem form, stand density.

I I