U.S. Department of Agriculture

Forest Service

Research Paper SO-159

Growth and Yield in Managed Natural Stands of

Loblolly and Shortleaf Pine in the

West GuIf Coastal Plain

5. D. Burton
SUMMARY

Second-growth even-aged loblolly-shortleaf

pine stands on good and medium sites were

thinned from above or below to a basal area of 70

ft2, 85 ft 2, and 100 ft2 /acre, to an increasing basal

area, or according to the judgment of a committee.

Treatments began at age 20 for original plots and

at age 25 for supplementary plots (on good sites

only), which were thinned to a basal area of 55 ft2,

115 ft2, or 130 ft2/acre. Stands were thinned every

5 years.

At age 45, most trees in good-site original

plots and supplementary plots thinned from below

were in the lo-inch d.b.h. class and larger. In the

70-ft2, 85-ftk, and “increasing” treatments, most

stems were in the 15-inch class and larger.

On good-site original plots thinned from

below, at 45 years standing sawtimber volume for

trees 29.6 inches d.b.h. containing 2 one 16-ft

log to an 8-inch top was greatest in “increasing”

treatment plots and least in 85-ft2 and NOft2/acre plots. In supplementary plots, standing

board-foot volume was greatest in 130~ft2 and

least in 55-ft2/acre plots. On medium sites,

standing volume was greatest in “judgment” and

lOOft and least in 70 ft2/acre plots.

Sawtimber m.a.i. was still increasing rapidly

at age 45 in all treatments. Cubic-foot m.a.i. was

increasing slowly on medium sites but declining in

supplementary plots and in all good-site original

plots except the 70-ft” and “increasing” treatments. On good sites, p.a.g. in board feet

culminated between ages 30 and 35 in the 70-ft2

and 85.ft2 treatments and between ages 40 and 45

in “increasing” plots. On medium sites, p.a.g.

apparently was still increasing at 45 years. On

both sites, sawtimber ingrowth was much less

complete at age 45 in thin-from-above stands than

in those thinned from below.

On good sites, sawtimber yield to age 45 in

plots thinned from below was greatest in “increasing” treatment plots and least in lOOft2/acre stands. In supplementary plots,

sawtimber yield was greatest in 55-ft2 and least in

115~ft2 /acre treatments. On medium sites,

sawtimber yield was greatest in “judgment” and

lOOft and least in 70-ft2 /acre stands.

On good sites, cubic-foot yield to age 45, in

peeled stemwood to a 3-inch d.i.b., trees 2 3.6

inches d.b.h., in plots thinned from below, was

greatest for “increasing” treatment plots and

least for 70-ft2 stands. In supplementary plots,

cubic-foot yield was greatest for 130-ft2 and least

for 55-ft2 /acre plots. On medium sites, cubic-foot

yield was greatest for 100.ft2 and least for 70-

ft 2 /acre stands.

This study is a cooperative effort with the Crossett Division, Georgia-Pacific Corp. Plots are on

company land, and company personnel participated in periodic remeasurements and thinnings.

1980
Growth and Yield in Managed Natural Stands

of Loblolly and Shortleaf Pine in the

West Gulf Coastal Plain

J. D. Burton

INTRODUCTION

A thinning study in even-aged second-growth

loblolly-shortleaf pine (Pinus tee&z L. and P.

echinatu Mill.) stands is being conducted near

Crossett, Arkansas. This study has told us how

thinning method and stand density affect tree

size, standing volumes at different ages, growth

rates, and total yields on good and medium pine

sites in the West Gulf Coastal Plain. Results will

enable forest landowners to prescribe more

precisely thinning regimes consistent with

management objectives. This paper summarizes

results from age 20, when thinning was initiated,

through age 45. Growth and yields are reported in

cubic feet, board feet International %-inch rule,

and board feet Doyle rule.

METHODS AND MATERIALS

Two experimental areas were selected: an area

of good sites in Ashley County, Arkansas and an

area of medium sites in Morehouse Parish,

Louisiana. In winter 1949-50, twenty-seven O.lacre circular plots, each surrounded by a 33-footwide isolation zone, were established in each of

the two areas.

Site Quality

The good-site plots are on nearly level uplands.

Soils are mainly Grenada and Calloway silt loams.

Loblolly pine site index, determined before the

first thinning at age 20 and based on curves in

U.S. Department of Agriculture, Forest Service

(1976), averaged 90 ft at 50 years (table 1); individual plot means ranged from 85 ft to 100 ft.

Medium-site plots are on broad, low, islandlike ridges in the Ouachita River floodplain. These

ridges are flooded every 4 or 5 years. Soils are silt

loams in the Wrightsville-Leaf association with

some patches of Frizzell. Site index immediately

before initial thinning, based on curves in U.S.

Department of Agriculture, Forest Service (1976),

averaged 73 ft at 50 years; plot means ranged

from 69 ft to 79 ft.

Timber Type

Good-site plots were established in volunteer

shortleaf pine-loblolly pine-hardwood stands.

These stands originated after the virgin timber

was cut to a 12-&h d.b.h. limit during 1927

through 1930. This cut left two seed trees per acre.

Many hardwoods, some quite large but unmerchantable at that time, also were left standing.

About 1918, virgin timber on medium sites

was cut to a 14-inch d.b.h. limit. During the next

10 years, very hot wildfires burned the entire area

three times and killed many large residual trees.

The present stand grew from the 1929 seed crop,

and no charring was evident 20 years later when

the study began. No more cutting was done in

either area before 1949 when most residual pines

and hardwoods were still standing and had grown

very large. When study plots were laid out, these

old trees were avoided, so growth in the plots was

not suppressed by the overstory.

Because inventory procedures did not identify

species, relative proportions of shortleaf and

loblolly pine are unknown.

Stocking Before Initial Thinning

All these young stands were well stocked.

Before being thinned at age 20, good-site plots

had 892 pines/acre 23.6 inches d.b.h. (range 773

to 1,009 by plots), basal area of 140 ft2 /acre, and

mean d.b.h. (d.b.h. of tree of mean basal area) of

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

Pineville, Louisiana.
Table 1.-S&e index as determined before initial thinning and as determined at age 45 for plots

thinned from below

Site index at 50 years

Thinning Thinning

level method

Good sites

Initiala Age 4gb

Medium sites

Initiala Age 45’

ft 2/acre

70

85

loo

“Incr.”

“Judg.”

55

115

130

Above

Below

Above

Below

Above

Below

Above

Below

Both

Below

Below

Below

___________ ______. ___________________treeS per are _________.____________.------__.______

92 71

94 93 71 75

88 73 .

88 93 78 81

90 75 . . . .

88 ‘9;’ 73 80

89 73

89 93 73 81

96 95 73 80

95 96

93 95

91 95

a At age 20 in all original plots, at age 25 in 55 ft 2, 115 ft2, and 130 ft “/acre plots using curve in

b U.S. Department of Agriculture, Forest Service (1976).

Zahner’s (1962) curves for loessial soils were used.

’ Zahner’s (1962) curves for poorly aerated soils were used.

5.4 inches. Sixty-two percent of the cubic-foot

volume of stemwood inside bark to a 3-inch top

diameter inside bark (d.i.b.) was in the 6-inch

d.b.h. class and larger, 15 percent (22 trees/acre)

was in the &inch class and larger, and 1.2 percent

(4 trees/acre) was in the lo-inch class and larger.

And 1,162 pines/acre were 21.6 inches d.b.h., had

a basal area of 152 ft2 /acre, and had a mean d.b.h.

of 4.9 inches.

Before the first thinning at age 20 on medium

sites, 880 pines/acre were 2 3.6 inches d.b.h.

(range 823 to 950 by plots), had a basal area of 117

ft2/acre, and had a mean d.b.h. of 4.9 inches.

Forty percent of the cubic-foot volume to a 3-inch

top was in the g-inch d.b.h. class and larger; 4

percent of the volume (14 trees/acre) was in the 8-

inch class and larger. And 1,054 pines /acre were 2

1.6 inches d.b.h., had a basal area of 144 ft2, and

had a mean d.b.h. of 4.2 inches.

Mean total height of the dominant and

codominant 20-year-old pines was 46 ft on good

sites and 37 ft on medium sites.

Supplementary Plots

In winter 1954-55, nine more plots were laid

out on good sites next to the good-site plots

already established. Loblolly pine site index,

determined before thinning at age 25, based on

curves in U.S. Department of Agriculture, Forest

Service (1976), averaged 93 ft (table 1); plot

means ranged from 87 ft to 95 ft. These supplementary plots increased the range of stand

densities. Supplementary plots, still unthinned at

age 25, had 632 pines/acre, with basal area

averaging 171 ft2 /acre in trees 23.6 inches d.b.h.

(range 490 to 780 by plots) and with a mean d.b.h.

of 7.0 inches. Ninety-four percent of the cubic-foot

volume inside bark to a S-inch d.i.b. was in the 6.

inch class and larger; 67 percent of the volume (81

trees/acre) was in the &inch class and larger; and

24 percent (54 trees/acre) was in the lo-inch class

and larger. And 663 pines/acre were 21.6 inches

d.b.h. (range 490 to 830 by plots), had a basal area

of 172 ft2/acre, and had a mean d.b.h. of 6.9 inches .

Hardwood Control

In every plot, hardwoods 23.6 inches d.b.h.

were cut when plots were first thinned. All

remaining hardwoods were killed with a weedkilling chemical. In 1959, all hardwood sprouts 2

1.0 inch in diameter at the root collar were killed

by an injection of a weedkiller. On good-site plots,

original and supplementary, a dense, vigorous

2
understory of hardwood sprouts, shrubs, and

vines developed after each thinning. On medium

sites, the understory was feeble. In every goodsite plot, original and supplementary, all hardwoods 2 1.0 inch at root collar were cut before

every inventory through age 40.

Plot Establishment and Treatments

Nine treatments were randomly replicated

three times on both good and medium sites:

Thinning initially from above to a basal area

of 70 ft? ,85 ft2, or 100 ft2 /acre at ages 20 and

25; thinnings at 30, 35, 40, and 45 years were

from below, always to the originally assigned

density in each plot.

Thinning initially from above to a basal area

of 70 ft2/acre at age 20, increasing to 75

ft 2 /acre at age 25, then thinning from below to

80 ft2 at age 30, to 85 ft’ at age 35, to 90 ft2 at

age 40, and to 95 ft2 at age 45.

Thinning from below to a basal area of 70 ftz,

85 ft2, or 100 ft2 /acre at age 20 and at 5-year

intervals to the same densities.

Thinning from below to a basal area of 70

ft2/acre at age 20, increasing to 75 ft2 at age

25, to 80 ft2 at 30 years, to 85 ft2 at 35 years, to

90 ft2 at 40 years, and to 95 ft’ at 45 years.

Thinning according to the consensus of

participating personnel, with no restrictions on

method or intensity; this was called the

“judgment” treatment. The basal area left

after each thinning varied considerably between thinnings and between plots within

thinnings. Basal area ranged by plot from 67

ft2 to 81 ft2/acre and averaged about 75

ft2 /acre on both sites. “Judgment” thinning

was partly from above but mostly from below.

No unthinned control treatment was

established.

For all thinning treatments, if trees were of

equal quality, field workers cut shortleaf and kept

loblolly pines. Reasonably uniform spacing

between trees was maintained.

Thinning from above favored well-formed,

relatively smooth codominant and intermediate

trees by removing most dominants. Those suppressed merchantable trees apt to die within 5

years were cut, as were defective and poorly

formed trees, regardless of crown class.

In thinning from below, dominants were

favored, and competing trees in other crown

classes were removed. Where removing coarselimbed or misshapen dominants was desirable,

codominants were left.

Supplementary plots were thinned from below

to a basal area of 55 ft2, 115 ft2, or 130 ft* /acre

and at 5-year intervals to the same residual

densities.

Since thinning from above at ages 20 and 25

removed the most vigorous trees, average total

height of the 50 tallest trees/acre, from age 35

onward, was noticeably less in thin-from-above

plots than in thin-from-below plots: this difference

averaged 3 feet on both sites, although it varied

among inventories, and it usually was greater on

good sites than on medium. Researchers determined 50-year site index at age 45 only for plots

thinned from below, using Zahner’s (1962) curves

for loessial soil in good-site original and supplementary plots and his curves for poorly aerated

soils for medium-site plots. The age-45 site index

determinations (all treatments averaged) exceeded the age-20 and age-25 values by 3 ft on

good-site original plots, 6 ft on medium sites, and

4 ft on supplementary plots.

Changing attitudes on how to treat basal area

in submerchantable trees (trees 1.6 -3.5 inches

d.b.h.) resulted in varying thinning procedures till

age 30. When the original plots were first thinned,

researchers included only merchantable pine trees

in computing basal area and in selecting trees to

cut. Most plots contained many submerchantable

trees; their numbers varied widely between plots

within treatments; so, plots treated alike were not

alike in density, stand structure, and competition

intensity. Thinning at age 25 again removed only

merchantable stems, but the designated residual

basal area included submerchantable trees. So,

residual basal area in 3.6~inch and larger trees

averaged 7 ft2/acre less than prescribed stand

densities, but the deficit was as much as 21

ft2 /acre on individual plots. All submerchantable

stems were cut at age 30. After age 30, residual

stands consisted entirely of trees 3.6 inches d.b.h.

and larger.

Violent winds destroyed or damaged many

trees on good sites during the 41st growing

season. Distribution and severity of damage were

related to the storm track and were not caused by

thinning. During the next 4 years, many trees on

good sites and a few on medium sites were killed

by the southern pine beetle (Dendroctonus

frontalis Zimm.). Beetle-caused mortality was not

related to site quality, but was more severe on

lightly thinned than on heavily thinned plots.

3
Measurements and Analysis

The 54 original and 9 supplementary plots,

from 1954 onward, were inventoried and thinned

as one study. Merchantable height to an

estimated 3-inch top d.i.b. was measured with a

handheld altimeter. And d.b.h. was measured

with a diameter tape on every tree. Total height

was measured on sample trees. Using ladders,

diameter tapes, and Swedish bark gages, field

workers collected data for Girard form class.

Board-foot volumes (Doyle and Int. 1/) were

obtained from the form-class volume tables of

Mesavage and Girard (1946). Board-foot volumes

were determined for trees 2 9.6 inches d.b.h.

containing at least one 16-ft log to a top diameter

outside bark (d.o.b.) of about 8 inches. Cubic-foot

volume of pulpwood inside bark to a 3-inch top

d.i.b. in trees 23.6 inches d.b.h. was reckoned

from Mesavage’s (1947) tables.

In this paper, standing volume means cubicfoot or board-foot volume of stemwood per acre in

living pine trees before thinning at any specified

age. Total yield to any age consists of standing

volume plus volume in all previous merchantable

thinnings plus volume in natural mortality occurring in merchantable trees after age 30. Net

yield at any age includes standing volume plus

volume in merchantable thinnings. The difference

between total yield and net yield is natural

mortality. No record was made of mortality before

age 30, but it probably was confined almost entirely to submerchantable trees.

Because of a large spread in standing volume

amounts before initial thinning, I had to calculate

an adjusted initial cut before computing later

cubic-foot yields. In good-site original plots,

standing volume at age 20 ranged from 1,269 ft3

to 2,000 ft3 and averaged 1,471 ft3/acre; on

medium sites, standing volume ranged from 810

ft3 to 1,572 ft3 and averaged 1,261 ft3/acre; in

supplementary plots .at age 25, standing volume

ranged from 2,580 ft: to 3,967 ft 3 and averaged

3,246 ft3 /acre. Average merchantable yield before

initial thinning was calculated for each of the

three groups of plots: good-site original, mediumsite, and supplementary. Adjusted initial cut for

each plot was: the group pre-thinning average

minus the individual plot residual

volume.

No adjustment was needed for

yield.

Using analysis of variance, I

treatment-associated differences in:

cubic-foot

board-foot

evaluated

1.

2.

3.

4.

5.

6.

Adjusted cubic-foot yield to ages 25 through

45,

Unadjusted standing cubic-foot volume at

ages 25 through 45,

Unadjusted board-foot yield at ages 30

through 45,

Unadjusted standing board-foot volume at

ages 30 through 45,

Adjusted periodic annual cubic-foot volume

growth by 5-year periods from age 20

through age 45, and

Adjusted mean annual cubic-foot volume

growthtoages25,30,35,40,and45.

_ __ Separate analyses were made of data from

good-site original plots, medium-site plots, and

supplementary plots. Level of significance was

0.05. Singledf comparisons were orthogonal.

RESULTS

Thinning method caused few differences in

relationships among treatments. And, because

most commercial, non-mechanical thinning of

natural stands of southern pines is done mainly

from below, I will refer to thin-from-above

treatments only when their results are

significantly different.

Diameter Growth and Diameter Distribution

Bole diameter growth in good-site original

plots from age 20 to age 45 was most rapid in the

70-fP/acre plots, slowest in the lOO-ft2 (fig. 1).

Mean d.b.h. in the “increasing” treatment was

almost the same as mean d.b.h. in the 70.ft’

treatment till age 30. Then, “increasing” residual

basal area was 80 ft2 /acre; thereafter the “increasing” matched the 85-ft2 plots’ mean d.b.h.

At age 40 in “increasing” plots, residual basal

area was 90 ft2 /acre, so the 85-ft 2 curve soon rose

above the curve for the “increasing” treatment.

And although standing basal area at age 45 was

about the same for the 100 ft2 treatment and the

“increasing” treatment, mean d.b.h. was much

larger for the “increasing” treatment (14.6 inches)

than for the lOO-ft2 treatment (12.5 inches).

Mean d.b.h. in good-site supplemental plots

was greatest in heavily thinned plots, least in

lightly thinned plots from age 35 onward. At age

40, before thinning, mean d.b.h. was 15.4 inches in

the 55-ft2, 12.4 in the 115.ft2, and 11.9 inches in

the 130~ft2 treatment (fig. 2).
-INCR

. . . . . . . 85

--- 100

-___ 70

OOL

I I I I I I I

20 2 5 3 0 3 5 4 0 4 5

AGE OF STAND (YEARS)

Figure l.-Mean d.b.h. by treatment in stands thinned from

below on good sites, based on all surviving pine

trees L 3.6 inches d.b.h. at each inventory.

, -

Laj4 -

i

I

---- 55

-II5

. . . . . . . ,3(J

oi ’ I 1 I I 1

0 2 0 2 5 3 0 3 5 4 0 4 5

AGE OF STAND (YEARS)

Figure 2.-Mean d.b.h. in supplementary plots, based on all

surviving pine trees 2 3.6 inches d.b.h. at each

inventory.

14

i

12 -

IO -

4 -

INC.7

85

100

1

OL ’

I I I 1 I I

0 2 0 25

AGE

0F3:TAND $ARS, 4 0 4 5

Figure 3.-Mean d.b.h. by treatment in stands thinned from

below on medium sites, based on all surviving pine

trees L 3.6 inches d.b.h. at each inventory.

6
Mean d.b.h. on the medium sites responded

only weakly and very slowly to thinning levels

(fig. 3).

Table 2 shows diameter distribution on good

sites after thinning at age 20. Tables 3-7 show

diameter distribution on good sites (original plots

and supplementary plots) before thinning at ages

25, 30, 35, 40, and 45.

Just after initial thinning at age 20, 76 to 97

percent of the merchantable trees were in three

d.b.h. classes. At age 25 before thinning, the

majority (85 to 98 percent) had spread through

five (4. through 8-inch) classes. At age 30, merchantable trees were distributed through a wide

range of d.b.h. classes. Light thinning widened

the range of classes more than did heavy thinning.

Thinning from above widened the range more

than thmning from below. At age 35, all trees in

the 70 ft and 89 percent in the “increasing” thinfrom-below plots were in the lo-inch class and

larger.

Table 8 shows diameter distribution on

medium sites after thinning at age 20. Tables 9-13

show diameter distribution on medium sites

before thinning at ages 25,30,35,40, and 45.

After the first thinning at age 20, most (70 to

87 percent) of the merchantable trees on medium

sites were in two d.b.h. classes. The range of

classes began to expand immediately and continued to increase through age 45.

Cubic-foot Growth and Yield

Standing Volumes. -Standing volumes before

each thinning represent the resource available for

immediate liquidation if the rotation were to be

ended at that age. Except where catastrophic

losses occurred, standing cubic-foot volumes in

this study increased with age and were greater in

lightly thinned than on heavily thinned plots. The

result from thinning from above was usually not

much different from the result from thinning from

below. Differences among the 70-ft*, 85-ft? , and

lOO-ft? thinning levels were significant at every

inventory from age 25 onward on medium sites

and from age 30 onward on good sites. Differences

between the 55-ft2 and the 115~ft2 and 130-ft2

combined were significant at every inventory from

age 30 onward. There were no significant differences between the 115-ft2 and the 130-ft*

treatments.

Tables 14-18 show distribution of standing

cubic-foot volume on good-site original plots and

supplementary plots. On original plots at age 25,4

to 18 percent (average 11 percent) of standing

cubic-foot volume was in lo-inch and larger trees;

in supplementary plots, which were still unthinned at age 25, 19 to 29 percent (average 24

percent) of standing cubic-foot volume was in

sawtimber-sized trees (table 14).

Tables 19-23 show distribution of standing

cubic-foot volume on medium-site plots. At every

inventory, from age 25 through age 45, standing

cubic-foot volume increased as stand density

increased; among the 70-ft?, 85-ft2, and lOOft

levels this effect was significant. Only at age 30

was any difference associated with thinning from

above or below-thin-from-below plots contained

significantly more volume than did thin-fromabove plots.

Total Yields. -Yield in cubic feet of stemwood

inside bark to a 3-inch top d.i.b. was greatest

under the lightest thinnings, least under the

heaviest thinnings. These effects were significant

at ages 35 and 40 on good-site original plots and at

ages 25 through 45 on medium sites; on supplementary plots, these differences were not

significant.

Total yield to age 30 averaged 3,593 ft3 /acre

on good-site original plots, 2,536 ft 3 /acre on

medium sites, and 3,992 ft 3/acre on supplementary plots. Yield to age 40 averaged 5,935

ft3 /acre on good-site original, 4,736 ft3/acre on

medium-site, and 6,411 ft3 /acre on supplementary

plots.

Net yield was equal to total yield through age

45 in the good-site 70-ft* plots; no trees died after

age 30 (fig. 4). Nor did any mortality occur after

age 30 in 55-ft2 plots; in all other thin-from-below

treatments on good-site original and supplementary plots, some trees died. On medium

sites, mortality was light and showed little effect

of treatment.

The greatest total adjusted 45-year yields in

good-site original plots thinned from below were

in “increasing” plots (6,949 ft3 /acre) and 100 ft’

plots (6,666 ft3 /acre). Net yield was 6,186 ft3 /acre

in 100 ft2 plots and 6,416 ft3/acre in 70 ft2 plots.

Greatest total yields in supplementary plots

occurred in 130~ft2 (7,442 ft3/acre) and 115-ft2

(7,156 ft3/acre) treatments at 45 years. Greatest

net cubic-foot yields were in 55-ft2 (6,608 ft3 /acre)

and 130 ft2 (6,468 ft3/acre) plots.

Greatest total yield (6,089 ft3/acre) and net

yield (6,049 ft /acre) at age 45 on medium sites

resulted from thinning from below to a basal area

of 100 ft* (fig. 5). Net yields from 85 ft2 and

“increasing” stand densities were slightly less,

6
Table 2.-Diameter distribution of trees per acre on good sites after thinning at age 20

Thinning Thinning

level method

D.b.h. (inches) Total

28~3 4 5 6 7 8 9 10 1 4 2 2

ft ‘/acre

70

85

100

“Incr.”

“Judg.”

Above 127 120 130 83 43 27 10 0 413 540

Below 340 117 123 117 43 23 3 0 426 766

Above 270 223 187 103 50 17 0 0 580 850

Below 200 113 150 107 80 27 7 3 487 687

Above 103 147 200 147 80 20 3 0 597 700

Below 280 227 210 133 63 17 0 3 653 933

Above 480 267 213 70 17 0 0 0 567 1047

Below 300 100 90 113 60 23 0 7 393 693

Both 327 163 147 97 57 27 0 0 490 817

_______________ _____________ trees per acre___ .______________ ____ ______

Table 3.-Diameter distribution of trees per acre on good sites before thinning at age 25

Thinning Thinning D.b.h. (inches) Total

level method 2&3 4 5 6 7 8 9 10 11 12 13 2 4 2 2

ft 2/acre

70

85

100

“Incr.”

“Judg.”

55

115

130

Above

Below

Above

Below

Above

Above

Below

Both

Below

Below

Below

20 60 70

147 73 80

142 117 167

104 73 80

31 83 133

106 167 150

204 200 130

67 60 60

147 100 80

47 97 120

18 70 93

28 67 123

_ _ _____ ___, . __ __ ___. ~------trees per

100 70

113 80

120 97

114 90

107 103

147 107

173 63

93 63

107 93

153 80

123 90

113 130

____________________________

40 27 13 13 0 0 393 413

60 27 10 3 0 0 446 593

50 30 7 0 0 0 588 730

47 53 13 3 3 0 476 580

73 33 10 3 0 0 545 576

57 23 3 0 3 0 657 763

33 10 0 0 0 0 609 813

77 30 20 0 3 0 406 473

60 33 7 0 0 0 480 627

80 67 17 23 3 3 643 690

83 77 40 23 0 3 602 620

80 93 30 3 10 3 652 680

Table I.-Diameter distribution of trees per acre on good sites before thinning at age 30

Thinning Thinning D.b.h. (inches) Total

level method 28~3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 4 2 2

ft 2/acre ________________________________________._trees per are ___________----------________.----------

70

85

100

“Incr.”

“Judg.”

55

115

130

Above 9 13 40 37 33 70 37 27 17 10 0 7 3 0 294 303

Below 56 53 10 17 17 37 60 30 30 10 3 3 0 0 270 326

Above 37 83 50 87 70 53 57 30 13 7 3 0 0 0 453 490

Below 27 37 37 17 33 43 27 53 40 10 3 3 0 0 303 330

Above 7 43 70 77 53 80 63 37 13 10 3 0 0 0 449 456

Below 40 73 70 63 87 63 67 40 7 10 0 0 0 0 480 520

Above 100 100 63 60 83 60 33 17 10 0 0 0 0 0 426 526

Below 30 40 7 27 30 37 43 53 23 17 0 0 3 0 280 310

Both 66 80 23 27 50 47 43 53 17 7 0 0 0 0 347 413

Below 1710 0 7 7 13 23 30 20 17 20 3 0 3 153 170

Below 6 7 7 37 33 30 50 63 30 27 13 0 3 0 300 306

Below 13 3 17 53 67 47 57 77 20 10 13 3 0 0 367 380

7
Table S.-Diameter distribution of trees per acre on good sites before thinning at age35

Thinning Thinning D.b.h. (inches)

level method 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Total

5-18

ft 2/acre

70

85

100

“Incr.”

“Judg.”

55

115

130

Above 00 0 7 40 17 33 7 10 13 0 3 3 3 136

Below 00 0 0 0 10 37 20 23 13 7 3 0 0 113

Above 0 3 7 43 30 40 23 20 13 3 7 0 0 0 189

Below 00 3 3 27 10 43 47 13 3 7 0 0 0 156

Above 0 0 13 40 47 57 33 20 13 3 0 0 0 0 226

Below 3 7 43 30 60 40 40 10 13 0 0 0 0 0 246

Above 7 20 43 40 73 33 17 7 10 0 0 0 0 0 250

Below 00 3 0 13 40 33 30 20 10 0 0 0 0 149

Both 00 3 7 20 27 30 33 10 7 3 0 0 0 140

Below 00 0 0 0 3 13 20 10 20 10 7 0 0 83

Below 0 0 10 6 17 37 50 20 37 10 7 3 0 0 197

Below 0 3 23 33 47 30 63 17 13 10 0 7 3 0 249

___---- _____.. trees per acre --_____----_ -- ~~~~~~~~~~~__ _ ____-----____

Table 6.-Diameter distribution of trees per acre on good sites before thinning at age 40

D.b.h. (inches) Total

Thinning Thinning

):veI method 7 8 9 10 11 12 13 14 15 16 17 18 19 20 7-20

ft Vacre __.__ ______---___ _ _~~~~~~~__~~~~~~~~_-~~~ trees per acre- ___________ ______ ______ _________________

70 Above

85

100

“Incr.”

“Judg.”

55

115

130

Above

Below

Above

Below

Above

Below

Both

Below

Below

Below

03 0 3 20 17 20 7 7 7 0 7 0 3 94

00 0 0 3 13 13 23 17 7 7 0 0 0 83

0 13 13 23 20 20 23 20 3 0 7 0 0 0 132

0 0 7 10 17 20 27 30 7 3 0 0 0 0 121

0 17 7 23 47 27 10 23 3 7 0 0 0 0 164

13 13 17 53 27 27 17 3 13 0 0 0 0 0 183

13 7 27 47 43 20 3 10 7 0 0 0 0 0 177

00 0 7 33 10 27 13 27 0 0 0 0 0 117

0 3 0 17 3 27 23 13 10 7 3 0 0 0 106

00 0 0 0 3 13 10 7 7 3 13 0 0 56

7 7 7 20 17 30 23 30 10 3 7 0 0 0 161

10 7 30 27 20 40 27 13 7 3 7 0 3 0 194

Table ‘I.-Diameter distribution of trees per acre on good sites before thinning at age 45

Thinning Thinning D.b.h. (inches) Total

level method 9 10 11 12 13 14 15 16 17 18 19 20 22 9-22

ft 2/acre

70

85

100

“Judg.”

55

115

130

Above

Below

Above

Below

Above

Below

Above

Below

Both

Below

Below

Below

______ _ ~~_______~~~~.____~~~~~~~~____ trees per acre__.__________________________________

0 0 0 3 3 27 3 10 0 0 7 7 3

0 0 0 0 3 13 7 20 10 7 3 0 0

0 0 13 13 20 13 17 10 0 3 3 0 0

0 0 0 0 3 7 13 23 0 3 0 0 0

0 7 3 20 26 10 17 7 7 3 0 0 0

7 7 37 27 10 10 13 7 3 0 0 0 0

0 13 20 33 20 10 3 10 3 0 0 0 0

0 0 0 20 7 17 17 23 7 0 0 0 0

0 3 3 0 17 17 13 10 10 3 7 0 0

0000000777 7 10 0

0 0 0 7 13 10 20 17 3 7 0 0 0

7 10 7 17 33 17 17 0 7 3 0 3 0

63

63

92

49

100

121

112

91

83

38

77

121

8
Table 8.-Diameter distribution of trees per acre on medium sites after thinning at age 20

Thinning

level

Thinning

D.b.h. (inches) Total

method 2&3 4 5 6 7 8 9 2 4 2 2

ft z/acre

70

85

100

“Incr.”

“Judg.”

Above

Below

Above

Below

Above

Below

Above

Below

Both

______________________________trees per acre_ .___ __ ______ * _____._____.--__

363 230 183 70 23 13 0 519

733 300 210 67 7 3 0 587

603 360 200 83 20 3 3 669

120 280 197 113 23 10 0 623

427 270 203 133 60 10 3 679

670 383 24’7 107 30 7 0 774

903 410 130 50 20 0 0 610

433 180 220 83 23 13 0 519

763 283 177 60 13 3 3 539

882

1,320

1,272

1,343

1,106

1,444

1,513

952

1.302

Table Q.-Diameter distribution of trees per acre on medium sites before thinning at age25

D.b.h. (inches) Total

Thinning Thinning

level method 2&3 4 5 6 7 8 9 10 12 2 4 2 2

ft Vacre

70

85

100

“Incr.”

“Judg.”

Above

Below

Above

Below

Above

Below

Above

Below

Both

___ ____ ___ ______.______ _______t~es per acre __.________,__.___.______-____-----.

157 183 187 137 70 20 13 0 0 610 767

424 243 207 153 57 13 3 0 0 676 1.100

301 250 210 157 87 20 10 3 3 740 1,047

351 263 173 127 83 17 13 3 0 679 1,030

202 217 187 173 77 43 11 7 0 721 923

330 280 240 187 103 23 7 0 0 840 1,170

517 403 183 100 40 21 3 0 0 756 1,273

206 173 123 147 87 30 17 0 0 577 783

443 233 187 153 63 17 0 7 0 660 1,103

Table lO.-Diameter distribution of trees per acre on medium sites before thinning at age 30

Thinning Thinning

D.b.h. (inches) Total

level method 28~3 4 5 6 7 8 9 10 11 12 24 2 2

ft 2/acre __-.___,

70

85

100

“Incr.”

I1 Judg.”

Above 75

Below 227

Above 127

Below 190

Above 73

Below 156

Above 251

Below 84

Both 242

83 87

110 33

120 93

97 73

87 127

87 70

130 153

67 30

127 60

___._-._ trees per acre-_.- _____ __ ______ __ ______ __ ___._ ____

81 107 47 20 10 0 0 441 516

60 70 73 33 7 3 0 389 616

107 93 47 33 10 0 0 SO3 630

Q O 83 63 17 17 3 ‘7 460 640

93 103 60 43 7 7 0 527 600

117 97 100 43 10 0 0 524 680

Q O 53 23 17 13 0 0 479 730

63 73 IO 43 13 I 0 366 450

107 QO 67 30 17 0 3 501 743

9
Table Il.-Diameter distribution of trees per acre on medium $tes before thinning at age 35

D.b.h. (inches) Total

Thinning Thinning

level method 4 5 6 7 8 9 10 11 12 13 15 4-15

ft Vacre ________________-._.-________.__--------- trees per ~rs__._________________-____________________

70

85

100

“Incr.”

“Judg.”

Above 0 0 17 60 80 33 43 0 10 0 0 243

Below 53 10 7 27 53 70 23 17 3 3 0 266

Above 0 17 33 77 80 43 37 23 0 0 0 310

Below 7 20 40 43 57 63 37 7 10 7 3 294

Above 3 47 57 83 77 50 40 7 33 0 370

Below 0 0 30 70 73 80 43 23 0 0 0 319

Above 50 53 103 70 57 17 30 10 3 0 0 393

Below 0 0 7 47 47 63 47 13 13 0 0 237

Both 0 0 17 57 60 63 43 10 13 3 0 256

Table 12.-Diameter distribution of trees per acre on medium sites before thinning at age 40

Tbinkig Thinning D.b.h. (inches) Total

level

ft 2/acre

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

________...___________________.----trees per (Ic~e’e---------------------------------

70

85

100

“Incr.”

“Judg.”

Above 0 0 7 23 63 30 27 10 10 0 0 0 170

Below 0 0 3 27 23 53 17 13 13 3 3 0 155

Above 0 17 7 47 50 33 23 27 13 0 0 0 217

Below 3 3 10 20 47 50 27 7 13 3 3 3 189

Above 3 27 30 50 40 53 27 17 7 3 0 0 257

Below 0 0 10 37 43 63 27 37 10 0 0 0 227

Above 10 13 50 63 50 23 13 27 0 3 0 0 252

Below 0 0 10 30 27 43 37 17 17 3 0 0 184

Both 0 0 0 13 23 30 48 20 13 3 3 0 153

Table 13.-Diameter distribution of treesper acre on medium sites before thinning at age 45

Thhming Thinning

level method

D.b.h. (inches) Total

6 7 8 9 10 11 12 13 14 15 16 17 18 6-18

ft 2/acre

70

85

100

“Incr.”

“Judg.”

Above

Below

Above

Below

Above

Below

Above

Below

Both

0 0 0 7 37

0 0 0 7 3

0 0 13 30 20

0 0 7 7 23

0 3 27 27 30

0 0 0 3 20

3 7 27 33 54

0 0 3 7 13

0 0 0 3 0

23 23 17 10

27 23 13 13

13 20 17 27

27 37 10 10

37 30 20 10

57 30 27 17

20 7 20 13

37 27 33 10

17 30 33 10

3 3 0 0 123

10 7 0 0 103

7 0 0 0 147

3 3 3 3 133

0 3 0 0 187

7 0 0 0 161

0 0 0 0 184

10 0 0 0 140

10 7 0 0 110

10
Table 14.-Distribution of standing cubic-foot volume at age 25 among d. b. h. classes on good-site

original plots thinned from below and on supplementary plots

Proportion of standing volume

Thinning in trees having d.b.h. in inches 2:

Total

treatment 4 6 8 10 12 volume

ft 2/acre

70

85

100

“Incr.”

“Judg.”

55

115

130

________________________-_________-percent________________________________________

100 90 50 10 0

100 92 54 12 3

100 82 34 5 3

100 93 59 15 3

100 89 44 4 0

100 93 65 23 4

100 95 71 29 2

100 94 65 19 7

ft s/acre

1,905

2,173

2,129

1,918

1,918

3,037

3,262

3,438

Table 15.-Distribution of standing cubic-foot volume at age 30 among d. b. h. classes on good-site

original plots thinned from below and on supplementary plots

Proportion of standing volume

Thinning

treatment 4

in trees having d.b.h. m-inches 2: Total

6 8 10 12 14 16 volume

ft 2/acre

70

85

100

“Incr.”

“Judg.”

55

115

130

100 98 92

100 97 89

100 95 72

100 99 90

100 96 82

100 100 98

100 100 92

100 99 85

,______ percent -----. ,_-.-__________.____--.-.-.-----. .___

53 18 5 0

65 15 4 0

29 8 0 0

62 20 5 0

47 6 0 0

84 51 11 7

70 31 4 0

59 21 3 0

ft Vacre

2,167

2,466

2,544

2,338

2,206

2,146

3,083

3,325

Table 16.-Distribution of standing cubic-foot volume at age 35 among d. b. h. classes on good-site

originalplots thinned from below and on supplementary plots

Thinning

treatment

Proportion of standing volume

in trees having d.b.h. in inches 2: Total

4 6 8 10 12 14 16 volume

p Vacre

70

85

100

“Incr.”

“Judg.”

55

115

130

________

100

100

100

100

100

100

100

100

.________._________.

100

100

100

100

100

100

100

100

100

99

90

99

99

100

99

96

.-percent-----.

100

87

58

93

86

100

92

75

62 19

57 11

18 0

52 10

49 12

87 52

56 21

37 19

._____

5

0

0

0

0

12

4

11

ft 3/acre

2,637

3,178

3,350

3,039

2,681

2,443

3,763

3,996

11
Table 17.-Distribution of standing cubic-foot volume at age 40 among d.b.h. classes on good-site

original plots thinned from below and on supplementary plots

Proportion of standing volume

ThhmilW

in trees having d.b.h. in inches 2:

Total

treatment 4 6 8 10 12 14 16 18 volume

ft 2/acre

70

85

100

“Incr.”

“Judg.”

55

115

_______---___ ___.___._________ percent----

100 100 100 100 97

100 100 100 97 79

100 100 97 87 48

100 100 100 100 78

100 100 100 99 88

100 100 100 100 100

100 100 99 95 78

-__--1-_-1---

72 22 0

44 5 0

17 0 0

46 0 0

40 17 0

86 53 33

44 12 0

ft 3/acre

3,176

3,561

3,848

3,656

3,370

2,632

4,511

130 100 100 98 88 69 31 16 5 4,986

Table 18.-Distribution of standing cubic-foot volume at age 45 among d. 6. h. classes on good-site

originalplots thinned from below and on supplementary plots

Thinning

treatment

Proportion of standing volume

in trees having d.b.h. in inches L:

Total

8 10 12 1 4 1 6 18 20 volume

ft 2/acre

70

85

100

“Incr.”

“Judg.”

55

115

_ ________________________________-_--_________ percent ------ ~~~~~~~-~~..._________________________ ft s/acre

100 100 100 97 71 2 1 0 3,271

100 100 100 96 59 9 0 2,310

100 98 66 37 14 0 0 3,408

100 100 100 80 4 2 0 0 3,921

100 100 96 81 47 1 8 0 3,787

100 100 100 100 100 71 33 2,493

100 100 100 8 1 44 7 0 3,349

130 100 98 90 53 2 1 12 7 4,443

Table lg.-Distribution of standing cubic-foot volume at age 25 among d. b.h. classes on mediumsite olots thinned from below

Thinning

treatment

ft 2/acre

70

85

100

“Incr.”

“Judg.”

Proportion of standing volume

in trees having d.b.h. in inches 2:

4 6 8 1 0

_____ ______________._______________ percent _______________.__-------- -.-------

100 62 8 0

100 69 18 2

100 68 11 0

100 79 23 0

100 69 1 4 6

Total

volume

ft 3/acre

1,301

1,487

1,861

1,456

1,346

12
Table 20.-Distribution of standing cubic-foot volume at age 30 among d. b.h. classes on mediumsite plots thinned from below

Proportion of etanding volume

Thinning

treatment 4

in treea having d.b.h. in inches 2:

6 8 10

Total

12 volume

ft vacre

70

85

100

“Incr.”

“Judg.”

________________________________________ percent ____.________________________._._ _______

100 92 58 8 0

100 89 51 20 7

100 92 66 6 0

100 96 66 16 0

100 90 60 13 4

p Vacre

1,291

1,667

2,013

1,650

1,612

Table 21 .-Distribution of standing cubic-foot volume at age 35 among d. b.h. classes on mediumsite plots thinned from below

Proportion of standing volume

Thinning in trees having d.b.h. in inches 2:

treatment 4 6 8 10 12 14

fwacre __ _____ ____ _____._______________ __-_-___pe~~n~ .____.__._______________________________-

70 100 97 88 33 6 0

85 100 99 84 40 17 4

100 100 83 32 0 0 0

“Incr.” 100 100 87 45 10 0

“Judg.” 100 100 83 41 13 0

Total

volume

ft ‘/acre

2,024

2,560

2,834

2,402

2,430

Table 22.-Distribution of standing cubic-foot volume at age 40 among d. b.h. classes on mediumsite plots thinned from below

Thinning

treatment 4

Proportion of standing volume

in trees having d.b.h. in inchea_k:

Total

6 8 10 12 14 16 volume

ft 2/acre --_.-__..-.__.__.__________________________ percent _________________________________________. ft 3/acre

70 100 100 99 79 35 8 0 2,549

85 100 100 98 74 31 14 6 3,148

100 100 100 98 73 33 0 0 3,549

“Incr.” 100 100 98 78 31 3 0 3,111

“Judg.” 100 100 100 85 33 4 0 2,857

13
Table 23.-Distribution of standing cubic-foot volume at age 45 among d. b.h. classes on mediumsite plots thinned from below

Proportion of standing volume

Thinning

treatment

ft Vacre

70

85

100

“Incr.”

“Judg.”

in trees having d.b.h. in inches 2:

4 6 8 1 0 1 2 14 1 6 1 8

_________. ____ .___ _ ___________ ___.__ ________ percent _.------- __--- _-------------.. ---_ ------

100 100 100 97 76 42 10 0

100 100 100 95 69 3 3 1 7 7

100 100 100 99 6 1 21 0 0

100 100 100 96 69 2 3 0 0

100 100 100 99 90 34 6 0

Total

volume

ft a/acre

2,612

3,238

3,742

3,328

3,005

and yield from 70 ft2 was noticeably less; all these

differences were significant.

Andrulot et al. (1972) reported yields through

age 50 of plots established by H. H. Chapman

near Urania, Louisiana. Many differences exist

between the two studies, but comparisons can be

useful. In the tabulation below, the Urania

study’s net yields (including thinnings, excluding

mortality) in total stands (including hardwood)

and in pine only are arrayed with yields of the 70-

ft2, lOO-ft2, and “increasing” treatments in the

Crossett study.

Age of

stand

25

30

35

40

46

Urania study Crossett study

Total Pine Thinned from below to:

stand only 7Oft2 100 fi2 “Incr.”

______________________________ft3/acre__ .______ * ___. __ _________.__.

2,652 2,482 2,664 2,654 2,709

3,439 3,251 3,492 3,581 3,641

4.208 4,009 4,615 4,901 4,909

4,901 4,696 5,657 6,000 6,081

5,460 5,251 6,416 6,666 6,949

So, total yields to a 3-inch top in the Crossett

study were very similar to net yields of total

stemwood in the Urania study. Crossett yields

were a little larger than Urania yields, in part

because Crossett plots were kept free of hardwood, in part because site index at Crossett was

higher than the 88.foot average site index at

Urania, and in part because early thinnings at

Urania were more drastic than those at Crossett.

Periodic Annual Increment. -Periodic annual

growth (p.a.g.) in cubic feet to a 3-inch top

culminated between ages 30 and 35 in the goodsite original plots and between ages 35 and 40 on

medium sites. In supplementary plots, p.a.g.

culminated between ‘ages 30 and 35 in 55-ft2 plots

and between ages 35 and 40 in 115-ft2 plots and

13OW plots (table 24).

Periodic annual growth, age 20 to 45, on goodsite original plots thinned from below averaged

195 ft3/acre (range 187 ft3 to 208 ft3/acre by

treatments); on medium sites p.a.g. averaged 168

ft3/acre (range 148 ft3 to 193 ft3/acre), though it

declined suddenly for no apparent reason in the

lOOft plots between 40 and 45 years. Periodic

annual growth, age 25 to 45 in supplementary

plots averaged 191 ft3/acre for all treatments

combined (range 168 ft3 to 210 ft”/acre).

The p.a.g. values in table 24 appear similar to

those reported by Nelson et al. (1961) for a study

in Georgia, South Carolina, and Virginia. But

results of the two studies are not comparable for

several reasons:

1.

2.

3.

4.

5.

6.

Cubic-foot volumes in the southeastern

study were outside bark to a 4-inch top in

trees 24.6 inches d.b.h.

Management and analysis procedures in

the two studies differed greatly.

Stand basal area in the southeastern study

included trees considered submerchantable

in the Crossett study.

The southeastern plots, before their first

thinning, had a range of density from 40 to

130 percent of full stocking. Crown lengths

in the overstocked plots, especially in

stands over 40 years old, must have been

much shorter than crown lengths in trees of

the same age in the Crossett study.

The Crossett study considers total growth,

but the southeastern study dealt with net

growth.

Different site index curves were used in the

two studies.

Mean Annual Increment. -Mean annual

increment (m.a.i.) in cubic feet was still increasing

slowly on medium sites at age 45 (table 25). In

supplementary plots and in two of the five goodsite original thin-from-below treatments, cubic14
70 FT*/ACRE 85 FT’/ACRE 100 FT2/ACRE INCREASING

ii[Z[&[/[/

0 ’ ’ ’ ’ ’ 4

, ,

I I I I 1 ,

0 20 30 40 0 20 30 40 0 20 30 40 0 20 30 40

55 FT’/ACRE 115 FT2/ACRE 130 FT2/ACRE JUDGMENT

0 2 0 30 40 0 2 0 30 40

AGE 0~ STAND (YEARS)

Figure I.-Total and net cubic-foot yield, cumulative natural mortality, standing volume, anu

volume harvested in good-site original plots thinned from below and in supplementary

plots: 70&*, 85&*, 100.ft*, “increasing”, “judgment”, 55-ft2, 115~ft2, and 130-

ft z/acre treatments.

70 FT*/ACRE 85 FT */ACRE

8 8

100 FT*/ACRE INCREASING JUDGMENT

q/&&.&I

I 1 I I I 1 I I I 1 I I I I I I J

0 20 30 4 0 0 2 0 30 4 0 0 20 30 4 0

AGE OF STAND (YEARS)

Figure 5.-Total and net cubic-foot yield, cumulative natural mortality, standing volume, and

volume harvested in stands thinned from below on medium sites: 70-ft 2, 65-ft2, lOOft 2/acre, “increasing”, and “judgment” treatments.

15
Table 24.-Periodic annual growth in cubic-foot volumea

Good sites, ages Medium sites, ages

Thbmhlg

treatment 20-25 2590 3035 35-40 40-45 20-45 20-25 2530 3035 35-40 40-45 20-45

ft r/acre ___________.___________________.__________-________________________________._____~t3/acre b ._____..______ ____ ___ _______ __ __________________________.________----_________.____

70 189 162 225 208 152 187 112 107 193 192 136 148

85 217 166 244 219 105 190 114 127 221 232 129 165

100 183 185 264 220 133 197 165 148 223 250 180 193

“Increasing” 194 186 254 234 174 208 125 110 207 228 129 160

“Judgment” 181 190 230 244 179 205 125 143 233 222 144 173

--25-45-

55 . 180 204 181 107 168 . . . . . . . . . . . . . . . . .

115 . . . 142 229 295 116 195 . . . . . . . . . . . . . . . . . . .

130 . . . 125 236 306 172 210 . . . . . . . . . . . . . . . . . . .

aPlots thinned from above were omitted from these calculations.

bInside bark in trees 2 3.6 inches d.b.h. containing~ two 63.inch bolts to a 3-inch top d.i.b.

Table 25.-Adjusted cubic-foot mean annual incrementa

Thinning

treatment 25

Good sites to age

30 35 40 45

Medium sites to age

25 30 35 40 45

ft Vacre ___.______._____.________.______._____________-----.---- ft3/acre b ..__ ___________.___ _______._.___._________._.________

70 107 116 132 141 143 73 78 95 107 110

85 113 122 139 149 144 73 82 102 118 119

100 106 119 140 150 148 83 94 113 130 135

“Increasing” 108 121 140 152 154 75 81 99 115 117

“Judgment” 106 120 136 149 153 76 87 108 122 124

55 . 138 148 152 147 . . . . . . . .

115 . . 132 146 164 159 . . . . . . .

130 . 129 144 165 165 . . . . . . .

aPlots thinned from above were omitted from these calculations.

bInside bark, in trees 23.6 inches d.b.h. containing2two 63-inch bolts to a 3-inch top d.i.b.

Table 26.-Periodic annual mowth of sawtimber (Doyle)

Thinning

treatment

ft Vacre

Good sites, ages Medium sites, ages

30-35 35-40 40-45 30-45 3035 35-40 40-45 30-45

_________________________________.-_____------.----- fbm/mrea ____ _ __________ _ --_______.--______.----_---------_ _

70 954

85 833

100 571

“Increasing” 907

“Judgment”b 840

55 939

115 684

130 717

916 857 909 217 577 479 424

827 529 730 268 633 715 539

686 621 626 277 633 828 580

923 945 925 307 601 689 532

937 1,029 935 271 688 743 567

893 659 830 . . . . . . . . .

927 653 755 . . . . . . . . .

910 711 779 . . . . . . . .

‘Trees 29.6 inches d.b.h. containing 2 one Is-foot log to an 82mch top d.o.b.

b”Judgment” treatment included thinning from above and below. In all other treatments in this

table, thinning was always from below.

16
foot m.a.i. was declining. Apparently then, cubicfoot m.a.i. in periodically thinned stands

culminates at about 45 years, slightly earlier on

better sites, slightly later on medium sites;

however, at least one more regular inventory will

be needed to confirm this trend. On good-site

original thin-from-below plots, m.a.i. at 45 years

was about 148 ft” /acre; on supplementary plots,

m.a.i. was 157 ft3 /acre; and on medium-site thinfrom-below plots, m.a.i. was 121 ft3/acre.

Yield tables such as those inU.S. Department

of Agriculture, Forest Service (1976) and Meyer

(1942) clearly show that m.a.i. in fully stocked

stands culminates at about age 35. This early

culmination occurs because at age 35 natural

mortality caused by crowding exceeds the rate of

stand total growth. Thinning from below mostly

prevents crowding-induced mortality. So, we

must expect culmination of m.a.i. to occur later in

managed stands than it does in unmanaged.

Culmination occurs as a plateau, not a sharp peak.

Board-Foot Growth and Yield

Standing Volumes. -Standing sawtimber

volume in board feet (Doyle), all treatments

combined, averaged:

Medium sites Good sites Supplementary

30 years 224 1,882 3,978

35 years 1,386 5,396 7,417

40 years 4,095 8,911 10,974

45 years 7,108 11,450 12,083

Standing sawtimber volume on good-site

original plots (fig. 6) was significantly greater

when reckoned in Doyle rule from age 35 onward

in the 70-ft2 than in the lOO-ft2 treatment and

from age 40 onward in the 70-ft2 than in the 65-ft2

treatment, because: (1) stem diameter growth is

usually more rapid in heavily thinned stands than

in those lightly thinned; (2) some trees in lightly

thinned stands had not yet attained sawtimber

size, even by age 45; and (3) the Doyle rule

assigns disproportionately smaller volumes to

small-diameter logs than to large-diameter logs.

Good-site original plots thinned from below to

“increasing” basal area contained as much

standing volume in board feet (Doyle) as the 70-

ft2 plots had at 30, 35, and 40 years; at 45 years

“increasing” plots contained the greatest standing volume of any treatment (14.2 M bm),

original or supplementary. The “judgment”

treatment surpassed the 100 ft2 treatment at age

35, equaled the 85ft2 treatment at age 40, and

rivaled the “increasing” treatment at age 45.

In supplementary plots, standing board-foot

volume (Doyle) differed little between treatments

(fig. 7). When volumes were reckoned by the

International ‘/-inch rule, however, the 115-ft2

and 130-ft2 stands contained 3 to 5 M bm more

volume than did the 55-ft* stands at 40 and 45

years. In contrast, for good-site plots, use of

International %-inch rule instead of Doyle usually

lessened the differences in standing volume

between treatments.

No significant differences between treatments

occurred in standing sawtimber volume (Doyle or

Int. %) at any age on medium sites (fig. 8).

Thinning from below to an increasing basal

area usually produced noticeably greater standing

volumes (Doyle) than did thinning from above.

These differences, significant on good sites but

not on medium, diminished as the stands grew

older. The differences were due in part to the bias

inherent in the Doyle rule and in part to thinning

method. For example, good-site stands thinned

initially from above to “increasing” basal area

had a mean d.b.h. of 10.6 inches at age 40, and 27

percent of the trees were below sawtimber size.

Stands thinned always from below to “increasing” basal area on good sites had a mean

d.b.h. of 13.0 inches at age 40, and every tree was

in the lo-inch class or larger.

Total Yields. -On good-site original plots,

sawtimber yield varied significantly with intensity,of thinning, being low in the lOOft*, intermediate in the 85-ft2, and high in the 70 ft2

treatment. The “increasing” thin-from-below

treatment produced board-foot yields somewhat

greater than yields in the 70-ft4 plots (Doyle and

Int. ‘/4) (fig. 6). The “judgment” treatment surpassed the lOOft at age 35 and thereafter closely

trailed the 70-ft* treatment.

Thinning to 55 ft2 basal area resulted in

greater sawtimber net yields (Doyle and Int. 1/4)

than did thinning to 115 ft2 or 130 ft* (fig. 7). At

45 years, the 55 ft* stands had a net yield of

16,727 fbm/acre (Doyle) or 26,057 fbm/acre (Int.

%). In short rotations on good sites, heavy

thinning produced the largest net board-foot

yields.

On medium sites from age 35 onward, the 70-

ft2 treatment yielded much less sawtimber than

did any other treatment. Little difference was

evident in board-foot yield among the 85-ft’ , lOOftp, “increasing,” and “judgment” treatments.

17
As shown below, sawtimber yields of the 70-

ft?, 85-ft’, and “increasing” treatments on good

sites in this study are similar to those reported by

Andrulot et al. (1972) for the “normal thinning”

plots in the Urania study.

Age of

stand

years

30

35

40

45

Urania study Crossett study

Total Pine Thinned from below to:

stand only 7oft2 85 ft2 “Incr.”

____ ________---______. pm/acre Int. l/a ----- ----- --.--------

7,594 7,441 4,960 6,263 5,980

13,185 13,003 14,173 14,520 14,923

18,777 18,575 20,587 20,843 21,810

23,369 23,155 26,233 24,427 28,243

Thirty-year yields exceeded those at Crossett,

perhaps because a 5-inch top was used at Urania

and an a-inch top at Crossett, and because early

thinning at Urania was more drastic than that at

Crossett. From age 35 onward, Crossett yields

exceeded Urania yields, in part because Crossett

plots were kept free of hardwoods and in part

because site index was about 5 feet higher at

Crossett.

Periodic and Mean Annual Increment.-

Periodic annual growth in sawtimber culminated

between ages 35 and 40 at 858 fbm/acre in good70 FTzlACRE ES FT2/ACRE

3 0

TOTAL 8 NET

. 25 MORTALITY

3

k

s

2 0

site original plots thinned from below (all

treatments combined) and at 910 fbm/acre in

supplementary plots. Periodic annuaj growth

culminated at 954 fbm/acre in the 70-ft’ and 833

in the 85-ft’ between ages 30 and 35, and at 945

fbm between ages 40 and 45 in the “increasing”

plots (table 26).

On good sites, culmination usually occurred

earlier in the rotation and at a higher value in

heavy thinning treatments and occurred later at a .-

lower value in light thinning treatments. On

medium sites, p.a.g. was 678 fbm/acre between

ages 40 and 45 in plots thinned from below (all

treatments combined); whether this rate was a

maximum cannot be known before the next inventory. Culmination usually occurred later on

medium sites than on good sites. Thinning

intensity also affected results on medium sites, in

a reverse of its effect on good sites. On medium

sites, p.a.g. culminated at 828 fbm in the lOO-ft’,

at 715 fbm in the 85-ft*, at 689 fbm in the “increasing”, and at 577 fbm in the 70.ft’ treatment.

When these p.a.g. calculations were made with

board feet Int. %, culmination occurred between

ages 30 and 35 on good sites, in all thin-frombelow treatments, original and supplementary. On

medium sites, p.a.g. culminated between ages 40

and 45 in all thin-from-below plots except the 70

100 FT2/ACRE INCREASING -

OL- 0 30 3 5 4 0 4 5 0L1I1LI

3 0 35 4 0 4 5 0 3 0 35 4 0 4 5 0 3 0 35 4 0 4 5

AGE OF STAND (YEARS)

Figure 6.-Total sawtimber yield, net yield, cumulative natural mortality, standing volume, and

volume harvested in thinning from below: 70-ft*, 85-ft*, NO-f@/acre, and “increasing”

basal area on good sites.

18
55 FT2/ACRE

TOTAL 8

NET YIELD

VOLUME

II5 FT2/ACRE

MORTALITY --+

d

130 FT2/ACRE

“OL ’

1 I 4 L IL’ I I

l

0 30 35 4 0 45 0 30 35 4 0 45 0 30 35 4 0 45

AGE OF STAND (YEARS)

Figure 7.-Total sawtimber yield, net yield, cumulative natural mortality, standing volume, and

volume harvested in thinning from below: 55-ft 2, 115-ft*, and 130-fP/acre on good

70 FT’IACRE 85 FT’/ACRE

0

LLL

30 35 40 45

100 FT’IACRE

0IL30 35 40 45

AGE OF STAND (YEARS)

INCREASING

0I/: 30 35 40 45

Figure K-Total and net sawtimber yield, standing volume and volume harvested, in thinning

from below: 70-, 85-, lOO-ft2, and “increasing” basal area on medium sites.

19
ft2 where it culminated between ages 35 and 40.

The p.a.g. values in table 26 cannot be

compared directly with those found by Nelson et

al. (1961) for the southeastern study, because the

latter are in board feet Int. ‘/4. And even when

table 26 is converted to Int. 1/4, the p.a.g. values

are much higher in the Crossett study than in the

southeastern study.

Mean annual increment calculated in board

feet Doyle (table 27) or Int. ‘/was still increasing

rapidly at age 45 in all treatments on both sites.

Table 58 in U.S. Department of Agriculture,

Forest Service (1976) shows that culmination in

normal stands occurs at 70 years on site index 80,

at 65 years on site index 90, and at 60 years on site

index 100, for board feet (Doyle). Davis (1954),

plotting data from Meyer’s (1942) bulletin, indicated 44 years on site index 100, 45 years on site

index 90, and 46 years on site index 80 for board

feet Int. % in unthinned fully stocked stands.

Culmination can be expected to occur later in

managed than in unmanaged stands.

This Il-yearald stand was thinned always from below to an

increasing basal area. The increasing technique, one of several

compared in this study, was the most effective at growing

sawtimber in 45 years on good sites.

This Il-yearald stand on a medium site was thinned always

from below to 100 ft 2 /acre. This thinning regime was the most

effective of several compared for growing sawtimber on

medium sites.

20
Table 27.-Mean annual increment of sawtimber (Doyle)

Thinning

Good sites to age Medium sites to age

treatment 30 35 40 45 30 35 40 45

ft Vacre ________ __._ _____________._.____-..___..__.__.__.___ fbm/acW a _________________________________.____.___________

70

85

100

“Increasing”

“Judgment’b

55

115

130

78 203 292 355 5 3 5

96 201 280 307 1 7 53

36 112 184 233 5 44

93 209 299 370 8 51

51 164 261 346 11 48

142 256 336 372 . . . . .

130 209 299 338 . . . . .

125 210 297 343 . . . . .

103 145

126 191

117 196

120 183

128 197

.... ....

.... ....

.... ....

a Trees 29.6 inches d.b.h. containing Lone 16-foot log to an d-inch top d.o.b.

b”Judgment” treatment included thinning from above and below. In aII other treatments in this

table, thinning was always from below.

Table 28.-Cubic-foot volumes of merchuntabk wood removed: unaajusted initial cut, adjusted initial cut,a and adjusted total

harvests, and natural mortality in merchantable treesb

Good sites Medium sites

Total Total

through through

Initial Cut age 40 Initial cut age 40

Thbming Thinning Mortality Mortality

level method Unadj . Adj . Unadj . Adj . ages 30-45 Unadj . Adj . Unadj . Adj. ages 30-45

ft=/acre ____________________________.__________________-.----------------- fts/apre _.___._._________.__.___________________________._.__._ ________

70

85

100

“Incr.”

“Judg.”

55

115

130

Above 1,061 793 3,630 3,362 0

Below 767 779 3,133 3,145 0

Above 737 708 3,381 3,352 87

Below 711 652 3,148 3,089 1,093

Above 630 483 2,987 2,840 572

Below 328 525 2.619 2,816 480

Above 738 962 2,707 2,931 335

Below 940 790 3,177 3,027 25

Both 608 730 2,747 2,971 264

Below 1,790 1,999 3,905 4.114 0

Below 891 875 2,719 2,703 1,146

Below 740 548 2,354 2,162 974

642 522 2,302 2,182 0

392 520 2,196 2,323 29

405 407 2,636 2,638 0

430 344 2,223 2,137 0

285 164 1,889 1,768 34

209 223 2,304 2,318 40

439 549 1,887 1,997 144

444 432 1,943 1,931 9

455 542 2,500 2,587 0

.... ....

.... ....

. .

. . . . .

. . . . .

. . . .

. . . . .

‘Initial cuts were made at age 25 in the 56 ft2, 116 ft*, and 130 ft2/acre treatments. Initial cuts were made at age 20 in ah other

treatments, on both sites.

bTotal removal = total thinnings + total mortality.

21
GOOD SITES MEDIUM SITES

Cubic-Foot and Board-Foot Volumes in Intermediate Harvests

Table 28 shows total cubic-foot volume OI

merchantable wood harvested from age 2C

through age 40 in original plots and from age 25

through age 40 in supplementary plots. Adjusted

and unadjusted volumes in first thinnings are

presented side by side, as are adjusted and

unadjusted total thinnings through age 40. This

arrangement shows the amount of the adjusted

initial cut and how it affected total harvest. Total

volume in natural mortality of merchantable trees

is shown.

Total board-foot volumes (Doyle) harvested,

ages 30-40, in good-site original thin-from-below

plots ranged from less than 1 M bm in

“judgment” plots through 1.4 M bm in 100~ft’ to

2.9 M bm in 70-ft? /acre plots. On medium-site

thin-from-below plots, total cut, ages 30-40,

averaged only 0.27 M bm; the only apparent effect

of thinning level was that “judgment” thinning

produced the least volume ( < 0.06 M bm).

Thinning from above harvested only 58 percent of

the harvest of thinning from below on good sites

and 82 percent on medium. On supplementary

plots, total harvests, ages 30-40, were 5.3 M bm in

55-ft’ , 1.6 M bm in 115-ft’, and 0.5 M bm in 130-

ft* /acre plots. Here again, however, the bias

inherent in the Doyle rule can lead to erroneous

conclusions.

When board-foot volumes harvested were

reckoned by Int. % rule, the 70-ft2 treatment

produced the largest total cut (5.9 M bm) on goodsite original plots, and the 85-ft 2 treatment

produced the largest (1 .l M bm) on medium sites.

On both sites, the smallest total harvests in thinfrom-below plots were in the lOOft treatment:

2.2 M bm on good sites and 0.4 M on medium. On

supplementary plots, total cuts ranged from 9.9 M

bm on 55-ft* to 1.0 M bm on 130-ft’/acre plots.

DISCUSSION

Each thinning treatment in this study

represents a silvicultural alternative. The

“judgment” treatment, however, is a special case.

On both good and medium sites, yields in

“judgment” plots compared favorably with yields

of most other treatments (fig. 9). But this finding

30-

$25 -

\

2 20 -

2

$ 15-

2

1 ‘O-

? 5-

TOTAL YIELD

0 3 0 3 5 4 0 4 5 0L3 0 3 5 4 0 4 5

AGE OF STAND (YEARS)

Figure O.-Total and net sawtimber yield, and volume harvested in the “judgment” treatment on good and

medium sites.

may be of little value to the average forest landowner. A team of four to six experienced workers

acting together and without restrictions can thin

as well as, and frequently better than, a single

employee faithfully following one of the other

eight thinning regimes. In reality, however, most

timber marking is done not by a committee of

experienced people, but by an individual often

with limited experience and limited time to get the

job done.

So, the treatment a landowner selects must

depend on his objectives and circumstances; the

site quality of the land; and the age, condition,

and stand structure of his loblolly-shortleaf pine

forest.

Management’s primary aim may be growing

sawtimber trees 9.6 inches d.b.h. and larger, in

even-aged stands. Results of this study make a

good case for initial heavy thinning from below,

on good sites, to a basal area of 70 ft* /acre at age

20 and then increasing the residual stand density

by 5-ft’ steps. The “increasing” treatment

produced the best yield, and the 70-ft’ the second

best. If the landowner is trying to decide between

22
the two, he may elect to be guided by the expected

mean d.b.h. (fig. l), the number of trees per acre

(tables 3-7), and any restraints on rotation length

peculiar to his ownership. These two treatments

began alike. So, if the landowner selected either

treatment, he could change to the other later. The

55-ft2 treatment also produced large board-foot

yields.

These three treatments share some advantages and liabilities: they involve a small

investment in growing stock; they encourage

rapid growth of trees to large sizes in short

rotations; they involve heavy early thinnings and,

therefore, relatively large early returns; and they

encourage aggressive understory development

and, so, require much weeding. The better the site

and the more severe the thinning, the more urgent

will be the need for understory control.

If the landowner’s primary objective is to grow

wood fiber, densities higher than these are, indicated. In this study, the 130-ft* and the 115-R-2.

treatments produced the greatest total cubic-foot

yields in the supplementary plots. The lOO-ft2

treatment produced the greatest total yield in the

good-site original plots. Most of the reduction of

net yield by the southern pine beetle occurred

after age 40. So, if growing pulpwood is the sole

objective, the landowner may prefer to do no

thinning at all and to clearcut at 35 years, in view

of the high costs of thinning and the small cut

volumes for the 130-ft2 and the 115-ft? treatments.

If the landowner’s objective is to grow sawtimber on medium sites, the “increasing”

treatment would be best. Thinning to 85 ft2 or 100

ft2 produced slightly greater yields at 40 and 45

years, but the “increasing” treatment involves a

smaller investment in growing stock and a heavier

early thinning.

If the aim of management is to grow pulpwood

on medium sites, light thinning, or perhaps no

thinning, is called for. Thinning from below to 100

ft2 was the best pulpwood regime on medium sites

in this study.

LITERATURE CITED

Andrulot, E. R., L. P. Blackwell, and P. Y. Burns.

1972. Effects of thinning on yield of loblolly

pine in central Louisiana. Div. Res. Coll. Life

Sci., Bull. 6,145 p., La. Tech. Univ., Ruston,

La.

Davis, K. P.

1954. American forest management. 482 p.

McGraw-Hill Book Co., Inc., New York.

Mesavage, C.

1947. Tables for estimating cubic-foot volume

of timber. U.S. Dep. Agric. For. Serv. Occas.

Pap.111, 71 p. South. For. Exp. Stn., New

Orleans, La.

Mesavage, C., and J. W. Girard.

1946. Tables for estimating board-foot volume

of timber. U.S. Dep. Agric. For. Serv.

[Unnumbered Publ.] 94 p., Washington,

D.C.

.,-Meyer, W. H.

1942. Yield of even-aged stands of loblolly pine

in northern Louisiana. Yale Univ.: Sch. of

For. Bull. 51, 39 p. Yale Univ., New Haven,

ct.

Nelson, T. C., T. Lotti, E. V. Brender, and K. B.

Trousdell.

1961. Merchantable cubic-foot volume growth

in natural loblolly pine stands. U.S. Dep.

Agric. For. Serv., Stn. Pap. 127, 12 p.

Southeast. For. Exp. Stn., Asheville, N.C.

Nelson, T. C., K. B. Trousdell, E. V. Brender, and

T. Lotti.

1963. Board-foot growth of loblolly pine as

related to age, site, and stand density. J.

For. 61: 120-123.

U.S. Department of Agriculture, Forest Service.

1976. Volume, yield, and stand tables for

second-growth southern pines. U.S. Dep.

Agric. Misc. Publ. 50 [revision of 1929

edition], 202 p., Washington, D.C.

Zahner, R.

1962. Loblolly pine site curves by soil groups.

For. Sci. 8: 104-110.

23
BURTON, J. D.

1979. Growth and yield in managed natural stands of

loblolly and shortleaf pine in the West Gulf Coastal Plain.

U.S. Dep. Agric. For. Serv. Res. Pap. SO-159, 23 p.

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

Presents total and net yield, standing volume, volume harvested, and number of trees by d.b.h. class by 5-year periods,

ages 20-45, in even-aged stands on two sites, repeatedly

thinned to various densities. Cubic-foot volume to a 3-inch top

is given for ages 20-45. Board-foot volume, Doyle and Int. %

inch, to an 8-inch top, is given for ages 30-45.

Additional keywords: Pinus taedu L., P. echinata Mill., stand

structure, diameter distribution, stand density.
1 inch

1 foot

1 acre

1 tree/acre

1 cubic foot/acre

1 square foot/acre

1 board foot

1 cubic foot

Conversion to Metric Units

= 2.54 centimeters

= 0.3048 meter

= 0.4047 hectare

= 2.47 trees/hectare

= 0.06997 cubic meters /hectare

= 0.2296 square meter/hectare

= 0.005663 cubic meter

= 0.0283 cubic meter