Agriculture 

@ XrRg Forest Service 

Northeastern Forest 

Experiment Station 

Research Paoer 

Thinning Increases Growth 

I- - - Stands in West virghia 

Neil I. Lamson 
-- 

The Author 

Neil I. Lamson received his B.S. and MS. in silviculture and forest 

soils from the State University of New York College of Environmental 

Science and Forestry. He joined the USDA Forest Service, State and Private 

Forestry, in 1972. Currently he is a research forester in timber management 

at the Timber and Watershed Laboratory in Parsons, West Virginia. 

Abstract 

In north-centrai west Virginia, previously unmanaged, 60-year-old 

cherry-maple stands were thinned to 60 percent relative stand density. 

Thinning reduced mortality, redistributed growth onto fewer, larger stems, 

and increased individual tree growth. Five-year periodic basal area growth 

per acre was 1.2 times greater in thinned stands than in unthinned stands. 

Periodic basal-area growth of individual trees was greater in thinned stands 

than in controls: 3.0 times for all stems and 1.3 times for dominants and 

codominants. Relative stand density in the thinned stands increased 1.6 

percent annually. 
Introduction 

The Middle Mountain area on 

the Monongahela National Forest in 

north-central West Virginia supports 

well-stocked cherry-maple stands 

similar to those found in Allegheny 

hardwood forests of northwestern 

Pennsylvania. This area is 

approaching the southern limit of 

the most productive natural range of 

black cherry. There are about 

125,000 acres of commercial forest 

in the Middle Mountain area, most 

of which is in even-aged cherrymaple stands 60 to 80 years old 

(Figure 1). Thinnings are now 

becoming economically feasible in 

many of these stands. An important 

question is "Will these unrnanaged, 

even-aged stands respond to 

thinning at ages 60 years or 

greater?" In this paper, 5-year 

growth in thinned stands is 

compared with that of unthinned 

stands. 

Figure 1.-Typical 60-year-old cherry-maple stand before thinning. 
Study 

Two tracts, each about 5 acres 

in size, were thinned to 60 percent 

relative stand density (Marquis et al. 

1984) to determine the amount of 

wood products that could be 

produced from thinning 60-year-old 

cherry-maple stands on Middle 

Mountain. One tract was thinned in 

the fall of 1976 and the other was 

thinned in the spring and summer of 

1977 (Figure 2). Detailed product 

yield data were collected, but no 

effort was made to document the 

residual stand growth. 

In the spring of 1979, four study 

plots, each 114-acre in size, were 

established in each thinned tract. 

Two additional study plots, each 

one-quarter acre in size, were established in uncut areas close to each 

thinned tract. On each of the 12 

plots, all trees at least 1.0 inch in 

d.b.h. were permanently marked 

with galvanized wires and brass 

tags (Lamson and Rosier 1984). 

Diameter at breast height (d.b.h.), 

species, and crown class of each 

tagged tree were recorded in April 

1979 before that year's growth had 

commenced. 

Figure 2.-Typical cherry-maple stand after thinning. Tree being measured is 9.0 

inches d.b.h. 
In the fall of 1983, 5 growing 

seasons later, the plots were again 

inventoried. The d.b.h. of each live 

tagged tree was measured at the 

same height that was used in 1979. 

lngrowth and mortality were 

recorded, as well as the crown class 

of live trees over 1.0 inches d.b.h. If 

we assume that diameter growth 

had ceased by the time thinning 

was completed in the second area 

in the summer of 1977, these data 

represent growth for the 2nd 

through 6th and 3rd through 7th 

growing seasons after thinning. One 

control plot was vandalized and 

dropped from the study, leaving a 

total of 11 plots. 

In April 1979, when the study 

plots were installed, the control 

areas averaged 735 stems per acre, 

155.6 square feet per acre (1.0 + 

inch d.b.h.), 2,977 cubic feet per 

acre (5.0 + inch d.b.h.), 8,828 board 

feet per acre (11.0+ inch d.b.h.) and 

105 percent relative stand density 

(1.0 + inch d.b.h.). The thinned 

stands averaged 407 stems per acre, 

104.2 square feet per acre, 2,041 

cubic feet per acre, 7,862 board feet 

per acre, and 66 percent relative 

stand density (Table 1). 

Assuming that the control and 

thinned stands were similar before 

treatment, thinning removed mostly 

poletimber (5.0 to 10.9 inches 

d.b.h.). When this study was installed, basal area per acre of stems 

1.0 to 4.9 inches d.b.h. and stems 

11.0 + inches d.b.h. were similar for 

the control and thinned stands. 

However, -basal area of poletimber 

in the thinned stands was only 32.9 

square feet per acre, while in the 

control stands, poletimber basal 

area averaged 74.2 square feet per 

acre. This follows the guidelines for 

thinning Allegheny hardwood 

stands (Marquis et al. 1984), in 

which commercial thinnings 

concentrate the cut in trees of intermediate and weak codominant 

crown class to redistribute stand 

growth onto the best codominant 

trees. 

Table 1. Stand data at the time study plots were installed and 5 growing seasons later. I 

Thinned Control 

5.0- 5.0- 

1 .O-4.9 10.9 11.0+ Total 1 .O-4.9 10.9 11.0+ Total 

April 1979 

No.lacre 

B Alac re 

Cu.ft.lacre 

Bd.ft.lacre 

RSD 

September 1983 

No.lacre 

BAlacre 

Cu.ft.lacre 

Bd.ft.lacre 

RSD 

Basal area = Square feet of basal area of stems 1.0+ inch d.b.h. 

Cu. ft. vol. = Cubic foot volume to 4 inches d.i.b. of stems 5.0+ inches d.b.h. 

Bd. ft. vol. + International 114-inch board-foot volume to 8 inches d.i.b. of stems 

11.0+ inches d.b.h. 

RSD = Relative stand density, percent. 
Results 

Stand Growth 

All trees. Thinning increased 

the per-acre growth (Table 2). Total 

basal area per acre of all trees at 

least 1.0 inch in d.b.h. was greater 

in the control stands than in the 

thinned stands. However, basal-area 

growth for the 5-year period averaged 16.8 square feet per acre in 

thinned stands and only 7.8 square 

feet per acre in the control stands; 

an increase of 2.2 times. Similarly, 

cubic-foot volume growth of trees at 

least'5.0 inches d.b.h. for the Byear 

measurement period was 496 cubic 

feet per acre in the thinned stands 

and only 238 cubic feet per acre in 

the control stands; an increase of 

2.1 times due to thinning. 

Board-foot volume growth of 

those trees at least 11.0 inches in 

d.b.h. for the 5-year period averaged 

2,955 board feet per acre in the 

thinned stands and 2,530 board feet 

per acre in the control stands, 

which is an increase of 1.2 times 

due to thinning. 

Table 2. Five-year stand growth. 

Dominant and codominant 

trees. Dominant and codominant 

trees are the most important 

component of even-aged stands 

because these generate most of the 

revenue at harvest. Thinning also 

increased the per acre growth of 

trees that were dominant or codominant in 1983 (Table 2). It is interesting that the number of dominant 

and codominant stems per acre was 

about the same in thinned stands 

(109) and in the control stands (112). 

However, the 5-year basal area 

Thinned Control 5-Year 

Growth 

Ratio 

5-Year 5-Year Thinned: 

4179 9/83 Growth 4179 9/83 Growth Control 

ALL TREES 

No.lacre 407 41 7 735 657 

BAIacre 104.2 121.0 16.8 (407) 155.6 163.4 7.8 (735) 

Cu.ft.lacre 2,041 2,537 496 (173) 2,977 3,215 238 (282) 

Bd.ft.lacre 7,862 10,817 2,955 ( 74) 8,828 11,358 2,530 ( 71) 

RSD 66 74 105 106 

DOMINANT AND CODOMINANT TREES 

No.lacre 109 109 11 2 112 

BAlacre 80.6 93.2 12.6(109) 85.6 95.8 10.2 (1 12) 

Cu.ft.lacre 1,858 2,258 400 (107) 2,027 2,246 219 (110) 

Bd.ft .lac re 7,767 10,648 2,881 ( 72) 8,436 10,740 2,304 ( 65) 

RSD 43 48 44 48 

DOMINANT AND CODOMINANT CHERRY TREES 

Nolacre 5 1 5 1 69 69 

BAlacre 48.1 54.7 6.6 ( 51) 61 .O 67.9 6.9 ( 69) 

Cu.ft.lacre 1,157 1,369 212 ( 51) 1,482 1,622 140 ( 69) 

Bd.ft.lacre 5,892 7,740 1,848 ( 47) 6,997 8,691 1,694 ( 52) 

RSD 20 22 25 27 

Note: Numbers in parentheses refer to number of trees used in calculations. 

Number = Number of stems 1.0-1- inches d.b.h. 

BA = Square feet of basal area of stems 1.0+ inches d.b.h. 

Cu.ft. = Cubic-foot volume to 4 inches d.i.b. of stems 5.0+ inches d.b.h. 

Bd.ft. = International 114 inch board-foot volume to 8 inches d.i.b. of stems 11.0+ inches d.b.h. 

RSD = Relative stand density, percent. 
growth of dominant and codominant 

trees averaged 12.6 square feet per 

acre in the thinned stands and only 

10.2 square feet per acre in the 

control stands. This represents a 20 

percent increase due to thinning. In 

1983 the total basal area of 

dominant and codominant stems 

averaged about the same for 

thinned and control stands, 93.2 and 

95.8 square feet per acre, 

respectively. 

Volume growth for the 5-year 

period averaged 400 cubic-feet per 

acre in the thinned stands, and 219 

cubic feet per acre in the control 

stands; an 80 percent increase due 

to thinning. Sawlog volume growth 

of dominant and codominant trees 

averaged 2,881 board feet per acre 

in the thinned stands and 2,304 

board feet per acre in the control 

stands. Like cubic-foot volume, total 

board-foot volume per acre was 

nearly the same for thinned and 

control stands at the end of the 

measurement period: 10,648 and 

10,740 board feet per acre, 

respectively. 

Dominant and Codominant 

Black Cherry Trees. The dominant 

and codominant trees in these 

stands are primarily a mixture of 

black cherry, red maple, and sugar 

maple. Of these species, black 

cherry is the most valuable. Basalarea growth per acre of dominant 

and codominant black cherry trees 

that were dominant or codominant 

in 1983 was about equal in the 

thinned and control stands, 6.6 and 

6.9 square feet per acre, respectively. Although total basal-area 

growth per acre was not increased 

by thinning, the individual trees did 

respond to thinning. In the thinned 

stands, 51 dominant and 

codorninant trees grew 6.6 square 

feet per acre, while in the control 

stands, 69 trees grew 6.9 square 

feet per acre. 

Both cubic-foot and board-foot 

volume per acre of dominant and 

codominant black cherry trees were 

increased by thinning. 

Mortality, lngrowth and Survivor 

Growth 

All Trees. Mortality was greater 

in the control than in the thinned 

stands (Table 3). In both stands, 

mortality occurred only in the intermediate and overtopped crown 

classes. When the stand growth 

from table 2 was adjusted for 

ingrowth and mortality, the survivor 

growth was greater in the thinned 

than in the control stands. Thinning 

increased per-acre survivor basal 

area growth 1.2 times, survivor 

cubic-foot volume growth 1.5 times, 

and survivor board-foot volume 

growth 1.1 times (Table 3). 

Dominant and codominant 

trees. There was no mortality or 

ingrowth of dominant and 

codominant trees. In other words, 

no dominant or codominant trees 

died during the 5-year measurement 

period and no trees that crossed the 

1.0-inch d.b.h. threshold were dominant or codominant. However, a 

portion of the cubic-foot volume 

present in 9183 came from trees that 

crossed the 5.0-inch d.b.h. threshold, which is defined as cubic-foot 

volume ingrowth. Similarly, the 9183 

board-foot volume of trees that 

crossed the 11.0-inch d.b.h. threshold is defined as board-foot volume 

ingrowth. When stand growth from 

table 2 was adjusted for ingrowth, 

thinning increased the survivor 

growth of dominants and codominants (Table 3). Per-acre survivor 

basal-area growth was increased 1.2 

times, survivor cubic-foot growth 

was increased 1.8 times, and survivor board-foot growth was 

increased 1.2 times. 

Dominant and codominant 

black cherry trees. Survivor growth 

of dominant or codorninant black 

cherry trees was increased by thinning (Table 3). Survivor basal-area 

growth in the thinned stands averaged 6.6 square feet per acre while 

in the control it averaged 6.9 square 

feet per acre. But because there 

were 69 trees per acre in the control 

stands and only 51 trees per acre in 

the thinned stands, individual tree 

growth was increased 1.3 times by 

thinning. Similarly, board foot 

volume growth per acre was only 

slightly increased by thinning, but 

individual tree growth was 

increased 1.4 times. Survivor basalarea growth per acre of thinned 

stands averaged 1.5 times more 

than that in the control stands. 

Individual Tree Growth 

All trees. Diameter growth of all 

individual trees was increased about 

3 times by thinning (Table 4). During 

the 5-year measurement period, the 

average d.b.h. increased from 5.5 to 

6.1 inches in the thinned stands, 

while in the control stands it 

increased from 5.1 to 5.3 inches. 

Basal-area growth per tree was 

increased even more than d.b.h. 

growth per tree by thinning. In the 

thinned stands, basal area per tree 

increased from 23.7 to 29.2 square 

inches in the 5-year measurement 

period. Basal area per tree in the 

control stands increased from 20.4 

to 22.1 square inches. This represents an increase due to thinning of 

3.2 times. Analysis of variance indicated that individual trees in the 

thinned stands grew significantly 

faster than those in the control 

stands. 

Dominant and codominant 

trees. For the 5-year period, d.b.h. 

and basal-area growth of individual 

trees that were dominant or codominant in 1983 was increased about 

1.3 times by thinning (Table 4). In 

the thinned stands, average d.b.h. 

per tree increased only 0.9 inches, 

while in the control, average d.b.h. 

increased only 0.7 inches. Similarly, 

average basal area per tree 

increased by 16.5 square inches per 

tree in the thinned stands, but only 

12.9 square inches per tree in the 

control stands. Analysis of variance 

indicated that dominant and 

codominant trees in the thinned 

stands grew significantly faster than 

those in the control stands. 
Table 3. Mortality, ingrowth, and survivor growth of thinned and unthinned stands. 

Control 

5-Year 5-Year 

stand Survivor stand Survivor 

growth' Mortality2 Ingrowth3 growth4 growth Mortality lngrowth growth 

Survivor 

growth 

ratio 

Thinned: Control 

No.lacre 

BAlacre 

CFlacre 

BFlacre 

Nolacre 

BAlacre 

CFlacre 

BFIacre 

No .lac re 

BAlacre 

CFlacre 

BFlacre 

ALL TREES 

DOMINANT AND CODOMINANT TREES 

DOMINANT AND CODOMINANT BLACK CHERRY TREES 

' From table 2. 

Trees 1.0 + inches d.b.h. 

Vngrowth: Number and basal area threshold d.b.h. is 1.0 inch. 

Cubic foot threshold d.b.h. is 5.0 inches. 

Board foot threshold d.b.h. is 11.0 inches. 

Survivor growth = stand growth + mortality-ingrowth, i.e. growth of trees that were alive both in 4/79 and 9/83. 
Table 4. Five-year individual tree growth based on plot meansa. 

Thinned Control 5-Year Growth 

Ratio 

5-Year 5-Year Thinned: Signifi4179 9183 Growth 4179 9183 Growth Control cance 

ALL TREES 

No. plots 8 3 

D.b.h.ltree(in) 5.5 6.1 0.6 5.1 5.3 0.2 3.0 * * 

BAltree(in2) 23.7 29.2 5.5 20.4 22.1 1.7 3.2 * 

DOMINANT AND CODOMINANT TREES 

No. plots 8 3 

D. b. h.ltree(in) 11.2 12.1 0.9 11.4 12.1 0.7 1.3 * 

BAltree(in2) 98.5 115.0 16.5 102.1 115.0 12.9 1.3 t* 

I DOMINANT AND CODOMINANT BLACK CHERRY TREES 

No. plots 8 3 

D.b.h.ltree(in) 13.0 13.8 0.8 12.4 13.1 0.7 1.1 

BAltree(in2) 132.7 149.6 16.9 120.8 134.8 14.0 1.2 NS 

l 

a All data are arithmetic means, not quadratic means. 

** = Significantly different at 0.01 level, * =significantly different at 0.05 level. 

NS= not significantly different. 
Dominant and codominant 

black cherry trees. During the 5-year 

measurement period, d.b.h. and 

basal-area growth of individual black 

cherry trees that were dominant or 

codominant in 1983 was also 

increased by thinning (Table 4). 

Average d.b.h. per tree increased 

from 13.0 to 13.8 inches in the 

thinned stands, but only from 12.4 

to 13.1 inches in the control stands. 

Similarly, basal-area growth per tree 

averaged 16.9 square inches in the 

thinned stands but only 14.0 square 

inches in the control stands; an 

increase of 1.2 times due to thinning. Again, analysis of variance 

indicated that trees in the thinned 

stands grew significantly faster than 

those in the unthinned stands. 

Discussion 

It is not possible to predict 

long-term growth and yield of 

thinned and unthinned cherry-maple 

stands from the 5-year growth data 

of this study. However, these data 

show that trees in these 60-year-old 

stands did respond to thinning. 

Mortality was reduced, growth was 

redistributed onto fewer, larger 

stems, and individual trees grew 

faster. 

lngrowth was negligible in both 

the control and thinned stands during the !%year measurement period. 

Table 1 indicates that the total number of stems per acre increased 

from 407 to 417 in thinned stands 

during the 5-year period. lngrowth 

exceeded mortality by 10 stems per 

acre. However, in the control 

stands, the total number of stems 

per acre fell from 735 to 657-a 

decrease of 78 trees per acre-during the measurement period. In 

other words, thinning eliminated 

mortality during the 5-year measurement period. 

Total basal area and cubic-foot 

volume growth was about 2 times 

greater in the thinned stands than in 

the control stands (Table 2) even 

though the thinned stands had only 

about two-thirds as many stems per 

acre as the control stands. At the 

beginning of the measurement 

period the average diameter of all 

trees was 5.5 inches in the thinned 

stands and 5.1 inches in the control 

stands (Table 4). This shows that 

thinning redistributed the total 

stand growth of the stems 1.0 inch 

d.b.h. and larger onto fewer, larger 

stems. 

Table 4 shows that individual 

trees grew faster in the thinned 

stands than in the control stands. 

Not only was the absolute diameter 

and basal area growth greater, but 

analysis of variance indicated that 

individual tree growth was significantly greater in the thinned stands 

than in the control stands. 

Relative stand density in the 

thinned stands increased 8 percent 

during the Byear measurement 

period or 1.6 percent annually. At 

this rate, relative stand density will 

reach 90 percent in another 10 

years. Current guidelines recommend thinning when the stands 

exceed 85 percent relative stand 

density. Therefore, it appears that 

these stands can be thinned at 

intervals of 10 to 15 years. 

In conclusion, these data indicate that 60-year-old, previously 

unmanaged even-aged cherry-maple 

stands will respond to thinning. 

Literature Cited 

Lamson, Neil I.; Rosier, Robert L. 

Wires for long-term identification. 

Journal of Forestry, 82(2):110-111; 

1984. 

Marquis, David A.; Ernst, Richard L.; 

Stout, Susan L. Prescribing silvicultural treatments in hardwood 

stands of the Alleghenies. Gen. 

Tech. Rep. NE-96. Broomall, 

PA: US. Department of Agriculture, Forest Service, Northeastern Forest Experiment 

Station; 1984.90 p. 
Lamson, Neil I. Thinning increases growth of 60-year-old cherry-maple stands 

in West Virginia. Res. Pap. NE-571. Broomall, PA: U.S. Department of 

Agriculture, Forest Service, Northeastern Forest Experiment Station; 1985. 

8 P. 

In north-central West Virginia, previously unmanaged 60-year-old cherrymaple stands were thinned to 60 percent relative stand density. Thinning 

reduced mortality, redistributed growth onto fewer, larger stems, and 

increased individual tree growth. Five-year periodic basal-area growth per 

acre was 1.2 times greater in thinned stands than in unthinned stands. 

Periodic basal-area growth of,individual trees was greater in thinned stands 

than in controls: 3.0 times for all stems and 1.3 times for dominants and 

codominants. Relative stand density in the thinned stands increased 1.6 

percent annually. 

I ODC: 242, 561, 562, 176.1 

Keywords: Thinning, diameter increment, volume increment, Allegheny 

hardwoods 
Headquarters of the Northeastern Forest Experiment Station are in 

Broomall, Pa. Field laboratories are maintained at: 

Amherst, Massachusetts, in cooperation with the University of 

Massachusetts. 

Berea, Kentucky, in cooperation with Berea College. 

0 Burlington, Vermont, in cooperation with the University of 

Vermont. 

0 Delaware, Ohio. 

0 Durham, New Hampshire, in cooperation with the University of 

New Hampshire. 

Hamden, Connecticut, in cooperation with Yale University. 

0 Morgantown, West Virginia, in cooperation with West Virginia 

University, Morgantown. 

Orono, Maine, in cooperation with the University of Maine, 

Orono. 

Parsons, West Virginia. 

0 Princeton, West Virginia. 

0 Syracuse, New York, in cooperation with the State University of 

New York College of Environmental Sciences and Forestry at 

Syracuse University, Syracuse. 

University Park, Pennsylvania, in cooperation with the 

Pennsylvania State University. 

0 Warren, Pennsylvania. 

*U.S. GOVERNMENT PRINTING OFFICE: 1985-505-028:20023