Forest Service 

Northeastern Forest 

Experiment Station 

Research 

Paper N E-543 

Quality Response of Even-Aged 

80-Year-Old White Oak Trees 

ter Thinning 

David L. Sonderman 
Abstract 

Stem defects were studied over 

an 18-year period to determine the 

effect of thinning intensity on quality 

development of 80-year-old white oak 

trees. Seventy-nine white oak trees 

from a thinning study in Kentucky 

were analyzed from stereo photographs taken in 1960 and 1978. Stemrelated defects were measured on the 

butt &foot and second 8-foot sections 

of each tree. The number of defects 

per square foot of surface area increased significantly at the heaviest 

thinning level. The data suggest that 

heavy thinning has a detrimental effect on potential stem quality. 

The Author 

David L. Sonderman, research 

forest product technologist, received 

a B.S. degree in forestry from West 

Virginia University in 1962. He joined 

the Northeastern Forest Experiment 

Station in June 1962, and was a member of the staff of the Eastern Softwood Timber Quality project until 

June 1972. Currently, he is with the 

Northeastern Station's project on 

Management and Utilization Alternatives for Nonindustrial Private Forests located at Delaware, Ohio. 

Manuscript received for 

publication 17 October 1983 
Introduction 

Forest managers have long been 

interested in increasing volume growth 

by the use of various silvicultural 

treatments. Emphasis has been on 

increasing tree diameter and height 

growth by regulating residual stand 

density, but there has been little regard for tree quality. In fact, tree quality is equally important to good volume 

growth because it provides high value 

end-products such as veneers and 

high-grade lumber. 

Documentation of research on the 

effects of stocking on growth rates 

is much more frequent than documentation of potential quality development. We found that white oaks 

responded quite differently from other 

hardwood species reported on. In one 

study, the relative change in stem 

quality of 33-year-old white oaks was 

affected by thinning intensities after 

16 years of treatment. The number of 

live and dead branches greater than 

0.3 inch in diameter had increased for 

all density levels, with the largest 

increase at the lowest density plots 

(Dale and Sonderman 1984). 

In a study on the response of 

young northern hardwoods in New 

Hampshire, Marquis (1969) found that 

after 5 years there was no reduction 

in quality due to treatment. In a study 

of the influence of stand density on 

stem quality of pole-size northern 

hardwoods, Godman (1971) found that 

during a 15-year period the average 

number of defects per tree did not 

change except in the type and position 

of the defects in the tower tree bole. 

Smith (1977) found that thinning to 

various tree-density levels did not 

influence epicormic branching in 

yellow-poplar after 8 years. 

In most of these studies the 

responses of individual tree characterist ics were observed independently. 

In this paper, we have included individual tree and quality characteristics 

that we believe are related to potential 

end-product classes. We are examining the relationship of time on the 

development of quality-related surface 

characteristics of trees grown at different levels of residual stand density. 

Research on hardwood quality has 

shown that species, age, crown ratio, 

and stand density are important factors that affect potential stem quality. 

Usually, limb-related defects and epicormic branches are the bole characteristics most affected by thinning 

treatments. In this paper, limb-related 

characteristics should be considered 

simultaneously to interpret the effect 

of stand density on their development. 
Methods 

Data were collected on sample 

trees from a thinning experiment on 

the Daniel Boone National Forest, 

Laurel County, Kentucky. In 1960, 

sixteen I-acre plots were established 

in an 80-year old white oak stand; 

isolation zones of chain surrounded 

each plot. Four plots each were thinned 

to a residual basal area of 20,40, and 

60 ft21acre, leaving four plots with approximately 80 ft2facre as the control. 

Minimum diameter of trees thinned 

from the plots was limited to 3.6 

inches. Originally, all plots were about 

the same in density, age, size class, 

species composition, and site quality. 

Before the initial cutting, the average 

basal area of the plots was 80 ft2/acre. 

The average age was 78, the average 

d. b. h. was 8.9 inches, and the average 

site index was 63. Tree vigor, spacing, 

size, and apparent quality based on 

form, straightness, and freedom of 

stem branches were the factors used 

for potential crop-tree selection. 

Five trees from each plot were 

selected at random to study the 

change in potential tree quality by the 

stereo-photo technique described by 

Sonderman (1980). Stereo-photographs 

were taken from the four cardinal 

directions around each of the study 

trees; subsequent stereo-photographs 

were taken after 18 growing seasons. 

In this analysis, 79 stereo-photo trees 

were studied from 8 by 10 stereophotographic enlargements taken in 

1960 and 1978. For each tree we recorded the d.b. h., total height, crown 

ratio, number and diameter of live and 

dead limbs, and number of epicormic 

branches. The trees also were classified by relative quality (Sonderman 

1979). Only the limb-related defects 

were recorded from the stereo-photographs. The remaining variables were 

measured or observed in the field in 

1960 and 1978. 

Limb-related variables were analyzed by covariance analysis. The 

value of the variable at the initial 

time was used as the covariate. 

Results and Discussion 

Growth 

Stand density affects the diameter, height growth, and crown ratio 

of trees in different ways. Heavy stand 

density (80 ft2 BA) seems to affect 

diameter growth more than height 

growth. Average diameter of the study 

trees after treatment was 10.59 inches 

in 1960 and 13.38 inches in 1978. Mean 

diameter growth increased by 2.8 

inches on all trees, with a 22-percent 

increase in diameter in the 80-ft2 plots 

and a 31-percent increase in the 20-ft2 

plots. Hiit (1979) found similar diameter-growth trends in relation to 

stocking, 

In this study, mean height growth 

was highest in the 60-ft2 plots, but 

was not significant due to treatment 

differences in a similar study by Dale 

and Sonderman (1984). 

Average crown ratio, considered 

one of the best indicators of the effects of stand density, increased in 

all treatments except the control. The 

crown ratio in the control plots (80 ft2) 

decreased by 7 percent and the crown 

ratio in the 20-ft2 plots increased 

by 64 percent. The increase in the 

20-ft2 plots was due to the development of additional epicormic branches, 

faster growth, and greater retention 

of branches. Dale and Sonderman 

(1984) reported highly significant differences between crown length and 

treatments. 

Limb Defects Per Square Foot 

of Surface Area 

Limb defects per square foot of 

surface area include all live and dead 

limbs and all overgrowths on the butt 

16-foot section of the tree. Analyzing 

the data by the number of defects per 

square foot of surface area provides a 

relative comparison of the effects of 

stocking on stem quality. Normally, 

expansion of the surface area will 

result in a decrease in the number of 

defects per square foot of surface 

area-if no new defects develop over 

time. The following tabulation shows 

the number of defects per square foot 

of surface area (butt 16-foot section): 

Residual basal area 

Year (f t 21acre) 

The high-density control plots 

are the only ones that show a decrease in average number of defects 

after 18 years. The decrease is due to 

the effect of natural pruning and to 

the lack of development of epicormic 

branches that is associated with 

dense stands. These plots had a 

14-percent decrease in the number of 

defects per square foot of surface 

area, and a 16-percent increase in surface area. In the 20-ft2 plots, there 

was a 33-percent increase in the number of defects per square foot of surface area and a 24-percent increase 

in surface area. 

Live Limbs 

Limbs that were alive and smaller 

than 0.3 inch in diameter were classified as epicormic branches and those 

0.3 inch or larger in diameter were 

classified as live or dead. The number 

of limbs was recorded for both the 

butt 8-foot and second 8-foot sections 

of each sample tree. In the butt 8-foot 

section, the number of live limbs and 

the percentage of trees with live limbs 

decreased at all density levels between 1960 and 1978 (Table 1). The 

greatest reduction was in the 60-ft2 

treatment, which had no trees with 

live limbs in the butt 8-foot section 

after 18 years. When comparing the 

two log sections, the second 8-foot 

section increased over the butt section in both the proportion of trees 

with live limbs and the number of live 

limbs (Table 1). There was an overall 

reduction in the percentage of trees 

with live limbs in the second 8-foot 

section at every density level from 

1960 through 1978. 

There was no statistically significant (P < 0.05) difference in the 

number of live limbs per tree on the 

butt 16-foot section after adjusting 
for the initial number of live limbs 

over the 18-year period. However, 

there was a trend to fewer live limbs 

per tree as stocking increased. It is 

apparent that the number of live limbs 

in the 20- and 40-ft2 treatments increased early in the treatment period, 

because there was an overall increase 

in the number of dead limbs in these 

same treatments. This increase in 

dead limbs developed from an increase in live limbs that subsequently 

died during the 18-year period. 

Diameter of Live Limbs 

In 1978, the average diameter of 

live limbs for the butt 8-fool section 

of the study trees was more than l/2 

inch. The exception was the 60-ft2 

plots, which had no live limbs (Table 

2). In the second 8-foot section, the 

size of the live limbs had fluctuated 

considerably by 1978--from 1 .I7 

inches in the 40-ft2 plots to a low of 

0.57 inch in the control plots (Table 2). 

As the density of the stand increased, 

the number and size of the live limbs 

decreased because of natural pruning 

and limited light. In this study, the 

diameter of live limbs increased by 

31 percent in the 40-ft2 plots and by 

less than 1 percent in the control 

plots. 

Table 1.-Percentage sf trees with live limbs in butt 

8-fool and second 8-foot sections, 1960-78 

Residual basal area (ft21acre) 

Number of 

live limbs 20 40 60 80 

-- 

BUTT 8-FOOT SECTION 

SECOND 8-FOOT SECTION 

Table 2.--Average diameter of live limbs in butt 

8-foot and second $-foot sections, 1960-78 

Residual basal area (ft21acre) 

Tree 

section 20 40 60 80 
Dead Limbs 

In all treatments, the percentage 

of trees with dead limbs increased in 

both 8-foot sections over the 18-year 

period (Table 3). The 20-ft2 plots had 

both the largest increase in the percentage of trees with dead limbs and 

the largest number of defects in both 

sections. By contrast, the controls 

had the smallest increase in the percentage of trees with dead limbs in 

both sections. 

The overall increase in number 

of dead limbs on the lower density 

plots resulted from the large increase 

in live limbs early in the treatment 

period. These live limbs died later in 

the treatment period. Dead limbs 

in the butt 16-foot section showed 

a significant difference between 

the 20-ft2 treatment and all other 

treatments (P < 0.05). The 20- and 

40-ft2 treatments were significantly 

greater than the 60- and 80-ft2 treatments (P < 0.1). There was no signif icant difference between the 60- 

and 80-ft2 treatments for the entire 

16-foot section. 

The development of a dense understory on the lower density plots 

explains some of the changes in the 

percentage of trees with dead limbs 

and the number of dead limbs. Initially, the open condition created in 

these plots promoted the development 

of epicormic branches. As the understory developed over the 18 years, it 

progressively blocked some of the 

direct sunlight from the butt 8-foot 

section of the tree, causing limb development to slow. Later, attaining a 

height of 25 to 30 feet, the understory 

began blocking sunlight from the entire 16-foot section and suppressing 

the existing limbs and epicormic 

branches. This resulted in different 

limb-related growth rates for each 

8-foot section of the tree. 

Diameter of Dead Limbs 

The average diameter of the dead 

iimbs on the butt 8-foot section was 

smaller than the average diameter of 

the dead limbs on the second 8-foot 

section (Tabte 4). The size of dead 

limbs generally increased as stand 

density decreased. 

The second 8-foot section, which 

encompassed part of the living crown, 

received more light and as a result 

had larger dead limbs than the lower 

8-foot section. The second 8-foot section of the trees in the 20-ft2 treatment 

had the largest dead limbs, increasing 

from 0.90 inch in 1960 to 1.53 inches 

in 1978. This 70-percent increase in 

the size of the dead limbs illustrates 

the effect of open stocking on limb 

development. Part of the increase in 

the size of dead limbs was caused by 

the lack of natural pruning, which 

allowed existing live limbs to remain 

on the tree and develop. By contrast, 

the size of dead limbs in the control 

plots was 0.72 inch in 1960 and only 

0.83 inch in 1978. 

Epicormic Branches in 

Both 8-Foot Sections 

Table 5 shows the changes in 

numbers of epicormic branches between 1960 and 1978 for the butt and 

second 8-foot sections. Three broad 

categories of epicormic branches were 

established (Sondsrman 1979): (1) trees 

with no epicormic branches, (2) trees 

with 1 to 6 epicormic branches, and 

(3) trees with 7 or more epicormic 

branches for each 8-foot section. 

On the butt 8-foot section, the lowest density treatment had about the 

same number of epicormic branches 

per tree after 18 years. The percentage 

of trees with epicormic branches also 

remained the same. At all other density levels there was a decrease in the 

number of epicormic branches per 

tree, and a similar reduction in the 

percentage of trees with epicormic 

branches. In the second 8-foot section, there was a 35-percent reduction 

in trees with epicormic branches in 

the lowest density plots. 

In the butt 8-foot section, the 

understory on the 20-ft2 plots began 

blocking the sunlight soon after thinning, causing epicormic branches to 

develop more slowly. As a result, the 

percentage of trees with epicormic 

branches remained about the same 

over the 18-year period. 

In the second 8-foot section, epicormic branches developed faster 

because of more light for a longer 

time. Eventually, the understory attained a height of 25 to 30 feet and 

began shading the second 8-foot 

section. However, the extra amount 

of sunlight had allowed the epicormic 

branches to grow into measureable 

bivo limbs, as evidenced by the significant increase in the number of 

dead limbs. 
Table 3.-Percentage of trees with limbs in butt 

8-foot and second El-foot sections, 1960-78 

Residual basal area (ft21acre) 

Number of 

dead limbs 20 40 60 80 

1960 1978 1960 1978 1960 1978 1960 1978 - 

BUTT 8-FOOT SECTION 

SECOND 8-FOOT SECTION 

Table &--Average diameter of dead limbs in butt 

8-foot and second 8=fost sections, 1960-78 

Residual basal area (ft21acre) 

Tree 

section 20 40 60 80 

Butt 8-foot 0.75 1.00 0.66 0.66 - 0.63 1.12 0.93 

Second 8-foot 0.90 1.53 0.80 1.1 1 0.85 0.88 0.72 0.84 

Table 5.-Percentage of trees with epicormic branches, 

butt 8=foot and second 8-foot sections, 1960-78 -- 

Residual basal area (ft21acre) 

Number of 

epicormics 20 40 60 80 

1960 1978 1960 1978 1960 1978 1960 1978 

BUTT 8-FOOT SECTION 

SECOND 8-FOOT SECTION 
Summary and Conclusion 

The information in this report 

shows important trends in stem quality and growth as related to different 

levels of residual stand density for 

white oak trees over time. It must be 

remembered that the individual characteristics are not independent of 

one another. For example, there is a 

pattern of epicormic branches changing to live limbs, live limbs changing 

to dead limbs, and dead limbs changing to overgrowths. All branch-related 

defects must be considered simultaneously to interpret the effect of 

stocking on their development. 

Results from this study ind'rzate 

that in white oak trees measured 

over time showed that: 

1. The number of defects per square 

foot of surface area decreased 

as the residual stand density increased. 

2. The second 8-foot section of the 

tree had more live limbs than the 

butt 8-foot section. 

3. Live limbs were substantially 

larger in the second 8-foot section 

of the tree. 

4. Both the proportion of trees with 

dead limbs and the number of 

dead limbs decreased as residual 

stand density increased. 

5. The average number of dead limbs 

increased almost 4 times from 

1960 to 1978 at the lowest density 

level. 

6. There were more epicormic branches 

in the second 8-foot section of the 

tree than in the butt 8-foot section. 

7. The percentage of trees with epicormic branches on the butt 8-foot 

section in the open 20-ft2 plots did 

not change. Yet, the percentage of 

trees with epicormic branches decreased in every other treatment 

for both 8-foot sections between 

1960 and 1978. 

Because this study was limited 

to a single species, site class, and 

age group, the results can be extrapolated to other species, site classes, 

and age groups only in very broad 

terms. 

Literature Cited 

Dale, Martin E.; Sonderman, David L. 

Effect of thinning on growth and 

potential quality of young white 

oak crop trees. Res. Pap. NE-539. 

Broomall, PA: U.S. Department of 

Agriculture, Forest Service, Northeastern Forest Experiment Station; 

1984. 12 p. 

Godman, Richard M.; Brooks, David J. 

Influence of stand density on stem 

quality in pole-size northern hardwoods. Res. Pap. NC-54. St. Paul, 

MN: U.S. Department of Agriculture, Forest Service, North Central 

Forest Experiment Station; 1971. 

7 P. 

Hilt, Donald E. Diameter growth of 

upland oaks after thinning. Res. 

Pap. NE-437. Broomall, PA: U.S. 

Department of Agriculture, Forest 

Service, Northeastern Forest Experiment Station; 1979. 11 p. 

Marquis, David A. "rinning in young 

northern hardwoods: 5-year results. 

Res. Pap. NE-169. Upper Darby, 

PA: U.S. Department of Agriculture, 

Forest Service, Northeastern Forest Experiment Station; 1969. 22 p. 

Smith, H. Clay. Changes in tree density do not influence epicormic 

branching of yellow-poplar. Res. 

Note NE-239, Upper Darby, PA: U.S. 

Department of Agriculture, Forest 

Service, Northeastern Forest Experiment Station; 1977. 3 p. 

Sonderman, D. L. Guide to the measurement of tree characteristics 

important to the quality classification system for young hardwood 

trees. Gen. Tech. Rep. NE-54. 

Broomali, PA: U.S. Department of 

Agriculture, Forest Service, Northeastern Forest Experiment Station; 

1979. 12 p. 

Sonderman, D. L. Using terrestrial 

stereo photography to interpret 

changes in tree quality characteristics. Res. Note NE-298. Broomall, 

PA: U.S. Department of Agriculture, 

Forest Service, Northeastern Forest Experiment Station; 1980. 8 p. 
Sonderman, David L. Quality response of even-aged 80-year-old 

white oak trees after thinning. Res. Pap. NE-543. Broomall, PA: 

U.S. Department of Agriculture, Forest Service, Northeastern 

Forest Experiment Station; 1984. 6 p. 

Stem defects were studied over an 18-year period to determine 

the effect of thinning intensity on quality development of 80-yearold white oak trees. Seventy-nine white oak trees from a thinning 

study in Kentucky were analyzed from stereo photographs taken 

in 1960 and 1978. Stem-related defects were measured on the 

butt 8-foot and second 8-foot sections of each tree. The number 

of defects per square foot of surface area increased significantly 

at the heaviest thinning level. The data suggest that heavy 

thinning has a detrimental effect on potential stem quality. 

ODC 228.1: 242: 851: 852.11 

Keywords: Silviculture; thinning; bole quality 

.- U S GOVERNtvlENT PRINTING OFFICE: 1984-705-0293'510 
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. 

@ Burlington, Vermont, in cooperation with the University of 

Vermont. 

@ Delaware, Ohio. 

@ Durham, New Hmphire, in cooperation with the University of 

New Hampshire. 

@ Hamden, Connecticut, in cooperation with Yale University. 

@ Morgmtown, West Virginia, in cooperation with West Virginia 

University, Morgmtown. * Brono, Maine, in cooperation with the University of Maine, 

Orono. 

@ Parsons, West Virginia. 

@ 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. 

@ Warren, Pennsylvania,