United States 

Department of 

Agriculture 

Changes in Hardwood 

Forest Service Growing-Stock Tree Grades 

Northeastern Forest 

Experiment Station 

Research Paper NE-608 

David L. Sonderman 

Everette D. Rast 
Abstract 

Describes changes in provisional tree grades for 351 young, mixed upland hardwood trees 6 years after thinning. Treatments of 30, 50, and 70 percent stocking 

plus a crop-tree release were applied. Results indicate that light thinning and 

crop-tree thinning produced higher quality and better grade trees than heavy 

thinning. 

The Authors 

DAVID L. SONDERMAN, research forest products technologist, joined the Northeastern Forest Experiment Station in 1962 and was on the staff of the Eastern 

Softwood Timber Quality project until 1972. From 1972 to 1987 he was located at 

Delaware, Ohio, with the Northeastern Station's project on management and utilization alternatives for nonindustrial private forests. He is currently with the 

Station's Forestry Sciences Laboratory at Princeton, West Virginia. 

EVERETTE D. RAST, research forest products technologist, received a B.S. 

degree in forestry from the University of Missouri in 1960 and an M.S. degree in 

agricultural economics from The Ohio State University in 1970. He joined the 

Forest Service in 1960 as a forester on the Mendocino National Forest and was 

located at the Northeastern Station's Delaware, Ohio, laboratory from 1966 to 

1987. He is currently with the Station's Forestry Sciences Laboratory at Princeton, 

West Virginia. 

Manuscript received for publication 23 February 1987. 

USDA Forest Service 

370 Reed Road, Broomall, PA 19008 

November 1987 
Introduction 

The United States has an estimated 230 billion cubic feet of 

hardwood growing-stock volume. With this much raw material, some measure of potential quality and associated grade 

change is needed to eventually predict the value. But to do 

this, we must first: (1) identify the potential quality trees, 

and (2) determine the type of cultural treatment needed to 

produce good-quality growth in the future. Recognizing 

these requirements, Boyce and Carpenter (1968) developed 

provisional grade specifications for young hardwood 

growing-stock trees. The grade specifications were 

assigned according to the probability of a young tree yielding a Grade 1, Grade 2, or Grade 3 butt log when it reached 

16 inches in diameter at breast height (d.b.h.). The grades 

were developed from tree-growth characteristics and stem 

defects located on the butt 16-foot log section. Many of the 

same growth characteristics and defect indicators were 

further quantified by Sonderman and Brisbin (1978), who 

developed a quality classification system that describes the 

relative quality of individual trees. More recently, Dale and 

Sonderman (1984) investigated growth and quality changes 

resulting from the effects of different thinning methods on 

white oak trees. These studies have produced a data base 

that can be used for future research on predicting tree quality in young growing-stock trees. 

This study compares quality and growth changes over time 

of hardwood. growing-stock trees by the provisional tree 

grades. Data on tree-grade changes provide a standard for 

evaluating how different tree species perform under different thinning treatments, and aid the forester and land manager in selecting the best thinning method. 

The Stands 

The study trees were located on four forest stands at the 

Vinton Furnace Experimental Forest in southeastern Ohio. 

The original stands contained mixtures of mature, evenaged, upland hardwood species on medium to good sites. 

One of the stands was clearcut in 1954 and the other three 

between 1959 and 1963. Before cutting, all of the stands 

were uniform with respect to site class, species composition, and quality. They differed only in age, which at the 

time of thinning was between 14 and 23 years. In 1977, the 

stands were thinned to 30,50, and 70 percent of full stocking according to Gingrich (1967), and a crop-tree release 

was established. All 88 plots, including the controls, were 

l/l0-acre in size. A 1/2-chain-wide isolation strip was 

placed around each treatment boundary and treated the 

same as the respective plots; 351 trees were measured in 

this study. At the time of thinning, species composition 

included mixed oaks, aspen, yellow-poplar, red maple, black 

cherry, black walnut, blackgum, butternut, beech, red elm, 

and hickory. Four species that represented the majority of 

the stands were grouped and used for the analyses. They 

were oak, yellow-poplar, red maple, and aspen. Miscellaneous species were not included in the analyses because of a 

small number of sample trees. 

Methods 

The selected trees were graded twice (1 977 and 1983) by 

the provisional grade specifications for hardwood growingstock trees (Boyce and Carpenter 1968). Specifications 

required tree d.b.h. to be 6.0 inches or larger and that each 

tree have a potential 12-, 14-, or 16-foot butt log. Each tree 

was graded and assigned to one of four provisional 

growing-stock tree grades (the fourth grade was added for 

trees not qualifying as Grade 1,2, or 3, but still meeting 

criteria for butt-log length). All of the grades were assigned 

according to the probability that a tree will yield a Grade 1, 

2, or 3 butt log when it reaches 16 inches in d.b.h. The provisional tree grades were defined as: 

Grade 1: Crown class must be dominant or codominant, up to 4 inches of sweep allowed, and up to four 

defects permitted.1 

Grade 2: Crown class must be dominant or codominant, up to 6 inches of sweep allowed, and 5 to 17 

defects permitted.1 

Grade 3: Admit all crown classes, up to 8 inches of 

sweep, and 18 to 30 defects permitted.1 

Grade 4: Include all trees not meeting Grade 1,2, or 3 

specifications but still meeting criteria for butt-log 

length.1 

For the analyses, the trees were grouped by species, treatment, provisional grade, and year measured. The differences in potential grade change between growth periods 

(years) were the basis for this paper. 

1Defects include limbs, overgrowths, knots, bud clusters, 

and bark distortions. Trees with any amount of rot or forks 

are automatically Grade 4. 
Results and Discussion 

This paper focuses on stem quality as reflected in potential 

tree-grade changes over time under different thinning 

treatments. However, tree growth is as important as tree 

quality since both are taking place at the same time. For 

instance, as a tree grows, the branches may develop into 

live limbs, the live limbs die, and the dead limbs become 

overgrowths. The speed of this process is controlled partially by stand density, age, and site. 

Oak 

The oaks species generally developed more stem defects 

from heavy thinnings and consequently had lower grades 

than some of the other species in this report. In fact, the 

open crown condition of the 30 percent treatment had an 

adverse effect on oak stem quality and grade (Fig. 1). 

Because of the many stem defects, there were no Grade 1 

oak trees in the 30 percent treatment. The percentage of 

Grade 2 oak trees declined and the proportion of Grade 3 

and Grade 4 trees increased. The percent decline in Grade 

2 trees was due to an increase in the number of stem 

defects resulting from excessive sunlight that caused many 

of the suppressed buds to sprout and "feather out" as new 

epicormic branches. At the same time, some of the existing 

live limbs continue to thrive in the sunlight and grow larger, 

adding to the number and seriousness of the stem defects. 

There were no Grade 1 oak trees in the 50 percent treatment for the same reasons as in the 30 percent treatmentexcessive stem defects. The percentage of Grade 2 oak 

trees did not change, but there was a slight increase in 

Grade 3 trees in this treatment. 

Figure 1.-Percent change in oak provisional tree grades, by treatment, 1977-83. 
For the same reasons cited, there were no Grade 1 oak trees 

in the 70 percent treatment; however, the proportion of 

Grade 2 oaks increased by about 7 percent, the Grade 3 oak 

trees remained constant, and the Grade 4 trees decreased. 

As thinning intensities decreased, there was a trend toward 

better tree grades for the oak species. 

The crop-tree release resulted in the greatest improvement, 

a 3-percent increase in Grade 1 trees and a 7-percent 

decrease in Grade 2 trees. Grade 3 crop trees increased 

slightly, but there was no change-in the percentage of 

Grade 4 trees. The croptree treatment, which favors dominant and codominant trees in the final stand, resulted in 

fewer epicormic branches from reduced sprouting that is 

associated with better crown classes. This supports previous studies that show an inverse relationship between 

crown dominance and sprouting. 

In the control plots, the natural pruning of the dead limbs 

resulted in fewer stem defects and a 10-percent decrease in 

Grade 4 oak trees. This percentage change was redistributed among Grade 2 and Grade 3 trees as an increase. 

There were no Grade 1 trees in the control. 

Many of these results are similar to those of a thinningintensity study (Sonderman 1984) that showed a loss of 

stem quality as a result of heavy thinning in 80-year-old 

white oaks. 

Yellow-Poplar 

Previous research has shown that yellow-poplar trees 

sprout with epicormic branches if exposed to heavy thinning. During this 6-year study period, several yellow-poplar 

in the 30 percent treatment (Fig. 2) did increase in quality to 

Grade 1. However, a larger proportion, more than 13 perFigure 2.-Percent change in yellow-poplar provisional tree grades, by treatment, 1977-83. 
cent, decreased from Grade 2 to Grade 3. Many of the 

original Grade 2 trees became Grade 3 trees because of an 

increase in the number of stem defects resulting from heavy 

thinning. The Grade 4 yellow-poplar trees in the 30 percent 

treatment were unchanged. 

There were no Grade 1 yellow-poplar trees in the 50 percent 

treatment. However, the effects of this thinning treatment 

resulted in no change in the proportion of Grade 2 trees, 

and only a slight increase in Grade 3 trees. This small 

increase in Grade 3 trees resulted from fewer stem defects 

in the Grade 4 trees after 6 years. 

The 70 percent treatment had a dramatic effect on the percentage of yellow-poplar Grade 1 trees-the proportion of 

these trees increased by 8 percent from 1977 to 1983. Many 

of these originally were Grade 2 trees that developed better 

quality and grade over time by losing a number of limb 

defects. There was no change in the proportion of Grade 3 

trees and a slight decrease in the proportion of Grade 4 

trees in the 70 percent treatment. 

The effects of crop-tree thining on yellow-poplar resulted in 

a substantial increase in Grade 1 trees, with an almost equal 

loss in Grade 2 trees. Obviously, they changed grade 

because of fewer stem defects. Yellow-poplar responded 

well to crop-tree thinning with very little sprouting of epicormic branches. The proportion of Grade 3 trees increased 

by about 2 percent and there were no Grade 4 trees. 

The results of the controls on yellow-poplar had an opposite effect from that of the crop-tree treatment. A small percentage loss of Grade 1 and Grade 2 trees was noted along 

with a &percent increase in Grade 3 trees. Most of the 

young trees in the control treatment grew closer together 

and were more uniform than in the other treatments, resulting in an overall lower crown dominance, smaller crown 

ratios, and fewer vigorous stems. These factors contributed 

to the increase in the proportion of Grade 3 trees, most of 

which originated from a combined change of Grade 1,2, 

and 4 trees. It should be noted that the self-pruning that did 

occur was offset by the growth factors cited. 

Red Maple 

Red maple trees usually are considered prolific epicormic 

sprouters when subjected to heavy thinnings. These heavy 

thinnings can be expected to deteriorate red maple quality 

(grade) over time as a result of an increase in the size and 

number of limb-related defects. The many defects that 

resulted from this sprouting help explain why there were no 

Grade 1 trees in the 30 percent treatment and why Grade 2 

and Grade 3 red maple trees (Fig. 3) increased only about 2 

percent each. Heavy thinning causes young red maple 

crowns to expand and extend downward, resulting in an 

increase in crown ratios. Over time, increases in crown ratio 

reflect the degrading effect that results from the development of excessive epicormic branches and live limbs. In 

addition to these changes in crown ratio, the losses in the 

percentage of Grade 4 red maple trees may also result from 

a change in crown class that was created by the heavy thinning and, thus, reflected in the grading specifications. 

There were no graded red maple trees in the 50 percent 

treatment. 

There were no Grade 1 red maple trees in the 70 percent 

treatment, but there was a 4-percent increase in Grade 2 

trees. The percentage of Grade 3 and Grade 4 trees 

decreased, probably as a result of the decrease in the 

number of limb defects. The combination of all of these 

changes resulted in better overall tree quality in the 70 percent treatment. 

Crop-tree thinning of red maples resulted in good volume 

growth and quality development. The increase in the percentage of Grade 1 trees was a direct result of less sprouting from dominant and codominant trees as opposed to the 

intermediate and suppressed trees. It is believed that genetically inferior trees (with regard to growth rate) tend to be 

found in the intermediate and suppressed crown classes, 

and that these trees tend to sprout more prolifically than the 

genetically superior trees (dominant and codominants). 

There were no Grade 1 red maple trees in the control. The 

percentage of Grade 2 red maples decreased and the percentage of Grade 3 red maples increased correspondingly. 

The formation of new epicormic branches, along with existing large live and dead limbs that do not prune-off easily or 

quickly, contributed to lower grades for red maple trees. 

Besides the number of limbs, some of the lower grades 

were caused by poorer crown classes in the control plots. 

Many of these crown classes were in the codominant and 

intermediate categories, which have lower quality factors in 

the provisional tree-grading specifications. 
Figure 3.-Percent change in red maple provisional tree grades, by treatment, 1977-83. 

Aspen Aspen, however, did show an increase in Grade 1 trees in 

Aspen is a short-lived species that does not respond well to the 50 percent, 70 percent, crop-tree treatments, and conthinning-whether heavy or light. Results from the 30 per- trol, but the grade increases resulted more from loss of 

cent treatment (Fig. 4) show no Grade 1 trees and a limbs from age than from the effects of thinning. Limbs on 

3-percent increase in Grade 2 trees. Many of the aspens in aspen trees between 20 and 30 years of age tend to die 

the poorer grades lost limbs during the 6-year study period, early or persist only for a few years under any stocking 

accounting for most of the changes. treatment. 
Figure 4.-Percent change in aspen provisional tree grades, by treatment, 1977-83. 

Summary and Conclusions 

The provisional tree-grade specifications for young 

growing-stock trees were based on crown position, stem 

form, and the number of surface-defect indicators. Comparing the data from 1977 and 1983 has shown a number of 

interesting changes. For example, the crown classes of 

many trees were changed by the thinning method applied. 

Heavy thinning tended to favor dominant and codominant 

trees in the redidual stands, many of which suffered from 

excessive epicormic branching and heavy limb retention. In 

the 30 and 50 percent treatments, for example, the additional limb defects resulted in lower overall tree quality and 

grade than those in the 70 percent treatment. In the croptree treatment, the greatest improvement was in the percentage of Grade 1 trees. Thinningaround young potential 

crop trees had a positive effect' o. the proportion of Grade 1 

trees because enough crown c er was maintained to partially shade the stem and still a p" low sufficient light for good 

growth. By contrast, the young trees in the control plots 

showed much slower diameter growth, almost equal height 

growth, more natural pruningl of smaller limbs, and poorer 

but more evenly distributed crowns. This resulted in the 

larger limbs remaining on the stem, fewer epicormic 

branches, slightly straighter boles, and little positive effect 

on grade change for the trees in the control. 
An overall look at all species combined by treatments (Fig. 

5) shows the largest increase in Grade 1 trees in the croptree treatment and the smallest change in the control. There 

was a gradual increase in Grade 1 trees as percent stocking 

increased. 

Other findings were: 

In the oak group, only the crop-tree release contained 

Grade 1 trees. 

Yellow-poplar was the only species with Grade 1 trees 

in the 30 percent treatment. 

There were no Grade 4 yellow-poplar trees in the 30 

percent or crop-tree treatments. 

In the red maple group, only the crop-tree treatment 

contained Grade 1 trees. 

There were Grade 1 aspen trees in all treatments 

except for the 30 percent treatment. 

The results indicate that the potential for growing Grade 1, 

high-quality, young hardwood trees increases with a 

decrease in thinning intensity. Thinning below 60 percent 

stocking has a detrimental effect on tree quality and grade. 

At this stocking level, a sufficient number of young trees will 

be able to fully utilize the site while maintaining good 

growth and quality. 

-9 

-)O 

3O%STOCKHG 

I 

50%STOCKHG 

I 

7O%STOCK)K; 

I 

CROP 

I 

TREE 

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CONtROl 

Figure 5.-Percent change in provisional tree grades for all species combined, by treatment, 1977-83. 
Literature Cited 

Boyce, Stephen G.; Carpenter, Roswell D. 1968. Provisional 

grade specifications for hardwood growing-stock trees. 

Res. Pap. NE-97. Upper Darby, PA: US. Department of 

Agriculture, Forest Service, Northeastern Forest Experiment Station. 12 p. 

Dale, Martin E.; Sonderman, David L. 1984. Effect of thinning on growth and potential quality of young white oak 

trees. Res. Pap. NE-539. Broomall, PA: US. Department 

of Agriculture, Forest Service, Northeastern Forest Experiment Station. 12 p. 

Gingrich, S. F. 1967. Measuring and evaluating stocking and 

stand density in upland hardwood forests in the central 

states. Forest Science. 13:38-52. 

Sonderman, David L. 1984. 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. 

6 P. 

Sonderman, David L.; Brisbin, Robert L. 1978. A quality 

classification system for young hardwood trees-the first 

step in predicting future products. Res. Pap. NE-419. 

Broomall, PA: US. Department of Agriculture, Forest 

Service, Northeastern Forest Experiment Station. 7 p. 

*U. 5. GOVERNMENT PRINTING OFFICE: 1987/748-076/60004 
Sonderman, David L.; Rast, Everette D. 1987. Changes in hardwood 

growing-stock tree grades. Res. Pap. NE-608. Broomall, PA: U.S. 

Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 8 p. 

Describes changes in provisional tree grades for 351 young, mixed upland 

hardwood trees 6 years after thinning. Treatments of 30,50, and 70 percent 

stocking plus a crop-tree release were applied. Results indicate that light 

thinning and crop-tree thinning produced higher qualitjl and better grade 

trees than heavy thinning. 

ODC 228.1 :242:851:852:11:854 

Keywords: Stand density; thinning; stem quality; grade 
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. 

0 Berea, Kentucky, in cooperation with Berea College. 

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0 Delaware, Ohio. 

Durham, New Hampshire, in oooperation with the University of New Hampshire. 

Hamden, Connecticut, in cooperation with Yale University. 

Morgantown, West Virginia, in cooperation with West Virginia University, 

Morgantown. 

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

Parsons, West Virginia. 

Princeton, West Virginia. 

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. 

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