United States 'w Department of 

Agriculture Crop-Tree Release Increases 

Forest Service Growth of I 2-Year-Old 

Northeastern Forest 

Experiment Station Yellow-Poplar and Black Cherry 

Research Paper NE-622 

@ Neil I. Lamson 

H. Clay Smith 
Abstract 

Prewmmercial thinning was done in a 12-year-old Appalachian hardwood sapling 

stand in West Virginia. Two crop-tree release techniques were used-crown 

touching and crown touching plus 5 feet. Results indicated that both treatments 

significantly increased &year d.b.h. growth for released yellow-poplar and black 

cherry crop trees. Although there was a major increase in d.b.h. growth, caution is 

suggested when using the crown-touching plus 5 feet treatment as butt-log quality 

response was not conclusive. Releasing crop trees with the crown-touching 

approach seems appropriate in sapling stands when applied to desirable stems on 

better sites. 

The Authors 

NEIL I. LAMSON, research forester, received B.S. and M.S. degrees in silviculture 

and forest soils from the State University of New York, College of Environmental 

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

Private Forestry, in 1972. Currently he is engaged in research on the 

measurement, analysis, and modeling of forest tree and stand growth in the 

Northeast at the Northeastern Forest Experiment Station" Forestry Sciences 

Laboratory at Durham, New Hampshire. 

H. CLAY SMITH is Project Leader of research on the growth and culture of 

central Appalachian hardwoods at the Northeastern Station's Timber and 

Watershed Laboratory at Parsons, West Virginia. He received degrees from West 

Virginia University and Purdue University, and has been engaged in timber 

management research with the USDA Forest Service since 1962. 

-- -- -- 

Manuscript received for publication 6 March 1989 
Introduction 

Crop-tree release is the recommended prebommercial 

treatment for hardwood stands (Smith and Lamson 1986). 

This paper reports the 5-year growth of relbased 

yellow-poplar and black cherry crop trees in a 12-year-old 

Appalachian hardwood stand in West Virginia. 

There are two general methods used to release individual 

crop-treeea tree bole to tree bole release and a crown 

release. For this study, we used a crown release. This 

method involves the crown-touching concept, that is, cutting 

any tree in the intermediate, codominant, or dominant crown 

class whose crown intersects the drip edge of a crop-tree 

crown (except in the case of another crop tree). This is a 

practical way to ensure that a particular desirable tree is 

released. 

Study Methods 

The study was established in a 12-year-old Appalachian 

hardwood stand near Parsons, West Virginia. The stand 

was predominatly yellow-poplar (Liriodendron tulipifera L.) 

and black cherry (Prunus serotina Ehrh.), with a northern 

red oak (Quercus rubra L.) site index of 77 feet. Annual 

precipitation for the local area averages 55 inches and the 

growing season averages 145 frost-free days. The 

12-year-old stand originated after a clearcut in which all 

trees 1.0 inches and larger in diameter at breast height 

(d.b.h.) were cut. 

Six plots, each one-quarter acre in size, were established 

in fully stocked portions of the study stand during February 

1983. All live trees at least 1.0 inches d.b.h. were 

permanently identified on the plots. Species, d.b.h., crown 

class, and tree condition (e.g., dead top, insect damage) 

were recorded for each tree. During March 1983, 80 

yellow-poplar or black cherry crop trees per acre were 

selected on each plot (20 crop trees on each plot). A crop 

tree was defined as a condominant stem of a commercial 

species which had: 1) no main-stem fork in the lower 25 

feet of the bole, 2) no evidence of insect or disease 

damage, and 3) a vigorous, healthy crown, and 4) potential 

for a butt log grade 1 or 2. 

After the crop trees were selected, a crown-release 

treatment was assigned randomly to each plot-two plots 

per treatment. The treatments were control, crown-touching 

release (T), and crown-touching plus 5-foot release (T+5). 

The T treatment consisted of cutting all trees whose crowns 

either touched a crop-tree crown or inteicepted the drip 

edge of a crop-tree crown. Depending on the number of 

selected crop trees, there usually were several noncrop 

trees left in a precommercial stand after release. The T+5 

treatment consisted of cutting all trees whoke crowns were 

within 5 feet of a crop-tree crown. With the~+5 method, 

there were few to no intermediate, codomiiant or dominant 

noncrop trees in the stand after release; only crop trees 

were present. We realize this latter treatment was a drastic 

release for young stems. Our purpose was to determine 

how much is too much. D.b.h. growth and reductions in 

stem quality should be near maximum for this treatment. 

After the plots were marked, all trees to be cut were - 

recorded. 

Additional crop trees were selected outside the plots to 

make a total of at least 30 individual crop trees in each 

treatment for both yellow-poplar and black cherry. The crop 

trees outside the plots received the same treatments as 

those on the plots. 

In April 1983, the crop trees were released by felling 

competing trees with a chain saw (Fig. 1). After release, 

detailed measurements were taken for each crop tree. 

These included length of clear stem, height to base of live 

crown, total height, crown width, and crown growing space. 

Length of clear stem was measured as the height to the 

first live branch at least 1 foot long. Base of live crown was 

measured as the height to the first live branch that was not 

an epicormic branch. Crown width was measured along the 

four cardinal radii by estimating the point of the drip edge 

of the crop-tree crown and measuring the distance from the 

crop-tree bole with a tape. Crown growing space was 

measured similarly along the four cardinal radii as the 

distance between the drip edge of the crop tree and the 

closest adjacent tree. Length of clear stem, height to base 

of live crown, and total height were measured with a 

telescopic measuring pole. 

The six plots were reinventoried five growing seasons after 

treatment. Crown class and d.b.h. were recorded for each 

permanently identified tree and ingrowth trees (1.0-inch 

d.b.h. threshold). Crop-tree measurements of length of 

clear stem, base of live crown, total height, crown width, 

and crown growing space were repeated. Data from the 

quarter-acre plots were used to compute per-acre growth. 

Data from all of the crop trees, both on and off the plots, 

were summarized to compute average individual crop-tree 

growth. Analysis of variance and Tukey's multiple range 

test were used to test differences between treatments at 

the 1 percent level. 

Results 

Before treatment, basal area averaged about 75 ft2 per acre 

in 2,840 stems per acre (1 .O + inch d.b.h.). The T treatment 

reduced basal area from 75.6 to 43.1 ft2 per acre, while the 

T+5 treatment reduced basal area from 66.4 to 19.7 ft2 per 

acre (Table 1). Five-year net basal-area growth averaged 

36.3, 42.4, and 36.1 ft2 per acre for the control, T, and T+5 

treatments, respectively. 
Figure 1 .-Releasing 12-year-old yellow-poplar and black cherry crop trees by the crown-touching technique: 

before release (top) and after release. 
D.b.h. growth of individual crop trees was significantly increased d.b.h. growth by 72 percent over control. For 

increased by both release treatments (Table 2). For black cherry, 5-year d.b.h. growth was 1.3, 2.1, and 2.4 

yellow-poplar, 5-year d.b.h. growth was 2.1, 2.8, and 3.6 inches for control, T, and T+5, respectively. D.b.h. growth 

inches for control, T, and T+5, respectively. The T was increased 62 and 85 percent by the T and T+ 5 

treatment increased d.b.h. growth by 33 percent, while T+5 treatments, respectively. 

Table I .-Stand data before, immediate!^ after, and 5 years after crop-tree release 

Control Crown-touching release Crown-touching + 5 release 

Item 1.0-2.9 3.0-4.9 5.0 + Total 1.0-2.9 3.0-4.9 5.0 + Total 1.0-2.9 3.0-4.9 5.0+ Total 

Before Treatment 

Treeslacre (no.) 2774 398 44 3216 2224 390 60 2674 2248 352 28 2628 

BNacre (ft2) 44.5 29.1 8'.6 82.2 36.4 28.8 10.4 75.6 35.1 26.4 5.0 66.5 

Cut for Treatment 

Treeslacre (no.) 0 0 0 0 888 186 24 1098 1664 224 20 1908 

BNacre (ft2) 0 0 0 0 14.5 13.8 4.1 32.4 26.8 16.2 3.7 46.7 

Residual 

Treesiacre (no.) 2774 398 # 3216 1336 204 36 1576 584 128 8 720 

BNacre (ft2) 44.5 29.1 8.6 82.2 21.9 15.0 6.2 43.1 8.3 10.1 1.3 19.7 

5 Years Later 

Treestacre (no.) 1560 702 170 2432 1168 478 134 1780 1304 186 112 1602 

BNacre (ft2) 28.6 53.8 36.0 118.4 16.7 37.7 31.1 85.5 16.3 14.225.2 55.7 

5-year Net Growth 

BNacre (v) 36.2 42.4 36.0 

Table 2.-Crop tree grohth by treatment 

Yellow-poplar Black cherry I 

Crown- Crown- , Crown- touching Crown- touching 

touching +5 touching +5 

Item Control release release Control release release 

I 

No. of Trees 31 30 32 29 34 34 

Initial D.b.h. (inches) 3.9 3.6 3.8 3.9 3.8 3.6 

D.b.h. 5 years later 6.0 6.4 7.4 5.2 5.9 6.0 

5-year growth 2.1 a 2.8b 3.6~ 1.3a 2.1 b 2.4~ 

Initial Clear Stem (ft) 17.0 16.9 17.3 17.0 16.2 15.4 

Clear stem 5 years later 25.2 19.8 16.6 24.5 18.7 17.0 

5-year change 8.2a 2.9b -0.7~ 7.5a 2.5b 1.6b 

Initial Base Live Crown (ft) 19.6 19.2 18.8 20.6 19.9 17.7 

Base live crown 5 years later 25.3 20.8 17.7 24.5 20.3 17.7 

5-year change 5.7a 1.6b -1.1~ 3.9a 0.4b O.Ob 

Initial Total Height (ft) : 35.1 32.9 33.5 35.8 35.1 32.8 

Total height 5 years later I 49.3 46.7 44.2 46.8 44.0 40.8 

5-year growth 14.2a 13.8a 10.7b 11.0a 8.9b 8.0b 

Initial Crown Diameter (ft) 9.4 8.0 9.0 10.6 9.8 10.4 

Crown diameter 5 years later 13.4 17.0 20.4 12.6 18.6 19.6 

5-year change 4.0a 9.0b 11.4~ 2.0a 8.8b 9.2b 

Initial Growing Space (ft) 0.0 4.4 9.8 0.0 4.9 9.5 

Growing space 5 years later 0.0 1 .O 5.3 0.0 1 .O 5.5 

5-year change 1 O.Oa -3.4b -4.5~ O.Oa -3.9b -4.0~ 

NOTE: For each species, means in the same row followed by the same letter are not significantly 

different, P > 0.01; Analyses done using Tukey's multiple range test. 
Crop-tree release significantly slowed the rate of increase of 

length of clear stem (Table 2). For the controls, length of 

clear stem increased by 8.2 and 7.5 feet in 5 years for 

yellow-poplar and black cherry, respectively. For the T 

treatment, length of clear stem increased by only 1.6 feet for 

yellow-poplar and 0.4 feet for black cherry; for the T+ 5 

treatment, length of clear stem decreased by 0.7 foot in 5 

years for yellow-poplar and by only 1.6 feet for black cherry. 

Five years after treatment, length of clear stem for both 

species averaged 24.8 feet for controls, 19.3 feet for T, and 

16.8 feet for T + 5. 

Five-year height growth was decreased 2 to 3 feet by 

crop-tree release. For yellow-poplar, height growth averaged 

14.2, 13.8, and 10.7 feet for control, T, and T + 5, 

respectively. The T+ 5 release resulted in significantly less 

height growth than the other treatments. For black cherry, 

5-year height growth was 11 .O, 8.9, and 8.0 feet, for control, 

T, and T+5, respectively. However, in this instance, both 

the T and T+ 5 treatments produced significantly lower 

5-year height growth in black cherry compared to control 

trees. 

Crown diameter was significantly increased by crop-tree 

release. During the 5 years after treatment, crown diameter 

of yellow-poplar increased by 4.0, 9.0, and 11.4 feet for 

control, T, and T+ 5, respectively. During the same period, 

crown diameter of black cherry increased by 2.0, 8.8, and 

9.2 feet, for control, T, and T+5 treatments, respectively 

(Table 2). The released crop trees of both species showed 

an increase in crown diameter of about 2 feet per year. 

Crown growing space immediately after release of both 

species combined averaged about 4.6 and 9.6 feet for the T 

and T+5 treatments, respectively. Five years later, the 

T-released crop trees had an average of 1.0 foot of crown 

growing space, while the T+5 crop trees had an average of 

5.4 feet of crofin growing space. Crown growing space 

around all released trees decreased by about 4 feet in 5 

years. 

Discussion 

Net stand basal-area growth was not decreased by either of 

the crop-tree release treatments. Even though basal area in 

the T+5 treatment was reduced from 66.4 to 19.7 ft2 per 

acre, the 5-year net basal area growth was 36.1 ft2 per 

acre, or only 0.2 foot less than the control. It appears that 

this heavy thinning was not severe enough to reduce the 

stand below its biological potential. 

Stand growth was shifted onto fewer more desirable stems, 

which is a major objective of intermediate stand treatments. 

Stand basal-area growth was not reduced by thinning even 

though there were more than 3 times as many stems on 

the control plots as on the T+5 plots. For stems more 

than 3.0 inches d.b.h., the control plots averaged 442 

stems per acre, while the T and the T+ 5 plots had 240 

and 136 stems per acre, respectively. 

Crop-tree release studies in 7- and 9-year-old stands in 

West Virginia, with height of codominant stems averaging 

less than 25 feet, showed that yellow-poplar and black 

cherry crop trees did not respond to a 5-foot radius bole 

release (Smith 1977). Wendel and Lamson (1987) showed 

that 8-year-old black cherry crop trees responded to a 5-foot 

bole release when the competition was killed by injecting 

herbicide. It is possible that rapid resprouting of cut stems 

negated the effects of a crop-tree release reported by Smith 

(1977). In this study, the crop trees were 12 years old and 

about 35 feet tall. The T treatment resulted in a 6.5-foot 

radius bole release, while the T + 5 treatment resulted in a 

11 .l -foot-radius bole release. This study supports Smith and 

Lamson's (1986) recommendation that when using a 

crown-touching release, wait until the codominants are at 

least 25 feet tall before releasing crop trees. However, we 

are not aware that a T+5 treatment has been used to 

release codominant crop trees that are less than 25 feet tall. 

Figure 2 shows the effect of crop-tree release on total 

height and crown development. During the 5-year period, 

the control trees grew about 13 feet taller and the height to 

base of live crown increased by about 5 feet. Although 

height growth was decreased by both release treatments, 

the released trees clearly have more crown area than the 

control trees. This increase in crown area translated into an 

increase in d.b.h. growth. It is likely that released crop trees 

will experience increased d.b.h. growth for 5 to 10 more 

years because of their crown area. 

Epicormic branching was not serious even in the T+ 5 crop 

trees. The only crop trees that decreased in length of clear 

stem or height to base of live crown were T+ 5 

yellow-poplar. Only 5 of 32 T + 5 yellow-poplar produced 

epicormic branches below the base of the live crown and 

most of these will not persist. 

Length of clear stem of the T crop trees was about 5 feet 

less than that of the controls; for T-l- 5 crop trees, it was 7 to 

8 feet less than that of control crop trees. Yellow-poplar 

T+5 crop trees had the shortest length of clear stem, 16.6 

feet. There is little doubt that these crop trees will have a 

clear stem of at least 25 feet after the stand begins to close 

in another 5 to 10 years. 

The growing space around released crop-tree crowns 

decreased at about the same rate (4 feet in 5 years) for 

both the T and T+5 treatments. At this rate, crown closure 

around crop trees should occur in another 1 or 2 years for 

T crop trees, and in another 4 to 5 years for T+5 crop 

trees. Assuming that the released trees will continue to 

have a slight increased d.b.h. growth rate for a few years 

after closure, it is possible that the d.b.h. of T crop trees 

will be about 1.5 inches larger than that of the controls. 

The d.b.h. of T+5 crop trees will be about 2 to 3 inches 

larger than that of the controls. 
INITIAL LKK)(] 

FIVE YEARS = 

TOTAL BASE 

CROWN I TOTAL BASE CROWN TOTAL BASE CROWN 

l€Ml UVECROWN~l HO(3HT LIE CROWN DIAETER HWM UVECROWNUAMETER 

CROWN 

TOUCHING 

CROWN 

TOUCHING(T*~) 

Figure 2.-Effect of a crop-tree release on tqal height, crown width, and height to base of live crown. 

The cost of the T treatment was about $0.42 per tree, or 

$33.60 per acre (Miller 1984). Miller (1986) estimated that 

for an investment period of 70 years and a current real 

stumpage price of $100 per 1,000 board fdet, it would take 

an increase in d.b.h. of 1.75 inches on 60 brop trees per 

acre to return 4 percent on an investment of $33.60. It 

appears that the T treatment will return nearly 4 percent on 

the investment, even if invested for 70 years. Of course, 

releasing fewer crop trees per acre would be a means of 

ensuring a high rate of return. 

nearly twice that of the T release. 

reasonable estimate of cost for 

I 

In general, height growth of nonreleased crop trees is 

significantly greater than that of released crop trees, though, 

total height growth is not a concern at this stage of stand 

development. Quality merchantable height has been 

established and the remainder of the merchantable stem will 

be primarily of low quality due to log diameter. No additional 

precommercial thinning treatments are plannad for the study 

areas. These stands will have at least two more commercial 

thinnings before the final harvest cut. These managed 

stands could be reduced from the present 80 crop trees per 

acre to about 30 crop trees per acre 15 to 20 years before 

the final harvest cut. 
Summary treatment, at this time we urge caution in recommending 

Both a T and a T+5 crop-tree release increased d.b.h. this treatment. It is too early to evaluate butt-log quality 

response as these results are not conclusive. After 5 years, growth of 12-year-old yellow-poplar and black cherry during understory growth has responded rapidly as several of the the first 5 years after treatment. D.b.h. growth increased by 

as much as 66 percent for the T release and 85 percent for butt logs already are receiving protection and shade from 

the T+5 release. Height growth was slowed by both the understory stems. Also, because of the intensity of the 

treatments, as was the rate of increase of length of clear overstory removal, the new understory, largely of sprout 

stem. However, it is expected that even the most heavily origin, will rapidly develop into a fourth-growth stand. In 

released crop trees eventually will develop a length of clear hardwood trees, a significant portion of the tree 

stem of at least 25 feet. volume-value is in the butt log. If management goals are to 

grow one quality 16-foot butt sawlog per tree in a short , 

period, this technique may be practical. 

The T crop-tree release may increase the d.b.h. of released 

trees by about 1.5 inches, while the T+5 crop tree release Thus, a crown-touching crop-tree release (T) seems 

will likely increase d.b.h. by as much as 3 inches. Although appropriate in 12-year-old Appalachian hardwood stands 

there was a major increase in d.b.h. growth with the T+5 when applied to desirable species on better sites. 
Literature Cited 

Miller, Gary W. 1984. Releasing young hardwood crop 

trees-use of a chain saw costs less than herbicides. 

Res. Pap. NE-550. Broomall, PA: U.S. Department of 

Agriculture, Forest Service, Northeastern Forest 

Experiment Station. 5 p. 

Miller, Gary W. 1986. Cultural practices on Appalachian 

hardwood sapling stands-are they worthwhile? In: 

Smith, H. Clay; Eye, Maxine C., eds. Proceedings, 

guidelines for managing immature Appalachian hardwood 

stands. 1986 May 28-30; Morgantown, WV. SAF Publ. 

86-02. Morgantown, WV: West Virginia University Books: 

33-45. 

Smith, H. Clay; Lamson, Neil 1. 1986. Cultural practices on 

Appalachian hardwood sapling stands--if done, how 

to do them. In: Smith, H. Clay; Eye, Maxine C., eds. 

Proceedings, guidelines for managing immature 

Appalachian hardwood stands. 1986 May 28-30; 

Morgantown, WV. SAF Publ. 86-02. Morgantown, WV: 

West Virginia University Books: 46-61. 

Smith, H. Clay. 1977. Results of precommercial thinning 

in very young Appalachian hardwood stands. Northern 

Logger. 24: 24-25. 

Wendel, G.W., Lamson, Neil 1. 1987. Effects of herbicide 

release on the growth of 8- to 12-year-old hardwood 

crop trees. Res. Pap. NE-598. Broomall, PA: US. 

Department of Agriculture, Forest Service, Northeastern 

Forest Experiment Station. 4 p. 
Lamson, Neil I.; Smith, H. Clay. 1989. Crop-tree release increases 

growth of 12-year-old yellow-poplar and black cherry. Res. Pap. 

NE-622. Broomall, PA: US. Department of Agriculture, Forest Service, 

Northeastern Forest Experiment Station. 7 p. 

Precommercial thinning was done in a 12-year-old Appalachian hardwood 

sapling stand in West Vriginia. Two crop-tree release techniques were 

used--crown touching and crown touching plus 5 feet. Results indicated that 

both treatments significantly increased 5-year d.b.h. growth for released 

yellow-poplar and black cherry crop trees. Although there was a major 

increase in d.b.h. growth, caution is suggested when using the 

crown-touching plus 5 feet treatment as butt-log quality response was not 

conclusive. el easing crop trees with the crown-touching approach seems 

appropriate in sapling stands when applied to desirable stems on better 

sites. 

ODC 242:236.1:1'76.1 

Keywords: Appalachian hardwoods, saplings, crown touching, yellow-poplar, 

black cherry. ; 
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. 

0 Hamden, Connecticut, in cooperation with Yale University. 

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

Morgantown. 

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

0 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. : 

0 University Park, Pennsylvania, in cooperation with the Pennsylvania State 

University. 

Warren, Pennsylvania. 

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