United States 

Department of 

Agriculture 

Forest Service 

Southern 

Research Station 

Research Note 

SRS-13 

First-Year Growth and Quality 

Response of Residual Hardwood 

Poletimber Trees Following Thinning 

in an Even-Aged Sawtimber Stand 

Daniel A. Skojac, Jr., Andrew W. Ezell, 

James S. Meadows, and John D. Hodges 

Febsuary 2007 

Abstract 

First-year diameter growth and epicormic branching responses of hardwood poletimber trees retained following thinning in a sawtimber stand - are reported. Poletimber trees were classified as either superior or inferior 

poletimber, and then retained on separate plots receiving identical thinning 

treatments. Comparison of responses by the two classes of poletimber was 

used to evaluate their future potential for grade sawtimber in the thinned 

sawtimber stand. Thinning treatments included an unthinned control, 

two levels of the desirable treatment (retained preferred and desirable 

sawtimber and either superior or inferior poletimber), and two levels 

of the acceptable treatment (retained preferred, desirable, and acceptable sawtimber and either superior or inferior poletimber). Preliminary 

results indicated that future sawtimber production from residual superior 

poletimber trees may be a realistic option but appears less likely from 

their inferior poletimber counterparts. The desirable treatment yielded 

significant first-year dianieter growth of superior poletimber trees (0.20 

inches), but also stimulated greater production of new epicormic branches 

on the potentially more valuable superior poletimber trees. The acceptable 

treatment minimized the production of epicormic branches on superior 

poletimber trees (only 2.2 new branches) during the first year. 

Key words:*Diameter growth, epicormic branching, hardwood. 

poletimber, thinning, tree class. 

Introduction 

Poletimber trees (5.5 to 12.5 inches diameter at breast 

height [&b.h.]) are usually abundant in the midstory of 

most previously unmanaged even-aged bottomland hardwood sawtimber stands. Many of these trees are in poor 

health and of low quality and have no potential for grade 

sawtimber production. To improve stand health and quality, 

these trees are typically removed during thinning for pulpwood. Fewer scattered poletimber trees in these stands 

are of good form and quality and exhibit potential to yield 

sawlogs. The most effective and profitable utilization of 

these trees, however, is arguable. Should these trees be 

removed for pulpwood as well, or if they are retained, can 

they reasonably be expected to yield sawlogs by rotation 

age? Retention of these trees poses no risk to their current 

merchantability. If thinning fails to yield'grade sawtimber 

from these trees, as a product, they remain pulpwood. 

However, if they develop a grade sawlog before the end of 

the rotation, their value and the value of the residual stand 

is dramatically increased. Alternatively, removal of these 

trees provides immediate compensation in the form of 

pulpwood, whereas future sawtimber production, though 

more profitable, is not guaranteed. Those poletimber trees 

favored during thinning must compete for site resources 

with larger sawtimber neighbors, while preserving bole 

quality under reduced stand density levels. Poor growth 

history and susceptibility to epicormic branching may 

prevent these trees from producing a grade sawlog. Given 

this uncertainty, practical guidelines for poletimber retention are needed when planning thinning operations in these 

even-aged sawtimber stands. 

A new system of tree classes' developed for the management 

of southern hardwoods attempts to separate poletimber 

trees based on their potential for sawtimber production, 

and could be used as a guide when selecting poletimber 

trees for retention following thinning in sawtimber stands. 

This new system expands Putnam's (Putnam et al. 1%0) 

set of four tree classes to five tree classes used exclusively 

for sawtimber (in descending order of desirability): (1) 

preferred growing stock, (2) desirable growing stock, (3) 

acceptable growing stock, (4) cutting stock, and (5) cull 

Daniel A. Skojac, Jr.. Forestry Technician, and James S. Meadows, 

Principal Silviculturist, USDA Forest Service, Southern Research Station, ' Meadows, J.S., Skojac, D.A. A new tree classification system for southern 

Southern Hardwoods Laboratory, Stoneville, MS 38776; Andrew W. Ezell, hardwoods. Manuscript in preparation. Authors can be reached at U.S. 

Professor of Forestry, and John D. Hodges, Professor Emeritus, Depart- Depament of Agriculture Forest Service, Southern HardwDods Laboratory, 

ment of Forestry, Mississippi State University. Starkville, MS 39762. PO. Box 227. Stoneville. MS 38776. 
stock; and creates two additional classes for poletimber: 

(1) superior poletimber stock and (2) inferior poletimber 

stock. Under the new system, superior poletimber trees 

must be of a desirable or acceptable species for the site and 

management objectives, be in good condition, pose little 

risk of mortality or degrade, and have the potential to make 

a Grade 2 or better butt log when minimum diameter limits 

are reached. Inferior poletimber trees are believed to have 

little potential for sawtimber production and are incapable 

of meeting Grade 2 butt log requirements when sawtimber 

diameters are reached. These trees should be removed 

during the next entry into the stand because they are of an 

undesirable or unmerchptable species, are in poor condition, pose serious risk of mortality or degrade, or exhibit 

symptoms of disease. 

Utilizing this new tree classification system, a study was 

initiated to determine the potential of poletimber trees to 

produce grade sawtimber following various levels of thinning in an even-aged bottomland hardwood sawtimber 

stand. First-year growth and quality response of residual 

poletimber trees are reported. 

Site Description 

The experiment was conducted in an even-aged bottomland 

hardwood stand within the alluvial floodplain of the Red 

River, on Barksdale Air Force Base in southwestern Bossier 

Parish, in northwestern Louisiana. The study site is part 

of a larger 188-acre stand that was approximately 60 to 65 

years old at the time of study establishment. Prior to treatment, the stand averaged 119 trees (75 poletimber trees) and 

110 square feet (30 square feet in poletimber) of basal area 

per acre in trees 5.5 inches and larger at d.b.h. Quadratic 

mean d.b.h. was 13.1 inches. Average stand stocking was 

92 percent (Goelz 1995). Stand basal area consisted of 47 

percent red oak [cherrybark oak (Quercus pagoda Raf.), 

Nuttall oak (Q. nuttallii Palmer), water oak (Q. nigra L.), 

and willow oak (Q. phellos L.)], 38 percent sweetgum 

(Liquidambar styracijlua L.), and 15 percent other species, 

primarily pecan [Carya illinoensis (Wangenh.) K. Kwh] 

and American elm (Ulmus americana L.). The study area 

contained nearly equal areas of both Peny clay (very-fine, 

smectitic, thermic Chromic Epiaquerts) and Gallion silt-loam 

(fine-silty, mixed, superactive, thermic Typic Hapludalfs) 

(U.S. Department of Agriculture Soil Conservation Service 

1%2, U.S. Department of Agriculture Natural Resources 

Conservation Service 2003). Site indices based on the Baker 

and Broadfoot (1979) site evaluation method were estimated 

as 104 feet for cherrybark oak, 97 feet for water and willow 

oak, 94 feet for Nuttall oak, and 107 feet for sweetgum. 

Procedure 

In December of 2003, the following five treatments were 

applied to 2.0-acre plots measuring five by four chains 

and replicated three times in a randomized complete block 

design: (1) unthinned control, (2) desirable growing stock 

with superior poletimber (DesSupP), (3) desirable growing 

stock with inferior poletimber (DesInfP), (4) acceptable 

growing stock with superior poletimber (AccSupP), and 

(5) acceptable growing stock with inferior poletimber 

(AccInfP). Tree classes (see footnote1) were used to establish the cutting priority within treatments, such that each 

treatment was defined by the tree classes to be retained 

(table 1). Treatments 2 and 3 were classed as desirable and 

Table 1 -List of five thinning treatments, including tree classes to 

be retained following application of thinning treatments 

Treatments 

Tree class Control DesSupP DesInfP ' AccSupP AccInfP - -- 

Preferred X X X X X 

Desirable X X X X X 

Acceptable X X X 

Cut X 

Cull X 

Superior 

poletimber X X X 

Inferior 

poletimber X X X 

DesSi~pP = desirable growing stock with superior poletimber stock; DesIntP = desirable 

growing stock with inferior polelimber stock; AccSupP = acceptable growing stock with 

superior polelimber stock; AccInlP = acceplable growing stock with inferior poletimber; 

X = tree classes to be retained following application of thinning wealmenl. 
4 and 5 as acceptable. Under traditional marking rules, inferior poletimber. Therefore, thinning was heaviest in the 

superior poletimber trees would be residual growing stock DesSupP treatment and lightest in the AccInfP treatment. 

and inferior poletimber trees would be part of the over- All four levels of thinning significantly reduced residual 

burden component to be removed during thinning. We stand density relative to the unthinned control. 

retained inferior poletimber trees in two of the four thinning 

treatments to compare responses between superior and infe- Residual Poletimber Characteristics 

rior poletimber trees, particularly within treatments characterized by similar overstory removal. Prior to thinning, the stand contained many weak, poorly 

formed, or otherwise defective poletimber trees we classiPrior to treatment, species, d.b.h., tree class, and crown 

class were recorded for every tree L 5.5 inches d.b.h. on 

0.6-acre interior measurement plots of three by two chains. 

Sawtimber tree classes were assigned to trees 2 12.5 inches 

d.b.h., and poletimber tree classes to trees between 5.5 and 

12.4 inches d.b.h. Immediately following thinning, d.b.h. 

and number of epicormic branches on the 16-foot butt log 

were recorded for residual poletimber trees. Individual 

epiconnic branches were tallied according to their location by height and cardinal direction on the butt log section 

so that new epicormic branches could be detected in the 

following year. Diameter growth and epicomic branching 

were assessed 1 year after treatment. 

Results 

Residual Stand Conditions 

Thinning intensities were defined by initial stand quality, 

expressed as tree class, and were not bound to predetermined levels of residual stand density. Postharvest residual 

stand conditions are summarized in table 2. By design, 

desirable treatments were more heavily thinned than 

acceptable treatments. Within both levels of sawtimber 

retention (i.e., desirable and acceptable), reduction in stand 

density was greater in those treatments retaining superior 

poletimber thap in corresponding treatments retaining 

fied as inferior poletimber. A smaller number of poletimber 

trees met our criteria for the superior class. Therefore, 

following thinning, inferior poletimber trees were on average three to four times as numerous as superior poletimber 

trees in corresponding thinning treatments (table 3). 

Within the thinned treatments, superior poletimber trees 

were nearly equally distributed between the red oaks and 

sweetgum, whereas sweetgum accounted for > 65 percent 

of residual inferior poletimber trees. Residual superior 

poletimber trees in this stand were approaching minimum 

sawtimber size (12.5 inches d.b.h.) and were no more than 

2.5 inches below sawtimber d.b.h. at the postharvest evaluation (table 3). In contrast, inferior poletimber trees were 

nearly 2.0 inches smaller in diameter than their superior 

poletimber counterparts, and averaged > 4.0.inches below 

minimum sawtimber d.b.h. Superior poletimber trees also 

averaged fewer than fow epicormic branches on the butt 

log, a level acceptable for grade sawtimber production 

(table 3). In contrast, inferior poletimber trees in corresponding thinning treatments averaged two to three times 

more epicormic branches than their superior poletimber 

counterparts, but these differences were not significant. 

Diameter Growth 

Diameter growth response of surviving superior poletimber 

trees in the DesSupP treatment was significant after the 

first year (table 4). Diameter of superior poletimber trees 

Table 2-Residual stand conditions immediately following 

application of treatments 

Quadratic mean 

Treatment Trees per acre Basal area diameter Stocking 

number feet2/acre inches percent 

Control 113 a" 117 a 13.8 b 98 a 

DesSupP 34 d 42 d 15.0 b 35 d 

DesInfP 64 c 59 c 13.1 b 50c 

AccSupP 38 d 65 c 17.7 a 52 c 

AccInfP 87b 80b 13.1 b 67 b 

DesSupP = desirable growing stock with superior poletimber stock; DeslnfP = desirable 

growing stock with inferior poletimber stock; AccSupP = acceptable growing stock with 

superior poletimber stock; AccInfP = acceptable growing stock with inferior polelimber. 

"Means followed by the same lettea within a column are not significantly dflerent at the 

0.05 level of probability using Duncan's New Multiple Range Test. 
Table 3-Postharvest trees per acre, average diameter, 

and number of epicormic branches on the butt log of 

residual poletimber trees by treatment 

Treatment Tree per acre Diameter Epiconnics 

number inches number 

Control 68.9 8.4 bn 8.6 a 

DesSupP 10.6 9.9 a 3.0 a 

DesInfP 35.6 8.1 b 7.3 a 

AccSupP 10.6 10.3 a 3.6 a 

AccInfP 45.9 8.4 b 10.6 a 

DesSupP = desirable growing stock with superior poletimber stock; 

DesInfP = desirable growing stock with inferior poletimber stock; 

AccSupP = acceptable growing stock with superior poletimber stock; 

AccInfP = acceptable growing stock with inferior poletimber. 

"Means followed by the same letter within a column are not 

significantly different at the 0.05 level d probability using Duncan's 

New Multiple Range Test. 

in the DesSupP treatment grew four times as much as 

that of poletimber trees in the unthi~ed control, and 

twice as much as that of inferior poletimber trees in either 

inferior poletimber treatment (DesInfP and AccInfP). 

First-year diameter growth of inferior poletimber trees in 

both overstory treatments was uniformly low and did not 

differ significantly from growth of poletimber trees in the 

unthinned control. 

Within each of the five treatments, individual species 

groups responded similarly in initial diameter growth 

(fig. 1). As a group, red oak poletimber trees averaged 

0.09 inches in first-year diameter growth in the unhmed 

control, compared to an average of 0.18 inches in diameter 

growth in the DesSupP treatment. Similarly, sweetgurn 

poletimber trees averaged 0.06 inches in diameter growth 

during the first year in the unthimed control, compared to 

an average of 0.17 inches in diameter growth in the DesSupP 

treatment. Despite this wide variation in response, first-year 

diameter growth response within individual species groups 

was not significant across the five levels of thinning. 

Epicormic Branching 

In general, production of new epiconnic branches by poletimber trees increased as stand density decreased (table 4). 

Poletimber trees in desirable treatments produced significantly more new epiconnic branches than poletimber trees in 

the unthimed control. Both superior and inferior poletimber 

trees produced nearly twice as many new epicormic branches 

in desirable treatments as they did in corresponding acceptable treatments during the first year. Average production of 

new epiconnic branches by poletimber trees in acceptable 

treatments did not exceed 2.2 branches and did not differ 

significantly from that for the unthimed control. 

Production of new epiconnic branches during the first year 

varied by individual species group (fig. 2). Production of 

new epiconnic branches by red oak poletimber trees varied 

by treatment, but differences were not significant. Thinning 

had no effect on the production of new epiconnic branches 

by residual sweetgum poletimber trees, which averaged 

fewer than three new epicormic branches during the first 

year after thinning across treatments. 

The total number of epiconnic branches doubled on 

superior poletimber trees in the desirable treatment, but 

increased by only one branch on those in the acceptable 

Table 4-Average tree diameter and diameter growth of residual 

poletimber trees 1 year after thinning, by treatment, and total 

number of epicormic branches and number of new epicormic 

branches for those trees, by treatment, 1 year after thinning 

Diameter Diameter Total epiconnics New 

Treatment year 1 growth Year 1 epicormics 

----- inches - - - - - - - - - - - - - number - - - - - - - - 

Control 8.6 ba 0.05 b 7.9 a 1.2 c 

DesSupP 10.3 a 0.20 a 6.7 a 4.3 a 

DesInfP 8.3 b 0.09 b 8.2 a 3.1 ab 

AccSupP 10.6 a 0.13 ab 4.4 a 2.2 bc 

AccInfP 8.4b 0.10b 10.8 a 1.5 c 

DesSupP = desirable growing stock with superior poletimber stock; DesInlP = desirable 

growing stock with inferior poletimber stock; AccSupP = acceptable growing stock with 

superior poletimber stock; AcclnIP = acceptable growing stock with inferior poletimber. 

"Means followed by the same letter wihin a cdumn are not significantly different at he 

0.05 level of probability using Duncan's New Multiple Range Test. 
0.2 

Control Dessu~P H DeslnfP ACCSUDP . AcclnfP 1 

Red oak Sweetgum 

Species group 

Figure 1 -Avaage diameter growth d residual poletimber trees by species group 1 year fouowing 

five levels of thinning. hfeans with the same letter within a species group are not significaurly 

Merent at the 0.05 level of probability using Duncan's New Multiple Range Test. DesSupP= 

desirable growing stock with superior poleti~bfr stock: DesInfP= desirable growing stock with 

inferior poletimber stock: AccSqiP= acceptable growing stock with superior poletimber stock; 

AccInfP = accq~tahle "gowing stock with inferior poletimber. 

Red oak Sweetgurn 

Species group 

Figure 2-Average number of new epiconnic branches prodwed on the butt log of residual 

poletimber trees by species group 1 year following Gve levels of thinning . Means with he same 

leller within a species group are not signiGcanUy different at the 0.05 level of probability using 

Duncan's New Multiple Range Test. DesSupP= desirable growing stock wih superior poletimber 

stock: DesInfP = desirable erowine stock with inferior olet timber stock; AccSupP = acceptable ... - 

growing stock with superior polelimber stock; AccInfP = acceptable growing stock with inferior 

poletimber. 

treatment during the first year (tables 3 and 4). The total Although epicormic branch totals on superior poletimber 

number of branches on inferior poletimber trees only trees were half that of inferior poletimber trees in some 

slightly increased during the first year, but were still cases, there still were no significant differences across treattoo numerous for production of high-quality sawtimber. ments in total epiconnic branches after the first year. 
Conclusions 

Retention of poletimber trees in the expectation that they will 

produce sawtimber is an attractive but uncertain option when 

planning thinning operaljons in even-aged sawtimber stands. 

Retaining poletimber for sawtimber production requires 

that improved growth and maintenance of bole quality 

be achieved following thinning. A new tree classification 

system (see footnote 1) was used in this study to segregate poletimber trees with high potential to produce grade 

sawtimber from those of low potential. Our first-year results 

indicate that future production of grade sawtimber from 

trees ipitially classed as superior poletimber may be a realistic possibility, but that such production is highly unlikely 

for trees classed as inferior poletimber. First-year diameter 

growth of superior poletimber trees was up to twice as great 

as that of.inferior poletimber trees. Superior poletimber 

trees also maintained fewer total epicormic branches than 

inferior poletimber trees after the first year. The desirable 

treatment enhanced the diameter growth of the superior 

poletimber trees but promoted greater epicomic branching, 

particularly among red oaks, and reduced stand stocking 

below optimum levels to fully occupy the site. The acceptable treatment minimized epicormic branching on superior 

poletimber trees during the first year across all species but 

did not improve growth beyond that of inferior poletimbkr 

trees or that of unreleased poletimber trees in the control. 

The first-year response of the superior poletimber trees 

in both treatments reflects the inherent tradeoff between 

improved growth and loss of bole quality associated with 

most partial cutting in hardwood stands. Further assessment 

of superior poletimber trees will be required to determine if 

the initial increase in epicormic branching in the desirable 

treatment continues and if growth rates within the acceptable treatment can improve over time. 

Acknowledgments 

The authors thank Barksdale Air Force Base and Matthew 

Stroupe, staff forester, who helped locate a study site. We 

also thank the technicians at the Southern Hardwoods 

Laboratory for their help in the field. 

Literature Cited 

Baker, J.B.; Broadfoot, W.hl. 1979. A practical field method of site 

evaluation for commercially important southern hardwoods. Gen. Tech. 

Rep. SO-26. New Orleans: U.S. Department of Agriculture, Forest 

Service, Southern Forest Experiment Station. 51 p. 

Goelz, J.C.G. 1995. A stocking guide for southern bottomland hardwoods. 

Southern Journal of Applied Forestry. 19: 1M-104. 

Putnam, J.A.; Fumival, G.M.; McKnight, J.S. 1%0. Management and 

inventory of southern hardrvoods. Agric. Handb. 181. Washington, DC: 

U.S. Department of Agriculture, Forest Service. 102 p. 

United States Department of Agriculture, Natural Resources Conservation 

Service, Soil Survey Division. Official soil series descriptions. http:;~ 

ortho.ftw.nrcs.us&.gov~os& Date accessed: October 20(n]. 

United States Department of Agriculture, Soil Conservation Service. 

1962. Soil survey of Bossier Parish, Louisiana. Washington, DC: U.S. 

Government Printing Office. 144 p. 

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