No. 80 

1958 

RESULTS 18 YEARS AFTER PLANTING LOBLOUY PINES 

AT RIFFERENT SPACINGS 

In 1939 a test of four spacings in planting loblolly 

pine seedlings was begun in an abandoned field on Maryland's 

Eastern Shore. The spacings were 4, 5.7, 8, and 11.3 feet 

between trees; each spacing was replicated on four 100-footsquare plots. In the 4- and 8-foot spacings, rows and trees 

within rows were 4 or 8 feet apart, with trees opposite in 

adjoining rows. In the other two spacings, trees in adjoining rows were staggered. .Trees 8 feet apart staggered in 

rows 4 feet apart gave the 5.7-foot spacing; trees 16 feet 

apart in rows 8 feet apart gave the 11.3-foot spacing. 

1957 Measurements 

Eighteen years later, before the 1957 growth started, 

trees were measured in each plot inside an isolation strip 

that extended to midway between the first and second rows 

from a plot edge. All planted trees, and all volunteers by 

species, were tallied separately by l-inch diameter (breast 

high) classes. On twenty representative planted trees in 

each plot, total height was also measured. 

Effect On Planted Trees 

In 1957, the number of living planted trees per acre, 

their average diameter and basal area and volume, varied 

with the original spacing. There were 1,067 more planted 

trees per acre at the closest spacing than at the widest 

(table 1). Although 40 to 54 percent of the planted trees 

in all spacings had died since 1939, only at the closest 

spacing had competition apparently caused some mortality. 

The 1957 measurements showed that, the closer the 

original planting, the greater the basal areas and total 

cordwood volumes (table 1). At the 4-foot spacing, basal 

area of planted trees per acre was 130 percent more than at 

the 11.3-foot spacing, and the volume in trees 4 inches 

d.b.h. and larger was 75 percent more. However, when only 

pines 6 inches deboh. and larger are considered, the 8-foot 

spacing showed the greatest cordwood volume (table 1). 

.A 

FOREST RESEARCH NOTES 

NORTHEASTERN FOREST EXPERIMENT STATION 

Upper Darby , Pennsylvania 

0 

.' 
Most of the per-acre volume differences are due to 

the effect of spacing on number of trees and diameter growth, 

not on tree height. The average diameter of planted pines 

increased from 4.5 inches at the 4-foot original spacing to 

7.7 inches at 11,3 feet (table 1). But average and maximum 

heights tended to increase only slightly with greater distance between trees; within a diameter class, heights tended 

to decrease with wider spacing (table 2). 

Table 1.--Number of planted pines living in 1957, their average diameter, 

basal area, and volume per acre, by spacings 

Volume per acre in trees1-- 1 Original spacing I Trees 1 1 Basal area 

of planted trees per acre diameter per acre 4 inches d.b.h. 6 inches d.b.h. 

- - -- - 

Feet Number Inches Sq. ft. Cords Cords 

4 1,258 4.5 141.5 17.8 7.7 

5.7 738 5.4 116.8 16.5 12.0 

411 6.6 98.3 15.7 14.4 ~ 1!.3 191 7.7 61.5 10.2 9.9 

'~olume in cords of roughwood above a l-foot stump to a top diameter (i.b.) of 3 inches. Table values were computed using field measurements and Table 3 of U.S. Dept. Agr. 

Misc. hb. 50, "Volume, yield. and stand tables for second-growth southern pines." 

'~ncludes trees 0.6 inch d.b.h. and larger. 

'1ncludes both planted and volunteer pines. 

Table 2.--Average herghts of sample trees zn relatron to spacrng 

and present draneter 

A1 1 

sizes 

Original spacing 

Ofplantedtrees 

Diameter (b.h. ) , in inches 

4t05 16~07 /st09 110t011 1 12 

Feet Feet Feet Feet Feet Feet Feet 

4 32.8 36.3 40.0 -- -- 34.7 

5.7 32.4 36.2 39.8 42.0 -- 35.2 

8 31.7 36.0 39.7 42.7 -- 36.6 

11.3 31.1 33.9 37.8 40.5 46.0 36.0 

All spacings 32.4 35.6 38.9 41.0 46.0 35.6 

Table 3.--Number of volunteer trees per acre, total basal area of all trees, 

and total volume of ptne, by orzgrnal spaczng of planted trees 

Original spacing 

of planted trees 

Feet Number Number Sq. ft. Cords Cords 

4 71 2 41 150.3 18.2 7.8 

5.7 179 488 132.2 17.2 12.3 

8 285 7 07 123.0 17.3 15.2 

11.3 829 917 108.0 14.7 12.6 

Volume per acre in pines2-- 

4 inches d.b.h. 

and larger 

Basal area per 

acre of all 

trees1 

6 inches d.b.1~. 

and larger 

Volunteers per acre1 . 

Pines Pines and 

hardwoods 
Volunteer Trees 

Many volunteer trees have become established on the 

plots, roughly in inverse proportion to the density of the 

planting (table 3), thus tending to equalize the total densities of stocking. For instance, the difference in number 

of planted trees between the closest and widest spacings was 

1,067 per acre, but this difference drops to 391 trees per 

acre (stems 0.6 inch d.b.h. and larger) when volunteers also 

are counted. The narrowing of differences in stocking density is reflected in basal areas and volumes. Maximum difference in basal area per acre was 80 square feet for 

planted trees, 42 square feet when volunteers were included; 

in volume of pine stems 4 inches d.b.h. and larger, maximum 

difference was 7.6 cords for planted trees, 3.5 cords with 

pine volunteers included (tables 1 and 3). Although we have 

no measure of it, growth response to the different spacings 

doubtless was reduced in some degree by competition from the 

volunteers. 

Conclusions 

In view of the above results, present spacing practices in plantings on the Eastern Shore seem satisfactory. 

The most common one, 6 feet by 7 feet, is probably best, 

particularly where commercial row thinnings for pulpwood are 

feasible in stands 15 to 20 years old. An 8-foot spacing 

will provide larger trees, but it results in larger limbs 

and slower natural pruning. However, where some volunteer 

pines can be expected, an 8-foot spacing can be recommended. 

Wider spacings produce too limby trees, and a 4-foot spacing 

too spindly trees, to be advisable. 

The results and conclusions from this study agree 

fairly closely with those from more extensive trials in the 

South (1, 2). 

Literature Cited 

1. Wakeley, P. C. 

1954. Planting the southern pines. U. S. Dept. Agr., 

Agr. Monograph 18. 233 pp. 

2. Ware, L. M., and Stahelin, R. 

1948. Gropth of southern pine plantations at various 

spacings, Jour. Forestry 46: 267-274. 

--S. LITTLE and H. A. SOMES 

Northeastern Forest Experiment Station 

Forest Service, U. S. Dept. Agriculture