No. 104 

1960 

EFFECTS OF LOW THINNING 

IN ATLANTIC WHITE-CEDAR STANDS 

Atlantic white-cedar typically grows in dense stands. 

In southern New Jersey, young stands commonly contain several thousand trees per acre, and at ages around 60 years 

there still may be 1,000 or more trees per acre. 

a The great density of white-cedar stands led early 

foresters to strongly recommend thinning. Akerman (1) 

thought that thinnings would reduce the time required to 

grow sawtimber by 20 percent, and would improve the quality 

as well. Other early foresters were equally sure that benefits would accrue from thinning cedar stands (2, - 3, 4, 10). 

However, no thinnings actually were made until the 

1920's. Mostly these were commercial thinnings in the better 

stands of about 45 years of age. They yielded net returns 

of $50 to $100 per acre from the cut products (5, 9). 

Income from thinnings, though desirable, should not 

be the sole determinant of thinning practices. Also of 

great importance are the effects upon (1) timber production 

during the whole rotation, and (2) reproduction of the 

white-cedar after harvest cutting. 

@ Some information about these effects is now available 

from thinning plots established in the 1920's by the New 

Jersey Department of Conservation and Economic Development, 

in well-stocked pure white-cedar stands on 40- to 50-foot 

sites. Thinnings were made from below, at the following intensities: 

Basal area 

Plots Stand age removed 

(number) (years) (percent) 

2 22 21 

2 35 34 

2 50 37 

2 50 35 

4 36-40 49 
Table 1.--30-year changes after thinning two white-cedar stands 

 he largest-diameter trees, about 670 per acre. 

2~n cords, unpeeled volume to a top diameter (i.b.) of 4 inches, based on table 44 of U. S. Dept. Agr. Tech. Bul. 251 (5). This also includes sawtimber trees. In board-feet, International rule, 1/8-inch kerf, trees 8 inches d.b. h. and larger to a 6-inch top, based on table 40 of 

Tech. Bul . 251 (2). 

'~verage values from 3 plots after thinning, from 2 plots before thinning. 

Merchantable 

volume per acre 2 

Crop trees 1 

36-40 

5 0 

. 

Average 

d.b'h' 

White-cedar 

stems 

per acre 

- No. Inches Sq.ft. Cords Bd.ft. Inches Sq.ft. Cords Bd.ft. 

Before thinning 3,558 3.4 223.3 11.5 125 - - - - - - -- Thinned3 After thinning 1,025 4.5 114.0 10.3 120 5.0 92.2 10.3 120 

30 years later 9 09 7.0 239.9 54.9 10,510 7.5 206.3 50.0 10,510 

Change - - +2.5 +125.9 +44.6 +10,390 +2.5 +114.1 +39.7 +10,390 

At beginning 3,335 3.5 226.4 12.3 - - 5.2 98.0 12.3 - - None 30 years later 950 6.6 229.0 51.3 8,130 7.3 192.4 46.6 8,130 

Change -- +3.1 + 2.6 +39.0 +8,130 +2.1 + 94.4 +34.3 +8,130 

Before thinning 2,380 4.4 248.9 24.2 450 - - - - -- - - Thinned After thinning 1,050 5.3 161.8 21.1 450 5.9 125.9 20.1 450 

30 years later 880 7.5 272.8 71.8 16,660 8.1 239.1 66.0 16,660 

Change - - +2.2 +111.0 +50.7 +16,210 +2.2 +113.2 +45.9 +16,210 

At beginning 1,940 4.8 246.9 30.5 1,350 6.4 147.9 25.9 1,350 

None 30 years later 89 0 7,. 7 288.0 77.0 20,240 8.3 253.0 71.0 20,240 

Change -- +2.9 + 41.1 +46.5 +18,890 +1.9 +105.1 +45.1 +18,890 

Age of 

stand 

(years) Volume 

per acre 

Average 

d.b.h. 

area 

peracre Basal area 

per acre 

Treatment I tem 
Each of the four pairs of plots consisted of a thinned plot 

and a control; the $-plot set consisted of 3 thinned plots 

and a control. All plots were small: about 0.04 acre in the 

22-year-old stand, and ranging from 0.125 to 0.3 acre in the 

others. 

Because of wildfires and other mishaps, we have only 

5-year records for the first three pairs of plots listed 

above; for the others we have 30-year records. 

Results 

Mortality, as might be expected, was in most instances much less in thinned than in unthinned plots. In 

the surviving pair of plots, 30-year mortality was 16 and 

54 percent respectively; for thinned plots and control in 

the 4-plot set it was 11 and 72 percent. 

Basal-area growth, with one exception, was substantially greater on thinned plots. However, growth of the 

larger, "crop" trees was not markedly nor consistently increased by thinning. In terms of basal area and cords, on 

both 5-year and 30-year plots, the crop trees generally did 

make slightly better growth where thinning had been done. 

But in terms of board-feet, where we have 30-year records on 

stands that now have reached the age of financial maturity-- 

65 to 80 years (5, 7)--growth in one instance was better and 

in the other was poorer on the thinned plots (table 1). 

Although white-cedar is highly subject to windthrow 

and snow damage, trees on the thinned plots of this study 

suffered no greater damage from wind and snow than did trees 

in unthinned stands. 

The thinnings had one very adverse effect--they encouraged the development of an understory of shrubs and 

hardwood trees. These plants are more tolerant of shade 

than Qhite-cedar (6). - During the 30 years since thinning 

they have formed a very dense understory, with the larger 

@ members 6 to 25 feet tall. The species are chiefly sweet 

pepperbush, high-bush blueberry, dangleberry, red maple, 

blackgum, and sweetbay. To reproduce white-cedar, this 

understory must be eliminated or at least controlled. While 

such control is not so much of a problem now as it was before herbicides were available, still it would require an 

appreciable investment per acre. From that angle alone, low 

thinning as done in this study is not desirable. 

Discussion 

Since the low thinnings described above did not appreciably increase pmduction of merchantable timber, and 

did have the undesirable effect of stimulating the growth of 
hardwood understories, such thinnings are not recommended in 

white-cedar management. 

However, the great density of most white-cedar stands 

still implies that thinning, if properly carried out, should 

increase production. The crucial question is: how and when 

should the thinning be done? Although we have no experimental demonstrations of other types of thinning in whitecedar, observations of many stands, and consideration of the 

silvics of the different species that are involved, lead Us 

to believe that crown thinnings in reproduction stands would 

be effective. Such thinnings would be made when the trees 

were about 10 feet tall, and would be so applied as to favor 

dominance of about 700 stems per acre. An essential requirement would be that enough smaller cedars be left to serve as 

trainers and to prevent establishment of objectionable hardwood understories. Any future thinning studies in whitecedar stands should be designed to test this idea. 

Literature Cited 

1. Akerman, A. 

1923. The white cedar of the Dismal Swamp. 

Va. Geol. Comn. Forestry Pub. 30. 21 pp., illus. 

2. Baker, W. M. 

1925. Forestry for profit. 

N.J. Dept. Conserv. and Devlpmt. Ed.2, 88 pp., illus 

3. Emerson, G. B. 

1846. Report on the trees and shrubs growing naturally in the 

forests of Massachusetts. Mass. Zool. and Bot. Survey. 547 

PP., illus. 

4. Gifford, J. 

1900. Forestal conditions and silvicultural prospects of the 

coastal plain of New Jersey. N. J. State Geologist Ann. 

Rpt. 1899: 233-318, ~llus. 

5. Korstian, C. F., and Brush, W. D. 

1931. Southern white cedar. 

U.S. Dept. Agr. Tech. Bul. 251. 75 pp., illus. 

6. Little, S. 

1950. Ecology and silviculture of whitecedar and associated 

hardwoods in southern New Jersey. Yale Univ. School Forestry Bul. 56. 103 pp., illus. 

7. Moore, E. B. 

1939. Forest management in New Jersey. 

N.J. Dept. Conserv. and Devlpmt. 55 pp., illus. 

8. ---------- and Waldron, A. F. 

1938. Southern white cedar. 

N. J. Dept. Conserv. and Devlpmt., Div. Forests and Parks 

Tech. Note 3. 4 pp. 

9. ---------- and Waldron, A. F. 

1940. Growth studies of southern white cedar in New Jersey. 

Jour. Forestry 38: 568-572. 

10. Pinchot, G. 

1899. A study of forest fires and wood production in southern 

New Jersey. N.J. State Geologist Ann. Rpt. 1898, Appendix. 

102 pp., illus. 

--G. T. BAMFaRD 

Forest Management Section, N. J. 

Dept. of Conservation and Economic Development 

and S. LITTLE 

Northeastern Forest Experiment Station 

Forest Service, U.S. Dept. Agriculture