Growth and Yield
Some of the earliest data on diameter growth in natural eastern redcedar stands is presented in table 2 (3). Site classes mentioned are those described in table 1. Analysis of these data provided equations to compute the height-age relationships in table 3. The relation of height of dominant and codominant trees to d.b.h. and stand density was also determined, after pooling of data for age and site classes (11). Height growth, a reflection of soil depth and fertility, increases with stocking density (fig 1).
Table 2- Average annual diameter growth of dominant eastern redcedar by site
class and stand density¹ Site Class Stand character
IV mm Under-stocked 7.6 8.1 4.6 3.6 Well-stocked - 8.1 4.3 3.0 Over-stocked - 3.8 2.5 1.8 in Under-stocked 0.30 0.32 0.18 0.14 Well-stocked - 0.32 0.17 0.12 Over-stocked - 0.15 0.10 0.07 ¹Based on increment core measurements of 456 trees (3). Table 3- Total height of eastern recedars by age¹ and site class Site Class Growth rings II III m ft m ft 10 4.6 15 3.7 12 15 5.5 18 5.2 17 20 7.6 25 6.1 20 25 8.5 28 7.3 24 30 9.8 32 7.9 26 35 10.7 35 8.8 29 40 11.3 37 9.4 31 45 12.2 40 10.1 33 50 12.8 42 10.7 35 ¹Age was computed using the total number of growth rings; false rings make accurate determinations difficult.
Figure 1- Relation of height to d.b.h. by stocking class.
Other studies in Arkansas have shown that growth and yield are affected by stand density and hardwood competition. In a 45-year-old eastern redcedar stand, highest volume growth was obtained in unthinned stands from which hardwoods had been removed. Volumes averaged 1.96 m³/ha (28 ft³/acre) per year during a 14-year period. This was double the growth of stands where hardwoods were left. A stand containing 432 crop trees per hectare (175/acre), 7.6 cm (3.0 in) d.b.h. and larger grew nearly the same volume after 14 years when 80 percent of the competition was removed as an unreleased stand of 988 trees per hectare (400/acre) (11).
Over a 10-year period in northern Arkansas, completely released stands averaged higher growth in d.b.h., basal area, and volume than stands where only crown competition was removed. The greatest mean d.b.h. growth, 6.4 cm (2.5 in), occurred with the lightest stocking, 124 crop trees per hectare (50/acre). As stocking increased, mean d.b.h. growth decreased. Basal area increase was greatest in stands having 988 crop trees per hectare (400/acre), and as stocking decreased, basal area and volume growth decreased. An initial stocking of 988 eastern redcedar crop trees per hectare (400/acre), averaging about 7.6 cm (3 in) d.b.h., produced over 28 m³/ha (2,000 fbm/acre) in 10 years. A stocking of 432 trees per hectare (175/acre), averaging 10.2 cm (4 in) d.b.h., produced slightly more volume during the same period on similar sites (11).
On most sites eastern redcedar grows slowly, and long rotations are required to produce conventional sawlogs. Because the wood is used for small items, however, and there is wide latitude in acceptable defects, shortening of rotations and intermediate harvesting of merchantable wood are possible. About 20 to 30 years are required for posts and 40 to 60 years for sawtimber (11,25).
Maintaining relatively dense stands can maximize post production. Thinning one or more times before harvest cut hastens sawlog production but may not increase total yield. The ideal density for growing sawlogs is not known, but excessive thinning may promote excessive formation of sapwood and growth of lower branches.
- Burns, Russell M., and Barbara H. Honkala, technical coordinators. 1990. Silvics of North America: 1. Conifers; 2. Hardwoods. Agriculture Handbook 654 (Supersedes Agriculture Handbook 271,Silvics of Forest Trees of the United States, 1965). U.S. Department of Agriculture, Forest Service, Washington, DC. vol.2, 877 pp. http://www.na.fs.fed.us/spfo/pubs/silvics_manual/table_of_contents.htm
No one has provided updates yet.