Reukema, Donald L; Smith, J. Harry G. Development over 25 years of Douglas-fir, western hemlock, and western redcedar planted at various spacings on a very good site in British Columbia. Res. Pap. PNW-RP-381. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station; 1987. 46 p. Results of five spacing trials on the University of British Columbia Research Forest, covering a range of plantation spacings from 1 to 5 meters, showed that choice of initial spacing is among the most important factors influencing bole and crown development and stand growth and yield. The trials include Douglas-fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla), and western redcedar (Thuja plicata). The results to date should help managers to choose optimum spacings for their purposes. Initial wide spacings with rectangularities up to 2:1, such as 6 by 3 meters, resulted in efficient production of large trees of high value and satisfactory quality. Pruning of widely spaced trees to enhance quality of the lower bole is strongly recommended.
This file was created by scanning the printed publication. Mis-scans identified by the software have been corrected; however, some errors may remain. Yield tables generated by the stand simulation program DFSIM (Douglas-Fir SIMulator) are presented for. a number of possible management regimes. These include a "normal" yield table; tables for stands planted or precommercially thinned to 300 and 400 trees per acre; tables for commercially thinned stands with and without prior commercial thinning; and tables illustrating the effect of fertilization with nitrogen. Guides are presented for number of trees to be planted or left after precommercial thinning and expected time of first commercial thinning.
AuthorsThese tables can be used as aids in choice of management regimes, guides to stocking control, and as a partial basis for estimating probable yields of future managed stands. Their limitations arise mainly from limitations of the basic data used in construction of DFSIM. Users are cautioned on some misinterpretations.
A 29-year record of seedfall in thinned and unthinned portions of a Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand, spanning ages 39 through 68, reveals annual seed production from no seeds to about 3 million per hectare. For the nine largest crops, annual seedfall in the best seed-producing thinning treatment included at least 100 000 filled seed per hectare. The first of these nine crops was in 1950; the other eight occurred at 1- to 4-year intervals beginning with 1959. For the nine largest crops, the proportion of seeds filled averaged 45% and ranged from 30 to 54%. Typically, about two-thirds of the seed fell by mid-December; but for two of the three largest crops, time of seed shedding was greatly delayed. Thinning substantially increased the number of seeds produced in some years following thinning but the effect was not lasting. There was little or no effect of thinning on the proportion of seed filled or timing of seed dissemination.
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