Long-Term Response of Planted Ponderosa Pine to Thinning in Oregon's Blue Mountains
A spacing study in ponderosa pine (Pinus ponderosa) was established in 1959 by thinning plots in a 33-yr-old plantation near John Day, Oregon. The influence of 4 spacings (17.2, 12.5, 10.1, and 8.7 ft) on stand and tree growth for a 31-yr period was examined. Study plots were remeasured five times after establishment. Periodic annual increments (PAI) of gross basal area, gross volume, and average height differed with period but not with spacing (P ≤ 0.10). The PAIs of mean diameter differed with period and decreased with increasing density. Annual height growth and annual gross and net growth of basal area and volume did not differ with spacing. Annual diameter growth was much greater for trees at the widest spacing. Annual volume growth of the largest 90 trees/ac was greatest at the widest spacing. Thirty-one years after thinning, the largest 90 trees/ac on the widest spacing had 73% of the volume of all the trees on the narrowest spacing. Mortality due to mountain pine beetle (Dendroctonus ponderosae) increased markedly when values for stand density index exceeded 200. Wide spacings increased average tree volumes, increased mean diameters, and reduced the probability of mortality without sacrificing gross cubic volume growth potential. West. J. Appl. For. 8(4):126-132.
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Document Type: Journal Article
Affiliations: USDA Forest Service, Silviculture Laboratory, 1027 N.W. Trenton Avenue, Bend, OR 97701
Publication date: 1993-10-01
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