True fir spacing and yield trials

Description

This report updates data and comparisons from previous reports (Curtis and others 2000, Curtis 2008) on a series of precommercial thinning and yield trials in high-elevation true fir-hemlock stands, using data from the 12 replicates for which 20-year data are now available. The stands were varying mixtures of Pacific silver fir (Abies amabilis (Douglas ex Loudon) Douglas ex Forbes), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and noble fir (Abies procera Rehder). Trends noted in the 2008 report continue. Increment in top height was somewhat reduced at wide spacings. Volume increment and basal area increment increased as the residual number of trees increased. There was a small increase in diameter increment of the 80 largest trees per acre at wide spacing. Relative stand densities on the unthinned plots, as measured by stand density index (SDI) and relative density (RD), are still increasing; it appears that the maximum (not yet attained) is probably at least 20 to 25 percent greater than values observed in Douglas-fir.

Subjects

Series Statement

• Research Paper -- PNW-RP-590

Links

• External source

Other Editions

• True fir spacing and yield trials: 20-year updateUnited States Department of Agriculture, Forest Service, Pacific Northwest Research Station2013-01-01
• True fir spacing and yield trialsU.S. Dept. of Agriculture, Forest Service, Pacific Northwest Research Station2013