Skip to Main Content
True fir spacing and yield trials—20-year updateAuthor(s): Robert O. Curtis
Source: Res. Pap. PNW-RP-590. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 32 p.
Publication Series: Research Paper (RP)
Station: Pacific Northwest Research Station
View PDF (2.47 MB)
DescriptionThis 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.
- You may send email to firstname.lastname@example.org to request a hard copy of this publication.
- (Please specify exactly which publication you are requesting and your mailing address.)
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
CitationCurtis, Robert O. 2013. True fir spacing and yield trials—20-year update. Res. Pap. PNW-RP-590. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 32 p.
KeywordsPrecommercial thinning, increment, yield, Abies amabilis, Tsuga heterophylla, Abies procera, true firs, noble fir, Pacific silver fir.
- Saddle Bag Mountain Research Natural Area: guidebook supplement 34.
- Growth of site trees and stand structure in mixed stands of Pacific silver fir and western hemlock.
- True fir spacing trials: 10-year results.
XML: View XML