Five-year growth responses of Douglas-fir, western hemlock, and western redcedar seedlings to manipulated levels of overstory and understory competition.

Abstract

Douglas-fir, western hemlock, and western redcedar seedlings were planted in 2001 within clearcuts, shelterwoods, or thinned stands of second-growth Douglas-fir. Understory vegetation was left untreated or removed to provide areas of vegetation control (AVC) of 0, 50, or 100 percent of seedling growing space. Third-year stem volume of seedlings growing in clearcuts was greater than in thinned stands but did not exceed that in shelterwoods (for redcedar) unless AVC was 50 percent or greater (for Douglas-fir) or 100 percent (for hemlock). Results indicate that competition in thinned stands severely limits seedling growth, competition in shelterwoods limits or prevents growth increases after vegetation control, and understory vegetation in clearcuts is just as competitive as shelterwood trees and understory vegetation combined.

Citation

Harrington, T.B. 2006. Five-year growth responses of Douglas-fir, western hemlock, and western redcedar seedlings to manipulated levels of overstory and understory competition. Canadian Journal of Forest Research. 36(10): 2439-2453