Crown Expansion and Stem Radial Growth of Douglas-Fir as Influenced by Release

Abstract A study of 32 felled and dissected codominant trees (29 released and 3 unreleased) in a 50-year-old Pseudotsuga menziesii stand in western Washington indicated that release tends to reduce rather than accelerate crown expansion during the first few growing seasons following thinning. This effect was most pronounced in the upper part of the crown. Moreover, when released and unreleased sides of a given tree were compared, no differences in branch elongation were apparent. Stem radial growth was increased by release, progressively improving lower on the stem. Thus, apparently crown buildup was not a major contributing factor in the stem-growth response of released trees.