Comparing tree and stand volume growth response to low and crown thinning in young natural Douglas-fir Stands

Abstract

We consider tree and stand response to low, crown, and no thinning of well-differentiated, naturally regenerated even-aged Douglas-fir stands over 15 years on a moderately productive Cascade Mountains site and over 10 years on a highly productive Oregon Coast Range site. Regardless of treatment, trees in dominant and codominant crown classes continued growing at preinitiation rates and contributed 92-100% of stand growth 5-15 years later. Most leave trees in suppressed crown classes died during the first 10 years and suppressed and intermediate crown classes contributed little to stand growth because survivors continued to grow slowly. Low thinning remains the most reliable thinning method for increasing stand volume in high-quality trees. Crown or selection thinning may be used to achieve certain objectives if managers carefully use information about response of trees in various crown classes. Growth rates of residual stands will depend on the amount of residual growing stock and the degree to which it is comprised of vigorously growing dominant and codominant trees. Residual subordinate trees may provide snags but few living trees in small-diameter classes. Implications for management of the Douglas-fir are discussed. Copyright © 2007 by the Society of American Foresters.