Assessment of precommercial thinning as a restoration tool for coast redwood-Douglas-fir forests

In the redwood region, recent expansion of parks and reserves into former commercial timberland has changed management objectives, however, some timber management techniques may be valuable restoration treatments. The effectiveness of precommercial thinning as a restorative treatment in young (27-46 year old) even-aged second growth coast redwood (Sequoia sempervirens) – Douglas-fir (Pseudotsuga menziezii) forests was assessed in five stands in Redwood National Park, California. Thinned and unthinned areas within the same even-aged stand were compared 13 to 18 years post thinning. Precommercial thinning met forest restoration goals by postponing decline in tree vigor, thereby improving response to future thinnings, and enhancing the stands ability to meet diverse or changing management goals. Trees within precommercially thinned areas were found to be more vigorous than adjacent unthinned areas, averaging 21% larger live crown ratios. Coast redwood's 10 year diameter growth increment improved 50%, and Douglas-fir improved 31% in precommercial thinned areas. Tree stability (as assessed via height : diameter ratios) was improved by 18% in precommercially thinned areas. Precommercial thinning is recommended as a restoration treatment at this stage of stand development, because it efficiently accomplishes the goals of forest restoration and maintains sufficient tree stocking to buffer against future small-scale disturbances.