PREDICTING PRUNED BRANCH STUB OCCLUSION IN YOUNG, COASTAL DOUGLAS-FIR

Time is required after pruning tree branches until radial stem growth occludes individual branch stubs. Foresters and planners need improved understanding of factors affecting occlusion time and distance so the y can better forecast yield of clear wood and returns on pruning inves tments. This study examined occlusion of 335 pruned branches from 38 c oastal Douglas-fir (Pseudotsuga menziesii (Mirb.) France) trees sample d from 13 stands that were pruned between age 9 and 22. Regression mod els were developed for predicting number of years to occlude, the widt h of the occlusion region, and radius-over-occlusion which is the dist ance from the stem pith to the onset of clear wood production. Study r esults indicate that years to occlude is a function of stem size, stub length, stem growth rate, live or dead branch condition, and whether pruning produced smooth or nonsmooth cuts. Distance to occlude is a fu nction of stem size, stub diameter, stem growth rate, live or dead bra nch condition, and whether pruning produced smooth or nonsmooth cuts. Radius-over-occlusion is a function of stem size, stub length, stub di ameter, stem growth rate, and whether pruning produced smooth or nonsm ooth cuts.