Prediction of pruning wound occlusion and defect core size in ponderosa pine

Abstract

Occlusion following pruning is an important determinant of the size of the inner defect core of a pruned log. A total of 117 branch stubs from 5 ponderosa pine (Pinus ponderosa) logs pruned 32 yr previously were destructively sampled to evaluate occlusion in relation to growth and wound characteristics. Models were developed to predict the size of the occlusion zone and the years to occlusion. The models indicate the size of the occlusion zone is more sensitive to length of the branch stub than stub diameter. Increasing the length of the pruning stub from 1.5 to 3.0 in. increases the predicted size of the occlusion zone from 112-132% depending on stub diameter. Doubling the stub diameter an equal amount increases the size of the occlusion zone by only 3-14%. Minimization of the size of defect core is best achieved by reducing the length of the pruning stub through cutting flush with the bark. These results suggest land managers should not hesitate to prune fast growing ponderosa pine plantations with large branch diameters.