Predicting branch diameters on second-growth Douglas-fir from tree-level descriptors

The quality of lumber and veneer recovered from logs of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is directly influenced by the maximum limb size attained on the crop tree. Because limb sizes are influenced by stand-density regimes, a need has arisen for quantitative tools that link a wide array of silvicultural regimes to woodproduct quality by accounting for silvicultural effects on crown development. An equation for estimating maximum branch size at a given level within the live crown was developed from data collected on 96 felled sample trees in the Coast Ranges and Cascade foothills of Oregon and Washington. Height and basal diameter of the largest branch within each live whorl were measured on each felled tree, and a predictive equation was developed by various regression techniques. The final mixed-effects nonlinear model estimates maximum branch size as a function of depth into crown and tree diameter at breast height, height, and live crown length.