Second-Log Branch Size Comparison Between Even-aged and Multiaged Douglas-fir Stands in Coastal Northern California

Christopher Isaac Kirk, John-Pascal Berrill


We studied how forest management decisions affect branching of coastal Douglas-fir Pseudotsuga menziesii var. menziesii in coastal northern California because knot sizes can affect performance, grade, and value of structural lumber. We focused on branching in the second log which is located immediately above the butt log and constitutes an important part of a tree's wood volume and potential value. Branch diameters were measured on multiple Douglas-fir trees nested within 40 plots sampling even-aged and multiaged stands. We analyzed two tree-level branch size metrics that can be influential in log grading: (i) the basal diameter of the largest branch on the log, and (ii) the average diameter of the largest branch on each quadrant (termed BIX). Generalized linear mixed-effects regression analysis revealed that branches were smaller in multiaged stands than even-aged stands. Trees with larger branches also had larger DBH and crown width, and lower height:diameter ratio. Branch diameters were more sensitive to competition from their nearest neighboring trees than overall stand density or basal area of larger trees. Since neighboring trees exerted control over branch development, and if large branches are undesirable, managers may consider implementing more dispersed patterns of retention and limiting creation of edges.


BIX; multiaged management; Pseudotsuga menziesii; tree branching; uneven-aged silviculture; wood quality.

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