Abstract
We studied branching in Sequoia sempervirens (Lamb. ex D. Don) Endl. (coast redwood) and Pseudotsuga menziesii (Mirb.) Franco var. menziesii (coast Douglas-fir) because of their commercial value to coastal northern California. We focused on branching in the second log, which constitutes an important part of a tree’s wood volume and potential value. We quantified branch size and branch growth of overstory trees in multiaged stands in Mendocino County, California, in response to topographic, silvicultural, and stand- and tree-related variables. Higher stand density—a measure of competition averaged across the sample plot—did not correlate with size of the largest second-log branch measured but was associated with a smaller average diameter of the largest branches measured on all sides of the study tree. The largest branch measured was smaller when in closer proximity to branches of its immediate neighbor tree. Redwood had larger branches than Douglas-fir but their size was more sensitive to an ecological gradient of soil-moisture deficit. Branches responded differently to individual tree selection harvest of conifers versus herbicide control of hardwoods. Residual conifer branches in harvested plots responded almost immediately with increased growth, but this release was short-lived. Branches in herbicide-treated plots exhibited a delayed release, giving more consistent branch growth throughout two five-year measurement periods after treatment.
Highlights
Controlling tree branching is a challenge for forest managers concerned about knots in timber products [1,2,3] or fuel ladders in fire-prone regions [4,5]
We studied branch size and branch growth in mixed multiaged redwood and Douglas-fir stands
We modeled branch size in terms of BIX and maximum branch diameter (MaxB)
Summary
Controlling tree branching is a challenge for forest managers concerned about knots in timber products [1,2,3] or fuel ladders in fire-prone regions [4,5]. Trees with large lower branches are more likely to allow fire to climb into the tree crown, which can result in active crown fires within forests in fire-prone regions [6]. Trees with large branches yield sawn timber with large knots, which can impact performance and lower the value of their lumber [7,8,9]. Crown structure variables were under genetic control in loblolly pine (Pinus taeda L.) and slash pine (P. elliottii Engelm.) plantations, affording selection for desired traits including branch diameter [11].
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