Effects of Crown Release on Growth and Quality of Even-Aged Red
The effects of six crown-release treatments on growth and bole quality of 54 dominant, codominant, and intermediate red maples (Acer rubrum L.) were examined in an even-aged stand in upper Michigan. Treatments included an unreleased control, a single-tree and a two-tree crown release, and a full crown-to-crown release of 5, 10, and 15 ft. Twenty-two years after treatment, all trees showed a decrease in number of defects. Trees released to 15 ft lost twice as many defects as unreleased trees. Codominants and intermediates lost twice as many defects as dominants. Overgrown knots were the most common defects and showed the greatest decrease over time. The number of epicormic branches also declined; dominants had no epicormic branches after 22 years. Growth was greater for all released trees than for unreleased trees. Twice as much growth occurred in the 15-ft treatment as in the control, but this result was not significantly greater than those of the 5- or 10-ft crown release treatments. Dominant trees grew significantly more than the intermediate trees. Twenty-two years after treatment, dominants appeared to be least affected by crown-release but had the fewest defects and largest diameters. Crown-release treatment had the greatest effect on intermediates. To maximize growth and maintain bole quality, a crown release of between 5 and 10 ft is recommended for red maple pole-size trees in the Lake States.
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