Effects of residual stand density on growth and volume production in even-aged red maple stands

The effects of five residual stand densities (9.2, 13.8, 16.1, 18.4 m2/ha, and an unthinned control (27.2 m2/ha)) on 10-year stand and crop tree growth and bole quality were studied in an even-aged red maple stand in Michigan. A secondary treatment of removing the understory trees (5-10 cm DBH) was applied on half the plots. Diameter growth was significantly greater in all cutting treatments than in the control. Ten-year diameter growth in the heaviest cut treatment was nearly three times that of the control. The interaction between understory removal treatments and density treatments was significant for net basal area growth. Ingrowth in the heavier cut treatments accounted for a significant portion of net basal area growth in the plots without understory removal. Mortality was highest in the control and lowest in the heavier cut treatments. Epicormic branching significantly reduced clear bole length of crop trees in the heavier cut treatments, especially when the understory was removed. For these reasons, a more conservative first entry thinning level of about 17-18 m2/ha without controlling the understory is recommended for even-aged red maple stands.