Bigleaf maple (Acer macrophyllum Pursh) is a native broadleaf commonly found in the coastal forests of the Pacific Northwest. Following harvesting, vigorous sprouting from cut stumps can create large, rapidly growing clumps of maple sprouts, which can severely reduce the survival and growth of neighbouring conifers. During 1996, ten 0.09-ha plots containing up to 490 bigleaf maple clumps per hectare (cph) were established. A series of maple clump thinning treatments ranging from 0 to 400 cph was assigned to the plots to study the effects of varying maple clump density on understorey light and conifer growth. Select maple clumps were removed by manually cutting all clump sprouts. Post-treatment results over 14 years indicated that the maple clump thinning treatments did not result in any long-lasting differences in conifer survival and growth. In contrast, the clump thinning treatments resulted in a significant decline in cut maple and an increase in uncut maple clump sprout density and volume increment with increased uncut maple cph. Conifer volume increment and total stand volume increment showed no response across the maple cph treatments. Stand periodic annual volume increment of the maple-conifer mixedwood plots ranged from 7.6 to 13.1 m3/ha/yr over 14 years post-thinning.
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Updated January 17, 2013