Effects of partial cutting and partial disturbance by wind and insects on stand composition, structure and growth in boreal mixedwoods

Abstract

Although partial harvesting has been proposed as a measure for maintaining compositional and structural characteristics of natural old-growth stands, it has not been rigorously evaluated. The first objective of this study was to compare forest composition and structural characteristics after killing a portion of canopy trees and after partial cuts in boreal mixedwoods of eastern Canada by natural disturbances. The second objective was to evaluate the effectiveness of the partial harvest treatments in meeting the silvicultural objectives of increased growth of residual stems and advances in regeneration. Higher densities of shade-intolerant species were found after partial cuts when comparedwith naturally disturbed stands. Similar diameter distributions of residual living trees and densities of shade-tolerant species were found following all disturbances. Increase in growth was similar for all height classes (<1 m, 12 m, 24 mand > 4 m) of balsam fir (Abies balsamea) advance regeneration in naturally disturbed and partially cut stands. In the overstory, trembling aspen (Populus tremuloides), white birch (Betula papyrifera), white spruce (Picea glauca) and balsam fir had growth increases after partial cuts, whereas black spruce (Picea mariana) did not. This study provides evidence that partial cutting in these mixedwood stands may emulate the effects of natural mortality resulting from natural partial disturbances by retaining key compositional and structural attributes and inducing increased growth rates in residual trees. © 2012 Institute of Chartered Foresters. All rights reserved.