Influence of variable retention harvests on forest ecosystems. II. Diversity and population dynamics of small mammals

摘要: Summary 1 Variable retention harvests in temperate coniferous forests provide various intensities and sizes of disturbance across a gradient, from clear-cutting to single-tree harvesting. These ‘green-tree systems’ leave large live trees after harvest (i.e. residual trees) increase structural diversity the regenerating stand. It is unclear what effect these harvesting patterns will have on wildlife general, small mammals particular. 2 This study was designed test hypotheses that: (i) abundance forest-floor decline with lower levels tree retention; (ii) abundance, reproduction survival Microtus spp. southern red-backed vole Clethrionomys gapperi populations increase, respectively, basal area density harvest; (iii) habitat heterogeneity generated by variable limit population size Microtus, thereby reducing feeding damage seedlings planted harvested areas. 3 Small were intensively live-trapped 1996 1999 replicated clear-cut, single seed-tree, group patch-cut uncut forest sites mixed natural Douglas fir Pseudotsuga menziesii–lodgepole pine Pinus contorta British Columbia, Canada. The seed-tree system leaves few wind-firm seed standing singly, or groups, regenerate an naturally. timber (< 1-ha) units dispersed over given forest. 4 Contrary hypothesis (i), mean total similar among sites, species richness lowest but other four treatments. 5 The overall (ha−1) higher clear-cut (11·3) than (6·0), (3·9), (1·8) (0·1) sites. Overall C. (16·2) (10·0) which both (6·4), (4·2) (2·7) sites. 6 The recruitment new differed significantly declining forest. exhibited opposite trend. number successful pregnancies treatments for highest forest, each treatment sites. 7 Hypothesis supported. inversely, that positively, related harvest. also inversely percentage cover crown volume index trees, positively lodgepole cones (seeds) logging debris. 8 In terms (iii), appeared during 1997–98 1998–99 overwinter periods, been caused mainly rather spp. 9 The systems achieved aims persistence prevention outbreaks. methods are as good mammal any other.