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

Abstract

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

The effect of the interaction of various spawn grains with different culture medium on carpophore dry weights and stipe and pileus diameters of Lentinus squarrosulus (Mont.) Singer

“…When significant differences were determined for the main effects or their interactions (p 0.05), comparisons among means were made using Duncan's multiple range test (Snedecor and Cochran, 1987;Sullivan and Sullivan, 2001). Values of 0.01, 0.1 and 1.0 were added to dry weights, stipe and pileus diameters, Means followed by the same letter(s) within the same row or column in a treatment group are not significantly different statistically at 5% level of probability using DMRT.…”

Individual legacy trees influence vertebrate wildlife diversity in commercial forests

“…Songbirds in a variety of coniferous mixed, and hardwood forest types have benefited from the retention of residual trees (Hobson and Schieck, 1999;Rodewald and Yahner, 2000;Schieck et al, 2000;Tittler et al, 2001;Whittman et al, 2002;Zimmerman, 2002). Southern red-backed voles (Clethrionomys gapperi), a late-successional associated forest species, are also more common in harvested areas as the basal area in residual trees increases (Sullivan and Sullivan, 2001). The retention of residual structure during logging appears to have benefits to wildlife, but additional research will be necessary to distinguish the effects of retaining commercially mature-but relatively young-trees for wildlife from retaining and managing legacy trees, which are typically much older.…”

Comunidade de Carabidae (Coleoptera) em manchas florestais no Pantanal, Mato Grosso do Sul, Brasil

“…Mas, dependendo do grupo taxonômico, da escala espacial e do parâmetro estrutural, a diversidade pode até diminuir com o incremento em heterogeneidade (DAVIDOWITZ & ROSENZWEIG, 1998;SULLIVAN & SULLIVAN, 2001;TEWS et al, 2004). A comunidade de plantas determina a estrutura física do ambiente para as espécies animais em muitos hábitats (MACARTHUR & MACARTHUR, 1961;LAWTON, 1983;MCCOY & BELL, 1991;TEWS et al, 2004).…”