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Small mammal associations with habitat structure in riparian zones of a managed ICH Forest; Revelstoke, B.C.

University of British Columbia

I investigated small mammal communities and habitat associations within riparian and upland areas of a class S2 stream in Revelstoke, B.C. Sampling sites were distributed among three types of habitat: old-growth ICH forests, 5-10-year-old clearcut, and clearcuts with 60 to 90m riparian buffers. I assessed small mammal populations and habitat associations along a transriparian gradient starting flush with the stream and going upland perpendicular to the stream (300m). Six small mammal species or genera were captured. Deer mice (Peromyscus maniculatus), western jumping mice (Zapus princeps), voles (Microtus spp.j, shrews (Sorex spp), red-backed voles (Clethrionomys gapperi), and short tailed weasels (Mustela erminea) all occupied clearcut sites. M. erminea was not captured within the riparian buffer strips areas, nor within the old-growth habitat. Small mammal species richness varied with sampling-site but was generally higher within the clearcut and buffered habitats where higher percent cover of shrubs and volume of downed wood were found. The relative abundance of small mammals differed among sampling-sites. Small mammal density and abundance were higher within the heterogeneous buffered habitat (composed of both clearcut and riparian buffer zones) followed by the clearcut and old-growth habitats. Herbs (including ferns), species richness and vegetative percent cover differed among sampling-sites. There was no distance effect on vegetation species richness. Percent cover of shrubs differed significantly with distance from stream; Percent cover of herbs was greater within old-growth and riparian buffer strip areas than in clearcut zones. Sampling-sites contained a wide range of microhabitats, so it was not possible to discern a continuous gradient or trend in habitat structure. There was no distance effect on the pooled small mammal populations. P. maniculalus dominated all habitats. Sorex were most abundant within clearcut areas and were positively correlated with distance from the stream in the buffered habitat. Microtus spp. and Z. princeps were most abundant within old-growth and riparian buffer strips. Z. princeps capture rates were negatively correlated with distance from stream in clearcuts and old-growth habitats. C. gapperi was found only in riparian buffer strip zones when these were present within a clearcut. My results suggest that heterogeneous habitat (clearcut with riparian buffer) increases the overall small mammal abundance and diversity. Presence of riparian buffer strips allow the density of old-growth obligate species to remain high. From my results it was not possible to suggest an ideal riparian buffer width to contain quality habitats for small mammal communities. Buffers of 60-90m wide appeared adequate to retain species diversity. Because small mammal communities seemed related to the microhabitat rather than the habitat at a larger scale, an investigation of the microhabitat associations would provide better understanding of small mammal population parameters.

Thesis/Dissertation

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2009-03-12

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http://hdl.handle.net/2429/5946

Forestry

University of British Columbia

UBCV

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