Microhabitat selection by the bank vole (Clethrionomys glareolus Schreber, 1780) under destabilized and stable habitat conditions

The aim of our work was to study the microhabitat selection by the bank vole (Clethrionomys glareolus) under ecologically contrast (undisturbed, postanemogenic and postpyrogenic) conditions. Between 1987 and 2009 we investigated stable biocenoses of foothill area of the Pechora-Ilych State Nature Biosphere Reserve (the Northern Urals) and forest communities destabilized by natural catastrophes (windfall and fire) in the Visim State Nature Biosphere Reserve (the Middle Urals). On the territory of the Pechora-Ilych Reserve we studied the population of animals and the environment characteristics of their microhabitats in three various fir- woods different in their landscape structure: haircap-moss spruce interfluve forest, tall grass flood-plain fir-wood and green moss filical fir-wood, located on the ridge height. On the territory of the Visim Reserve the studies were conducted before the disturbance by windfall and fire (1987-1994), on early stages (2-3 years after disturbances) of anemogenic (windfall) and pyrogenic successions and during the postcatastrophic restoration. We estimated microhabitat selection by bank voles under ecologically contrast conditions by a response of their local numbers to the microhabitat characteristics by the multiple regression method. Small mammals were collected by the trap-line method; all traps during the whole research period were put in the centre of the same 10 м2 squares. On each sample plot we carried out a quantitative description of the environment characteristics of animal microhabitats by 8 variables estimating protective and forage conditions of the biotopes. Under the destabilized conditions on the territory of the Visim Reserve the interannual variability appeared essentially above byotopical variability, compared with microhabitat characteristics in the stable biocenoses of the Pechora-Ilych Reserve. This is explained by high speed successions in the wood communities after the catastrophic natural phenomena. The influence of natural disturbance factors is reflected on the level of the bank vole relative abundance values and the character of population dynamics of this number. Before disturbances in the Visim Reserve this species had been connected with the greatest microhabitat variables, statistically significantly determining distribution number of small mammals: moss cover, dwarfshrub-herb vegetation, shrub, underwood and stumps. After windfall disturbance in early stages of anemogenic successions the local number of the bank vole was influenced by less microhabitat characteristics (underwood, coarse debris, stumps) in comparison with the later stage of postcatastrophic restoration (dwarfshrubherb vegetation and shrub cover, fallen dead trunks, coarse debris, living trees). On the pyrogenic site in early forest successional stages the number of animals depended on only one microhabitat factor, shrub cover, and during the later period of biocenoses restoration after the fire it was connected with stumps. Under stable conditions on the territory of the Pechora-Ilych Reserve in two fir-woods we found the dependence of local number from microhabitat factors. In the haircap-moss spruce forest the bank vole preferred microsites with coarse debris, in the tall grass fir-wood animals prevailed in microhabitats with dwarfshrub-herb vegetation. In green moss filical fir-wood the local number of the bank was statistically significantly connected with the greatest numbers of characteristics among which are dwarfshrub-herb vegetation, shrub cover, fallen dead trunks, dry trunks and stumps. According to our results, microhabitat selection by the bank vole in ecologically contrast environment is connected with microhabitat structure of the biotopes: in the stable environment of fir-woods on the foothill area of the Pechora-Ilych Reserve it is defined by landscape peculiar properties and in destabilized forest biocenoses of the Visim Reserve it is conditioned by forest communities in different postanemogenic and postpyrogenic successional stages. The article contains 2 figures, 8 tables, 40 ref.

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