ZONAL AND BIOTOPIC PECULIARITIES OF BANK VOLE POPULATION ABUNDANCE AND ITS VARIABILITY LEVEL

The aim of the paper is to analyze geographical and temporal peculiarities of bank vole population abundance and its variability. Long-term studies have been carried out at 4 sites located in different parts of the geographical range. Data on the population dynamics are available from several sites in the same area with different vegetation composition. Variability in density depends both on the season and the location of the population within the species range. The amplitude of changes in the bank vole population increases when moving from the south (the zone of broad-leaved forests) to the north (the middle-taiga subzone). The bank vole populations living in primary forests are most stable. In secondary forests the values of the variability coefficient rise. Analogous changes to the seasonal dynamics are revealed in the successional series from the primary forests through all developmental stages of the communities to clearings of different age. The cyclicity index changes alongside with variability coefficients from the south to the north. Although the abundance variability of the southern populations from the secondary forests and that of the northern populations from the primary and the secondary forests seem to be similar, the mechanisms of its support are different.