Communities of terrestrial small mammals in two mountain ecosystems influenced by air pollution

Small mammals were sampled in spring and autumn on 1 ha quadrats situated i n clearings caused by air pollution, and on trap-lines or a 0.6 ha quadrat in other habitats. Five insectivore and nine rodent species were collected, including three insectivores and eight rodents in the clearings. Populatio n densities in clearings were significantly higher in the Jeseniky than in the Orlicke hory mountains, but they were rather low overall (0.1-4.1 ind. per ha). Sorer araneus was numerically dominant in samples from both mounta in ecosystems, and other common species were M. agrestis and A. flavicollis in Jeseniky and C. glareolus and M, agrestis in the Orlicke hory mountains . Fluctuations in the numbers of M. agrestis in clearings in the Jeseniky M ts. approached cyclic development. Higher damage to seedlings used in refor estation was found a year after the peak in vole numbers, however, when com pared to other mountains affected by polluting emissions, the damage was mi nor (0.75-1.65%). The samples from the high forest differed from those from the clearing samples mainly in higher dominances of Clethrionomys glareolu s and Apodemus flavicollis and, in the Orlicke hory Mts., of Sorer minutus as well. In the two mountain ecosystems studied, clearcutting was slightly reflected in changes in species composition but, in contrast to other data, not in substantial changes in the diversity and abundance of the community as a whole.