With farmland afforestation becoming common policy in many European Union countries, we studied how early forest succession (from meadow to young stand) influences small mammal species composition, diversity, abundance and biomass. Despite numerous investigations into forest succession, almost no attention has been given to the small mammal community change in the early-successional forest ecosystems, starting with the pre-forest habitat and ending with stand formation and the establishment of tree dominance. We compared small mammal communities in meadows at the initial stage of regrowth (with saplings less than 10 cm in height), in young forest (5-10 years old) and more advanced forest (15-20 years) in both cases of human-induced forest succession, where the trees had been planted, and natural forest succession, where natural regrowth of meadows had occurred.

The greatest diversity of small mammal species was recorded in the meadow (H = 2.95), with a lower diversity found in the young forest (H = 2.61) and even lower in the advanced forest (H = 2.04), the last habitat being the most monodominantic. The order of species dominance from Microtus sp. (M. arvalis, M. agrestis), Myodes glareolus, Apodemus flavicollis, Sorex araneus, A. agrarius in the meadow changed to M. glareolus, S. araneus, M. arvalis, M. agrestis in the young forest and to M. glareolus, A. flavicollis, S. araneus in the advanced forest. The lowest relative abundance of small mammals was recorded in the meadow (18.19 ± 2.27 ind. Per 100 trap-days), with Microtus voles being the most abundant. Relative abundance was higher in the young forest (22.72 ± 2.25 ind. Per 100 trap-days), with Myodes glareolus being the most abundant (7.59 ± 0.96 ind. Per 100 trap-days) and at its highest in the advanced forest (23.91 ± 2.77 ind. Per 100 trap-days), again with M. glareolus being the most abundant (15.54 ± 2.35 ind. Per 100 trap-days).

Thus, our analysis suggests that that during early meadow-forest succession, the diversity of the small mammal community declines - the number of species decreases as typical meadow species are lost due to the transformation of the habitat and one or a few species became dominants. However, the relative abundance of the small mammals increases. Biological indices of small mammal communities differed between natural and human-induced meadow-forest succession.