Small mammal community changes during forest succession (Pakruojis district, north Lithuania)

Small mammal communities were investigated in three stages of the meadow-forest succession (natural meadow, 5–10-year-old forest plantation [FP] and 15–20-year-old spruce–birch forest stand [FS]) in the Pakruojis forest (north Lithuania) in 2007–2011. These three consecutive forest succession phases occurred after a forest had been planted in a natural meadow. Four hundred and eighty-eight individuals of nine small mammal species were registered in the above-mentioned three habitats during the four-year study period. We found that the highest species diversity was in the natural meadow: Shannon’s diversity index H = 2.65, Margalef’s species richness index d = 1.68 and Pielou species evenness index e = 0.84. The above-mentioned indexes showed a smaller small mammal species diversity in the FP: Shannon’s H = 2.54, Margalef’s d = 1.47 and evenness e = 0.80. The lowest species diversity was registered in the FS: Shannon’s H = 2.08, Margalef’s d = 1.21 and evenness e = 0.74. The highest relative abundance of small mammals was registered in the FP (33.8 ± 3.9 ind./100 trap-days) and the lowest in the natural meadow (17.8 ± 2.1 ind./100 trap-days). Small mammal species abundance in the FS was 25.8 ± 2.0 ind./100 trap-days. During the investigated process of forest succession, the dominance of one species, bank vole (Myodes glareolus), was more and more expressed (Simpson’s index of dominance c = 0.30 in the FS against merely 0.21 and less in other areas). It was not only the composition of species of the small mammal community that was different in each stage of forest succession, but also the dominant species – from the common shrew (Sorex araneus) and yellow-necked mouse (Apodemus flavicollis) in the natural meadow to the absolute dominance of one species (My. glareolus) in the FS (48.9% of all individuals trapped in the FS).