The aim of our study was to assess the small scale distribution (up to several m²) of hibernating forest-dwelling snails in relation to small-scale environmental factors, like litter composition, soil temperature and humidity or vegetation cover. The study was conducted in the ”Dębno nad Wartą” (local name) natural reserve, western Poland, in December 2006. A novel, cartographic method was applied for analysing and illustrating the small-scale distribution and habitat preferences of the snails. Four permanent study plots (15 m²) were established in 50 m intervals. Each plot was divided in fifteen 1m² squares, and from each square a litter sample was taken and analysed (60 samples in total). 17 snail species were recorded (6–13 species per plot; 0–8 per square). The distribution of particular species was clustered as its coefficients of variation were high (CV%> 150) as well as was the small-scale distribution of the total abundance of all the species (CV% = 122). The most uniformly distributed and frequent (C% of all samples) species were Trichia hispida (Linnaeus) (CV%= 153; C% = 45), Cochlodina laminata (Montagu) (206; 30) and Perforatella incarnata (O.F. Müller)(152; 37). Among frequent species the greatest value of CV% (425) and therefore the most patchy distribution was recorded for Ruthenica filograna (Rossmässler). According to the results of CCA, this species, together with Vitrina pellucida (O.F. Müller) (CV% = 296), and Clausilia bidentata (Ström) (CV% = 291), were the most stenotopic, wintering in specific microhabitats with low herb layer coverage, elm leaves prevailing in the litter and high percentages of hornbeam, ash, birch and alder leaves. In turn, for Perforatella rubiginosa (A. Shmidt) (CV% = 440) and Perforatella bidentata (Gmelin)(CV% = 440), also the species with patchy distribution – optimal wintering conditions were found in places with a higher soil temperature and the litter consisting mainly of oak leaves. The remaining snail species seem to be more eurytopic and winter in microhabitats with intermediate conditions. The results of the present study show that for the distribution of majority of species studied the most important factor is the proportion between the coverage of litter and herbaceous vegetation cover. The species richness of the malacocenoses studied strongly depends on the diversity of litter, since particular species prefer leaves of different trees.
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