Land mollusc faunas of Bialowieza Forest (Poland), and the character and survival of forest faunas in the North European Plain

The land mollusc faunas of three plant associations in the Bialowieza Forest, Poland, were sampled in 2001/2. Overall 51 species were recorded, of which 45 were found in Circaeo-Alnetum (CA; floodplain forest), 38 in Tilio-Carpinetum (TC; mixed forests on eutrophic soils), and 35 species in Melitto-Carpinetum (MC; mixed forests on meso- to oligotrophic soils). CA forests hold a number of wetland species but, at site level, their faunas are slightly poorer and more variable than those in TC, which are rich and uniform. MC faunas are poorer, and many species occur there infrequently and in low numbers. Taken with earlier surveys in the forest, these results give a picture of the undisturbed fauna of forests off limestone on the North European Plain. They are compared with those from other lowland forests in Poland, and more widely across northern Europe. While this forest fauna is now confined to small areas, it appears to have survived intact in sites not subject to gross pollution or disturbance. There are changes in species composition across the Plain, discussed in terms of historical biogeography. A comparison is also made with tropical forest; where there is a similar pattern of Holocene habitat change, the faunas are remarkably similar in many aspects of diversity.