Threatened alvar grasslands in NW Russia and their relationship to alvars in Estonia

Alvar grasslands are thin-soil calcareous grasslands on Silurian and Ordovician limestone bedrock. They are considered unique plant communities for northern Europe and America with a high conservation value. Until now, European alvar grasslands have only been described in Sweden and Estonia. We described species-rich alvar grasslands on the Izhora plateau, NW Russia and compared this vegetation with that of Estonian alvar grasslands. Floristic composition and environmental conditions of Russian alvars were similar to Estonian alvar grasslands on thicker dry soil. Russian alvars are isolated from similar communities in Estonia, but extensive transport of domestic animals from Estonia to NW Russia in past centuries has probably enhanced species dispersal. Some characteristic Estonian alvar species were missing in NW Russia because it lies outside their natural ranges. Other differences in vegetation were explained by higher atmospheric nitrogen deposition and younger age of Russian sites. In NW Russia the alvar grasslands were small, but several red-listed plant species were present. In order to preserve European alvar vegetation effectively, Russian alvar grasslands need further study and conservation as an outpost of this threatened vegetation type.