Floristic diversity of meadow steppes in the Western Siberian Plain: effects of abiotic site conditions, management and landscape structure

Temperate grasslands have suffered from severe habitat loss and degradation worldwide. In Russia, vast areas of forest-steppe grasslands have been converted to cropland during Soviet times, whilst remaining grasslands were often intensively grazed. Contrastingly, the collapse of the Soviet Union have resulted in a massive reduction in livestock numbers and cessation of management. Albeit relatively large natural grassland areas remained in the Western Siberian Plain, their present condition is poorly studied. We analysed plant species composition, functional structure and richness of grassland communities and tested for the effect of local factors (management, abiotic site conditions) and landscape factors (patch size, proportion of land cover types) on diversity patterns. Abiotic site conditions, mainly soil moisture and salinity, differentiated distinct community types. Overall, species richness was highest in meadow steppe communities with lower soil moisture and salinity. Grazing intensity and litter accumulation due to cessation of management were significant negative related to species richness and shaped the functional structure. At the landscape scale, diversity in meadow steppe grasslands was higher in forest-grassland mosaics and in small remnants isolated in a matrix of cropland. Our findings highlight that meadow steppes suffered massively under the historical habitat loss and high grazing pressure. Small species-rich remnants are evidence of the former extent of meadow steppe habitats in agricultural landscape, but are likely threatened by an extinction debt. Low intense, irregular mowing maintained species-rich meadow steppe in forest- grassland mosaics, but currently such practices are declining.