Carex pulicaris abundance is positively associated with soil acidity, rainfall and floristic diversity in the eastern distribution range

Carex pulicaris is considered an endangered species, and further losses are forecast under the influence of even moderate climate change. Local studies indicate that temporal declines in C. pulicaris abundance are positively correlated to decreases in precipitation and increases in air temperature. Determining ecological properties on larger scales than local ones can help develop effective protection programs for the species. We hypothesize that the local relationships observed between C. pulicaris abundance and precipitation, air temperature and soil properties will be confirmed in a spatially-oriented large-scale study performed in situ. Therefore, the present study takes a novel, large-scale integrated approach to (1) precisely characterize the ecological requirements of C. pulicaris within its eastern distribution range, and (2) determine the influence of its community type, soil properties and climatic conditions on its abundance. It was found that C. pulicaris is not a dominant or codominant species in the studied phytocoenoses in the eastern distribution range. Five natural vegetation groups including C. pulicaris, with significantly diverse species compositions, were resolved: well supported Estonian, Polish, Slovak and Radecz groups, and a weakly-supported Ambiguous group. The abundance of C. pulicaris was found to be positively correlated with the composition of the geographically-diversified plant communities and atmospheric precipitation, and to be also negatively associated with latitude and soil pH. Although the species is adapted to a relatively wide range of soil types, such adaptation requires appropriate substrate moisture level and light conditions. The species prefers moist organic and mineral soils and grows on both acid and neutral medium, characterized by a narrow C:N ratio, with various amounts of digestible total P, Mg and N, and low levels of digestible K. Climate change, manifested by reduced rainfall, may be one of the most important predictors negatively affecting the occurrence of C. pulicaris.