Changes in the composition of sand grasslands along a climatic gradient in Hungary and implications for climate change
Kovács-Láng, E.; Kröel-Dulay, Gy.; Kertész, M.; Fekete, G.; Bartha, S.; Mika, J.; Dobi-Wantuch, I.; Rédei, T.; Rajkai, K.; Hahn, I.
The primary objectives of this study were (1) to document the changes in the composition and structure of a semiarid grassland (Festucetum vaginatae) along a climatic gradient in Hungary, and (2), by applying the concept of "Space for Time Substitution", to form hypotheses on the possible effects of a predicted climate change on these grasslands. Three sites were selected along a 200 km transect in the sand forest-steppe vegetation of the Hungarian Plain. Percentage canopy cover was estimated by species in 30 pairs of randomly located 16 m2 quadrats at each site. Species were classified based on their phytosociological character, geographic distribution, and Raunkiaer life form. We found that species richness, canopy cover, diversity, and the relative importance of dry grassland generalists, forest species, and Hemicryptophytes decreased, whereas the relative importance of sand grassland specialists, Therophytes, and species with Continental and Sub-Mediterranean distribution increased with increasing aridity. We found that the existing differences in climate along the gradient are comparable to the predicted climate change for the region, therefore, the changes observed along the gradient may serve as hypotheses on the possible future changes in grassland structure and composition. However, the rate of changes is unpredictable. The indirect effects of climate, such as higher forest cover and soil organic matter content at the wet end of the transect, may be important in driving the present differences in grassland composition, and may buffer or considerably slow down the expected changes.