Structural changes of a pannonian grassland plant community in relation to the decrease of water availability

Climate change and other local factors in Central Hungary resulted in a severe water table drawdown during the last few decades. Several studies with different methodical approaches have already been conducted in the region to examine the reaction of the vegetation to the new conditions. In this paper we report the results of a unique, long-term vegetation study of a permanent site, which was also suffering from the loss of its original water supply. The site consisted of a drier section with sandy steppe communities and a wetter one located in an interdune depression. By using diversity measures, relative ecological indicators, flora element classifications, Raunkiaer’s life-form categories and Borhidi’s social behaviour types we could show that both sections were influenced by the water table drawdown, though most shifts were more prominent in the wet section. According to the results the vegetation of the wet section was in a drying phase, it was getting more thermophilous and its continental character was getting stronger. We found that the vegetation of both sections had undergone a transitional degradation before the study was started and during the study it was in a regeneration phase towards a new natural state. This fortunate process proves that these communities have a potential to adapt to drier conditions, but beside the decrease of the overall habitat diversity we could also detect an obvious negative trend in the productivity, which we consider a severe general trend for the entire region