Hydrologic fluctuations trigger structural changes in wetland-dry grassland ecotones but have no 1 effect on ecotone position 2 3 Dynamics of wetland-dry grassland ecotones 4 5 ; Phone: +36 62 546 952; Fax: +36 62 546 949 11 12 Ecotones between plant communities have received considerable attention among ecologists in the 13 context of fragmentation, climate change and the management of heterogeneous landscapes. However, 14 the predictability of ecotone dynamics is low and the processes taking place within ecotones are still 15 poorly understood. In this study we aimed to characterize the positional and structural dynamics of 16 thirteen ecotones in an ecotone-rich steppe-wetland landscape of Hungary in relation to the inter-17 annual fluctuations of water regime and the gradients of elevation and of soil composition. According 18 to our results, the ecotones between steppe and wetland communities were sharp and their positions 19 coincided with those places in the landscape where the rate of change in elevation was the highest, 20confirming that microtopography is a major determinant of ecotone position. Soil boundaries were 21 also detected, mostly downhill to the ecotones. Interestingly, the fluctuations of the water supply had 22 make wetland edges more sensitive to edge effects; thus, the cause-effect relationship is difficult to 31 disentangle. 32 33