The Changes in the Forest Vegetation on the Danube River Aggradation Mound Affected by Water Regime Changes

Abstract This article is focused on the specific vegetation, which has formed from the floodplain forests on the aggradation mound (elevated sediment deposition) along the original Danube river in Slovakia in the part affected by Gabčíkovo waterworks that was put in operation in 1992. As a result of water regime changes, when a major part of the Danube water flow was redirected to the Gabčíkovo hydroelectric power plant, original floodplain forests on the aggradation mound began to suffer from a water deficit, which is also supported by shallow soils formed mostly on the gravel sediments with limited capillary rise of groundwater. It has triggered successional processes leading to the degradation of forest with changes in all layers. To identify these changes and development trends, we analyzed vegetation data from 2002, 2012, and 2022. The results indicate that the process of secondary succession of the original floodplain forest continues. This includes mainly an increase in the number of species, especially those typical for grasslands and synanthropic habitats. From an environmental point of view, the spread of some invasive species is striking. Ordination method (canonical-correlation analysis [CCA]) confirmed light, moisture, number of species, and Shannon–Wiener index as the main factors determining relevés’ variability.