Last Remnants of Riparian Wooded Meadows along the Middle Drava River (Slovenia): Species Composition Is a Response to Light Conditions and Management

In the present study, we investigated the species richness and species composition in relation to light and management regime in remnants of wooded meadows within the riparian forests along the middle Drava River in Slovenia. 41 plots of still managed and, at different time periods (<5 yrs, 5–15 yrs, >15 yrs), abandoned riparian wooded meadows (RWM) were sampled. In addition to vegetation relevés, light intensity (PAR) was also measured in plots. Within the still-managed RWM, two floristically distinct types were recognized using TWINSPAN analysis: meadow-like and forest-like. Light intensity differed significantly between types. The CCA of active RWM showed a significant relation between species composition and light conditions. The number of species per relevé on active RWM was negatively correlated with light intensity – in contrast to North European wooded grasslands. This could be explained by the influence of species-rich riparian hornbeam forests that contribute many understorey species, in contrast to naturally mesotrophic meadows. CCA of both active and abandoned RWM demonstrated that light was a good predictor of RWM species composition and that abandonment caused profound changes in floristic composition. The species turnover during succession was more pronounced in less shaded meadow-like RWM where more light-requiring (grassland) species occurred. Species richness was the highest in active forest-like RWM. There were no significant differences in species richness between active meadow-like RWM and groups of abandoned RWM. The remains of riparian forests stretching along the flood plains of Central and Eastern Europe are considered one of the most natural ecosystems in the prevailing agricultural landscape. But naturalness could be in many cases only the consequence of abandonment of ancient land-use practices, like grazing of livestock, cutting between the trees, litter collecting, etc. Examination of the middle Drava River in Slovenia suggests the need to recognize the remains of ancient cultural landscape.