Riparian structural vegetation types exhibit differential responses to local community drivers

Abstract Riparian vegetation consists of different Structural Vegetation Types (SVTs): woodland, shrubland, and herbaceous communities. Since each SVT may respond differently to abiotic and biotic drivers, our study aimed to disentangle the independent and shared effects of these drivers on distinct SVTs. Using a stratified random sampling approach, we collected 144 plots in a Mediterranean river of central Italy. We applied RDA and variation partitioning to assess the relative importance of local abiotic (lateral gradient, anthropogenic disturbances, environmental factors) and biotic (alien species) drivers on species richness, Shannon diversity index, and community composition of each SVT. After accounting for spatial autocorrelation, abiotic factors emerged as the main filters shaping riparian community assembly. Additionally, our results showed similar responses in the diversity of woodland and herbaceous SVTs to the independent effects of local drivers. In terms of community composition, only woodlands responded to the effects of environment, lateral gradient, and alien species. Consequently, for conservation purposes, different riparian SVTs should be managed separately, as they may respond differently to local drivers. Finally, the shared effects of certain drivers suggest that management measures addressing only a single group of factors are likely less effective.