Kathrin Stürzenbaum



Potential effects of box eider control measures and vertical stratification of xylobiontic beetles in floodplain forests of the Donau-Auen National Park, Lower Austria

Xylobiontic beetles represent a substantial fraction of the biodiversity of forest ecosystems and are useful bioindicators for evaluating effects of forest management measures. This study was conducted in the Donau-Auen National Park in Lower Austria, one of the largest remaining semi-natural floodplain forests in Central Europe. There, for five months in summer 2012, beetles were sampled using flight interception traps, a widely used method for inventorying the fauna of wood inhabiting beetles. The aims of the study were to investigate the differences of xylobiontic beetle assemblages between two forest strata (understory and canopy) and the possible effects of an abruptly increased volume of fresh dead wood on them. The dead wood originated from the neophytic Box Elder (Acer negundo), that is becoming more and more widespread in riparian landscapes, and was girdled or felled at several locations in the national park to prevent a further dispersal. At five sites where such control measures had been applied beetles were sampled with one flight interception trap in the understorey and one in the canopy, the same was done at five reference sites without management. In total, 267 species of xylobiontic beetles (of 49 families) were recorded. Species richness, total abundance and also the composition of beetle assemblages differed significantly between forest strata. Total abundance was higher in the understorey, whereas species richness was higher in the canopy. There is no evidence however for an effect of the control measures on box elder on either total abundance, species richness or the composition of assemblages. The distribution of the functional groups of xylobiontic beetles seems to correlate neither with stratum nor with site type. The complete lack of an influence of the newly available dead wood material on xylobiontic beetle assemblages can be accounted for by the following factors: for one thing the time lag between implementation of control measures and sampling (less than one year) may have been too short for beetles to react, or the neophytic origin of the dead wood made it unsuitable for autochthonous beetle species.