Andreas Zöchling

Zöchling

zoechling.andreas@yahoo.de

PDF im Hochschulschriften-Service der Universität Wien

Auswirkungen unterschiedlicher Bewirtschaftungsweisen und Nutzungsintensitäten von Almen auf die Tagfalterfauna im NP Gesäuse

One of the major threats for butterflies is the loss of suitable habitats through either intensification or complete abandonment of traditional land-use practices. This process also takes place on Alpine mountain pastures. Unmanaged meadows below the natural climatic forest line will be subject to encroachment by shrubs and trees. Especially for heliophilic butterflies, this has a negative impact. Extensively managed grasslands are generally regarded as favourable for butterfly diversity and the occurrence of rare species. To evaluate the importance of grazing on Alpine pastures for butterflies and diurnal moths, I investigated 66 sample plots (50 x 50 m²) on 13 different pastures in the National Park Gesäuse (Austria). Sites ranged from abandoned ones to intensively grazed pastures. All sample plots were investigated three times during the growing season 2011. In addition to sight records of the target insect groups, different environmental variables were assessed. I used multivariate models (GLM, GLMM, distLM) for data analysis and ordination procedures to visualize my results. Overall, I observed 95 species (3065 individuals) of diurnal Lepidoptera, including 66 species (2545 individuals) of butterflies (Hesperioidea and Papilionoidea). The intensity of grazing had no significant influence on the diversity and species richness of diurnal Lepidoptera in general, yet with increasing grazing intensity the proportion of habitat specialized species and species which prefer natural/semi-natural habitats decreased on mountain pastures. Also the number of sight records per site decreased at higher grazing pressure. The main predictor for butterfly diversity and species richness was the elevation of the sample plot or average elevation of the mountain pasture. In contrast abundance was mainly influenced by availability of nectar plants. Butterfly communities differed rather weakly between grazing intensities. Only abandoned mountain pastures had obviously different communities. Abandoned plots were more similar in faunal composition than grazed plots at different grazing levels. As with species diversity, elevation had the strongest influence on butterfly species composition, followed by predictors that describe grazing intensity and nectar availability. To keep species richness and abundance of Alpine butterflies and diurnal moths at a high level, it is important to maintain grasslands rich in flowering plants as nectar sources. The differences between communities on old fallow pastures and still grazed pastures leads to the conclusion that different stages of succession are important for certain groups of butterflies. Therefore management should aim at creating a mosaic of succession stages.