Browsing by Author "Lähteenmäki, Saija"

Dung beetles affect ecosystem functioning in agricultural landscapes. Among these beetles several functional groups decompose cattle dung and contribute to recycling its nutrients back to the soil. To-day many Finnish dung beetle species are threatened because of habitat change and fragmentation. Therefore, the impacts of changes in dung beetle community structure on ecosystem functioning needs to be addressed. However, many earlier studies of dung beetle functions have focussed only on small-scale manipulations with possible implications for interpretation of the results on larger scale. The aim of this study was to assess whether large-scale enclosures can be used to manipulate dung beetle communities in Finland. With this new method I wanted to examine how different dung beetle communities affected dung decomposition and nutrient cycling. I also wanted to examine wheth-er grazing pressure affected dung decomposition. I used two types of mesh enclosures to create different communities of Aphodius and Geotrupes species. In small mesh enclosures I added dung beetles manually, while in the large mesh enclosures the smaller Aphodius species could get through the mesh, and Geotrupes were then added manually to some of these enclosures. During the experiment I repeatedly measured the amount of dung beetles inside and outside of the mesh to assess the performance of the enclosures. Within enclosures I created plots that reflected different grazing pressure. In every plot I placed a dung pat which I then weighed six times during the summer. At the end of the experiment I studied the effect of dung beetles on nutri-ent cycling by weighing the biomass of grass. Overall, I found that the large enclosures are usable and work well in Finland. My results from the enclosures with the bigger mesh size showed that Geotrupes are more efficient decomposers of dung than are Aphodius. However, there were no significant differences between Aphodius and Geotrupes in enclosures made of smaller mesh. Thus, different enclosures may have affected the functioning of the dung beetles because I put the beetles to some enclosures and to some they could get through the mesh. Dung decomposition rates changed remarkably between the different grazing pressures. The end weight of pats was lighter in short grass compared to pats in long grass. It is possible that this reflects microhabitat selection by beetles choosing the warmer pats in the short grass. Dung beetle community structure did not affect rates of nutrient recycling, as measured by grass growth. In conclusion, the results of my study suggest that large-scale enclosures can be effectively used to study dung beetle functions in grassland habitats. This study also confirms earlier observations re-garding the significance of different functional groups of dung beetles, and shows that the grazing envi-ronment may have an important impact on the ecosystem functions provided by dung beetles.