Seasonal change of dung beetles in Hungarian pastures, wood-pastures and forests – knowledge for the conservation of decomposers

Abstract

Dung beetles (Scarabaeidae: Scarabaeinae, Aphodiinae and Geotrupidae) have an important role in several ecologically and economically valuable ecosystem functions and services through dung decomposition and by improving soil characteristics. Their number has a decreasing tendency throughout in Europe and thus, the ecosystem functions and services they provide are damaged. Main reason of decline is the change of farming practices, namely the decrease of grazing livestock and seminatural pastures. Until the second half of the 20th century wood-pastures were traditional pasture areas and grazing in forests also had great importance. However, forest grazing has now almost completely disappeared, several wood-pastures are under restoration and grazed again, primarily as conservation management. The aim of the study was to describe the structure and functional composition of the dung beetle assemblages, its seasonal changes in wood-pastures, compared to forests and pastures. Our study was carried out in three landscapes in the Északi-Középhegység (North Hungarian Mountains) and the Dunántúli-Középhegység (Transdanubian Mountains) regions. Three sampling points per area were designated in each habitat. The sampling of dung beetle assemblages was carried out in spring (May), summer (July) and autumn (October) of 2016, using pitfall traps baited with the dung of cattle, horse and sheep, the three most important livestock species in region. Pitfall traps were emptied after one week. Collected beetles were identified at species level and were categorized into functional groups. Average dry weight of each species were measured as well. In all, more than 70,000 specimens of nearly 60 species were collected and classified into four functional groups: small rollers, big tunnelers, small tunnelers and dwellers. The seasonal pattern was similar in all the three areas: the highest species richness was in spring what is gradually declined to autumn. Densities and dung preferences were significantly different in the areas. The composition and biomass of functional groups also differed between habitat types and seasons. In general, pastures were dominated by small tunneler species in spring and summer, while the forests by the big tunnelers in summer. In autumn the abundance of dwellers increased in all habitat types. The dung beetle assemblages of wood-pastures show a transition between the assemblages of forests and pastures. In these partly wooded areas the species of forests and open grasslands may occur together. Therefore, we recommend special conservation efforts to maintain and restore wood-pastures and to graze with different livestock, to secure the functioning of diverse dung beetle asssemblages.