Biology session

Nowadays the role of soil biota in ecosystem services is a relevant topic. It is especially important in habitats endangered by intensifying urbanization, where the maintaining of natural communities and the functioning of ecosystems matter the most. The global urbanization, the similar structure and characteristics of cities the introduction of non-native species all lead to the homogenization of urban soil fauna (biotic homogenization). The establishment of cosmopolitan and introduced species endangers natural assemblages. As a metropolitan area, Budapest gives an ideal location to investigate this process.

The present study aimed to investigate the communities of macrodecomposer arthropods, first of all terrestrial isopods (Isopoda: Oniscidea) and millipedes (Diplopoda), based on their species richness and species composition in differently degraded urban forest patches. We hypothesized that mostly native species dominate natural or slightly disturbed habitats while in intensely urbanized ones cosmopolitan and synanthropic species prevail.

The sample sites were chosen randomly in 23 differently disturbed forest patches in Budapest’s Buda side. Hand sorted samples (6x10 minutes in each plot) were taken during May, in 2016. We also recorded the botanical characteristics of the forest patches. We calculated urbanization indices based on the proportion of built-up areas and vegetation cover in the 1 km2 area of the sample sites, using digital aerial images. The collected individuals were identified to species level, and they were also classified by their habitat preferences. Isopods were also qualified by naturality index (TINI).

The sampling resulted 11 isopod and 10 diplopod species. According to our data, the number of species per sampling plots did not depend on urbanization gradient, but that had an effect on the species composition (p=0.003). Botanical characteristics, such as quantity of dead wood also had a significant effect on species composition (p=0.050). There was a negative correlation between the naturality indices of isopods and the areas’ urbanization indices (p=0.035).

We concluded that the knowledge of the decomposer macro-arthropod fauna species composition might be a good tool for estimating habitat quality and for monitoring in areas worthy of protection. Our study proved the hypothesis that more urbanized habitats harbour more non-native/generalist species. This change in fauna composition might have an effect on biodiversity value, and also on the functioning of the ecosystems.