Epigeic fauna (with emphasis on ant community) response to land-use change for sugarcane expansion in Brazil

Abstract

The epigeic fauna, ground surface-dwelling invertebrates that inhabit leaf-litter, acts on multiple soil processes and key ecosystem services and is threatened by global land-use change (LUC). In Brazil, LUC for sugarcane expansion over extensive pasture has been taking place for promoting bioenergy production; however, conventional sugarcane cultivation includes monoculture, periodic soil tillage and agrochemicals may alter the quantity and quality of crop residue inputs, soil habitats and communities of soil fauna. Thus, a field study at three sites in central southern Brazil was conducted to evaluate if the expansion of sugarcane cultivation affects soil epigeic fauna. In each site, we sampled epigeic fauna in areas under LUC from native vegetation to extensive pasture, and from that to sugarcane. The epigeic fauna was collected using pitfall traps and then quantified and classified in taxonomic groups (Order, Class, Family). In addition, as a focal organism group, ants were classified at the species level. Overall, 13 taxonomic groups were identified, in which the Formicidae family was the most abundant group (i.e., 67% of individuals), followed by Diptera (13%), Araneae (5%) and Coleoptera (4%). Land transition from native vegetation to pasture increased fauna abundance by 27% but reduced the diversity of epigeic fauna community by 43%. In contrast, sugarcane expansion over extensive pasture reduced fauna abundance (−22%), did not alter the diversity of the invertebrate community at a broad taxonomic level, but decreased species richness of the dominant taxa (ants) by 55%. Ant individuals were classified into 37 species, allowing to verify that sugarcane cultivation over pastures decreased both the abundance and richness of ants and altered community composition. Ant species Ectatomma brunneum were more sensitive to LUC and, therefore, could be characterized as potential indicators of disturbed environments. We demonstrate that sugarcane expansion over pasturelands reduces the total abundance of the soil epigeic fauna, and that effects on fauna diversity vary from broad to fine taxonomic resolutions. Further studies are needed to evaluate if the declines in fauna abundance and ant species richness impair specific soil functions and soil-related ecosystem services.