Dung beetles diversity and their role in nutrient cycling in livestock systems of the dry Chaco

Abstract

Dung beetles represent one of the main animal groups involved in the cycling of cattle dung, modifying soil physicochemical properties, and reducing parasite incidence. However, their diversity and activity in cattle areas depends on conserving critical resources and conditions, including native vegetative composition, microclimatic and soil conditions. Whereas most previous studies were conducted in humid forests, our objective was to experimentally study the diversity and role of dung beetles in soil nutrient dynamics in native forests and shrub savannas with cattle ranching in the dry Chaco of Argentina. Using pitfall traps, we collected dung beetles in both habitats. In cow exclusions, we buried two plastic containers filled with soil and two kg of fresh cow dung on the surface and covered one with a mosquito net to prevent the access of dung beetles. After three months, we collected soil samples and analyzed nutrient contents and soil structure. Contrary to previous studies, the abundance and richness of dung beetles were higher in savannas than in native forests. In both habitats, the activity of dung beetles strongly increases phosphorous and potassium contents; however, consistent with the higher abundance, this effect was more marked in shrub savannas. In addition, we observed higher contents of total organic carbon, electrical conductivity, and calcium in native forests. Our results emphasize the critical role of dung beetles in maintaining soil quality in the most extended cattle management practices of the dry Chaco. Moreover, our results were opposite to previous studies conducted in humid forests, which could be associated with greater tolerance of native species to extreme microclimate conditions in the dry Chaco.