Landscape and grazing management affect dung beetle communities in California

Abstract

Agroecosystem management can have large impacts on arthropod communities, with downstream consequences for ecosystem function. In grazed agroecosystems, dung beetle nesting and consumption activities contribute to critical ecosystem services such as aerating soils, dispersing seeds, suppressing pathogens, decreasing fly eggs, decreasing dung greenhouse gas emissions, and increasing nutrients in the soil. Grassland grazing management as well as the landscape cover surrounding a grassland can impact dung beetle abundance and diversity with implications for downstream ecosystem function. One third of California is grazed by livestock, however, there are few studies of dung beetles in these agroecosystems. Our study examines the effect of grazing management, including the time spent grazing and animal density (the number of days grazed and number of animals), as well as how landscape cover, including surrounding grasslands, forests, and wetlands, affect dung beetle abundance and richness. We also examined how seasonality or temperature and the year in which we sampled affect dung beetle communities. We found that grazing management affects richness. While increases in the number of days grazed was associated with higher dung beetle species richness, we found that increased grazing density was associated with lower dung beetle species richness, showing that increasing grazing density may have a detrimental effect on richness. We also found that the amount of wetland cover in the landscape was positively associated with abundance and species richness, and grassland cover was positively associated with species richness. Dung beetle abundance did not shift by year, but did shift with sample time, while dung beetle richness shifted with year and sample time. Our results differed by beetle functional type and species. The results demonstrate the importance of both local disturbances and more permanent landscape surroundings for arthropod communities in agroecosystems.