Effects of grazing and mowing on ground-dwelling predatory arthropods in a semi-arid grassland

The arthropod communities are important component in grassland ecosystems and are largely affected by management. However, the information on the effects of different grassland management on ground-dwelling predatory arthropods are very limited, especially for the natural steppe grasslands in semi-arid regions. Here we investigated the dynamic patterns of predatory arthropod communities (Carabidae and Araneida) using the Pitfall-trap method in the grasslands subject to 6 management treatments of full-season grazing, spring-summer grazing, summer grazing, summer-autumn grazing, autumn mowing, and unused grassland in a natural steppe grassland in central Inner Mongolia; each management treatment was replicated by three experimental paddocks. The results showed that (i) a total of 305 ground-dwelling predatory arthropods were captured, belonging to 31 genera, 11 families, 2 orders and 2 classes; and the dominant genera were Craspedonotus, Harpalus, Pardosa and Gnaphosa, accounting for 14.75%, 12.79%, 11.15% and 15.74% of the total genera, respectively. (ii) Compared to unused grassland, grazing significantly reduced the individual number, biomass and genus diversity of ground-dwelling predatory arthropods, and these inverse impacts were smaller under summer-autumn grazing than other grazing; while autumn mowing increased the biomass of the arthropods in summer. (iii) Grazing and mowing had bigger effects on the large than small ground-dwelling predatory arthropods. Our results deepen the understanding of the dynamic patterns of ground-dwelling predatory arthropods in grasslands subject to different management, and it is important to take these dynamic patterns in evaluating management effects on grassland ecosystems, especially for the development of sustainable grassland management systems.