Sheep and cattle grazing regimes differentially affect ground beetle and ant communities in Mediterranean cork oak woodlands

Grazing has a substantial impact on European grasslands, with both intensification and abandonment posing threats to biodiversity and ecosystem services. Sustainable agroforestry systems integrating grazing, agriculture and conservation offer a multifunctional solution to maintain productivity, biodiversity, cultural heritage and mitigate land degradation. In this study, the impact of grazing on Mediterranean woodlands, characterised by a history of sustained sheep and cattle grazing, was assessed by monitoring ground beetle and ant communities in 18 cork oak woodlands in Sardinia, Italy, in 2016. Environmental variables and forest descriptors characterising each selected area were also quantified. Species richness (SR) and functional diversity (FD) were estimated for each taxonomical group and compared among sheep-, cattle-grazed and ungrazed sites. Multivariate analysis was conducted to investigate differences in species composition among various grazing regimes and to evaluate the influence of environmental variables on insect communities. A total of 607 ground beetles (37 species) and 14,492 ants (35 species) were recorded. Sheep-grazed sites showed the highest species richness (SR) and FD for both taxa. Significant differences were found in beetle and ant assemblages among different grazing regimes. Environmental variables significantly influenced community composition. In particular, altitude and tree density were found to significantly affect both ground beetle and ant composition. Our findings suggest that grazing influences arthropod communities by increasing habitat diversity and biodiversity, particularly in sheep-grazed sites, and indicate that ground beetles and ants are valuable indicators for tracking land-use changes through their population composition.