Passive restoration of subtropical grasslands leads to incomplete recovery of ant communities in early successional stages

Understanding how land use and management practices affect biodiversity is essential for developing effective restoration and conservation strategies. Here, we used ant communities to evaluate the effects of historical land uses (former agriculture or tree plantation) and current management (grazing, burning, mowing, and fertilizing) in subtropical grasslands. We also examined how ant species richness and composition are affected through changes in resource diversity and habitat structure. We classified 80 study sites in southern Brazil into two groups: permanent and secondary grasslands. Permanent grasslands presented high, medium or low management intensities that had never been under other land use. Secondary grasslands are former grasslands that were used for agriculture or pine plantations in the past, followed by passive restoration. We sampled ant communities with D-Vac suction in three multiplots per site in 2013–2015. We found that secondary grasslands had lower ant species diversity and different community composition than permanent grasslands. Ant diversity did not differ among permanent grasslands, but composition was markedly different, especially when comparing medium and high management intensities with low. Additionally, ant richness in secondary grasslands was mainly mediated by a decreased resource diversity (i.e., plant species richness) and grass cover, while burning and mowing management increased ant richness by increasing resource diversity. Our results indicate that passive recovery of grasslands in early successional stages after other land uses leads to incomplete recovery of ant communities, as important resource and structure-related drivers of ant species remain altered. In contrast, traditional management practices promote ant diversity.