Effects of grazing on species richness, functional trait composition, and functional diversity in subtropical grasslands

• Species richness decreased under grazing exclusion; • Plant traits reflecting convergence were related to plant structure, life span, and clonal growth; • Grazing consistently shaped functional structure across Pampa and Highland grasslands; • Functional diversity remained stable across grazing treatments. Grazing is a disturbance that affects floristic composition, vegetation structure and functional patterns in grassland ecosystems. In this study, we aimed to assess the effect of grazing intensity on (1) species richness and composition; (2) plant trait assemblages and (3) functional diversity of grassland vegetation. We experimentally assessed the effect of three grazing treatments (continuous, deferred and exclusion) on grassland vegetation in six sites situated in Pampa and Highland grasslands in Southern Brazil. We compiled functional traits associated with grazing (maximum plant height, life form, belowground storage organs, life span, leaf morphometry and diaspore type) from our regional grassland functional traits database. We explored the relations among different sites and grazing treatments through Principal Coordinate Analysis (PCoA). To analyze the effects of grazing treatments on community-weighted mean functional traits, we used a method based on Procrustes correlations for discriminating trait-convergence and trait-divergence assembly patterns (TCAP and TDAP). Functional diversity (Rao’s quadratic entropy), species richness, and community-weighted mean traits (CWM) were analyzed in relation to grazing treatments using linear mixed models, with site included as a random effect. Plant species richness was lower in the grazing exclusion treatment. Functional diversity did not differ between grazing treatments. Nevertheless, we found TCAP affected by grazing intensity for the following traits: species life span, fruit as dispersal unit, rhizomatous and stoloniferous life form. PCoA revealed there were less rhizomatous plants in the exclusion plots. Therefore, species composition and functional structure of communities in grasslands in southern Brazil are partially explained by grazing intensity.