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Grazing exclusion may lead to biodiversity loss and homogenization of naturally heterogeneous and species-rich grassland ecosystems, and these effects may cascade to higher trophic levels and ecosystem properties. Although grazing exclusion has been studied elsewhere, the consequences of alleviating the disturbance regime in grassland ecosystems remain unclear. In this paper, we present results of the first five years of an experiment in native grasslands of southern Brazil. Using a randomized block experimental design, we examined the effects of three grazing treatments on plant and arthropod communities: (i) deferred grazing (i.e., intermittent grazing), (ii) grazing exclusion and (iii) a control under traditional continuous grazing, which were applied to 70 x 70 m experimental plots, in six regionally distributed blocks. We evaluated plant community responses regarding taxonomic and functional diversity (life-forms) in separate spatial components: alpha (1 x 1 m subplots), beta, and gamma (70 x 70 m plots), as well as the cascading effects on arthropod high-taxa. By estimating effect sizes (treatments vs. control) by bootstrap resampling, both deferred grazing and grazing exclusion mostly increased vegetation height, plant biomass and standing dead biomass. The effect of grazing exclusion on plant taxonomic diversity was negative. Conversely, deferred grazing increased plant taxonomic diversity, but both treatments reduced plant functional diversity. Reduced grazing pressure in both treatments promoted the break of dominance by prostrate species, followed by fast homogenization of vegetation structure towards dominance of ligneous and erect species. These changes in the plant community led to increases in high-taxa richness and abundance of vegetationdwelling arthropod groups under both treatments, but had no detectable effects on epigeic arthropods. Our results indicate that decision-making regarding the conservation of southern Brazil grasslands should include both intensive and alleviated levels of grazing

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Aims We offer a first classification of South Brazilian grasslands (Campos Sulinos) based on quantitative vegetation data and describing grassland types in terms of dominant and indicator species. Location South Brazilian grasslands (Paraná, Santa Catarina, Rio Grande do Sul states). Methods We described vegetation plots in 167 sampling units throughout the region using a stratified nested design, totalizing 1,502 1 m² quadrats. We classified vegetation using cluster analysis based on Bray–Curtis dissimilarities, establishing three vegetation types and ten subtypes. We conducted indicator species analysis within the resulting subtypes, and for all possible combinations of subtypes. Results In the cluster analyses, a clear separation of poorly drained grasslands from the drier sites appeared. Further, a clear distinction between grasslands in the South Brazilian highland region, situated in the Atlantic Forest biome, and the grasslands of the Pampa biome, to the south, emerged, reflecting climatic and management differences. Highland grasslands showed lower species cover dominance, while in the Pampa, Paspalum notatum clearly was the most important species and the abundance of exotic species was higher. Conclusions Our study provides the first classification of South Brazilian grasslands based on quantitative vegetation data recorded in a standardized sampling design. The data support the division of grasslands into the main phytogeographic units of the region (Brazilian biome classification). Grasslands in these two regions also differ in terms of species dominance pattern (higher dominance in Pampa grasslands, likely also due to higher grazing levels) and in terms of conservation state (low presence of exotic species in highland grasslands). Our results are important for conservation policies, which can now consider the presence of different grassland types in different region, but more data will be necessary for a more detailed classification that considers different abiotic features in more detail.

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Habitat loss is one of the greatest threats to biodiversity, exerting negative effects on the ecological viability of natural vegetation remnants. The south Brazilian grasslands belong to one of the largest temperate grassland regions in the world, but have lost 50% of their natural extent in the past 35 years. To date, there is no empirical evidence for the effects of habitat loss on these grasslands' biological diversity, undermining their conservation. Using data from a large‐scale biodiversity survey, we asked if local plant communities respond to levels of habitat loss representative of the entire region (≤50%). Vegetation in grassland remnants was sampled in 24 landscapes at three localities each, using nine plots per locality. To investigate whether species losses were a consequence of stochastic or nonrandom local extinctions and whether plant communities became more homogenized, we evaluated species richness, beta‐diversity components (spatial turnover and nestedness), and phylogenetic diversity, in respect to landscape change. In part of the landscapes, arthropods were sampled to investigate if loss of plant diversity had a cascading effect on other trophic levels. We evaluated generic richness of ants, an omnivore group with high levels of plant associations, in respect to a plant community's phylogenetic diversity. Local plant communities in landscapes with less grassland cover had fewer species, less spatial turnover, increased nestedness and lower phylogenetic diversity. Our results suggest that the observed species loss can be linked to taxonomic homogenization and is nonrandom, decreasing evolutionary diversity within the community. Furthermore, ant richness declined by 50% in plant communities with the lowest phylogenetic diversity, suggesting that effects of habitat loss propagate to higher trophic levels. Policy implications. We conclude that the biological diversity of south Brazilian grasslands, at the producer and consumer level, is at risk under the current rate of land‐use conversion, even at habitat losses below 50%. To avoid substantial biodiversity loss, conservation and more restrictive policies for conversion of native grasslands to different land uses in South Brazil are urgently needed.

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