Functional diversity loss with increasing livestock grazing intensity in drylands: the mechanisms and their consequences depend on the taxa

1. Overgrazing is one of the main drivers of desertification in drylands, and livestock production is expected to increase in the next decades. The analysis of functional diversity can clarify the effects of increasing livestock grazing on ecosystem functioning.

2. We assess the effect of livestock grazing intensity on the relationship between taxonomic (TDH) and functional diversity (FDQ) of plants, ants and small mammals, as well as on within-trait diversity. We compared results using two indices of taxonomic diversity (Shannon and Simpson). We used structural equation modelling (SEM) to assess the causal relationship between grazing intensity, TDH, FDQ and decomposition rate for each taxa.

3. Correlation between TDH vs. FDQ varied across assemblages and seasons, but was consistent between different indices of taxonomic diversity. A similar trajectory of TDH vs. FDQ under land-use intensification was found for all taxa, with a correlated loss of species and functional traits. Al...