Disentangling ecosystem responses to livestock grazing in drylands.

This study aims to analyze dryland dynamics under livestock production in an integrated manner, by considering several taxa, intrinsic variability in resource availability and variations in disturbance intensity and management. Resilience was assessed by quantifying functional redundancy and response diversity of vegetation, ants and small mammals in arid rangelands under continuous and rotational management strategies. The net effect of increasing grazing intensity on community resilience and the occurrence of structural (richness, diversity and composition) and functional (decomposition rate) threshold responses under the effects of seasonality and management were assessed. Results showed that grazing intensity negatively affected functional redundancy more than response diversity of all taxa and under both management strategies. Animal assemblages showed abrupt changes in richness and diversity, but vegetation showed a gradual change in structure along the grazing intensity gradient. Decomposition rate showed abrupt changes under both management strategies. Although overall community resilience decreased, not all assemblages presented a threshold response, probably due to different components of resilience affecting assemblages in different ways. These decreases caused structural threshold response within animal taxa but not on vegetation. The lack of thresholds in vegetation does not imply that a related ecosystem process is not affected (i.e., decomposition). Vegetation and animal assemblages, as well as functional and structural threshold responses, may not be strongly coupled in natural systems. [ABSTRACT FROM AUTHOR]