Rangeland resilience to droughts: changes across an intensification gradient

Abstract

AimThe intensification of livestock systems generates structural and functional changes in native grassland, which alter their capacity to respond to disturbances. Our objective was to evaluate the resilience to an extraordinary consecutive droughts event, across an intensification gradient of livestock systems. Our prediction was that sites with more intensive management (less diverse) will have lower resilience (as resistance and/or recovery) to drought.LocationSouth-central region of Uruguay.MethodsWe evaluated the resilience (as resistance and recovery) to consecutive droughts, across an intensification gradient of livestock systems. We analyzed the effect of diversity on resilience at two scales: 1. regional, an observational experiment with real commercial farms, where we compared three systems with an increasing level of intensification that determine changes in diversity, 2. patch, we carried out a manipulative experiment with different grazing management intensities determined by the level of biomass removal and fertilization. In both experiments, resistance and recovery were calculated from the Normalized Difference Vegetation Index.ResultsThe most intensified and less diverse management (sown pastures) had significantly lower resistance than native and overseeded grassland. Also, it showed the lowest recovery rate, and its productivity did not reach previous values after the drought end. The grazing intensification gradient at the plot scale did not show clear differences among treatments neither for resistance nor recovery. However, resistance of the individual plots showed a positive significant association not only with species richness and diversity, but also with evenness and diversity of functional groups.ConclusionOur research supports the insurance hypothesis by demonstrating that farms with greater biodiversity (less intensive management) have higher resistance to drought. We found that species richness is not enough to account for the effect of diversity on resilience. Our results emphasize the importance of preserving grassland biodiversity to maintain resilient ecosystems in the face of climate change.