The 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 pastoral systems. Our prediction is 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 pastoral systems. We analyzed the effect of diversity on resilience at two scales: 1. regional, where we compared the resilience of 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 systems (different level of defoliation, and fertilization). In both experiments the response variables, resistance and recovery, were calculated from the Normalized Difference Vegetation Index, a remotely sensed proxy of aerial net primary productivity. ResultsOur results showed that sown pastures (the less diverse) had significantly lower resistance, than native grassland and overseed grassland. Also, sown pastures showed the lowest recovery rate, although differences were only significant with overseed grassland. Grazing treatments at the plot level (manipulative experiment) did not show clear differences among treatments neither for resistance nor recovery. However, resistance of the individual plots showed a positive significant association with evenness and diversity of functional groups. ConclusionThis study showed that the different grazing managements studied were resilient, in terms of their ANPP, to a major drought disturbance event. Differences in resilience was expressed in resistance rather than recovery. These results support our prediction, both at the regional and plot scales, that the least rich and diverse situations showed the lowest resilience, at least in terms of resistance.

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 pastoral systems. Our prediction is that sites with more intensive management (less diverse) will have lower resilience (as resistance and/or recovery) to drought.Location: South-central region of Uruguay. MethodsWe evaluated the resilience (as resistance and recovery) to consecutive droughts, across an intensification gradient of pastoral systems. We analyzed the effect of diversity on resilience at two scales: 1. regional, where we compared the resilience of 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 systems (different level of defoliation, and fertilization). In both experiments the response variables, resistance and recovery, were calculated from the Normalized Difference Vegetation Index, a remotely sensed proxy of aerial net primary productivity. ResultsOur results showed that sown pastures (the less diverse) had significantly lower resistance, than native grassland and overseed grassland. Also, sown pastures showed the lowest recovery rate, although differences were only significant with overseed grassland. Grazing treatments at the plot level (manipulative experiment) did not show clear differences among treatments neither for resistance nor recovery. However, resistance of the individual plots showed a positive significant association with evenness and diversity of functional groups. ConclusionThis study showed that the different grazing managements studied were resilient, in terms of their ANPP, to a major drought disturbance event. Differences in resilience was expressed in resistance rather than recovery. These results support our prediction, both at the regional and plot scales, that the least rich and diverse situations showed the lowest resilience, at least in terms of resistance.

The replacement of grassy vegetation by tree monocultures has become an emerging global activity. In South America, about half a million hectares of new plantations are incorporated each year, typically conducted with fast‐growing exotic species, like Pinus and Eucalyptus species. However, information about the potential for spontaneous recovery of these grasslands is almost nonexistent. We assessed the biotic and abiotic legacies left by a 7‐year plantation of Pinus taeda on a natural temperate sub‐humid grassland of Uruguay. In a paired sampling design, comparing a clear‐cut P. taeda plantation and a natural grassland, we analyzed the vegetation richness, cover and composition, the seed bank size and composition, and chemical soil parameters. Afforestation reduced species richness and vegetation cover by 30 and 58%, respectively. Also, species composition differed considerably between sites. Afforestation had a strong negative effect on grass species, excluding the shade‐intolerant C4 grasses that dominate in the grassland. Seed‐bank richness did not differ between sites, but the total seedling density was significantly higher in the plantation compared to the grassland (6,620 and 4,420 seeds/m2, respectively), mainly due to the contribution of forbs. Only 30% of the seed bank species were shared between the two sites. In terms of soil chemical parameters, afforestation induced soil acidification (deviation by 0.15–0.20 pH units) and reduction in soil carbon and cation (Ca and K) concentrations (deviation by 30, 20, and 40%, respectively). Our study showed limited possibilities for passive restoration of a natural grassland of Uruguay after a Pinus afforestation event.