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The conservation of disturbance-prone ecosystems such as rangelands may depend on the spatial and temporal variation in the application of disturbances. Patch-burn management approaches attempt to increase overall landscape biodiversity by creating a mosaic of habitat patches using a patchy application of fire and grazing. Three fundamental assumptions underlay the patch-burn management approach: 1) fire and grazing drive spatial patch differentiation in community structure, 2) species composition of patches diverge through time in response to disturbance, 3) high spatio-temporal variation in fire and grazing results in high compositional variation and thus high landscape-scale diversity. We tested the first two assumptions of the patch-burn approach by comparing the importance of variation in management (changes in fire frequency and grazer species) relative to inherent sources of landscape heterogeneity at the Tallgrass Prairie Preserve in Osage Co., Oklahoma, USA. We sampled 150 square 100 m2 quadrats on a 1 x 1 km UTM grid. We randomly selected 20 of those quadrats to annually resample for 12-years. We recorded visual cover of all vascular plant species rooted within each quadrat. We used variation partitioning within multiple regression and direct ordination frameworks to estimate the relative contribution of classes of variables on species richness and composition respectively.
Our results indicate that there was some support for the two assumptions underlying patch-burn management; however, independent spatial and temporal inherent landscape heterogeneity played a much larger role than management in shaping both plant richness and composition. The strength of inherent landscape heterogeneity on the plant community suggests that fine-tuning the application of fire and grazing is not critical for maintaining this community as long as fire and grazing remain part of the system. More generally, the effects of intrinsic spatiotemporal template on biodiversity may dominate even in disturbance-prone ecosystems.