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Determinants of plant functional group richness in fire-maintained pine savannas

The fragmented nature of longleaf pine savanna ecosystems means that they are effectively islanded within a larger matrix of agriculture, plantation forestry, fire-impeding hardwood forest, wetlands, water bodies, and urban development, wherein only a small proportion of native savanna species are found.  Each savanna fragment has a unique plant species composition due to a variety of historical and environmental factors, and the differences between those species assemblages may have implications for wildlife food provisioning, ecosystem resilience, and biodiversity conservation.  Little is known about the lasting effects of past fire suppression and landscape fragment isolation on the plant species composition of today’s savanna preserves, or the influences of long-term differences in prescribed fire regime characteristics (particularly seasonality and frequency) on plant communities.    

We are examining plant species richness and diversity patterns within plant functional groups important to wildlife (warm-season grasses, cool-season grasses, legumes, forbs, shrubs, and trees) across a regional sample of 30 different fire-managed savanna preserves in Florida and Georgia, USA.  We hypothesize that functional group richness and composition will vary between sites, and that some of this variation will be explained by fire regime (return interval, number of fires, time-since-fire, and seasonality), vegetation structure (herbaceous cover, woody cover, and tree density) and spatial factors (composition of the surrounding landscape and distance between sites).  The results of this study will provide a new perspective on the role of prescribed fire in preserving biodiversity across Florida’s large network of fire-maintained savanna preserves.