Natural Canopy Damage and the Ecological Restoration of Fire-Indicative Groundcover Vegetation in an Oak-Pine Forest

An important goal of restoring fire to upland oak-dominated communities that have experienced fire exclusion is restoring groundcover plant species diversity and composition indicative of fire-maintained habitats. Several studies have shown that fire alone, however, may not be sufficient to accomplish this goal. Furthermore, treatment-driven declines in rare forest specialists could negate the benefits of ecological restoration in these ecosystems. I present the results of an experiment examining effects of tornado-generated canopy openings and biennial spring burning on groundcover vegetation at an oak-pine forest in north Mississippi, USA. Results from four years of monitoring showed that species richness and abundance of species indicative of fire-maintained open habitats were greater at sites with canopy damage than at sites with undamaged canopies, especially in years without drought. Annual ruderals increased initially following canopy damage but then decreased. Few forest indicator species changed in abundance, and the few that did increased. Canopy openings appeared to have a greater effect than fire on groundcover vegetation, although some legumes and panicgrasses appeared to benefit directly from fire. Results suggest that fire restoration treatments must include both canopy openings and fire to effectively increase the diversity and distinctiveness of groundcover vegetation in mixed oak-pine forests. Prescribed burning after years of fire exclusion, by itself, does not constitute effective restoration of fire (at least in the short term), but it also does not appear to reduce the abundance of rare, forest-specialist groundcover species.