Effects of Oak-hickory Woodland Restoration Treatments on Native Groundcover Vegetation and the Invasive Grass, Microstegium vimineum

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 open habitats. Treatment-driven declines in rare forest specialists and increases in widespread ruderals and competitive non-native species, however, could negate the benefits of ecological restoration in these ecosystems. We tested the effects of treatment-related disturbances on native groundcover vegetation, density and proliferation of patches of an invasive grass, Japanese stiltgrass (Microstegium vimineum), and the net effects of treatment and the invasive grass on native groundcover vegetation. Results from multiple years of monitoring at two replicate sites in north Mississippi showed that thinning and burning significantly increased both groundcover species richness and the abundance of species indicative of fire-maintained open habitats. We found subtle increases in forest species in response to treatments, whereas most native ruderals did not increase significantly in response to the treatments over the long term. The density and competitive effect of the invasive Japanese stiltgrass increased dramatically at both sites in response to the restoration treatments. However, new patches of Japanese stiltgrass established in response to the treatments only at the site with the more recent history of agricultural disturbance. Results suggest that fire restoration treatments were effective in the absence of past agricultural disturbance and in areas lacking Japanese stiltgrass. At sites with a history of agriculture and large populations of Japanese stiltgrass, effective restoration may require eradication of Japanese stiltgrass and reintroduction or augmentation of competitive, native specialists of fire-maintained open habitats.