Fire effects on plant communities in Ozark woodlands and glades

Abstract

Abstract Background Decades of fire suppression have caused drastic changes to community structure and composition across ecosystems, including in Ozark woodlands in the central Midwestern United States. Reintroducing fire can restore ground flora by reducing midstory tree density, increasing ground layer light, and reducing leaf litter accumulation, but we lack a clear understanding of how these effects vary across time and space. We investigated the effects of repeated prescribed fire on ground flora species richness, floristic quality, abundance, community composition, and stand structure over 20 years in a landscape matrix of glades, dry woodlands, and dry mesic woodlands using data collected from the Ozark National Scenic Riverways Fire Effects Monitoring program in the Current River Watershed in the Missouri Ozarks. Results We found that fire plays a key role in driving community structure and dynamics across community types, although with varying levels of intensity. Herbaceous species richness, abundance, and floristic quality index increased across all community types, while mean coefficient of conservatism decreased. Effects were stronger in drier sites. Community composition changed with successive burns, resulting in several indicator species for post burn treatments. The density of midstory trees declined across community types with repeated fire. The number of burns significantly affected overstory tree density overall, but overstory tree density only declined in dry woodlands and glades and not in dry mesic woodlands. Conclusions Our results suggest that landscape fire can shape plant community structure and dynamics. Specifically, these findings show that fire effects vary among community types, and suggest that land managers should consider landscape heterogeneity. Understanding repeated fire effects over several decades across multiple community types is critical to informing fire-driven woodland restoration across landscape scales.