Fire history and tree invasion in an Ozark glade, barrens, and woodland complex

Abstract Background In the Ozark Plateau, glade and barrens communities provide habitat and species diversity within the broader landscape of hardwood forests and oak-pine woodlands. In the past, frequent surface fires burned through the extensive oak-pine woodlands of the region, and it is likely that these fires burned into adjacent barrens and glades, helping keep them clear of woody vegetation. Following fire protection in the twentieth century, many of these barrens and glades have been invaded by shrubs and trees. However, we generally lack empirical evidence of the role that fire played in maintaining these open habitats historically. Therefore, we aimed to assess the role of past fire in shaping vegetation at Devil’s Knob-Devil’s Backbone Natural Area, an area that includes invaded glade and barrens communities surrounded by oak-pine woodlands and forest. Our objectives were to (1) characterize the past fire regime at the site; (2) assess whether the timing of tree invasion aligns with the timing of fire protection at the site; and (3) assess the drivers of spatial and temporal patterns of tree invasion within the glades and barrens. Results We collected fire-scarred shortleaf pine samples from the wooded slopes surrounding the glades and barrens and we collected cores from trees within the barrens and glades. The reconstructed fire scar record spanned the period 1670–2018, with a composite mean fire interval of 2.6 years prior to the onset of fire protection in the 1930s. Tree establishment dates from within the glades and barrens demonstrated that large pulses of tree recruitment aligned with the onset of fire protection, indicating that fire was an important ecological process that maintained open habitat in the glade and barrens communities. Analysis of tree age and corresponding environmental site conditions within the glades and barrens indicated that the majority of red cedar ( Juniperus virginiana ) establishment occurred later in the 1960s on topographic positions with higher amounts of insolation. Conclusion Our results support the view that frequent fire played an important role in maintaining these glades and barrens in the past and that prescribed burning can be used to restore and maintain these habitats in the future.