Roles of fire in the plant communities of the eastern Edwards Plateau of Texas

Abstract

Background The eastern Edwards Plateau supports a mosaic of woodlands, savannas, and shrubland in which native plant and animal species are often still dominant. Some woodlands are dominated by a mix of native woody species, including Ashe juniper (Juniperus ashei), oak species (Quercus spp.), and other hardwoods. Other woodlands are nearly pure Ashe juniper; these are particularly susceptible to crown fires. The savannas were once, and still can be, maintained by surface fires. Results We hypothesize that frequent surface fires once kept some of the mixed woodlands more open and more diverse (a “lost community”) and that these fires would have reduced the abundance of Ashe juniper, which does not resprout from the base, and allowed oak regeneration, which is currently failing. The absence of fire, the current failure of oak regeneration, and high white-tailed deer densities together favor the “juniperization” of woodlands, that is, the conversion of mixed woodlands into nearly pure stands of Ashe juniper. Surface fires in savannas can sometimes control woody encroachment and the non-native grass King Ranch bluestem (Bothriochloa ischaemum), although the particular fire characteristics required are not yet clear. The current lack of fire in savannas favors their conversion to woodlands. Since under present conditions Ashe juniper is the primary encroacher, without fire or mechanical clearing these savannas are also on trajectories towards nearly pure stands of Ashe juniper. Conclusions Prescribed fire, sometimes paired with mechanical thinning, offers land managers in this region a tool for achieving many goals, including increasing native biodiversity and reducing wildfire danger. However, more study of the effects of fires of different intensities and frequencies in these woodlands, savannas, and shrublands is needed to better inform the use of prescribed fire in this region.