Fire-maintained pine savannas and woodlands dominated the Southeastern Coastal Plain prior to European settlement and provided habitat for many of the endemic species that led to the designation of the region as a global biodiversity hotspot. Old-growth concepts for pine savannas and woodlands of the southeastern US are based on sites with minimally-disturbed populations of old trees and ground-layer vegetation, and long-term fire regimes that replicate ecological and evolutionary conditions present historically. Highly uneven-aged old-growth pine populations persist over time as stands containing dense patches of recruits interspersed among more randomly dispersed large trees. Stands are maintained in demographic non-equilibria by recurring tropical cyclones and lightning strikes, and are blocked from transition to closed-canopy forests by frequent fires that also maintain conditions conducive for recruitment of pines. Old-growth ground-layer vegetation includes grasses as aspect dominants, as well as a high diversity of shrubs, lianas, and especially forbs, many endemic to pine savannas and most of which thrive under conditions of frequent, lightning-season fires and which respond post-fire with rapid regrowth and flowering. Other taxonomic groups ranging from insects to soil microbes are known to be extremely diverse in the region, but their place in this ecosystem remains relatively unstudied.
Results/Conclusions
Pines and some ground-layer savanna plants generate feedbacks on fuels, altering characteristics of fires. The resulting plant-fire “coevolution” involves iterative changes in characteristics of plants and fires, producing plant communities that are highly integrated with respect to recurrent fire and similar in function to savannas worldwide that occur on impoverished soils in relatively constant climates. In the current period of increasingly small fragments of natural landscape, human exploitation, and global change, maintenance of high-biodiversity, fiery ecosystems with old-growth attributes will require active management using prescribed fires that mimic the natural, lightning-season fires and ecological conditions under which the savanna species evolved. Restoration of old-growth characteristics requires reestablishing ground-layer vegetation that is both diverse and that facilitates fires, recreating uneven-aged pine populations that produce flammable needle fuels, and reinstating fire-vegetation feedbacks that mimic natural fires with respect to return periods and season. Relatively large tracts will be necessary to allow a patchwork of fire histories and facilitate the ability of managers to employ fire on a regular basis. In addition, it will be important to incorporate other natural ecosystems of the Coastal Plain into preserves to allow preservation of regional biodiversity and the landscape-level natural processes to which these habitats contribute.