Insular ecosystems of the southeastern United States: A regional synthesis to support biodiversity conservation in a changing climate

Abstract

In the southeastern United States, insular ecosystems—such as rock outcrops, depression wetlands, high-elevation\rbalds, flood-scoured riparian corridors, and insular prairies and barrens—occupy a small fraction of land area but\rconstitute an important source of regional and global biodiversity, including concentrations of rare and endemic plant\rtaxa. Maintenance of this biodiversity depends upon regimes of abiotic stress and disturbance, incorporating factors such\ras soil surface temperature, widely fluctuating hydrologic conditions, fires, flood scouring, and episodic droughts that may\rbe subject to alteration by climate change. Over several decades, numerous localized, site-level investigations have yielded\rimportant information about the floristics, physical environments, and ecological dynamics of these insular ecosystems;\rhowever, the literature from these investigations has generally remained fragmented. This report consists of literature\rsyntheses for eight categories of insular ecosystems of the southeastern United States, concerning (1) physical geography,\r(2) ecological determinants of community structures including vegetation dynamics and regimes of abiotic stress and\rdisturbance, (3) contributions to regional and global biodiversity, (4) historical and current anthropogenic threats and\rconservation approaches, and (5) key knowledge gaps relevant to conservation, particularly in terms of climate-change\reffects on biodiversity. This regional synthesis was undertaken to discern patterns across ecosystems, identify knowledge\rgaps, and lay the groundwork for future analyses of climate-change vulnerability. Findings from this synthesis indicate\rthat, despite their importance to regional and global biodiversity, insular ecosystems of the southeastern United States have\rbeen subjected to a variety of direct and indirect human alterations. In many cases, important questions remain concerning\rkey determinants of ecosystem function. In particular, few empirical investigations in these ecosystems have focused on\rpossible climate-change effects, despite the well-documented ecological effects of climate change at a global level. Long-term\rmanagement of these ecosystems could benefit from increased scientific effort to characterize and quantify the linkages\rbetween changing environmental conditions and the ecological processes that sustain biodiversity