Concepts for maintaining a high-endemism fiery refugium in the context of a changing climate: Managing for evolutionary plant-fire feedbacks should facilitate conservation of endemic species in pine savannas

Background/Question/Methods

To persist during climate change, high endemism refugia should maintain ecological conditions to which native species are adapted. We explore conservation of such ecological conditions in geologically old, climatically stable refugia using the North American Coastal Plain (NACP) as an exemplary hotspot in which environmental conditions have been relatively stable over millions of years. Proximity to oceans in a warm and humid temperate-subtropical seasonal climate has resulted in thunderstorms and lightning strikes during a “fire season” in which weather conditions reliably facilitate frequent low-severity landscape-scale fires. The evolutionary consequence, comprising about 1/3 of the NACP, is fiery pine savannas and associated inclusions characterized by endemic pyrogenic vegetation (C₄grasses, flammable shrubs and palms, and savanna pines) and high endemic plant species richness (1552 endemic plant species; 85% of all NACP endemics). In the context of 96% habitat loss and conversion largely resulting from severe fire suppression, we describe how pine savanna endemics in the East Gulf Coastal Plain are distributed with respect to hydrological and soil conditions that change along microtopographic gradients, often a few meters or less. We further examine relationships between expected changes in temperature, moisture and fires to explore expected climate change effects on pine savanna endemics.

 Results/Conclusions

NACP endemics comprise ~40-50% of local pine savanna floras and combine deep and more recent endemism. A small group of overstory and ground layer species produce flammable fine fuels and tend to be widely distributed along local microtopographic gradients across subregions. A larger group of highly diverse ground layer endemics contains species that are much more narrowly distributed from xeric to hydric conditions, often associated with distinct aspects of soils, and differ among subregions. We anticipate that restricted distributions relative to local environmental conditions should be influenced only weakly by changes in temperature and rainfall, especially in coastal savannas; adaptations, such as underground storage organs (USOs) that facilitate occupancy of fiery pine savannas, should confer resistance of many species to climate change. Thus, landscape-level diversity of endemics is not likely to change greatly in response to anticipated climate change. Endemic diversity should be more dependent on characteristics of fire regimes. Current management actions based largely on outmoded succession concepts, rather than vegetation-fire feedbacks that facilitate fires resembling those under which endemic species evolved, are degrading biodiversity. Fire management based in local vegetation-fire feedbacks should facilitate effective conservation of endemism in the context of ongoing climate change in the NACP hotspot.