Southeastern ecosystems and early successional habitat: One size does not fit all

Background/Question/Methods

Natural disturbances and early successional habitats (ESH) are integral to most ecosystems, and important in maintaining diverse biotic communities.  ESH can differ widely, but share in common a well developed ground cover or shrub and young tree component, lack a closed tree canopy, and are created or maintained by recurring disturbances.  Eastern ecosystems are as diverse as the geography, topography, and disturbance regimes that shape them.  Contrasting examples include longleaf pine-wiregrass sandhills or sand pine scrub in the Coastal Plain, and upland hardwood forest in the southern Appalachians.  We compare natural disturbance types, frequencies, and scale across several southeastern ecosystems, and consequent structural characteristics that may be categorized as ESH, or not.  We assess the ‘disturbance dependence’ of characteristic flora and fauna, as potential clues to historic disturbances and habitat structure integral to the ecosystems in which they evolved.  Finally, we discuss potential management strategies that mimic natural disturbances, or otherwise create ESH compatible with specific ecosystems and other land management objectives.

Results/Conclusions

Natural disturbances differ among southeastern ecosystems, and create widely different structural characteristics that nonetheless share the “openness” of ESH.  Longleaf pine-wiregrass sandhills or sand pine scrub in the Coastal Plain, or table mountain-pitch pine in the southern Appalachians, are created, maintained, and defined by fire, albeit fires of widely differing intensities, frequencies, and scope.  Gopher tortoises, red cockaded woodpeckers, and many endemic herbaceous plants occur solely or primarily in this environment, providing evidence that the open understory and high-light environment they require was maintained by frequent, low-intensity fire caused by relatively frequent lightning strikes.  The open, low-vegetation structure required by scrub endemic scrub jays, sand skinks, and plants indicate that fires in sand pine scrub were stand-replacing and largescale. Serotinous cones and bare-ground seedbed requirements of endemic table mountain pine suggest that it evolved with frequent fire, likely most common on xeric ridgetops in the southern Appalachians. In the central hardwood region, lightning strikes are relatively infrequent, and natural disturbances that create ESH are primarily due to winds associated with hurricane remnants, tornadoes, or severe ice storms.  Several bird, reptile, and plant species opportunistically use ESH of varying patch size, but few are endemic, suggesting that historically, availability of ESH was spatially and temporally unpredictable.  Management tools including fire, herbicide, and different silvicultural methods can create ESH with size and structural attributes characteristic of each ecosystem.