Restoration and conservation management of the longleaf pine ecosystem: Understanding the pieces of the puzzle
Restoration of the fire-dependent, species rich longleaf pine-wiregrass (Pinus palustris-Aristida beyrichiana) ecosystem of the southeastern United States is a daunting task and requires knowledge of the complex relationships between stand structure, fuels, longleaf pine regeneration and mechanisms that maintain diversity. Based on the exceptionally high species richness and distribution across a wide ecological gradient, the ecosystem provides a unique opportunity to test prevailing ecological theories and to challenge forest management and restoration paradigms. Several studies conducted by Bob Mitchell and colleagues illustrate approaches to merging basic and applied research related to ecological restoration of the diverse native ground cover.
A long-term resource manipulation and fire exclusion study was conducted to examine relationships between productivity, disturbance and species richness. It was coupled with complementary short-term studies to determine the relative importance of recruitment limitations on seedling diversity. These studies were the first to suggest that the disturbance due to prescribed fire has a greater role in structuring biodiversity than does productivity, and that the episodic supply of microsites for recruitment could influence species richness in the highly threatened and biodiverse longleaf pine savanna. Another study examining stand structure and patterns of ground cover recovery during the conversion of planted slash pine stands to multi-age longleaf pine indicated that local seed dispersal appears to be an important factor structuring species richness patterns. Limitations of seed dispersal distance in some species, particularly those that are ant- or gravity-dispersed, represent an obstacle to passive restoration that can only be overcome either by introduction of propagules in the restoration process or by allowing for longer periods of recruitment. Other case studies from silvicultural restoration and applied conservation management in second-growth stands provide insights for developing conservation models for longleaf pine ecosystems and have been used to identify important conservation and forest management principles.