PARENT SESSION
Symposium 8: Old-Growth Savannas as Models for Management of Upland Coastal Systems: The Role of Disturbance in a Time of Global Change
Organized by: F Gilliam and W Platt
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Chatham Ballroom B.
Restoring fire to long-unburned old-growth southeastern pine savannas: new approaches for novel forests.
Varner, J.*,1, Putz, Francis1, Gordon, Doria1, 2, Hiers, J. 3, Mitchell, Robert 4, Ottmar, Roger5, 1 University of Florida, Gainesville, FL, USA2 The Nature Conservancy, Gainesville, FL, USA3 Eglin Air Force Base, Niceville, FL, USA4 Joseph W. Jones Ecological Research Center, Newton, GA, USA5 USDA Forest Service Pacific NW Research Station - FERA, Seattle, WA, USA
ABSTRACT- Traditional models of southeastern coastal plain pine savannas are based on pristine ecosystems now rare in the contemporary landscape. Instead of open pine savannas with high groundcover richness frequented by low-severity surface fires, greater than half of all remnants are degraded and fire-excluded. To fill the gap between these understandings, we reviewed the literature and investigated natural experiments of fire exclusion in southeastern longleaf pine (Pinus palustris) savannas. Our primary interests were the influence fire exclusion has had on vegetation structure and composition, its role in the advent of forest floor accumulations, and outcomes of fire re-introduction. Fire excluded pinelands have shifted structurally from nearly mono-specific open savanna-woodlands to closed canopy mixed pine-hardwood forests. Both overstory and understory species composition has changed; canopies are more diverse, groundcovers more depauperate. Without frequent surface fires, forest floor accumulations have developed deep (5-50 cm), densely rooted decomposition horizons (Oe and Oa) absent in frequently-burned stands. In fire re-introductions, resulting overstory pine mortality has been substantial (from 10 to 100% of larger individuals), a major deterrent to further restoration. We review four primary hypotheses related to pine death resulting from fire re-introduction: (1) smoldering Oe and Oa horizons damage vascular tissues, (2) smoldering Oe and Oa horizons damage organic and surficial mineral soil roots, (3) associated flaming combustion damages canopy meristems, and (4) fire-caused damage and stresses lead to whole-tree carbohydrate deficits. Restoration of long-unburned pineland ecosystems will require more understanding of vegetation dynamics, pine physiological response, and smoldering fire ecology; all research areas that have received little attention considering the extent and importance of this novel forest.
Key words: forest floor , smoldering combustion, fire exclusion, pinus palustris