Disturbance-Adapted Animals: Habitat Requirements and Historic Distribution Across Central Hardwood Forests
Wildlife species are often categorized based upon their associations with vegetation structure and/or composition; those associated primarily with young, open, recently disturbed forest are often described as disturbance-adapted. Some species are disturbance specialists, where most of their requirements are met within recently disturbed forests; many others use both young and mature forests. Disturbance-adapted species may differ in their associations with specific structural features across the gradient of conditions created by disturbances. For example, Indiana bats rely on clumps of snags across the landscape and often roost in gaps or on forest edges; breeding eastern bluebirds require large, open areas to forage, and snags for nesting; indigo buntings are associated with open canopy forest having herbaceous and shrub components; and golden-winged warblers require open, grassy areas with some shrub and sapling cover in a forested matrix. Historically, this gradient of forest conditions was likely created by natural disturbances such as single-tree mortality, ice storms, insect outbreaks, high winds, and wildfires of different severities and frequencies, and by anthropogenic burning or clearing associated with Native Americans and later European settlers. We explore a suite of wildlife species that utilize different disturbed-forest structures and patch sizes, and discuss how their historic distributions and populations may have ebbed and flowed with frequency and size of natural and anthropogenic disturbances across the landscape. Finally, we investigate potential strategies that can be used to achieve the conservation of disturbance-associated wildlife while protecting biodiversity as a whole in central hardwood forests.
1 North Carolina Wildlife Resources Commission, Mills River, NC; 2 USDA Forest Service, Southern Research Station, Asheville NC; 3 USDA Forest Service, Southern Research Station, Clemson University, Clemson, SC; 4 North Carolina Wildlife Resources Commission, Marion, NC
89 • Scott E. Schlarbaum1, Faith T. Campbell2, Stacy L. Clark3
Changes in Forest Structure by Exotic Pests: Challenges in Policy, Biology, and Forest-Related Infrastructure
Forest ecosystem function and structure in the United States are being disturbed by a plethora of long-term and short-term impacts such as climate change and fragmentation due to urban development. Among the more immediate threats to the historic integrity of forests, is the progressive decimation of forest tree species by exotic pests. Over the last two centuries, these pests have transformed native forest species composition and structure. Some species, such as the American chestnut, are facing multiple exotic pests that reduce the probability of successful restoration. Preventing pest entry through strengthening of policies regarding importation and movement of goods within the country, developing sustained support for research to address each pest problem and restore affected species, and rebuilding the associated research and development infrastructure are discussed.
1 UT Tree Improvement Program, Dept of Forestry, Wildlife & Fisheries, The University of Tennessee, Knoxville, TN; 2 The Nature Conservancy, Arlington, VA; 3 USDA Forest Service, Southern Research Station, The University of Tennessee, Knoxville, Dept of Forestry, Wildlife, and Fisheries, Knoxville, TN
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90 • Virginia Dale1, Dan Hayes1, M. Joseph Hughes2
Potential Effects of Climate Change on Natural Disturbances in the Southeastern Upland Hardwood Forest Region
The spatial patterns and ecological processes of the southeastern upland hardwood forests are a function of climate and disturbance regimes. Global Circulation Models project an increase in temperature for all months in the southeastern United States, but changes in precipitation are less consistent (with some models projecting less precipitation and others projecting more). Even more unclear is how climate change might affect future trends in the severity and frequency of natural disturbances, such as severe storms, fires, droughts, floods, and insect outbreaks. Here, we use the Landsat record to map the spatial pattern and severity of broad classes of natural disturbances over the southeast region. The data derived from this map allow analysis of regional-scale trends in natural disturbances in the region over the last three decades. We discuss how observed changes in those disturbance regimes might project into the future, and the associated impacts on the patterns and processes in southeast upland hardwood forests.
1 Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN; 2 Dept of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN
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91 • Eric K. Zenner
Managing Central Hardwood Forests Within the Historic Range of Variation in Natural Disturbances
Forest ecosystems are dynamic; autogenic processes such as regeneration, growth, mortality, and decay keep forest composition and structure in a continuous state of change that is further modified by allogenic (natural and anthropocentric) disturbances. Disturbance regimes represent the interaction of frequent small scale events with infrequent, large scale events and are conditioned by landscape heterogeneity and feedbacks linked to current vegetation and prior disturbances. The complexity of natural disturbances is the crossroad to multiple pathways of forest succession, and facilitates long-term maintenance of ecosystem structure and processes. Historic range of variation (HRV) in natural disturbances attempts to synthesize the systemic variation in extent, magnitude, severity, frequency, timing, synergisms and feedbacks into a conceptual framework. Because disturbance regimes are tied to ecosystems, landscapes, and regions, they are not random, unpredictable or equally likely everywhere. Linking HRV to spatially delineated areas identified by climate, geology, topography, soils, and vegetation through an ecological classification system provides an ecological framework, within which silviculturists could then devise management strategies. Recognizing that not all disturbances provide the desired benefits and management outcomes, silvicultural strategies can be additive, compensatory or preventive vis-à-vis the HRV. Although the HRV concept has been challenged because HRV conditions may no longer exist due to climate change, atmospheric chemistry changes, and introduced species that are poised to transform all ecosystems, local analyses of HRV are critical to document the plasticity of forest community persistence under changing environmental conditions and provide guidance for silvicultural prescriptions.
Dept of Ecosystem Science and Management; Penn State University, University Park, PA
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92 • Mason Brock1, Dwayne Estes2
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