Using LiDAR to Analyze Vegetation Structure and Ecological Depature in the Upper Warwoman Watershed, Georgia
This report was conducted for the Southern Blue Ridge FLN by Josh Kelly Abstract (Western North Carolina Alliance).
Abstract: Ecological restoration has become one of the guiding principles of National Forest management. However, it can be difficult to identify a reference or desired condition as a restoration goal, and furthermore, accurately assessing ecosystem condition is dependent of the quality of the data available. LANDFIRE Biophysical Settings are computer models that combine scientific research, historical information, and expert opinion to describe the disturbance probabilities of ecosystems and simulate a natural range of variation as a restoration target. Ecological zone maps are the most accurate ecosystem maps available for the Southern Blue Ridge Ecoregion and can be cross-walked to LANDFIRE Biophysical Settings. Light Detection and Ranging (LiDAR) data are recognized as one of the most comprehensive and accurate data sources, where available, for measuring vegetation structure. The current condition of the upper Warwoman Watershed in Rabun County, Georgia was analyzed with the use of ecological zone maps, LANDFIRE Biophysical Settings, and LiDAR vegetation models. In total, 4,900 hectares of Chatahoochee National Forest were evaluated using LiDAR measured height and US Forest Service stand records to estimate forest age. LiDAR measurements of canopy cover and shrub density were used to evaluate canopy closure. Of seven forest ecosystems evaluated, five were found to be highly departed from reference conditions. Age and canopy closure were compared with NRV conditions predicted by the biophysical settings model to determine the level of departure with each ecozone. In general, ecosystems with a more frequent historical fire return interval were more departed from reference conditions than mesic ecosystems. All ecosystems had less young forest than predicted by Biophysical Setting models, demonstrating a very low rate of disturbance. All oak and pine ecosystems had canopies that were much more closed than the reference models, with canopy openings and young forest concentrated in prescribed fire areas. This study indicates that continued fire management and other techniques that create and maintain early-seral and open-canopy forest along with the continued restoration of old-growth conditions on public land in the Warwoman Watershed would be ecologically beneficial.
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