Predicting global climate change impacts on longleaf pine (Pinus palustris) distribution
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Before its decline in the wake of agricultural conversion, timber harvesting, the naval stores production industry, and fire suppression, longleaf pine (Pinus palustris) stands were a prominent feature of the natural ecosystem of the southeastern U.S. In light of this, longleaf pine has become a strong candidate species for restoration projects. However, previous studies have mainly focused on restoration within the historic range of the longleaf pine ecosystem. To evaluate persistence of longleaf pine into the future, this study focused on the potential impacts of climate change on longleaf pine distribution. In order to help longleaf pine restoration projects to be successful, it is critical to estimate the potential change in suitable sites for longleaf pine over the course of the next century. In order to model potential suitable site for longleaf pine, two approaches were compared: the Maximum Entropy approach (MaxEnt) and the Random Forests (RF) approach. Changes in suitable habitat were evaluated for three time points (2020, 2050, and 2080) using two general circulation models (Canadian Center for Climate Modeling and Analysis Coupled Model Version 3 (CGCM3) and the Hadley Center Coupled Model Version 3 (HadCM3)) with two emission scenarios (medium to high emissions and low to medium emissions) and two thresholds for determining the range considered "suitable" given model output (relatively liberal and strict). Thus, each approach has eight scenarios, for a total of 16 scenarios in this study. Most of the scenarios estimated that habitats suitable to longleaf pine will decrease by 2080, and that the maximum latitude of the area designated as suitable habitat would move farther north than that of current longleaf pine distribution. Each model produced different predictions and, while the degree of difference was significant in terms of the size of suitable habitat, the difference was slight for northward shift. General circulation models and emission scenarios did not result in large differences between the 16 model predictions regarding the size of the future suitable habitat and the location of suitable habitat. However, the approach (MaxEnt or Random Forests) and thresholds (the value for determining suitable and unsuitable habitat) produced significant differences among the various model predictions.