Herbicide site preparation is common in longleaf pine artificial regeneration and restoration to reduce competition and promote seedling establishment. However, few studies have evaluated longer-term influences of herbicide site preparation on ecosystem development and fire management. We report results from a field study on Fort Benning, Georgia, initiated in 2003 to evaluate the response of longleaf pine seedlings, woody plant stem density, herbaceous vegetation cover, species richness, and fine fuels to two herbicide site preparation treatments: imazapyr/glyphosate and hexazinone. Both treatments clearly enhanced longleaf pine seedling growth compared with an untreated control, primarily by reducing hardwood stem densities. By 2009, hardwood stem density was 5 times as high on control plots compared with treated plots. Vegetation composition and structure were otherwise similar, with no differences in shrubs and woody vines, perennial bunch grasses, or species richness on treated versus control plots. Total herbaceous fuels were enhanced by hexazinone in particular, which bodes well for fire management and continued hardwood control. Alternatively, increased woody litter on control plots appeared to modify the fuel bed in ways that may inhibit fire management. Overall, results suggest that treated plots are better poised than control plots for restoration success without additional treatments beyond fire.
MethodsWe simulated eastern indigo snake movements under different resistance surface and resistant kernel parameterizations and selected the scenario that produced simulated movement distances that best approximated the maximum observed annual movement distance. We used our calibrated resistant kernel to model range-wide connectivity and compared delineated conservation units to Euclidean distancebased population units from the recent eastern indigo snake species status assessment (SSA). Results We identified a total of 255 eastern indigo snake conservation units, with numerous large (2500-5000 ha of suitable habitat) conservation units across the eastern indigo snake distribution. There was substantial variation in the degree of overlap with the SSA population units likely reflecting the spatial heterogeneity in habitat suitability and landscape resistance. Conclusion Our calibration approach is widely applicable to other systems for parameterizing biologically meaningful resistant kernels. Our conservation units can be used to prioritize future eastern indigo snake conservation efforts, identify areas where more survey work is needed, or identify small, isolated populations with high extinction risks.
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