Influence of Herbicide Site Preparation on Longleaf Pine Ecosystem Development and Fire Management

Abstract

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.