Plant community response to burning and herbicide site preparation in eastern Louisiana, USA

High yield commercial forests are an important source of fiber for global forest product needs and the southeastern United States is a key region for global wood supply needs with intensively managed pine stands (Pinus spp.) an important component of forested landscapes in this region. Concern has arisen over possible effects of stand establishment practices on vegetation communities within commercial forests, particularly relative to use of herbicides and burning. Therefore, we examined response of plant communities to site preparation within intensively managed pine stands in eastern Louisiana, USA that were either prescribe burned (PF; n = 5) or treated with a combination of herbicides (imazapyr and triclopyr) and prescribe burned (PFH; n = 5) during 2002. We used 5 m line intercepts (n = 10 per stand) to quantify species richness, diversity, and relative abundance of plant species for 3 years post-treatment (2003–2005) with a repeated measures analysis of variance. We documented 80 genera or species of plants and neither species richness nor diversity differed between treatments. Site preparation with PFH appeared to promote development of an herbaceous plant community and reduced relative abundance of woody plants, whereas PF-treated sites were dominated by woody vegetation. Our results demonstrate that different plant communities result from PF and PFH site preparation and may place stands on different successional trajectories. We suggest PFH site preparation may increase availability of early successional vegetation associations on managed forest landscapes and may extend the time stands stay in this successional stage. However, increased crop tree growth from site preparation may shorten open canopy conditions.