Fire-dependent, longleaf pine forests are a major conservation priority in the southeastern United States due to their dramatic decrease in extent and their many unique species. Recurrent fires are necessary for their long term persistence, and low-intensity ground fires are now regularly used to manage these threatened ecosystems. Although prescription fires are widely viewed as beneficial by managers and policy makers, their effects are largely only known for a few priority taxa. We are investigating the effects of controlled burns on the functionally important, native bee communities of upland, longleaf pine woodlands. We have been systematically sampling bee communities at recently burned versus 1- and 2- year post burn sites using blue-yellow cross vane traps. Our objective is to quantify short-term effects of controlled burns, as fire return intervals of 1-3 years are now routine in the management and restoration of longleaf pine woodlands. Our initial sampling conducted during 2016 and 2017, morphed into a more extensive survey that initiated June 2019 and continues. Traps are set at bi-weekly intervals and remain in the field for one week before collections are retrieved. To quantify the effects of recent fire on bee communities, the resulting species (rows) by site (columns) abundance matrix is being analyzed using a combination of multivariate methods implemented in Primer and iNext.
Results/Conclusions
To date more than 2400 bees have been collected, representing more than 50 species. Although data collection is ongoing, we have found no clear effect of fire on species composition, richness, or community structure. Overall, bee communities from recently burned sites are no different than those from sites that have remained unburned for a year or more. Rarefied species accumulation curves for all sites have overlapping confidence intervals when extrapolated to the size of larger overall samples. Bray-Curtis pairwise similarities among sites are also similar, regardless of the site’s burn history, and there is no significant clustering of communities in multidimensional space. In fact, some of the most similar communities are those from sites with the most divergent burn intervals. This lack of a clear effect of burn history on community diversity suggests that native bee communities are generally resilient to low intensity prescribed burns. Most species apparently either readily colonize from elsewhere or find protection in situ above-ground in unburned vegetation, twigs, and forest duff, or below-ground in nests.