COS 58-5
The effects of different prescribed burning strategies on functional trait diversity in longleaf pine understory communities
Prescribed burning is the primary tool available to land managers for maintaining healthy Longleaf Pine savanna that is home to many threatened and endangered species, but burning is expensive and comes at the cost of limiting multiple land-uses and affecting compliance with environmental regulations. Changes to prescribed burn frequency may affect plant communities in many ways, such as by altering fire intensity by changing the amount of fuel that accumulates between burns, or by altering nutrient cycling. Thus, different fire frequencies impose different environmental filters on the functional diversity of these systems, which has consequences for community structure and function. Sound management decisions require an understanding of these consequences. To understand the effect of fire frequency on functional trait diversity in the understory of the Longleaf Pine ecosystem of North Carolina’s Sandhills region, we set up 142 vegetation plots at 32 sites on the Fort Bragg Military Reservation and imposed fire treatments so that each site was burned on a 1, 2, or 3 year interval, or suppressed completely. In each plot we measured a suite of functional traits related to nutrient acquisition/retention and fire tolerance/promotion on over 100 plant species, along with relevant environmental variables.
Results/Conclusions
We show that, while there is large variation in individual species' responses to fire and climate variables, community functional traits show significant directional shifts in response to the time since the most recent burn, but are less responsive to the cumulative number of burn events over the previous 3 three years. Temperature driven water stress during the growing season, measured in stress degree days, had the largest individual effect on species' functional traits, but there were also significant interactions between the fire and climate variables. These fire/climate interactions show that the effects of prescribed burns on functional trait diversity cannot be predicted independent of growing season climate. This suggests that land mangers can maximize the effect of prescribed burning as a tool to manage functional diversity by adopting an adaptive approach that incorporates growing season climate forecasts when developing and executing their annual prescribed burn plans.