PARENT SESSION
Poster Session # 11: Disturbance Ecology.
Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Disturbance interactions: Effects of canopy removal and fine fuels on fire characteristics and vegetation response.
Passmore, Heather*,1, Platt, William1, 1 Louisiana State University, Baton Rouge, LA
ABSTRACT- Interacting natural disturbances, especially in frequently disturbed systems, may alter plant communities. Increased fuel loads and openness of the canopy after hurricanes have been postulated to increase fire probability and intensity in Southeastern habitats, potentially converting forests into pine savannas. We predict that if fire effects are modified by a prior wind disturbance such as a hurricane, these effects should be most evident along slopes between upland savannas and downslope hardwood forests. In this study, we experimentally manipulated canopy cover and fuel loads to explore whether hurricanes alter the effects normally expected from fires in the ecotone between frequently burned second growth savanna and downslope hardwood forests. We measured characteristics of fires and responses of vegetation. Canopy cover was reduced by removal of approximately 10 canopy trees per plot. We manipulated fuel type by adding longleaf pine, mixed pine, and deciduous fine fuels to different 1m2 vegetation subplots. Reduced canopy cover resulted in increased light levels at both 0.65m and 1.5m compared to undisturbed plots. Canopy removal resulted in higher maximum temperatures in fires. Maximum fire temperatures also differed with fuel types. Mean maximum fire temperatures were lower for hardwood fuels and controls than both pine fuel types. There were also significant interactive effects between canopy removal and fuel additions on maximum fire temperatures. Canopy removal and pine fuel type treatments resulted in decreased mean stem density in canopy removal plots compared to hardwood fuels and controls. Fuel additions resulted in fires with higher maximum temperatures and reduced plant survival and density compared to control plots. In this study, prior canopy disturbance modified the effects of subsequent fires and also influenced understory vegetation. Repeated interactions between these frequent, natural disturbances may influence the composition and structure of ecotones between Southeastern pine savannas and downslope forests.
Key words: longleaf pine savanna, vegetation response, disturbance interactions, fire