Fire Lines Volume 12 Issue 5
Research Brief
Season of prescribed burns and management of an early successional species affect flower density and pollinator activity in a pine savanna ecosystem
Authors: Opeyemi A. Adedoja, Raelene M. Crandall, and Rachel E. Mallinger
Prescribed burn in longleaf pine savanna at the study site. Credit: Dr. Raelene Crandall
In a nutshell: Prescribed burning and mechanical removal of yankeeweed (Eupatorium compositifolium Walter) enhanced flower density and pollinator activity in an early-successional longleaf pine savanna. These effects were different depending on the seasonal timing of the burns and whether fire had occurred in the area in the same year. The results suggest that land managers should use longleaf restoration strategies that include a regular schedule of prescribed burning that alternates between dormant and growing seasons.
Effective longleaf ecosystem management requires regular application of prescribed fire every one to three years to mimic the natural fire return interval. Land managers in the southeast often conduct prescribed burns in the winter dormant season rather than in the late spring or summer when most natural lightning fires would have historically occurred. It is unclear how differences in the seasonal timing of burns can lead to different ecological outcomes. This study examined the effect of the seasonal timing of fire on flowering plant communities and associated pollinators. It also looked at how burn timing interacts with the removal of dominant vegetation, another common management practice.
The study took place over three years on a recently restored upland pine savanna in north central Florida. Three different burn treatments were used, each occurring at a different time of year: winter-dry, spring, and summer-wet. A no-burn control condition was also used. Within each burn plot, yankeeweed was removed from one subplot and left undisturbed in another subplot. Prescribed fire treatments were applied twice to each burn plot: once each in the first and third years of the study. Yankeeweed removal occurred in the first year.
Data on flowering plants and pollinators were collected during the second year when no burning was conducted (non-burn year) and the third year when the second round of burn treatments was applied (burn year). Flower data included the number of flowers (density) and the number of species in bloom (richness). Pollinator data were counts of pollinators encountered in a five-minute period (activity).
The use of prescribed fire resulted in increased flower density, but this effect varied by burn treatment and the occurrence of fire in the same year. Greater flower density was associated with summer-wet burning in the non-burn year and spring burning in the burn year. Pollinator activity showed similar patterns. In the non-burn year, pollinator activity was greater in plots that burned in the spring or summer-wet. In the burn year, increased pollinator activity was associated with spring burning and winter-dry burning. Independent of the different burn treatments, flower density, flower richness, and pollinator activity all increased as a function of time after a burn.
