U.S. Joint Fire Science Program


Date of this Version


Document Type



Final Report: JFSP Report Number: 11-3-1-21


US government work.


Soil CO2 efflux (Rs) is a significant flux of carbon dioxide from ecosystem soils to the atmosphere and is a critical component of the total ecosystem carbon budget. Rs fluxes are comprised of autotrophic (Ra) sources of CO2 produced by plant roots and associated rhizosphere fungi and heterotrophic (Rh) sources of CO2 produced by aerobic soil microbes. A variety of forest management activities, including prescribed fire and mechanical fuels mastication treatments have been shown to significantly influence Rs rates in forests of the Western United States (US), yet these relationships are not well known for southeastern US forests. Prescribed fire is one of the most prevalent forest management tools employed in the southeastern US, and mechanical fuels treatments are becoming more common in the region as efforts to mitigate potential wildfire behavior in the wildland urban interface grow. Given that many of these forests provide habitat for endangered species, understanding the implications of management activities on ecosystem carbon dynamics may allow landowners to capitalize on future alternative revenue streams for carbon sequestration services while maintaining their properties in conserved states. This study investigated the influence of prescribed fire and mechanical fuels mastication treatments on Rs rates in longleaf / slash pine flatwoods of the Osceola National Forest in North Florida. In the flatwoods forests, neither mechanical fuels treatments nor prescribed fire significantly altered monthly mean Rs rates. Prescribed fire, mechanical fuels mastication, and mechanical fuels mastication followed by prescribed fire were found to significantly increase mean soil temperature within the flatwoods sites. Future research is needed to understand whether the changes in soil temperature will ultimately lead to altered decomposition rates and soil carbon fluxes. Our results however, found no evidence of elevated soil CO2 fluxes within one-year of mastication treatment. Our results suggest that future methods to model soil carbon fluxes in the region should account for the impacts of land management activities on soil temperature, a key driver in soil carbon dynamics.