Soil CO 2 Fluxes and Carbon Storage As Influenced By Thinning and Burning Practices in the Bankhead National Forest in Alabama.

Forest ecosystems play an important role of fixing atmospheric carbon dioxide (CO₂) into carbohydrate via photosynthesis. In addition to supplying oxygen into the atmosphere, forest ecosystems play a key role in sequestering carbon (C) in the form of above and below ground woody biomass, some of which can be sequestered as soil organic carbon. This study investigated the effect of thinning and burning forest management practices on soil CO₂ fluxes and C storage in a forest ecosystem in the Bankhead National Forest in North Alabama in 2011, 2012, and 2013. Soil gas samples were collected using custom built static chambers and analyzed for CO₂ concentration using a Varian model 450 gas chromatograph equipped with a thermal conductivity detector (TCD) for CO₂ analysis. Soil total C content was measured using the Dumas dry combustion method on an Elementar CNS analyzer. Average CO₂ flux in forest stands which were not thinned and not burned was 0.46 mg m^-2 min^-1 compared to 0.47 mg m^-2 min^-1, 0.65 mg m^-2 min^-1, and 0.79 mg m^-2 min^-1, respectively, in plots which were thinned to 11m² and not burned, in plots which were not thinned but were burned every 3 years, and in plots which were thinned to 11m² and burned every 3 years. Soil total C content average over three years (2011, 2012, and 2013) in the 0-30cm soil profile in plots which were not thinned and not burned was 11.3 gkg^-1 compared to 11.4 gkg^-1 in plots which were thinned to 11m² and 13.8 gkg^-1 in plots which were thinned to 17m².  This study suggests that thinning and burning forest management practices affect the soil’s capability to act as a source or sink of C which can, in the long-term, significantly impact C sequestration in forest soils.