Net Ecosystem Exchange of CO2 and C-Sequestration Potential of a North Alabama Forest during Different Seasons.

Alabama has the third most timberland acreage in the 48 contiguous states with about 23 million acres of timberland accounting for 68% of the total land area in the state. Many of the forests are undergoing different restoration programs in order to reduce the susceptibility of the forests to future outbreaks such as the Southern Pine Beetle problem. As the forests undergo different restoration projects, their productivity (the rate at which the forests remove carbon dioxide from the atmosphere and store in live woody tissues -biomass) will remain the main consideration for their management. Net ecosystem exchange (NEE) of carbon dioxide (a measurement of how much carbon is entering and leaving the ecosystem) is a good estimate of gross primary production, the amount of biomass that primary producers produce in a given ecosystem. For agro-forestry ecosystems in particular, NEE measurement by using the eddy covariance (EC) technique has been used to characterize the fluxes in photosynthetic uptake of CO₂ by plants and ecosystem release of CO₂ by plant respiration and decomposition. The objective of this study was to estimate the seasonal variations of net ecosystem carbon exchange in a mid-aged southern mixed forest located in the William Bankhead National Forest, Alabama, USA. Eddy covariance equipment was used to measure mass and energy fluxes over the forest. The sensor array included a LI-7500A Open Path CO2/H2O Analyzer, a CSAT3 three-dimensional sonic anemometer, NR-LITE Net Radiometer, and a Photosynthetic Active Radiometer sensor mounted on a 130 ft-tall tower in the Forest. The 180, 000 acre forest is dominated by Loblolly Pine/Shortleaf Pine, and Oak/Hickory. The canopy height is 80-90 ft. The eddy fluxes of sensible heat, latent heat, CO₂ and momentum will be calculated from the measurements. The data will be analyzed to show the seasonal variations of NEE and the major drivers for the seasonal variations such as gross primary production (GPP) and ecosystem respiration (Re), and whether the forest is a net carbon source or sink.