9728363 King Carbon monoxide is a more dynamic component of the atmosphere than methane, occurring at a lower concentration but substantially higher flux. CO and hydroxyl radical interact rapidly, affecting a number of atmospheric parameters: the oxidative state of the troposphere; the fate and residence times of methane, non-methane organics and inorganics; tropospheric ozone; and the extent of thermal forcing. Soils consume atmospheric CO, accounting for 10-25% of the global carbon budget, depending on the source estimate. Some of the controls of soil CO uptake and production have been described generally, but much remains unknown. Details of CO uptake in agroecosystems are particularly sketchy, in spite of the fact that they occupy about 10% of terrestrial surface area, and have a disproportionate impact on a number of important trace gases. Limited field results have suggested that CO uptake in agroecosystems may be equivalent to or greater than uptake in undisturbed systems. Stimulation of CO consumption in agroecosystems could partially ameliorate the inhibition of methane uptake that accompanies agriculture by enhancing the availability of tropospheric OH. Since CO uptake is as much as 10-fold greater than methane uptake on a global basis, small changes in soil CO dynamics (positive or negative) can have a significant impact on the fate of methane. This study will determine specifically the extent to which agricultural practices affect atmospheric CO consumption by soils. Agricultural soils will be compared with similar non-agricultural soils across a gradient of texture using sites in Maine and Georgia. This study will focus on gas exchange, water regimes, temperature, and various agricultural disturbances (fertilization, pesticide use, tilling, no-till), as controls of CO fluxes. The extent to which several microbial groups of CO oxidizers vary as a function of land use will also be determined. The results of this study will establish both rates and the major controls of soil CO dyn amics, as well as the sensitivity of CO uptake to climate change and other anthropogenic perturbations.
