CH4 Oxidation Potentials of Different Land Uses in Three Gorges Reservoir Area of Central Subtropical China

To compare the CH4 oxidation potential among different land uses and seasons, and to observe its response to monsoon precipitation pattern and carbon and nitrogen parameters, a one-year study was conducted for different land uses (vegetable field, tilled and non-tilled orchard, upland crops and pine forest) in central subtropical China. Results showed significant differences in CH4 oxidation potential among different land uses (ranging from -3.08 to 0.36 kg CH4 ha(-1) year(-1)). Upland with corn-peanut-sweet potato rotation showed the highest CH4 emission, while pine forest showed the highest CH4 oxidation potential among all land uses. Non-tilled citrus orchard (-0.72 +/- 0.08 kg CH4 ha(-1) year(-1)) absorbed two times more CH4 than tilled citrus orchard.(-0.38 +/- 0.06 kg CH4 ha(-1) year(-1)). Irrespective of different vegetation, inorganic N fertilizer application significantly influenced CH4 fluxes across the sites (R-2 = 0.86, P = 0.002). Water-filled pore space, soil microbial biomass carbon, and dissolved nitrogen showed significant effects across different land uses (31% to 38% of variability) in one linear regression model. However, their cumulative interaction was significant for pine forest only, which might be attributed to undisturbed microbial communities legitimately responding to other variables, leading to net CH4 oxidation in the soil. These results suggested that i) natural soil condition tended to create win-win situation for CH4 oxidation, and agricultural activities could disrupt the oxidation potentials of the soils; and ii) specific management practices including but not limiting to efficient fertilizer application and utilization, water use efficiency, and less soil disruption might be required to increase the CH4 uptake from the soil.