Methane consumption and carbon dioxide emission in tallgrass prairie: Effects of biomass burning and conversion to agriculture

摘要

Consumption of atmospheric methane and emission of carbon dioxide by soils were measured on unburned and annually burned tallgrass prairie and on adjacent wheat and sorghum agricultural plots in Kansas. Profiles of CH4and CO2concentration with soil depth were also measured. Overall patterns of CH4consumption by soils varied temporally, with soil depth and land use. Mean CH4consumption for the 200‐day sampling period was −1.02 mg CH4m−2d−1(SE=0.13, n=41) for burned prairie, −0.63 (SE=0.09, n=45) for unburned prairie, −0.85 (SE=0.20, n=36) for wheat, and −0.45 (SE=0.08, n=40) for sorghum. Less than 20 of the variance in CH4consumption was explained by soil temperature and/or moisture content. Overall patterns of CO2emission from prairie and agricultural soils varied temporally, but not among land use. Mean CO2emission for the 200‐day sampling period was 15.7 g CO2m−2d−1(SE=1.8, n=41) for burned prairie, 14.5 (SE=1.3, n=45) for unburned prairie, 13.9 (SE=2.1, n=36) for wheat, and 10.3 (SE=2.1, n=40) for sorghum. More than 70 of the variance in prairie CO2emission rate was explained by soil temperature and moisture. Crop management practices influenced the timing of CO2emission from agricultural plots but not the net annual rate of emission. Methane concentrations generally decreased and CO2concentrations increased with soil depth, and the magnitude of CH4and CO2flux generally increased with increased magnitude of the soil gas concentration gradient. Fertilization of agricultural fields had no measured effect on CH4or CO2flux or on soil