Potential Carbon Gas Production in Southern Brazil Wetland Sediments: Possible Implications of Agricultural Land Use and Warming

Methane (CH4) and carbon dioxide (CO2) are greenhouse gases (GHG) important in the carbon cycle that exchanges carbon between ecosystems and the atmosphere. To determine how rice paddy fields and temperature affect the carbon budget, we experimentally estimated CH4 and CO2 concentrations and production in sediments from natural and rice wetlands over a temperature gradient. Moreover, we estimated how much GHG production rates would increase in these ecosystems, according to the IPCC projections for temperature rise caused by global warming. Our results showed that the concentrations and potential production rates of GHG showed no significant differences between natural and rice wetlands, although the accumulation of organic matter and nutrients was higher in natural wetland sediments. However, temperature elevation played a significant role in the rise of gas production rates. According to our results, projected increased atmospheric temperature may promote increases in the rates of production and concentrations of carbon gases. The potential carbon gases production in the scenario of atmospheric warming indicated that CH4 (18.91%) may be higher than CO2 (4.54%), mainly in rice wetlands. This reinforces the importance of natural wetland conservation.