The effects of elevated CO 2 and temperature on the quantity and quality of dissolved organic carbon (DOC) of wetland sediments were investigated by measuring organic matter decomposition rates and phenolic compounds as target recalcitrant organic matter. Mean rates of anaerobic microbial metabolism were consistently higher both in vegetated sediments and in elevated CO 2 and temperature, although the differences were not statistically significant (P , 0.05). Concentrations of phenolic compounds in sediments with vegetation are significantly different (P , 0.05) from those in sediments without vegetation. Regarding the biodegradability of the phenolic compounds, vegetated sediments showed higher concentrations of 2-chlorophenol and 2,4-dimethylphenol under elevated CO 2 and temperature conditions, which means that more refractory material can be produced through enhanced organic matter degradation by elevated CO 2 and temperature. The produced phenolic compounds can be transported to the freshwater ecosystem and influence the recalcitrance of DOC. Water Environ. Res., 86, 779 (2014).
This study investigated the effects of elevated CO2 and nitrogen addition on the anaerobic decomposition mediated by microorganisms to determine the microbial metabolic pathways in the degradation of organic matters of the sediments. There were statistically significant differences(P < 0.05) in the rates between denitrification and methanogenesis upon increased CO2 concentration, nitrogen addition, in the presence of plants. Based on the assumption that anaerobic degradation of organic matter mainly occurs through denitrification, iron reduction, and methanogenesis, methanogenesis is the dominant pathways in the decomposition of organic matter under the condition of elevated CO2 and nitrogen addition. In addition, the altered environment increased anaerobic carbon decomposition. Therefore, it can be concluded that freshwater wetland sediments have positive effects on the global warming by the increased methanogenesiss as well as increased anaerobic carbon decomposition.
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