Methane and nitrous oxide production and their driving factors in Phragmites riparian wetlands of Dianchi Lake, China

The eutrophic lake Dianchi, china, is a hotspot for methane (CH4) and nitrous oxide (N2O) emissions. However, the potential factors driving CH4 and N2O production in the riparian wetlands of Dianchi Lake remain unclear. In the current study, the potential CH4 and N2O production was evaluated using incubation experiments. The abundance and community structure of the methanogenic communities and denitrifying bacteria were measured using quantitative polymerase chain reaction and Illumina MiSeq sequencing. The results indicated that the potential CH4 and N2O production differed significantly among the riparian wetlands of Dianchi Lake, with rates of 0.26–17.65 μg/g.d and 0.09–1.30 ng/g.h, respectively. The soil mcrA, nirS and nosZ gene copies differed significantly among the riparian wetlands, whereas the soil narG and nirk genes did not. Soil methanogenic archaea in the riparian wetlands were dominated by the order Bathyarchaeia (2.36–45.97 %). Forty-one potential denitrifying bacterial genera were detected in soils from the riparian wetlands, among which the majority belonged to the Proteobacteria (31 genera; 1.54–37.78 %). The variation in CH4 production was mediated through soil AP, water NO3−-N and soil mcrA abundance, while water NH4+-N, soil TN and soil NH4+-N were the main factors regulating N2O production in the riparian wetlands of Dianchi Lake. Our study highlighted the important implication of pollution abatement to greenhouse gas emission reduction in the riparian wetland.