Carbon dioxide and methane fluxes: seasonal dynamics from inland riparian ecosystems, northeast China.

Riparian wetland ecosystems have been described as significant hotspots for carbon dioxide (CO2) and methane (CH4) fluxes, but their role in the release and sequestration of these greenhouse gases has been insufficiently assessed within China. The influences of vegetation and soil parameters on daily and seasonal variations in carbon flux in the Nenjiang basin, northeast China, were recorded using a static closed-chamber technique during the non-growing (November and January) and growing (June, July and August) seasons of 2009-2010. Seasonal differences in average CO2 flux were observed (growing season: 6.605g·C·m(-2)h(-1); non-growing season: -0.185g·C·m(-2)h(-1)) and these were significantly correlated with CH4 emission (r=0.532, p=0.011) and soil temperature at 5 cm depth below ground (r=0.852, p=0.000). Average diel gaseous flux showed significant variation between hours for both gases (CO2 flux one-way ANOVA F=3.075, p<0.01; CH4 flux one way ANOVA F=2.622, p<0.05). Various significant correlations were also found between CH4 and CO2 fluxes and multiple vegetation and soil parameters. For example at both sites, growing season-CH4 flux was correlated with vegetation cover (r=0.580, p<0.05) and total vegetation phosphorous (r=0.474, p<0.05). This study allowed key temporal differences in gas release and their potential biotic and abiotic drivers to be identified. Crucially, it also highlighted important areas in need of further research, to enhance our understanding of gaseous flux from inland riparian habitats.