Seasonal and Spatial Variation of Nitrogen Oxide Fluxes from Human-Disturbance Coastal Wetland in the Yellow River Estuary

摘要

Anthropogenic activities strongly affect greenhouse gases emissions in coastal wetland. In situ field study was conducted to explore the effects of anthropogenic activities on the N2O emissions, used static, manual stainless steel chambers in four seriously disturbed coastal wetlands (west side of the seawall, WSS; oil field existed, OF; Spartina alterniflora coastal marsh, SCM; and aquaculture pond, ACP) in the Yellow River estuary. Results showed that N2O emissions showed significant seasonal variation (p0.05). The maximum values were found in August at WSS and ACP, in December and April at SCM and OF, while minimal values were observed in April, February, October, and August, respectively. The annual average N2O fluxes from WSS, OF, SCM, and ACP were 13.24, 9.83, 8.11 and 2.70g N2O m(-2)h(-1), and the variance analysis results showed that the difference between WSS and ACP reached significant level (p0.05). For each month, significant differences were observed between WSS and ACP during June, December and February, WSS and SCM during October, and SCM and ACP during December (p0.05). Basing on previous natural wetland measurements, we found that seawall construction and S. alterniflora invasion significantly affected the N2O fluxes in the Yellow River estuary, especially seawall construction which accelerated N2O emissions due to its block of seawater migration, resulting in changes of soil physicochemical properties. Pearson correction analysis showed that significant correlations were observed between N2O emissions and electrical conductivity at WSS and OF, while other environmental factors (temperature, water content, total carbon, total nitrogen, C/N ratio) had no significant effect, which indicated that electrical conductivity was the most important factor that affected N2O emissions in these sampling sites. Our results suggested that there could be considerable changes of N2O emissions as a response of artificial disturbance, particularly seawall construction.