Seasonal dynamics in nitrous oxide emissions under different types of vegetation in saline-alkaline soils of the Yellow River Delta, China and implications for eco-restoring coastal wetland

Abstract

Salt-affected soils are extensively present and constitute about 7% of total land surface. However, our knowledge about nitrous oxide (N2O) production through rapid nitrification and denitrification processes between the atmosphere and the saline soil is very limited. In order to evaluate the potential of N2O consumption in saline soils, this study was therefore designed to quantify the variability in N2O emissions monthly in the Yellow River Delta in China. Main issues include: different saline-alkaline soils and temporal aspects. Our aim was to quantify N2O emissions and identify the major drivers controlling its emissions for providing guidance in eco-restoring coastal wetland on large scale. By using in situ closed chambers the annual average emissions of N2O from the mudflat was determined and it was significantly higher than plant communities, especially herbage communities. In general, the emissions of N2O of different ecosystems showed a unique-peak annual pattern, with the peak in September. Saline-alkaline mudflat and different vegetations acted as N2O source in the Yellow River Delta and the N2O emission of different ecosystems followed the order: Saline-alkaline mudflat>T. chinensis >S. salsa>P. australis. Therefore restoration of saline land through revegetation was necessary to reduce the N2O emission of saline soils. The effects of air and soil temperature on N2O fluxes were significant in salt-affected soils except P. australis. Soil water content and electrical conductivity correlated positively or negatively with N2O emissions in mudflat and P. australis community. While relationships between N2O production and other soil properties (TC, TN, C:N ratio, NH4+-N and NO3−-N) were only significant in mudflat and T. chinensis community. Temporal variations of N2O emission were related to the interactions of abiotic factors (air and soil temperature, soil water content and electrical conductivity) and the variations of other soil properties, while spatial variations were mainly affected by the vegetation composition at spatial scale.