Nitrous Oxide Emissions from Newly Created Littoral Marshes in the Drawdown Area of the Three Gorges Reservoir, China

摘要

This study aimed to understand the seasonal and spatial variations of N_2O emissions from newly created littoral marshes in the drawdown area of the Three Gorges Reservoir (TGR), China. We measured N_2O emissions at 10-day intervals during the growing season (early July to late September) in 2008. N_2Ornemissions were measured with static chambers in four typical vegetation stands. The results showed great spatial variations of N_2O emissions among the four stands. The greatest N_2O emissions (0.052±0.063 mg N_2O m~(-2)h~(-1)) were from Scirpus triqueter stand, while the lowest N_2O emissions (0.020±0.020 mg N_2O m~(-2) h~(-1)) were from Typha angustifolia stand. To such spatial variations in N_2O emissions, standing water depths and soil water content may be important explaining factors. Besides spatial variations, we also found significant temporal variations of N_2O emissions in this area. The temporal variation of N_2O emissions in the growing season was not found significantly related to any measured factor in the study. However, based on principal component analysis, we consider it partly caused by thermal conditions and the marked temporal variation of the standing water depth in the growing season, which to some degree influenced the process of denitrification and N_2O emissions. These results about TGR enable us to make a more reasonable estimate of N_2O emissions from large dam reservoirs, particularly those with a large drawdown area in the growing season in an agricultural landscape.