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Nitrous Oxide Emission from Deyeuxia angustifolia Freshwater Marsh in Northeast China

Yu, Junbao, Liu, Jingshuang, Wang, Jinda, Sun, Weidong, Patrick, William H. Jr., Meixner, Franz X.
Environmental management 2007 v.40 no.4 pp. 613-622
Calamagrostis, air, biomass, ecology, freshwater, greenhouse gas emissions, growing season, humans, marshes, nitrous oxide, redox potential, soil, temperature, China
Here we report N₂O emission results for freshwater marshes isolated from human activities at the Sanjiang Experimental Station of Marsh Wetland Ecology in northeastern China. These results are important for us to understand N₂O emission in natural processes in undisturbed freshwater marsh. Two adjacent plots of Deyeuxia angustifolia freshwater marsh with different water regimes, i.e., seasonally waterlogged (SW) and not- waterlogged (NW), were chosen for gas sampling, and soil and biomass studies. Emissions of N₂O from NW plots were obviously higher than from the SW plots. Daily maximum N₂O flux was observed at 13 o'clock and the seasonal maximum occurred in end July to early August. The annual average N₂O emissions from the NW marsh were 4.45 μg m-² h-¹ in 2002 and 6.85 μg m-² h-¹ in 2003 during growing season. The SW marsh was overall a sink for N₂O with corresponding annual emissions of -1.00 μg m-² h-¹ for 2002 and -0.76 μg m-² h-¹ for 2003. There were significant correlations between N₂O fluxes and temperatures of both air and 5-cm-depth soil. The range of soil redox potential 200-400 mV appeared to be optimum for N₂O flux. Besides temperature and plant biomass, the freeze-thaw process is also an important factor for N₂O emission burst. Our results show that the freshwater marsh isolated from human activity in northeastern China is not a major source of N₂O.