作 者 ：张丽华,宋长春,王德宣,王毅勇,顾江新
期 刊 ：生态学报 2007年 27卷 4期 页码：1442~1449
Keywords:exogenous nitrogen, freshwater marshes, CH4 and N2O fluxes,
摘 要 ：三江平原沼泽湿地受到大气沉降、地表径流、农业排水等外源氮素的输入，对湿地生态系统CH4和N2O通量有重要影响。采用野外原位施肥试验模拟外源氮输入，设0，60，120，240kgN•hm-2 4种试验处理，探讨外源氮对沼泽湿地CH4和N2O通量的影响。结果表明，外源氮促进了CH4和N2O排放。与对照处理比较，各施氮水平CH4平均排放通量分别增加了181％，254％和155％，N2O排放通量分别增加了21％，100％和533％。外源氮输入对CH4排放的季节变化形式影响不大，而N2O的季节变化形式随着氮输入表现出波动变化的趋势。不同施氮水平对CH4排放的促进作用与植物生长阶段和产CH4的微生物过程密切相关，N2O排放通量随氮输入量呈指数增加（R2＝0.97，p<0.01）。外源氮通过影响湿地微生物过程来进一步影响CH4和N2O的排放。
Abstract:CH4 and N2O are the two main greenhouse gases with great contribution to global warming. Natural wetland in the north hemisphere is recognized as one of the most important global sources of atmospheric CH4. But its role in contribution to N2O is not clear. Nutrient enrichment may impact the greenhouse gas emission from freshwater marshes. As the largest freshwater marsh distribution area in China, Saijiang Plain has experienced the extensive reclamation over the past 50 years. Large area of the marshes was drained for agricultural production. The remained marshes are often subject to high levels of nitrogen enrichment from atmospheric deposition, surface runoff loading and agricultural drainage, which affected the CH4 and N2O emission from marsh ecosystem. In this work, we discuss the effects of exogenous Nitrogen on the CH4 and N2O fluxes of marshes using an in situ field fertilization experiment with the static chamber technique. Ammonia Nitrate solution were applied at a rate of 0 (control), 60, 120kgN•hm-2 and 240kgN•hm-2. Monitoring results showed the maximum CH4 flux of these four levels is 3.67mg CH4 m-2 h-1 ,11.01 mg CH4 m-2 h-1, 11.28 mg CH4 m-2 h-1 and 5.82 mg CH4 m-2 h-1, While the maximum N2O flux is 0.27 mg •m-2•h-1, 0.65 mg•m-2•h-1, 1.0 mg•m-2•h-1, 2.26 mg•m-2•h-1. The results indicated exogenous nitrogen input increases the CH4 and N2O emission. Comparing with the control level, the CH4 flux of other three fertilization levels increases by 181％, 254％and 155％, and the N2O fluxes increased 21％, 100％and 533％, respectively. During the growing season, nitrogen input does not have obvious influence upon the seasonal dynamic pattern of CH4 emission flux. But every Nitrogen input, especially of the highest level, brings about the obvious fluctuation of the N2O emission flux. With the increasing of nitrogen input, there is an exponential increase trend of N2O flux (R2＝0.97，p<0.01).CH4 flux under the high nitrogen input was lower than those under the low and medial nitrogen input，which was related to the plant growing stages and the microbial activity of CH4-producing. The exogenous nitrogen input changed the CH4 and N2O fluxes not only via the direct effect but also by affecting the wetland microbial process.