中文摘要：

利用开顶箱薰气室，设置正常大气CO2浓度（AmbientCO2，350umol·mol^-1）和高CO2浓度（ElevatedCO2，700μmol·mol^-1）2个水平和不施氮（NN，0gN·m^-2）、常氮（MN，5gN·m^-2）、高氮（HN，15gN·m^-2）3个氮素水平，研究CO2浓度升高和氮肥施用对三江平原草甸小叶章湿地（Calamagrostisangustifolia）土壤活性有机碳及微生物的影响。结果表明，CO2浓度升高条件下，土壤微生物量碳（MBC）和溶解性有机碳（DCK2）呈增加趋势，易氧化有机碳（LOC）和水溶性碳水化合物碳（CHC）的变化因生长期和氮素水平而异。CO2浓度升高，小叶章湿地土壤微生物数量在不同的生长时期呈现不同的响应趋势。细菌数量在腊熟期增幅最大，为31．4％；真菌数量在腊熟期增加16．6％，成熟期增加24．3％；放线菌数量没有发生明显变化。相关分析表明，细菌、真菌和放线菌数量都与土壤微生物量碳呈显著相关。湿地土壤中的活性有机碳可以为土壤微生物提供更多的有效能量，从而加快湿地生态系统养分循环过程。

英文摘要：

An experiment was carried out with treatments different in nitrogen supply （0,5 and 15 gN ·m^-2） and CO2 level （350 and 700 μmol ·mol ^-1 ） on the OTCs （Open Top Chamber） equipment to investigate soil microbial amount and soil active carbon of freshwater marsh in Sanjiang Plain. Results show that elevated CO2 has increased the content of MBC and DOC, while the content of LOC and CHC differed in plant growth stage and nitrogen input under elevated CO2. Stepwise regressions indicate there arc significant correlations belween microhe amount and MI3C. Microbial carbon is regarded as the main index for soil microbe amount of freshwater marsh. All typos of microbe responses to elevated CO2, differed in plant growth stage. Baterial amount shows a large increase in dough stage, up to 31. 4%. The increases in fungi amount due to CO2 elevation is 16.6% and 24.3 % during the dough and muturity stages, respectively. There is no evident change in actinmycete amount. S, oil active carbon provides more energy for soil microbe and the process of nutrients cycling in freshwater marsh ecosystem is accelerated.