不同耕作措施下双季稻田生态系统碳循环及其生态服务价值

耕作方式对稻田碳循环有着较大的影响。采用田间试验方法，研究了秸秆还田条件下，不同耕作措施双季稻田碳循环及其生态服务价值，为稻田生态服务价值计算及土壤固碳潜力评价提供依据。试验于湖南省宁乡县进行，通过静态箱法测定翻耕秸秆还田（CT）、旋耕秸秆还田（RT）、免耕秸秆还田（NT）稻田CH4及CO2排放，根据美国橡树岭国家生态实验室得出的碳折算系数计算各项农资投入的碳释放。结果表明：（1）机械操作造成的碳排放为CT〉RT〉NT，免耕分别比翻耕和旋耕碳减排61．69、35．70bC·hm^-2；（2）含碳农资碳减排对于稻田碳减排具有较大作用，其中减少含碳农资投入对于免耕碳减排作用最大；（3）免耕促进了稻田土壤碳固定，稻田生态系统总体碳固定为NT〉CT〉RT；（4）采用免耕、减少含碳农资投入有利于固碳及增加稻田生态系统服务价值。本研究得出免耕秸秆还田有利于减少碳排放及增加稻田生态系统生态服务价值，建议长江中下游双季稻区采用以免耕秸秆还田为主的保护性耕作。

Ecosystem Service Value and Carbon Cycle of Double Cropping Paddy Under Different Tillage

Tillage influences carbon cycle of paddy greatly. In order to provide theoretical guide for forecasting carbon sequestration potential of soil and evaluating ecosystem service value, a field trial was conducted during 2005 to 2009 to evaluate the performance of the tillage effect on carbon cycle and ecosystem services value. Both early-rice and late-rice straws were returned. During the winter season, rice fields were left fallow under drained. The closed chamber method was used to measure the CH4 and CO2 emission from the paddy field with the treatments of conventional tillage（CT）, rotary tillage （RT）, no-tillage （NT） at Ningxiang County, Hunan Province. Carbon emission of all kinds of agri- cultural inputs had been calculated by using carbon convert coefficient which was from Oak Ridge National Laboratory. The results showed as following： （1）NT reduced carbon emission by 61.69, 35.70 kg C·hm^-2 compared with CT,RT,respectively, with increasing mechanical strength for NT, RT and CT; （ 2 ）The carbon emission reduction of agricultural inputs contributed greatly to carbon reduction, which was the most important carbon reduction aspect for NT; （3）NT was benefit to paddy carbon sequestration; （4）NT and reducing agricultural inputs were benefit to carbon sequestration and increased paddy ecosystem service value. This research got the results that NT attributed to release carbon emission and increase paddy ecosystem service value. So we suggest using NT, which is the main tillage method in conservation tillage, in the double paddy soil area.