长江三角洲水田保护性耕作制度的碳收集效应估算

耕作制度对农田土壤有机碳的稳定和积累作用显著，探讨耕作制度演变下农田土壤碳库动态，将有助于农田土壤碳收集的技术选择及政策制定。利用已发表的田间定位试验数据，构建不同耕作制度下长江三角洲水田耕层土壤有机碳密度的估算模型。依据该区近20多年来耕作制度演变动态，对保护性耕作制度的土壤碳收集效应进行了初步估算。结果表明，油菜面积的扩大、小麦的少免耕和作物秸秆的还田分别约增加土壤耕层有机碳0.94 Tg、2.76 Tg和3.95 Tg，其中以麦稻复种转向油稻复种的单位面积碳收集效应为最高。最后，就碳收集效应估算的方法进行了相关讨论，并就土壤碳收集研究和如何提高土壤碳收集潜力提出了一些建议。

A BRIEF ASSESSMENT OF CARBON SEQUESTRATION EFFECTS OF CONSERVATIONAL FARMING SYSTEMS IN PADDY SOILS OF YANGTZE DELTA PLAIN

Farming system plays an important role in soil organic carbon stability and accumulation.To study soil carbon dynamics of farming system evolution will contribute to farming technology selection and incentive policy making for carbon sequestration in agricultural soils.Therefore,some published-data from long-term field experiments were used to construct assessment model of the change in soil organic carbon density induced by conservational farming systems in paddy fields in Yangtze Delta Plain.In addition,soil carbon sequestration effects of conservational farming systems were primarily assessed based on the change of the farming system in the past 20 years in this region.Results showed that the increase in sown oilseed rape area,reduced-tillage wheat area and straw application area had rises in organic carbon being about 0.94 Tg,2.76 Tg and 3.95 Tg in surface soils(15 cm),respectively.The highest effect of carbon sequestration occurred under the transformation of wheat-rice system to oilseed rape-rice system.Finally,the assessment method was discussed,and some recommendations were put forward for carbon sequestration research and to improve soil carbon sequestration potential.