长三角水稻土进化过程中有机碳库变化研究- - 以绰墩山发掘的两个古水稻土埋藏剖面为例

Soil carbon sequestration and carbon cycle research is the final frontier of soil science, which is related to global climate change and biodiversity development. Paddy soil is a type of anthrosols greatly influenced by agricultural activities and environmental changes. In general, paddy soil management introduces plant (rice) debris and exudates, and its associated microbial biomass into soils; through artificial submergence or drainage, ploughing and fertilization (manuring), affecting paddy soil development. In fact, Soil organic carbon deposition is a process generally occured in hydroponic tillage management in paddy soil. There is a more than 7 000 a history of rice cultivation in China. However, how soil organic components changed with evolution of paddy soil in the big time scale is whereas what the authors want to know. Two entire ancient buried paddy soil profiles, excavated in Chuodunshan Relics (31 24' 07'' N, 120 50' 41'' E) that have been verified to be the earliest ever found irrigated rice fields, could may be as a perfect research carrier to study on changes of soil organic components and effects of hydroponic artificial tillage and environmental changes on evolution of the paddy soil in the Yangtze River Delta region..Lipids, as one of the minor constituents of organic components in soil, are a heterogeneous group of organic substances, operationally defined as being insoluble in water but extractable with non-polar solvents, include alkanes, carboxylic acids, alcohols, PAHs, and so on, and are documented to be one of the important biomarkers for the global or local changes, but also keep a record related to the anthropogenic activities..In the proposal, hence, two entirely buried ancient paddy soil profiles from prehistoric (6280 a 14C BP) to present collected from a typical paddy field in Yangtze River Delta region will be as a case study to evaluate the influence of hydroponics management on the carbon cycle in paddy fields, the lipids biomarkers as well as total organic carbon contents and δ13Corg are used to trace changes of paddy soil organic carbon under the hydroponics management and natural environmental change over the last six millennia period.

土壤固碳和碳循环研究是目前土壤学的最新前沿。水稻土是人为熟化特殊的湿地土壤，固碳趋势明显，固碳潜力较大。我国植稻已有7000年的历史，但大时间尺度上水稻土有机碳库的变化研究鲜见报道。对水稻土有机碳固定/稳定机制和不同农业管理措施下变化的研究存在知识缺陷。发掘于江苏省苏州市绰墩山遗址的两个整段的古水稻土埋藏剖面作为一个研究载体或许可以给我们提供一些长三角水稻土进化过程中有机碳库变化及水耕管理和环境变化对其影响的信息。因此，本项目以这两个古水稻土埋藏剖面为主要研究对象，运用脂生物标志物结合分子碳同位素地球化学指示技术，通过解析剖面土壤脂组分、主要生物标志物比率和碳原子数分布模式，鉴定并定量分析时间序列（史前、古代、现代）水稻土剖面稳定性有机碳含量及组分变化，探索水耕管理和环境变化对水稻土有机碳稳定性，特别是对稳定性有机碳含量和组成的影响，从而揭示长三角水稻土进化过程中有机碳库变化的某些特征。

项目研究背景：土壤固碳和碳循环研究是目前土壤学的最新前沿。水稻土是自然土壤在人为水耕熟化过程中形成的，特殊的人为湿地土壤，其有机碳含量较高、固碳趋势明显，固碳潜力较大。我国植稻已有7000 年的历史，但大时间尺度上水稻土进化过程中有机碳库，尤其稳定性有机碳含量及组分变化研究尚不清楚。对水稻土有机碳固定/ 稳定机理和不同农业管理措施下变化的研究严重不足并存在知识缺陷。2003年在江苏绰墩山遗址发掘过程中发现了两个完整的古水稻土埋藏剖面。这两个整段的古水稻土埋藏剖面作为一个研究载体或许可以给我们提供一些长三角水稻土进化过程中有机碳库变化及水耕管理和环境变化对其影响的信息。.主要研究内容：本项目以绰墩山遗址发掘的两个古水稻土埋藏剖面为主要研究对象，借鉴生物地球化学的一些研究手段，运用脂生物标志物结合分子碳同位素地球化学指示技术，鉴定并定量分析时间序列（史前、古代、现代）水稻土剖面稳定性有机碳含量及组分变化，揭示水耕管理和环境变化等对水稻土有机碳稳定性，特别是对稳定性有机碳含量和组成的影响。.重要研究结果：（1）实证证明了稻田水耕管理显著增加土壤中有机碳、氮的含量；（2）稻田弃耕导致土壤有机碳、氮含量快速下降，有机碳库缩减明显；（3）植硅体与时间序列（史前、古代、现代）水稻土剖面土壤中有机碳含量呈显著正相关关系，表明植硅体包裹有机碳（phytolith-occluded organic carbon）或许可以作为一种生物标志物来表征6000年来长三角区域水稻土进化过程中土壤有机碳的变化。.科学意义：通过研究，对认识水稻耕作模式和城市化进程对长三角地区水稻土进化过程中有机碳库的变化具有重要意义，并为调整现代耕作管理方式以提高水稻土碳捕获和固定能力提供理论指导。