季节性冻土农业区生态水文驱动下土壤碳氮输移的热斑与热时段解析研究

As comprehensively affected by long-term high intensive agricultural development and seasonal freeze-thaw cycles, the status of local ecological environment continues to deteriorate in Sanjiang Plain. Agricultural practices compelled soil organic materials and nutrients losses driven by eco-hydrological processes are the primary causes. In this project, the transport of soil carbon and nitrogen representing soil organic materials and nutrients in an agricultural region with the conventional developing mode in Sanjiang Plain are concerned, through Field observation in situ, geospatial analysis and space inversion. The objectives of this project are to explore the eco-hydrological process and driving mechanism influenced by seasonal freeze-thaw cycles, lessive pedogenic profiles and agricultural practices compeller; to interpret complex effects of agricultural practices and managements on soil carbon and nitrogen transport; to reveal the cross correlations of soil carbon and nitrogen transport regularities at regions with different scales; to exposit characteristics of hot spots and hot moments of soil carbon and nitrogen transport through natural and artificial composite systems in the high latitude boreal. The research findings of this project are expected to fill in gaps of theories and frameworks on soil nutrients transport and loss driven by eco-hydrological processes in agricultural regions with seasonal freeze-thaw events, and to play significant roles in environmental pollution prevention and ecological safety regulation in SanJiang Plain.

受大规模高强度农业开发活动和季节性冻融循环的耦合作用，三江平原灌区生态环境持续恶化，人工胁迫下生态水文驱动的农田系统土壤有机质和养分流失是主因。本项目选取三江平原传统型开发模式农业区，关注土壤有机质和养分主要构成元素碳和氮的输移，针对农田景观单元和小流域两种尺度，通过原位观测、空间分析和过程反演等技术，在阐明季节性冻融循环、白浆化成土结构及人工扰动耦合作用下生态水文过程和驱动机制的基础上，探讨农业活动和管理措施等人工配置对土壤碳氮输移过程的复合效用，解析高强度农业开发活动和长期季节性冻融循环胁迫下不同尺度土壤碳氮输移规律的递推关系，揭示中高纬寒温带农区中小尺度自然-人工复合体系下土壤碳氮输移的热斑和热时段特征。研究成果将有效补充季节性冻土区农业生态系统中生态水文驱动的土壤养分输移与流失研究理论和框架，为三江平原区域环境污染防治和生态安全调控提供依据。

土壤有机质和养分流失引发的区域生态和环境恶化是我国农业垦殖区可持续发展面临的关键难点问题。三江平原是我国重要的粮食生产战略基地，多次大规模高强度农业开发活动改变了原有生态系统的结构和功能，加剧耕地土壤有机质和养分流失，造成大量的碳流失和严重的农业面源污染，引发一系列生态破坏与环境污染问题。深入理解并系统把握土壤碳氮在农田景观单元和小流域中的输移特征，有助于补充土壤碳氮污染物环境行为由微观运动到宏观规律的归纳与推论，为环境友好的区域农业管理提供依据。本项目选取三江平原传统型开发模式农业区，针对典型农田景观单元和小流域两种尺度，综合考量了自然环境因素和人工扰动的效用，阐明生态水文过程变化对降水事件的响应反馈，揭示人工配置系统对溶解态碳氮流失的干扰，探讨中小尺度土壤碳氮在生态水文驱动下的流失规律和特征，探索溶解态碳氮及主要离子输出的相互联系与作用，解析了中高纬寒温带农区自然-人工复合体系下土壤碳氮输移的热斑和热时段特征，构建了三江平原农区土壤碳氮输移热斑与热时段的解析方法体系。结果表明：在农田景观单元尺度，降水类型决定了土壤碳氮输出强度，径流量与碳氮输出浓度显著相关，表层地下潜流是溶解态碳氮流失的优先水文路径，农业管理措施明显影响碳氮输出过程和热斑特征；在小流域尺度，水文因子变化受降水控制，溶解态碳氮和主要离子输出具有明显季节性，农业管理措施对碳氮输出特征影响显著；人工沟渠对溶解态碳氮具有明显削减作用，但削减效果在生长季不同阶段存在差异。研究成果有助于揭示三江平原灌区耕地土壤碳氮流失规律与机制，有利于深化对特殊生境区域土壤养分流失的理解，为三江平原集约化农业区土壤碳氮管理与生态环境保护工作提供借鉴和科学依据，为农区水环境污染防控和农业的可持续发展提供理论基础。