林木根系对溶质优先运移的影响机制研究

The goal of this research project is to explore the difficult problem of quantifying the relationship between structure of tree roots and the formation and migration of solute preferential transport. Based on the long-term ecological observation at the capital forest ecosystem research station and the solute preferential transport device which was built in the early stage, combining field test, indoor experiment, data processing and model building, we will map the process of soil solute preferential transport, distinguishing preferential flow area and matrix flow area, analyzing migration rules of moisture and solute in two regions, determining the types and probability distribution functions of preferential flow in the study area, revealing the formation and migration rules of solute preferential transport in root - soil zone. We will analyze the impact mechanisms of tree root systems on solute preferential transport by using the devices for solute preferential transport, which include root systems and synchronous tracer, image analysis and monitoring, and construct a process based model of the impact of roots on solute preferential transport. This research project will play an important role for reasonable use of water, effective watershed managing, water resources controlling and water quality improving, and also will provide technological instructions and research methods for a sound environmental construction at a regional level.

研究针对长期以来林木根系的种类、结构与溶质优先迁移的形成和运移具有何种量化关系这一难题，以首都圈森林生态系统鹫峰国家森林公园定位试验站的长期定位观测及申请者前期构建的溶质优先迁移装置为基础，野外试验、室内实验、数据处理、模型构建相结合，获取土壤溶质优先迁移过程图，区分优先流区和基质流区，分析水分及溶质在两区的运移规律，确定优先流的概率分布函数及研究区域优先流类型，揭示根土层内溶质优先迁移形成及运移规律；构建研究区域根系的生长结构模型，利用建立的具有同步示踪、影像监测功能，且添加根系的溶质优先迁移实验装置，开展根系对溶质优先迁移的影响实验，构建林木根系对溶质优先迁移影响的过程模型，定量分析林木根系对溶质优先迁移的形成驱动和运移影响。研究将在首都水资源合理利用、有效流域管理、减缓首都水量减少、水质恶化等方面发挥重要作用，并将为区域生态环境建设提供理论指导及研究技术手段支撑。

优先流是一种可以促使溶质沿着根孔、土壤裂隙、动物孔洞等大孔隙优先路径进入深层地下水的现象。林木根系是土壤层的重要组成部分，根系在土壤内可形成巨大的空间网络结构，形成根系通道，加快优先流入渗过程。本研究以鹫峰森林公园定位生态站和密云水库为研究区域，采用染色示踪法、CT扫描技术、工业内窥镜技术，定量分析研究区域根系与优先流形成、驱动以及迁移之间的关系，并成功获得根孔内部结构特征。研究表明优先流区中植被根长密度和根系生物量都大于基质流区。不同径级根系对优先流贡献不同，直径越细的根系对优先流贡献率越大。通过CT扫描技术可以得到植被根系对石砾分布、大孔隙数量和迂曲度影响显著。根系延伸可以使得土壤中石砾位置发生移动，根系含量较高的土壤层，其大孔隙数量越大，迂曲度越小，这种富含根系的土壤结构有利于优先流发生，减少径流对地表的侵蚀作用。根系在根孔中松散分布，无根毛，与孔壁接触不紧密，根系会将孔隙分割成若干小孔隙，从而影响水流在根孔中的运移过程。本项目共发表文章16篇，其中SCI6篇，中文核心9篇，获得发明专利1项，形成行业标准1项，获得奖励2项，项目组成员在国际会议进行多次交流，对研究内容有了更深入的认识。