荒漠绿洲土壤团聚体间孔隙和根系孔隙驱动优先流运动机制

Macropore flow plays a significant role in the frequent transform between surface water and groundwater in the desert-oasis region. Inter-aggregate and root pores are the main components of macrospore in this area. However, macropore flow mechanisms subject to the inter-aggregate and root pores are poorly understood. In this study, preferential flow will be investigated by using soil column simulation experiment, dye tracing in-situ field, Hood infiltration experiment, X-ray computed tomography, and model simulation in the typical desert-oasis region of the Hexi corridor. The objective of this study was to (1) separate the inter-aggregate pore and root pore in oasis soils and quantify pore structural characteristics of the two type's pores; (2) investigate the effects of the inter-aggregate pore and root pore on soil water transport, respectively; (3) study the joint effect of the inter-aggregate and root pores on soil infiltration and solute transport; (4) establish a dual-permeability model of macropore flow in oasis soils. It is helpful to quantify the contribution ratios of the inter-aggregate pore and root pore to soil water transport and to reveal macropore flow mechanisms affected by the two type’s pores. It is also important to advance our understanding of preferential flow mechanism and to develop soil hydrology science in the desert-oasis region. The findings also play a significant role in revealing the transform mechanism between surface water and groundwater and maintaining the health and stability of the desert-oasis ecosystem.

干旱荒漠绿洲区，优先流对地表水与地下水转换过程产生深刻的影响，其中团聚体间孔隙和根孔是该区大孔隙的主要组成部分，但目前关于绿洲团聚体间孔隙和根孔对土壤优先流的影响机制认识还非常有限。本项目选择河西走廊典型荒漠绿洲区，通过土柱模拟、野外染色示踪和Hood入渗试验，结合CT扫描和模型模拟分析，重点研究：（1）绿洲土壤团聚体间孔隙、根系孔隙的分割与结构特征；（2）土壤团聚体间孔隙、根系孔隙对水分运移的影响；（3）团聚体间孔隙和根系孔隙对水分入渗、溶质迁移的共同作用；（4）构建绿洲土壤大孔隙流的双重渗透模型，以期量化团聚体间孔隙和根系孔隙对土壤水分传输的贡献比例，揭示其对土壤优先流运动过程的驱动机制。有望在荒漠绿洲土壤非均质流方面取得新认识，发展干旱区土壤水文学，对揭示绿洲地表水与地下水转换规律、维持绿洲生态系统健康稳定有重要的实践意义。

根据项目计划书，项目围绕“荒漠绿洲土壤大孔隙驱动优先流运动机制”科学问题，主要研究内容包括：（1）荒漠绿洲土壤大孔隙空间特征及影响因素研究；（2）绿洲土壤大孔隙结构特征及对水分运移的影响；（3）绿洲农田根系孔隙特征及对水分运移的影响；（4）确定绿洲土壤大孔隙流的双重渗透模型参数，模拟绿洲土壤优先流运动过程。. 通过4年系统研究，项目量化了荒漠绿洲4种景观类型土壤大孔隙，揭示了绿洲农田土壤大孔隙三维结构特征； (2) 发现根系孔隙和团聚体间孔隙是绿洲土壤优先流发生的主要路径，确定了根系孔隙占土壤大孔隙比例； (3) 集成CT、染色示踪法和双重渗透模型，从土壤孔隙角度阐明了绿洲土壤优先流运动的影响机制，解析了荒漠绿洲土壤优先流主要运动形式；(4) 确定了绿洲化过程土壤大孔隙流传导的水流通量，量化了土壤优先流对水分入渗的贡献。. 项目迄今共发表论文9篇，其中SCI论文5篇，分别发表在European Journal of Soil Science、Land Degradation & Development、Soil Science Society of America Journal、Catena、Vadose Zone Journal、土壤学报、水土保持学报等土壤水文领域内的主流刊物。项目执行中申报了1项发明专利（实质审查阶段）。项目成员参加学术会议10余次，做学术报告6次。项目负责人张勇勇晋升为研究员、博士生导师，入选中国科学院青促会会员；培养硕士研究生3名，协助培养博士研究生1名；积累了河西走廊中部荒漠绿洲土壤结构及优先流运移的大量野外观测数据，逐步形成一个从事干旱区土壤水文学方向的研究小组。研究成果在荒漠绿洲土壤非均质流方面取得新认识，对揭示绿洲地表水与地下水转换规律、维持绿洲生态系统健康稳定有重要的实践意义，提升了干旱区土壤水文学研究水平。