黄土区干化土壤再植苜蓿生长与土壤水分的协同互馈机制

黄土高原人工林草植被造成规模化深层土壤干化，土壤水环境退化不但加速现有植被衰败，还将严重影响后续多年生深根系植物可持续更替，但有关土壤干化再种植多年生深根系植物的研究十分少见。本项目面向黄土区干化土壤可持续利用与生态安全的国家重大需求，围绕变化环境下土壤水分生态过程对植被再建造影响这一核心科学问题，选择宁南典型深层干化土壤地段，采用径流小区种植苜蓿试验，测定干化土壤再种植苜蓿后土壤水分、降水入渗、苜蓿生长等指标。应用Hydrus-1D模型和Penman-Monteith模型对土壤水分动态及苜蓿地蒸散耗水进行模拟。研究深层干化土壤再种植苜蓿根、冠生长与土壤水分的互馈规律，包括再种植苜蓿后干化土壤水分时空变异特征及降水入渗对苜蓿根系分布的调控作用，揭示再种植苜蓿生长对水分的响应机制，探讨提高水分利用效率的策略，评价干化土壤可持续利用的途径，为半干旱黄土区干化土壤再建造植被奠定科学基础。

Artificial vegetation on the Loess Plateau has caused deep soil desiccation. The degradation of soil water may seriously affect the decline of exsiting vegetation and the growth of replanted deep-rooted perennials. However, there are few research regarding on new-planted deep rooting vegetation in dry soil conditions. Based on government demands for Sustainable Utilization of Dry Soil and Ecological Safety on the Loess Region , the aim is to solve the scientific problems on the vegetation rebuilding by the effect of soil water by replanting Alfalfa on deep dried soil layers in selected Runoff areas of the south of Ningxia province, China. Soil water, precipitation infiltration depths and Alfalfa growth indices were monitored. Hydrorus-1D and Penman-Monteith models were used to simulate soil water dynamics and Evapotranspiration of Alfalfa. This research will help to find the relationship between soil water and root/crown growth of Alfalfa, including spatial variability of soil moisture and the regulation of precipitation infiltration on Alfalfa root distribution on deep dried soil layers. Our findings may reveal the response of soil water to the growth of replanted Alfalfa and provide a scientific foundation for exploring strategies to enhance water use efficiency and evaluating sustainable use of desiccated soil and vegetation rehibitation on the Loess Plateau.