太湖流域典型下垫面土壤水响应规律及影响因素

Responding patterns and influencing factors of soil moisture under different underlying surfaces over the Taihu Lake basin

为揭示不同土地利用/覆被下土壤水动态变化规律,选取太湖流域城市绿地、耕地和林地3种典型土地利用/覆被类型,开展了连续(2018—2020年)原位观测(1h间隔),剖析了不同下垫面的土壤水响应规律及主要影响因素。研究表明:随着土壤深度增加,降雨后土壤含水量峰值逐渐增加(埋深10、20、40 cm分别为25.90%、28.06%和31.24%),而土壤水增幅、增加速率和消退速率逐渐降低;土壤水响应时间从上层到下层先增加后减小,耕地和林地深层土壤的响应时间快于中层;随降雨量级增加,各土壤水响应特征均呈现逐渐增加趋势;土壤水动态变化受到了降雨、物理参数、植被、前期湿度等多种因素影响,但不同土壤水响应特征的主导因素有所差异;前期湿度是土壤含水量峰值、增幅和增加速率的主导因素,前期含水量越高,土壤含水量峰值相对越大,但增幅和增加速率越小。研究结果可为不同土地利用/覆被下产汇流机理分析和水资源管理提供依据。

Soil moisture plays a crucial role in connecting rainfall,runoff,and groundwater processes.Investigating the dynamic changes of soil water under different land use/covers is of great significance for understanding the mechanisms of the water cycle.Taking the Taihu Lake basin as a case study,this paper selects three representative underlying surfaces,i.e.,urban green land,farmland,and forest land,to conduct continuous in-situ observations during 2018 and 2020.A method for identifying and extracting characteristics of soil moisture responses to rainfall events was proposed,and a total of 801 soil moisture responding events(with 1-hour interval)were observed.Then the response patterns of soil moisture and main influencing factors for typical underlying surfaces were revealed.The results suggest that the responses of soil moisture display distinct characteristics in vertical profile,and the peaks of soil moisture for 10cm,20cm,and 40cm depth gradually increases(i.e.,25.90%,28.06%,and 31.24%,respectively),while the increasement,rate of increase,and rate of recession of soil moisture gradually decrease.The responding time of soil moisture increases firstly and then decreases from the surface to the deep layers,and responding time of soil moisture for cultivated land and forest land in deep layer is faster than that of the middle layer,mainly due to the preferential flow effects influenced by large pores in soil.With the increase in rainfall intensity,all responding characteristics of soil moisture show a gradually increasing trend for different land use/covers.The dynamic changes of soil moisture in the Taihu Lake basin are influenced by multiple factors such as rainfall,soil parameters,vegetation,and antecedent wetness,however,the dominant factors for different responding characteristics vary.The antecedent wetness is the primary factor that influences the peaks,increasement and rate of increase of soil moisture.Specifically,a higher antecedent wetness leads to a greater soil moisture peaks,but a smaller increasement and rate of increase of soil moisture.These results could provide a reference for the analysis of water yield mechanisms under different land use/covers in the Taihu Lake basin,and support the agricultural production and water resources management.