基于电阻率成像的沙地土壤水分监测技术

The monitoring technology of soil water content in sandy land based on electrical resistivity tomography

土壤水分是影响干旱半干旱区植物生长的主要因素,快速准确、长期连续地监测土壤水分时空动态可为干旱半干旱区植被建设与生态恢复提供科学依据。以乌兰布和沙漠东北部灌木林地土壤为研究对象,应用多电极电阻仪对林地土壤电阻率进行了测量,同步采取土样用烘干法测定了土壤实际含水率,建立了2者之间的相关关系,并对剖面上土壤水分空间特征进行了分析。结果表明:1)土壤含水率(y)与土壤电阻率(x)之间为极显著负相关关系(R2=0. 81,P <0. 01),可用幂函数y=88. 68x-0. 63表示。2)强降水之后,二维剖面上土壤水分整体呈增加趋势。随着雨后时间的延长,1m以上土层的含水率由于受蒸发和植物蒸腾耗水而明显降低,1m以下土层的含水率由于受上层水分入渗有增加趋势,说明连续强降雨(81. 2mm)能对1m以下土层的土壤水分进行有效补给。3)多电极电阻率成像技术在野外能够快速准确,长期定位监测土壤水分含量;且对地表扰动小,实现了非破坏性测量;能够提供尺度较大、分辨率较高的土壤水分二维分布图像及水分入渗过程的图像,是今后中等尺度上监测土壤水分的一种新途径。

Soil moisture plays a major role in plant growing in the arid and semi-arid area.Rapid,accurate,continuous and long-term monitoring of soil moisture can provide guidance for vegetation construction and ecological restoration in the arid and semi-arid area.Selecting shrub land in northeastern edge of Ulan Buh desert as the research object,the relationship between the moisture content measured by multi-electrode electrical resistivity tomography and the moisture content measured by drying method was established.Spatial features of the soil electrical resistivity and soil moisture were analyzed.The results showed as follows: 1) There was extremely significant negative correlation( R^2= 0.81,P < 0.01) between soil moisture content and soil resistivity and it could be expressed by the power function y = 88.68 x^-0.63.2) After heavy precipitation,the soil moisture showed increasing tendency.As the rain continuing,soil moisture of surface layer below 1 m showed a significant decrease from surface layer to 1 m due to the evaporation and transpiration;soil moisture of soil surface below 1 m had a tendency to increase because of infiltration,which indicated that continuous heavy rainfall can effectively supply soil moisture in the soil surface below one meter.3) Multi-electrode resistivity can monitor soil moisture quickly and accurately in the field over a long-time scale.It also can provide large-scale and high-resolution image of soil moisture and water infiltration process.It provides a new method for measurement of soil moisture in a medium-scale in the future.