三峡山地沟谷不同坡位土壤水分特征及对降雨过程的响应

土壤水分是影响地表植被生长发育及分布格局的重要因子，也是岩石圈-水圈-生物圈-大气圈水分循环的重要环节，其动态变化能够反映土壤水文过程的信息。基于高分辨率时域反射水分探针和小型气象站连续定位监测，获取2018~2019年三峡大老岭地区典型沟谷内坡上、坡中、坡下部位0~80 cm范围内各土层含水量及大气降水数据，分析了不同坡位土壤水分在月尺度，日尺度和小时尺度的变化特征及其对降雨过程的响应。结果表明：（1）月尺度上，土壤水分含量季节性差异明显，春夏季节（5~7月）是土壤水分储蓄期，土壤平均含水率为38.40%，夏秋季节（8~10月）是水分消耗期，剖面土壤平均含水率仅为35.04%。（2）日尺度和小时尺度，不同层次土壤水分含量对降水响应存在差异。0~40 cm深度土壤对降雨响应较快（响应时间<0.5 h），土壤水分与降雨量变化趋势相似；60~80 cm深度土壤对降雨响应存在明显的滞后现象（响应时间滞后0.5~3.0 h），且随深度加深，滞后时间呈阶梯式延长。（3）不同降雨条件下，土壤水分对降水的响应差异明显。随降雨量级由中雨增至大暴雨，土壤水分对降雨的响应加快，含水量变化曲线与降雨过程同步性增强，响应深度也逐层增加，土壤水分增量变大。（4）不同坡位对土壤水分的影响存在差异，上坡位对中雨、大雨响应平稳，中、下坡位对降水响应强烈，土壤水分增加迅速。产生不同坡位间响应差异的原因是各点微地形差异导致集水面积不同。

Response of Soil Moisture to Precipitation in Different Slope Areas in Typical Hill Slope of the Three Gorges Mountain Area

Soil moisture is a key factor affecting the growth and development of vegetation on the surface, which also an essential part of the hydrological cycle of lithosphere-hydrosphere-biosphere-atmosphere. Its dynamic change can reflect the comprehensive information of surface hydrologic process. Based on the collected data from real-time monitoring systems of rainfall and soil moisture of upper, middle and lower slope positions in a typical basin of the Three Gorges Mountain area from May 2018 to May 2019 monitored by high-resolution TDR water probes and a small meteorological station, the variation of soil moisture and its response to precipitation were analyzed in different temporal scales. The results showed that: (1)In the monthly scale, the soil moisture content had a great seasonal difference. From May to July, it was the saving period (the average soil moisture content of 0~80 cm is 38.40%), and from August to October was the consumption period (the average soil moisture content is only 35.04%). (2) In the daily and hourly scales, different depths to precipitation were distinct significantly. The response of shallow layer (0~40 cm) to precipitation was faster (lag time <0.5 hours), and the trend of soil moisture change was similar to the process of rainfall; the response of 40~80 cm depth soil to rainfall had obvious hysteresis (lag time >0.5 hours), and in descending order of soil depths, the response luffing showed a decreasing trend and the retardation time was gradually increased. (3) Under different precipitation conditions, the soil moisture content showed markedly different variation. With different levels of rainfall changing from moderate rain to heavy downpour, the higher the rain intensity, the faster the growth rate of soil moisture, and the response time of soil water content increased synchronously. (4)The effect was different of soil moisture at different sites. The response curve of the upper slope site to precipitation was stable, but the middle and lower sites fluctuated greatly. It can be seen that different microtopography of different sites can change the response of soil moisture to precipitation.