毛乌素沙地固定沙丘表层土壤水分时间稳定性特征

Temporal Stability Characteristics of Surface Soil Moisture of Fixed Dunes in the Mu Us Sandy Land

土壤水分在干旱半干旱地区的水文过程和植被恢复中具有重要的决定性作用,探究毛乌素沙地固定沙丘表层土壤水分的时间稳定性特征,对该地区水资源调控和生态环境改善具有重要意义。在毛乌素沙地东南缘选取固定沙丘迎风坡、背风坡和坡顶进行网格化布点,于2019年7月至10月使用土壤温湿度记录仪(TMS)对表层(0~5 cm)土壤含水量进行测定,分析表层土壤水分的时空变异性与时间稳定性特征。结果表明:研究期内表层土壤含水量的均值为21.00%,时空变化总体上具有中等变异性特征。表层土壤含水量的空间模式在观测时间上具有较弱的相似性,各日期对之间均具有较低的相关系数。土壤含水量的相对差分平均值(MRD)在-17.24%~18.80%之间,相对差分标准差(SDRD)和时间稳定性指数(ITS)的平均值分别为12.70%和14.20%,表层土壤含水量具有较好的时间稳定性。土壤含水量高于平均值的观测点,SDRD与ITS均较低,较高土壤含水量观测点的时间稳定性优于较低土壤含水量观测点。通过土壤含水量的时间稳定性特征分析判定,观测点77可以较好的代表研究区内表层土壤含水量的平均水平(决定系数为0.8769)。

Soil moisture plays an important role in the hydrological process and vegetation restoration in arid and semi-arid regions.Exploring the temporal stability characteristics of soil moisture in the fixed dunes of the Mu Us Sandy Land is of great significance to the regulation of water resources and the improvement of the ecological environment in this area.The windward,leeward and slope tops of fixed dunes on the southeastern edge of the Mu Us Sandy Land were selected for grid layout.The surface(0~5 cm)soil water content was measured by soil temperature and humidity recorder(TMS)from July to October 2019.Then,the spatial variability and temporal stability characteristics of the surface soil water was analyzed.The results showed that during the study period the average surface soil water content was 21.00%.Temporal and spatial changes were generally characterized by moderate variability.The spatial model of surface soil water content had weak similarity in observation time,and each date pair had a low correlation coefficient.The average relative difference(MRD)of soil water content was between-17.24%and 18.80%,and the average relative difference standard deviation(SDRD)and time stability index(ITS)were 12.70%and 14.20%,respectively.The surface soil water content had good time stability.The observation points with higher soil water content had lower SDRD and ITS,and the time stability of observation points with higher soil water content was better than that of observation points with lower soil water content.Based on the analysis of the time stability characteristics of soil water content,the 77 th observation point could better represent the average level of surface soil water content in the study area(coefficient of determination was0.8769).