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土壤表层水分是固沙植被生长的主要水分来源,其时空变化格局决定了固沙植被的稳定性和演替方向。整合被动微波和光学数据的时空分辨率优势建立模型、反演土壤表层水分,可为不同固定程度沙地固沙植被稳定性评价提供科学依据。以腾格里沙漠东南缘为研究区,选取2003—2011年生长季(5—9月)AMSR-E土壤水分产品与MODIS数据,利用归一化植被指数NDVI、地表温度Ts,采用多元回归的方法,将空间分辨率为0.25°的AMSRE土壤水分数据降尺度为每月的1km平均表层土壤水分的时间序列数据,结合沙丘类型数据,分析了不同沙丘类型下土壤水分的时空异质性。结果表明:流动沙地的土壤水分空间分布与整个区域的差异性高于半固定沙地和固定沙地,而在极端干旱年份,研究区的整体分异不大,但同一类型间,固定沙丘空间差异明显高于半固定沙丘和固定沙丘;3种沙地类型表层土壤平均含水量在不同月份具有相似的变化规律,即土壤含水量5—9月呈抛物线形状,先下降后上升,7月达到最低,从同一月份不同沙地类型看,研究区表层土壤水分含量依次是固定沙地>半固定沙地>流动沙地;年际土壤水分在流动沙地和半固定沙地随降雨的变化而变化,而固定沙地基本不变。
Soil surface moisture is the main source of water for the growth of sand-fixing vegetation, and its temporal and spatial pattern determines the stability and succession direction of sand-fixing vegetation. Integrating the spatio-temporal resolution advantages of passive microwave and optical data to establish the model and invert the surface water can provide a scientific basis for evaluating the stability of sand-fixing vegetation on different fixed levels. Taking the southeastern margin of the Tengger Desert as the research area, AMSR-E soil moisture products and MODIS data of growing season (May-September) from 2003 to 2011 were selected. Using normalized NDVI, surface temperature Ts, Method, the scale of AMSRE soil moisture data with a spatial resolution of 0.25 ° is downscaled to the monthly time series data of 1 km average surface soil moisture, and the temporal and spatial heterogeneities of soil moisture under different types of sand dunes are analyzed in combination with the data of sand dune types. The results show that the spatial distribution of soil moisture in mobile sandy land is higher than that in semi-fixed sandy land and fixed sandy land. However, in the extremely dry years, there is not much difference in the whole study area, but in the same type, fixed sand dunes The spatial variability was obviously higher than semi-fixed sand dunes and fixed sand dunes. The average soil water content of topsoil with three types of sandy land had similar variation pattern in different months, that is, the soil water content was parabolic from May to September, and then decreased first and then increased. July Reaching the minimum. According to the types of different sandy land in the same month, the surface soil moisture content in the study area was in the order of fixed sandy land> semi-fixed sandy land> mobile sandy land. The interannual soil moisture fluctuated with the rainfall in the mobile sandy land and the semi-fixed sandy land And change, while the fixed sand basically unchanged.