Temporal stability of soil moisture in various semi-arid steppe ecosystems and its application in remote sensing
Temporal stability of soil moisture in various semi-arid steppe ecosystems and its application in remote sensing
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DOI：
10.1016/j.jhydrol.2008.06.016
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发表时间：
2008-09
影响因子：
6.4
通讯作者：
K. Schneider;J. Huisman;L. Breuer;Y. Zhao;H. Frede
中科院分区：
文献类型：
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作者：
K. Schneider;J. Huisman;L. Breuer;Y. Zhao;H. Frede
土壤水分监测在各种尺度的水文研究中经常是必要的。挑战之一是以最少的劳动力和成本确定大面积的平均土壤湿度。本研究的目的是测试样本位置的时间持久性，以减少所需的样本数量，使可靠的估计在表层土壤中的平均含水量。在2004-2006年的植被期，收集了四个试验点的土壤水分数据。实验地点位于中国北方的草原环境中，其特征在于不同的放牧管理导致植被覆盖的差异。每个站点共100个采样点进行了排名，就其差异，实地平均土壤水分使用的时间稳定性的概念。我们测试了：（a）存在代表性样本位置，可将田间平均土壤湿度预测到可接受的程度，（B）这些位置在单个植被期之后是时间稳定的。时间稳定的位置，从平均田间土壤水分和低标准差的低偏差确定为每个网站。虽然一些点的时间稳定性特征在不同年份之间有所不同，但所选的点适合于预测多年的平均土壤水分。在田间尺度上，利用斯皮尔曼等级相关分析了模式的时间稳定性和持续性。分析表明，持续性取决于放牧管理和相关的植物覆盖。它的结论是，时间稳定性的概念提供了有用的信息，水文或遥感模型的验证，或土壤水分信息的升级到更大的尺度。对从地面实况数据和遥感数据得出的土壤湿度测量结果进行的初步比较表明，在某些情况下，数据匹配良好，但在其他情况下，空间范围的巨大差异促成了差异。
Monitoring soil moisture is often necessary in hydrological studies on various scales. One of the challenges is to determine the mean soil moisture of large areas with minimum labour and costs. The aim of this study is to test temporal persistence of sample locations to decrease the number of samples required to make reliable estimates of mean moisture content in the top soil. Soil moisture data on four experimental sites were collected during the vegetation period in 2004–2006. The experimental sites are located in a steppe environment in northern China, and are characterised by different grazing management which causes differences in vegetation cover. A total of 100 sampling points per site were ranked with respect to their difference to field mean soil moisture using the time-stability concept. We tested whether: (a) representative sample locations exist that predict field mean soil moisture to an acceptable degree, and (b) these locations are time-stable beyond a single vegetation period. Time-stable locations with a low deviation from mean field soil moisture and low standard deviation were identified for each site. Although the time-stability characteristics of some points varied between years, the selected points were appropriate to predict mean soil moisture of the sites for multiple years. On the field scale, time-stability and the persistence of patterns were analysed by the use of a Spearman rank correlation. The analysis showed that persistence depended on grazing management and the related plant cover. It is concluded that the time-stability concept provides useful information for the validation of hydrological or remote sensing models, or for the upscaling of soil moisture information to larger scales. A preliminary comparison of soil moisture measurements derived from ground-truth and remote sensing data showed that the data matched well in some cases, but that the considerable difference in spatial extent promotes differences in other cases.