基于环境变量和机器学习的土壤水分反演模型研究
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内蒙古自治区科技计划项目(201802123)和国家自然科学基金项目(52069021、51839006)


Soil Moisture Inversion Based on Environmental Variables and Machine Learning
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    摘要:

    为利用多源数据构建毛乌素沙地腹部土壤含水率建模指示因子,通过微波后向散射系数、地表温度、缨帽变换要素、波段反射率、干旱指数和地形要素等17个变量为建模因子,分别以偏最小二乘(Partial least squares regression,PLSR)、极限学习机(Extreme learning machine,ELM)和随机森林(Random forest,RF)3种方法构建土壤含水率反演模型,对模型进行验证和对比,并对研究区的土壤水分分布进行制图。结果表明:温度植被干旱指数是土壤水分空间变异性的最重要的预测因子(决定系数为0.64),其次是地表温度(0.6)、σVV(0.38)、植被指数(0.38)、波段7反射率(0.35)、σVH(0.32)、波段6反射率(0.3)和反照率(0.26)。相比于未筛选变量所构建的模型,利用最优子集筛选(Best subset selection,BSS)变量所构建的模型精度均有所提升。其中PLSR在处理共线性方面表现最优,ELM回归模型最稳定。RF模型具有最高的精确度,4月,决定系数为0.74,均方根误差为8.85%,平均绝对误差为7.86%;8月,决定系数为0.75,均方根误差为8.86%,平均绝对误差为7.41%。不同方法反演的土壤水分分布趋势没有显著差异,高土壤含水率出现在研究区的北部和东南部,中北部平坦地区的土壤含水率较低。利用光谱指数、环境因子和地形数据构建的多因子、多指数综合模型能较高精度地反演毛乌素沙地腹部表层土壤水分,对研究该地区土地荒漠化和生态环境治理具有参考价值。

    Abstract:

    In order to construct the modeling indicators of soil moisture content in the Mu Us sandy land using multi-source data, totally 17 variables, including microwave backscattering coefficient, surface temperature, silk hat transform factor, band reflectance, drought index and topographic factor were used as modeling factors. PLSR, extreme learning machine (ELM) and random forest (RF) were used to construct soil water content inversion models, verify and compare the models, and map soil water distribution in the study area. The results showed that the determination coefficient of temperature vegetation drought index was 0.64, followed by land surface temperature (0.6),σVV(0.38), vegetation index (0.38), band 7 reflectance (0.35),σVH(0.32), band 6 reflectance (0.3) and Albedo (0.26). Compared with the model constructed with unscreened variables, the accuracy of the model constructed with best subset selection (BSS) variables was improved. PLSR had the best performance in collinearity, and ELM regression model was the most stable. RF model had the highest accuracy, with a determination coefficient of 0.74, root mean square error of 8.85% and mean absolute error of 7.86% in April. In August, the determination coefficient was 0.75, the root mean square error was 8.86%, and the mean absolute error was 7.41%. There was no significant difference in soil water distribution trend between different methods. The highest soil water content occurred in the north and southeast of the study area, and the lower soil water content occurred in the flat area in the central and northern part of the study area. Using spectral index, environmental factor and topographic data, the multi-factor and multi-index comprehensive model can accurately retrieve the surface soil moisture in the Mu Us sandy land, which had reference value for the study of land desertification and ecological environment control in this area.

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王思楠,李瑞平,吴英杰,赵水霞,王秀青.基于环境变量和机器学习的土壤水分反演模型研究[J].农业机械学报,2022,53(5):332-341. WANG Sinan, LI Ruiping, WU Yingjie, ZHAO Shuixia, WANG Xiuqing. Soil Moisture Inversion Based on Environmental Variables and Machine Learning[J]. Transactions of the Chinese Society for Agricultural Machinery,2022,53(5):332-341.

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  • 收稿日期:2021-05-24
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  • 在线发布日期: 2022-05-10
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