Applicability of cosmic-ray neutron sensor for measuring soil moisture at the agricultural-pastoral ecotone in northwest China  

作　　者：Xingyan TAN Lanhui ZHANG Chansheng HE Yuzuo ZHU Zhibo HAN Xuliang LI 

机构地区：[1]Key Laboratory of West China's Environmental System(Ministry of Education),College of Earth and Environmental Sciences,Lanzhou University,Lanzhou 730000,China [2]Department of Geography,Western Michigan University,Kalamazoo,MI 49008,USA

出　　处：《Science China Earth Sciences》2020年第11期1730-1744,共15页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.41530752,41877148,41501016&91125010);the Scherer Endowment Fund of Department of Geography,Western Michigan University。

摘　　要：Accurate monitoring of soil moisture is crucial in hydrological and ecological studies.Cosmic-ray neutron sensors(CRNS)measure area-average soil moisture at field scale,filling a spatial scale gap between in-situ observations and remote sensing measurements.However,its applicability has not been assessed in the agricultural-pastoral ecotone,a data scarce semiarid and arid region in Northwest China(APENC).In this study,we calibrated and assessed the CRNS(the standard N0 method)estimates of soil moisture.Results show that Pearson correlation coefficient,RP,and the root mean square error(RMSE)between the CRNS soil moisture and the gravimetric soil moisture are 0.904 and less than 0.016 m3 m–3,respectively,indicating that the CRNS is able to estimate the area-average soil moisture well at our study site.Compared with the in-situ sensor network measurements(ECH2O sensors),the CRNS is more sensitive to the changes in moisture in its footprint,which overestimates and underestimates the soil moisture under precipitation and dry conditions,respectively.The three shape parameters a0,a1,a2 in the standard calibration equation(N0 method)are not well suited to the study area.The calibrated parameters improved the accuracy of the CRNS soil moisture estimates.Due to the lack of low gravimetric soil moisture data,performance of the calibrated N0 function is still poor in the extremely dry conditions.Moreover,aboveground biomass including vegetation biomass,canopy interception and widely developed biological soil crusts adds to the uncertainty of the CRNS soil moisture estimates.Such biomass impacts need to be taken into consideration to further improve the accuracy of soil moisture estimation by the CRNS in the data scarce areas such as agricultural-pastoral ecotone in Northwest China.

关 键 词：Soil moisture Cosmic-ray neutron sensor In-situ observations The agricultural-pastoral ecotone in Northwest China(APENC) 

分 类 号：S152.7[农业科学—土壤学]