关键词:土壤线 高光谱 反射率 植被指数 定量遥感 光谱反射率 土壤线 影响因素分析 Hyperspectral Reflectance Soil Laboratory Based Analysis Influence Factors 计算方法 数显 相关系 背景 曲线形状 大小 粗糙度 土壤水分 秸秆覆盖 矿物组成 有机质
In order to estmi ate vegetation index precisely, the soil lines of different soil types must be identified.However, it is difficult to obtain the soil line parameters, because there aremany influencing factors. With the laboratory soilhyperspectral reflectance studied, the main factors influencing the soil line were determined. The laboratory soil hyperspectral reflectance was used to calculate soil line parameters, which were introduced to compute the vegetation indices related to soil line. The correlation between the indices and soybean chlorophyll a or leaf area index (LAI) was comparedwith thatbetween normalized difference vegetation index (NDVI) and chlorophyll a orLAI, then the feasibility of the soil line computingmethodwas analyzed.The resultswere as follows: themain factors affecting soil line parameterswere not the bandwidth but the soil class,the latitude, organicmatter, mineral composition, and straw residues. Soil classes, with differentphysical and chemical properties, show significant differences in spectral characteristics, especially the reflectance shape at red and infrared bands. The slope ofsoil linewith low soil albedowasnotalways smaller than thatwith higher soil albedo. What’smore,latitude also influenced the soil line parameters because of the regular distribution of soil parentmaterial and other soil properties. The effectoforganicmatter on soil reflectance in visible and infrared bands(620—810nm) ismuch stronger than other spectral regions, the reflectance curve at visible and infrared domain is concave, so the slope of soil line increaseswith organicmatter content. What’smore the effect of organicmatter on soil line parametersmay be stronger than soil class.Based on soil line, the soilvegetation indicespartly elmi inate the soilbackground noises, and the correlation between the indices and soybean chlorophyll a orLAI ismore significant than thatbetweenNDVI and chlorophyll a orLAI, which indicates that the soil line parameter derivingmethod is feasible and appropriate for the vegetation indices based on soil line.In order to enhance themonitoring precision ofvegetation indices, the soil line parameters should be calculated based on the spatial difference of the main factors influencing the parameters. However, the results of the study is based on ground crop spectral reflectance data and obtained in the laboratory, as a result, the influence of atmosphere is not completely considered. Therefore, when the result is used in remote sensing mi age data, the influence of atmosphere on\nsoil and crop reflectancemustbe analyzed.