[Effects of different spectra types on the accuracy and correction of soil salt content inversion in Yinchuan Plain, China].

Soil salinization is one of key drivers for the degradation of soil quality and yield in arable land. To accurately and quickly evaluate soil salt content in Yinchuan Plain, field and indoor hyperspectral data were processed with first order differential (FDR) transformation, then the feature bands were identified by stepwise regression (SR). Partial least squares regression (PLSR) and support vector machines (SVM) were used to build models, which were verified to figure out the optimal hyperspectral type for the study area. Moreover, segmented and global corrections were performed to process poor hyperspectral, aiming to improve the accuracy of soil salt content inversion. The results showed that the accuracy of soil salt content inversion model based on field hyperspectral data was 58.9% higher than that of the indoor hyperspectral data. The accuracy of the inversion was improved through the segmented and global correction of the indoor hyperspectral. We found that the segmented correction is more accurate for the PLSR model (Rc2=0.790, Rp2=0.633, RPD=1.64) and the global correction is more accurate for the SVM model (Rc2=0.927, Rp2=0.947, RPD=3.87). The SVM models' inversion accuracy was higher than that of PLSR, with the field hyperspectral model fitted the best, followed by the indoor hyperspectral processed with the global correction and the indoor hyperspectral processed with the segmented correction, while the indoor hyperspectral the worst. Our results suggest that field hyperspectral data could contribute to the quantitative inversion of soil salt content in Yinchuan Plain. The corrected indoor hyperspectral could significantly enhance the inversion accuracy of soil salt content, which could guarantee food security and ecological quality development.土壤盐渍化是导致土壤质量下降、耕地减产的重要因素之一。为准确快速评价银川平原土壤含盐量,本研究对野外高光谱数据和室内高光谱数据进行一阶微分(FDR)变换,逐步回归(SR)筛选特征波段,利用偏最小二乘回归(PLSR)与支持向量机(SVM)进行建模,明确适用于本地区土壤含盐量准确反演的光谱类型,并对较差光谱类型进行分段校正与全局校正,尝试提高土壤含盐量反演精度。结果表明: 基于野外光谱的土壤含盐量反演模型精度比室内光谱平均高58.9%;对室内光谱进行分段校正、全局校正后反演精度均有提高,其中,PLSR以分段校正精度更高,建模决定系数(Rc2)、验证决定系数(Rp2)和相对分析误差(RPD)分别为0.790、0.633和1.64,而SVM以全局校正精度更高,Rc2、Rp2和RPD分别为0.927、0.947和3.87;SVM模型的反演精度高于PLSR,其中,野外光谱建模效果最佳,室内全局校正光谱与室内分段校正光谱次之,室内光谱最差。因此,野外高光谱可实现对银川平原土壤表层含盐量的定量反演,经校正的室内光谱对土壤含盐量反演精度显著提升,均可为粮食安全与生态环境高质量发展提供保障。.