基于连续统去除法的土壤盐分含量反演研究

INVERSION OF SOIL SALT CONTENT BASED ON CONTINUUM-REMOVAL METHOD

通过对新疆维吾尔自治区温宿县、和田县、拜城县191个土样的原始反射率进行连续统去除及连续统去除的一阶微分处理,分析了盐分的高光谱吸收特征及敏感波段,并建立了盐分含量的多种高光谱定量反演模型。结果表明,在400~2 400 nm波段,土壤反射率与盐分含量之间无明显规律。640~700 nm波段的连续统去除数据与含盐量呈极显著负相关,而710~780 nm波段呈极显著正相关。原始反射率经连续统去除处理后,可明显提高反演模型的预测性能。基于盐分光谱指数和吸收特征参数构建的反演模型的稳定性及预测能力不如连续统去除、连续统去除一阶微分的400~2 400 nm或敏感波段的偏最小二乘回归(PLSR)模型。所有模型中,仅有以400~2 400 nm和640~700 nm连续统去除数据所建模型的相对分析误差(RPD)达2.5以上,分别为2.62和2.52,且二者其余各项评价指标差异不大。以640~700 nm波段连续统去除数据构建的PLSR模型对南疆水稻土盐分含量具有很好的反演效果。

A total of 191 soil samples were collected from Wensu,Hetian and Baicheng counties for analysis of origi- nal reflectanees,which were then subjected to continuum removal and first derivative of continuum removal for analysis of hyperspectral absorption characteristics and sensitive bands of salts. On such a basis, a number of hyperspectral inversion models for quantification of soil sah contents （S,） were established. Results show that there was no obvious relationshipbetween soil reflectance and S, in 400 - 2 d00 nm bands, and an apparent negative relationship between the data of contin- uum removal and S, in 640 -700 nm bands and a positive one in 710 -780 nm bands. Prediction accuracies of the inver- sion models were improved significantly after the original reflectances underwent continuum removal. The inversion models established on spectral indices and spectral absorption features were inferior in stability and prediction accuracy to the PLSR models based on spectral reflectance in 400 - 2 400 nm bands or sensitive bands after continuum removed （CR） and first derivative of continuum removal （FDCR）. Among all the models, the inversion models between S, and FDCR were higher in determination coefficient and lower in root mean square error than the inversion models between S, and CR. But the former was lower than the latter in prediction accuracy. Among all the inversion models, only the ones based on full spectrum and 640 ~ 700 nm continuum removal were higher than 2.5 in RPD, reaching 2.62 and 2.52, respectively and moreover,little difference was found between the two in all the other evaluation indices. The PLSR inversion model based on the continuum-removal data of the 640 ~ 700 nm bands is the most effective one in predicting S^of paddy soils in South- ern Xinjiang Uygur Autonomous Region of China.