Hyperspectral degraded soil line index and soil degradation mapping in agriculture-pasture mixed area in Northern China

Land degradation is a major problem world-wide. Soil degradation is the core of land degradation. Soil degradation at regional scale is related to susceptibility to erosion, soil suitability, and soil characteristics. There is a pressing need for an objective measure on land degradation at regional scale. The study area is in Hengshan county in ShanXi province, where is in the agriculture-pasture mixed area in Northern China with complex physical geographical situation. On the basis of discussing the spectrum feature of soils and soil line parameters and analyzing the spectrum feature parameters responding to land degradation, the study is to develop and evaluate a spectral approach for soil features for degraded soil using Hyperion by exploiting the potential of its red bands and near infrared bands. This index called Degraded Soil Line Index (DSLI) is based on SAM classification approach and the soil line concept. The potential of Hyperion image data for mapping soil degradation through the application of this spectral index and the spectral angle mapping (SAM) approaches in semi-arid area of North China will also be compared and investigated. It was indicated that results showed that both the SAM and DSLI approaches have the ability to map soil degradation and clearly show the degraded soil class. It also showed the difference between the DSLI and SAM methods is significant, and showed the interest and the contribution of the DSLI index in the study of land degradation. The validation of the results obtained with the DSLI index and soil samples served as an additional tool showed that that the map of distribution of land degradation types using DSLI method depends on the physico-chemical characteristics of the different classes. It indicated that the highly degraded soils are associated with low soil organic matter and available phosphorus, high slope gradient and sand particle percentage and total phosphorus.