Spectral pedology: A new perspective on evaluation of soils along pedogenetic alterations

There is still a lack between pedology and the knowledge of what is the perspective of spectroscopy in this science. Thus, it is important to describe how soil sensing can assist these pedologists on their studies. This work aims to show the perspective of proximal and remote sensing (VisNIR) on the evaluation of pedogenetic processes and parent material alterations along a toposequence and to estimate their mineralogical content. Eight soil classes from different taxonomic units were studied. Soil samples were submitted to physicochemical, mineralogical, and reflectance spectroscopy analyses. Reflectance data were acquired in laboratory conditions using a spectroradiometer (400–2500 nm). Hierarchical clustering analysis was applied to discriminate soil classes and their properties were assessed by multiple linear regression. Variations in spectral behavior in depth (absorption features and reflectance intensity) enabled the characterization of the soil classes. Reflectance data associated with clustering analysis allowed distinguishing the soils according to their weathering levels and parent materials. The clay mineral contents were estimated with a reasonable accuracy level. Soils along a toposequence can be detected by reflectance spectroscopy through variations in reflectance intensity and absorption features mainly in terms of the texture and mineralogical composition, respectively. Different weathering levels and, consequently, soil formation processes alter the soils along the toposequence which reflect on their spectral behavior, thus leading to a new site for soil visualization: the spectral pedology.