Soil line concept and its use for soil mapping and monitoring (overview)

The soil line concept was proposed in 1977. Since then, it has been widely used for satellite monitoring of vegetation, land cover and soils. A critical review of scientific publications on the use of the soil line concept in remote sensing is carried out. The review is based on the analysis of publications indexed in the scientific databases RISC and Scopus. The search was performed using the terms “soil line” and “soil AND line AND spectral AND reflection” in the titles of articles, in keywords and in abstracts of publications for all available years. The following types of publications were included in the sample: articles in scientific journals, review articles, book chapters, and articles in conference proceedings. A total of 104 articles were analyzed. It was found that the soil line concept is most widely used in the creation of vegetation spectral indices for monitoring vegetation cover. It is also used to assess the state of land cover and in soil monitoring. The leader in the number of publications in this field of knowledge are specialists from China. Together with specialists from the USA and Russia, they have published about half of all publications. By affiliation of the first author, publications of the Chinese Academy of Sciences and the V.V. Dokuchaev Soil Science Institute (Russia) prevail. The concept of soil line is promising for mapping and monitoring of separate groups of soil properties, less often - separate soil properties by the character of their open surface image. For its wider use, additional studies of the influence of individual properties of different soils on their spetcral reflectivity in the visible and NIR spectral ranges are needed. The hypothesis about the possibility of satellite mapping and monitoring of soil types (or other classification divisions) based on the soil line concept requires extensive experimental confirmation.