Desertification and remote sensing

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Jilin City (red) in Jilin province (orange)

Study on Remote Sensing of the Degree of Land Desertification in the West of Ji Lin Province

Posted by Basic Science

See: Basic Science Paper

Land desertification that is an important content in the global change research is the one of most serious ecological problems all over the world. It is not only the threat to the survival of the human environment, but also the important factor to restrict the development of the global economy and affect Social stability. If we don’t take fundamental measures, the process of land desertificationwill not stop automatically, but will intensify to develop.We should start from the inherent attributes of the land desertification for learning to its type and extent. The comprehensive application and research of the Remote Sensing Data and Multiple Geo-information can be show attributes and inherent feature of the objects with a variety of ways and different scales. It’s very advantaged for Remote Sensing information to distinguish the object with their differentia of electromagnetic radiation features, but also it have some limitations. Practice has proved that we must relate Remote Sensing data to Multiple Geo-information that contain Geological data and Geochemical data with addition of the difficulty of geological work, and then we truly understand the nature of the objects and relation each other, also to be satisfied with the application of geological effects.

Heavenly Lake, Changbai Mountains in Jilin Province, China. September, 2003 -
Heavenly Lake, Changbai Mountains in Jilin Province, China. September, 2003 –

This article use the west of Ji Lin Province as study area. It make an estimate to desert land in working area as a whole with Remote Sensing Data (2007 ETM) and Geochemical Data (the results of 1:200000 soil geochemical survey in the west of Ji Lin Province).

Major work is as follows:(1) The classification of desert land.We obtain the information of land desertification in the west of Ji Lin Province by the ways of unsupervised classification and supervised classification, and then compare the results of both so that to separate accurately desert land and undesert land. The result indicates that the method of supervised classification is more accurate.(2) Enhance the information of Clay minerals among Remote Sensing Data. The special configuration of the objects fix on their Physical and Chemical character. We can analyse the inherent attributes after studying their spectrum character. Clay minerals which play an important role in extent of Land Desertification is an important part of soil composing. But vegetation and clay minerals have similar characteristic absorbable spectrum because the west of Ji Lin Province locate moist area. We should make use of Band Ratio and Principal Components to avoid vegetation information that would disturb clay minerals information in Remote Sensing Data as a whole hog so that we can analyse accurately the negative correlation between the extent of desertification and content of clay minerals.(3) Research methods of combination and classification of elements about Geochemical Data.We make use of Genealogy Cluster Analysis to combine and classify various elements among Geochemical data. The establishment of equal deep image of minerals content such as Quartz, Clay Minerals, Carbonate and so on could reflect directly the distribution of various minerals about Geochemical Data. It validates the seasonable of classification through contrasting Remote Sensing Image.(4) Complete the classification evaluation of desert land and find the variety rule between Remote Sensing spectrum and mineral content.The substance composing of different degrees of desert land is different. There is a close relationship between mineral content and spectral characteristics. We can found the association of both after establishing relevant model of Remote Sensing Spectral Profile image and equal deep image of minerals content.This article first study on Remote Sensing of the degree of land desertification to study area by the ways of combining geochemical data. It’s also the innovation point. It not only has done the evaluation of distribution and degree of desertification land, but also has realized semi-quantitative analysis of clay minerals to desertification land of different degrees. Reached the conclusions as follows:(1) It’s a negative correlation between the extent of desertification and content of clay minerals. The more serious desertification, the less content of clay minerals. There is may be a potential desertification to crops and grassland that contain less clay minerals.(2) The contain of Quartz is more than 42.115077% and the contain of clay minerals is less than 6.410923% to desert land which degree is serious; The contain of Quartz is 39.673305~42.115077% and the contain of clay minerals is 6.410923~8.557119% to desert land which degree is moderate; The contain of Quartz is 34.789760~39.673305% and the contain of clay minerals is 8.557119~10.414073% to desert land which degree is mild.

Author: Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.

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