Assessment of Land Degradation Status and Its Impact in Arid and Semi-Arid Areas by Correlating Spectral and Principal Component Analysis Neo-Bands

Alfred Homère Ngandam Mfondoum,Joachim Etouna,Florine Gustave Noulaquape Deussieu,Buji Kindess Nongsi,Fabrice Armel Mvogo Moto

doi:10.23953/cloud.ijarsg.77

Abstract

This paper aimed to assess the status of land degradation in arid and semi-arid areas based on a correlation analysis between spectral and statistical neo-bands. The methodology uses vegetation and soil spectral indices as the second Modified Soil Adjusted Vegetation Index (MSAVI2), Normalized Difference Bare Soil Index (NDBSI), Texture Index (NDTeI), Crust Index (CI), Top Soil Grain Size Index (GSI), Normalized Difference Sand Dune Index (NDSDI) and the first Specific Principal Component of the red, near infrared, shortwave infrared bands stacking (SPC1 R-NIR-SWIR1-SWIR2 ). The vegetation is considered here as the main object of soil sub-surface. Thus after all the spectral and the statistic neo-bands are performed on Landsat8 OLI sensor image, a linear regression is generated to assess their correlation with MSAVI2. Based on the visual interpretation and the regression curves the results show that the determination coefficient R 2 and the P values all significant as less than 0.0001. Each neo-band is weighted with its R 2 to improve its contribution to the model and the synthesis image obtained enhances the land degradation sensing in six classes; these are respectively named as ‘‘severe’’ (3139 km 2 ), ‘‘high’’ (6763 km 2 ), ‘‘moderate’’ (8341 km 2 ), ‘‘low’’ (7454 km 2 ), ‘‘very low’’ (6947 km 2 ) and ‘‘close to nil’’ (5437 km 2 ). This last image is summed with population layer to produce a decision map helpful for further government decision. At the end the degradation image has given interesting results for the detection of land degradation comparatively to derivation and comparison of individual indices.

Highlights

Land degradation refers to a change in soil health condition that causes a reduction in the ecosystem's ability to provide goods and services for its beneficiaries (Barrow, 1991; Conacher and Sala, 1998; Biancalani, n.y.)
The results show six classes of land degradation on a nominal decreasing graduated scale that is arranged from the severe to the nil (Figure 10)
The first remark is that a visual and statistic close relation between SPC1R-NIR-SWIR1-SWIR2 and the degradation image; and this is confirmed by comparing the areas on each image class of degradation

Summary

Introduction

Land degradation refers to a change in soil health condition that causes a reduction in the ecosystem's ability to provide goods and services for its beneficiaries (Barrow, 1991; Conacher and Sala, 1998; Biancalani, n.y.). It is defined as the loss of soil production by either chemical or physical processes (Singer and Munns, 2002; Blaikie and Brookfield, 1987). From a holistic point of view and in its extreme form, land degradation is followed by a severe deterioration of vegetation cover and soil production capacity reduction takes the connotation of desertification, in those semi-dry arid or arid areas (Warren and Agnew, 1988; Begzsuren, 2007)

Objectives

Methods

Results

Conclusion