A Comparative Study for Performance of Five Landsat-based Vegetation Indices: Their Relations to Some Ecological and Terrain Variables

Abstract

Spectral vegetation indices and their relations to some ecological and terrain variables in the Iraqi Kurdistan Region (IKR) are the main objective of this study. A mosaic of two Landsat-7 ETM+ images was utilized to produce five spectral vegetation indices, and the Terra ASTER Digital Elevation Model (DEM) dataset was employed. The Normalized Difference Vegetation Index (NDVI), Soil Adjusted Vegetation Index (SAVI), Optimized Soil Adjusted Vegetation Index (OSAVI), Tasseled Cap Greenness, and Land Surface Temperature (LST) were utilized for this study. The results of the current study revealed that MSAVI2 is more reliable and accurate in depicting the vegetation presence in the IKR, which occupied 34.7% of the total study area in 2014. In terms of terrain variables, all vegetation indices responded to variation in aspect ratio. It was found that the densest vegetation exists between 180 and 350°. Mainly, in the South (157.5°-202.5°), Southwest (202.5°-247.5°), West (247.5°-292.5°), Northwest (292.5°-337.5°), and North (337.5°-360°). In contrast, from the aspect ratio point of view, vegetation cover growth was at its maximum status on the shaded side of the mountains, more than on the sunny side. Additionally, the adequate slope for vegetation growth in the mountainous lands is 9–17%. Statistically, the LST appeared to have negative relationships with vegetation indices and elevation.