Influence of rock-soil spectral variation on the assessment of green biomass

Abstract Vegetation indices can be adversely influenced by variation in rock and soil spectral characteristics. When rocks and soils yield different vegetation index values, this is misinterpreted as changes in green biomass. This spectral influence is present to some extent in all vegetation indices. Secondly, variations in rock-soil brightness have a strong influence on ratio-based vegetation indices. Variations in rock-soil brightness have the same effect on all ratio-based vegetation indices: Vegetation is overestimated on dark backgrounds relative to bright backgrounds. Overall, it is concluded that the perpendicular vegetation index is the best available vegetation index to use in multispectral imagery of arid and semiarid regions where there is wide variation in rock and soil spectral characteristics.