Assessment of Landsat Multispectral Scanner spectral indexes for monitoring arid rangeland

The utility of Landsat Multispectral Scanner (MSS) spectral indexes for monitoring arid range land was tested in south-central New Mexico by determining correlations between spectral indexes and vegetation parameters. Also, spectral index change from 1976 to 1980 was calculated from retrospective MSS data and compared with qualitative ground truth to determine if vegetation change could be detected using spectral indexes. MSS band 5, albedo, and the Kauth-Thomas Brightness component were correlated with total vegetation cover, with maximum r = −0.844. Dry season green vegetation indexes were the best estimators of combined cover of mesquite plus snakeweed, two shrub invaders of degraded grassland. The dry season-wet season difference in green vegetation indexes gave rough estimates of grass cover. In retrospective monitoring, cover change in response to shrub control and changes in grating intensity and rainfall was detected by change in brightness indexes. Brightness index change consistently differentiated between cover increase and decrease, but Index change was apparently offset from true cover change. The offset was attributed, at least in part, to failure of the methods used to standardize MSS scenes for differences in sensor response. In contrast to brightness indexes, green vegetation indexes failed to consistently differentiate between cover increase and decrease.