High resolution infrared digital camera imagery was used to determine the extent of the invasion of hill slopes by Pteronia incana , an unpalatable dwarf shrub. On the basis of a priori field surveys, the imagery was classified into different degrees of the invasion and other surface cover types using Idrisi32 GIS. The imagery was noted to have limited constraints, as evidenced by the high level of classification accuracy. A range of vegetation indices was examined to identify one that best characterized the spatial distribution of the shrub and its degree of invasion. Distinct spectral separability of the invader from other surface cover types was achieved by means of the perpendicular vegetation index (PVI), as opposed to the ratio based vegetation indices (NDVI, SAVI, and MSAVI). Depending on the local geographical characteristics, the PVI could be particularly suited for the identification of perennial shrubs with characteristics similar to P. incana , which are usually interspersed with considerable bare zones.
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Document Type: Research Article
Department of Geosciences, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
ARC‐Range & Forage Institute, Grahamstown, South Africa
Catchment Research Group, Rhodes University, Grahamstown, South Africa
Publication date: 2006-07-10
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