CORRELATIONS BETWEEN DEM-DERIVED TOPOGRAPHIC INDEXES AND REMOTELY-SENSED VEGETATION COVER IN RANGELANDS

The paper describes an attempt to relate patterns of vegetation cover with topography and a set of biological and grazing intensity variable s in a mountain and piedmont area of arid central Australia. Vegetatio n cover, as measured by an index based on data from the Landsat satell ite, can also be used as an erosion/deposition surrogate so the result s have implications for distributed erosion models. A simple, analytic ally based erosion model derived from the continuity equation does not reproduce observed patterns of vegetation cover, and neither do vario us topographically based moisture indices. A regression approach shows that patterns of vegetation cover are related to topography but the m ost important predictors are biological ones, with percentage of bare ground upslope being the strongest. Tests with variable drainage area show that relationships between cover and topography, bare area upslop e and grazing effects change systematically with basin size and that s cale effects are present. Distributed erosion models are not yet capab le of handling biological processes very well, yet these processes mus t be incorporated if erosion prediction is to be successful.