Data from two long traverses in the chenopod rangelands of arid South Australia were analysed by the moving block association analysis technique to reveal the different plant communities. Discriminant analysis showed that the communities along each traverse had distinctive Landsat MSS reflectivity spectra. A method of constructing a quantitative key to identify community types by their Landsat reflectivities is described. However, the key for one traverse was defective when applied to the second traverse, demonstrating a broad-scale breakdown of reflectance relations. Implications for future work are discussed.