Saltcedar (Tamarix pentandra Pall.) and Russian olive (Elaeagnus angustifolia L.) invade moist pastures and rangeland and cause serious forage-production and soil-water losses. Our objective was to develop criteria for classifying sites relative to the likelihood of infestation by saltcedar and Russian olive, based on comparisons of soil and vegetation characteristics of infested and adjacent uninfested sites. Discriminant analyses indicated that Russian olive occurs on soils with low to medium concentrations of soluble salts (100–3500 ppm), whereas saltcedar occurs on soils with much higher soluble salt concentrations (700–15000 ppm). Characteristics of the herbaceous vegetation on sites infested with saltcedar or Russian olive differed distinctly from each other and from adjacent, uninfested sites. Frequency of occurrence of certain herbaceous understory species provided the most accurate basis for discrimination of infested and uninfested areas. Discriminant analysis may be of value in the development of infestation-proneness indices.
