The Ecological role of tamarisk and Russian olive: Interaction with native species and other exotic plants.

John H. Brock, Environmental Resources Program, Arizona State University, Tempe, AZ

Russian olive and tamarisk (saltcedar) are competitive with native woody species, especially those that are under some type of stress. Both species produce large numbers of seedlings and tend to coexist in mixed stands. Once tamarisk and Russian olive occupy a site, there is a decrease in the suitability of the site for native riparian tree species and their associated vegetation. Man has been the major agent in the spread of these alien invasive species. Sixteen of the 17 western states still subsidize the planting of Russian olive as an ornamental or conservation plant. Impacts of tamarisk/Russian olive include: (1) dewatering of sites, (2) crowding out native species causing a loss of biodiversity and(3) providing less habitat values compared to functioning riparian areas with native species. Positive aspects of their presence are (1) provide some habitat where nothing else is growing, (2) provide some wildlife food (Russian olive), (3) provide stream bed stabilization, and (4) nesting sites for some threatened and endangered species. Overall, the negative aspects of tamarisk and Russian olive outweigh the positive aspects.

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