Restoration of Tamarix-Dominated Riparian Ecosystems in Western North America

In the latter part of the 19th century, species of the nonnative shrub tamarisk (also called saltcedar; for example, Tamarix ramosissima, T. chinensis) were introduced to the United States for use as ornamental plants and for erosion control.  By 1877, some naturalized populations had become established, and by the 1960s, tamarisk was present along most rivers in the semiarid and arid parts of the West and was quite abundant along downstream reaches of the major southwestern rivers such as the Colorado, Rio Grande, Gila, and Pecos.  The great abundance of tamarisk and Russian olive along western rivers has led resource managers to seek means of controlling it for various reasons, including 1) a desire to increase the flow of water in streams by losses otherwise due to evapotranspiration; 2) a desire to restore native riparian vegetation; and 3) a desire to improve wildlife habitat.  Changes in water use, wildlife habitat, and vegetation composition associated with Tamarix control are all dependent on the outcome of restoration or revegetation efforts.

Our research program combines multiple studies in an effort to develop a comprehensive understanding of restoration in the context of Tamarix control, so that land and water managers can better plan and execute projects and understand the broader context of their efforts.  Our work includes writing synthetic articles, and conducting experimental and field research on a broad range of restoration sites and approaches, including intensive revegetation of dry, saline sites, to streamflow management downstream of dams to promote native vegetation establishment over long river reaches.

Key findings to date include the publication of a state-of-the-science review article on tamarisk control, water use, wildlife habitat issues, and restoration.  A second synthesis article focused on planning and implementing restoration projects has been recently accepted for publication in the journal Restoration Ecology.  (http://www.fort.usgs.gov/staff/staffprofile.asp?StaffID=71)
Managed streamflow experiments have been conducted downstream of Alamo Dam on the Bill Williams River, Arizona over three years and the effects of these flows on the establishment and mortality of tamarisk versus native cottonwood and willow trees have been evaluated.  We have conducted field studies of reference riparian vegetation growing on dry and/or saline sites along multiple rivers in New Mexico.  Finally, we have conducted greenhouse trials with over 30 species of native species, testing for responses to different soil salinity levels and inoculation with mycorrhizal fungi.

Future research will include completion of greenhouse trials and field studies of reference sites.  In addition, these results are being used to inform and generate predictions for a factorial field restoration experiment, where we will examine the effects of different soil conditions, planting techniques, and mycorrhizae on planted species establishment.  Results of managed streamflow work will be published.  New research directions will likely include work on the ecology and management of other woody, invasive riparian plants such as Russian-olive.

	Contact: Pat Shafroth U.S.G.S. Fort Collins Science Center 2150 Centre Ave., Bldg. C Fort Collins, CO 80526 Phone: 970-226-9327 e-mail: shafrothp@usgs.gov Websites: http://www.fort.usgs.gov/staff/staffprofile.asp?StaffID=71 http://billwilliamsriver.org/