Riparian lands are especially integral and fragile aspects of western ecosystems due to their role in maintaining water quality and quantity, providing ground water recharge, controlling erosion, and dissipating stream energy during flood events (Birken and Cooper 2006). Unfortunately, many of these water systems and associated riparian lands have been severely degraded over the past 150 years by anthropogenic activities (damming, road building, irrigation, etc.) and invasive plant species, resulting in reduced water quality, altered river regimes and reduced ecological systems and habitats (Di Tomaso 1998 and Glenn and Nagler 2005).
Tamarisk (Tamarix spp.) and Russian olive (Elaeagnus angustifolia) are invasive woody species of particular interest to many land managers. For a detail discussion on both of these species please see the Colorado River Basin Tamarisk and Russian Olive Assessment.
Tamarisk is a deciduous shrub or small tree that was introduced to the western U.S. in the early nineteenth century for use as an ornamental, in windbreaks, and for erosion control. The exact date of introduction is unknown; however, it is generally understood that tamarisk became a problem in western riparian zones in the mid 1900s (Robinson 1965, Howe and Knopf 1991).
Originating in central Asia and the Mediterranean, tamarisk is a facultative phreatophyte with an extensive root system well suited to the hot, arid climates and alkaline soils common in the western U.S. These adaptations have allowed it to effectively exploit many of the degraded conditions in southwestern river systems today (e.g., interrupted flow regimes, reduced flooding, increased fire) (Glenn and Nagler 2005).
Please see the Colorado River Basin Tamarisk and Russian Olive Assessment for more information on:
Tamarisk cover estimates range from 1 to 1.5 million acres of land in the western U.S. and may be as high as 2 million acres (Zimmerman 1997).
In the presence of established native vegetation or sprouts, tamarisk seedlings are not strongly competitive. (Sher, Marshall & Gilbert, 2000; Sher, Marshall & Taylor, 2002; Sher & Marshall, 2003).
Tamarisk can increase fire frequency and intensity, drought (Graf 1978), and salinity (Taylor et al. 1999) of a site.
Tamarisk populations develop in dense thickets, with as many as 3,000 plants per acre that can prevent the establishment of native vegetation (e.g., cottonwoods (Populus spp), willows (Salix spp), sage, grasses, and forbs) (Carpenter 1998, McDaniel et al. 2004).
Dense tamarisk stands on stream banks accumulate sediment in their thick root systems gradually narrowing stream channels and increasing flooding. These changes in stream morphology can impact critical habitat for endangered fish (Carpenter 1998, McDaniel et al. 2004).
Dense stands affect agricultural production by invading rangeland, reducing forage, and preventing access to surface water. The non-beneficial use of water also affects irrigation practices (Carpenter 1998, McDaniel et al. 2004).
Aesthetic values of the stream corridor are degraded, and access to streams for recreation (e.g., boating, fishing, hunting, bird watching) is lost (Carpenter 1998, McDaniel et al. 2004).
Birken, A.S. and D.J Cooper. 2006. Processes of Tamarix invasion and floodplain development along the lower Green River, Utah. Ecological Applications 16(3):1103-1120.
Carpenter, A. 1998. Element Stewardship Abstract for Tamarix ramosissima Lebedour, Tamarix pentandra Pallas, Tamarix chinensis Loureiro, and Tamarix parviflora De Candolle. The Nature Conservancy, Arlington, Virginia.
Di Thomaso, J.M. 1998. Impact, Biology, and Ecology of Saltcedar (Tamarix spp.) in the Southwestern United States. Weed Technology 12:326-336.
Glenn, E.P. and P.L. Nagler. 2005 Comparative ecophysiology of Tamarix ramosissima and native trees in western U.S. riparian zones. Journal of Arid Environments 61:419-446.
Graf, W.L. 1978. Fluvial adjustments to the spread of tamarisk in the Colorado Plateau region. Geological Society of America Bulletin 89:1491-1501.
Howe, W.H. and F.L. Knopf. 1991. On the imminent decline of Rio Grande cottonwoods in central New Mexico. The Southwestern Naturalist 36:218-224.
McDaniel, K.C., J.M. DiTomaso and C.A. Duncan. 2004. Tamarisk or Saltcedar (Tamarix spp.) Galley proof for Allen Press.
Robinson, T.W. 1965. Introduction, spread, and aerial extent of salt cedar (Tamarix) in the western states. Geological survey professional paper 491-A. United States Government Printing Office, Washington.
Sher, A.A. and D.L. Marshall. 2003. Competition between native Populus deltoides and invasive Tamarix ramosissima and the implications of reestablishing flooding disturbance. Conservation Biology 14:1744-1754.
Sher, A.A., D.L. Marshall, and S.A. Gilbert. 2000. Competition between native Populus deltoides and invasive Tamarix ramosissima and the implications for reestablishing flooding disturbance. Conservation Biology 14:1744.
Sher, A.A., Marshall, D.L., and Taylor, J.P. 2002. Establishment patterns of native Populus and Salix in the presence of invasive, non-native Tamarix. Ecological Applications 12: 760-772.
Taylor, J.P., D.B. Wester, and L.M. Smith. 1999. Soil disturbance, flood management, and riparian woody plant establishment in the Rio Grande floodplain. Wetlands 19:372-382.
Zimmerman, J. 1997. Ecology and Distribution of Tamarix chinensis Lour and T. parviflora D.C., Tamariccea. Southwest Exotic Plant Mapping Program, U.S. Geological Survey.