ABSTRACT
Invasive, non-indigenous plants are increasingly serious resource concerns in wetlands and riparian ecosystems because of their potential to displace native plant species, degrade habitat quality for wildlife, and alter physical properties of ecosystems, including the potential to retain water resources. One of the most serious plant invaders in western North America is tamarisk or saltcedar (Tamarix spp.), a fast-growing shrub or small tree that now dominates many arid-zone riparian systems throughout the region.[1] Fig. 1 illustrates the abundances that can be attained, in this case at the Virgin River in southern Nevada. While tamarisk has colonized numerous wildland ecosystems, the most severe infestations occur along regulated rivers and reservoirs where it benefits from altered hydrologies and other anthropogenic influences, and may place severe demands on limited water supplies.[2] A variety of control technologies exist or are being developed to control tamarisk, and substantial financial resources are directed to managing this invasive weed. However, controversies continue over the nature of its economic and environmental impacts and whether control or eradication will provide the benefits anticipated.[3-5]
BACKGROUND
Tamarisk is the common name for shrubs and trees of the genus Tamarix, which along with the Myricaria and Reaumuria comprise the Tamaricaceae, a family associated with arid and semi-arid, frequently saline, environments of the Old World (Europe, Africa, and Asia). At least 54 species of Tamarix are known, and it is often a dominant element of the vegetation in low-lying basins and river corridors where heat, salt, and irregular water availability limit the number of other riparian plants that can tolerate these conditions.[6] These trees can use saline groundwater and excrete excess salt from glands on the leaves and green stems. Leaves consist of cedar-like bracts, and these two traits suggest the other common name for genus, saltcedar. Many members of the genus are deciduous and frost-tolerant, losing their foliage during the winter months, while some species, particularly T. aphylla,
commonly known as athel, are evergreen and are associated with warmer frost-free regions. Plants produce long racemes of insect-and wind-pollinated pink to white flowers producing copious quantities of small (ca. 0.5mm length), short-lived windblown seed.
