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Tamarisk (a.k.a. saltcedar, Tamarix spp.) is an invasive plant species that occurs throughout western riparian and wetland ecosystems. It is implicated in alterations of ecosystem structure and function and is the subject of many local control projects, including removal using heavy equipment. We evaluated short-term vegetation responses to mechanical Tamarix spp. removal at sites ranging from 2 to 5 yr post-treatment along the Virgin River in Nevada, USA. Treatments resulted in lower density and cover (but not eradication) of Tamarix spp., increased cover of the native shrub Pluchea sericia (arrow weed), decreased density and cover of all woody species combined, increased density of both native annual forbs and the nonnative annual Salsola tragus (prickly Russian-thistle), and lower density of nonnative annual grasses. The treated plots had lower mean woody species richness, but greater herbaceous species richness and diversity. Among herbaceous species, native taxa increased in richness whereas nonnative species increased in both species richness and diversity. Thus, efforts to remove Tamarix spp. at the Virgin River reduced vegetative cover contributing to fuel loads and probability of fire, and resulted in positive effects for native plant diversity, with mixed effects on other nonnative species. However, absolute abundances of native species and species diversity were very low, suggesting that targets of restoring vegetation to pre-invasion conditions were not met. Longer evaluation periods are needed to adequately evaluate how short-term post-treatment patterns translate to long-term patterns of plant community dynamics.
Nomenclature: Tamarix (tamarisk).
Key words: Virgin River, saltcedar, riparian, invasive species control, bull dozer.
Riparian ecosystems contain critical natural resources, buffer anthropogenic contaminants, and stabilize stream channels (Naiman et al. 1993; Sabo et al. 2005). Most riparian areas have been highly modified through alter- ations to natural flow regimes, water diversions and ground water pumping (Richardson et al. 2007) often resulting in a suite of negative ecological effects (Patten 1998, Stromberg 2001). In riparian zones of the arid and semi-arid western United States, one of the primary indicators of altered conditions is the presence and dominance of nonnative invasive plants, chiefly Tamarix spp. (tamarisk, saltcedar) (Hultine and Dudley 2013).
Intentionally introduced to North America from southern Europe, Asia, and North Africa, Tamarix spp. has been used for windbreaks and to resist streambank erosion. Escaping cultivation by the...