Research Task: 8327CMZ.3.0
Task Manager: Jonathan Friedman
In the arid/semi-arid interior of western North America, riparian cottonwood (Populus fremontii), willow (Salix spp.), and other native species are being replaced by exotic shrubs and trees. Saltcedar (both Tamarix ramosissima and T. chinensis), the most abundant invasive, now covers about 500,000 ha and has become the dominant riparian woody species in much of the southwestern United States; Russian-olive and Siberian elm are also important invasive species throughout much of the West. These great changes in species composition of riparian woody plants have been associated with loss of plant diversity, degradation of habitat for vertebrate animals, decreased channel conveyance, increased water loss from evapotranspiration, and loss of aesthetic and recreational opportunities. This study examines how environmental factors, including climate change, latitude, livestock grazing, substrate composition, flood regimes, and the upstream presence of dams influence the susceptibility of a river to invasion, especially by saltcedar and Russian olive. Approaches used include vegetation surveys at 500 long-term USGS stream gages, common-garden studies investigating latitudinal variation in phenology and cold hardiness, and experimental manipulations testing the importance of specific factors for plant survival. Results will be used to predict how changes in climate and related changes in stream flow will affect susceptibility of riparian areas to invasion by saltcedar and Russian olive. This information will be provided to land managers who need to know which systems are most susceptible to invasion by exotics and which are most likely to respond positively to restoration efforts.
For more information contact Jonathan Friedman
U.S. Department of the Interior | U.S. Geological Survey
URL: http://www.fort.usgs.gov/Research/research_tasks.asp
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