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DISTRIBUTION OF SELECTED INVASIVE PLANTS IN RIPARIAN ECOSYSTEMS OF THE WESTERN UNITED STATES
Citation:
Ringold, P L., T. K. Magee, AND J Van Sickle. DISTRIBUTION OF SELECTED INVASIVE PLANTS IN RIPARIAN ECOSYSTEMS OF THE WESTERN UNITED STATES. Presented at Ecological Society of America annual meeting, Savannah, GA, August 3-8, 2003.
Description:
Riparian ecosystems typically exhibit high levels of plant species richness, physical disturbance, and interconnectedness; characteristics that may favor establishment and spread of invasive plant species. To assess the magnitude of this invasion, we organized an extensive survey over 12 western states for 1 cryptogenic and 11 alien, invasive plant taxa (Arctium minus (Common Burdock), Arundo donax (Giant Reed), Bromus tectorum (Cheatgrass), Carduus nutans (Musk Thistle), Cirsium arvense (Canada Thistle), Dipsacus fullonum (Teasel), Elaeagnus angustifolia (Russian olive), Euphorbia esula (Leafy Spurge), Hedera helix (English Ivy), Phalaris arundinacea (Reed Canarygrass), Rubus discolor (Himalayan Blackberry), and Taramix spp. (Salt Cedar)). This work is part of the four year EMAP (Environmental Monitoring and Assessment Program) Western Stream Pilot, which focuses on the assessment of diverse stream properties, using a probability sample of 1200 streams. Target species were selected based on invasive character, widespread distribution, frequent or potentially increasing occurrence in streamside settings of the study area, and for ease of identification. Field crews were trained to recognize 6 to 11 of the target species, and each crew searched for the list of species designated for the state(s) they sampled. Remeasurements by expert crews in some states and by repeat sample visits in all states document a high level of repeatability. At 300 sites sampled during 2001, the target weeds most frequently observed in the states where they were surveyed included C. arvense at 31% of sampled streams; E. esula at 21% and P. arundinacea at 13%. In general, and consistent with numerous plausible mechanisms, all target species were more frequently found on higher vs. lower order streams. For example, C. arvense was found at 51% of surveyed streams with Strahler order 4 or greater and only 19% of streams with Strahler order 1 or 2.