Authored By: T. L. Wurtz, M. Macander, B. T. Spellman
Tricia L. Wurtz, Matt Macander, and Blaine T. Spellman
USDA Forest Service Pacific Northwest Research Station, ABR Inc.--Environmental Research & Services, and University of Alaska Fairbanks School of Agriculture and Land Resources Management
Alaska has few invasive plants, and most of them are found only along the state’s limited road system. One of the most-widely distributed invasives in the state, Melilotus alba, or sweetclover, has been sown both as a forage crop and as a roadside stabilization species. Melilotus has recently been found to have moved from roadsides to the floodplains of at least three glacial rivers. This species has aggressively colonized the lower Stikine river floodplain, and occurs there in dense, monospecific stands. It is at an earlier stage of colonization of the Matanuska and Nenana River floodplains as well. To locate other rivers that may have been colonized, and to determine which rivers might be most at risk for future colonization, we examined the distribution of Melilotus near 120 bridges along 5 of the state’s major highways. At thirteen bridges, we found Melilotus growing on natural floodplain surfaces; in all thirteen cases we found Melilotus growing in moderate to heavy infestations on the roadside immediately adjacent to the bridge. In addition, 41 bridges had Melilotus growing on the roadside immediately adjacent to the bridge, but none yet on a natural floodplain surface. A path analysis of those 54 rivers examined the vulnerability of downstream terrain to invasion, and the location downstream of lands of high conservation significance, such as National Parks and Wildlife Refuges. Results point to certain bridges and river systems as critical control points for the spread of invasive plants in Alaska; both monitoring and control efforts should be focused at these points. This path analysis may help prevent the spread of other invasive species from roadsides to river networks in Alaska.
Exotic Pests Session - Tuesday Afternoon
corresponding author:
Tricia L. Wurtz
Boreal Ecology Cooperative Research Unit
University of Alaska, Fairbanks
PO Box 756780
Fairbanks, AK 99775-6780
907-474-5994
twurtz@fs.fed.us