ARS | Publication request: White Sweetclover Invasions on Alaska Floodplains

Submitted to: Workshop Proceedings
Publication Acceptance Date: October 28, 2004
Publication Date: October 29, 2004
Citation: Conn, J.S., Shepherd, M. 2004. White Sweetclover Invasions On Alaska Floodplains. Workshop Proceedings.

Interpretive Summary: Technical Abstract White sweetclover, Melilotus alba, was reported to have colonized the Stikine River in Southeast, Alaska, the Matanuska River near Anchorage and the Nenana River in Interior Alaska. Surveys were conducted by airplane and by boat to determine the source and extent of the invasions. The aerial survey of the Stikine River showed that white sweetclover inhabited nearly all river bars from Telegraph Creek to end of the river. It was not found on any of the Stikine tributaries below Telegraph Creek. Soil samples were collected on the lower Stikine River and permanent plots were established to monitor population changes and impacts on native vegetation. It was noticed that at one island the 2-year-old plants from last year had been replaced by a stand of first-year plants. Shade produced by dense 2nd-year stands may prevent growth of seedlings. Boat surveys were conducted on the lower Matanuska and Knik Rivers. On the Matanuska River, continuous populations of white sweetclover were found from the old Glenn Highway Bridge to the end of the river. White Sweetclover was not found on the adjacent Knik River, except below the junction of the Knik with the Matanuska. Soil samples were collected both from the Matanuska and Knik sample locations. The aerial survey of the Nenana River revealed that dense white sweetclover populations occur from the Rex Bridge on the George Parks Highway to approximately 8 miles downstream. A boat survey showed that there is a stand of white sweetclover at the Healy power plant, which is located 25 miles upriver of the main infestation. There were several small populations of white sweetclover upriver of the Rex Bridge, but the main populations were located downriver from the bridge. White Sweetclover had been planted along the George Parks Highway in the early 1990s and is the likely seed source for the main infestation. Soil samples were collected both in areas where white sweetclover was growing and in areas where it was not to determine whether soil characteristics were limiting its distribution. In all locations white sweetclover populations were greater in areas with fine sand rather than cobbley soil surfaces.

Technical Abstract: Technical Abstract White sweetclover, Melilotus alba, was reported to have colonized the Stikine River in Southeast, Alaska, the Matanuska River near Anchorage and the Nenana River in Interior Alaska. Surveys were conducted by airplane and by boat to determine the source and extent of the invasions. The aerial survey of the Stikine River showed that white sweetclover inhabited nearly all river bars from Telegraph Creek to end of the river. It was not found on any of the Stikine tributaries below Telegraph Creek. Soil samples were collected on the lower Stikine River and permanent plots were established to monitor population changes and impacts on native vegetation. It was noticed that at one island the 2-year-old plants from last year had been replaced by a stand of first-year plants. Shade produced by dense 2nd-year stands may prevent growth of seedlings. Boat surveys were conducted on the lower Matanuska and Knik Rivers. On the Matanuska River, continuous populations of white sweetclover were found from the old Glenn Highway Bridge to the end of the river. White Sweetclover was not found on the adjacent Knik River, except below the junction of the Knik with the Matanuska. Soil samples were collected both from the Matanuska and Knik sample locations. The aerial survey of the Nenana River revealed that dense white sweetclover populations occur from the Rex Bridge on the George Parks Highway to approximately 8 miles downstream. A boat survey showed that there is a stand of white sweetclover at the Healy power plant, which is located 25 miles upriver of the main infestation. There were several small populations of white sweetclover upriver of the Rex Bridge, but the main populations were located downriver from the bridge. White Sweetclover had been planted along the George Parks Highway in the early 1990s and is the likely seed source for the main infestation. Soil samples were collected both in areas where white sweetclover was growing and in areas where it was not to determine whether soil characteristics were limiting its distribution. In all locations white sweetclover populations were greater in areas with fine sand rather than cobbley soil surfaces.