|Shephard, M - USDA FOREST SERVICE|
|Carlson, M - UNIV. OF ALASKA|
|Lapina, I - UNIV. OF ALASKA|
|Hebert, M - UNIV. OF ALASKA|
|Gronquist, R - BUREAU OF LAND MANAGEMENT|
|Densmore, R - US GEOLOGICAL SURVEY|
|Rasy, M - UNIV. OF ALASKA|
Submitted to: Arctic, Antarctic, and Alpine Research (AAAR)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 28, 2007
Publication Date: May 20, 2008
Citation: Conn, J.S., Beattie, K.L., Shephard, M.A., Carlson, M., Lapina, I., Hebert, M., Gronquist, R., Densmore, R., Rasy, M. 2008. Alaska Melilotus invasions: distribution, origin, and susceptibility of plant communities. Arctic, Antarctic, and Alpine Research (AAAR). 40(2):298-308. Interpretive Summary: White sweetclover (Melilotus alba) and yellow sweetclover (Melilotus officinalis) have invaded roadsides and river floodplains in Alaska. Numerous surveys have been conducted to locate non-native plants, including the sweetclovers, and this data has been entered into the Alaska Exotic Plant Information Clearinghouse database. These data, plus data from surveys to locate sweetclover on the Stikine, Matanuska, and Nenana Rivers were used to construct distributions maps for white and yellow sweetclover in Alaska. Sweetclovers were distributed from southeast Alaska which has a mild, very rainy (100 inches or more) climate to north of the Arctic Circle, where there is little rain (less than 7 inches) and the annual temperature is below freezing. Sweetclover was only found in disturbed sites and was especially common along roadsides or on river floodplains. No evidence was found that sweetclover were deliberately planted along highways. The roadside populations may have gotten started by inadvertent purchase of sweetclover seed rather than white clover seed or from contamination of seed for revegetation. Sweetclover populations on the Nenana and Matanuska Rivers likely arose from populations growing along highways that intersected the rivers. Sweetclover seed is known to float and can be carried great distances in water. The infestation on the Stikine river is not attributed to roadside populations and probably started from agricultural fields at Telegraph Creek/Glenora, British Columbia that provided fooder for pack animals used during the Cassiar and Klondike gold rushes. Sweetclovers are known to require alkaline soils. Soils that upland plant communities inhabit in Alaska are acidic, which may protect them from invasion by sweetclover. The floodplains of the lower Tanana River, Yukon and Copper Rivers have alkaline soils and are at risk for invasion by sweetclover.
Technical Abstract: Present distributions of Melilotus alba and M. officinalis in Alaska were determined from surveys for alien plant species conducted from 2002 – 2005 by various State and Federal agencies. Data was entered into the Alaska Exotic Plant Information Clearinghouse (AKEPIC) statewide alien plant database. Data recorded for each sample location were: geographic location, observers, plant species, population area, and average percent cover of each species. Aerial and boat-based surveys were used to determine the distribution of Melilotus on portions of the Stikine, Matanuska, Knik, Nenana, Tanana, and Copper Rivers. M. alba and M. officinalis were found in Alaska at 721 and 205 sites, respectively. The northward limit of distribution of M. alba was 66.19 N and 64.87 N for M. officinalis. Both species were strictly associated with disturbance, especially that occurring on roadsides and river floodplains. M. alba extended no further than 10 m from the road edge at sample locations along the Alaska and Dalton Highways. The exception to this pattern was where M. alba on roadsides met river floodplains and dispersed downriver. The Matanuska River M. alba infestation originated at the Old Glenn Highway Bridge and continued to Cook Inlet. Melilotus populations on the Nenana River originated both from roadside populations and from a mixed population of M. alba and M. officinalis near Healy, Alaska, though only M. alba spread downriver successfully. It has now reached the Tanana River. M. alba also occurs on a 190-km stretch of the Stikine River from near Telegraph Creek, British Columbia to its delta. The origin of this infestation was probably agricultural, dating from when the Glenora/Telegraph Creek area was used as a staging area for miners going to the Klondike gold fields. Populations on all three rivers were most extensive on braided sections and cover and density of M. alba was greater in areas with fine sand rather than cobbley soil. Soil samples were collected from locations where M. alba occurred on the Stikine, Matanuska and Nenana Rivers and the Alaska and Parks Highways. On the Nenana River, soil characteristics did not differ between samples where M. alba was growing versus similar areas where it had not yet reached. The pH of river soils (7.9 – 8.3) was significantly higher than highway soils (7.3). Upland taiga plant communities may be protected from invasion by Melilotus since they grow on acid soils on which Melilotus does not thrive, but early succession communities on the Tanana, Yukon and Copper River floodplains are susceptible because soils are alkaline.