Invasiveness Ranking System for Non-Native Plants of Alaska

Medicago sativa ssp. falcata (L.) Arcang.Ranking SummaryEcoregion known or expected to occur inSouth CoastalInterior BorealArctic AlpineYesYesYesPotential Max. ScoreEcological Impact 30 15Biological Characteristics and Dispersal 25 17Amplitude and Distribution 19 15Feasibility of Control 10 7Relative Maximum 64Climatic ComparisonCollected inAlaska regions?CLIMEXsimilarity?South Coastal Yes –Interior Boreal Yes –Arctic Alpine No YesMedicago sativa ssp. falcata has been collected in the south coastal(Seward and Exit Glacier) and interior boreal (Anchorage,Fairbanks, Wasilla, Palmer, Gakona, and Haines Junction)ecogeographic regions in Alaska (Hultén 1968, AKEPIC 2005,UAM 2005). The CLIMEX matching program indicates theclimatic similarity between Nome and areas where yellowalfalfa is well established is moderately high. The range of yellowalfalfa includes Røros, Norway, and Zlatoust and Kirov, Russia(Gubanov et al. 2003, Hultén 1968). The climate of these townsshas a 76%, 71%, and 66% match with Nome, respectively. Thesimilar climates suggest that the establishment of yellow alfalfa inarctic alpine ecogeographic region of Alaska may be possible.Ecological ImpactScoreImpact on Ecosystem Processes (0–10) 5Yellow alfalfa in symbiosis with the bacteria Rhizobia, increasessoil nitrogen levels by fixing atmospheric nitrogen (USDA2002). The alteration of soil condition may facilitate colonizationby other plant species. Alfalfa increases the growth of aspenseedlings (Powell and Bork 2004). In Saskatchewan ranchlandsseeded with alfalfa were susceptible to regrowth of aspen andprickly rose (Rosa acicularis) (Bowes 1981, Sullivan 1992).Impact on Natural Community Structure (0–10) 3Yellow alfalfa establishes in an existing layer of vegetation andsubsequently increases the density of the layer (I. Lapina pers.obs., Klett et al. 1984, Duebbert et al. 1981). There are no recordsconcerning the elimination of existing layers of vegetation by thepresence of alfalfa.Impact on Natural Community Composition (0–10)Documentation specific to the alteration of communitycomposition was not found in this review.UB-77common names: yellow alfalfaImpact on Higher Trophic Levels (0–10) 7A total of 27 species of birds and 46 mammals are known touse alfalfa (Graham 1941). Yellow alfalfa is consumed by mostbig game animals, including moose and mule deer (Kufeld1973, Leach 1956). Many small mammals, including marmots,mice, and ground squirrels graze alfalfa. Waterfowl such asthe American wigeon and mallards eat the leaves, flowers, orseeds. Seeds are also consumed by rodents, rabbits, and uplandbirds. Yellow alfalfa is a source of nectar and pollen for insects(Graham 1941, Stanton 1974) and it is particularly attractive tosolitary bees (Carlson pers. obs.). Dabbling ducks (mallards, bluewingedteals, northern pintail, northern shovelers, and Americanwigeons) will nest in yellow alfalfa stands (Klett et al. 1984).Undisturbed alfalfa fields provide food and cover for a variety ofbirds, including sharp-tailed grouse, American bitterns, marshhawks, short-eared owls, and passerines (Duebbert et al. 1981).Alfalfa is a host for numerous pathogens (Sullivan 1992).Total for Ecological Impact 15/30Biological Characteristics and Dispersal ScoreMode of Reproduction (0–3) 3Yellow alfalfa reproduces by seed only (USDA 2002). The meannumber of seeds produced by an individual plant has beendocumented at 5,320 (Stevens 1932).Long-distance dispersal (0–3) 2Yellow alfalfa seeds are large and not easily dispersed. Herbivoreslikely facilitate the spread of the plant’s seeds (Duebbert et al.1981, Kufeld 1973, Leach 1956).Spread by humans (0–3) 3Yellow alfalfa is cultivated worldwide and is used in erosioncontrolprojects, for rangeland and wildlife habitat restoration,and for hay production. The utility of the plant probablycontributes to its spread (Klett et al. 1984, McLean et al. 1971).Allelopathic (0–2) 0Yellow alfalfa is not allelophathic (USDA 2002).Competitive Ability (0–3) 3Yellow alfalfa seedlings have faster root extension and greatertotal root length than other perennial legumes (Bell 2004).Established alfalfa plants can be very competitive (Sullivan 1992).However, in Saskatchewan ranchlands seeded with alfalfa wereoutcompeted by aspen and prickly rose (Rosa acicularis) (Bowes1981).Thicket-forming/Smothering growth form (0–2) 1Yellow alfalfa can grow very densely from 3 to 5 feet high and canbe taller than surrounding forbs and grasses (USDA 2002, Royerand Dickinson 1999).Germination requirements (0–3) 2Although seed germination can be inhibited by the presence ofpine and juniper litter (Sullivan 1992), seeding in undisturbedrangelands and woodlands can be successful (MAFRI 2004).Other invasive species in the genus (0–3) 3Medicago sativa ssp. sativa L., Medicago lupulina L., M. polymorphaL., and M. minima (L.) L. (USDA 2002, Royer and Dickinson1999, Hultén, E. 1968).Aquatic, wetland or riparian species (0–3) 0Yellow alfalfa has established along roadsides, in waste areas,(Hitchcock and Cronquist 1973, Hultén 1968) and in active andabandoned agricultural fields (Royer and Dickinson 1999). It isnot known to invade wetlands or riparian communities.Total for Biological Characteristics and Dispersal 17/25