Invasiveness Ranking System for Non-Native Plants of Alaska

Ecological Amplitude and Distribution ScoreHighly domesticated or a weed of agriculture (0–4) 4The species was introduced to North America in the late 1600s asa garden ornamental (Beck 2001, Carpenter and Murray 1998).At present, it is a weed of rangeland and pastures (Darwent et al.1975, Whitson et al. 2000).Known level of impact in natural areas (0–6) 4Yellow toadflax invades high quality areas with no knowndisturbance for the last 100 years in Rocky Mountain NationalPark, Colorado and has the potential to modify existing nativecommunities (Rutledge and McLendon 1996). This invasivespecies has invaded Coconino National Forest in northernArizona (Zouhar 2001). Yellow toadflax was found in jack pine–lichen woodland of the upper boreal forest in northern Quebec;and in a ponderosa pine–bluebunch wheatgrass community inMontana (Zouhar 2001Role of anthropogenic and natural disturbance in3establishment (0–5)Disturbance may be necessary for establishment to occur. Onceestablished, it readily spreads into adjacent nondisturbed areas(Beck 2001). It can invade communities with naturally-occurringdisturbances (Arnold 1982). This taxon persisted for at least30 years in Manitoba, following an initial disturbance (Zouhar2003).Current global distribution (0–5) 5Linaria vulgaris is a native of Southeastern Europe andSouthwestern Asia. The present world distribution includesmost of Europe and Asia, Australia, New Zealand, South Africa,Jamaica, Chile, and North and South America, includingsubarctic regions (Hultén. 1968).Extent of the species U.S. range and/or occurrence of5formal state or provincial listing (0–5)This weed is declared noxious in nine states and four Canadianprovinces (Invader Database System 2003). This species is arestricted noxious weed in Alaska (Alaska Administrative Code).It is found throughout the continental United States and in everyCanadian province (Carpenter and Murray 1998, USDA 2002).Total for Ecological Amplitude and Distribution 21/25Feasibility of ControlScoreSeed banks (0–3) 3The seeds can remain dormant for up to 10 years (Carpenter andMurray 1998, Rutledge and McLendon 1996).Vegetative regeneration (0–3) 2Vegetative regeneration is possible from root fragments as short as1 cm (Carpenter Murray 1998, Rutledge and McLendon 1996).Level of effort required (0–4) 4Successful control can be obtained by mechanical and chemicaltreatment. The treatments must be repeated every year for at least10 years due to vegetative propagation and longevity of the seedbank (Carpenter and Murray 1998).Total for Feasibility of Control 9/10Total score for 4 sections 69/100§Lolium perenne ssp. multiflorum(Lam.) HusnotRanking SummaryEcoregion known or expected to occur inSouth CoastalInterior BorealArctic AlpineYesYesYesPotential Max. ScoreEcological Impact 40 14Biological Characteristics and Dispersal 25 10Amplitude and Distribution 25 15Feasibility of Control 10 2Relative Maximum 41Climatic ComparisonCollected inAlaska regions?CLIMEXsimilarity?South Coastal Yes –Interior Boreal Yes –Arctic Alpine Yes –Lolium perenne ssp. multiflorum has been collected in allecogeographic regions of Alaska (Hultén 1968, UAM 2004).common names: annual ryegrass,Italian ryegrass, perennial ryegrassEcological ImpactScoreImpact on Ecosystem Processes (0–10) 3Despite being widely planted for erosion control, seeding of thisspecies may increase erosion in the following years. It addition,Italian ryegrass may increase the frequency and severity of fire(Carey 1995, Zedler et al. 1983). Observations in Alaska indicatethat its impacts are minimal. Seedings in Denali National Parkdo not persist. No reduction in native species is recorded atintermediate densities (Densmore et al. 2000).Impact on Natural Community Structure (0–10) 3Some varieties of ryegrass are capable of forming dense stands(Densmore et al. 2000, Facelli et al. 1987).Impact on Natural Community Composition (0–10) 3In seeded plots in burned chaparral California, there was a 40%reduction in species diversity relative to unseeded plots. Italianryegrass can hinder woody species establishment throughresource competition and increased fire potential (Carey 1995,Facelli et al. 1987). However, in numerous habitats in the West(including Alaska), it appears that this species is readily replacedby tall herbaceous and woody species (Carey 1995 and referencestherein, Densmore et al. 2000).B-68