Invasiveness Ranking System for Non-Native Plants of Alaska

Germination requirements (0–3) 3Orchardgrass is widely used for pasture improvements and iscommonly broadcast seeded (Sullivan 1992). Thus, orchardgrasspresumably can germinate on vegetated sites.Other invasive species in the genus (0–3) 0None (USDA, NRCS 2006).Aquatic, wetland or riparian species (0–3) 0Orchardgrass prefers dry soils in waste places, fields, yards, androadsides (Hultén 1968, Welsh 1974).Total for Biological Characteristics and Dispersal 10/25Ecological Amplitude and Distribution ScoreHighly domesticated or a weed of agriculture (0–4) 4Orchardgrass is widely used as a forage crop. A number ofcultivars have been developed (Anderson and Brooks 1975,McLean and Clark 1980).Known level of impact in natural areas (0–6) 3Orchardgrass has invaded oak woodlands and perennialgrasslands in California (Williamson and Harrison 2002, Corbinet al. 2004). However, its impact on natural communities isconsidered to be low (Cal-IPC 2005). Orchardgrass appearsto have potential for invading and modifying existing plantcommunities in Rocky Mountain National Park (Rutledge andMcLendon 1996). Orchardgrass invades open woodlands andprairies in western Oregon (M. Carlson pers. obs.)Role of anthropogenic and natural disturbance inestablishment (0–5)Orchardgrass is usually associated with human disturbances(Hultén 1968, Welsh 1974, Williamson and Harrison 2002),but it is known to invade undisturbed coastal prairie grasslands(Corbin et al. 2004).5Current global distribution (0–5) 5Orchardgrass was introduced from Europe and it is now presentthroughout temperate Asia and North America. It was alsointroduced into South America, Australia, and New Zealand, andcan be found in the Arctic (Hultén 1968, Tolmachev et al. 1995).Extent of the species U.S. range and/or occurrence of5formal state or provincial listing (0–5)Orchardgrass is present throughout the United States andCanada (USDA, NRCS 2006). It is declared noxious in NewJersey and Virginia (Rice 2006).Total for Ecological Amplitude and Distribution 22/25Feasibility of ControlScoreSeed banks (0–3) 0Orchardgrass does not have long-lived seeds. Most seedsgerminate in the fall or following spring (Dorph-Petersen 1925,Beddows 1959).Vegetative regeneration (0–3) 2Vegetative regeneration of orchardgrass occurs through tilling.When plants are cut or plowed, rooting stems may develop newplants (Beddows 1957).Level of effort required (0–4) 3Generally, mechanical methods are not effective in control oforchardgrass. Numerous herbicides are available for this species(Rutledge and McLendon 1996).Total for Feasibility of Control 5/10Total score for 4 sections 54/100§Descurainia sophia (L.)Webb ex Prantl.Ranking SummaryEcoregion known or expected to occur inSouth CoastalInterior BorealArctic AlpineYesYesYesPotential Max. ScoreEcological Impact 40 8Biological Characteristics and Dispersal 25 13Amplitude and Distribution 25 18Feasibility of Control 10 2Relative Maximum 41Climatic ComparisonCollected inAlaska regions?CLIMEXsimilarity?South Coastal Yes –Interior Boreal Yes –Arctic Alpine Yes –Descurainia sophia has been collected from the south coastal,interior boreal, and arctic alpine ecoregions of Alaska (Hultén1968, UAM 2004).common names: flixweed, herb sophiaEcological ImpactScoreImpact on Ecosystem Processes (0–10) 0Flixweed is a pioneer species of disturbed soils, facilitating theestablishment of other weedy species. It can form dense standsthat become dried, creating a fire hazard. If flixweed standsdo not burn, dried plants facilitate cheatgrass establishment(Howard 2003). Nevertheless in Alaska, this species does nottend to invade natural plant communities (M. Carlson pers. obs.,I. Lapina pers. obs.).Impact on Natural Community Structure (0–10) 0Flixweed establishes in an existing layer and changes the densityof the layer on disturbed sites (I. Lapina pers. obs., WSSA2003). No impact on the natural community structure has beendocumented. Increases total percent cover in open, disturbedsites.Impact on Natural Community Composition (0–10) 1Flixweed has not been observed in undisturbed areas in Alaska;no perceived impact on native populations has been documented(Densmore et al. 2001).B-32