Invasiveness Ranking System for Non-Native Plants of Alaska

Current global distribution (0–5) 3Scotch broom is native to the British Isles as well as Central andSouthern Europe to the Canary Islands (USDA, ARS 2004). Ithas become widely naturalized in North America (Hoshovsky1986) as well as India, Iran, New Zealand, Australia, and SouthAfrica (Prasad 2002).Extent of the species U.S. range and/or occurrence of5formal state or provincial listing (0–5)In western North America, scotch broom has now becomeestablished along the inland valleys of the Pacific Northwest,from British Columbia to central California (Hitchcock andCronquist 1990). It is found in 25 states (USDA 2002) and islisted as noxious in California, Hawaii, Idaho, Oregon, andWashington (Invaders Database System 2003).Total for Ecological Amplitude and Distribution 18/25Feasibility of ControlScoreSeed banks (0–3) 3Seeds remain viable for over 80 years (Bossard et al. 2000,Coombs and Turner 1995, Hoshovsky 1986, Prasad 2002).Vegetative regeneration (0–3) 2Plants can resprout after burning or cutting, particularly duringthe rainy season (Bossard et al. 2000, Hoshovsky 1986).Level of effort required (0–4) 3Hand pulling, cutting, or mowing can be effective. However,broom easily resprouts and seeds are long-lived. Therefore, longtermmonitoring is needed (Hoshovsky 1986).Total for Feasibility of Control 8/10Total score for 4 sections 69/100§Dactylis glomerata L.Ranking SummaryEcoregion known or expected to occur inSouth CoastalInterior BorealArctic AlpineYesYesYesPotential Max. ScoreEcological Impact 40 16Biological Characteristics and Dispersal 25 10Amplitude and Distribution 25 22Feasibility of Control 10 5Relative Maximum 53Climatic ComparisonCollected inAlaska regions?CLIMEXsimilarity?South Coastal Yes –Interior Boreal No YesArctic Alpine No YesDactylis glomerata has been collected in the south coastalecogeographic region of Alaska (Hultén 1968, Welsh 1974,AKEPIC 2005,UAM 2004). Dactylis glomerata is known to occurthroughout Europe and has been documented as far north as thenorthern province in Norway (Finnmark) at 70°N (Lid and Lid1994). The range of this species also includes Røros and Dombås,Norway, which have 76% and 63% climatic matches with Nome,and 55% and 52% climatic matches with Fairbanks, respectively.Thus, it may be possible for Dactylis glomerata to becomeestablished in the interior boreal and arctic alpine ecogeographicregions.Ecological ImpactScoreImpact on Ecosystem Processes (0–10) 5Dense stands of orchardgrass may suppress the growth ofnative shrubs (Anderson and Brooks 1975) and trees (Powellet al. 1994). Lodgepole pine seedling survival and growth ratedecreased as the density of orchardgrass increased in a field studyconducted in British Columbia (Powell et al. 1994).Impact on Natural Community Structure (0–10) 3Orchardgrass alone usually does not form a dense layer, but whenit grows with another perennial European grass such as Festucaarundinacea, Holcus lanatus, or Phalaris aquatica, it is capable ofdeveloping a dense stand that excludes native perennial grasses(Cobrin et al. 2004, Cal-IPC 2005).common names: orchardgrassImpact on Natural Community Composition (0–10) 3As a codominant with other exotic perennial grasses,orchardgrass is capable of causing reduction and extirpation ofnative perennial grasses (Cobrin et al. 2004, Cal-IPC 2005).Impact on Higher Trophic Levels (0–10) 5Orchardgrass is moderately nutritious and highly palatable tograzing animals. Orchardgrass also provides food and cover fora number of small mammals, birds, and insects (Sullivan 1992).However, suppressed development of native shrubs might bedetrimental to native wildlife habitat (Anderson and Brooks1975).Total for Ecological Impact 16/40Biological Characteristics and Dispersal ScoreMode of Reproduction (0–3) 1Orchardgrass reproduces by seeds (Beddows 1957). Becauseorchardgrass breeders have traditionally focused on forage traits,most cultivars are not necessarily good seed producers (Casler etal. 2003).Long-distance dispersal (0–3) 2Most seeds fall directly to the soil below the parent plant. Someseeds attach to animals and travel long distances (Beddows 1957).Spread by humans (0–3) 3Orchardgrass is widely used as a forage crop and is recommendedas part of a mix for erosion control and pasture rehabilitation(Anderson and Brooks 1975, McLean and Clark 1980). It is acommon commercial seed contaminant (Bush et al. 2005).Allelopathic (0–2) 0Orchardgrass is not listed as an allelopathic (USDA, NRCS2006). In experimental studies orchardgrass did not showsignificant inhibition of germination, root, and shoot growth(Grant and Sallens 1964, Larson et al. 1995).Competitive Ability (0–3) 1Orchardgrass is able to compete with native perennials andannual species (Corbin et al. 2004).Thicket-forming/Smothering growth form (0–2) 0Orchardgrass rarely forms dense layers, but it is capable ofcreating a dense stand when grown with other perennialEuropean grasses (Corbin et al. 2004, Cal-IPC 2005).B-31