Invasiveness Ranking System for Non-Native Plants of Alaska

Feasibility of ControlScoreSeed banks (0–3) 2Seeds buried in soil and permanently submerged in water lostviability after 23 months (van der Toorn and ten Hove 1982).Vegetative regeneration (0–3) 2The species is documented as regenerating from pieces of stem(Plants for a future 2002).Level of effort required (0–4) 3Common brassbuttons can grow on very soft, deep mud, makinginfestations nearly inaccessible by foot or boat. No herbicides areselective enough to be used in wetlands without the potential forinjuring native species.Total for Feasibility of Control 7/10Total score for 4 sections 41/98§Crepis tectorum L.Ranking SummaryEcoregion known or expected to occur inSouth CoastalInterior BorealArctic AlpineYesYesYesPotential Max. ScoreEcological Impact 30 9Biological Characteristics and Dispersal 25 17Amplitude and Distribution 25 18Feasibility of Control 7 3Relative MaximumClimatic ComparisonCollected inAlaska regions?CLIMEXsimilarity?South Coastal Yes –Interior Boreal Yes –Arctic Alpine Yes –Crepis tectorum has been collected in south coastal [Seward,Skagway, Lake Clark, and Unalaska (UAM 2004)], interiorboreal [Anchorage and Fairbanks (Hultén 1968, UAM 2004),Wasilla (AKNHP 2003), and Denali National Park and Preserve(Densmore et al. 2001)], and arctic alpine [Dillingham (UAM2004)] ecoregions in Alaska. The range of the species includesDillingham, of the arctic alpine ecoregion (UAM 2004) whereit withstands winter temperatures to -53 °F and a mean of 140frost-free days (WRCC 2004). It is unclear if Crepis tectorum canestablish in arctic sites with shorter growing seasons (e.g., Nomehas similar extreme winter temperatures, but averages 30 fewerfrost-free days (WRCC 2004).Ecological ImpactScoreImpact on Ecosystem Processes (0–10) 3Narrowleaf hawksbeard likely reduces water availability. It maydelay the establishment of native species on naturally disturbedsoil (J. Conn pers. com.) including following forest fires ininterior Alaska (K. Villano 2007).Impact on Natural Community Structure (0–10) 3Narrowleaf hawksbeard has established along the Knik Riverwhere it changes the density of other species (M. Shephard pers.com.).Impact on Natural Community Composition (0–10) 3Dense stands of narrowleaf hawksbeard in Denali National Parkand Healy have displaced native colonizers (R. Densmore pers.com.).Impact on Higher Trophic Levels (0–10)UNo information was found identifying impacts on higher trophiclevels.Total for Ecological Impact 9/30common names: narrowleaf hawksbeardBiological Characteristics and Dispersal ScoreMode of Reproduction (0–3) 3Narrowleaf hawksbeard reproduces by seeds. Each plant iscapable of producing over 49,000 seeds (Royer and Dickinson1999).Long-distance dispersal (0–3) 3The small seeds have long pappus hairs that aid in wind dispersal(SAFRR 1984, Royer and Dickinson 1999).Spread by humans (0–3) 3Narrowleaf hawksbeard is often a contaminant in agriculturalseed (MAFRI 2004). It spreads along roadsides in Alaska(Densmore et al. 2001).Allelopathic (0–2) 0NoneCompetitive Ability (0–3) 3Narrowleaf hawksbeard competes with native species for soilmoisture (J. Snyder pers. com.). It competes successfully with haycrops (J. Conn pers. com.).Thicket-forming/Smothering growth form (0–2) 0Narrowleaf hawksbeard does not form dense thickets (Lapinapers. obs.).Germination requirements (0–3) 1Narrowleaf hawksbeard has been observed germinating in areaswith anthropogenic and natural disturbances (M. Shephardpers. obs.). It can germinate in established hayfields (Royer andDickinson 1999, J. Conn pers. obs.).Other invasive species in the genus (0–3) 3Crepis capillaris (L.) Wallr. is declared noxious in Minnesota(Invaders Database System 2003).Aquatic, wetland or riparian species (0–3) 1Narrowleaf hawksbeard can be found on cultivated fields,pastures, forage stands, fallow land, roadsides, and railroads(Royer and Dickinson 1999, SAFRR 1984). It is established alongthe Knik River (M. Shephard pers. com.).Total for Biological Characteristics and Dispersal 17/25Ecological Amplitude and Distribution ScoreHighly domesticated or a weed of agriculture (0–4) 4Narrowleaf hawksbeard is a weed of agricultural fields (MAFRI2004, Royer and Dickinson 1999).Known level of impact in natural areas (0–6) 1Narrowleaf hawksbeard is not considered as an invader of naturalareas (Densmore et al. 2001). However, this taxon degrades anumber of habitat types in the Pacific Northwest; it persists indisperse populations in disturbed headlands, grasslands, andclearcuts (M.L. Carlson pers. obs.), additionally it is knownto invade and persist following forest fires in interior Alaska(Villano 2007).B-28