Invasiveness Ranking System for Non-Native Plants of Alaska

Feasibility of ControlScoreSeed banks (0–3) 0Seeds remain viable in the soil for less than 1 year (Tu 2002). Ina study in Oregon seed viability dropped to less than 2% after 2years in the soil (Thomas Kaye pers. com.).Vegetative regeneration (0–3) 2False brome can resprout from a small stem or root fragmentswhen cut. It is fire tolerant and is able to resprout within 2 weeksafter a burn (Cal-IPC 2005, Kaye 2002).Level of effort required (0–4) 3Removal of the entire plant by digging is effective for smallinfestations, but is extremely time and labor-intensive. Repeatedmowing, grazing, or burning may eliminate seed production.Herbicides can be applied late in the season after most otherspecies are dormant (Kaye 2001, Tu 2002).Total for Feasibility of Control 5/10Total score for 4 sections 69/98§Bromus inermis ssp. inermis Leyss.Ranking SummaryEcoregion known or expected to occur inSouth CoastalInterior BorealArctic AlpineYesYesYesPotential Max. ScoreEcological Impact 40 20Biological Characteristics and Dispersal 25 16Amplitude and Distribution 25 18Feasibility of Control 10 8Relative Maximum 62Climatic ComparisonCollected inAlaska regions?CLIMEXsimilarity?South Coastal Yes –Interior Boreal Yes –Arctic Alpine Yes –Bromus inermis ssp. inermis has been reported from all ecoregionsof Alaska (Hultén 1968, Densmore et al. 2001).Ecological ImpactScoreImpact on Ecosystem Processes (0–10) 5Smooth brome may inhibit natural succession processes(Densmore et al. 2001, Rutledge and McLendon 1996).Impact on Natural Community Structure (0–10) 5Establishes in an existing layer, increasing the density of the layerand reducing the density of shorter herbaceous layers (I. Lapinaand M.L. Carlson pers obs.).Impact on Natural Community Composition (0–10) 5It forms a dense sod that may eliminate other species, thuscontributing to the loss of species diversity in natural areas(Butterfield et al. 1996, Rutledge and McLendon 1996). In recentyears Bromus inermis has largely replaced B. pumpellianus andcertain other native species (Elliott 1949).Impact on Higher Trophic Levels (0–10) 5Smooth brome has high palatability for grazing animals (USDA2002). It is an alternate host for the viral diseases of crops (Sather1987, Royer and Dickinson 1999). In southern Alaska hybridswarms with B. inermis ssp. pumpelliana occur (Elliott 1949,Hultén 1968).Total for Ecological Impact 20/40common names: smooth bromeBiological Characteristics and Dispersal ScoreMode of Reproduction (0–3) 3Bromus inermis reproduces by rhizomes and seeds. The numberof seeds produced has a very wide range. Each plant is capableof producing 156–10,080 viable seeds (Butterfield et al. 1996,Sather 1987). In studies by McKone (1985) Bromus inermis hadsignificantly lower average seed set (17.2 per plant). Reproductivepotential in Alaska is unknown.Long-distance dispersal (0–3) 1Seeds may be transported short distances by wind and ants(Rutledge and McLendon 1996, Sather 1987).Spread by humans (0–3) 3Smooth brome, often planted as a forage crop, persists aftercultivation and infests surrounding vegetation. It is spread whensoil containing rhizomes is moved (Densmore et al. 2001).Allelopathic (0–2) 0There is no known allelopathy potential. (USDA 2002).Competitive Ability (0–3) 2Smooth brome is a highly competitive weed in agricultural fields(Butterfield et al. 1996). In Alaska its competitiveness is largelyrestricted to sunny sites with nutrient rich mesic soils (J. Connpers. com.).Thicket-forming/Smothering growth form (0–2) 2It forms a dense sod that often excludes other species (Butterfieldet al. 1996, Rutledge and McLendon 1996). Stands are very denseand often greater than 1 m tall (M.L. Carlson pers. obs.)Germination requirements (0–3) 2Butterfield et al. (1996) suggests this species establishes inundisturbed or lightly disturbed areas, while Densmore etal. (2001) indicate it requires open soil and disturbance forgermination.Other invasive species in the genus (0–3) 3Bromus arenarius Labill., B. briziformis Fischer and C. Meyer,B. diandrus Roth, B. japonicus Thunb. ex Murr., B. hordeaceusL., B. madritensis L., B. secalinus L., B. stamineus Desv., B. sterilisL., B. tectorum L., and B. trinii Desv. (Wilken and Painter 1993,Royer and Dickinson 1999, USDA 2002).Aquatic, wetland or riparian species (0–3) 0Smooth brome is a weed of roadsides, forests, prairies, fields,lawns, and lightly disturbed sites (Butterfield et al. 1996,Rutledge and McLendon 1996).Total for Biological Characteristics and Dispersal 16/25B-8