Invasiveness Ranking System for Non-Native Plants of Alaska

Feasibility of ControlScoreSeed banks (0–3) 3The seeds of sheep sorrel are long-lived. They remained viable formore than 6–7 years in the soil (Chippindale and Milton 1934,Steinbauer and Grigsby 1958). In a Massachusetts study sheepsorrel was not present in the ground cover of 80-year old pinestands, but viable seeds were found in soil samples. Presumablyviable seeds remained buried in the soil since earlier successionalstages (Livingston and Allessio 1968).Vegetative regeneration (0–3) 2Sheep sorrel is able to survive severe fire and resprout fromrhizomes and roots (Granström and Schimmel 1993).Level of effort required (0–4) 2Control of sheep sorrel can be difficult because of its creepingrhizomes and long-lived seeds. Plants are too low to be affectedby mowing or grazing. It usually survives prescribed burning.Repeated cultivation and frequent removal of resprouted plantswill eventually exhaust the population. Several herbicides areavailable for be used in pastures and lawns; however, sheepsorrel is resistant to several herbicides (Putwain and Harper1970). Liming the soil may help eradicate sheep sorrel (Rutledgeand McLendon 1996). Densmore et al. (2001) suggested thateradication of sheep sorrel is not necessary, because it usuallydoes not persist when shaded out by other vegetation.Total for Feasibility of Control 7/10Total score for 4 sections 51/100§Rumex crispus L.common names: curly dockR. obtusifolius L. bitter dockR. longifolius DC. dooryard dockRanking SummaryEcoregion known or expected to occur inSouth CoastalInterior BorealArctic AlpinePotentialYesYesYesScoreMax.Ecological Impact 40 10Biological Characteristics and Dispersal 25 16Amplitude and Distribution 25 14Feasibility of Control 10 8Relative Maximum 48Climatic ComparisonRumexcrispus L.CollectedRumexobtusifoliusL. CollectedRumexlongifoliusDC. CollectedCLIMEXsimilarity?South Coastal Yes Yes Yes –Interior Boreal Yes No Yes YesArctic Alpine Yes No Yes YesRumex crispus and R. longifolius are documented from allecogeographic regions of Alaska. Rumex obtusifolius is knownfrom the south coastal ecogeographic region (Hultén 1968, UAM2004, AKEPIC 2005). Rumex obtusifolius: Using the CLIMEXmatching program, the climatic similarity between Nome andother areas where the species is documented is fairly high. Therange of the species includes Chirka-Kem’ and Arkhangel’sk,Russia (Gubanov et al. 2003), which have a 77% and 76% climaticmatch with Nome respectively. The range of R. obtusifoliusalso includes Røros and Dombås, Norway (Lid and Lid 1994),which has 76% and 63% climatic matches with Nome and 55%and 52% climatic matches with Fairbanks, respectively. Thusestablishment of R. obtusifolius in interior boreal and arctic alpineecogeographic regions of Alaska may be possible.Ecological ImpactScoreImpact on Ecosystem Processes (0–10) 1The impact of exotic docks on ecosystem processes has not beendocumented. However, population densities of exotic docksin natural or seminatural habitats of Alaska are currently lowenough that likely only minor ecosystem functions are affected(M.L. Carslon pers. obs.).Impact on Natural Community Structure (0–10) 3Curly dock is capable of changing the density of the existing layerof vegetation (I. Lapina pers. obs.).Impact on Natural Community Composition (0–10) 3Curly and bitter docks likely reduce the number of individuals inone or more native species in the community (Cal-IPC 2003).Impact on Higher Trophic Levels (0–10) 3The seeds and vegetation of docks can be toxic to animals(Royer and Dickinson 1999). Bitter dock is avoided by rabbits,but it appears to be a favorite food of deer (Amphlett and Rea1909, cited in Cavers and Harper 1964). Dock species are alsoan alternate host for number of viruses, fungi (Dal Bello andCarranza 1995), and nematodes (Edwards and Taylor 1963,Townshend and Davidson 1962). Hybrids between many speciesof the subgenus Rumex commonly occur. Although these hybridsare largely sterile, they can produce some viable seeds (Caversand Harper 1964).Total for Ecological Impact 10/40Biological Characteristics and Dispersal ScoreMode of Reproduction (0–3) 3Plants reproduce by seeds. The number of seeds per plant mayvary from less than 100 to more than 40,000 for curly dock andmore than 60,000 for bitter dock per season (Cavers and Harper1964). Stevens (1932) reported 29,500 seeds per plant for curlydock and 23,000 seeds per plant for bitter dock. Damage plantscan resprout from underground parts (Cavers and Harper 1964).B-111