Invasiveness Ranking System for Non-Native Plants of Alaska

2.9. Aquatic, wetland, or riparian species.Aquatic weeds have a history of more problematic invasions (see Galatowitsch et al. 1999, Pheloung et al. 1999). Additionally,riparian habitats display high connectivity and tend to be of great conservation concern in Alaska, and we therefore rank thosespecies with an intermediate value.A. Not invasive in wetland communities. 0B. Invasive in riparian communities. 1C. Invasive in wetland communities. 3U. UnknownShowing the possible range of responses and values of impacts. Justifications of questions are presented below each subsection in italics.Table 4. Excerpt of the distribution section of the Alaska invasiveness ranking system3. Distribution.3.1. Is the species highly domesticated or a weed of agriculture.Cultivated species are generally planted in high volumes and bred for environmental conditions in novel regions, making theprobability of escape into native habitats higher. An intermediate score is given to species that are common weeds of agriculture,since these species not only pose an economic impact, but have numerous opportunities to transition from the agricultural fields tobordering natural areas.A. No 0B. Is occasionally an agricultural pest. 2C. Has been grown deliberately, bred, or is known as a significant agricultural pest. 4U. Unknown3.2. Known level of ecological impact in natural areas.This point concerns how similar habitats are to those in Alaska and the degree of the ecological impacts in other regions. This pointis based on a question from the Southwest Exotic Plants system (Hiebert and Studdendieck 1993). Species that are known to havesevere impacts to habitats similar to those found in Alaska are given the highest score, while those species whose impacts are severefor somewhat dissimilar habitats or whose impacts are less for similar habitats are given lower scores.A. Not known to cause impact in any other natural area. 0B. Known to cause impacts in natural areas, but in dissimilar habitats and climate zones than exist in regions 1of Alaska.C. Known to cause low impact in natural areas in similar habitats and climate zones to those present in3Alaska.D. Known to cause moderate impact in natural areas in similar habitat and climate zones. 4E. Known to cause high impact in natural areas in similar habitat and climate zones. 6U. Unknown3.3. Role of anthropogenic and natural disturbance in establishment.Species with a habit of invading natural areas are clearly more dangerous than those restricted to the anthropogenic footprint (seeRejmanek 2001).A. Requires anthropogenic disturbances to establish. 0B. May occasionally establish in undisturbed areas but can readily establish in areas with natural3disturbances.C. Can establish independent of any known natural or anthropogenic disturbances. 5U. Unknown14