Question A-5: What are the current patterns of distribution of weedy or invasive plant species in the Assessment Area? Where in the area are invasive species most likely to be of concern for restoration management?
Exotic and invasive plants, known as noxious weeds, are alien species that are deemed detrimental to an environmentally sound ecosystem. They are usually introduced to an area, often from a different continent, and would not occur there naturally. Once in the area they can be further spread by people, cars and trucks, and domestic animals. Noxious weeds usually compete aggressively with native plants and can take over entire native plant communities. They are very adaptable species and therefore, very difficult to control once introduced into the ecosystem. There is currently a management plan for the Pike and San Isabel National Forests which identifies the preferred methods of control of these species.
Map V-8. Distributions of Exotic or Invasive Plant Species. This map shows known locations and potential habitats of exotic and invasive plants. |
Exotic and invasive plant species that occur or are likely to occur in the Assessment Area were identified as target species for this study. Exhibit 10 presents the species and their preferred habitat and elevation range. Appendix G discusses the methodology for identification of these species. Map V-8 shows the distributions of potential and known locations.
Exhibit 10.Noxious Weeds of Concern in the Assessment Area
Noxious
Weed |
Place of Origin |
Elevation |
Examples of Preferred Habitat |
Canada Thistle |
Eurasia and North Africa |
4,000-9,500 |
Open meadows, ponderosa pine savannas, roadsides, fields, pastures and other disturbed areas. Prefers rich, heavy and dry soils. Does not tolerate water-logged or poorly aerated soils |
Dalmation Toadflax |
Southeastern Europe - Mediterranean Region. Introduced to North America as an ornamental |
5,000 - 6,500 |
Oak, aspen, sagebrush, mountain brush, and riparian communities on roadsides, rangeland, waste places, cultivated fields, and semi-arid regions. Tolerates low temperatures and coarse textured soils |
Diffuse Knapweed |
Eurasia |
NA |
Readily colonizes a wide range of soils |
Downy Broam |
Eurasia and Mediterranean |
4,000 - 9,000 |
Roadsides, waste areas, pastures, rangelands. Also occurs in open slopes, sagebrush, pinyon/juniper, and less commonly, aspen and conifer communities. Does not tolerate heavy soils |
Field Bindweed |
Europe - thought to have been introduced in wheat from Turkey |
4,000 - 10,000 |
Common on roadsides, very adaptable. Prefers rich somewhat sandy and basic soils |
Houndstongue |
Europe |
5,000 - 9,000 |
Usually found in pastures, waste fields, and bare and disturbed patches of stony or sandy ground. Prefers gravely, somewhat limey soils |
Kochia |
Europe |
up to 8,500 |
Roadsides, waste places, fields |
Leafy Spurge |
Europe |
5,000 - 6,500 |
Prefers open habitats, roadsides, waste areas, pastures, cultivated fields, irrigation ditches, disturbed sites, rangelands, fields etc. Tolerant of wide range of conditions |
Musk Thistle |
Southern Europe and western Asia |
NA |
Disturbed sites along roads, fields, pastures spreading into sagebrush, pinyon juniper and mountain brush communities. Prefers dry, gravely soils and very abundant on fertile soils |
Russian Knapweed* |
Europe |
4,500 - 7,500 |
Roadsides, waste areas, cultivated fields, fence rows, ditch banks. Very adaptable and difficult to control |
Russian Thistle |
Eurasia |
up to 8,500 |
Wide variety of habitats. Dry plains, cultivated fields, waste places, roadsides. Adapted to disturbed land |
Salt Cedar |
Eurasia and Africa - introduced as an ornamental shrub in early 1800s |
NA |
Disturbed and undisturbed streams, waterways, bottomlands, banks, and drainage washes. Also moist rangelands and patures. Seedlings require saturated soils. Tolerates highly saline soils and alkali conditions. |
Spotted Knapweed |
Europe - Introduced as contaminant of alfalfa and clover seed |
NA |
Includes habitats dominated by ponderosa pine and Douglas-fir as well as foothill prairie habitats. Found in light, porous fertile, well-drained and often calcareous soils in warm areas. |
Hoary Cress |
Europe - Introduced in alfalfa seed |
3,500 - 8,500 |
Waste places, cultivated fields, pastures. Vigorous growth on irrigated alkaline soils |
Yellow Toadflax |
Eurasia - escaped as an ornamental |
6,000 - 8,500 |
Waste places, pastures, roadsides, cultivated fields, meadows and gardens. Occurs in a wide variety of habitats but is limited in wet or dark conditions. Occurs mostly on sandy/gravely soils, but also common on chalky soils. |
* Considered a serious noxious weed due to difficulty of control and eradication and is one of four plants that must be managed in accordance with the Colorado Weed Management Act. |
|||
Several of the species listed in Exhibit 10 have become common invasive plants in burned areas (Buffalo Creek Fire), out-competing native plants and reducing forage value. There have been extensive efforts to combat their spread. The species that have been noted in burned areas include leafy spurge, kochia, salt cedar, defuse knapweed, Canada thistle, musk thistle, yellow toad flax, and Russian thistle. See Appendix G for a discussion of current distribution of invasive plants.
