Plant Assessment Form
More Rhaponticum repens resources
Rhaponticum repens
Synonyms: Acroptilon repens, Centaurea repens
Common Names: Russian knapweed, hardheads, creeping knapweed, mountain bluet, Turkestan thistle
Evaluated on: 7/20/04
List committee review date: 27/08/2004
Re-evaluation date:
Evaluator(s)
Rob Wilson, Weed Ecology/Cropping Systems Farm Advisor
UCCE Cooperative Extension
707 Nevada St. Susanville, CA 96130
530-251-8132
rgwilson@ucdavis.edu
Joseph M. DiTomaso/ Cooperative Extension Specialist
University of California
Weed Science Program, Robbins Hall, Davis, CA 95616
530-754-8715
ditomaso@vegmail.ucdavis.edu
List committee members
Peter Warner
Cynthia Roye
Alison Stanton
Jake Sigg
John Randall
Joe DiTomaso
General Comments
No general comments for this species
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|
Overall Score ?
Plant scoring matrix
Based on letter scores from Sections 1 through 3 below
| Impact | Invasiveness | Distribution | | |
| A | A B | Any | High | No Alert |
| A | C D | Any | Moderate | Alert |
| B | A B | A B | Moderate | No Alert |
| B | A B | C D | Moderate | Alert |
| B | C D | Any | Limited | No Alert |
| C | A | A B | Moderate | No Alert |
| C | A | C D | Limited | No Alert |
| C | B | A | Moderate | No Alert |
| C | B | B D | Limited | No Alert |
| C | C | Any | Limited | No Alert |
| D | Any | Any | Not Listed | No Alert |
Moderate
|
Alert Status ?
Plant scoring matrix
Based on letter scores from Sections 1 through 3 below
| Impact | Invasiveness | Distribution | Alert |
| A | A or B | C or D | Alert |
| B | A or B | C or D | Alert |
No Alert
|
Documentation ?
The total documentation score is the average
of Documentation scores given in Table 2.
| Reviewed Scientific Publication | 4 points |
| Other Published Material | 3 points |
| Observational | 2 points |
| Anecdotal | 1 points |
| Unknown or No Information | 0 points |
3 out of 5 |
|
|
Score |
Documentation |
|
| 1.1 |
?Impact on abiotic ecosystem processes
Consider the impact on the natural range and variation of abiotic ecosystem processes and system-wide parameters in ways that significantly diminish the ability of native species to survive and reproduce. Alterations that determine the types of communities that can exist in a given area are of greatest concern. Examples of abiotic processes include:
- fire occurrence, frequency, and intensity;
- geomorphological changes such as erosion and sedimentation rates;
- hydrological regimes, including soil water table;
- nutrient and mineral dynamics, including salinity, alkalinity, and pH;
- light availability (e.g. when an aquatic invader covers an entire water body that would otherwise be open).
Select the one letter below that best describes this species' most severe impact on an abiotic ecosystem process:
A. Severe, possibly irreversible, alteration or disruption of an ecosystem process.
B. Moderate alteration of an ecosystem process.
C. Minor alteration of an ecosystem process.
D. Negligible perceived impact on an ecosystem process.
U. Unknown.
|
B. Moderate |
Other Published Material |
Impact?
| Section 1 Scoring Matrix |
|---|
| Q 1.1 | Q 1.2 | Q 1.3 | Q 1.4 | Score |
| A | A | Any | Any | A |
| A | B | A,B | Any | A |
| A | B | C,D,U | Any | B |
| A | C,D,U | Any | Any | B |
| B | A | A | Any | A |
| B | A | B | A | A |
| B | A | B,C | B-D,U | B |
| B | A | C,D,U | A | A |
| B | A | C,D,U | B-D,U | B |
| B | B | A | A | A |
| B | C,D,U | A | A | B |
| B | B-D | A | B-D,U | B |
| B | B-D | B-D,U | Any | B |
| B | D,U | C,D,U | A-B | B |
| B | D,U | C,D,U | C,D,U | C |
| C-D,U | A | A | Any | A |
| C | B | A | Any | B |
| C | A,B | B-D,U | Any | B |
| C | C,D,U | Any | Any | C |
| D | A,B | B | Any | B |
| D | A,B | C,D,U | Any | C |
| D | C | Any | Any | C |
| D | D,U | Any | Any | D |
| U | A | B,C | Any | B |
| U | B,C | A,B | Any | B |
| U | B,C | C,D,U | Any | C |
| U | U | Any | Any | U |
Four-part score
BABD
Total Score
B
|
| 1.2 |
?Impact on plant community
Consider the cumulative ecological impact of this species to the plant communities it invades. Give more weight to changes in plant composition, structure, and interactions that involve rare or keystone species or rare community types. Examples of severe impacts include:
- formation of stands dominated (>75% cover) by the species;
- occlusion (>75% cover) of a native canopy, including a water surface, that eliminates or degrades layers below;
- significant reduction or extirpation of populations of one or more native species.
Examples of impacts usually less than severe include:
- reduction in propagule dispersal, seedling recruitment, or survivorship of native species;
- creation of a new structural layer, including substantial thatch or litter, without elimination or replacement of a pre-existing layer;
- change in density or depth of a structural layer;
- change in horizontal distribution patterns or fragmentation of a native community;
- creation of a vector or intermediate host of pests or pathogens that infect native plant species.
Select the one letter below that best describes this species' impact on community composition, structure and interactions:
A. Severe alteration of plant community composition, structure, or interactions.
B. Moderate alteration of plant community composition.
C. Minor alteration of community composition.
D. Negligible impact known; causes no perceivable change in community composition, structure, or interactions.
U. Unknown.
|
A. Severe |
Reviewed Scientific Publication |
| 1.3 |
?Impact on higher trophic levels
Consider the cumulative impact of this species on the animals, fungi, microbes, and other organisms in the communities that it invades. Although a non-native species may provide resources for one or a few native species (e.g. by providing food, nesting sites, etc.), the ranking should be based on the species' net impact on all native species. Give more weight to changes in composition and interactions involving rare or keystone species or rare community types.
Examples of severe impacts include:
- extirpation or endangerment of an existing native species or population;
- elimination or significant reduction in native species' nesting or foraging sites, cover, or other critical resources (i.e., native species habitat), including migratory corridors.
Examples of impacts that are usually less than severe include:
- minor reduction in nesting or foraging sites, cover, etc. for native animals;
- minor reduction in habitat connectivity or migratory corridors;
- interference with native pollinators;
- injurious components, such as awns or spines that damage the mouth and gut of native wildlife species, or production of anti-digestive or acutely toxic chemical that can poison native wildlife species.
Select the one letter below that best describes this species' impact on community composition and interactions:
A. Severe alteration of higher trophic populations, communities, or interactions.
B. Moderate alteration of higher trophic level populations, communities, or interactions.
C. Minor alteration of higher trophic level populations, communities or interactions.
D. Negligible impact; causes no perceivable change in higher trophic level populations, communities, or interactions.
E. Unknown.
|
B. Moderate |
Reviewed Scientific Publication |
| 1.4 |
?Impact on genetic integrity
Consider whether the species can hybridize with and influence the proportion of individuals with non-native genes within populations of native species. Mechanisms and possible outcomes include:
- production of fertile or sterile hybrids that can outcompete the native species;
- production of sterile hybrids that lower the reproductive output of the native species.
Select the one letter below that best describes this species' impact on genetic integrity:
A. Severe (high proportion of individuals).
B. Moderate (medium proportion of individuals).
C. Minor (low proportion of individuals).
D. No known hybridization.
U. Unknown.
|
D. None |
Anecdotal |
|
| 2.1 |
?Role of anthropogenic and natural disturbance in establishment
Assess dependence on disturbance, both human and natural, for establishment of this species in wildlands. Examples of anthropogenic disturbances include:
- grazing, browsing, and rooting by domestic livestock and feral animals;
- altered fire regimes, including fire suppression;
- cultivation;
- silvicultural practices;
- altered hydrology due to dams, diversions, irrigation, etc.;
- roads and trails;
- construction;
- nutrient loading from fertilizers, runoff, etc.
Examples of natural disturbance include:
- wildfire;
- floods;
- landslides;
- windthrow;
- native animal activities such as burrowing, grazing, or browsing.
Select the first letter in the sequence below that describes the ability of this species to invade wildlands:
A. Severe invasive potential: this species can establish independent of any known natural or anthropogenic disturbance.
B. Moderate invasive potential: this species may occasionally establish in undisturbed areas but can readily establish in areas with natural disturbances.
C. Low invasive potential: this species requires anthropogenic disturbance to establish.
D. No perceptible invasive potential: this species does not establish in wildlands (though it may persist from former cultivation).
U. Unknown.
|
B. Moderate |
Reviewed Scientific Publication |
Invasiveness?
| Section 2 Scoring Matrix |
| Total points | Score |
| 17-21 | A |
| 11-16 | B |
| 5-10 | C |
| 0-4 | D |
| More than two U's | U |
Total Points
14
Total Score
B
|
| 2.2 |
?Local rate of spread with no management
Assess rate of spread in existing localized infestations where the proportion of available habitat invaded is still small when no management measures are implemented.
Select the one letter below that best describes the rate of spread:
A. Increases rapidly (doubling in <10 years)
B. Increases, but less rapidly
C. Stable
D. Declining
U. Unknown
|
A. Increases rapidly |
Reviewed Scientific Publication |
| 2.3 |
?Recent trend in total area infested within state
Assess the overall trend in the total area infested by this species statewide. Include current management efforts in this assessment and note them.
Select the one letter below that best describes the current trend:
A. Increasing rapidly (doubling in total range statewide in <10 years)
B. Increasing, but less rapidly
C. Stable
D. Declining
U. Unknown
|
B. Increasing less rapidly |
Other Published Material |
| 2.4 |
?Innate reproductive potential
(see Worksheet A)
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
|
A. High |
Reviewed Scientific Publication |
| 2.5 |
?Potential for human-caused dispersal
Assess whether this species is currently spread: or has high potential to be spread: by direct or indirect human activity. Such activity may enable the species to overcome natural barriers to dispersal that would not be crossed otherwise, or it may simply increase the natural dispersal of the species. Possible mechanisms for dispersal include:
- commercial sales for use in agriculture, ornamental horticulture, or aquariums;
- use as forage, erosion control, or revegetation;
- presence as a contaminant (seeds or propagules) in bulk seed, hay, feed, soil, packing materials, etc.;
- spread along transportation corridors such as highways, railroads, trails, or canals;
- transport on boats or boat trailers.
Select the one letter below that best describes human-caused dispersal and spread:
A. High: there are numerous opportunities for dispersal to new areas.
B. Moderate: human dispersal occurs, but not at a high level.
C. Low: human dispersal is infrequent or inefficient.
D. Does not occur.
U. Unknown.
|
B. Moderate |
Reviewed Scientific Publication |
| 2.6 |
? Potential for natural long-distance dispersal
We have chosen 1 km as the threshold of "long-distance." Assess whether this species is frequently spread, or has high potential to be spread, by animals or abiotic mechanisms that can move seed, roots, stems, or other propagules this far. The following are examples of such natural long-distance dispersal mechanisms:
- the species' fruit or seed is commonly consumed by birds or other animals that travel long distances;
- the species' fruits or seeds are sticky or burred and cling to feathers or hair of animals;
- the species has buoyant fruits, seeds, or other propagules that are dispersed by flowing water;
- the species has light propagules that promote long-distance wind dispersal;
- The species, or parts of it, can detach and disperse seeds as they are blown long distances (e.g., tumbleweed).
Select the one letter below that best describes natural long-distance dispersal and spread:
A. Frequent long-distance dispersal by animals or abiotic mechanisms.
B. Occasional long-distance dispersal by animals or abiotic mechanisms.
C. Rare dispersal more than 1 km by animals or abiotic mechanisms.
D. No dispersal of more than 1 km by animals or abiotic mechanisms.
U. Unknown.
|
C. Rare |
Reviewed Scientific Publication |
| 2.7 |
?Other regions invaded
Assess whether this species has invaded ecological types in other states or countries outside its native range that are analogous to ecological types not yet invaded in your state (see Worksheets B, C, and D for California, Arizona, and Nevada, respectively, in Part IV for lists of ecological types). This information is useful in predicting the likelihood of further spread within your state.
Select the one letter below that best describes the species' invasiveness in other states or countries, outside its native range.
A. This species has invaded 3 or more ecological types elsewhere that exist in your state and are as yet not invaded by this species (e.g. it has invaded Mediterranean grasslands, savanna, and maquis in southern Europe, which are analogous to California grasslands, savanna, and chaparral, respectively).
B. Invades 1 or 2 ecological types that exist but are not yet invaded in your state.
C. Invades elsewhere but only in ecological types that it has already invaded in the state.
D. Not known as an escape anywhere else.
U. Unknown.
|
C. Already invaded |
Observational |
|
| 3.1 |
?Ecological amplitude/Range
(see Worksheet C)
Refer to Worksheet C and select the one letter below that indicates the number of different ecological types that this species invades.
A. Widespread: the species invades at least three major types or at least six minor types.
B. Moderate: the species invades two major types or five minor types.
C. Limited: the species invades only one major type and two to four minor types.
D. Narrow: the species invades only one minor type.
U. Unknown.
|
A. Widespread |
Observational |
Distribution?
| Section 3 Scoring Matrix |
| Q 3.1 | Q 3.2 | Score |
| A | A, B | A |
| A | C,D,U | B |
| B | A | A |
| B | B,C | B |
| B | D | C |
| C | A,B | B |
| C | C,D | C |
| D | A | B |
| D | B,C | C |
| D | D | D |
| A,B | U | C |
| C,D | U | D |
| U | U | U |
Total Score
B
|
| 3.2 |
?Distribution/Peak frequency
(see Worksheet C)
To assess distribution, record the letter that corresponds to the highest percent infested score entered in Worksheet C for any ecological type.
|
D. Very low |
Observational |
Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".
| Section 1: Impact |
Question 1.1 Impact on abiotic ecosystem processes?
Consider the impact on the natural range and variation of abiotic ecosystem processes and system-wide parameters in ways that significantly diminish the ability of native species to survive and reproduce. Alterations that determine the types of communities that can exist in a given area are of greatest concern. Examples of abiotic processes include:
- fire occurrence, frequency, and intensity;
- geomorphological changes such as erosion and sedimentation rates;
- hydrological regimes, including soil water table;
- nutrient and mineral dynamics, including salinity, alkalinity, and pH;
- light availability (e.g. when an aquatic invader covers an entire water body that would otherwise be open).
Select the one letter below that best describes this species' most severe impact on an abiotic ecosystem process:
A. Severe, possibly irreversible, alteration or disruption of an ecosystem process.
B. Moderate alteration of an ecosystem process.
C. Minor alteration of an ecosystem process.
D. Negligible perceived impact on an ecosystem process.
U. Unknown.
|
B
Other Published Material
|
Identify ecosystem processes impacted:
Very little information is available regarding Russian knapweed's affects on abiotic ecosystem processes. Since russian knapweed produces a deep, extensive root system, the plant likely has significant effects on soil moisture levels especially at deeper depths compared to native grassland ecotypes. The plant commonly forms monoculture stands and may influence soil erosion and soil infiltration rates compared to native ecotypes. Russian knapweed is also commonly found in saline/sodic soils and may change soluble salt distributions in the soil profile. Some evidence suggests that it leads to the accumulation of high levels of zinc in the soil surface which can alter the ability for more desirable plants to develop.
Sources of information:
Bottoms, R., C.J.Nelson, T.D. Whitson,and J.H. Coutts. 1999.Factors being considered that make russian knapweed a highly competitive plant. Proc. Western Soc. Weed Sci. 52:73
|
Question 1.2 Impact on plant community composition,
structure, and interactions?
Consider the cumulative ecological impact of this species to the plant communities it invades. Give more weight to changes in plant composition, structure, and interactions that involve rare or keystone species or rare community types. Examples of severe impacts include:
- formation of stands dominated (>75% cover) by the species;
- occlusion (>75% cover) of a native canopy, including a water surface, that eliminates or degrades layers below;
- significant reduction or extirpation of populations of one or more native species.
Examples of impacts usually less than severe include:
- reduction in propagule dispersal, seedling recruitment, or survivorship of native species;
- creation of a new structural layer, including substantial thatch or litter, without elimination or replacement of a pre-existing layer;
- change in density or depth of a structural layer;
- change in horizontal distribution patterns or fragmentation of a native community;
- creation of a vector or intermediate host of pests or pathogens that infect native plant species.
Select the one letter below that best describes this species' impact on community composition, structure and interactions:
A. Severe alteration of plant community composition, structure, or interactions.
B. Moderate alteration of plant community composition.
C. Minor alteration of community composition.
D. Negligible impact known; causes no perceivable change in community composition, structure, or interactions.
U. Unknown.
|
A
Reviewed Scientific Publication
|
Identify type of impact or alteration:
Russian knapweed will commonly form monoculture stands especially in disturbed areas. In open areas, Russian knapweed often spreads aggressively covering over 12m2 within a two year period. Russian knapweed stands are also very persistent with documented infestations dominating a site for >75 years. Russian knapweed is a strong competitor. It can grow in saline/sodic conditions and effectively competes for soil moisture and nutrients with several native plants. Russian knapweed's deep root system allows the plant to mine deep soil moisture that most native grasses and shrub cannot obtain. Russian knapweed is allelopathic and inhibits the growth of several plants. Russian knapweed is also unpalatable to most grazers and tends to dominate rangeland and grazed areas.
Sources of information:
Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Beck, K.G. 2004. Russian Knapweed. Colorado State University Cooperative Extension Fact Sheet. no. 3.111. http://www.ext.colostate.edu
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.
|
Question 1.3 Impact on higher trophic levels?
Consider the cumulative impact of this species on the animals, fungi, microbes, and other organisms in the communities that it invades. Although a non-native species may provide resources for one or a few native species (e.g. by providing food, nesting sites, etc.), the ranking should be based on the species' net impact on all native species. Give more weight to changes in composition and interactions involving rare or keystone species or rare community types.
Examples of severe impacts include:
- extirpation or endangerment of an existing native species or population;
- elimination or significant reduction in native species' nesting or foraging sites, cover, or other critical resources (i.e., native species habitat), including migratory corridors.
Examples of impacts that are usually less than severe include:
- minor reduction in nesting or foraging sites, cover, etc. for native animals;
- minor reduction in habitat connectivity or migratory corridors;
- interference with native pollinators;
- injurious components, such as awns or spines that damage the mouth and gut of native wildlife species, or production of anti-digestive or acutely toxic chemical that can poison native wildlife species.
Select the one letter below that best describes this species' impact on community composition and interactions:
A. Severe alteration of higher trophic populations, communities, or interactions.
B. Moderate alteration of higher trophic level populations, communities, or interactions.
C. Minor alteration of higher trophic level populations, communities or interactions.
D. Negligible impact; causes no perceivable change in higher trophic level populations, communities, or interactions.
E. Unknown.
|
B
Reviewed Scientific Publication
|
Identify type of impact or alteration:
Russian knapweed is generally avoided by grazing animals due to it's bitter taste. Prolonged consumption of Russian knapweed is toxic to horses. Russian knapweed is grazed by bighorn sheep in British Columbia. Birds and rodents eat the seed. The BLM estimates an annual loss of 55% in livestock carrying capacity.
Sources of information:
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Beck, K.G. 2004. Russian Knapweed. Colorado State University Cooperative Extension Fact Sheet. no. 3.111. http://www.ext.colostate.edu
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.
|
Question 1.4 Impact on genetic integrity?
Consider whether the species can hybridize with and influence the proportion of individuals with non-native genes within populations of native species. Mechanisms and possible outcomes include:
- production of fertile or sterile hybrids that can outcompete the native species;
- production of sterile hybrids that lower the reproductive output of the native species.
Select the one letter below that best describes this species' impact on genetic integrity:
A. Severe (high proportion of individuals).
B. Moderate (medium proportion of individuals).
C. Minor (low proportion of individuals).
D. No known hybridization.
U. Unknown.
|
D
Anecdotal
|
The author was not able to find any native plants that might hybridize with Russian knapweed. No plants native to CA are in the Acroptilon or Centaurea genus.
Sources of information:
The Jepson manual. higher plants of California/ James C. Hickman, editor. 1993. Univesity of California Press.
|
| Section 2: Invasiveness |
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
Assess this species' dependence on disturbance: both human and natural: for establishment in wildlands. Examples of anthropogenic disturbances include:
- grazing, browsing, and rooting by domestic livestock and feral animals;
- altered fire regimes, including fire suppression;
- cultivation;
- silvicultural practices;
- altered hydrology due to dams, diversions, irrigation, etc.;
- roads and trails;
- construction;
- nutrient loading from fertilizers, runoff, etc.
Examples of natural disturbance include:
- wildfire;
- floods;
- landslides;
- windthrow;
- native animal activities such as burrowing, grazing, or browsing.
Select the first letter in the sequence below that describes the ability of this species to invade wildlands:
A. Severe invasive potential: this species can establish independent of any known natural or anthropogenic disturbance.
B. Moderate invasive potential: this species may occasionally establish in undisturbed areas but can readily establish in areas with natural disturbances.
C. Low invasive potential: this species requires anthropogenic disturbance to establish.
D. No perceptible invasive potential: this species does not establish in wildlands (though it may persist from former cultivation).
U. Unknown.
|
A
Reviewed Scientific Publication
|
Describe role of disturbance:
Russian knapweed typically invades disturbed, open sites such as roadsides, riverbanks, irrigation ditches, pasture, waste places, and cropland. Russian knapweed does not readily establish/thrive in healthy, natural habitats because it's sensitive to shading and aggressive competition with other plants. Occasionally, Russian knapweed is found growing in healthy native plant communities, especially in ecotypes that lack aggressive plant competition or areas that border sites with recent natural or anthropogenic disturbance. Once established in disturbed areas, Russian knapweed commonly spreads into greasewood habitats in NE California.
Sources of information:
Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Beck, K.G. 2004. Russian Knapweed. Colorado State University Cooperative Extension Fact Sheet. no. 3.111. http://www.ext.colostate.edu
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.
Personal Observations by Rob Wilson.
|
Question 2.2 Local rate of spread with no management?
Assess this species' rate of spread in existing localized infestations where the proportion of available habitat invaded is still small when no management measures are implemented.
Select the one letter below that best describes the rate of spread:
A. Increases rapidly (doubling in <10 years)
B. Increases, but less rapidly
C. Stable
D. Declining
U. Unknown
|
A
Reviewed Scientific Publication
|
Describe rate of spread:
The local spread rate of Russian knapweed varies quite a bit from location to location depending on soil type, soil moisture, disturbance, and the existing plant community. Under favorable conditions, Russian knapweed will spread quite rapidly extending radially in all directions (creeping roots) over 12m2 during a two year period. Tom Whitson claimed an 11% average increase in Russian knapweed populations in Wyoming. The BLM estimates an average annual rate of spread of 8% in the northwestern US.
Sources of information:
Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.
|
Question 2.3 Recent trend in total area infested within state?
Assess the overall trend in the total area infested by this species statewide. Include current management efforts in this assessment and note them.
Select the one letter below that best describes the current trend:
A. Increasing rapidly (doubling in total range statewide in <10 years)
B. Increasing, but less rapidly
C. Stable
D. Declining
U. Unknown
|
B
Other Published Material
|
Describe trend:
Russian knapweed infestations have been documented throughout most of California (32 counties). Russian knapweed invades a wide range of ecosystems, plant communties, and soils, but Russian knapweed's rate of spread in California is quite dependent on location and land-use. Russian knapweed is most invasive on open, distrurbed sites. It will grow on several soil types, but it spreads and thrives best in arid areas with clay soil. It reproduces primarily by root and tends spread at alarming rates following soil disturbance. Russian knapweed populations located in poor growing conditions have remained static with minimal spread, while other infestations growing under optimal conditions have spread at alarming rates. The rating given in this section is based on the author's estimate of average spread throughout the state.
Sources of information:
Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.
|
Question 2.4 Innate reproductive potential?
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
|
A
Reviewed Scientific Publication
|
Describe key reproductive characteristics:
Russian knapweed reproduces by adventitious buds on horizontally spreading roots and by seed. Local infestations increase primarily by shoots arising from the root system. A singe knapweed plant can produce 1,200 seeds per year. Seed viability data differs from 2-3 years up to 9 years under dry storage. Fragmented roots quickly grow into new plants.
Sources of information:
Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.
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Question 2.5 Potential for human-caused dispersal?
Assess whether this species is currently spread: or has high potential to be spread: by direct or indirect human activity. Such activity may enable the species to overcome natural barriers to dispersal that would not be crossed otherwise, or it may simply increase the natural dispersal of the species. Possible mechanisms for dispersal include:
- commercial sales for use in agriculture, ornamental horticulture, or aquariums;
- use as forage, erosion control, or revegetation;
- presence as a contaminant (seeds or propagules) in bulk seed, hay, feed, soil, packing materials, etc.;
- spread along transportation corridors such as highways, railroads, trails, or canals;
- transport on boats or boat trailers.
Select the one letter below that best describes human-caused dispersal and spread:
A. High: there are numerous opportunities for dispersal to new areas.
B. Moderate: human dispersal occurs, but not at a high level.
C. Low: human dispersal is infrequent or inefficient.
D. Does not occur.
U. Unknown.
|
B
Reviewed Scientific Publication
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Identify dispersal mechanisms:
Russian knapweed commonly infests cropland and can be found as a contaminant (seeds and propagules) in hay, straw, and fill dirt. Plants often grow in roadsides, ditches, and parking areas and are spread along transportation corridors.
Sources of information:
Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.
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Question 2.6 Potential for natural long-distance dispersal?
We have chosen 1 km as the threshold of "long-distance." Assess whether this species is frequently spread, or has high potential to be spread, by animals or abiotic mechanisms that can move seed, roots, stems, or other propagules this far. The following are examples of such natural long-distance dispersal mechanisms:
- the species' fruit or seed is commonly consumed by birds or other animals that travel long distances;
- the species' fruits or seeds are sticky or burred and cling to feathers or hair of animals;
- the species has buoyant fruits, seeds, or other propagules that are dispersed by flowing water;
- the species has light propagules that promote long-distance wind dispersal;
- The species, or parts of it, can detach and disperse seeds as they are blown long distances (e.g., tumbleweed).
Select the one letter below that best describes natural long-distance dispersal and spread:
A. Frequent long-distance dispersal by animals or abiotic mechanisms.
B. Occasional long-distance dispersal by animals or abiotic mechanisms.
C. Rare dispersal more than 1 km by animals or abiotic mechanisms.
D. No dispersal of more than 1 km by animals or abiotic mechanisms.
U. Unknown.
|
C
Reviewed Scientific Publication
|
Identify dispersal mechanisms:
Plants generally spread over short distances via root to form dense patches, but plants growing near waterways can easily spread over long distances via propagules and seed washing downstream. However, the plant does not generally grow near water sources. Seasonal high water flow or floods often spread plants over large distances. Seeds may occasionally be spread by rodents and birds.
Sources of information:
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.
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Question 2.7 Other regions invaded?
Assess whether this species has invaded ecological types in other states or countries outside its native range that are analogous to ecological types not yet invaded in your state (see Worksheets B, C, and D for California, Arizona, and Nevada, respectively, in Part IV for lists of ecological types). This information is useful in predicting the likelihood of further spread within your state.
Select the one letter below that best describes the species' invasiveness in other states or countries, outside its native range.
A. This species has invaded 3 or more ecological types elsewhere that exist in your state and are as yet not invaded by this species (e.g. it has invaded Mediterranean grasslands, savanna, and maquis in southern Europe, which are analogous to California grasslands, savanna, and chaparral, respectively).
B. Invades 1 or 2 ecological types that exist but are not yet invaded in your state.
C. Invades elsewhere but only in ecological types that it has already invaded in the state.
D. Not known as an escape anywhere else.
U. Unknown.
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C
Observational
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Identify other regions:
Russian knapweed is wide spread in the western United States and is currently found in at least 412 counties in 21 states.
Sources of information:
Observations by Rob Wilson, Peter Warner, Joe DiTomaso, John Randall, Jake Sigg.
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| Section 3: Distribution |
Question 3.1 Ecological amplitude/Range?
Refer to Worksheet C and select the one letter below that indicates the number of different ecological types that this species invades.
A. Widespread: the species invades at least three major types or at least six minor types.
B. Moderate: the species invades two major types or five minor types.
C. Limited: the species invades only one major type and two to four minor types.
D. Narrow: the species invades only one minor type.
U. Unknown.
|
A
Observational
|
Russian knapweed has wide ecological amplitude and is found in several ecological types. First introduced in California between 1910-1914.
Sources of information:
Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.
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Question 3.2 Distribution/Peak frequency?
To assess distribution, record the letter that corresponds to the highest percent infested score entered in Worksheet C for any ecological type.
|
D
Observational
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Describe distribution:
More common in northern California, but not widespread at the present time.
Sources of information:
Wilson, R. and DiTomaso, J.M. - observational
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| Reaches reproductive maturity in 2 years or less |
Yes |
| Dense infestations produce >1,000 viable seed per square meter |
Yes |
| Populations of this species produce seeds every year. |
Yes |
| Seed production sustained over 3 or more months within a population annually |
No |
| Seeds remain viable in soil for three or more years |
Yes |
| Viable seed produced with both self-pollination and cross-pollination |
Yes |
| Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes |
Yes |
| Fragments easily and fragments can become established elsewhere |
Yes |
| Resprouts readily when cut, grazed, or burned |
Yes |
| Total points: |
11
|
| Total unknowns: |
0 |
| Total score: |
A?
Scoring Criteria for Worksheet A
A. High reproductive potential (6 or more points).
B. Moderate reproductive potential (4-5 points).
C. Low reproductive potential (3 points or less and less than 3 Unknowns).
U. Unknown (3 or fewer points and 3 or more Unknowns).
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Related traits:
Worksheet B - Arizona Ecological Types is not included here
(sensu Holland 1986)
| Major Ecological Types |
Minor Ecological Types |
Code?
A means >50% of type occurrences are invaded;
B means 20% to 50%;
C means 5% to 20%;
D means present but <5%;
U means unknown (unable to estimate percentage of occurrences invaded)
|
| Marine Systems | marine systems | |
| Freshwater and Estuarine | lakes, ponds, reservoirs | |
| Aquatic Systems | rivers, streams, canals | |
| estuaries | |
| Dunes | coastal | |
| desert | |
| interior | |
| Scrub and Chaparral | coastal bluff scrub | |
| coastal scrub | |
| Sonoran desert scrub | |
| Mojavean desert scrub (incl. Joshua tree woodland) | |
| Great Basin scrub | D, < 5% |
| chenopod scrub | |
| montane dwarf scrub | |
| Upper Sonoran subshrub scrub | |
| chaparral | |
| Grasslands, Vernal Pools, Meadows, and other Herb Communities | coastal prairie | |
| valley and foothill grassland | D, < 5% |
| Great Basin grassland | D, < 5% |
| vernal pool | |
| meadow and seep | |
| alkali playa | |
| pebble plain | |
| Bog and Marsh | bog and fen | |
| marsh and swamp | |
| Riparian and Bottomland habitat | riparian forest | D, < 5% |
| riparian woodland | D, < 5% |
| riparian scrub (incl.desert washes) | D, < 5% |
| Woodland | cismontane woodland | |
| piñon and juniper woodland | D, < 5% |
| Sonoran thorn woodland | |
| Forest | broadleaved upland forest | D, < 5% |
| North Coast coniferous forest | |
| closed cone coniferous forest | |
| lower montane coniferous forest | D, < 5% |
| upper montane coniferous forest | |
| subalpine coniferous forest | |
| Alpine Habitats | alpine boulder and rock field | |
| alpine dwarf scrub | |
|
Amplitude (breadth): |
A |
|
Distribution (highest score): |
D |
Infested Jepson Regions
Click here for a map of Jepson regions
- CA Floristic Province
- Cascade Range
- Central West
- Great Valley
- Northwest
- Sierra Nevada
- Southwest
- Great Basin Province
- Modoc Plateau
- Sierra Nevada East
- Desert Province
- Mojave Desert
- Sonoran Desert
