Source: California Invasive Plant Council


URL of this page: http://www.cal-ipc.org/site/paf/468
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Cal-IPC Plant Assessment Form

For use with "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands"
by the California Invasive Plant Council and the Southwest Vegetation Management Association

Table 1. Species and Evaluator Information

Species name
(Latin binomial):
The official Latin binomial name for this species. Specify only one name here. Additional species names may go into the Synonyms field.

Acroptilon repens

Synonyms:
Additional Latin binomial names for this species. Separate multiple names with a ; character. Please avoid narrative descriptions, and list only the binomial names.
Centaurea repens
Common names:
Common names for this species. Separate multiple names with a ; character.
Russian knapweed, hardheads, creeping knapweed, mountain bluet, Turkestan thistle
Evaluation date:
The date(s) when this species PAF was filled out, modified, or reviewed. This is free-form text, so it may include multiple dates or other notes.
07/20/04
Evaluator #1 Rob Wilson, Weed Ecology/Cropping Systems Farm Advisor
UCCE Cooperative Extension
707 Nevada St. Susanville, CA 96130
530-251-8132
rgwilson@ucdavis.edu
Evaluator #2 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
Committee review date: 8/27/2004
List date:
Re-evaluation date(s):
General comments
on this assessment:
Enter any additional notes about this assessment, such as factors affecting the reliability or completeness of the answers, likely affects of impacts, or research which is not specific to California but is still relevant in the evaluation of this species.

Table 2. Criteria, Section, and Overall Scores

Overall Score

Plant scoring matrix
Based on letter scores from Sections 1 through 3 below

ImpactInvasivenessDistribution
AA BAnyHighNo Alert
AC DAnyModerateAlert
BA BA BModerateNo Alert
BA BC DModerateAlert
BC DAnyLimitedNo Alert
CAA BModerateNo Alert
CAC DLimitedNo Alert
CBAModerateNo Alert
CBB DLimitedNo Alert
CCAnyLimitedNo Alert
DAnyAnyNot ListedNo Alert

Moderate

Alert Status

Plant scoring matrix
Based on letter scores from Sections 1 through 3 below

ImpactInvasivenessDistributionAlert
AA or BC or DAlert
BA or BC or DAlert

No Alert

Documentation

The total documentation score is the average
of Documentation scores given in Table 2.

Reviewed Scientific Publication4 points
Other Published Material3 points
Observational2 points
Anecdotal1 points
Unknown or No Information0 points

3.2 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 1.1Q 1.2Q 1.3Q 1.4Score
AAAnyAnyA
ABA,BAnyA
ABC,D,UAnyB
AC,D,UAnyAnyB
BAAAnyA
BABAA
BAB,CB-D,UB
BAC,D,UAA
BAC,D,UB-D,UB
BBAAA
BC,D,UAAB
BB-DAB-D,UB
BB-DB-D,UAnyB
BD,UC,D,UA-BB
BD,UC,D,UC,D,UC
C-D,UAAAnyA
CBAAnyB
CA,BB-D,UAnyB
CC,D,UAnyAnyC
DA,BBAnyB
DA,BC,D,UAnyC
DCAnyAnyC
DD,UAnyAnyD
UAB,CAnyB
UB,CA,BAnyB
UB,CC,D,UAnyC
UUAnyAnyU


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 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.
B. Moderate Reviewed Scientific Publication
Invasiveness
Section 2 Scoring Matrix
Total pointsScore
17-21A
11-16B
5-10C
0-4D
More than two U’sU


Total Points
14

Total Score
B
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. 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 3.1Q 3.2Score
AA, BA
AC,D,UB
BAA
BB,CB
BDC
CA,BB
CC,DC
DAB
DB,CC
DDD
A,BUC
C,DUD
UUU


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

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".
Short citations may be used in this table. List full citations at end of this table.

Section 1: Impact

Other Published Material B 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.
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

Reviewed Scientific Publication A 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.
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.

Reviewed Scientific Publication B 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.
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.

Anecdotal D 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.
Identify impacts:
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

Reviewed Scientific Publication B 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.
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.

Reviewed Scientific Publication A 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
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.

Other Published Material B 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
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.

Reviewed Scientific Publication A Question 2.4 Innate reproductive potential
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
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.

Reviewed Scientific Publication B 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.
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.

Reviewed Scientific Publication C 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.
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.

Observational C 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.
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.

Section 3: Distribution

Observational A 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.
Describe ecological amplitude, identifying date of source information and approximate date of introduction to the state, if known:
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.

Observational D 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.
Describe distribution:
More common in northern California, but not widespread at the present time.

Sources of information:
Wilson, R. and DiTomaso, J.M. - observational

Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Yes, 1 points
Dense infestations produce >1,000 viable seed per square meter Yes, 2 points
Populations of this species produce seeds every year. Yes, 1 points
Seed production sustained over 3 or more months within a population annually No
Seeds remain viable in soil for three or more years Yes, 2 points
Viable seed produced with both self-pollination and cross-pollination Yes, 1 points
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes Yes, 1 points
Fragments easily and fragments can become established elsewhere Yes, 2 points
Resprouts readily when cut, grazed, or burned Yes, 1 points
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).
Note any related traits:
Return to Table 2

Worksheet B - Arizona Ecological Types is not included here


Worksheet C - California Ecological Types
 
(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 Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrub
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrubD. < 5%
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparral
Grasslands, Vernal Pools, coastal prairie
Meadows, and other Herbvalley and foothill grasslandD. < 5%
CommunitiesGreat Basin grasslandD. < 5%
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forestD. < 5%
riparian woodlandD. < 5%
riparian scrub (incl.desert washes)D. < 5%
Woodlandcismontane woodland
piñon and juniper woodlandD. < 5%
Sonoran thorn woodland
Forestbroadleaved upland forestD. < 5%
North Coast coniferous forest
closed cone coniferous forest
lower montane coniferous forestD. < 5%
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth)  
Distribution (highest score)  
Return to Table 2

Addendum J - Jepson Regions Infested
 
Click here for a map of Jepson regions

Infested Jepson Regions:
Check the boxes to indicate the Jepson floristic provinces in which this species is found.














Addendum L - External Links & Resources

Cal-IPC Plant Profile
The Cal-IPC Plant Profile for this species.
http://www.cal-ipc.org/ip/management/plant_profiles/Acroptilon_repens.php
Calflora Plant Profile:
The Calflora Plant Profile for this species.
http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=92
CalWeedMapper:
Load CalWeedMapper with this species already selected.
http://calweedmapper.cal-ipc.org/maps/?species=1