Plant Assessment Form
More Elymus caput-medusae resources
Elymus caput-medusae
Synonyms: Taeniatherum caput-medusae
Common Names: medusahead
Evaluated on: 3/8/03
List committee review date: 10/02/2003
Re-evaluation date:
Evaluator(s)
Joe DiTomaso
UC Davis
Weed Science Program, Robbins Hall, Univ. California, Davis CA 95616
530-754-8715
DiTomaso@vegmail.ucdavis.edu
List committee members
Carla Bossard
John Randall
Peter Warner
Doug Johnson
John Hall
Dana Backer
Cindy Roye
Matt Brooks
General Comments
Removed second scientific name, Taeniatherum caput-medusae, and added it to the synonym line 3/28/17. Ramona Robison
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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 |
High
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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
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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 |
3.5 out of 5 |
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Score |
Documentation |
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| 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.
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A. Severe |
Reviewed Scientific Publication |
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
AAAD
Total Score
A
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| 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.
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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.
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A. Severe |
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.
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D. None |
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| 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.
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A. Severe |
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
17
Total Score
A
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| 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
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A. Increases rapidly |
Other Published Material |
| 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
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A. Increasing rapidly |
Reviewed Scientific Publication |
| 2.4 |
?Innate reproductive potential
(see Worksheet A)
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
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B. Moderate |
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.
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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.
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A. Frequent |
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.
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C. Already invaded |
Reviewed Scientific Publication |
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| 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.
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A. Widespread |
Other Published Material |
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
A
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| 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.
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B. Moderate |
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.
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A
Reviewed Scientific Publication
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Identify ecosystem processes impacted:
Increases litter density, utilized shallow soil moisture, and increases frequency of fire. The dense litter cover enhances medusahead germination, may exclude native species, ties up soil nutrients, and contributes to fire danger in the summer. High silica content reduced the rate of tissue decomposition and can lead to 2-5 inches of litter build-up. This heavy thatch delays soil warming in spring, allow nutrient cycling, and prevents seed penetration into the soil surface.
Sources of information:
Miller, A.C., D. Clausnitzer and M.M. Borman. 1999. Medusahead. In, Biology and Management of Noxious Rangeland Weeds. Eds. R.L. Sheley and J.K. Petroff. Oregon State Univ. Press, Corvallis; Bovey, R.W., D. LeTourneau and L.C. Erickson. 1961. The chemical composition of medusahead and downy brome. Weeds 9:307-311; Hironaka, M. 1994. Medusahead: natural successor to the cheatgrass type in the northern Great Basin. Pages 89-91, In Proc. Sym. On Ecology, Management, and Restoration of Intermountain Annual Rangelands. Ogden, UT; Evans, R.A. and J.A. Young. 1970. Plant litter and establishment of alien annual weed species in rangeland communities. Weed Science 18:697-703
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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.
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A
Reviewed Scientific Publication
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Identify type of impact or alteration:
Medusaahead is considered to be the most threatening of the invasive annual grass species to rangeland production and wildand plant diversity in California, Idaho and Oregon. Can form near monotypic stands with this thick thatch layer. Medusahead effectively removes available soil water at depths where native grass roots grow. These characteristics confer an advantage in fall establishment and allows medusahead to compete successfully for soil moisture.
Sources of information:
George, M.R. 1992. Ecology and management of medusahead. Range Sci Rept. Dept. Agron. And Range Sci. Agr. Exp. Stat. Series #32, 3 pp.; Harris, G.A. 1977. Root phenology as a factor of competition among grass seedlings. J. Range Manage. 30:172-177; Young, J.A. 1992. Ecology and management of medusahead (Taeniatherum caput-medusae ssp. asperum [Simk.] Melderis). Great Basin Naturalist 52:245-252; Harris, G.A. and A. M. Wilson. 1970. Competition for moisture among seedlings of annual and perennial grasses as influenced by root elongation at low temperature. Ecology 51:530-534; Lusk, W.C., M.B. Jones, D.T. Torell, and C.M. McKell. 1961. Medusahead palatability. J. Range Management 14:248-251
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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.
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A
Reviewed Scientific Publication
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Identify type of impact or alteration:
It has low palatability to wildlife and can reduce grazing capacity by as much as 50% due to the high silica content. The long awned seeds often injure animals foraging later in the season when the inflorescence is present. Provides very little food to livestock and wildlife because of the high silica content and long awns.
Sources of information:
Miller, A.C., D. Clausnitzer and M.M. Borman. 1999. Medusahead. In, Biology and Management of Noxious Rangeland Weeds. Eds. R.L. Sheley and J.K. Petroff. Oregon State Univ. Press, Corvallis; Goebel, C.J. and G. Berry. 1976 Selectivity of range grass seeds by local birds. J. Range Manage. 29:393-395; Young, J.A. 1992. Ecology and management of medusahead (Taeniatherum caput-medusae ssp. asperum [Simk.] Melderis). Great Basin Naturalist 52:245-252
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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.
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D
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None Not expected to impact genetic integrity of native species. No natives within this genus in North America. Somewhat related to Elymus, but no evidence that they hybridize.
Sources of information:
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| 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.
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A
Other Published Material
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Describe role of disturbance:
Can readily move into disturbed grass or scrublands, either mechanical disturbance or overgrazing. Can also move into undisturbed areas. Medusahead threatens rangelands with sparse native plant communities, as well as more complex communities degraded by overgrazing, fire, or cultivation, particularly Artemisia/Agropyron/Poa dominated communities. Reported that 30 years of protection from livestock grazing did not prevent medusahead invasion in Lassen County. Unpublished data by DiTomaso indicate that it can move into native undisturbed scrubland.
Sources of information:
Miller, A.C., D. Clausnitzer and M.M. Borman. 1999. Medusahead. In, Biology and Management of Noxious Rangeland Weeds. Eds. R.L. Sheley and J.K. Petroff. Oregon State Univ. Press, Corvallis; Wagner, J.A., R.E. Delmas and J.A. Young. 2001. 30 years of medusahead: return to Fly Brown Flat. Rangelands 23(3):6-9; Dahl, B.E. and E.W. Tisdale. 1975. Environmental factors related to medusahead distribution. J. Range Manage. 28:463-468
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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
Other Published Material
|
Describe rate of spread:
Can spread very rapidly once it gets a foothold. Populations can double in far less than 10 years. Current estimates for medusahead distribution in the Great Basin or northeastern California, extending across Modoc and Lassen Counties, are approximately 5 million acres.
Sources of information:
Miller, A.C., D. Clausnitzer and M.M. Borman. 1999. Medusahead. In, Biology and Management of Noxious Rangeland Weeds. Eds. R.L. Sheley and J.K. Petroff. Oregon State Univ. Press, Corvallis
|
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
|
A
Reviewed Scientific Publication
|
Describe trend:
In 1950, it occurred in 6 counties and by 1990s was in 20 counties and as far south as Riverside County. Today, observations estimate it occupies more than a million acres of annual-dominated grassland, oak woodland, and chaparral communities in California. Although is has been suggested that all suitable sites in California are occupied, this is probably only true in the northeastern part of the state. Medusahead appears to be rapidly spreading in the southern Sierra Nevada foothills and the coast ranges.
Sources of information:
Young, J.A. 1992. Ecology and management of medusahead (Taeniatherum caput-medusae ssp. asperum [Simk.] Melderis). Great Basin Naturalist 52:245-252
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Question 2.4 Innate reproductive potential?
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
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B
Reviewed Scientific Publication
|
Describe key reproductive characteristics:
Germination rates are very high and dormancy is short. Plant density after establishment may range from 500 plants per square foot on scublands to 2000 plants per square foot on valley bottom soils. Like most winter annual grasses. Produces high number of seeds every year. Seedbanks, however, appear to persist for only about 2 years, with very little surviving 3 or more years.
Sources of information:
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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.
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B
Reviewed Scientific Publication
|
Identify dispersal mechanisms:
Long distance dispersal is primarily by travel in coats of livestock, especially sheep. Sees can also be dispersed by attaching to machinery, vehicles, and clothing. Long awns attach to many things, including animals, humans and objects.
Sources of information:
Furbish, P. 1953. Control of medusahead on California ranges. J. Forestry 51:118-121
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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.
|
A
Reviewed Scientific Publication
|
Identify dispersal mechanisms:
Local dispersal from established patches is by wind and water, but primarily by animals. As with livestock, medusahead can attach to the hair and fur of wildlife and disperse long distances. Awns facilitate long distance dispersal.
Sources of information:
|
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.
|
C
Reviewed Scientific Publication
|
Identify other regions:
First introduced to Oregon as a seed contaminant around 1887. Major problem in the interior valleys of Oregon, but also a problem in Nevada, Idaho, Utah, Washington and Colorado. Although invasive in other areas of the west, it occupies similar sites in California as it does in these other states.
Sources of information:
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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
Other Published Material
|
First introduced to the US in Oregon in 1884. Reached the Sacramento Valley of California by 1900. Also occurs in the Central West region. Most widespread in the grassland and scrubland of the Great Basin region.
Sources of information:
Miller, A.C., D. Clausnitzer and M.M. Borman. 1999. Medusahead. In, Biology and Management of Noxious Rangeland Weeds. Eds. R.L. Sheley and J.K. Petroff. Oregon State Univ. Press, Corvallis; Maurer, T., M.J. Russo and A. Godell. 1988. Medusahead. The Nature Conservancy. Element of Stewardship Abstract http://tncweeds.ucdavis.edu/esadocs/Taencapu.html
Eric Wylde, Santa Clara Weed Management Area
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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.
|
B
Observational
|
Describe distribution:
Today, observations estimate it occupies more than a million acres of annual-dominated grassland, oak woodland, and chaparral communities in California. It is most common in Northeastern California, but is expanding range along the coastal and Sierra Nevada foothills. Primarily found in open areas with high light.
Sources of information:
Miller, A.C., D. Clausnitzer and M.M. Borman. 1999. Medusahead. In, Biology and Management of Noxious Rangeland Weeds. Eds. R.L. Sheley and J.K. Petroff. Oregon State Univ. Press, Corvallis; Kan, T. and O. Pollack. 2000. Taeniatherum caput-medusae. In, Invasive Plants of Californias Wildlands. Eds. C. Bossard, J. Randall, M. Hoshovsky. UC Press, Berkeley
|
| 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 |
No |
| Viable seed produced with both self-pollination and cross-pollination |
Yes |
| Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes |
No |
| Fragments easily and fragments can become established elsewhere |
No |
| Resprouts readily when cut, grazed, or burned |
No |
| Total points: |
5
|
| Total unknowns: |
0 |
| Total score: |
B?
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).
|
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 | D, < 5% |
| Sonoran desert scrub | |
| Mojavean desert scrub (incl. Joshua tree woodland) | |
| Great Basin scrub | B, 20% - 50% |
| chenopod scrub | |
| montane dwarf scrub | |
| Upper Sonoran subshrub scrub | |
| chaparral | C, 5% - 20% |
| Grasslands, Vernal Pools, Meadows, and other Herb Communities | coastal prairie | C, 5% - 20% |
| valley and foothill grassland | B, 20% - 50% |
| Great Basin grassland | |
| vernal pool | |
| meadow and seep | |
| alkali playa | |
| pebble plain | |
| Bog and Marsh | bog and fen | |
| marsh and swamp | |
| Riparian and Bottomland habitat | riparian forest | |
| riparian woodland | |
| riparian scrub (incl.desert washes) | D, < 5% |
| Woodland | cismontane woodland | B, 20% - 50% |
| piñon and juniper woodland | |
| Sonoran thorn woodland | |
| Forest | broadleaved upland forest | |
| North Coast coniferous forest | |
| closed cone coniferous forest | |
| lower montane coniferous forest | |
| upper montane coniferous forest | |
| subalpine coniferous forest | |
| Alpine Habitats | alpine boulder and rock field | |
| alpine dwarf scrub | |
|
Amplitude (breadth): |
A |
|
Distribution (highest score): |
B |
Infested Jepson Regions
Click here for a map of Jepson regions
- Cascade Range
- Great Valley
- Northwest
- Sierra Nevada
- Southwest
- Modoc Plateau
- Sierra Nevada East
