Plant Assessment Form
More Bromus diandrus resources
Bromus diandrus
Synonyms: B. rigidus, B. rigidus var gussonei, B. gussonei
Common Names: ripgut brome; great brome; ripgut grass
Evaluated on: 7/20/04
List committee review date: 27/08/2004
Re-evaluation date:
Evaluator(s)
Guy Kyser / Staff Research Associate
Weed Science Group, University of California, Davis
University of California, 1 Shields Ave., Davis, CA 95616
530-752-8284
gbkyser@ucdavis.edu
Joseph M. DiTomaso
University of California
University of California, 1 Shields Ave., Davis, CA 95616
530-754-8715
ditomaso@vegmail.ucdavis.edu
List committee members
Joe DiTomaso
Peter Warner
Alison Stanton
Jake Sigg
John Randall
Cynthia Roye
General Comments
Bromus diandrus is a medium threat according to the rubric, although I began the survey with the prejudice that it should rank higher. I looked at the effect of raising 1.2 to an "A" or of raising Section 2 to an "A" - unlikely in that it would require 4 more points - and in either case the rating would stay the same.
Much of the information referenced here comes from Kon & Blacklow's 1989 review; in most cases they credit multiple previous authors. I will refer to Kon & Blacklow rather than repeat their citations.
|
|
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 |
3.5 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 |
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
BBBD
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.
|
B. Moderate |
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 |
Other Published Material |
|
| 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
12
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
|
B. Increases less rapidly |
Observational |
| 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
|
C. Stable |
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.
|
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.
|
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.
|
B. Occasional |
Observational |
| 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 |
Other Published Material |
|
| 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 |
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
|
| 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.
|
A. High |
Other Published Material |
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
Reviewed Scientific Publication
|
Identify ecosystem processes impacted:
hydrology; fire occurrence/severity B. diandrus has high water use efficency allowing late season growth, and it produces abundant potential fuel which can increase frequency or severity of fires. Generally does not form monotypic stands, so it does not cause the type of impact characteristic of other annual grasses, such as medusahead. These effects are reversible.
Sources of information:
Bicak, C. J. and D. Sternberg. 1993. Water relations of an annual grass, Bromus diandrus, in the Central Valley of California. Bull. Southern California Acad. Sci. 92:54-63.
DiTomaso, J.M., and G.B. Kyser. 2004. Observations in Yolo, Yuba, and San Benito counties, 1998 to present (jmditomaso@ucdavis.edu, gbkyser@ucdavis.edu).
Gordon, D. R. and K. J. Rice. 1993. Competitive effects of grassland annuals on soil water and blue oak (Quercus douglasii) seedlings. Ecology 74:68-82.
Gordon, D. R. and K. J. Rice. 1992. Partitioning of space and water between two California annual grassland species. American Journal of Botany 79:967-976.
Holmes, T. H. and K. J. Rice. 1996. Patterns of growth and soil-water utilization in some exotic annuals and native perennial bunchgrasses of California. Annals of Botany 78:233-243.
Kon, K.F., and Blacklow, W.M. 1989. The biology of Australian weeds. 19. Bromus diandrus Roth and B. rigidus Roth. Plant Protection Quarterly 4:52-61.
|
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.
|
B
Reviewed Scientific Publication
|
Identify type of impact or alteration:
interferes with establishment and survival of native plant seedlings. B. diandrus competes with other plants for water and nutrients, often establishs dense stands, and hosts various plant diseases. However it generally does not form exclusionary monocultures.
Sources of information:
Gordon, D. R. and K. J. Rice. 1993. Competitive effects of grassland annuals on soil water and blue oak (Quercus douglasii) seedlings. Ecology 74:68-82.
Kon, K.F., and Blacklow, W.M. 1989. The biology of Australian weeds. 19. Bromus diandrus Roth and B. rigidus Roth. Plant Protection Quarterly 4:52-61.
Rice, K. J. and E. S. Nagy. 2000. Oak canopy effects on the distribution patterns of two annual grasses: the role of competition and soil nutrients. American Journal of Botany 87:1699-1706
|
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:
physical injury to ruminants; decreased quality of late season forage, but if good forage in spring. B. diandrus' sharp florets can cause damage to eyes, mouth, feet, and intestines of grazing animals, plus it is poor late season forage. Impacts to faunal populations are probably persistent but low intensity.
Sources of information:
DiTomaso, J.M., and E.A. Healy. 2005. Weeds of California (in press).
Kon, K. F. and W. M. Blacklow. 1989. The biology of Australian weeds. 19. Bromus diandrus Roth and B. rigidus Roth. Plant Protection Quarterly 4:52-61.
|
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
Other Published Material
|
Some native Bromus species, but not known to hybridize with natives.
Sources of information:
Hickman, J. (ed.) 1993. The Jepson Manual. UC 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.
|
B
Observational
|
Describe role of disturbance:
Soil disturbance, both anthropogenic (cultivation, construction, livestock) and natural (rooting and other disturbances by animals), contributes to establishment. May establish in undisturbed areas on gaps, burrow mounds, etc. B. diandrus may establish in natural areas on gaps, burrow mounds, etc.
Sources of information:
DiTomaso, J.M., and E.A. Healy. 2005. Weeds of California (in press).
DiTomaso, J.M., and G.B. Kyser. 2004. Observations in Yolo, Yuba, and San Benito counties, 1998 to present (jmditomaso@ucdavis.edu, gbkyser@ucdavis.edu).
Kon, K. F. and W. M. Blacklow. 1989. The biology of Australian weeds. 19. Bromus diandrus Roth and B. rigidus Roth. Plant Protection Quarterly 4:52-61.
|
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
|
B
Observational
|
Describe rate of spread:
As discussed above - B. diandrus is opportunistic and occupies gaps and disturbed areas. It spreads locally, but slowly.
Sources of information:
DiTomaso, J.M., and E.A. Healy. 2005. Weeds of California (in press).
DiTomaso, J.M., and G.B. Kyser. 2004. Observations in Yolo, Yuba, and San Benito counties, 1998 to present (jmditomaso@ucdavis.edu, gbkyser@ucdavis.edu).
Kon, K. F. and W. M. Blacklow. 1989. The biology of Australian weeds. 19. Bromus diandrus Roth and B. rigidus Roth. Plant Protection Quarterly 4:52-61.
|
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
|
C
Other Published Material
|
Describe trend:
B. diandrus already occupies pretty much its entire potential range in California thus is not increasing in area, nor is management making much of an impact. The statewide population is relatively stable.
Sources of information:
CalFlora. 2004. Accessed July 2004 at http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=1200.
DiTomaso, J.M., and G.B. Kyser. 2004. Observations in Yolo, Yuba, and San Benito counties, 1998 to present (jmditomaso@ucdavis.edu, gbkyser@ucdavis.edu).
|
Question 2.4 Innate reproductive potential?
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
|
B
Reviewed Scientific Publication
|
Describe key reproductive characteristics:
Reaches reproductive maturity in 1 year; dense infestations produce >1000 seed/square meter; populations produce seed every year; seed is produced only during a short period; seed has a soil viability of less than 3 years; can both self- and cross-pollinate; cannot reproduce vegetatively. Moderate reproductive potential: seeds heavily, but with a short seed life, and no vegetative reproduction.
Sources of information:
Cheam, A.H. 1987. Longevity of Bromus diandrus Roth seed in soil at three sites in Western Australia. Plant Protection Quarterly 2:137-139.
Kon, K. F. and W. M. Blacklow. 1989. The biology of Australian weeds. 19. Bromus diandrus Roth and B. rigidus Roth. Plant Protection Quarterly 4:52-61.
|
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
|
Identify dispersal mechanisms:
Sharp awned florets stick to clothing, to fur of domestic animals, and in crevices in machinery; can be spread as contaminant in crop seed Moderate human dispersal: is dispersed by accident, not by any systematic process.
Sources of information:
DiTomaso, J.M., and E.A. Healy. 2005. Weeds of California (in press).
DiTomaso, J.M., and G.B. Kyser. 2004. Observations in Yolo, Yuba, and San Benito counties, 1998 to present (jmditomaso@ucdavis.edu, gbkyser@ucdavis.edu).
Kon, K. F. and W. M. Blacklow. 1989. The biology of Australian weeds. 19. Bromus diandrus Roth and B. rigidus Roth. Plant Protection Quarterly 4:52-61
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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.
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B
Observational
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Identify dispersal mechanisms:
Florets stick to fur, feathers, and feet of animals and birds. No mechanisms to promote effective abiotic dispersal. Natural dispersal over long distances can occur but would require seeds attaching to wide-ranging animals such as deer, puma, etc.
Sources of information:
DiTomaso, J.M., and E.A. Healy. 2005. Weeds of California (in press).
DiTomaso, J.M., and G.B. Kyser. 2004. Observations in Yolo, Yuba, and San Benito counties, 1998 to present (jmditomaso@ucdavis.edu, gbkyser@ucdavis.edu).
Kon, K. F. and W. M. Blacklow. 1989. The biology of Australian weeds. 19. Bromus diandrus Roth and B. rigidus Roth. Plant Protection Quarterly 4:52-61.
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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
Other Published Material
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Identify other regions:
none known B. diandrus seems limited to habitats similar to those it occupies in California; moreover, it appears already to occupy most of the appropriate sites here.
Sources of information:
CalFlora. 2004. Accessed July 2004 at http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=1200.
Kon, K. F. and W. M. Blacklow. 1989. The biology of Australian weeds. 19. Bromus diandrus Roth and B. rigidus Roth. Plant Protection Quarterly 4:52-61.
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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.
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A
Other Published Material
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B. diandrus is documented in 45 out of 52 counties and is probably present in the remainder. Found in most California habitats with the exception of alpine, rainforest, and marsh / aquatic. Herbarium specimens include collections from desert, coastal, forest, woodland, scrub, and grassland communities.
Sources of information:
CalFlora. 2004. Accessed July 2004 at http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=1200
DiTomaso, J.M., and G.B. Kyser. 2004. Observations in northern and central California, 1998 to present (jmditomaso@ucdavis.edu, gbkyser@ucdavis.edu).
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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.
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A
Other Published Material
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Describe distribution:
B. diandrus is most prevalent in scrub, grassland, and woodland.
Sources of information:
CalFlora. 2004. Accessed July 2004 at http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=1200.
DiTomaso, J.M., and G.B. Kyser. 2004. Observations in northern and central California, 1998 to present (jmditomaso@ucdavis.edu, gbkyser@ucdavis.edu).
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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 |
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:
Seed is relatively large and highly viable.
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 | C, 5% - 20% |
| desert | D, < 5% |
| interior | B, 20% - 50% |
| Scrub and Chaparral | coastal bluff scrub | A, > 50% |
| coastal scrub | A, > 50% |
| Sonoran desert scrub | C, 5% - 20% |
| Mojavean desert scrub (incl. Joshua tree woodland) | B, 20% - 50% |
| Great Basin scrub | A, > 50% |
| chenopod scrub | B, 20% - 50% |
| montane dwarf scrub | U, Unknown |
| Upper Sonoran subshrub scrub | A, > 50% |
| chaparral | A, > 50% |
| Grasslands, Vernal Pools, Meadows, and other Herb Communities | coastal prairie | A, > 50% |
| valley and foothill grassland | A, > 50% |
| Great Basin grassland | A, > 50% |
| vernal pool | D, < 5% |
| meadow and seep | U, Unknown |
| alkali playa | U, Unknown |
| pebble plain | U, Unknown |
| Bog and Marsh | bog and fen | |
| marsh and swamp | |
| Riparian and Bottomland habitat | riparian forest | D, < 5% |
| riparian woodland | C, 5% - 20% |
| riparian scrub (incl.desert washes) | B, 20% - 50% |
| Woodland | cismontane woodland | A, > 50% |
| piñon and juniper woodland | A, > 50% |
| Sonoran thorn woodland | U, Unknown |
| Forest | broadleaved upland forest | A, > 50% |
| North Coast coniferous forest | U, Unknown |
| closed cone coniferous forest | B, 20% - 50% |
| lower montane coniferous forest | A, > 50% |
| upper montane coniferous forest | C, 5% - 20% |
| subalpine coniferous forest | D, < 5% |
| Alpine Habitats | alpine boulder and rock field | |
| alpine dwarf scrub | |
|
Amplitude (breadth): |
A |
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Distribution (highest score): |
A |
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
