Plant Assessment Form

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 commitee 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.

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? No Alert
Documentation? 3.5 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes B Reviewed Scientific Publication
Impact?
Four-part score BBBD Total Score
B
1.2 ?Impact on plant community B. Moderate Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels B. Moderate Reviewed Scientific Publication
1.4 ?Impact on genetic integrity D. None Other Published Material
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Reviewed Scientific Publication
Invasiveness?
Total Points
12 Total Score B
2.2 ?Local rate of spread with no management B. Increases less rapidly Observational
2.3 ?Recent trend in total area infested within state C. Stable Other Published Material
2.4 ?Innate reproductive potential
(see Worksheet A)
B. Moderate Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal B. Moderate Reviewed Scientific Publication
2.6 ? Potential for natural long-distance dispersal B. Occasional Observational
2.7 ?Other regions invaded C. Already invaded Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
A. Widespread Other Published Material
Distribution?
Total Score A
3.2 ?Distribution/Peak frequency
(see Worksheet C)
A. High Other Published Material

Table 3. Documentation

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? 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?
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? 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? 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?
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? 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? 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? 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? 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


Question 2.6 Potential for natural long-distance dispersal? B Observational
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.


Question 2.7 Other regions invaded? C Other Published Material
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.


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? A Other Published Material

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).


Question 3.2 Distribution/Peak frequency? A Other Published Material
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).


Worksheet A - Innate reproductive potential

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?

Related traits:

Seed is relatively large and highly viable.

Worksheet B - Arizona Ecological Types is not included here

Worksheet C - California Ecological Types

(sensu Holland 1986)
Major Ecological Types Minor Ecological Types Code?
Marine Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
estuariesD, < 5%
DunescoastalC, 5% - 20%
desertD, < 5%
interiorB, 20% - 50%
Scrub and Chaparralcoastal bluff scrubA, > 50%
coastal scrubA, > 50%
Sonoran desert scrubC, 5% - 20%
Mojavean desert scrub (incl. Joshua tree woodland)B, 20% - 50%
Great Basin scrubA, > 50%
chenopod scrubB, 20% - 50%
montane dwarf scrubU, Unknown
Upper Sonoran subshrub scrubA, > 50%
chaparralA, > 50%
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieA, > 50%
valley and foothill grasslandA, > 50%
Great Basin grasslandA, > 50%
vernal poolD, < 5%
meadow and seepU, Unknown
alkali playaU, Unknown
pebble plainU, Unknown
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forestD, < 5%
riparian woodlandC, 5% - 20%
riparian scrub (incl.desert washes)B, 20% - 50%
Woodlandcismontane woodlandA, > 50%
piñon and juniper woodlandA, > 50%
Sonoran thorn woodlandU, Unknown
Forestbroadleaved upland forestA, > 50%
North Coast coniferous forestU, Unknown
closed cone coniferous forestB, 20% - 50%
lower montane coniferous forestA, > 50%
upper montane coniferous forestC, 5% - 20%
subalpine coniferous forestD, < 5%
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): A
Distribution (highest score): A

Infested Jepson Regions

Click here for a map of Jepson regions

  • ALL
  • CA Floristic Province
  • Cascade Range
  • Central West
  • Desert Province
  • Mojave Desert
  • Sonoran Desert
  • Great Basin Province
  • Great Valley
  • Modoc Plateau
  • Northwest
  • Sierra Nevada
  • Sierra Nevada East
  • Southwest