Plant Assessment Form

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 commitee 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

Table 2. Criteria, Section, and Overall Scores

Overall Score? High
Alert Status? No Alert
Documentation? 3.5 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes A Reviewed Scientific Publication
Impact?
Four-part score AAAD Total Score
A
1.2 ?Impact on plant community A. Severe Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels A. Severe Reviewed Scientific Publication
1.4 ?Impact on genetic integrity D. None
2.1 ?Role of anthropogenic and natural disturbance in establishment A. Severe Reviewed Scientific Publication
Invasiveness?
Total Points
17 Total Score A
2.2 ?Local rate of spread with no management A. Increases rapidly Other Published Material
2.3 ?Recent trend in total area infested within state A. Increasing rapidly Reviewed Scientific Publication
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 A. Frequent Reviewed Scientific Publication
2.7 ?Other regions invaded C. Already invaded Reviewed Scientific Publication
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)
B. Moderate Observational

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? A Reviewed Scientific Publication
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


Question 1.2 Impact on plant community composition,
structure, and interactions?
A Reviewed Scientific Publication
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


Question 1.3 Impact on higher trophic levels? A Reviewed Scientific Publication
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


Question 1.4 Impact on genetic integrity? D

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:

Unknown


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
A Other Published Material
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


Question 2.2 Local rate of spread with no management? 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? 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


Question 2.4 Innate reproductive potential? 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:

Question 2.5 Potential for human-caused dispersal? 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


Question 2.6 Potential for natural long-distance dispersal? 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? 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:

Section 3: Distribution
Question 3.1 Ecological amplitude/Range? 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


Question 3.2 Distribution/Peak frequency? 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 Californias Wildlands. Eds. C. Bossard, J. Randall, M. Hoshovsky. UC Press, Berkeley


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:

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
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrubD, < 5%
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrubB, 20% - 50%
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparralC, 5% - 20%
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieC, 5% - 20%
valley and foothill grasslandB, 20% - 50%
Great Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forest
riparian woodland
riparian scrub (incl.desert washes)D, < 5%
Woodlandcismontane woodlandB, 20% - 50%
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forest
closed cone coniferous forest
lower montane coniferous forest
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine 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