Plant Assessment Form

Dactylis glomerata

Common Names: orchard grass

Evaluated on: 4/4/05

List committee review date: 08/07/2005

Re-evaluation date:

Evaluator(s)

Jeffrey Corbin
UC Berkeley
Dept. of Integrative Biology, University of CA, Berkeley, CA 94720-3140
510-643-4993, 510-703-4904
corbin@berkeley.edu
Joseph DiTomaso
University of California-Davis
Dept. Plant Sci., Mail Stop 4, Davis, CA 95616
530-754-8715
jmditomaso@ucdavis.edu

List commitee members

Carla Bossard
John Randall
Carri Pirosko
Dan Gluesenkamp
Gina Skurka
Brianna Richardson

General Comments

Joe: Check scores for 1.2, 3.1, and 3.2

Table 2. Criteria, Section, and Overall Scores

Overall Score? Limited
Alert Status? No Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes D Observational
Impact?
Four-part score DCDD Total Score
C
1.2 ?Impact on plant community C. Minor Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels D. Negligible
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 Reviewed Scientific Publication
2.3 ?Recent trend in total area infested within state C. Stable Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
B. Moderate Other Published Material
2.5 ?Potential for human-caused dispersal A. High Reviewed Scientific Publication
2.6 ? Potential for natural long-distance dispersal C. Rare Other Published Material
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 B
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low 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? D Observational
Identify ecosystem processes impacted:

Not well-studied, but likely no impacts


Sources of information:

DiTomaso, observational


Question 1.2 Impact on plant community composition,
structure, and interactions?
C Reviewed Scientific Publication
Identify type of impact or alteration:

Can is infrequent circumstances displace native perennial grasses. Dactylis has been shown to invade oak woodlands (Williamson and Harrison 2002), serpentine habitats (Williamson and Harrison 2002), and also appears to be an emerging threat in coastal prairie grasslands (Corbin and D'Antonio in prep). Not usually a problem and seldom in high densities.


Sources of information:

Williamson, J. and S. Harrison (2002). "Biotic and abiotic limits to the spread of exotic revegetation species." Ecological Applications 12(1): 40-51.
Corbin and D"Antonio in prep - unpublished paper, to be submitted to Madrono.
Corbin, J. 2004. Out of the frying pan: Invasion of exotic perennial grasses in coastal prairies. Jeffrey D. Corbin, Department of Integrative Biology, UC Berkeley. Presentation at the California Invasive Plant Council Symposium. Available: http://groups.ucanr.org/ceppc/Symposia/2004_Presentations.htm


Question 1.3 Impact on higher trophic levels? D
Identify type of impact or alteration:

Not known. The thatch may be poor forage, but not known. Fresh grass considered good forage and is commonly used in pastures.


Sources of information:

Very little info.


Question 1.4 Impact on genetic integrity? D Other Published Material

None known and no native Dactylis in California.


Sources of information:

Hickman. 1993. The Jepson Manual.


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
B Reviewed Scientific Publication
Describe role of disturbance:

Disturbed areas at McLaughlin Reserve saw great invasion of Dactylis (Williamson and Harrison). It has also invaded an undisturbed coastal prairie grassland (Corbin and D'Antonio in prep)


Sources of information:

See above


Question 2.2 Local rate of spread with no management? B Reviewed Scientific Publication
Describe rate of spread:

Significant increase in its cover during 4 year sampling at Tom's Point Preserve (Corbin and D'Antonio in prep). LIkely not spreading fast enough to warrant an "A".


Sources of information:

Williamson, J. and S. Harrison (2002). "Biotic and abiotic limits to the spread of exotic revegetation species." Ecological Applications 12(1): 40-51.
Corbin and D"Antonio in prep - unpublished paper, to be submitted to Madrono. .


Question 2.3 Recent trend in total area infested within state? C Observational
Describe trend:

This invasion may be relatively recent - within the last 30 years or so, but infestations in the state seem to be static.


Sources of information:

DiTomaso, observational


Question 2.4 Innate reproductive potential? B Other Published Material
Describe key reproductive characteristics:

Reaches maturity quickly, and spreads via rhyzomes.


Sources of information:

Corbin, J. personal observations
DiTomaso and Healy. 2006. Weeds of California. UC DANR Pub. #3488.


Question 2.5 Potential for human-caused dispersal? A Reviewed Scientific Publication
Identify dispersal mechanisms:

Along roadways - e.g. McLaughlin reserve (Williamson and Harrison 2002). It is likely a component of forage as well.


Sources of information:

Williams and Harrison 2002.


Question 2.6 Potential for natural long-distance dispersal? C Other Published Material
Identify dispersal mechanisms:

Very light seeds, that likely easily attach to animals in mud, but vast majority of seed fall directly to soil surface below parent plant.


Sources of information:

DiTomaso and Healy. 2006. Weeds of California. UC DANR Pub. #3488.


Question 2.7 Other regions invaded? C Reviewed Scientific Publication
Identify other regions:

British Columbia and Spain


Sources of information:

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

Dactylis has been shown to invade oak woodlands (Williamson and Harrison 2002), serpentine habitats (Williamson and Harrison 2002), and also appears to be an emerging threat in coastal prairie grasslands (Corbin and D'Antonio in prep)


Sources of information:

CalFlora: Information on California plants for education, research and conservation. [web application]. 2004. Albany, California: The CalFlora Database [a non-profit organization]. Available: http://www.calflora.org/.
Williamson and Harrison 2002.
Jeff Corbin, personal observations


Question 3.2 Distribution/Peak frequency? D Observational
Describe distribution:

Grassland, oak woodland.


Sources of information:

Very little data about the range of potential habitats. It is widespread in the state (CALFLORA).


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Yes
Dense infestations produce >1,000 viable seed per square meter No
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 No
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes Yes
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned Yes
Total points: 4
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 scrub
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieD, < 5%
valley and foothill grasslandD, < 5%
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)
Woodlandcismontane woodlandD, < 5%
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forestD, < 5%
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): B
Distribution (highest score): D

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