Plant Assessment Form

Acacia dealbata

Synonyms: Acacia decurrens var. dealbata

Common Names: silver wattle

Evaluated on: 1/4/07

List committee review date: 14/02/2007

Re-evaluation date:

Evaluator(s)

Joseph M. DiTomaso, UC Specialist
University of California
Dept Plant Sci., Mail Stop 4, Davis CA 95616
530-754-8715
jmditomaso@ucdavis.edu
Andrea Williams
415-331-0639
Andrea_Williams@nps.gov

List commitee members

Joe DiTomaso
Peter Warner
Joanna Clines

General Comments

There is very little information available on this species. For more information, contact Andrea Williams, Stassia Samuels (Stassia_Samuels@nps.gov) or Bobbi Simpson (Bobbi_Simpson@nps.gov)

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? No Alert
Documentation? 2.5 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes B Observational
Impact?
Four-part score BBBD Total Score
B
1.2 ?Impact on plant community B. Moderate Observational
1.3 ?Impact on higher trophic levels B. Moderate Other Published Material
1.4 ?Impact on genetic integrity D. None Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Observational
Invasiveness?
Total Points
15 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 B. Increasing less rapidly Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High Other Published Material
2.5 ?Potential for human-caused dispersal A. High Other Published Material
2.6 ? Potential for natural long-distance dispersal C. Rare Observational
2.7 ?Other regions invaded B. Invades 1 or 2 ecological types Other Published Material
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? B Observational
Identify ecosystem processes impacted:

Nitrogen fixation and possibly allelopathic litter. Species is fire-adapted but has not appeared to change fire regime any more than current land management practices. Nitrogen-fixing especially detrimental in serpentine areas as it allows other invasives to establish. Some evidence from South Africa that it can alterbank stability in riparian areas.


Sources of information:

Andrea Williams, observational


Question 1.2 Impact on plant community composition,
structure, and interactions?
B Observational
Identify type of impact or alteration:

Appears to displace many natives, possibly due to allelopathic effects. This includes Danthonia california, Festuca rubra, Umbellularia california, Ceanothus pumilis, Frangula purshiana and F. californica, Eschscholzia californica, Rhododendron occidentale, etc.


Sources of information:

Andrea Williams and Peter Warner, observational


Question 1.3 Impact on higher trophic levels? B Other Published Material
Identify type of impact or alteration:

Threatens habitat of rare and endangered Mount Hermon June beetle by blocking sunlight.
Possibly displaces good forage species for deer and small mammals. Stands lack structure preferred by songbirds.


Sources of information:

Horowitz, M. 2003. Alternatives to chemical stump treatment of Acacia dealbata. Proc., Cal-IPC. 7:54-56.
Andrea Williams, observational


Question 1.4 Impact on genetic integrity? D Reviewed Scientific Publication

None. No native Acacia in areas where this species occurs.


Sources of information:

Hickman, J. C. (ed.) 1993. The Jepson Manual, Higher Plants of California. University of California Press. Berkeley, CA enter text here


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

Inhabits roadsides and other disturbed places and areas with little or no human disturbance. While it originally established in disturbed areas, in less than 20 years it has spread into intact grassland and woodland areas.


Sources of information:

Andrea Williams, observational


Question 2.2 Local rate of spread with no management? B Observational
Describe rate of spread:

Populations are expanding, but not rapidly yet. Spreading locally (<1 mile) along riverbanks and roadsides, plus new patches from seed and rhizomes into intact areas.


Sources of information:

DiTomaso, observational
Andrea Williams, observational


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

Populations are expanding, but not rapidly yet. Some management has begun in Redwood National Park starting in 2003.


Sources of information:

DiTomaso, observational


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

Perennial tree. Reproduces by seeds and can spread by rhizomes. Also readily sprouts after cutting or damage.


Sources of information:

DiTomaso, J. M., and E. A. Healy. 2007. Weeds of California and Other Western States. University of California Agriculture and Natural Resources Publication 3488. Oakland, CA.


Question 2.5 Potential for human-caused dispersal? A Other Published Material
Identify dispersal mechanisms:

Still widely planted in California as an ornamental.


Sources of information:

DiTomaso, J. M., and E. A. Healy. 2007. Weeds of California and Other Western States. University of California Agriculture and Natural Resources Publication 2488. Oakland, CA.


Question 2.6 Potential for natural long-distance dispersal? C Observational
Identify dispersal mechanisms:

Seeds may be explosively dispersed from parent plant and also moved my animals, but this is not long distance movement. Could move long distance by water when near a stream.


Sources of information:

DiTomaso, observational.


Question 2.7 Other regions invaded? B Other Published Material
Identify other regions:

Native to the southeastern Australia. In California, it has invaded Del Norte County, near Hiouchi, spreading from old homesites into river bar, grassland, mixed conifer, and Jeffrey pine serpentine woodland. It is also considered invasive in South Africa. Can be found in the bushland in Australia and may invade such areas of California in addition to riparian and coast sites.


Sources of information:

DiTomaso, J. M., and E. A. Healy. 2007. Weeds of California and Other Western States. University of California Agriculture and Natural Resources Publication 3488. Oakland, CA.
Wells, M.J. et al. 1979. Woody plant invaders of the central Transvaal. Proc. 3rd National Weeds Conf of S. Afr. pp. 11-23.
Observational, Andrea Williams


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

Commonly planted as an ornamental, but has been reported to escape cultivation along the coast from north to south. Found in riparian areas, mixed conifer forest, woodlands, and coast grasslands.


Sources of information:

Andrea Williams, observational


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

Only an occasional escape in California.


Sources of information:

DiTomaso, observational


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less No
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 Unknown
Seeds remain viable in soil for three or more years Yes
Viable seed produced with both self-pollination and cross-pollination Unknown
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: 7
Total unknowns: 2
Total score: A?

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 grassland
Great Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forestD, < 5%
riparian woodlandD, < 5%
riparian scrub (incl.desert washes)
Woodlandcismontane woodlandD, < 5%
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forestD, < 5%
closed cone coniferous forestD, < 5%
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): D

Infested Jepson Regions

Click here for a map of Jepson regions

  • Cascade Range
  • Central West
  • Great Valley
  • Northwest
  • Sierra Nevada
  • Southwest