Plant Assessment Form

Spartina densiflora

Common Names: dense-flowered cordgrass; Chilean cordgrass.

Evaluated on: April 15, 2004, revised July 25, 2005, Roye

List committee review date: 15/08/2005

Re-evaluation date:

Evaluator(s)

Dr. Debra Ayres
UC Davis
Evolution and Ecology, 1 Shields Ave., Davis, 95616
530 752 6852
drayres@ucdavis.edu
Cynthia L. Roye/Associate State Park Resource Ecologist
California State Parks
California State Parks, Natural Resources DivisionPO Box 942896, Sacramento, CA 94296-0001
(916) 653-9083
croye@parks.ca.gov

List commitee members

Peter Warner
Jake Sigg
Joe DiTomaso
Cynthia Roye

General Comments

This plant has invaded all available habitat in Humboldt Bay. Populations are found in San Francisco Bay at Corte Madera Creek, Point Pinole and Pickleweed Park. Infestations in Tomales Bay and Bolinas Bay have been controlled.

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 Other Published Material
Impact?
Four-part score AABC Total Score
A
1.2 ?Impact on plant community A. Severe Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels B. Moderate Other Published Material
1.4 ?Impact on genetic integrity C. Minor/Low Observational
2.1 ?Role of anthropogenic and natural disturbance in establishment A. Severe Reviewed Scientific Publication
Invasiveness?
Total Points
15 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 B. Increasing less rapidly Reviewed Scientific Publication
2.4 ?Innate reproductive potential
(see Worksheet A)
B. Moderate Observational
2.5 ?Potential for human-caused dispersal C. Low Anecdotal
2.6 ? Potential for natural long-distance dispersal A. Frequent Reviewed Scientific Publication
2.7 ?Other regions invaded B. Invades 1 or 2 ecological types Reviewed Scientific Publication
3.1 ?Ecological amplitude/Range
(see Worksheet C)
D. Narrow Reviewed Scientific Publication
Distribution?
Total Score C
3.2 ?Distribution/Peak frequency
(see Worksheet C)
C. Low Reviewed Scientific Publication

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 Other Published Material
Identify ecosystem processes impacted:

colonizes open mudflats and openings in marshes. May slow water flow and increase sedimentation.


Sources of information:

San Francisco Invasive Spartina Project N.D. Introduced Spartina densiflora (dense-flowered cordgrass) as accessed on the Internet at: www.spartina.org/species/spartina-densiflora_v2.pdf


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

S. densiflora has shown high tolerance to salinity and co-occurs with Salicornia virginica in the higher tidal marsh. It is able to grow under a wide variety of conditions and ultimately covers the entire area. Has invaded much of Humboldt Bay. The main impacts of S. densiflora are the potential replacement of Salicornia virginica dominated marshes, and the invasion and dominance of upper elevations of restored marshes.


Sources of information:

Ayres DR, Smith DL, Zaremba K, Klohr S, Strong DR. 2004. Spread of exotic cordgrasses and hybrids (Spartina sp.) in the tidal marshes of San Francisco Bay. Biological Invasions. 6: 221-231
Kittleson PM and Boyd MJ. 1997. Mechanims of expansion for an introduced species of cordgrass, Spartina densiflora, in Humboldt Bay, California. Estuaries 20: 770-778.

Castillo JM et al. 2000. Lower limits of Spartina densiflora and S. maritima in a Mediterranean salt marsh determined by different ecophysiological tolerances.


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

Overgrowth of native Salicornia may impact a listed species Salt marsh harvest mouse, which relies on this habitat. California Clapper Rail nests in Salicornia, forages in open channel and may also be negatively effected.


Sources of information:

San Francisco Invasive Spartina Project N.D. Introduced Spartina densiflora (dense-flowered cordgrass) as accessed on the Internet at: www.spartina.org/species/spartina-densiflora_v2.pdf


Question 1.4 Impact on genetic integrity? C Observational

Spartina densiflora x foliosa hybrids have been found where the 2 species occur at Creekside Park, Marin Co. This is under investigation by the Ayres lab, but thus far it appears there are only F1 hybrids (no backcrossing or hybrid crossing), which means impact to the genetic integrity of the native will be limited. The new hybrids however, may create problems on their own if they find a way to produce good seed.


Sources of information:

Ayres, Strong et al. Unpublished data.


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

S. densiflora colonizes the open mud of restoration sites, and naturally caused bare patches in established marshes. Continuing restoration of salt ponds into tidal marsh will likely create recruitment sites for cordgrass seed.


Sources of information:

Ayres DR, Smith DL, Zaremba K, Klohr S, Strong DR. 2004. Spread of exotic cordgrasses and hybrids (Spartina sp.) in the tidal marshes of San Francisco Bay. Biological Invasions. 6: 221-231.
Ayres and Strong, unpublished data.


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

moderate to rapid plants have been found 10s of km (and in Tomales Bay and Puget Sound WA!) from known populations due to tidally borne seed and/or human aided transport (see below).


Sources of information:

Ayres DR, Smith DL, Zaremba K, Klohr S, Strong DR. 2004. Spread of exotic cordgrasses and hybrids (Spartina sp.) in the tidal marshes of San Francisco Bay. Biological Invasions. 6: 221-231.


Question 2.3 Recent trend in total area infested within state? B Reviewed Scientific Publication
Describe trend:

increasing


Sources of information:

Ayres et al, 2004


Question 2.4 Innate reproductive potential? B Observational
Describe key reproductive characteristics:

Ayres DR, Smith DL, Zaremba K, Klohr S, Strong DR. 2004. Spread of exotic cordgrasses and hybrids (Spartina sp.) in the tidal marshes of San Francisco Bay. Biological Invasions. 6: 221-231.
Spicher, D. Master's thesis, SF State.
Ayres, Strong and Lee. Unpublished data.


Sources of information:

limited - however, the occurance of S. densiflora populations near oystering areas in Tomales Bay and in Puget Sound, WA suggests possible human aided movement during transport of oyster spat


Question 2.5 Potential for human-caused dispersal? C Anecdotal
Identify dispersal mechanisms:

limited - however, the occurance of S. densiflora populations near oystering areas in Tomales Bay and in Puget Sound, WA suggests possible human aided movement during transport of oyster spat


Sources of information:

Katy Zaremba, personal communication and pers. communication from WA Spartina workers.
Ayres et al, 2004


Question 2.6 Potential for natural long-distance dispersal? A Reviewed Scientific Publication
Identify dispersal mechanisms:

seed floating on the tides; seed contained in rafts of cordgrass wrack Cordgrass seed is able to float for long periods; seed-containing wrack is able to move long distances. Long distance dispersal on tidal currents is feasible.


Sources of information:

Huiskes AHL, Koutstaal BP, Herman PMJ, Beeftink WG, Markusse MM and De Munck W (1995) Seed dispersal of halophytes in tidal salt marshes. Journal of Ecology 83: 559-567;
Kathleen Sayce, personal communication on dispersal of S. alterniflora from Willapa Bay to Greys Harbour, WA


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

S. densiflora has completely colonized all available habitat in Humboldt
Bay, and is a problem in Spanish marshes, dunes, saltpans.


Sources of information:

Kittleson and Boyd, 1997, and pers. comm. Kittleson.
Castillo et al 2000 and references therein


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? D Reviewed Scientific Publication

S. densiflora was introduced into Humboldt bay within the past 100 years during lumber shipping between there and Chile. Plants thought to be an ecotype of S. foliosa were transplanted into Creekside Park during the 1970s. Other plants were planted into Richardson Bay as part of a landscaping project. One major type invaded, salt marsh


Sources of information:

Kittleson and Boyd, 1997.
Ayres et al, 2004.
Spicher, D. MS thesis


Question 3.2 Distribution/Peak frequency? C Reviewed Scientific Publication
Describe distribution:

Plants have spread from points of deliberate introduction sometimes a very long distance (80 km). In addition to Corte Madera Creek, the plant has been found in small infestions up coast and has occupied much of Humboldt Bay; probably more than 5% of the marsh habitat in California. Marshes and creeks (i.e. Corte Madera Creek) neighboring invaded marshes are especially vulnerable to invasion.


Sources of information:

Ayres DR, Smith DL, Zaremba K, Klohr S, Strong DR. 2004. Spread of exotic cordgrasses and hybrids (Spartina sp.) in the tidal marshes of San Francisco Bay. Biological Invasions. 6: 221-231.


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 Unknown
Seeds remain viable in soil for three or more years No
Viable seed produced with both self-pollination and cross-pollination Unknown
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 Yes
Total points: 5
Total unknowns: 2
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
estuariesC, 5% - 20%
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 prairie
valley and foothill grassland
Great Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swampU, Unknown
Riparian and Bottomland habitatriparian forest
riparian woodland
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
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): D
Distribution (highest score): C

Infested Jepson Regions

Click here for a map of Jepson regions

  • Central West
  • Northwest