Plant Assessment Form

Tamarix gallica

Common Names: French tamarisk

Evaluated on: 2/8/03

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

5/26/17 Note by Ramona Robison.
This PAF was originally prepared for three species: Tamarix ramosissima, Tamarix gallica, and Tamarix chinensis. It has now been split into three PAFs and the information copied into each. This decision was based on the overlapping ranges of the three species and the hybridization between T. chinensis and T. ramosissima. PAF could be updated to include recent information on biocontrol in California and elsewhere.

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 B. Increasing less rapidly Other Published Material
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High 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 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)
B. Moderate 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? A Reviewed Scientific Publication
Identify ecosystem processes impacted:

Very high water use and increased deposition of salts on soil surface. The longer the community has been invaded by saltcedar the more xeric in nature are the plant species which occupy the understory. Such deposits of salt-encrusted needles can inhibit other species germination. Saltcedar has been blamed for increasing flooding by forming a partial barrier to floodflow, which can cause floodwater to disperse and inundate areas that otherwise would not be flooded. With the invasion of saltcedar there has been an apparent increase in the frequency of fire in riparian ecosystems. Evapotranspiration rates of saltcedar are among the highest of any phreatophyte evaluated in southwestern North America, including native riparian trees. Saltcedar has been reported to contain 41,000 ppm dissolved solids in the guttation sap.


Sources of information:

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

Saltcedar replaced two phreatophytic grass species, saltgrass (Distichlis stricta) and alkali sacaton (Sporobolus airoides) in a southwestern riparian zone. In some areas it makes up 70-80% of the vegetative cover, substantially displacing native vegetation and reducing the value of this critical wetlands complex for wildlife. In one river system, little regeneration of cottonwoods occurred in the past 30-35 years in a saltcedar-infested area. In the lower Colorado River, saltcedar replaced up to 90% of the riparian communities historically dominated by cottonwood-willow forests. Once established, periodic burning, clearing, and flooding have allowed saltcedar communities to remain young and to form nearly impenetrable thickets. Saltcedar can form stands considerably more dense than naturally occurring riparian vegetation.


Sources of information:

Question 1.3 Impact on higher trophic levels? A Reviewed Scientific Publication
Identify type of impact or alteration:

The majority of birds do not use saltcedar in high proportions compared with native plant communities. Frugivores and insectivores, abundant in native riparian vegetation, almost completely avoid saltcedar. Studies showed that several species had a higher affinity for the cottonwood-willow association, including common flicker, yellow-bellied sapsucker, porcupine and beaver. With the exception of desert woodrat and desert cottontail, no native mammal species are known to feed upon saltcedar. Then consumed by wildlife, only young growth is utilized. Although certain wildlife species may find saltcedar beneficial to their survival, the encroachment of saltcedar has most certainly altered the native habitat that was apparently of great benefit to wildlife. Although the southwestern willow flycatcher can nest in saltcedar, infestation have a negative impact on most other birds that would normally use the native vegetation.


Sources of information:

Question 1.4 Impact on genetic integrity? D

None. No native species within the family in North America. Unlikely to cross with any native species.


Sources of information:

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

The development of water management programs that severely impact natural river flows has greatly contributed to spread of saltcedar. These alterations include reservoir and dam construction, river diversions, flow regulations, and irrigation projects. Historically, the flow of these rivers peaked in the late spring and early summer from snowmelt. These changes in channel geometry and streamflow created conditions unfavorable for the regeneration and survival of native riparian species. As a result, rapid colonization and expansion of saltcedar occurred throughout the western river systems. In addition to altering streamflow, clearing and plowing of floodplains and associated agricultural activity also aided saltcedar colonization during the 1800s. Saltcedar has also been reported to rapidly infest riparian areas exposed to heavy grazing. Once established, seed dispersal and plant fragments can become established in otherwise undisturbed areas. Establishment can occur on disturbed and undisturbed sites, but disturbance can increase the rate of establishment.


Sources of information:

Question 2.2 Local rate of spread with no management? A Other Published Material
Describe rate of spread:

Doubling rate between 1920 and 1960 without management was about 6 years. Infestations went from 4,000 ha in 1920 to 362,000 ha in 1960. Recent estimates indicate infestations in the southwestern United States to exceed 600,000 ha .


Sources of information:

Brotherson, J.D. and D. Field. 1987. Tamarix: impacts of a successful weed. Rangelands 9:110-112; see DiTomaso, J.M. 1998. Impact, biology, and ecology of saltcedar (Tamarix spp.) in the southwestern United States. Weed Technology 12:236-336 for review and peer-reviewed reference citations.


Question 2.3 Recent trend in total area infested within state? B Other Published Material
Describe trend:

Recent trend in increase of saltcedar is about at a rate of 3 to 4% per year. Much of the riparian area in the southwestern US has been occupied by saltcedar and the rate of increase there has slowed down. However, the rate of increase in other areas where it is just becoming established, particularly in more northern regions is probably greater.


Sources of information:

Brotherson, J.D. and D. Field. 1987. Tamarix: impacts of a successful weed. Rangelands 9:110-112; see DiTomaso, J.M. 1998. Impact, biology, and ecology of saltcedar (Tamarix spp.) in the southwestern United States. Weed Technology 12:236-336 for review and peer-reviewed reference citations.


Question 2.4 Innate reproductive potential? A Reviewed Scientific Publication
Describe key reproductive characteristics:

Seedlings mature rapidly and produce small, white or pinkish flowers often by the end of the first year of growth. A single large tamarisk tree produces a half million seeds a year. Saltcedar had one major and one minor peak of seed production over a 5.5 month period. Seeds remain viable for several weeks and will germinate on saturated soils or while afloat. It can vegetatively resprout after fire, severe flood, or treatment with herbicides and it is able to accommodate wide variations in soil and mineral gradients in its environment. A good deal of evidence indicates that saltcedar can reproduce very effectively both asexually and sexually.


Sources of information:

Brotherson, J.D. and D. Field. 1987. Tamarix: impacts of a successful weed. Rangelands 9:110-112; Shrader, T.H. Selective management of phreatophytes for improved utilization of natural food-plain resources. Irrigation and Drainage pp. 16-44; see DiTomaso, J.M. 1998. Impact, biology, and ecology of saltcedar (Tamarix spp.) in the southwestern United States. Weed Technology 12:236-336 for review and peer-reviewed reference citations.


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

Planted as an ornamental, as a shade tree, and for erosion control. Not nearly as widely planted today as in the past. Can still be purchased via the internet. It was planted as an ornamental shrub or shade tree, or to create wind breaks, or to stabilize eroding stream banks. It did not escape cultivation until around the 1870s. In the early 1900s, farmers were using this plant for erosion control. It became clear by the 1920s that saltcedar was becoming a serious problem.


Sources of information:

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

The tiny seeds have high viability and long hairs allowing for wind distribution, but may also be carried and deposited along sandbars and riverbanks by water. Stem and root fragments can also float downstream after fragmentation by mechanical damage or flooding and initiate new infestations. Seeds weight about 0.1 mg and can travel long distances in the wind. Flooding can move stem and root fragments very long distances.


Sources of information:

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

Today, saltcedar infestations are common in most river systems over much of Utah, Nevada, Arizona, New Mexico, Colorado, Oklahoma, and Texas. Saltcedar is continuing to spread northward into Montana and Canada and southward into northwestern Mexico. Populations have been reported from as high as 2,135 m in the southern Rocky Mountains, but typically occur below 500 m. Seems to be weedy in areas similar to those in the southwestern US.


Sources of information:

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

Tamarisk was first brought to North America in the 1800s, from southern Europe or the eastern Mediterranean region. Although saltcedar is typically found around aquatic or riparian areas, it has also been observed in scrublands, although not in dense stands.


Sources of information:

Neill, W.M. 1985. Tamarisk. Fremontia 12:22-23; See both Lovich, J. Tamarix ramosissima. In, Invasive Plants of Californias Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley and DiTomaso, J.M. 1998. Impact, biology, and ecology of saltcedar (Tamarix spp.) in the southwestern United States. Weed Technology 12:236-336 for review and other citations.


Question 3.2 Distribution/Peak frequency? B Other Published Material
Describe distribution:

Saltcedar forms dense stands in many riparian areas around the state, particularly in Southern California, where it infests most riparian communities. It is also in many smaller, isolated water sources that are scattered about the desert. Saltcedar is a facultative phreatophyte, which accounts for its primary infestations in riparian and aquatic regions, but occasional occurrence in drier regions.


Sources of information:

Neill, W.M. 1985. Tamarisk. Fremontia 12:22-23; See both Lovich, J. Tamarix ramosissima. In, Invasive Plants of Californias Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley and DiTomaso, J.M. 1998. Impact, biology, and ecology of saltcedar (Tamarix spp.) in the southwestern United States. Weed Technology 12:236-336 for review and other citations. Many sources of personal observations.


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 Yes
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 Yes
Fragments easily and fragments can become established elsewhere Yes
Resprouts readily when cut, grazed, or burned Yes
Total points: 9
Total unknowns: 0
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, reservoirsC, 5% - 20%
Aquatic Systemsrivers, streams, canalsB, 20% - 50%
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrubD, < 5%
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)D, < 5%
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrubC, 5% - 20%
chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairie
valley and foothill grassland
Great Basin grassland
vernal poolD, < 5%
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swampB, 20% - 50%
Riparian and Bottomland habitatriparian forestB, 20% - 50%
riparian woodlandB, 20% - 50%
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): A
Distribution (highest score): B

Infested Jepson Regions

Click here for a map of Jepson regions