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More info for the term: shrub
Spanish broom is native to the southern Mediterranean region of Europe,
including Spain, Morocco, the Canary Islands, Madeira, and the Azores.
Spanish broom's North American distribution is from Washington to southern California
[53]. It has also established in Hawaii. Spanish broom occurs in other states as a cultivated ornamental
(e.g. Utah [57], the Intermountain west [2], Texas
[29]).
Spanish broom was introduced into the California ornamental trade in 1848 in
San Francisco. Beginning in the late 1930s, it was planted along mountain
highways in southern California. By 1949, Spanish broom had escaped cultivation
and established populations in Marin County ([38], and references therein). It
now occurs in the north coast counties of California, the San
Francisco Bay region, the Sacramento Valley, through the south coast counties
into northern Baja California [27,37], in the western Transverse Ranges, and the Channel Islands [38].
It also occurs on dry slopes in the eastern half of the Santa Monica
Mountains [15]. Of the invasive
brooms in California, Spanish broom is less widespread and is considered less of a problem
than Scotch broom (Cytisus scoparius) and French broom (Genista
monspessulana) [28]. There is no information in the literature on distribution of
Spanish broom in Oregon, Washington, or Hawaii. Plants database provides a state distribution map of Spanish broom.
Spanish broom is 1 of 4 nonnative invasive broom species that occur in North America. Spanish broom, Scotch broom, Portuguese broom (C. striatus), and French broom occur in similar habitats. Common gorse (Ulex europaeus)
is another leguminous shrub that occurs in similar habitats.
The following lists include vegetation types in which Spanish broom is known to
be or thought to be potentially invasive, based on reported occurrence and
biological tolerances to site conditions from studies of Spanish broom in
California. There is no information about Spanish broom
distribution or site tolerances outside California; therefore, these lists are somewhat
speculative and may be imprecise.
More info for the terms: cover, fire management, phenology, prescribed burn, prescribed fire, restoration, wildfire
Postfire colonization potential:
According to Nilsen [38], Spanish broom is especially invasive in southern California chaparral after
fire. No other information on postfire colonization potential of Spanish broom
is available.
Preventing postfire establishment and spread:
The USDA Forest Service's "Guide to Noxious Weed Prevention
Practices" [52] provides several fire management considerations for weed
prevention in general that may apply to Spanish broom.
Preventing invasive plants from establishing in weed-free burned areas is the
most effective and least costly control method. This can be accomplished through
careful monitoring, early detection and eradication, and limiting invasive plant
seed dispersal into burned areas by [23,52]:
re-establishing vegetation on bare ground as soon after fire as possible
using only certified weed-free seed mixes when revegetation is necessary
cleaning equipment and vehicles prior to entering burned areas
regulating or preventing human and livestock entry into burned areas until
desirable site vegetation has recovered sufficiently to resist invasion by
undesirable vegetation
detecting weeds early and eradicating before vegetative spread and/or seed
dispersal
eradicating small patches and containing or controlling large infestations
within or adjacent to the burned area
In general, early detection is critical for preventing establishment of large
populations of invasive plants. Monitoring in spring, summer, and fall is
imperative. Managers should eradicate established Spanish broom plants and small
patches adjacent to burned areas to prevent or limit postfire dispersal and/or
spread onto the site [23,52].
The need for revegetation after fire can be based on the degree of desirable
vegetation displaced by invasive plants prior to burning, and on postfire
survival of desirable vegetation. Revegetation necessity can also be related to
invasive plant survival as viable seeds or root crowns [23].
Managers can enhance the success of revegetation (natural or artificial) by
excluding livestock until vegetation is well established (at least 2 growing
seasons) [23]. See Integrated Noxious Weed Management after Wildfires for more information.
When planning a prescribed burn, managers should preinventory the project
area and evaluate cover and phenology of any Spanish broom and other invasive
plants present on or adjacent to the site, and avoid ignition and burning in
areas at high risk for Spanish broom establishment or spread due to fire
effects. Managers should also avoid creating soil conditions that promote weed
germination and establishment. Weed status and risks must be discussed in burn
rehabilitation plans. Also, wildfire managers might consider including weed
prevention education and providing weed identification aids during fire
training; avoiding known weed infestations when locating fire lines; monitoring
camps, staging areas, helibases, etc., to be sure they are kept weed free;
taking care that equipment is weed free; incorporating weed prevention into fire
rehabilitation plans; and acquiring restoration funding. Additional guidelines
and specific recommendations and requirements are available [52].
Fire as a control agent:
While prescribed fire is sometimes used in management of French broom and Scotch broom, no information is available on using fire to control Spanish broom.
Fire hazard potential:
According to Nilsen [38], Spanish broom can grow in tall, dense patches and form a tangle containing a large
amount of dead wood and, therefore, mature stands should be considered a fire
hazard during the dry season. DiTomaso [16] also suggests that dense broom infestations produce substantial
dry matter that can create a serious
fire hazard.
More info for the terms: density, fire management, invasive species, natural, restoration, shrub, shrubs, tree
Impacts:
Spanish broom rapidly colonizes disturbed habitats and develops thick shrub communities that
prevent colonization by native chaparral species. It may be a fire hazard during
the dry season [38]. However, it is listed by the California Invasive Plant Council
as a "wildland pest plant of lesser invasiveness" [8].
As a nitrogen-fixing plant, Spanish broom may enrich soil nitrogen levels in
invaded communities. Although nitrogen fixation has not
been studied in Spanish broom, Scotch broom is capable of fixing nitrogen
throughout the year in regions with mild winters [58]. The ability of the brooms to fix nitrogen increases the total
amount of nitrogen and the way in which nitrogen cycles in invaded communities [25].
Nitrogen enrichment is unlikely to benefit native plants and may reduce species
diversity [14], except in ecosystems dominated by nitrogen-fixers. This may have implications for restoration and
rehabilitation efforts [25].
Control:
There is little information on controlling Spanish broom.
Nilsen [38] presents a summary of possible control approaches based on the biology of
the plant, rather than on information derived from controlled experiments [38]. See FEIS reviews on Scotch broom and French broom for information on controlling these similar species.
It is likely that the success of any control method will vary with site
characteristics (topography, soils, climate), age and density of plants in the stand, and the
availability of human and technical resources. Since a large and persistent seed
bank is predicted for this species, it is likely that seedlings will establish
rapidly following fire or mechanical removal of aboveground biomass [38].
A comprehensive monitoring of control effectiveness is critical because there
is no scientifically based knowledge about control of Spanish broom. Experimental
manipulations should be monitored at least annually. Each monitoring visit
should determine the number of new plants and the size or age distribution of
the recovering populations. Attention should be placed on the
proportion of new individuals coming from the seed bank or sprouting from old
plants. Monitoring should continue for at least 5 years after control treatment
[38].
Prevention:
The most effective method for managing
invasive species is to prevent their establishment and spread. Some methods of
prevention include limiting seed dispersal, containing local infestations,
minimizing soil disturbances, detecting and eradicating weed introductions
early, and establishing and encouraging desirable competitive plants [44]. One way to help prevent continued
introductions of Spanish broom into wildlands is to prevent its sale as a horticultural
species.
Integrated management:
A particularly effective control combination for
Spanish broom may be saw cutting followed by application of herbicide to the cut
stem to kill adult plants. Spanish broom seedlings are likely to
establish from the soil seed bank so monitoring and follow-up treatments of new
seedlings is necessary for several years [38].
Physical/mechanical:
In general, physical and mechanical control methods are likely to be effective only when Spanish broom is
young [38]. The Nature Conservancy's Element Stewardship Abstract on Spanish broom provides a general overview of physical and mechanical control methods that may be effective for
controlling infestations [28].
Pulling with weed wrenches is effective for small broom infestations or in
areas where an inexpensive, long-duration labor source is dedicated to broom
removal [51]. Hand-pulling Spanish broom plants may be most practical and
effective when the stand is 1 to 4 years old, and plants are small enough, as
long as roots are removed and follow-up treatment of seedlings is done. The
optimal season for pulling may be July to September when plants are experiencing
water stress [36]. When plants have matured to small tree size, they cannot easily be
removed with hand tools [38].
Nilsen [38] suggests that machines such as brush hogs are probably impractical
for Spanish broom removal, since it commonly occurs on steep slopes, and
because the trunks of Spanish broom grow rapidly to a size outside the range of
effectiveness for this technology. Saws can be used to cut plants with larger
stems; however, Spanish broom has a great facility for sprouting from a saw cut
even when the cut is close to the ground. When brush
hogs or saws are used to cut Spanish broom stems, sprouting should be expected.
Among all the mechanical methods, saw cutting is least likely to be effective in
preventing sprouting [38].
Fire: See the Fire Management Considerations section of this summary.
Biological:
Biological control of invasive species has a long history,
and there are many important considerations before the implementing a biological
control program. Tu and others [51] provide general information and considerations for biological
control of invasive species in their Weed control methods handbook. Additionally, Cornell University, Texas A & M University, and NAPIS websites offer
information on biological control.
As of this writing (2005) there are no USDA approved biological
control agents for Spanish broom. In greenhouse situations
plants are susceptible to mealy bugs and show evidence of viral
depression of growth [38]. An insect purposely introduced for control of Scotch broom,
the Scotch broom bruchid (Bruchidius villosus) [11], also attacks Portuguese broom,
Spanish broom, and French broom. See Coombs and others [12] for more information on this
insect, its distribution, and effects.
Domestic goats are said to be effective at controlling reestablishment of broom [28].
Chemical:
Herbicides are effective in gaining initial control of a new
invasion (of small size) or a severe infestation, but are rarely a complete or
long-term solution to invasive species management, as they do not change
conditions that allow infestations to occur [7]. Herbicides are more effective
on large infestations when incorporated into long-term management plans that
include replacement of weeds with desirable species, careful land use
management, and prevention of new infestations. See the Weed control methods handbook [51]
for considerations on the use of herbicides in
natural areas and detailed information on specific chemicals and adjuvants.
Spanish broom is sensitive to applied pesticides. In greenhouse
situations only mild pesticides can be used without detrimentally affecting the
plants. Therefore, it is highly likely that application of chemicals such as glyphosate or
triclopyr will drastically reduce population size. The ramifications of applying
herbicides to a plant community must be carefully considered, because effects on
nontarget species are likely, especially when foliage spray methods are used [38].
Rusmore and Butler [42] compared the efficacy of basal
bark applications of varying rates of triclopyr on different size Spanish broom shrubs, at 3
phenological stages, under different moisture and shade conditions on a
California riparian site. Small differences were observed among treatments,
although results were not statistically significant. The kill rate averaged over
90% across all treatments [42].
See The Nature Conservancy's Element Stewardship Abstract on Spanish broom for a more detailed review of chemical control [28].
Cultural:
Research by Williams [59] suggests that
broom stands are early successional and can be replaced by later seral
vegetation if left undisturbed; however, tests of this assumption are not reported in the
literature. A review by Hoshovsky [28] suggests that planting of
tall growing shrubs or trees in or near broom stands may aid in reducing
photosynthesis in broom plants and possibly lead to their demise.
More info for the term: low-severity fire
As of this writing (2005) no information is available on the response of Spanish
broom to fire. A review by Nilsen [38] suggests that Spanish broom is likely to
sprout vigorously from trunk bases and stem meristems
following low-severity fire.
However, a severe fire that kills all aboveground stems and burns hot and close
to the ground will completely kill standing individuals and most likely remove
some of the seed bank. Seeds of Spanish broom are similar in structure to those of
Scotch broom. In heterogeneous or low-temperature fires Scotch broom seed banks are not effectively
reduced. Under similar fire conditions it is unlikely that fire will effectively
reduce seed bank regeneration of Spanish broom [38].
More info on this topic.
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
BLM PHYSIOGRAPHIC REGIONS [4]:
1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
7 Lower Basin and Range
More info for the term: high-severity fire
As of this writing (2005) no information is available on the immediate effects
of fire on Spanish broom plants or seeds. Based on information from fire effects
on Scotch and French broom, and reproductive characteristics described by Nilsen
[38], it is likely that Spanish broom is top-killed by fire, and that perennating
tissues below ground survive and sprout after fire.
Spanish broom seed in the soil seed bank is probably not damaged by fire, and
may be stimulated to germinate. High-severity fire may kill
Spanish broom plants and seeds. Research is needed on the effects of fire on
Spanish broom to support or refute these conjectures.
See FEIS reviews on
French broom and
Scotch broom for more information on fire effects on these species.
II, V, VIII, IX
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | Pablo Gutierrez, IABIN |
Source | No source database. |