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Species
Bromus rubens L.
IUCN
NCBI
EOL Text
Comments: Bromus rubens occurs at low to medium elevations (below 5,000 ft), in deserts and chaparral hillsides, and various places where competition from established herbaceous plants is minimal: along roadsides, waste places, rangelands and cultivated fields (Munz and Keck 1959, Beatley 1966, Crampton 1974). It is a dominant species on some rangeland that, previous to the destruction of the vegetation, were abundant in perennial native grasses (Burcham 1957, Humphrey 1977).
Bromus rubens is commonly found growing on shallow dry soil or poor textured, clayey soil (Sampson et al. 1951, Wu and Jain 1978). This cool season annual germinates in the fall and grows slowly until early spring at which time the growth rate rapidly increases, culminating with the development of the reproductive structures (Hufstader 1978). Due to the fall germination and the winter growth period, red brome grows in locales with hot, dry summers and mild, moist winters. This species is killed by winter freeze and requires between 10 cm and 25 cm of precipitation throughout its growing season (Hulbert 1955, Bartolome et al. 1980).
Bromus rubens grows on south facing slopes (Hufstader 1978) and is a common constituent in the steppe region in the Sacramento-San Joaquin valley of California (Daubenmire 1978). It is often a co- dominant or subdominant species in COLEOGYNE spp. communities in southern Nevada and California; BROMUS TECTORUM, but not Bromus rubens, grows in ARTEMISIA-Pinyon-Juniper plant communities in Nevada which occur above 5,000 feet elevation (Beatley 1966, Daubenmire 1978).
Bromus rubens often coexists with Bromus mollis or Bromus tectorum (Hulbert 1955, Wu and Jain 1979). The life-cycle and growth patterns of these species are similar, with the exception that B. tectorum is more tolerant of frost (Hulbert 1955, Bock pers. comm.). A greater amount of literature is available on B. tectorum than on B. rubens. This is due to the extensive distribution of B. tectorum in western United States, particularly in the Great Basin and Columbia Basin regions (Hulbert 1955). The distribution of Bromus rubens is far more patchy than it is for Bromus mollis; B. rubens appears to be more sensitive than B. mollis to plant competition, allelopathic substances and grazing patterns. Thus, environmental factors greatly influence the distribution of red brome, particularly in comparison to B. mollis (Wu and Jain 1979).
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Annual.
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Rights holder/Author | Bibliotheca Alexandrina, BA Cultnat, Bibliotheca Alexandrina - EOL Ar |
Source | http://lifedesk.bibalex.org/ba/pages/2195 |
More info for the terms: competition, density, shrub, shrubs
Foxtail chess and red brome prefer disturbed sites in Mediterranean climates [41,66]. Elevational ranges are described below by state:
Species | State | Range |
foxtail chess, red brome | California | 7,200 feet (2,200 m) [41] |
red brome | Nevada | 1,200 to 6,000 feet ( 370-1,800m) [44,48] |
red brome | southern Nevada | 4,000 to 5,000 feet (1,200-1,500 m) [10] |
red brome | Utah | 3,000 to 5,000 feet (910-1,520 m) [64] |
Regional: In California, foxtail chess prefers areas receiving less than 9.8 inches (250 mm) annual rainfall [8]. Foxtail chess is a dominant species in California valley grasslands receiving less than 7.5 inches (190 mm) rainfall [40], and is abundant in California valley grasslands receiving less than 12 inches (305 mm) annual precipitation. In areas with annual precipitation greater than 12 inches (305 m), foxtail chess is replaced by soft chess (Bromus mollis) [7,8].
Bowers [19] monitored the relative abundance of northern Mojave Desert annuals over 6 years in relation to precipitation. Red brome density was highest during years receiving 2.4 to 4.2 inches (63-109 mm) precipitation; results are summarized below:
Pre-census precipitation (mm) between 1970-1976:
Year | Sept.-Oct. | Nov.-Dec. | Jan.-Feb. | Total | Mean red brome/0.25m2 |
1971 | 0 | 37.4 | 8.1 | 45.5 | 0.113 |
1972 | 0 | 41.4 | 0 | 41.4 | 0.132 |
1973 | 40.4 | 29.7 | 70.9 | 141.0 | 0.073 |
1974 | 3.8 | 24.9 | 35.0 | 63.7 | 0.959 |
1975 | 25.9 | 35.3 | 5.1 | 66.3 | 1.012 |
1976 | 5.8 | 4.8 | 98.0 | 108.6 | 6.780 |
Soils: Red brome commonly occurs in small patches on shallow soils, growing best where there is little competition from other annuals [86]. In southern Nevada, red brome occupies blackbrush communities with coarse-textured soils, showing best growth under shrubs and peripheries of shrub canopies [10]. Upland clay and sandy loam ranges and rolling sandy hills receiving 8 to 12 inches (203-305 mm) precipitation promote good growth in southern Utah 60.
Red brome is often found in areas with relatively high levels of sulfur dioxide pollution [69].
REPRODUCTIVE CHARACTERISTICS: The dormancy period of Bromus rubens seeds varies depending on the geographic location of the plant (Jain 1982). Genetic variability between populations may account for the direct relationship between time of maximum germination and probability of rainfall in a specific locale. Depending upon the climate of the site, the seeds, which are produced and mature in the spring, usually remain dormant throughout the hot, dry period of the summer and then germinate after the first rainfall that exceeds 1.0 cm (Hammouda and Bakr 1969). Many seeds display dormancy during the first few weeks after dissemination, but as the season progresses the degree of dormancy is significantly reduced (Jain 1982). Greater than 50% of the year's seed source germinates by the middle of September in California (Jain 1982).
Precipitation affects germination much more than it influences other stages of growth (Hufstader 1978). Rains that deliver less than 1.0 cm of water will not stimulate germination. The optimum germination conditions for Bromus rubens are temperatures between 20 C and 25 C with greater than 1.0 cm of rainfall (Hammouda and Bakr 1969). The optimum and maximum temperature for germination of Bromus tectorum seeds increases with increasing age of the seed (Hulbert 1955). About half as much rain is required (1.2 cm) to stimulate annual brome seeds to germinate than is required (2.5 cm) to stimulate native winter annuals in Nevada (Beatley 1966). This trait allows the introduced weeds to initiate development early in the season, thus giving them an advantage over the native annual species.
Moisture plays a greater role than temperature in influencing germination of red brome seeds. A germination rate of 54% occurred during three months, each with different average temperatures, provided that the moisture in the soil was not limiting (Hammouda and Bakr 1969). Seeds germinate throughout the winter and into spring following heavy rains (Beatley 1966).
Mulch in the form of plant litter may aid in germination of Bromus rubens by providing a protected site which maintains the necessary moisture and temperature conditions (Evans and Young 1970). Annual grasses, especially those with sharp pointy florets, such as red brome, require (1) an unvegetated area for the seeds to become embedded in the soil and (2) a site with optimum conditions and protection from disturbances (Pickford 1932). Nitrogen in desert soils is often limiting and mulch provides a readily available source of nitrogen to seedlings, thus aiding in the establishment of Bromus rubens (Hulbert 1955, Kay 1971). Surprisingly, mulch appears beneficial in significantly increasing the moisture availability only in areas with an annual precipitation rate of greater than 25 cm (Bartolome et al. 1980).
The tolerance of Bromus rubens to high salt and high pH conditions partially explains its success in desert soils. Delayed germination occurs when Bromus rubens seeds are grown in soil mixed with coal precipitator ash (Vollmer et al. 1982). Seeds in soil mixed without ash (pH 8.3) germinate at a 93% rate within 12 days, as compared to the delayed (24 days) low, but still significant, rates of germination (15%) occurring in soils mixed with 50% ash (pH 11.4 to pH 12.7). In addition to Bromus rubens' ability to germinate in extremely alkaline conditions is its ability to germinate (greater than 50% germination) in high osmotic potential soils treated with sodium chloride solutions of 7.5 atmospheres (Hammouda and Bakr 1969).
Increasing the depth of seed burial results in a reduced number of emerging seedlings of Bromus tectorum; 93% of seeds 4 cm deep emerge, whereas 14% of seeds 6 cm deep emerge (Hulbert 1955). Partial burial is most likely beneficial to seed germination because of the retarding effect diffuse light has on germination of B.TECTORUM seeds (Hulbert 1955).
Seed viability rapidly decreases over the first year after seeds are dispersed (Jain 1982). Approximately 100% of the seeds are viable during the initial fall after they are produced (Wu and Jain 1979). However, seed carry-over from one year to the next is less than 2% as measured by dormant seeds in the soil (Wu and Jain 1979). In contrast, seeds of Bromus tectorum stored in laboratory conditions for over 11 years demonstrate a 96% viability rate (Hulbert 1955).
Bromus rubens is a prolific seed producer: an average of 76 seeds per plant in natural populations, 142 seeds per plant in experimental mixed stand plots, or 83,600 seeds per square meter of densely spaced plants (Wu and Jain 1979). Reproductive capacity is reduced by a low seedling survival rate and by a low maturation probability (Wu and Jain 1979).
Mechanisms of seed dispersal of Bromus rubens are poorly understood. Wind carries florets of Bromus tectorum a few meters from the parent plant (Hulbert 1955). Rodent excavation may also be a means of disseminating the seeds (Hulbert 1955). Other common mechanisms of seed dispersion, such as flood sediment transport and scattering by animals, most likely aid in the dissemination of B. rubens seeds.
Most annual bromes, including Bromus rubens, are facultatively autogamous (Smith 1981). The outcrossing rate of red brome is less than 0.1% (Wu and Jain 1978). The low rate of pollen production, short filaments and lack of exserted anthers contribute to the self-pollination mechanism of red brome (Hulbert 1955, Smith 1981). Apparently, the stigma is pollinated by direct contact with the adjacent anther. This partially explains the low genetic variability within a population and, along with several other characteristics, may account for the relatively narrow niche that Bromus rubens occupies (Wu 1975, Wu and Jain 1979).
Bromus rubens is the only one of ten annual brome species tested which displays normal spring flowering when plants are kept warm during the winter and planted in the field during the spring (Hulbert 1955). All other species tested require a cold floral induction period.
The recovery potential of land invaded by this species is good, providing that competition increases form other herbaceous species. Bromus rubens is an annual plant and does not produce a dormant vegetative structure, thus recovery is based on reducing the quantity of seeds. Since less than 2% of seeds maintain their viability over a one year period, control is plausible. Crowding and shading, early in the plant's development, are detrimental to the survival of Bromus rubens (Hufstader 1976, Wu and Jain 1979).
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More info on this topic.
This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):
More info for the terms: cover, shrub
SRM (RANGELAND) COVER TYPES [74]:
201 Blue oak woodland
202 Coast live oak woodland
205 Coastal sage shrub
206 Chamise chaparral
207 Scrub oak mixed chaparral
208 Ceanothus mixed chaparral
209 Montane shrubland
210 Bitterbrush
211 Creosotebush scrub
212 Blackbush
214 Coastal prairie
215 Valley grassland
401 Basin big sagebrush
413 Gambel oak
414 Salt desert shrub
503 Arizona chaparral
506 Creosotebush-bursage
507 Palo verde-cactus
United States
Rounded National Status Rank: NNA - Not Applicable
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Rights holder/Author | DARA NEWMAN, NatureServe |
Source | http://explorer.natureserve.org/servlet/NatureServe?searchName=Bromus+rubens |
An annual herb with solitary or caespitose, erect culms. Leaf-sheaths are hirsute; the leaf-blade surface is also hirsute on both sides. Inflorescence is a tightly congested panicle with densely pubescent axis, and solitary spikelets. Fruit is an apically hairy caryopsis with adherent pericarp.
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Rights holder/Author | Bibliotheca Alexandrina, BA Cultnat, Bibliotheca Alexandrina - EOL Ar |
Source | http://lifedesk.bibalex.org/ba/pages/2195 |
More info on this topic.
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
More info for the term: cover
SAF COVER TYPES [33]:
242 Mesquite
249 Canyon live oak
250 Blue oak-foothills pine
255 California coast live oak
Rounded Global Status Rank: GNR - Not Yet Ranked
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Rights holder/Author | DARA NEWMAN, NatureServe |
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United States
Origin: Exotic
Regularity: Regularly occurring
Currently: Unknown/Undetermined
Confidence: Confident
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