Schismus arabicus (Arabian schismus)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Natural enemies
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Impact Summary
- Economic Impact
- Environmental Impact
- Social Impact
- Risk and Impact Factors
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Links to Websites
- Distribution Maps
Don't need the entire report?
Generate a print friendly version containing only the sections you need.Generate report
IdentityTop of page
Preferred Scientific Name
- Schismus arabicus Nees, 1841
Preferred Common Name
- Arabian schismus
Other Scientific Names
- Schismus spectabilis Fig. & De Not.
International Common Names
- English: Arabian grass; camel grass; Mediterranean grass; schismus; split grass
Summary of InvasivenessTop of page
S. arabicus is an annual grass from the Old World that has become widespread and invasive in arid and semi-arid regions of North America and Australia. In North America it has become prevalent in parts of the Sonoran Desert and most of the Mojave Desert. In Australia it is confined to southern and western parts. The grass competes for limiting nutrients and water with native annual plants by occupying spaces between desert shrubs. Its numerous fibrous roots form a dense mat beneath the soil surface. S. arabicus promotes fires, because its dead stems readily carry flames and thus increase fire frequencies and the size of burned areas. In southern California, the decline of the native annual grass Vulpia octoflora (six-weeks fescue) is linked to the increase in S.arabicus. Spread is aided by harvester ants carrying seeds to their nests, as seedlings grow better in ant nests than outside.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Monocotyledonae
- Order: Cyperales
- Family: Poaceae
- Genus: Schismus
- Species: Schismus arabicus
Notes on Taxonomy and NomenclatureTop of page
Schismus arabicus and S. barbatus are often treated as a single species due to their morphological and ecological similarity. Gould (1951) treated S. arabicus as a subspecies of S. barbatus and believed that the two taxa broadly intergrade. In many ecological studies, the two species are not being distinguished and are treated as a single taxon. This datasheet treats them as separate species.
DescriptionTop of page
S. arabicus is a small, tufted annual grass. Culms are erect to ascending, green, smooth, usually widely spreading and 5-20 cm tall. Leaf blades are thread-like, up to 2 mm wide and up to 7 cm long, and usually inrolled. Leaves are mostly basal. At the base of a leaf blade is a ring of rigid hairs of ca 3 mm long. Inflorescence is a dense and narrow panicle, becoming purplish. Spikelets are laterally compressed and contain 5-10 florets. Glumes are persistent, lanceolate, with 3-5 veins and larger than lowest lemmas. Lemmas are membranous, with two lobes at the end and have 9 veins. Paleas are shorter or as long as lemmas and without awns. Caryopses (seeds) are 0.5-0.8 mm long, roundish and loosely bounded by palea and lemma.
DistributionTop of page
S. arabicus is native to the Africa, Asia and parts of Europe. It has become widespread and invasive in arid and semi-arid regions of North America and Australia. In North America, it has become prevalent in parts of the Sonoran Desert and most of the Mojave Desert. In Australia, it is confined to southern and western parts.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
History of Introduction and SpreadTop of page
The exact date of its introduction to North America is obscure because S.arabicus and S. barbatus were often treated as a single species. Felger (1990) treated S. arabicus as a synonym for S. barbatus in his account of Sonoran plant species. He stated that the earliest record in North America is from 1926 in southern Arizona, where the grass has been observed on the floodplain of the Gila River near Sacaton. By 1928 the species had become established and from Arizona it spread westwards (Burgess et al., 1991; Esque and Schwalbe, 2002).
In California, the grass was first observed in Fresno County in 1935 (Felger, 1990). By the 1940s it was abundant throughout the Mojave and Sonoran Deserts (Kemp and Brooks, 1998). Since then, both S. arabicus and S. barbatus have increased their distribution and are now some of the most abundant annual plant species in the deserts of North America (Esque and Schwalbe, 2002).
The oldest specimen collected in South Australia and held in the State Herbarium of South Australia is from 1932 (Atlas of Living Australia, 2012).
Risk of IntroductionTop of page
The grass is unlikely to be introduced intentionally to new areas, but it is likely that it will continue to spread within areas where it has become established.
The grass is listed in the Global Invasive Species Database of the Invasive Species Specialist Group (ISSG, 2012), but it is not listed on any state noxious weed list within the USA.
HabitatTop of page
S. arabicus grows in open and disturbed sites in arid and semi-arid regions. Typical habitats include semi-arid shrublands, roadsides, waste areas, fields, dry river beds and the spaces between desert shrubs (Hickman, 1993; Brooks and Berry, 2006). After disturbance and if bare soil is present, the grass can also colonize coastal shrubland (Brooks, 2000). Within its native range, the grass is an important component of steppes and desert vegetation in Israel, especially in the Negev Desert (Feinbrun-Dothan, 1986). In California, S. arabicus is found from 0 to 1300 m elevation (Brooks, 2000). In Arizona, S. arabicus or S. barbatus occupy an elevation of 395-1580 m (Esque and Schwalbe, 2002).
Habitat ListTop of page
|Terrestrial – Managed||Cultivated / agricultural land||Secondary/tolerated habitat||Natural|
|Disturbed areas||Principal habitat||Harmful (pest or invasive)|
|Disturbed areas||Principal habitat||Natural|
|Rail / roadsides||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Rail / roadsides||Secondary/tolerated habitat||Natural|
|Urban / peri-urban areas||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Urban / peri-urban areas||Secondary/tolerated habitat||Natural|
|Terrestrial ‑ Natural / Semi-natural||Scrub / shrublands||Principal habitat||Harmful (pest or invasive)|
|Scrub / shrublands||Principal habitat||Natural|
|Deserts||Principal habitat||Harmful (pest or invasive)|
|Arid regions||Principal habitat||Harmful (pest or invasive)|
|Arid regions||Principal habitat||Natural|
Biology and EcologyTop of page
The chromosome number was determined to be 2n=12 for plants from Israel and Libya (Faruqi and Quraish, 1979; Díaz Lifante et al., 1992).
The grass is annual and reproduces by seed. S. arabicus is self-pollinating and self-fertilizing, but it hybridizes with the closely related S. barbatus (Faruqi and Quraish, 1979). Hybrids are fully fertile.
Physiology and Phenology
Flowering time is from January to May in Arizona (Guertin, 2003). The grass will flower until water stress causes senescence (Brooks, 2000). Schismus species are winter annuals and with sufficient rain, germination can occur within two weeks (Pake and Venable, 1995). In North American deserts, S. arabicus is among the first of the winter annuals to flower and the last to die (Pake and Venable, 1995). As a desert annual and winter ephemeral depending on rainfall for germination and growth, it shows great variability in abundance from year to year.
In the southwestern USA, seed germinates in early winter (Brooks, 2000).
In its native range, germination depends on temperature, light conditions and rainfall (Gutterman, 1996a; Gutterman et al., 2010). It can germinate after early winter rains or following later winter rains. The phase of vegetative growth is longer if germination occurs early (Gutterman, 1989). Growth is controlled by day length. The grass has also been observed to germinate following summer rains in southern Egypt and Saudi Arabia (Gutterman, 1996b).
A prolonged after-ripening period is evident in S. arabicus, as the germination rate of stored seeds was higher than that of fresh seeds in plants from its native range (Gutterman, 1996a). Germination in the dark was much higher than in light in a study with seeds from the Negev Desert (Gutterman, 1996a).
Following senescence, plants may remain rooted and standing upright for up to two years. Eventually culms are detaching at the roots and are then blown across the ground (Brooks, 2000).
Population Size and Structure
Abundance of this desert annual varies greatly from year to year because growth and germination depend on rainfall. Once established it may become frequent and cover can reach 45-70% (Howard, 2006). Seed set can be high, e.g. 89 plants covering 1 square metre produced ca 10.000 caryopses (Loria and Noy-Meir, 1979/1980); this gives an average of 112 seeds per plant.
In the Central Asian Gurbantunggut Desert, the grass is colonized by arbuscular mycorrhizal fungi (Zhang et al., 2012).
S. arabicus is adapted to arid conditions. It emerges during winter and completes its life cycle in spring. In the Negev Desert of Israel, the grass completes its life cycle even in years with less than 100 mm rainfall (Gutterman et al., 2010). In the Central Asian Gurbantunggut Desert, where the grass is a native component of spring ephemerals, mean monthly temperatures range from -20° C to -15° C in January and from 22° C to 26° C in July (Zhang et al., 2012).
ClimateTop of page
|BS - Steppe climate||Preferred||> 430mm and < 860mm annual precipitation|
|BW - Desert climate||Preferred||< 430mm annual precipitation|
|Cs - Warm temperate climate with dry summer||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
|Csa - Mediterranean climate||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers, warmest month average temp. > 22°C|
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
Notes on Natural EnemiesTop of page
The smut fungus Sporisorium aegyptiacum (A.A. Fisch. Waldh.) Vánky occurs on S. arabicus in Australia (Shivas, 2010), but the fungus does not appear to cause significant damage to the plant. In the Central Asian Gurbantunggut Desert, the grass is colonized by arbuscular mycorrhizal fungi (Zhang et al., 2012).
Means of Movement and DispersalTop of page
Natural Dispersal (Non-Biotic)
Detached spikelets or tiny seeds are blown along the ground by wind. Sheet flooding in arid regions also carries seeds away. Seeds often persist within the inflorescence, which detaches after the plant has dried out and is blown across the ground (Brooks, 2000).
Vector Transmission (Biotic)
Seeds are not adapted for animal dispersal, but in Arizona harvester ants (Veromessor pergandei and Pogonomyrmex rugosus) collect seeds and carry them to their nests (Rissing, 1986). Seeds that are not consumed by ants and germinate in ant nests grow to be significantly larger plants than those growing on sites outside ant nests due to a higher nutrient content. The number of seeds per plant may be 15 times higher in ant nests than outside. In the native range of S. arabicus, ant species of the genus Messor also disperse seeds (Pisarski, 1978).
In Chile, introduced rabbits and hares appear to promote spread of the grass, probably by digging activities, causing soil disturbances, and by damaging native shrubs (Manrique et al., 2007).
As the grass grows in disturbed sites, human activities such as road and railroad construction, off-road vehicle use and urbanization will promote the spread of Schismus seeds. Seeds may also be carried by traffic wind and on clothing. In a study modelling the potential distribution of S. arabicus in Sonora, Mexico, factors associated with human-caused disturbances proved to be the best predictors (Sánchez-Flores, 2007).
Impact SummaryTop of page
Economic ImpactTop of page
In Arizona, both S. arabicus and S. barbatus are reported as weeds in fields cultivated by Pima Indians (Rea, 1997).
Environmental ImpactTop of page
Impact on Habitats
Both S. arabicus and S. barbatus can significantly alter desert ecosystems because these annual grasses accumulate fuel and hence affect fire regimes. In the Sonoran Desert, S. arabicus is considered to be an invasive grass causing serious ecological damage (Van Devender et al., 1997). Fire frequency has increased since 1970 in the Sonoran Desert region (Brooks et al., 2005). In the Mojave Desert, several wildfires in the 1990s were fueled mostly by Schismus litter (Brooks, 1999). Schismus species are not alone responsible for altered fire regimes in the Sonoran Desert but do contribute to fuel accumulation; other alien grasses present in the area such as red brome (Bromus rubens) and buffelgrass (Pennisetum ciliare) have the same effects (Esque and Schwalbe, 2002). It is thought that adventive Bromus species fuel hot, fast-moving and continuous fires, whereas Schismus fuels cooler, slower-moving and more patchy fires (Brooks, 1999).
Impact on Biodiversity
Both S. arabicus and S. barbatus compete with native annuals and grasses for water, nutients and microhabitats in the deserts of North America. Where Schismus grasses are abundant, changes in community composition and species abundances occur, further exacerbated by the grass/fire cycle (see above).
The first stems and leaves often spread out close to the ground, which may prevent other desert ephemerals from sprouting (Van Devender et al., 1997).
Alien annual grasses including Bromus spp. and Schismus spp. affect habitats of the endangered desert tortoise (Gopherus agassizii) in the Mojave Desert as a result of increased fire frequencies (Brooks and Esque, 2002). Fires result in both decreased amounts and altered seasonal availabilities of preferred food plants (US Fish and Wildlife Service, 1994). These effects cannot be attributed to S.arabicus alone, since several alien annual grasses are present in the area.
The degree to which the grass causes ecological damages is differently rated among regions. In Arizona, S. arabicus has been categorized as an invasive plant of medium risk by the Arizona Wildlands Invasive Plant Working Group (SBSC, 2012), based on a regionally developed assessment protocol. The California Invasive Plant Council rates S. arabicus as a species with limited impacts (Cal-IPC, 2012). In the Sonoran Desert, S. arabicus is among six exotic plant species potentially causing the most ecological damage (Van Devender et al., 1997).
Social ImpactTop of page
Increases in fire frequencies (see Environmental Impact) due to S. arabicus represent hazards to the public.
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Has a broad native range
- Abundant in its native range
- Is a habitat generalist
- Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
- Pioneering in disturbed areas
- Fast growing
- Has high reproductive potential
- Damaged ecosystem services
- Ecosystem change/ habitat alteration
- Modification of fire regime
- Monoculture formation
- Reduced native biodiversity
- Threat to/ loss of native species
- Competition - monopolizing resources
- Rapid growth
- Difficult to identify/detect as a commodity contaminant
- Difficult to identify/detect in the field
UsesTop of page
Similarities to Other Species/ConditionsTop of page
The closely related S. barbatus is distinguished from S. arabicus by lemmas with shorter terminal points constituting15-25% of the total length of the lemma. In S. arabicus, this value amounts to 30-50%. The presence of hairs on the lemma and the length of the palea in S. arabicus are probably the most distinct differences. Nevertheless, both species are annuals and are so similar that distinguishing them is not easy.
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Cultural Control and Sanitary Measures
Grazing is not an ideal method to contain S.arabicus, as stated by Brooks (2000). He notes that although grazing can reduce S. arabicus, Schismus biomass increases following moderate to intense grazing, because grazing animals cause soil disturbances and reduce shrub cover. This promotes further spread of the grass.
Hand removal is impractical due to the plant’s small size (Brooks, 2000). Due to the extensive mat of roots under the soil surface, pulling up the grass causes substantial soil disturbances, thereby creating conditions which encourage further establishment of S. arabicus (Brooks, 2000). The same holds for ploughing, disking or scraping. Fire generally promotes the growth of S. arabicus.
A late application of glyphosate or grass-specific herbicides has proven to be effective in killing plants (Marushia et al., 2010). If fuel accumulation and seed set are to be prevented, herbicides need to be applied at the pre-bolting rosette stage. However, the small surface area of the leaves and culms makes herbicide application difficult (Brooks, 2000).
Gaps in Knowledge/Research NeedsTop of page
Studies on the long-term ecological effects of this grass are largely lacking. The role of fires in spreading this invasive grass is not yet fully understood and here studies are badly needed. Many studies do not distinguish between S. arabicus and S. barbatus, hence exact data on local distribution and abundance of S. arabicus are often lacking.
ReferencesTop of page
Atlas of Living Australia, 2012. Atlas of Living Australia. Canberra ACT, Australia: GBIF. www.ala.org.au
Brooks ML, 2000. Schismus arabicus Nees; Schismus barbatus (L.) Thell. In: Invasive Plants of California's Wildlands. In: Schismus arabicus Nees; Schismus barbatus (L.) Thell [ed. by Bossard, C. C. \Randall, J. M. \Hoshovsky, M. C.]. Berkeley, California, USA: University of California Press. [Invasive Plants of California's Wildlands.]
Brooks ML; Belnap J; Keeley J; Sanford R, 2005. Fire and invasive annual grasses in western ecosystems. Las Vegas, NV, U. Fire and invasive annual grasses in western ecosystems. Las Vegas, Nevada, USA: Western Ecological Research Center, US Geological Survey.
Brooks ML; Esque TC, 2002. Alien annual plants and wildfire in desert tortoise habitat: status, ecological effects, and management. Alien annual plants and wildfire in desert tortoise habitat. Chelonian Conservation and Biology, 4:330-340.
Burgess TL; Bowers JE; Turner RM, 1991. Exotic plants at the desert laboratory, Tucson, Arizona. Madrono, 38:96-114.
Cal-IPC, 2012. California Invasive Plant Council. Berkeley, California, USA: Cal-IPC. http://www.cal-ipc.org/ip/inventory/weedlist.php
Devender TRVan; Felger RS; Burquez MA, 1997. Exotic plants in the Sonoran Desert region, Arizona and Sonora [ed. by Kelley, \Wagner, E. \Warner, P.]. Concord, California, USA: California Exotic Pest Plant Council. http://www.cal-ipc.org/symposia/archive/1997_proceedings.php
Diaz Lifante Z; Luque T; Barbara CS, 1992. Chromosome numbers of plants collected during Iter Mediterraneum II in Israel. Bocconea, 3:229-250.
Esque TC; Schwalbe CR, 2002. Alien annual grasses and their relationships to fire and biotic change in Sonoran desertscrub. In: Invasive exotic species in the Sonoran region [ed. by Tellman, B.]. Tucson, USA: University of Arizona Press, 194.
Feinbrun-Dothan N, 1986. Flora Palaestina. Jerusalem: Israel academy of sciences and humanities.
Felger RS, 1990. Non-native Plants of Organ Pipe Cactus National Monument, Arizona. Technical Report No. 31. Non-native Plants of Organ Pipe Cactus National Monument, Arizona. Tuscon, Arizona, USA: Cooperative National Park Research Studies Unit.
Fish and Wildlife Service US, 1994. Desert Tortoise (Mojave Population) Recovery Plan. Portland, Oregon, USA: United States Fish and Wildlife Service.
Flora of Saudi Arabia, 2012. Plant Diversity in Saudi Arabia - Checklist. Plant Diversity in Saudi Arabia. Riyadh, Saudi Arabia: Flora of Saudi Arabia (online). http://www.plantdiversityofsaudiarabia.info/Biodiversity-Saudi-Arabia/Flora/Checklist/Cheklist.htm
FloraBase, 2012. The Western Australian Flora. Western Australia, Australia: Department of Environment and Conservation. http://florabase.dec.wa.gov.au/
Fuentes N; Pauchard A; Sanchez P; Esquivel J; Marticorena A, 2012. A new comprehensive database of alien plant species in Chile based on herbarium records. first. DOI 10. A new comprehensive database of alien plant species in Chile based on herbarium records. DOI 10.1007/s10530-012-0334-6
GBIF, 2013. Global Biodiversity Information Facility. Global Biodiversity Information Facility (GBIF). http://data.gbif.org/species/
Gould F, 1951. Grasses of southwestern United States. Tucson, Arizona, USA: University of Arizona.
Guertin P, 2003. Factsheet for Schismus arabicus Nees. Factsheet for Schismus arabicus Nees. Tuscon, Arizona, USA: University of Arizona.
Gutterman Y, 1996. Effect of day length during plant development and caryopsis maturation on flowering and germination, in addition to temperature during dry storage and light during wetting, of Schismus arabicus (Poaceae) in the Negev Desert, Israel. Journal of Arid Environments, 33(4):439-448.
Howard JL, 2006. Research Project Summary: Nonnative annual grass fuels and fire in California's Mojave Desert. In: Fire Effects Information System. Nonnative annual grass fuels and fire in California's Mojave Desert [ed. by Fire Effects Information System, \[Online]]., USA: US Department of Agriculture. http://www.fs.fed.us/database/feis/
ISSG, 2012. Global Invasive Species Database (GISD). Auckland, New Zealand: University of Auckland. http://www.issg.org/database
Izquierdo I; Martin JL; Zurita N; Arechavaleta M, 2004. List of wild species of the Canary Islands (fungi, plants and land animals). (Lista de especies silvestres de Canarias (hongos, plantas y animales terrestres).) List of wild species of the Canary Islands. Canary Islands: Ministry of Environment and Spacial Planning, Canary Islands Government.
Kemp PR; Brooks ML, 1998. Exotic species of California deserts. Fremontia, 26:30-34.
Missouri Botanical Garden, 2013. Tropicos database. St Louis, USA: Missouri Botanical Garden. http://www.tropicos.org/
Pisarski B, 1978. Comparison of various biomes. In: Production Ecology of Ants and Termites. In: Comparison of various biomes [ed. by Brian, M. E.]. Cambridge, UK: Cambridge University Press, 326-331.
Sánchez-Flores E, 2007. GARP modeling of natural and human factors affecting the potential distribution of the invasives Schismus arabicus and Brassica tournefortii in 'El Pinacate y Gran Desierto de Altar' Biosphere Reserve. Ecological Modelling, 204(3/4):457-474.
Shivas R, 2010. Schismus smut (Sporisorium aegyptiacum). PaDIL (online). http://www.padil.gov.au
Southwest Biological Science Center, 2012. Invasive Non-native Plants That Threaten Wildlands in Arizona. Northern Arizona University, Arizona, USA: Southwest Biological Science Center (online). http://sbsc.wr.usgs.gov/research/projects/swepic/SWVMA/2B_AboutList.asp
USDA-ARS, 2012. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx
USDA-NRCS, 2013. The PLANTS Database. Baton Rouge, USA: National Plant Data Center. http://plants.usda.gov/
Valdes B; Scholz H, 2009. Poaceae (pro parte majore). Euro+Med Plantbase. http://ww2.bgbm.org/EuroPlusMed/
Valdes B; Scholz H, 2012. Poaceae (pro parte majore). Euro+Med Plantbase. http://ww2.bgbm.org/EuroPlusMed
Zhang Tao; Sun Yu; Shi ZhaoYong; Feng Gu, 2012. Arbuscular mycorrhizal fungi can accelerate the restoration of degraded spring grassland in central Asia. Rangeland Ecology & Management, 65(4):426-432.
Zhengyi W; Raven PH; Deyuan H, 2006. Flora of China. Vol. 22. Poaceae. Louis, MI, U. Flora of China. St Louis, Missouri, USA: Missouri Botanical Gardens.
Zuloaga FO; Morrone O; Belgrano MJ, 2008. Catálogo de las Plantas Vasculares del Cono Sur (Argentina, Sur de Brasil, Chile, Paraguay y Uruguay). Volumen 1: Pteridophyta, Gymnospermae y Monocotyledoneae (Catalogue of the vascular plants of the southern cone (Argentina, southern Brazil, Chile, Paraguay and Uruguay). Volume 1: Pteridophyta, Gymnospermae and Monocotyledoneae) [ed. by Zuloaga FO, Morrone O, Belgrano MJ]. St. Louis, USA: Missouri Botanical Garden Press, 983 pp.
OrganizationsTop of page
USA: California Invasive Plant Council (Cal-IPC), 1442-A Walnut Street, #462, Berkeley, California, CA 94709, http://www.cal-ipc.org/
ContributorsTop of page
02/01/13 Original text by:
Ewald Weber, Consultant, Germany
Distribution MapsTop of page
Unsupported Web Browser:
One or more of the features that are needed to show you the maps functionality are not available in the web browser that you are using.
Please consider upgrading your browser to the latest version or installing a new browser.
More information about modern web browsers can be found at http://browsehappy.com/