Tamarix | |
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Tamarix aphylla in its natural habitat in Revivim, Israel | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Order: | Caryophyllales |
Family: | Tamaricaceae |
Genus: | Tamarix L. [1] |
Species | |
See text |
The genus Tamarix (tamarisk, salt cedar, taray) is composed of about 50–60 species of flowering plants in the family Tamaricaceae, native to drier areas of Eurasia and Africa. [2] The generic name originated in Latin and may refer to the Tamaris River in Hispania Tarraconensis (Spain). [3]
They are evergreen or deciduous shrubs or trees growing to 1–18 m (3.3–59.1 ft) in height and forming dense thickets. The largest, Tamarix aphylla , is an evergreen tree that can grow to 18 m (59 ft) tall. They usually grow on saline soils, [4] tolerating up to 15,000 ppm soluble salt, and can also tolerate alkaline conditions. [5]
Tamarisks are characterized by slender branches and grey-green foliage. The bark of young branches is smooth and reddish brown. As the plants age, the bark becomes gray-brown, ridged and furrowed. [4]
The leaves are scale-like, almost like that of junipers, [6] 1–2 mm (1/20" to 1/10") long, and overlap each other along the stem. They are often encrusted with salt secretions. [4]
The pink to white flowers appear in dense masses on 5–10 cm (2" to 4") long spikes at branch tips from March to September, [4] [7] though some species (e.g., T. aphylla) tend to flower in the summer until as late as November. [8]
Tamarix aphylla can spread both vegetatively, by submerged stems producing adventitious roots, and sexually, by seeds. Each flower can produce thousands of tiny (1 mm; 1/20" diameter) seeds that are contained in a small capsule usually adorned with a tuft of hair that aids in wind dispersal. Seeds can also be dispersed by water. Seedlings require extended periods of soil saturation for establishment. [9] Tamarisk trees are most often propagated by cuttings. [10]
These trees grow in disturbed and undisturbed streams, waterways, bottom lands, banks, and drainage washes of natural or artificial water bodies, moist rangelands and pastures.[ citation needed ]
Whether Tamarix species are fire-adapted or not is unclear, but in many cases a large proportion of the trees are able to resprout from the stump after fires, although not notably more so than other riverine species. They likely cannot resprout from root suckers. In some habitats where they are native, wildfire appears to favour the establishment of riverine trees such as Populus , to the detriment of Tamarix. Conversely, they do appear to be more flammable, with more dead wood produced and debris held aloft. In the southwestern USA, most stands studied appear to be burning at faster intervals than they can fully mature and die of natural causes. [11]
Tamarix species are used as food plants by the larvae of some Lepidoptera species including Coleophora asthenella which feeds exclusively on T. africana. [12]
In some specific riparian habitats in the Southwestern United States and California, Tamarix ramosissima has naturalized and become a significant invasive plant species. [11] In other areas, the plants form dense monocultures that alter the natural environment and compete with native species already stressed by human activity. [23] Recent scientific investigations have generally concluded that the primary human-caused impact to desert riparian ecosystems within the Colorado River Basin is the alteration of the flood regime by dams; Tamarix ramosissima is relatively tolerant of this hydrologic alteration compared to flood-dependent native woody riparian species such as willow, cottonwood, and box elder. [24]
Research on competition between tamarisk seedlings and co-occurring native trees has found that Tamarix seedlings are not competitive over a range of environments, [25] [26] [27] but stands of mature trees effectively prevent native species' establishment in the understory, due to low light, elevated salinity, and possibly changes to the soil biota. [28] [29] Box elder ( Acer negundo , a native riparian tree) seedlings survive and grow under higher-shade conditions than Tamarix seedlings, and mature Tamarix specimens die after 1–2 years of 98% shade, indicating a pathway for successional replacement of Tamarix by box elder. [30] Anthropogenic activities that preferentially favor tamarisk (such as changes to flooding regimens) are associated with infestation. [31] [32] [33] To date, Tamarix has taken over large sections of riparian ecosystems in the western United States that were once home to native cottonwoods and willows, [34] [35] [36] [37] and are projected by some to spread well beyond the current range. [38]
In a 2013 study which examined if native plant growth was hindered by the microbiota associated with the presence of Tamarix, a relatively new invasive plant to the northern United States, Elymus lanceolatus and other native plants in fact grew better when a small soil sample from areas where Tamarix trees grew was mixed in with the potting soil, as opposed to samples without these plants. This was thought to indicate the presence of beneficial mycorrhizae. The presence of Tamarix plants has also been shown to boost soil fertility in a number of studies, and it also increases soil salinity. Two studies found that Tamarix plants are able to limit the recruitment of Salix and Populus tree species, in the latter case possibly due to interfering with the trees ability to form symbiotic relationships with arbuscular mycorrhizal fungi, in contrast to the grass and legume species studied in 2013. [39]
Because it is much more efficient at both obtaining water from drying soil and conserving water during drought, it can outcompete many native species, especially after the habitat is altered by controlling flood regimes and disturbance of water sources. [23] Because the trees are able to concentrate salts on the outside of their leaves, dense stands of the tree will form a layer of high salinity on the topsoil as the leaves are shed. [23] Although this layer is easily washed off during flooding events, in areas where the rivers are channelled and floods are controlled, this salty layer inhibits the germination of a number of native plants. [11] However, a study involving more than a thousand soil samples across gradients of both flood frequency and Tamarix density concluded that "flooding may be the most important factor for assessing floodplain salinity" and "soils under Tamarix canopies had lower surface soil salinity than open areas deprived of flooding suggesting that surface evaporation may contribute more to surface soil salinity than Tamarix". [40]
Tamarix species are commonly believed to disrupt the structure and stability of North American native plant communities and degrade native wildlife habitat, by outcompeting and replacing native plant species, salinizing soils, monopolizing limited sources of moisture, and increasing the frequency, intensity, and effect of fires and floods [ citation needed ]. While individual plants may not consume larger quantities of water than native species, [41] [42] large, dense stands of tamarisk do consume more water than equivalent stands of native cottonwoods. [43] An active and ongoing debate exists as to when the tamarisk can out-compete native plants, and if it is actively displacing native plants or it just taking advantage of disturbance by removal of natives by humans and changes in flood regimens. [44] [45] [46] [47] [48]
Pest populations of tamarisk in the United States can be dealt with in several ways. The National Park Service has used the methods of physically removing the plants, spraying them with herbicides, and introducing northern tamarisk beetles ( Diorhabda carinulata ) in the national park system. Various attempts to control tamarisk have been implemented on federal lands including Dinosaur National Monument, San Andres National Wildlife Refuge, and White Sands Missile Range. [49] [50] After years of study, the USDA Agricultural Research Service found that the introduced tamarisk beetles ( Diorhabda elongata ) eat only the tamarisk, and starve when no more is available, not eating any plants native to North America. [51]
The tamarisk was introduced to the United States as an ornamental shrub, a windbreak, and a shade tree in the early 19th century. In the 1930s, during the Great Depression, tree-planting was used as a tool to fight soil erosion on the Great Plains, and different trees were planted by the millions in the Great Plains Shelterbelt, including salt cedars. [53] [54]
Eight species are found in North America. They can be divided into two subgroups: [9]
Tamarix aphylla (Athel tree), a large evergreen tree, does not sexually reproduce in the local climate and is not considered a seriously invasive species. [9] The Athel tree is commonly used for windbreaks on the edge of agricultural fields and as a shade tree in the deserts of the Southwestern United States. [55]
The second subgroup contains the deciduous tamarisks, which are small, shrubby trees, commonly known as "saltcedars". These include T. pentandra, T. tetrandra, T. gallica, T. chinensis, T. ramosissima and T. parviflora. [9]
The willow flycatcher is a small insect-eating, neotropical migrant bird of the tyrant flycatcher family native to North America.
A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a riparian zone. The word riparian is derived from Latin ripa, meaning "river bank".
Populus deltoides, the eastern cottonwood or necklace poplar, is a species of cottonwood poplar native to North America, growing throughout the eastern, central, and southwestern United States as well as the southern Canadian prairies, the southernmost part of eastern Canada, and northeastern Mexico.
Populus trichocarpa, the black cottonwood, western balsam-poplar or California poplar, is a deciduous broadleaf tree species native to western North America. It is used for timber, and is notable as a model organism in plant biology.
Tamarix aphylla is the largest known species of Tamarix, with heights up to 18 metres (59 ft). The species has a variety of common names, including Athel tamarisk, Athel tree, and Athel pine. It is an evergreen tree, native across North, East, and Central Africa, through the Middle East, and into parts of Western and Southern Asia.
Atriplex lentiformis is a species of saltbush.
Tamarix ramosissima, commonly known as saltcedarsalt cedar, or tamarisk, is a deciduous arching shrub with reddish stems, feathery, pale green foliage, and characteristic small pink flowers.
Diorhabda carinulata is a species of leaf beetle known as the northern tamarisk beetle, which feeds on tamarisk trees from southern Russia and Iran to Mongolia and western China. This beetle is used in North America as a biological pest control agent against saltcedar or tamarisk, an invasive species in arid and semiarid ecosystems.
Tamarix gallica, the French tamarisk, is a deciduous, herbaceous, twiggy shrub or small tree reaching up to about 5 meters high.
Diorhabda elongata is a species of leaf beetle known as the Mediterranean tamarisk beetle (MTB) which feeds on tamarisk trees from Portugal and Algeria east to southern Russia. The MTB is used in North America as a biological pest control agent against saltcedar or tamarisk, an invasive species in arid and semi-arid ecosystems.
Diorhabda carinata is a species of leaf beetle known as the larger tamarisk beetle which feeds on tamarisk trees from Ukraine, eastern Turkey and Syria east to northwest China, Kyrgyzstan and Pakistan, extending as far south as southern Iran. It is used in North America as a biological pest control agent against saltcedar or tamarisk, an invasive species in arid and semi-arid ecosystems.
Diorhabda sublineata is a leaf beetle known as the subtropical tamarisk beetle (STB). The species was first described by Hippolyte Lucas in 1849. It feeds on tamarisk trees from Portugal, Spain and France to Morocco, Senegal, Algeria, Tunisia, Egypt, Yemen, and Iraq. It is used in North America as a biological pest control agent against saltcedar or tamarisk, an invasive species in arid and semi-arid ecosystems.
Canebrake Ecological Reserve is a 6,700-acre (27 km2) nature reserve in the South Fork Valley of Kern County, 20 miles (32 km) east of Lake Isabella, California. It is located in the Southern Sierra Nevada region.
Populus fremontii, commonly known as Frémont's cottonwood, is a cottonwood native to riparian zones of the Southwestern United States and northern through central Mexico. It is one of three species in Populus sect. Aigeiros. The tree was named after 19th-century American explorer and pathfinder John C. Frémont.
Riparian-zone restoration is the ecological restoration of riparian-zonehabitats of streams, rivers, springs, lakes, floodplains, and other hydrologic ecologies. A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the fifteen terrestrial biomes of the earth; the habitats of plant and animal communities along the margins and river banks are called riparian vegetation, characterized by aquatic plants and animals that favor them. Riparian zones are significant in ecology, environmental management, and civil engineering because of their role in soil conservation, their habitat biodiversity, and the influence they have on fauna and aquatic ecosystems, including grassland, woodland, wetland or sub-surface features such as water tables. In some regions the terms riparian woodland, riparian forest, riparian buffer zone, or riparian strip are used to characterize a riparian zone.
Tamarix chinensis is a species of tamarisk known by the common names five-stamen tamarisk and Chinese tamarisk or saltcedar. It is native to China and Korea, and it is known in many other parts of the world as an introduced species and sometimes an invasive noxious weed. It easily inhabits moist habitat with saline soils. It may grow as a tree with a single trunk or as a shrub with several spreading erect branches reaching 6 metres or more in maximum height. It has been known to reach 12 metres. It has reddish, brown, or black bark. The small, multibranched twigs are covered in small lance-shaped, scale-like leaves which are no more than about 3 mm long. The inflorescence is a dense raceme of flowers a few cm long. Each fragrant flower has five petals which are usually pink but range from white to red.
Desert riparian is a North American desert vegetation type occurring in the bottoms of valleys, canyons, and other watercourses that have water at or near the surface most of the year. The visual character is of large, lush, perennial green trees surrounded by dry desert vegetation and soil coloration. The area may be in a patch surrounding a spring such as an oasis, or in a strand following the course of water flow, such as a bosque. The soil in this biome is typically moist and ranges from rocky and sandy to silty alluvium. This biome has seasonal variation, with hot, dry summers and cool, moist winters. Precipitation mostly occurs during the winter, and ranges from 8 to 25 cm each year. It is contrasted with the desert dry wash vegetation type, in which water at or near the surface is lacking most of the year, such as arroyos.
Flora of the Colorado Desert, located in Southern California. The Colorado Desert is a sub-region in the Sonoran Desert ecoregion of southwestern North America. It is also known as the Low Desert, in contrast to the higher elevation Mojave Desert or High Desert, to its north.
The Azerbaijan shrub desert and steppe is a deserts and xeric shrublands ecoregion in western Asia. It lies in the lowlands west of the Caspian Sea, and covers portions of Azerbaijan, Georgia, and Iran.
Anna Amelia Sher is an American plant ecologist who is a professor at the University of Denver. She works on conservation and the restoration of areas invaded by Tamarix. She is the author of two textbooks, Ecology:Concepts and Applications and Introduction to conservation biology.