Science Fair Project Encyclopedia
The genus Tamarix, known as tamarisk or (US) saltcedar, comprises about 50-60 species of deciduous or evergreen shrubs or small trees growing to 1-15 m in height and forming dense thickets , native to drier areas of Eurasia and Africa. The largest, Tamarix aphylla, is an evergreen tree that can grow to 15 m tall. They usually grow on saline soils, tolerating up to 15,000 ppm soluble salt and can tolerate alkali conditions. Tamarisks are characterized by slender branches and gray-green foliage. The bark of young branches is smooth and reddish-brown. As the plants age, the bark becomes brownish-purple, ridged and furrowed. The leaves are scale-like, 1-2 mm long, and overlap each other along the stem. They are often encrusted with salt secretions. The pink to white flowers appear in dense masses on 5-10 cm long spikes at branch tips from March to September, though some species (e.g. T. aphylla) tend to flower during the winter.
Tamarix can spread both vegetatively, by adventitious roots or submerged stems, and sexually, by seeds. Each flower can produce thousands of tiny (1 mm 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. Tamarix species are fire-adapted, and have long tap roots that allow them to intercept deep water tables and exploit natural water resources. They are able to limit competition from other plants by taking up salt from deep ground water, accumulating it in their foliage, and from there depositing it in the surface soil where it builds up concentrations lethal to many other plants.
North American invasive species
Saltcedar was introduced to the western United States as an ornamental shrub in the early 1800s. Saltcedar establishes in disturbed and undisturbed streams, waterways, bottomlands, banks and drainage washes of natural or artificial waterbodies, moist rangelands and pastures, and other areas where seedlings can be exposed to extended periods of saturated soil for establishment.
Saltcedar disrupts the structure and stability of native plant communities and degrades native wildlife habitat by outcompeting and replacing native plant species, monopolizing limited sources of moisture, and increasing the frequency, intensity and effect of fires and floods. Although it provides some shelter, the foliage and flowers of saltcedar provide little food value for native wildlife species that depend on nutrient-rich native plant resources.
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