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RIPARIAN
ENVIRONMENTS Riparian environments are river bank environments, although in desert regions the term tends to be used more broadly to include temporary water courses such as gullies and washes that receive run-off water from the mountains during the wet season. Even when these washes are dry, they tend to retain a higher moisture content in the soil. The result is an unusually lush vegetation compared with that on the surrounding land.
In desert regions of southwestern USA the rivers and other water courses can provide ideal habitats for invading organisms. The image below shows part of the Colorado River at Yuma (extreme south of Arizona) where the river fllod plain has been dominated by thick growth of tamarisk trees (Tamarix ramosissima and related species) which were introduced into the USA from Europe or Asia, as fast-growing trees to serve as windbreaks along fields.
Tamarisk is so successful as an invader because it produces prolific seeds which germinate readily. It displaces the native riparian trees such as mesquite, willow and cottonwood because it is much more salt-tolerant than them. It achieves this by excreting excess salt onto the leaf surfaces. Quite apart from its domination of the water courses, tamarisk is detrimental because it transpires a large amount of water - more so that desert plants that evolved to be adapted for water conservation. GO TO: |
This site is no longer maintained and has been left for archival purposes
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