Exposed riverine sediments

Exposed riverine sediments

Exposed riverine sediments, or ERS, are composed of silt, sand and gravel deposited by streams but exposed as water level falls.

Other terms for ERS include river shingle, point bars, berms and shoals and they are most common in actively meandering and braided rivers.Adrian Fowles of the Countryside Council for Wales and members of the UK Environment Agency in 1993 coined ‘exposed riverine sediments’ as a term to describe the full scope of these related microhabitats. Their aim in-so-doing was to reduce confusion and pull together the conservation and scientific investigation of these habitats. Bates and Sadler (2005)Bates, A.J., and J.P. Sadler. 2005. "The ecology and conservation of beetles associated with exposed riverine sediments". CCW Contract Science Report No.688.] have since further defined exposed riverine sediments as:

"Exposed, within channel, fluvially deposited sediments (gravels, sands and silts) that lack continuous vegetation cover, whose vertical distribution lies between the levels of bankfull and the typical baseflow of the river."

Therefore, eroding river banks are ERS because they are usually composed of fluvially deposited sediment. Whereas areas of the stream bed and over-bank deposits are not ERS because they are only exposed when water levels are unusually low and are more elevated than the bankfull level respectively.

The term ERS is slowly becoming more common and has now been used in a large number of published papers, for example:
* [http://www3.interscience.wiley.com/cgi-bin/abstract/72511990/ABSTRACT Petts et al. 2000]
* [http://www.springerlink.com/content/r6758388728t728l/?p=e5d1ccdc10c342518d44b909b8f7b4df&pi=1 Eyre et al. 2001]
* [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V5X-4B0WKCP-6&_user=122868&_coverDate=06%2F30%2F2004&_alid=623379167&_rdoc=1&_fmt=summary&_orig=search&_cdi=5798&_sort=d&_docanchor=&view=c&_ct=1&_acct=C000010083&_version=1&_urlVersion=0&_userid=122868&md5=357608d2d5936f84ce913d2e0838acd5 Sadler et al 2004]
* [http://www3.interscience.wiley.com/cgi-bin/abstract/114099188/ABSTRACT Looy et al. 2005]
* [http://www.blackwellpublishing.com/book.asp?ref=9781405151214 Tockner et al. 2006]
* [http://www.springerlink.com/content/g267083701r54386/?p=7f561071cc514ad7a111206330cc2244&pi=5 Bates et al. 2006]

ERS habitat

A casual glance at ERS would suggest a harsh, relatively un-inhabited habitat with little value. However, ERS habitats are of considerable conservation importance because of their high species diversity, high degree of species specialisation, and large number of rare and endangered species. ERS are of substantial importance for a small number of vertebrate species, such as the rare Little Ringed Plover, but for the most part their value lies in their invertebrate fauna.

The United Kingdom Biodiversity Action Plan, for example, lists eight species of beetle:
* [http://www.ukbap.org.uk/UKPlans.aspx?ID=336 "Bembidion testaceum"] . "See also" "in Wikispecies".
* [http://www.ukbap.org.uk/UKPlans.aspx?ID=336 "Lionychus quadrillum"]
* [http://www.ukbap.org.uk/UKPlans.aspx?ID=336 "Perileptus areolatus"] . "See also" "in Wikispecies".
* [http://www.ukbap.org.uk/UKPlans.aspx?ID=336 "Meotica anglica"] . "See also" "in Wikispecies".
* [http://www.ukbap.org.uk/UKPlans.aspx?ID=336 "Thinobius newberyi"] . "See also" "in Wikispecies".
* [http://www.ukbap.org.uk/UKPlans.aspx?ID=336 "Hydrochus nitidicollis"] . "See also" "in Wikispecies".
* [http://www.ukbap.org.uk/UKPlans.aspx?ID=275 "Dyschirius angustatus"] . "See also" "in Wikispecies".
* [http://www.ukbap.org.uk/UKPlans.aspx?ID=145 "Bidessus minutisimus"] . "See also" "in Wikispecies".and two species of stilleto fly:
* [http://www.buglife.org.uk/conservation/currentprojects/projectsfliesofsandyexposedriverinesediments.htm Southern silver stiletto-fly] ( [http://www.ukbap.org.uk/UKPlans.aspx?ID=225 "Cliorismia rustica"] )
* [http://www.buglife.org.uk/conservation/currentprojects/projectsfliesofsandyexposedriverinesediments.htm Northern silver stiletto-fly] ( [http://www.ukbap.org.uk/ukplans.aspx?ID=583 "Spiriverpa lunulata"] ).that are associated with ERS.

ERS dynamics

ERS rely on a continued supply of sediment from upstream, and periodic disturbances from flooding to prevent ecological succession to more vegetated riparian habitat.

Threats to ERS

Many of the threats to ERS act to:
#reduce the supply of sediment by interrupting its downstream transfer:
##dam construction
##construction aggregate extraction
##reducing river erosion (river engineering and dam construction)
#reduce the frequency and magnitude of floods (dam construction) (Plachter and Reich 1998 [Plachter, H. and M. Reich. 1998. The significance of disturbance for populations and ecosystems in natural floodplains. In "Proceedings of the International Symposium on River Reastoration", 26-27 May, Tokyo, Japan.] , Sadler et al 2005, Tockner et al. 2006 [*Tockner, K., A. Paetzold, U. Karaus, C. Claret, and J. Zettel. 2006. "Ecology of braided rivers". Pages 339-359 in G. Sambrook-Smith, J. Best, S. Lane, and G. E. Petts (editors) Braided Rivers. IAS Special Publication 36, Blackwell Publishing, Oxford.] ).

Other threats operate over smaller scales, such as livestock trampling [Bates, A.J., J.P. Sadler, and A.P. Fowles. 2007. Livestock trampling reduces the conservation value of beetle communities on high quality exposed riverine sediments. "Biodiversity & Conservation" 16:1491-1509.] [ [http://www.springerlink.com/content/128218k432n17342/?p=a1bdd0e3aa2542a2b74e353ae350dcee&pi=3 Bates et al. 2007] )] .

References

Further general reference material

*Bates, A.J., J.P. Sadler, and A.P. Fowles. 2006. Condition-dependent dispersal of a patchily distributed riparian ground beetle in response to disturbance. "Oecologia" 150:50-60.
*Eyre, M. D., M. L. Luff, and D. A. Phillips. 2001. The ground beetles (Coleoptera: Carabidae) of exposed riverine sediments in Scotland and northern England. "Biodiversity & Conservation" 10:403-426.
*Looy, K. V., S. Vanacker, H. Jochems, G. de Blust, and Dufrêne. 2005. Ground beetle habitat templets and riverbank integrity. "River Research & Applications" 21:1133-1146.
*Petts, G. E., A. M. Gurnell, A. J. Gerrard, D. M. Hannah, B. Hansford, I. Morrissey, P. J. Edwards, J. Kollmann, J. V. Ward, K. Tockner, and B. P. G. Smith. 2000. Longitudinal variations in exposed riverine sediments: a context for the ecology of the Fiume Tagliamento, Italy. "Aquatic Conservation: Marine and Freshwater Ecosystems" 10:249-266.
*Sadler, J. P., D. Bell, and A. P. Fowles. 2004. The hydroecological controls and conservation value of beetles on exposed riverine sediments in England and Wales. "Biological Conservation" 118:41-56.


Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • Triassic Period — Interval of geologic time, с 248–206 million years ago, that marks the beginning of the Mesozoic Era. Many new vertebrates emerged during the Triassic, heralding the major changes that were to occur in both terrestrial and marine life forms… …   Universalium

  • river — river1 riverless, adj. riverlike, adj. /riv euhr/, n. 1. a natural stream of water of fairly large size flowing in a definite course or channel or series of diverging and converging channels. 2. a similar stream of something other than water: a… …   Universalium

  • Asia — /ay zheuh, ay sheuh/, n. a continent bounded by Europe and the Arctic, Pacific, and Indian oceans. 2,896,700,000; ab. 16,000,000 sq. mi. (41,440,000 sq. km). * * * I Largest continent on Earth. It is bounded by the Arctic Ocean, the Pacific Ocean …   Universalium

  • GEOGRAPHICAL SURVEY — Names The name Ereẓ Israel (the Land of Israel) designates the land which, according to the Bible was promised as an inheritance to the Israelite tribes. In the course of time it came to be regarded first by the Jews and then also by the… …   Encyclopedia of Judaism

  • hydrosphere — /huy dreuh sfear /, n. the water on or surrounding the surface of the globe, including the water of the oceans and the water in the atmosphere. [1885 90; HYDRO 1 + SPHERE] * * * Discontinuous layer of water at or near the Earth s surface. It… …   Universalium

  • arctic — arctically, adv. /ahrk tik/ or, esp. for 7, /ahr tik/, adj. 1. (often cap.) of, pertaining to, or located at or near the North Pole: the arctic region. 2. coming from the North Pole or the arctic region: an arctic wind. 3. characteristic of the… …   Universalium

  • Wetland — For other uses, see Wetland (disambiguation). The Florida Everglades massive wetland system in the United States saw 1.7 billion gallons of fresh water flushed from it daily and pumped into the ocean following one of the most successive water… …   Wikipedia

  • Australia — /aw strayl yeuh/, n. 1. a continent SE of Asia, between the Indian and the Pacific oceans. 18,438,824; 2,948,366 sq. mi. (7,636,270 sq. km). 2. Commonwealth of, a member of the Commonwealth of Nations, consisting of the federated states and… …   Universalium

  • Marine habitats — Coral reefs provide marine habitats for tube sponges, which in turn become marine habitats for fishes Littoral zone …   Wikipedia

  • Constructed wetland — Vertical Flow type of Constructed Wetlands A constructed wetland or wetpark is an artificial wetland, marsh or swamp created as a new or restored habitat for native and migratory wildlife, for anthropogenic discharge such as wastewater,… …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”