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Index to the habitat - coastal vegetated shingle
Shingle is the term applied to sediments larger in diameter than sand but smaller
than boulders. At a regional scale, the type of rock determines shingle availability
and durability. Hard materials such as flint, chert, granite, quartzite, and
some metamorphic materials survive much longer at the size range of >2mm
- <200mm (which helps to define shingle) than sandstones, limestones or shells.
Geomorphologists and ecologists have recognised five categories of shingle
structures three assigned to shingle beaches and two shingle structures (Chapman
1976). They vary in their oceanicity
and therefore in their ecology. Shingle, as defined above, can thus be considered
in two geomorphologically recognisable landforms, namely:
- Shingle
beaches, which are common and geographically widespread where they
occur. They often fringe exposed coastal areas, protecting the land behind.
They may be precursors to larger structures. In the most exposed locations
they are devoid of vegetation, though they can support ephemeral
vegetation during periods when the surface remains stable;
- Shingle
structures, which are scarce and much less widely distributed.
They develop when a series of beaches are piled upon each other and progressively
moved out of reach of all but the most severe storms. They can remain stable
for many (sometimes hundreds of years) during which time soils can build up
and with it vegetation
including grassland, heathland and scrub.
NB These two types are not mutually exclusive and the simple shingle
beach can and in most case must act as a precursor to the more stable shingle
structure. The type
of structure that develops in a particular area depends on a number
of environmental factors. The range
of vegetation and associated animals, notably birds
and invertebrates
is considerable and help to make this a significant nature conservation resource.
The worldwide
distribution is restricted to the more northerly and southerly latitudes where
suitable-sized gravel deposits are available and in areas of high wave energy
(Pye 2001). The resource is widely distributed
in GB, representing a major proportion of that present
in Europe.
Comment: The distinction between sand dunes (sediment size <2mm)
and shingle (sediment size >2mm derives from the method by which the grains
are moved: in the former wind is the principle agent; whilst for the latter
it is wave energy.
References
Chapman, V.J.
1976.
Coastal Vegetation. Pergamon Press, Oxford, 245 pp.
Pye, K.
2001.
The nature and geomorphology of coastal shingle.
In: Ecology & Geomorphology of Coastal Shingle, eds.Packham, J.R., Randall, R.E., Barnes, R.S.K. & Neal, A.Westbury Academic and Scientific Publishing, 2-22.
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