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pH) and peatlands (acid, completely organic soils). But both have many
points in common regarding their location, their biological functions and
their environmental interest.
Fig. 12.10 Left: highly contrasted redox mottles in the mottled zone of a Ferralsol ( photo :
A. Ruellan). Right: a spectacular Histic Stagnosol with a thick, black, organic A horizon
(low mineralization), a very white iron-depleted B horizon and a C horizon coloured orange
by iron oxides. Sarthe Department, France ( photo : J.C. Favrot).
12.5.1 Marshes and Peatland Localization
Admittedly, low temperature acts to slow down mineralization of
carbonaceous materials. But the principal factor in formation of marshes
and peatlands is the permanent saturation with water in absence of
oxygen. This is why they are found not only in the mountains or in the
northern zones of the Earth but also in the tropical zone.
Coastal lagoons and marshes . These wetlands are the most diverse. Each
coastal lagoon has specific sediments and hydrologic regime. Salinity
is also variable.
Pond areas are often man-made reservoirs.
Alluvial wetlands are located in the main bed of streams (areas that
can become flooded in times of spate). On hard rock in cold temperate
climate, the action of ice of glacial periods generated debris and easily
transported them to the footslope by colluviation and solifluction. But
Types of wetlands
 
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