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Primary Succession in Wetlands

Wetlands are regions which are characterized by water saturated soils which are characterized by particular water loving plant species. Such regions are often highly prized by ornithologists for their diversity of bird life, such as terns, herons and grebes. Primary succession in wetlands occurs when a region transitions from being barren and devoid of most plant and animal life to developing an established community, which facilities the colonization of subsequent species.
  1. Definition of a Wetland

    • A wetland is defined as an area in which water covers the soil, or is at least present close to the upper soil layer or near the root zone, throughout the year. The presence of water in surface soils is a primary factor in determining soil development and the types of flora and fauna that inhabit the region. Wetlands are often identified by the presence of hydrophytes, which are types of plants which are adapted to flooded or saturated soil conditions.

    Definition of Primary Succession

    • Primary succession encompasses the series of community level changes which occur in a habitat which previously was bare of most life, with no soil present at this stage. It is the first stage in colonization and is found in the wake of areas such as where retreating glaciers are present, after a volcano has erupted or where new river deltas are evolving. Primary succession is characterized by plant and animal species which are able to rapidly colonize this often barren environment and later give way to successive colonizers.

    Primary Succession in Wetlands

    • Glaciers were responsible for forming wetlands in two primary ways: by leaving behind chunks of ice to melt and inundate the surroundings, and by leaving glacial run-off water in depressions in which the bottom was sealed by organic material and fine clays. Primary succession in wetlands is effected by both environmental conditions in the wetland region and the distance from surrounding ecosystems. Early colonizers generally arrive by wind or are transported by migratory or wandering species. If neighboring populations of plants are more distant, then the chances of a propagules, which are plant material used for plant propagation, reaching the wetland area is remote. Thus, some wetland regions may take longer to be colonized than others.

    Autogenic View of Wetland Primary Succession

    • In the autogenic (self-generating) view of wetland primary succession, early biotic colonizers, such as plankton, live, reproduce and die, creating an accumulation of organic material which builds up to the surface, until the region is no longer flooded. These early colonizers help create conditions which are favorable to support other flood-tolerant species, such as hydrophytes.

    Wetland Succession as a Transitional Stage

    • An environment may progress from the open-water stage, where plants are submerged, into a wetland primary succession stage, where floating plant species may be present, through an emergent swamp stage where flood tolerant plants are present, to a sedge grass stage, a shrub stage where the ecosystem is no longer classified as a wetland, and finally to a tree stage. In the early stages of wetland primary succession, initial colonizers are often microscopic organisms, and biodiversity is low. However, as succession continues, larger and more complex organisms appear, and biodiversity increases.

    Examples of Wetlands

    • Alaska, the most northerly U.S. state, contains extensive areas of wetlands, in total covering 43.3 percent of its area. This compares to an average of 5.2 percent in the contiguous 48 states. The majority of these wetlands were created as a result of the melting of vast North American ice sheets at the end of the Ice Age and thus experienced primary succession. These wetlands support a huge variety plant and animal species and are particularly abundant in waterfowl. They support over 12,000 swans and over 12 million ducks, and the regions importance to such species increases when the prairie regions to the south experience extended periods of drought.


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