Wetland Succession—Bog Succession
Wetland
is a comprehensive term for landforms such as salt marshes, swamps, bogs,
prairie potholes, etc. Their common feature is that they are wet at least part
of the year and as a result have a particular type of vegetation and soil. Wetlands
help recharge groundwater. Wetlands are natural filters that help purify water;
plants in wetlands trap sediment and toxins. They provide habitat for many
species listed as endangered or threatened.
Fig.: Wetland
Bog
Succession
A
bog is a body of water with no surface outlets at all and hence waters have
little current.
Succession
in a bog is a process that begins with open water and ends with a forest (Figure). Bog succession can be observed
easily because the pond fills in from the edges toward the center. The center
is successionally the youngest, and the bog’s original edge is the oldest. In
the quiet waters of the open part of a bog, sedge plants form floating mats
that grow out over the water’s surface. These short-lived shrubs are the
pioneers. Their mat of thick, organic matter forms a primitive soil into which
seeds of other plant species fall and germinate. Meanwhile, sediments build up
on the bog bottom made up of dead organic matter from aquatic animals and
plants as well as organic material that flows in from surface streams or is
blown in by the wind.
The
bog slowly fills in from the bottom to the top. Eventually the floating mat and
sediments meet to form a base firm enough to support trees. The first trees
that can survive under these conditions are adapted to wet grounds. If the
process continues undisturbed, the entire bog fills in and a raised, heavily
organic soil forms, in which other trees can survive. In some cases, the bog
disappears and the area is taken over by tree species that are characteristic
of mature forests on the well-drained soils.
In
other cases, open water or a moss-covered wetland with some open water can
persist. Wetlands can persist for very long periods without completely filling
in.
Fig.: Bog succession
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