Introduction
Types of Wetlands
Wetland Plants
Wetland Animals
Threats to Wetlands
Types of Wetlands
It is difficult to clearly define the different types of wetlands because many wetlands merge with other ecosystems such as ponds and meadows. Wetlands exist in places where the water table is at or near the surface of the dirt. The water table is the highest level of the ground water. When dirt is completely saturated with water the water table is at the surface and standing water will accumulate when it rains. Water can saturate the soil and rock to the depth of the impervious bedrock. If there is a drought (period without rain) the water table will drop causing the surface soil to dry.
Submergent and Floating Communities
Submergent and floating plants are truly aquatic. Submergent and emergent plants are found in the area where a marsh merges with a pond or lake. Submergent plants grow entirely under water while emergent and floating plants have part of the plant at or above the water surface. Yellow pond lilies are a common emergent plant found in Northwest wetlands. Emergent plants can not grow in water that is deeper than six feet because the water cannot support the weight of longer stems. The edge of the yellow pond lilies marks the six feet depth line, which is useful information for both swimmers and boaters.
The roots of most of these plants are in sand, gravel, silt or mud but a few are free-floating and drift with wind and water currents. These plants also grow in slow-moving rivers and streams, lakes, ponds, sloughs and pools on floodplains.
Common examples of submergent and floating plants are duckweed, watercress, pondweeds, water-milfoils and bladderwort.
Marshy Shore Communities
These plant communities are found on the muddy shores of lakes, ponds, sloughs, lagoons and streams. These plants can live in water and on muddy substrates. These communities have water at the surface for most or all of the growing season. Most of the plants in these communities are emergents. Common plants include sedges, spike-rushes, rushes and some grass species as well as American brooklime, water parsley, cattails, European yellow iris and purple loosestrife.
Channel dredging, flood control and agriculture have caused extensive losses of marshy habitats.
Prairie Wetland Communities
A prairie is a wet grassland that develops on clay soil. Although most prairies are in the Midwest and Great Plains there are areas of prairie in the Willamette and Umpqua valleys and the southern Puget Trough, south of the glacial outwash plains. Wetland prairies are filled with tufted hairgrass and other grasses as well as sedges and herbaceous species such as western buttercup and large-leaf avens. A number of prairie plants, unique to the Willamette Valley, are now threatened or endangered due to habitat destruction.
Shrub Swamp Communities
These semi-terrestrial habitats feature willow thickets and woody plants that are less than six meters tall at maturity. Common plants are red-osier dogwood, Douglas' spirea and several species of willows. Shrub swamps and brush prairies occur in floodplains and gravel bars and in stream channels. These plants can tolerate variable water flow.
Wooded Wetland Communities (also known as riparian forests)
These communities look less like wetlands because they often contain cottonwoods/dogwoods stands, ash swales and cedar swamps as well as other woody wetland plants that grow to six meters tall or taller. Woodland communities are found along streams and rivers as well as along the shores of lakes, ponds, and sloughs.
