Wetland Classification Chapter 8
Why wetlands are classified • Mainly to assign a value to each type of wetland as funds to protect them are often in short supply. • By classifying them we can prioritize their importance for restoration or maintenance. • For proper mapping and inventory • To have a uniform understanding of their characteristics.
General Classification • They can be divided into coastal and inland wetlands. • Coastal wetlands consist of tidal fresh and salt marshes and mangrove areas • Inland wetland systems consist of peatlands, freshwater marshes, riparian systems, and freshwater swamps. • These cover most, but not all wetlands.
Circular 39 • Circular 39 was distributed by the fish and wildlife service who were concerned with the wildlife habitat. • Inland fresh areas • Inland saline areas • Coastal fresh areas • Coastal saline areas • Under these categories, they were further subcategorized by their water depth and inundation time. • Only salinity was used in this classification and soils were largely ignored.
Peatland Classifications • Earliest classifications of peat bogs order them according to: • Where was the bog established. i.e. lakes or deltas. • Was it developed inward from the shores or from the bottom up. • The vegetation composition at the surface. • Others use the amount of outside drainage.
Coastal Wetland Classification • H. T. Odum used stresses and forming functions to classify coastal wetlands. • Type A- naturally stressed systems • Type B- natural tropical ecosystems like mangrove swamps • Type C- Natural temperate ecosystems with some seasonal programming • Type D- Arctic ecosystems with ice stress • Type E- Emerging systems associated with human activity.
Fish and Wildlife Service • Created more than 20 years after Circular 39 • They were classified into systems- which showed similar hydrologic and geologic features, subsystems, and classes. • For classes, when the area is covered by 30% or more vegetation, a vegetation class is used. Otherwise, a substrate class is used.
Subsystems • Subtidal- submerged substrate • Intertidal- intermedianttly submerged by tides • Tidal- Low gradient riverbanks with tidal influence • Lower Perennial- Low gradient riverbanks with no tidal influence • Upper perinnial- High gradient, continuous flow, to tidal influence. • Limnetic- Deepwater lake habitats • Liiioral- From the shore to 2m below water so long as no particular plant life dominates.
Systems • Marine- Ocean • Estuarine- Wetlands with access to the ocean and tidal habits. • Riverine- Channeled wetlands • Lacustrine- wetlands mostly pertaining to a lake or lakeshore which: • Lack of trees and shrubs • Palustrine- the opposite of Lacustrine, wetlands which are dominated by trees and shrubs and are non-tidal
Hydrogeomorphic • Uses the combination of geomorphic, water sources, and hydrodynamics (water fluctuations) • Geomorphic settings • Depressions- getting water from precipitation • Peatlands • Fringe- Estuaries and Lacustaries with in and outflow • Riverine- mostly riparian streams and river areas • Water Source • Precipitation • Groundwater • Surface inflow • Hydrodynamics • Vertical fluctuation- evapotranspiration and groundwater replacement • Unidirectional- surface flow corresponding to gradient • Bidirectional- tidal and groundwater fluctuations