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MEETING 1998 |
Definition and Types
of "Wetland"
Proposed on 25 March, 1998, to the IMCG Greifswald Workshop
by
Ronald Hofstetter
Department of Biology
University of Miami, Coral Gables, FL USA
Definition of "Wetland"
WETLAND is a kind of ecosystem in which, due to saturation by water, anaerobiosis of the upper soil/sediment/ sedentate (especially the rhizosphere) has selected for biota tolerant of that condition and has promoted development of hydric soil characteristics, and in which water levels are usually within 2 m of the sediment surface, especially during periods of plant growth.
"Those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas."
Federal Manual for Identifying and Delineating Jurisdictional Wetlands (1989) US-EPA, 40 CFR 230.3 and CE, 33 CFR 328.3.
1) vegetation (of the kind and/or amount) that may or may not be peat-producing,
2) animals as the dominant biota, and
3) sediment/sedentate that may be organic or mineral.
1) "Mire"
2) "Wetland-Not-Mire" [no term yet identified]
The distinction between these types is not always clear.
"MIRE" is a kind of wetland in which the current vegetation and surface waters are isolated from underlying mineral sediments by a sufficiently thick layer of organic soils and whose current natural vegetation and surface conditions promote the accumulation of a kind of organic sediment/sedentate called peat.
[I know of no mire that is characterized primarily by animals.]
1) there is an inadequate layer of organic sediment/ sedentate to isolate current vegetation and surface waters from underlying mineral sediments and/or
2) current natural vegetation and surface conditions do not promote the production and/or preservation of an organic sediment/sedentate.
(i.e., all those kinds of wetland that are NOT mire)
1. peat-producing vegetation and peat-preserving conditions exist, but the current vegetation and surface waters are not isolated from the underlying mineral sediment, because the
a) site is (too) young, [This kind may become a mire in time.]
b) peat sediment/sedentate was once thicker, but has thinned as a result of drainage and exposure to decomposing forces. [This type may have been, but is no longer a mire.]
or because the
2. peat-producing vegetation and/or peat-preserving conditions have not existed and do not now exist at this site, so the current vegetation and surface waters are not isolated from the underlying mineral sediment. [This kind of wetland has not been a mire and will not be a mire if this vegetation and these conditions persist.]
"PEATLAND" refers to a geographic area where the surface sediments/sedentates are predominantly organic and are called peat. Because the presence of peat-forming vegetation is not required, "peatland" is not a kind of "wetland" (and "wetland" is not a kind of "peatland").
"Wet lands" and "peat lands" are terms that are also distinct from "wetland".
Types of wetlands may be distinguished by
1. Vegetation -
physiognomy of the dominant vegetation (e.g., forest)
dominant plant community (e.g., Caricetum lasiocarpae),
dominant species (e.g., Carex lasiocarpa),
species diversity/richness (e.g., monospecific);
2. Sets of Current Abiotic Factors -
sediment/sedentate types (e.g., sedge peat),
sources of water (e.g., minerogenous),
surface topography (e.g., sloped),
nature of water movement (e.g., slow, subsurface),
pH classes (e.g., acid),
available nutrients (e.g., oligotrophic);
or by
3. Other factors (e.g., origin and genesis); or
4. Combinations of the above factors.
Sediments
Sediment/sedentate may be of:
Current Source of Surface Water
Current surface and near-surface water may be
Current Surface Water Movement
Flow of surface and near-surface water may be
Current Plant Physiognomy
The dominant vegetation may be:
Current Surface Topography
The current sediment surface may be:
Current Sediment Surface Topography
convex:
Position in the Landscape
Wetlands may occur as:
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