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14 August 2013 @ 01:45 pm
wetlands  
Introduction to Wetlands with a Classification hierarchy of wetlands.

Рамсарская классификация водно-болотных угодий (рус.) и Ramsar Classification System for Wetland Type

Definition. The Emergent Wetland Class is characterized by erect, rooted, herbaceous hydrophytes, excluding mosses and lichens. This vegetation is present for most of the growing season in most years. These wetlands are usually dominated by perennial plants. All water regimes are included except subtidal and irregularly exposed.

Description. In areas with relatively stable climatic conditions, Emergent Wetlands maintain the same appearance year after year. In other areas, such as the prairies of the central United States, violent climatic fluctuations cause them to revert to an open water phase in some years (Stewart and Kantrud 1972). Emergent Wetlands are found throughout the United States and occur in all Systems except the Marine. Emergent Wetlands are known by many names, including marsh, meadow, fen, prairie pothole, and slough. Areas that are dominated by pioneer plants which become established during periods of low water are not Emergent Wetlands and should be classified as Vegetated Unconsolidated Shores or Vegetated Streambeds.
with Subclasses and Dominance Types

Emergent wetlands are marsh areas characterized by herbaceous vegetation. Common emergent vegetation includes cattails, sedges and rushes.

A quick lesson in wetland ecology

Palustrine System Emergent Wetland Class (PEM) - This type defined by the dominance of erect rooted herbaceous (not woody) wetland plants. If there is >30% cover of woody plants, then the type would be Scrub-Shrub or Forested.

Водно-болотные угодья России