Regional Evolution of Dalian Lake

Abstract

As same as the forest, grassland, desert and ocean, the wetland is an important integral part of global ecological environment and an ecological system with particular hydrologic, soil and biological features. Generally the wetland refers to the natural transitional zone from water to land. The word of “wetland” was firstly mentioned by U.S. Fish and Wildlife Service in the publications titled by No. 39 Notice in 1956. In which the wetland was defined as the lowland covered by the intermittent or the permanent shallow water layer. Such definition satisfies with the needs of wetland administrators and wetland scientists finitely, and thence it is still adopted and used frequently by wetland scientists and wetland administrators nowadays. In 1979, Zoltai, in a discussion meeting of Canadian National Wetland Working Party, defined the wetland into the one as follows, i.e.: “the land, where the wet soil dominates and the aquatic plants grow, but the water level approaches to or exceeds mineral soil in the majority days in the unfrozen seasons”. The definition made by the Canadian for the word of “wetland” limits the hydrologic conditions and wet soil conditions more concretely. Upon years’ investigation, the wetland scientists of U.S. Fish and Wildlife Service defined the wetland as the one as follows, i.e.: “the wetland is a transitional zone of the terrestrial system and the aquatic system; on these lands, the water level is normally on or approaches to the earth’s surface, or is covered by the shallow water”.