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<br />Figure 6 - Majorelemems of the Hydrological <br />Cycle in floodplains. <br /> <br /> <br /> <br />Evaporation & <br />Transportation <br /> <br />Groundwater Recharge <br />& Movement <br /> <br />that coexist in a certain area. The various plant species within an ecological commu- <br />nity may share the need for a certain soil type or level of soil moisture that is available <br />only in a particular portion of the floodplain. Wet meadows, bottomland hardwood <br />forests, and riparian shrub wetlands are examples of such communities. The bound- <br />aries of these ecological communities can be identified by the landform, soil. and plant <br />types that cover a portion of the floodplain. <br /> <br />Summary - This section has introduced floodplain natural resources with an explana- <br />tion of floodplains, watersheds, ecosystems and natural communities. The basic char- <br />acteristics of floodplains and their natural resources function in ways that make them <br />so valuable to humans and to wildlife. This is the subject of the next section. <br /> <br />How Do Natural Floodplain Systems Function? <br /> <br />The Floodplain Ecosystem - Floodplain ecosystems are typified by the bottomland <br />hardwood forests found in southern regions of the U.S., the floodplain forests of central <br />and eastern areas, and small wooded areas and stream bank vegetation in the western <br />portion of the country. Each f1.oodplain ecosystem has specific conditions that make it <br />unique, and it is important to recognize these distinctive attributes when planning <br />projects for a given area. But there are some general characteristics that are common to <br />the functions of ecosystems in stream and river corridors. <br /> <br />Hydrology - Flooding is extremely important to the maintenance of floodplain ecosys- <br />tems, and may be the primary reason for their biological richness. Floodwaters carry nutri- <br />ent-rich sediments and trigger chemical processes that cause beneficial changes in the soil, <br />which contribute to a fertile environment for vegetation. The degree of soil saturation from <br />flooding (and resulting elevated groundwater levels) determines the types of vegetation that <br />can grow throughout the floodplain and can create wetlands along stream channels. This is <br />especially im(XJrtant in dry climates, where water is a particularly limiting factor for vegeta- <br />tion. In these areas, floodplains may be far more biologically productive than surrounding <br />upland areas, which are often drier. <br /> <br />IIID <br />