II. The Hydrology of Wetlands

Water is one of the primary factors that organizes the landscape, doing so through processes such as transport, erosion, leaching, solution, and evapotranspiration (Brown 1985). The hydrologic regime of a wetland is one of the key variables that determine the composition, distribution, and diversity of wetland plants. Hydrologic conditions affect species composition, successional trends, primary productivity, and organic matter accumulation (Gosselink and Turner 1978; Brinson et al. 1981; Howard-Williams 1985; van der Valk 1987). Factors related to the hydrologic regime that affect wetland plant communities include water depth (Spence 1982; Grace and Wetzel 1982, 1998), water chemistry (Ewel 1984; Pip 1984; Rey Benayas et al. 1990; Rey Benayas and Scheiner 1993), and flow rates (Westlake 1967; Lugo et al. 1988; Nilsson 1987; Carr et al. 1997). Hydrology also influences the plant community composition and primary productivity by influencing the availability of nutrients (Neill 1990), soil characteristics (Barko and Smart 1978, 1983), and the deposition of sediments (Barko and Smart 1979). The hydrologic regime can be thought of as a master variable with respect to all these factors since it not only determines the hydroperiod, but it is also instrumental in carrying nutrients and sediment (and so modifying soil type) into a wetland.