Correspondence between Vegetation and Soils in Wetlands and Nearby Uplands

Abstract

The association between vegetation and soils from a geographically broad sampling of wetlands and adjoining uplands is reported for 38 hydric and 26 nonhydric soils, as recognized in the hydric soils list of the Soil Cortservation Service. Wetlands represented in the study include estuaries, pitcher plant bogs, prairie depressional wetlands, and western riparian lands. The agreement between vegetation and soils is clear with few exceptions. In general, hydric soils support hydrophytic plant communities, and nonhydfic soils support upland communities. Only 10% of the hydric soils sampled support upland communities and only 15 % of the nordlydric soils support wetland communities. Exceptions to the correspondence between vegetation and soils are discussed; local hydrology, the transitional nature of some soils, and other determinants of wetland vegetation structure (e.g., salinity, disturbance) seem to account for many of the observed discrepancies. A method that simplifies the complexity of soils and vegetation cannot be expected to represent accurately all details of their interrelations.

Use of created Wetland delineation and weighted averages as a component of assessment

“…Weighted averages have been described as useful for assessing wetland status of some vegetation types along a moisture gradient for wetland delineation under natural conditions (Carter et al 1988, Wentworth et al 1988, and Scott et at. 1989.…”

“…Indicator categories, probability ranges, and indicator index values for vegetative species occurrence in wetlands (Reed 1988 (Wentworth et al 1988), also termed community index (Scott et al 1989), using the following formula (Jongman et al 1987 Since indicator categories range from 1 to 5, plot indicator status does also. Thus, a plot composed of all obligate wetland species would have a status of 1; a plot of all obligate upland species would have a status of 5.…”

“…Scott et al (1989) found vegetation WA highly correlated with soil conditions in natural wetlands. Soil characteristics in created wetlands considered in this study were more similar to those of uplands than wetlands.…”

“…For direct gradient analysis of vegetation along a single environmental gradient, such as moisture, weighted averages (WA) may be used (Whittaker 1978). Weighted averages have been described as useful for assessing wetland status of some vegetation types along a moisture gradient for wetland delineation under natural conditions (Carter et al 1988, Wentworth et al 1988, and Scott et al 1989. Weighted averages are also used in the "Comprehensive Onsite Determination Method" described in the Federal Manual, where it is referred to as a "'prevalence index" and is an optional method for determination of the vegetation parameter.…”

The primary indicators method—A practical approach to wetland recognition and delineation in the United States

“…Fish and Wildlife Service studies have further confirmed traditional scientific opinion and observations that there is an excellent correlation between "hydrophytic vegetation" and "'hydric soils" for determining the presence of wetlands (Dick-Peddie et al 1987, Erickson and Leslie 1987, Baad 1988, Christensen et al 1988, Eicher 1988, Hubbard et at. 1988, Nachlinger 1988, Allen et al 1989, Scott et al 1989, Best et al 1990, Segetquist et at. 1990, Veneman and Tiner 1990.…”