Wetland Site Index for summarizing botanical studies

Abstract

By a series of simple arithmetic steps, a site list of plant species is reduced to a single Wetland Site Index number. The proposed method utilizes the U.S. Fish and Wildlife Service National Wetlands Inventory (FWSNWI) list of wetland indicator species as a database, and weights each species’ contribution to the index by its relative abundance. A single number is produced, which represents the range of upland to wetland by values from zero to one, respectively. Preliminary results of fieldwork in the glaciated northeastern U.S. indicate that well drained soils produce communities with index values between 0.1 and 0.5; poorly drained soils between 0.5 and 0.7; and very poorly drained soils between 0.7 and 0.9. Permanently inundated soils (deeper swamps and marshes) produce values above 0.9. These values seem to concur well with wetland botanists’ professional judgements of each community, and it is hoped that they will be useful as the basis for land-use planning decisions, particularly where plant communities show mixtures of upland and wetland species and decisions have been previously in dispute.