The Use of Bryophytes as Indicators of Hydric Soils and Wetland Hydrology during Wetland Delineations in the United States

Abstract : Under Section 404 of the Clean Water Act, the U.S. Army Corps of Engineers is responsible for delineating wetland boundaries, using hydrophytic vegetation, hydric soils, and wetland hydrology. Current procedures for making hydrophytic vegetation determinations are based on vascular plants; the use of bryophytes is generally not recommended. However, the National Technical Committee on Wetland Vegetation is investigating the use of bryophytes as indicators of environmental conditions. This literature review examines relationships between bryophytes, hydric soils, and wetland hydrology for delineating wetlands. To determine whether hydric soils and wetland hydrology control the bryophyte species present in wetlands, bryophyte adaptations to these environmental variables are investigated. Response to soils and hydrology is considered at the microscale and the mesoscale. The consistency and reliability of bryophytes as indicators of wetland type are examined. Selected species and genera are identified as hydrophytes, and procedures for field sampling are proposed. Bryophyte identification resources and the necessity of voucher specimens are also discussed. To determine whether species composition differs with soil moisture levels, soil type, and hydrologic regime, bryophyte associations in wetlands and adjacent uplands are explored. Finally, situations in which bryophytes could be used in wetland delineations and areas that require further research are identified.