Thursday, May 29, 2008 - 4:15 PM
594

Are bryophytes useful indicators of hydrologic permanence in forested headwater streams?

Ken M. Fritz, U.S. Environmental Protection Agency, Office of Research and Development, National Exposure Research Division, 26 West Martin Luther King Dr., Cincinnati, OH 45268

Federal court cases have recently questioned whether all headwater streams, particularly non-perennial streams, should be protected in US under the Clean Water Act.  Rapid field-based indicators of hydrologic permanence are needed for jurisdictional determinations.  The study objective was to determine whether bryophytes in forested headwater streams are useful indicators of hydrologic permanence.  Bryophytes were sampled from the channel thalweg at 113 sites which varied in hydrologic permanence.  Species composition differed between ephemeral and perennial stream reaches; however, the species composition of intermittent streams overlapped with ephemeral and perennial streams.  Three species and six families were identified as indicators of specific permanence classes.  Liverworts occurred more frequently at perennial than at intermittent or ephemeral sites.  Bryophytes with cushion and turf growth forms were common at ephemeral sites, whereas mat and weft forms were more common at perennial sites.  Species richness was significantly higher at ephemeral than at perennial sites, but neither was significantly different from intermittent sites.  Bryophytes are recommended to be included among the tools for jurisdictional determinations, much like vascular plants are useful for delineating wetlands.  Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.


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