Tuesday, May 19, 2009
198

Macroinvertebrate communities, organic matter, and physical habitat conditions across headwater streams of the otter river, a northern hardwoods watershed in Michigan's upper peninsula, USA

Andrew F. Burgess, South Dakota Dept. of Game, Fish and Parks, 523 E. Capitol Ave., Pierre, SD 57501 and Casey J. Huckins, Biological Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931.

This research examined relationships between land use, organic matter standing stocks and macroinvertebrate composition across streams with a range of 3-11 years since adjacent forests were last selection logged (YSC).  Results revealed that riparian canopy cover, substrate size and fall, coarse benthic organic matter standing stocks were all significantly lower in study reaches adjacent to forests more recently logged, while discharge was higher.  In contrast, overall macroinvertebrate composition (total biomass, Hillsenhoff tolerance index, Shannon Diversity index and EPT index) was not significantly correlated with YSC across study sites.  We did not detect a direct relationship between detritivore (collector-gatherers or shredders) biomass and YSC, local stream physical habitat or organic matter standing stocks.  However, the community composition and individual biomass of detritivores did vary significantly with reach and adjacent landscape factors and organic matter standing stocks.  Gatherer community composition appears to be associated with key traits providing physical tolerance and/or trophic flexibility to disturbances generated across the watershed, while taxa individual condition was correlated with reach-scale factors associated with trophic conditions. These trends suggest that selective logging is having an impact on stream physical and organic matter dynamics and indirectly influencing the composition and individual condition of local detritivore communities.


Web Page: selection logging, detritivores, bentic organic matter

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