Tuesday, June 5, 2007 - 8:00 AM
100

Stream macroinvertebrate secondary production responds to an experimental wood addition in the Upper Peninsula of Michigan

Sally A. Entrekin1, Emma J. Rosi-Marshall2, Jennifer L. Tank1, Timothy J. Hoellein1, and Gary A. Lamberti1. (1) Biological Sciences, University of Notre Dame, 292 Galvin, Notre Dame, IN 46615, (2) Department of Biology and Natural History, Loyola University Chicago, 6525 N. Sheridan Road, Chicago, IL 60626

Historic wood removal associated with logging has altered habitat heterogeneity and reduced organic matter retention and processing in Michigan streams. Restoration of instream structure has been attempted, but the effects of restoration on ecosystem function, such as aquatic macroinvertebrate secondary production, are rarely assessed.  We added 25 large logs to each of three forested streams with a history of logging. Macroinvertebrate secondary production was estimated from monthly benthic samples one year before and one year after log addition in both upstream control and downstream treatment reaches (replicated BACI design).  We predicted that added instream structure would increase secondary production via increased organic matter retention but after one year, we did not observe significant increases in reach-scale organic matter or total secondary production.  However, more detailed analysis showed increased organic matter accumulation around added logs, and concurrent increases in secondary production of two macroinvertebrate predators, Alloperla and Hexatoma.  In contrast, scraper (e.g. Glossosoma) secondary production decreased post one year, which may correspond to changes in substrate distribution in the treatment reaches. Thus far, the effects of wood addition on organic matter and invertebrates have been scale dependent, emphasizing the need for multiple levels of investigation when assessing stream restoration.

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