Tuesday, June 5, 2007
492

Effects of experimental large wood addition on stream geomorphology in three Northern Michigan streams

Kyle Pfeifer1, Emma J. Rosi-Marshall1, Jennifer L. Tank2, Timothy J. Hoellein2, Sally A. Entrekin2, and Gary A. Lamberti2. (1) Biology, Loyola University Chicago, Chicago, IL 60626, (2) Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556

Large wood (LW) has been shown to influence stream morphology, hydrology, and sediment deposition.  As part of a larger study looking at the influence of LW on stream ecosystem function, we examined the role of log addition on channel morphology and substrate composition.  In May 2004, we added 25 logs (2.43m X 0.48m) to 100m reaches in three streams in Northern Michigan.  For 3yrs since adding logs, we have seasonally measured channel profiles and substrate types along 10m spaced cross-sections.  To examine individual log effects at a smaller scale, we added transects immediately above and below each log. Relative substrate distributions associated with each log were compared to random transects in control and treatment reaches (Chi-Squared test) and log-associated substrate composition was significantly different than random transects (p<0.05).  Logs changed the relative distribution of substrates (i.e. gravel, cobble, and sand) and had more small wood than other transects. We quantified the extent of pools, riffles, and depth throughout the channels using interpolation software (GS+©). Pool depth increased upstream of logs as did depositional areas where logs were in contact with stream banks. Large wood addition altered both channel morphology as well as having localized effects on substrate distributions. 

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