The Response of Organic Matter Dynamics and Macroinvertebrates to Experimental Wood Additions in Three Michigan Streams

Restoration ecology is guided by basic ecological principles derived from population, community, and ecosystem ecology. As the human population grows and more land is developed; the need of restoration of freshwater ecosystems has and will grow. Stream ecosystems are often altered by changes in land use, and many headwater streams now drain logged, urbanized, or agricultural watersheds. In these systems, wood and boulders are often removed and channels straightened to accelerate drainage for development, but these modifications can result in increased frequency of downstream flooding and continued habitat deterioration. One of the most common restoration activities in streams is to add in-stream structures, such as flow defectors, boulders, wood, and vegetation to stabilize banks, reduce erosion, increase habitat complexity, and retain organic matter. My goal was to assess changes in organic matter standing stocks and decomposition, secondary production, and macroinvertebrate food web structure following an experimental addition of large wood to three small forested streams. I determined that macroinvertebrate secondary production was low in these streams before wood addition, likely from a legacy of intensive logging, which reduced in-stream habitat diversity and organic matter standing stocks. After wood addition, I measured an increase in organic matter standing stocks around the added logs, but no reach-scale responses and no changes in organic matter decomposition. Decomposition was affected by water temperature, scour and burial by sediments, and changes in water column nutrient concentrations. Macroinvertebrate responses were site-specific, with secondary production increasing in two streams and declining in one stream after wood addition. The stream-specific response was likely mediated by the amount of increased organic matter retention and substrate sorting due to log additions as well as differences in water temperature, mean annual discharge, and stream bed substratum. Furthermore, in one stream, I measured an increase in total macroinvertebrate consumption of both autochthonous (i.e., algae) and allochthonous (i.e., leaves) carbon as a result of the changes caused by the added logs. My research incorporated population, community, and ecosystem ecology to more effectively link changes in habitat and community structure to changes in ecosystem function within the context of a restoration.