Wednesday, August 8, 2007 - 2:50 PM

COS 85-5: Short-term effects of diversion dam decommissioning and flow restoration on leaf litter decomposition, fungal biomass, and macroinvertebrate abundance and diversity in Fossil Creek, Arizona, USA

Jeffrey D. Muehlbauer1, Carri J. LeRoy2, Jacqueline M. Lovett1, Kathleen K. Flaccus3, Julie K. Vlieg3, and Jane C. Marks1. (1) Northern Arizona University, (2) The Evergreen State College, (3) Sinagua High School

Dam decommissioning projects, although numerous, rarely include complete sets of adequate pre-restoration data, making it difficult to evaluate the ecological consequences of restoration actions.  In this study, we used a before-after control-impact (BACI) design to assess changes in leaf litter decomposition and characteristics of associated decomposers including macroinvertebrates and fungi following flow restoration in Fossil Creek, Arizona.  Using leaf litter bags we compared these variables in a relatively pristine site above the dam with a highly disturbed site below the dam where over 90 percent of the flow was diverted.  Six months after restoration, we found that leaf litter decomposition was slightly slower below the dam than above the dam both before and after restoration, indicating that decomposition was not affected by increased flow.  In contrast, both macroinvertebrates and fungi differed significantly above and below the dam prior to restoration but were similar post-restoration.  This suggests that decomposer communities can quickly rebound following restoration.  These results indicate that some aquatic ecosystem variables can return to a more pristine state following ecological restoration activities such as water flow restoration, but that the extent and timing of such a response may be process-dependent.

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