Stucker 2000 abstract

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Stucker, J.H., and F.J. Cuthbert. 2000. Biodiversity of southeastern Minnesota forested streams: relationships between trout habitat improvement practices, riparian communities, and the Louisiana waterthrush. Final report submitted to the Natural Heritage and Nongame Research Program, Minnesota Department of Natural Resources. 147 pages.


Forested streams in southeastern Minnesota have a limited distribution and are managed to meet a variety of consumptive and non-consumptive objectives. One fisheries management technique is trout habitat improvement (HI). Trout HI can include substrate and bank modifications, narrowing of streams, removal of understory and canopy trees, and planting of grass. This study was conduced in Winona, Wabasha, Fillmore, Houston, and Olmsted counties in Minnesota in May through July of 1996 and 1997. The study describes avian riparian communities, aquatic invertebrates, their associations with a riparian obligate species, Louisiana Waterthrush (Seiurus motacilla), and possible impacts of trout habitat improvement projects n these species and communities. In Minnesota, Louisiana Waterthrushes are a Species of Special Concern. Point counts and nest searching techniques were used to assess the avian community and determine Louisiana Waterthrush reproductive success in May and June of each year. Concurrently, benthic aquatic invertebrates were collected using a Surber sampler, and assessed in the lab. Physical habitat assessments of the stream and stream banks were visually quantified in July of each year. The study include 20 sites in 1996, and 22 sites in 1997, covering 31.6 km of 1st - 3rd order streams. Randomization tests showed significant differences in avian communities between sites with and without trout habitat improvement and/or Louisiana Waterthrushes. Emergence of grassland and edge associated species and communities, including Brown headed Cowbirds, within areas of habitat improvement suggest loss of continuity in the forested riparian corridor. Aquatic invertebrates display greater variation in diversity and lower HBI scores (<%chironomids, >EPT) among streams with HI compared to those without. Among streams with HI Significant differences in stream physical habitats and riparian communities suggest trout habitat improvement may locally eliminate availability of several features required for Louisiana Waterthrush nesting, although no significant differences between HI and non HI sites were detected in reproductive success. Minimizing disturbance and protecting the riparian zones adjoining ephemeral 3rd order forested streams is a priority for conservation of Louisiana Waterthrushes and associated riparian communities in southeastern Minnesota.

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