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A Survey of Insects in the West Eugene Wetlands, funded by BLM

Executive Summary

The purpose of this Challenge Cost Share project is to collect and compare insect assemblages at selected wetland sites using a combination of light traps and water traps (fallout traps). Insects will be sorted to order, counted, and selected groups (Hymenoptera, Trichoptera, Plecoptera and Ephemeroptera) identified to lower taxonomic resolution (family, genus or species).

There is a current need to monitor, classify, and analyze wetlands in order to assess management techniques, mitigation projects, restoration efforts, land-use impacts, and environmental contaminants. Aquatic insect larvae are frequently used as biological indicators in freshwater ecosystems because they are a diverse group that responds to environmental conditions in a predictable fashion. However, the use of aquatic insects as integrative, biological indicators has been largely restricted to lakes, rivers, and streams; perhaps due to difficulties associated with sampling immature insects in wetlands. Sampling in wetlands is difficult and can be destructive to wetland vegetation. Taxonomic

identification at the genus and species level can be quite difficult, especially for some groups of immature insects (e.g., Trichoptera). In spite of these difficulties associated with the sampling of immature insects, there are many advantages to the use of insects to characterize wetlands. First, insects are ubiquitous in wetlands throughout the world and information exists on their ecological requirements and tolerance to environmental stress. Second, insects respond quickly to change and integrate environmental variability over their life span; therefore, unlike most physical characters, insects can be used to measure past, as well as present, conditions. Finally, insects provide a measurement that is not directly manipulated by managers, as opposed to vegetation and various vertebrate taxa.

We initiated this survey of insects at the West Eugene Wetlands in 2001. We are sampling, using both light traps and fallout traps, at six locations at two sites.


S. Balboa Site

N44 02.984, W123 10.740

This is the site of an old airstrip, which was removed 4 years ago. At this site, we are sampling insects in a restored wet prairie, an emergent marsh, and a remnant wet prairie. The remnant wet prairie is now covered with blackberries and shrubs and a controlled burn or brush hogging is planned. There are several small areas of cattail near the restored runway.

Emergent Marsh

Greenhill Site

N44 03.779, W 123 12.528

This site has multiple landowners: ODOT owns 60 acres near the tracks and BLM and the City of Eugene own the rest. This site has multiple year restoration areas and a remnant wet prairie. Near the NW corner is the older area (seeded in 1999 with 50-60 species) now in its third growing season. There are a number of transplants and experimental plots (mychorhizae and fertilized plots) in this area. Some of these areas are being restored and managed using a combination of solarization, shallow discing, burning and hand weeding.

We are sampling insects in the south central portion of the site, which has a 1 year old restoration site. We are also sampling at a remnant wet prairie near the eastern side (between a drainage ditch and the road) that is somewhat wooded and an untreated agricultural area along the western side of the site.

Hand weeding teams in the 1 yr old restoration area at the Greenhill site.