Waterloo Creek is one of the premier trout streams in
NE Iowa. In August 2004, a major habitat reconstruction project involving stream bank stabilization and rehabilitation, and conversion of corn fields, grassy old fields, and wooded riparian areas to tallgrass prairie is occurring at the confluence of Waterloo Creek and Duck
Creek in NE Iowa. Beginning in 2003 prior to the reconstruction, we sampled ground beetle assemblages with pitfall traps and butterflies with a visual survey to provide baseline data beginning in 2003. As of 2005,
25 species of butterflies (an increase from only 11 species in 2003 and 8 species in 2004) have been found during July transect surveys. Currently, 29 species of ground beetles have been found on site by pitfall trapping (2005 samples are still being processed).
We hypothesize that as the tallgrass prairie planting this winter (2005-06) becomes established in former old field, corn field, and riparian areas, both butterfly and ground beetle diversity (richness and abundance) will continue to increase. Future monitoring will quantify long-term changes and correlate plant species richness and productivity with insect community diversity.
Tree cover along Waterloo
Creek hides extensive stream bank erosion. The banks were eroding due to inadequate root support from the box elder trees with shallow roots and the reed canary grass that dominated the banks.
Following removal of the box elder trees and reed canary grass, tallgrass prairie plants on the newly stabilized banks such as prairie cordgrass grow thick, deep root networks that stabilize and hold the banks, reducing erosion and improving reproductive habitat for the trout.
Ground beetles (Coleoptera: Carabidae) have been sampled using 18 oz cup pitfall traps. Twelve pitfall traps have been placed in each of the former corn field and old field riparian areas for one-week sampling periods in June, July & August beginning in 2003. In the corn field in 2003, only 8 species were found, but in
2004, these areas were fallow with a more diverse annual weed community beginning to develop and hosted 17 species of ground beetle with a reduction in the abundance of common agricultural species typically found in corn such as
and
. Thus there was a significant change in the ground beetle assemblage in corn field areas from 2003 to 2004 (t=16.56; df=316; p<0.001). In the grassy old field areas dominated by brome grass, there was no significant change from 2003 to 2004 in the abundance or diversity of ground beetles (t=1.65; df=213; p=0.09) but there also was little observed change in the plant community composition.
This 98-acre site located at the confluence of Waterloo
Creek and Duck Creek, 1 km NW of Dorchester in
Allamakee County, Iowa, includes valley bottom formerly planted to corn and soybeans, and overgrown oak savanna forest. Since 2003, we have been monitoring aquatic insect communities in the streams, and butterfly populations and ground beetle communities in the former corn and old field riparian areas as the habitat reconstruction has began. Future monitoring will continue as the prairie and savanna areas become reestablished.
A 1,500 m long sampling transect across the riparian area of the property has been established, and monitored for butterfly activity each July since 2003. All butterflies observed or collected in an approx. 5 m wide band along the transect were identified to species and counted. Before any work was done, the site was dominated by corn, box elder trees, and reed canary grass. Only 11 species of butterflies were found on-site in 2003. In 2004, following removal of the box elder trees and spraying of reed canary grass with the corn fields left fallow, annual weeds were just beginning to emerge after extensive earthmoving. The butterfly populations took a hit in 2004, with only 8 species being present, and only 6 of those species being found in both
2003 and 2004. This did result in a significant change in this small butterfly community from 2003 to 2004
(t=2.13; df=52; p=0.04). In 2005, after some prairie areas had been planted, and many native prairie plants appeared from the seed bank, we had a significant change (t=1.99; df=51; p=0.049) in the butterfly community with a jump to 25 species and a 10X increase in butterfly abundance over previous years.
The ongoing reconstruction of a more diverse riparian habitat along Waterloo Creek has reduced erosion into the stream, improved trout habitat, and is changing the terrestrial insect communities along the stream. The prairie reconstruction is increasing butterfly and ground beetle species diversity and abundance. As the prairie seeding on most of the site becomes established during
2006, we expect to see an even greater jump in overall terrestrial species diversity and insect abundance as evidenced by these indicator groups. Ongoing studies carried out by the Luther College biology department will continue to monitor ongoing changes in the plant and insect communities at this site.
Generous financial support for this project has come primarily from Dr. Michael Osterholm. Additional funds for summer undergraduate research positions were provided by the R.J. McElroy Trust Student/Faculty
Research Fund and Luther College Summer
Undergraduate Student-Faculty Collaborative Research
Program. Collaborators include the Iowa DNR, USDA-
NRCS, Trout Unlimited, and Driftless Land Stewardship.
Luther biology students Katie Hopp, Deneb Wood,
Derek Broman, Mike Thompson and other students have contributed to the ongoing collection and analysis of data for this project.