Study of Historic Air Photos Analyzes Cattail Invasion of Lake Ontario Wetlands
Ann Arbor, MI — Natural variability in lake levels provides occasional high waters in wetlands that kill tall, light-blocking cattails and invading upland plants. Periodic low lake levels create drier soils at upper elevations that can reduce invasion by moisture-requiring plants such as cattails. Exposure of soils to the air also allows seeds from other plants to germinate and grow, thus restoring habitat diversity. This natural cycling has persisted for thousands of years.
Lake Ontario water levels have been regulated since the St. Lawrence Seaway opened. The loss of natural variability allowed cattails to dominate much of the wetland area along the lakeshore and reduce fish and wildlife habitat. The International Joint Commission is using results from a large U.S.-Canadian study to evaluate new regulation plans for the lake that might reduce environmental damages.
As part of that study, plant communities in aerial photographs of 16 Lake Ontario wetlands were analyzed across five decades dating back to pre-regulation in the 1950s. Cattails invaded sedge/grass meadows at upper wetland elevations at nearly all sites. "Persistently higher lake levels keep wetland soils moist at higher elevations and remove the competitive advantage enjoyed by sedges and grasses," says Dr. Douglas Wilcox of the U.S. Geological Survey-Great Lakes Science Center. "Canopy-dominating cattails that require more water are able to survive and displace the shorter, more drought-resistant species."
Original Publication Information
Results of this study, "Cattail Invasion of Sedge/Grass Meadows in Lake Ontario: Photointerpretation Analysis of Sixteen Wetlands over Five Decades," are reported by Douglas A. Wilcox, Kurt P. Kowalski, Holly L. Hoare, Martha L. Carlson and Heather N. Morgan in the latest issue (Volume 34, No. 2, pp. 301-323) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2008.
Contacts
For more information about the study, contact Douglas Wilcox, USGS-Great Lakes Science Center, 1451 Green Rd., Ann Arbor, MI 48105;
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; editor@iaglr.org; (608) 692-1076.
Links
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.