PARENT SESSION
Contributed Oral Session 147: Aquatic Communities, Disturbance, and Dispersal
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 511a, Level 5, Palais des congrès de Montréal

Plant communities of Wisconsin lakes in the 1930s and present: how have they changed?

Borman, Susan^*,1, Galatowitsch, Susan¹, Newman, Raymond¹, ¹ University of Minnesota, St. Paul, Minnesota

ABSTRACT- How do aquatic plant communities change over time and what factors influence these changes? This study adopts a landscape-level view of change over a 70-year period of time. Thirty northern Wisconsin lakes are examined that were part of an extensive survey of lakes during the 1930s. New plant surveys were conducted along with measurements of water clarity, conductivity, sediment type and surrounding land use. Land use was evaluated from aerial photographs from the 1930s and present. Water clarity remained fairly stable and species richness increased. The most notable change was a shift in the submersed plant community. During the 1930s, small-stature isoetid species represented 50% of the species. The submersed community has changed to 70% larger, elodeid species and 30% isoetids. This occurred not through the loss of isoetids, but a marked increase in elodeids. The surrounding shoreland has undergone a reduction in forested land and increase in residential use. The increase in the percentage of shoreland residential use was closely associated with the increase in elodied species. In this case, a landscape perspective and historical time frame helped understand a within-lake change in species composition.

Key words: isoetid, elodeid, shoreland