Water regulation and muskrat effects on wetland plant assemblage

Water regulation (Plan 1958-D) in the Upper St. Lawrence River in the mid-twentieth century catalyzed the expansion of invasive cattails (Typha x glauca and Typha angustifolia), a decrease in muskrat (Ondatra zibethicus) populations, and degradation of coastal habitats. Although muskrats are considered ecosystem engineers, we know little about the impact of muskrat disturbance, e.g. herbivory and structure construction, on the wetland community, especially under changing environmental conditions from hydrological regulation. From 2017 to 2019, I conducted muskrat winter house counts to examine distribution patterns under the changing hydrologic regime, and surveyed vegetation in summer to assess local wetland plant biodiversity across ecological gradients related to muskrat disturbance. Muskrat house density increased over the past two decades and was positively correlated with average winter water levels. In addition, muskrat houses in managed marshes were more likely to be reoccupied annually. The wetland plant assemblage was significantly different around muskrat houses, with a higher species richness and diversity. This study showed that the muskrat disturbances (e.g., house building and herbivory) were shown to increase wetland structural heterogeneity and enhance local wetland plant diversity.

Collaborators: 

• John M Farrell (SUNY-ESF)
• Thousand Islands Biological Station (SUNY-ESF)

Related publications and presentations: (* indicates student contributor)
Kua, Z.X.*, J.M. Farrell, J.C. Stella. 2019. Muskrat (Ondatra zibethicus) effects on wetland plant communities. Oral presentation delivered at the International Association for Great Lakes Research 62nd annual Conference on Great Lakes Research, Brockport, NY.

Kua, Z.X.* 2019. Water Regulation and muskrat (Ondatra zibethicus) effects on wetland plant assemblages. MSc. Thesis. State University of New York College of Environmental Science and Forestry.