PARENT SESSION
Contributed Oral Session 64: GIS / Remote Sensing and Landscape Ecology
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 519 B, Level 5, Palais des congrès de Montréal
An aggregate response of emergent vegetation to water level fluctuations in Lake Ontario.
Wei, Anhua*,1, Chow-Fraser, Patricia1, 1 McMaster University, Hamilton, Ontario, Canada
ABSTRACT- A conventional approach to study the effect of water level (WL)fluctuations on emergent plant relates historical WL to areal changes in emergent vegetation, and this method has been successfully applied to site specific studies. However, application of this method could be problematic if multiple sites from a region experiencing the same WL are compared since the same lake elevation may correspond to vastly different inundated areas for these sites. In a previous site-specific study, we proposed the use of a Digital Elevation Model (DEM) to examine the effect of WL fluctuations on emergent plant cover (1934-1993) in a degraded freshwater marsh of western Lake Ontario. We found that changes in areal cover of emergent plants was significantly correlated with the amount of inundated area (IA), after controlling for the effect of WL fluctuation; however, there was no significant correlation between emergent cover and WL after controlling for IA. In this paper, we extend the approach to examine WL effects on vegetation cover at multiple sites in eastern Lake Ontario to validate the DEM-based method. We chose 12 sites within 28 watersheds that have experienced the same water level (variations of < 1cm among sites) during 1978 and 1980. Corresponding information on emergent vegetation for this time period were extracted from maps assembled by the National Wetland Inventory. We used a high resolution DEM to calculate the IA corresponding to mean summer WL in 1978 and 1980. Percent emergent cover was then related to IA and land-use alteration within watersheds for all sites. We found that changes in the percent emergent cover were negatively related to %IA and that %IA alone accounted for 86 to 91% of the total variation in emergent vegetation at both the site and watershed level. Results of this study support our general hypothesis that IA is better than WL for predicting emergent plant cover at both site-specific and regional scales since the former reflects both bathymetric characteristics and lake level information.
Key words: water level, disturbance, emergent marsh, wetland