The influence of fluctuating water levels on the ecology and morphology of a Great Lakes archipelago

Keywords: biogeography, Canada, GIS, Great Lakes, islands, plants, vegetation dynamics
Session Type: Virtual Paper Abstract
Day: Friday
Session Start / End Time: 2/25/2022 11:20 AM (Eastern Time (US & Canada)) - 2/25/2022 12:40 PM (Eastern Time (US & Canada))
Room: Virtual 2

Abstract

The Great Lakes have a history of water-level fluctuations. A prolonged low water stage in the Huron-Michigan basin occurred from 1999-2014, with a record low in January 2013 (175.57 meters above sea level). Subsequent years showed a gradual climb above the long-term average, with near-record high levels in 2020 (177.45 m asl). In this paper, we use field and satellite/aerial imagery data spread over twenty years to analyze the spatiotemporal interplay of water-level fluctuations, shoreline configuration, and vegetation dynamics affecting plant communities on islands in Lake Huron. Utilizing the analytical tools of a geographic information system (GIS), we examined vegetation surveys and island morphology data to shed light on the applicability of the prevailing model of island biogeography in areas with changing water levels. Water levels significantly altered island area and isolation during the study period (2001 – 2021). Islands that increased in size and decreased in isolation with low water levels correlated with a greater number of plant species. Stand structures of small islands showed a pine dominance during the extended low water period. However, at the onset of the current high-water period, ~15-year-old shoreline pines became dead standing wood and forest structure shifted to an oak-pine dominance. Obtaining accurate island sizes for a region with dynamic water levels is integral for understanding the degree of influence that island area has on plant species richness. Examination of the dynamic terrestrial-aquatic interface in the Great Lakes is pertinent to many of the conservation policy issues in the region today.