DIFFERENTIATING BETWEEN LAKE-EFFECT CLIMATE, REGIONAL PALEOCLIMATE AND EDAPHIC FACTORS IN INTERPRETING THE HOLOCENE-AGE POLLEN RECORD OF MINER LAKE, LOWER MICHIGAN, USA

Miner Lake (42.7°N, 85.8°W) in Allegan County, southwestern Lower Michigan, is located 30 km east of Lake Michigan. At present, the area is dominated by Fagus-Acer (beech-maple) forest and a lake-mediated climate characterized by higher snowfall, warmer winter temperatures, and cooler summer temperatures than inland locations. Our research objective was to test whether lake-effect climate was a more dominant influence on the local vegetation of the study area during the Holocene than regional paleoclimate patterns or local soil textural properties. We analyzed sediment cores from Miner Lake for pollen and compared these data to the published pollen record of Wintergreen Lake, Kalamazoo County, situated farther inland at the same latitude (42.4°N, 85.38°W) and beyond strong lake-effect influence. Our analysis considered soil texture, which can affect tree species dominance independent of climate, by characterizing and comparing the surficial geology within a 20-km radius of both Miner and Wintergreen Lakes.

The Wintergreen Lake catchment contains a higher percentage of coarse-textured soils (93%), as compared to the Miner Lake catchment (71.8%), explaining the greater abundance of xeric-adapted Quercus (oak) in both the modern and presettlement (ca. A.D. 1800) forests surrounding Wintergreen Lake, as well as its relative abundance in the Holocene pollen record of this lake. In contrast, the predominance of mesic-adapted Fagus on coarse-textured soils in both modern and presettlement forests in the Miner Lake catchment is anomalous. Fagus normally prefers moist, fine-textured soils, its growth on excessively drained, coarse-textured soils can only occur under favorable moisture and humidity conditions typical of areas under lake-effect influence. In addition, the Miner Lake pollen record is dominated by other mesic taxa including Acer, Ulmus (elm), and Tsuga (hemlock), a cool-adapted conifer. The pollen record of Miner Lake was apparently unresponsive to the reported regional "megadrought" that occurred from 4300 to 4100 cal. yr BP. Together these data suggest that a distinct lake-effect climate induced by nearby Lake Michigan was a more dominant control on the vegetation of the Miner Lake area than were regional paleoclimatic perturbations or local soil conditions during the Holocene.