Spatial and Temporal Variation in Lake-effect Snow Control Vegetational Distributions in the Great Lakes Region PDF Download

Author: Paul D. Henne
Publisher:
ISBN: 9780542988684
Category :
Languages : en
Pages : 242

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Book Description
Recent declines in the amount and duration of snow in the Northern Hemisphere are anticipated to continue as a result of greenhouse warming. The consequences of such changes for northern forests are uncertain. The Great Lakes region offers a unique setting to examine spatial and temporal variability in snowfall abundance and the impact of such variability on vegetational distributions. Lake-effect snowfall produces a threefold gradient (100--300 cm) in this region. I compared the importance of lake-effect snow relative to a suite of environmental factors as a predictor mesic-species abundance using a geographic information system and predictive modeling. Lake-effect snow, not soil texture, is the dominant control of regional mesic-forest distribution on the modern landscape. Mesic species dominate on all landform types (e.g. till, outwash) inside the lake-effect snowbelt, whereas they are restricted to fine-textured landforms outside the snowbelt. I also determined when lake-effect snowbelts developed during the Holocene by comparing oxygen-isotope data from one snowbelt and one non-snowbelt lake. These sites share similar climatic histories during the early Holocene. However, between 8500 and 5500 cal yr B.P., increasing lake-effect snow caused 18O-depletion at the snowbelt lake relative to the non-snowbelt lake, with the largest changes occurring after 6900 cal yr B.P. These differences lessened after 5500 cal yr B.P. but the snowbelt site continued to receive more snowfall. I integrated these isotopic data with pollen analysis from two snowbelt and two non-snowbelt lakes. One lake in each snowfall regime is situated on till and the other on outwash. Vegetational change was synchronous among these sites during the early Holocene prior to snowbelt development. A shift to mesic-hardwood forests after 5500 cal yr B.P. occurred only at the snowbelt sites. Snowfall variability was a more important constraint on vegetational change than edaphic variation.