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Holocene paleoenvironments of Isle Royale National Park

Investigators:
Kenneth L. Cole, USGS Colorado Plateau Research Station, Northern Arizona University.
Robyn L. Flakne, Department of Forest Resources, University of Minnesota, MN
James R. Myers, Conservation Ecology Program, University of Minnesota, MN
Marjorie G. Winkler, Center for Climate Dynamics, University of Wisconsin, WI
Daniel R. Engstrom, St. Croix Watershed Research Station, Marine on St. Croix, MN

Funding:
National Biological Service Global Change
Research Program

Summary:

    The environmental history of Isle Royale (vegetation map) since the last ice age is being reconstructed using lake sediments (last 10,000 years) and General Land Office Survey records (last 150 years).  Fossil pollen and diatoms from five sediment cores from lakes and bogs on Isle Royale detail the environmental history of the island. A core from Lily Lake, in the heart of the deciduous forest on the southwestern end of the island, documents the 9400 years of history since the island was first deglaciated (pollen diagram). This record demonstrates gradual shift from spruce to pine forest around 8500 years ago. Around 4500 years ago birch and maple increase at the expense of pine, gradually increasing to their present dominance at this end of the island. An 8800 year core from Lake Ojibway, on the northeastern end of the island, documents past changes on the boreal portion of the island.

    Ecological changes during the last 300 years are being reconstructed in order to determine what happened on the island as a result of settlement by an industrialized society.  Fossil pollen from detailed short cores of Wallace Lake, Lake Ojibway, and Lily Lake document changes brought about by mining, logging, trapping, and the introduction of exotic plants and animals.  Although some environmental impacts occurred during the settlement period, the island was changed very little compared to forest change elsewhere in the Great Lakes states.  Records from the 1847 General Land Office Survey demonstrate that much of the island's deciduous forest was converted to an aspen-birch forest by a severe fire in 1936 (figure contrasting 1847 and modern deciduous forests).   Records of  earlier nineteenth century fires were found both in the 1847 survey data and the fossil charcoal data.  These nineteenth century fires were likely set by miners to clear the vegetation in preparation for prospecting (figure).  The fossil charcoal data (figure) show the 1936 and nineteenth century fires, but also suggest that the boreal portion of the island had burned about every 100 years, prior to the time of settlement.   

Publications:

Myers, James R. and Kenneth L. Cole.  Vegetation dynamics and human disturbance on Isle Royale: implications of the General Land Office survey. Bulletin of the Ecological Society of America, 76. (Text)

Flakne, Robyn. L. and Kenneth L. Cole. 1995. The Holocene landscape history of Isle Royale. Bulletin of the Ecological Society of America, 76: 81. (Text)

Cole, Kenneth L., R. L. Flakne, D. R. Engstrom, and D. E. Harlow. 1997. Three hundred years of vegetation change and fire history on Isle Royale, MI. Bulletin of the Ecological Society of America, Vol. 78: 70. (Text)

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