Professor Gunnar Erdtman (1897-1973) popularized fossil pollen analysis in the 1920s and 1930s through both his English language publications and a lecture-collecting tour in North America. Of the cores that he lifted, he only published a pollen diagram from the "Twin Lakes Muskeg" in Itasca State Park, Minnesota (18 on map). In 1962, he told me that it was only to "illustrate diagram-drawing technique" and that since 1931 he had switched to pollen systematics.

Photo of Gunnar Erdtman (left) with G. D. Fuller and H. C. Cowles at Lake Villa, Illinois, on July 10, 1931. Gunnar’s car is a late model Plymouth. Photo copyright RLG 2004.

Map of 1930-1931 collections of G. Erdtman. He probably travelled from Alberta to Manitoba to Minnesota and Illinois. Twin Lakes Muskeg is number 18. Modified from Erdtman (1931).

In 1959, I was a student at the University of Minnesota Itasca Biology Station. I wanted to research vegetation history using fossil pollen analysis. Murray Buell of Rutgers University, who was teaching a field ecology course, said that in June 1931, as a graduate student he had helped Erdtman core in what came to be known as the Twin Lakes Bog D (Conway 1947). He said that the resulting pollen diagram (Erdtman 1943) was incomplete because the core was located along the bog margin of the basin. Murray suggested that I should locate a core beneath the central pond where the basin would be deeper and presumably have a longer record; he was right.

Erdtman's (1947) illustration of pollen grains from the Twin Lakes Muskeg. Left: Pollen grains from the surface layer: pine, spruce, alder and tamarack. Right: Pollen grains from a layer 14 feet deep, "formed probably several thousand years ago when oak forests and other deciduous trees were far more abundant than now". Shown are oak, pine, birch, hazel, blue beech, linden and alder. Not shown are herb pollen grains of wild rice and prairie plants.

Correlation of the two diagrams show that Zones 1, 2 and 3a of the Pond diagram are missing from the Muskeg diagram, surely because of a low water table during Zone 3a, a time of arid oak savanna. Moistening of the climate over the past 4,000 years caused not only succession to deciduous forest and then pine forest but also a rise in the water table, enlarging the Pond and initiating centripetal filling of the basin by "Muskeg".

Harking back to our conversation in 1962, I remember him saying, "If you want to be famous, you should not do pollen analysis, you should do pollen systematics".

Alas.

	Twin Lakes Muskeg pollen diagram, redrawn from Erdtman (1943).
	Bog D Pond pollen diagram, located about 70 m south of Erdtman's Muskeg core, redrawn from McAndrews (1966). Pollen sum is tree pollen. Sediment is gyttja with a buried soil at the base. Four 14C dates and the surface provide a chronology. The Poaceae peak in Zone 3c is from wild rice.

References cited:

Conway, V. M. 1949. The bogs of central Minnesota. Ecological Monographs 19:173-206.

Erdtman, G. 1932. Literature on pollen-statistics and related topics published 1930-1931. Geologisca Foreningens Forhandlingar 54:395-418.

Erdtman, G. 1943. An introduction to pollen analysis. Chronica Botanica, Waltham, Mass. 238pp.

Erdtman, G. 1947. Do you collect pollen? Journal of the New York Botanical Garden 48:245-253.

McAndrews, J. H. 1966. Postglacial history of prairie, savanna and forest in northwestern Minnesota. Memoirs of the Torrey Botanical Club 22:1-72.

Acknowledgements:

Thanks to John Rowley and Owen Davis for references and discussion.

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This article first appeared in CAP Newsletter 29(1):8-9, 2006. It is included here with permission of Jock McAndrews.