ARCUS | Arctic Research Consortium of the United States

6th Annual ARCUS Award for Arctic Research Excellence

Submitted by		W. Wyatt Oswald
Authors		W. Wyatt Oswald, L.B. Brubaker, F.S. Hu, and D.G. Gavin
Category		Life Science
Title		Pollen-vegetation calibration for arctic tundra communities in the Brooks Range foothills, northern Alaska
Affiliation		College of Forest Resources, University of Washington, Seattle, WA, USA

Abstract

Palynology has been portrayed as too "blunt" to reveal variations in arctic tundra vegetation. The analysis of 56 modern lake-sediment pollen assemblages tests this characterization for the northern foothills of the Brooks Range in northern Alaska. In the Toolik Lake area, repeated glacial advances have resulted in a complex pattern of different-aged land surfaces. The Sagavanirktok (>125,000 years BP) and Itkillik II (>11,500 years BP) glacial surfaces have considerably different landforms, soil characteristics, and plant communities. We used two multivariate methods, discriminant analysis and distance metrics (square chord distance and Canberra metric), to assess the ability of pollen data to distinguish between the Sagavanirktok and Itkillik II surfaces. Several taxa were encountered more frequently on one surface or the other. Taxa associated with the Sagavanirktok surface and moist acidic tundra included Rubus chamaemorus, Sphagnum, and Ericales, whereas Equisetum, Polypodicaceae, and Thalictrum were faithful to the Itkillik II surface and moist non-acidic tundra. Such differences made it possible to differentiate quantitatively between the two landscapes using discriminant analysis and the Canberra distance metric. Receiver operating characteristic (ROC) curve analysis demonstrated that the Canberra metric was more effective than square chord distance for distinguishing between Sagavanirktok and Itkillik II samples. This calibration study illustrates that palynology can be used to explore questions regarding the landscape-scale heterogeneity of past arctic tundra vegetation.