Vegetation history of a polygonal peatland, northern, Yukon

Abstract

Pollen, macrofossils and matrix composition are described for a 221 cm core from a polygonal peatland overlying a late‐Wisconsin lakebed. A hydroseral succession of wetland communities occurred at the site, and included a submerged assemblage with Chara , a Carex aquatilis ‐ Eleocharis marsh, a fen, and finally a Sphagnum ‐ Ledum bog. A transition about 9,600 B.P. to a wetter S. balticum ‐ Andromeda carpet is attributed to formation of permaforst and polygonal ice wedges. This community, sometimes with S. compactum and Chamaedaphne , prevailed until about 3,000 B.P. when the polygon became high centered, and peat growth declined. Peat growth rate is determined from 11 14 C dates, and is used to calculate pollen influx. Apparent periodic oscillations every 2,000 years, in total influx, are not accepted as sufficient evidence of treeline fluctuations.