Holocene environmental history of the Aishihik Region, Yukon, Canada

A 2.7 m sediment core from WA01, a small pond in Southwest Yukon, Canada (unofficial name, 61 degrees 14'41 '' N, 136 degrees 55'35 '' W, 1000 m above sea level), documents the postglacial vegetation and climate history of the Aishihik Basin. Open birch-shrub tundra established at the site ca. 10 900 cal years BP, immediately after deglaciation. Picea glauca established ca. 10 200 cal years BP, and an open spruce forest ecosystem has since remained dominant on the landscape. A gradual increase in Alnus crispa, starting ca. 6600 cal years BP, has also been noted in other studies from Central Yukon, suggesting a significant climate transition in Yukon at this time. An alternating pattern in sediment loss-on-ignition, also beginning ca. 6600 cal years BP, may be broadly related to trends in. partial derivative O-18 values from the Mount Logan and Jellybean Lake oxygen isotope records, and is most likely reflective of periodic changes in available moisture in the region resulting from alterations in the strength and position of the Aleutian Low pressure system. However, millennial-scale climate variability identified in ice core and sediment records had little impact on the forests of the region.