Abstract

Two pollen diagrams describe the previously unknown vegetational history of the Black River and Little Black River drain ages of northeastern Alaska. Tundra grew throughout much of the region between ca. 19 800 and 15 000 years BP. Prior to 18 000 years BP, the vegetation was dominated perhaps by xeric Cyperaceae communities, but apparently between ca. 18 000 and 15 000 years BP a more diverse herb tundra characterized the vegetation. Herbaceous species continued to be important in the vegetation until ca. 9700 years BP, although Betula nanaglandulosa and Salix species became more common after 15 000 years BP. At ca. 9700 years BP a major change in the vegetation occurred with the spread of Populus (probably P. balsamifera), B. nanaglandulosa, and Salix, possibly resulting in a mosaic of shrub tundra and Populus gallery forest. Picea glauca migrated into the Black River region ca. 7500 years BP, followed by Alnus ca. 7200 years BP and Picea mariana ca. 6000 years BP.Herb zone records from the Black River region support the hypothesis that eastern Beringian vegetation was characterized by a tundra mosaic prior to 14 000 years BP. Chronological and geographical patterns in the Populus subzone from eastern Beringia suggest that the expansion of Populus populations may not have been exclusively in response to climate change. Dates of Picea arrival on the western Porcupine Plateau indicate that this area probably was not an early Holocene migration route for Picea.

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