Ecosystem development in the Girdwood area, south-central Alaska, following late Wisconsin glaciation

Pollen analysis of two cores with discontinuous records from a peat bog near Girdwood, in south-central Alaska. provides the basis for reconstructing the first radiocarbon-dated outline of postglacial history of vegetation in the upper Turnagain Arm area of Cook Inlet. Pollen data from clayey silt underlying peat at one site indicate that the earliest known vegetation in the Girdwood area was shrub-herb tundra. Tundra vegetation developed by similar to 13 800 cal years BP. soon after local retreat of glacial ice from the maximum position of the Elmendorf glacial advance (similar to 15 000 - 11 000 cal years BP). By similar to 10 900 cal years BP, the tundra vegetation became shrubbier as Betula nana, Salix, and Ericales increased, and scattered Alnus shrubs began to colonize Turnagain Arm. By similar to 9600 cal years BP. Abuts thickets with Polypodiaceae ferns became the dominant vegetation. By similar to 6600 cal years BP, birch trees (Betula neoalaskana. B. kenaica) from the Anchorage and Kenai lowlands began to spread eastward into eastern Turnagain Arm. Mountain hemlock (Tsuga mertensiana) began to colonize the Girdwood area by similar to 3400 cal years BR followed soon after by Sitka spruce (Picea sitchensis), both Pacific coastal forest species that spread westward from Prince William Sound after a long migration from southeastern Alaska. For at least the past 2700 cal years. Pacific coastal forest composed mostly of Tsuga mertensiana, Picea sitchensis, and Alnus has been the dominant vegetation of eastern Turnagain Arm.