LATE QUATERNARY HISTORY OF TUNDRA VEGETATION IN NORTHWESTERN ALASKA

Pollen analysis of a new core from Joe Lake indicates that the late Qu aternary vegetation of northwestern Alaska was characterized by four t undra and two forest-tundra types. These vegetation types were differe ntiated by combining quantitative comparisons of fossil and modern pol len assemblages with traditional, qualitative approaches for inferring past vegetation, such as the use of indicator species. Although impre cisely dated, the core probably spans at least the past 40,000 yr. A g raminoid-Salix tundra dominated during the later and early portions of the glacial record. The middle glacial interval and the transition fr om glacial to interglacial conditions are characterized by a graminoid -Betula-Salix tundra. A Populus forest-Betula shrub tundra existed dur ing the middle potion of this transition, being replaced in the early Holocene by a Betula-Alnus shrub tundra. The modern Picea forest-shrub tundra was established by the middle Holocene. These results suggest that the composition of modem tundra communities in northwestern Alask a developed relatively recently and that throughout much of the late Q uaternary, tundra communities were unlike the predominant types found today in northern North America. Although descriptions of vegetation v ariations within the tundra will always be restricted by the innate ta xonomic limitations of their herb-dominated pollen spectra, the applic ation of multiple interpretive approaches improves the ability to reco nstruct the historical development of this vegetation type. (C) 1994 U niversity of Washington.