MODERN POLLEN ASSEMBLAGES FROM NORTHERN ALASKA

Surficial sediments from 101 lakes in northern Alaska were analyzed for their pollen content. Isopoll maps of pollen percentages show that boreal forest, mixed forest-tundra, and tundra are characterized by distinctive pollen assemblages. Pollen spectra from boreal forst contain the highest percentages of spruce (Picea) and birch (Betula) pollen, forest-tundra samples have the highest frequencies of alder (Alnus) pollen, and tundra spectra contain the highest grass (Gramineae) and sedge (Cyperaceae) pollen percentages. In addition, vegetational variations within the tundra and boreal forest are evident in the modern pollen. Differentiation of pollen from spruce and birth species accurately indicates areas (in northcentral and northeastern Alaska) where white spruce (P. glauca) and paper birth (B. payrifera) are common. The costal tundra is distinguished from a more interior tundra by higher percentages of grass and heath (Ericales) pollen. The increased resolution of the vegetation-pollen relationships is, in part, a function of a sampling design that employs a broad grid of sample sites instead of using isolated sites or isolated transects. The insight gained from the modern study should help in interpreting fossil pollen records and provide a more detailed picture of the development of the modern boreal forest and tundra in northern Alaska.