A Record of Late Quaternary Vegetation from Davis Lake, Southern Puget Lowland, Washington

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Abstract
Pollen and macrofossil analyses of a core spanning 26,000 yr from Davis Lake reveal late Pleistocene and Holocene vegetational patterns in the Puget Lowland. The core ranges lithologically from a basal inorganic clay to a detritus gyttja to an upper fibrous peat and includes eight tephra units. The late Pleistocene pollen sequence records two intervals of tundra-parkland vegetation. The earlier of these has high percentages ofPicea, Gramineae, andArtemisiapollen and represents the vegetation during the Evans Creek Stade (Fraser Glaciation) (ca. 25,000–17,000 yr B.P.). The later parkland interval is dominated byPicea, Tsuga mertensiana, and Gramineae. It corresponds to the maximum ice advance in the Puget Lowland during the Vashon Stade (Fraser Glaciation) (ca. 14,000 yr B.P.). An increase inPinus ontortapollen between the two tundra-parkland intervals suggests a temporary rise in treeline during an unnamed interstade. After 13,500 yr B.P., a mixed woodland of subalpine and lowland conifers grew at Davis Lake during a period of rapid climatic amelioration. In the early Holocene, the prolonged expansion ofPseudotsugaandAlnuswoodland suggests dry, temperate conditions similar to those of present rainshadow sites in the Puget Lowland. More-mesic forests ofTsuga eterophylla, Thuja plicata, andPseudotsuga, similar to present lowland vegetation, appeared in the late Holocene (ca. 5500 yr B.P.).