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Caunahue Chile Valdivian rainforest, 40°S, 72°W 500 Markgraf, 1991a west slope of the Andes

Mallín Aguado Argentina Nothofagus dombeyi- 40°S, 71°29'W 840 Markgraf and Bianchi, 1999

Austrocedrus forest, east slope of the Andes

Harberton Argentina Subantarctic mixed 54°53'S, 67°10'W 20 Markgraf, 1991a evergreen-deciduous forest

Caunahue Chile Valdivian rainforest, 40°S, 72°W 500 Markgraf, 1991a west slope of the Andes

Mallín Aguado Argentina Nothofagus dombeyi- 40°S, 71°29'W 840 Markgraf and Bianchi, 1999

Austrocedrus forest, east slope of the Andes

Harberton Argentina Subantarctic mixed 54°53'S, 67°10'W 20 Markgraf, 1991a evergreen-deciduous forest sons after 6800 B.P., when Picea mariana and Alnus expanded at the expense of Picea glauca (Cwynar and Spear, 1995). Therefore, the Holocene trend is toward cooler, wetter summers, with the warmest conditions during the earliest Holocene.

19.2.2. Southeast Alaska

The modern vegetation of southeast Alaska is Pacific coastal forest consisting of Picea sitchensis, Tsuga het-erophylla, and T. mertensiana. Pinus contorta var. contorta occurs in the southern part of the area, especially on muskegs, which are widespread. In the early Holocene, Alnus dominated, as in the Alaskan interior, although it was probably the subspecies A. viridis ssp. sinuata, which is present today, instead of A. viridis ssp. crispa, which occurs in the interior. Pinus contorta migrated very rapidly into the southern part of the area, reaching Lily Lake by at least 12,000 years ago (Fig. 3) (Cwynar, 1990). Picea sitchensis, Tsuga heterophylla, and T. mertensiana migrated up the coast during the Holo-cene. Picea arrived first, but the order of the two Tsuga species varied regionally. T. mertensiana preceded T. het-erophylla at Pleasant Island (Hansen and Engstrom, 1996) at the southern end of the region and at Prince William Sound (Heusser, 1983) at the northern end, but T. heterophylla preceded T. mertensiana by at least 1000 years at Lily Lake (Cwynar, 1990) and Munday Creek (Peteet, 1986). Pleasant Island, Lily Lake, Munday Creek, and Prince William Sound form a southeast-northwest transect along the Pacific coast. Arrival times along this transect were 10,700, 10,700, 8400, and 2800 B.P. for Picea sitchensis; 9800, 7800, 3600, and 2800 B.P. for Tsuga mertensiana; and 9500, 8500, 4200, and 2000

Screaming Yellowlegs Pond Sleet Lake

Screaming Yellowlegs Pond Sleet Lake

FIGURE 2 Representative pollen diagrams from northern Alaska and northwest Canada: Screaming Yel-lowlegs Pond (Edwards et al., 1985) and Sleet Lake (Spear, 1993). Picea glauca is shown as white bars in the Sleet Lake diagram.

Lily Lake

Munday Creek

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