6 – THE LATE QUATERNARY VEGETATION OF THE NORTH YUKON

摘要: The arctic-steppe concept is tested by scrutiny of two detailed late Pleistocene herb-zone pollen records from Hanging Lake (tundra) and Lateral Pond (woodland) in northern Yukon Territory consideration other published sequences eastern Beringia. In particular, we examine the idea that Alaska Yukon, when joined to Siberia Bering land bridge, “constituted end a huge grassland biome, unequaled today size character.” Herb-zone spectra consist largely taxa whose modern affinities are arctic-alpine. Contrary expectations concept, do not show diversity higher than rain. Pollen influx rates as low or lower during Holocene at same sites an order magnitude central Canadian prairies. Influx for Artemisia, well most prominent herbs grasses, about herb zone younger pond sediments, although form much smaller percentages total rain after birch, alder, spruce appear sediments. western Europe interpreted representing open, discontinuous tundra polar desert severely affected frost action. Beringian also probably vegetation floristically physiognomically similar communities found Beringia on xeric, regosolic above montane beyond arctic treeline. represented zones extinct but restricted distribution now due competition species adapted more leached humic soils have immigrated expanded response climatic amelioration. We conclude “arctic steppe biome” never existed Quaternary. large diverse ungulate populations were present interstadials 30,000 years ago–intervals which lack adequate palynological records–rather time zone, 14,000 ago. It doubtful could support population. Termination dwarf brich “rise” ago signals amelioration (warmer wetter). unlikely spread this productive was factor mammalian extinctions.