Predicted vs observed modern biomes: The pollen-derived biome map for 0 ka shows patterns which correspond well to observed patterns in vegetation distribution in eastern Beringia. In particular, the map accurately captures the modern position of both the northern and western boundary of the taiga, and the occurrence of cool conifer forests along the coast of south-central Alaska. In south-central Alaska, two sites beyond the observed northern limit of the coastal cool conifer forest are mis-classified. This apparently reflects the presence of low percentages of Tsuga pollen, probably derived by long-distance transport from further south. Sites in regions of eastern Beringia characterised today by a mosaic of tundra and taiga vegetation tend to be preferentially assigned to tundra.
Vegetation patterns in western Beringia are less well captured in the biome maps, but there is a broad-scale agreement. The Chukotkan tundra zone is well delimited. The extent of cold deciduous forest in northeast Siberia is underestimated, reflecting the fact that Larix, the dominant tree species, is systematically under-represented in the pollen spectra. Incorrectly assigned sites from the cold deciduous forest zone were classified as tundra.
6000 yr B.P. biomes: The predicted distribution of biomes across Beringia at 6000 yr B.P. is similar to the distribution based on modern pollen values. There is almost no change in the northern position of the tundra/taiga boundary in Alaska, although taiga is indicated north of its modern limit in the Mackenzie Delta region. There is insufficient data to delimit accurately the western limit of taiga in Alaska. However, the reconstruction of tundra vegetation at a number of sites within the modern taiga zone suggests the forest cover in the western interior was more discontinuous than today's. In the southern coastal region of Alaska, tundra and cold deciduous forest characterise rather than cool conifer forests, which are shown only in far south east of Alaska.
The extent of tundra in Chukotka and coastal Kamchatka at 6000 yr B.P. is similar to today. Reconstructed tundra in the lower Kolyma and northern Yakutia regions is unlikely to indicate a reduction in the extent of cold deciduous forest in western Siberia; it probably reflects the under-representation of Larix in the pollen record, as in the modern case. The biome reconstructions provide no evidence of an expansion of other kinds of forests (e.g. taiga, cool conifer, cold mixed forests) into the region occupied today by cold deciduous forests.
Last glacial maximum biomes: In contrast to the situation at 6000 yr B.P., the predicted distribution of biomes at 18,000 yr B.P. was significantly different from today. The biome map for 18,000 yr B.P. shows tundra across the whole of Beringia. Although steppe is a possible biome, it is not assigned to any site in the analysis.
6000 yr. B.P.
18,000 yr. B.P.
- Biomizations from Edwards and others (submitted).
- Primary Data from the GPD and the PALE Atlas