2000. Biomes of western North America at 18,000, 6000 and 0 14 C yr BP reconstructed from pollen and packrat midden data

• Main Authors: Robert S. Thompson, Katherine H. Anderson
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Pacific; taiga
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.459.4714; http://www.bridge.bris.ac.uk/projects/BIOME_6000/SpecialIssue2/BIOME2_downloads/thompson.pdf

1 A new compilation of pollen and packrat midden data from western North America provides a refined reconstruction of the composition and distribution of biomes in western North America for today and for 6000 and 18,000 radiocarbon years before present (14C yr B.P.). 2 Modern biomes in western North America are adequately portrayed by pollen assemblages from lakes and bogs. Forest biomes in western North America share many taxa in their pollen spectra and it can be difficult to discriminate among these biomes. Plant macrofossils from packrat middens provide reliable identification of modern biomes from arid and semiarid regions, and this may also be true in similar environments in other parts of the world. However, a weighting factor for trees and shrubs must be used to reliably reconstruct modern biomes from plant macrofossils. 3 A new biome, open conifer woodland, which includes eurythermic conifers and steppe plants, was defined to categorize much of the current and past vegetation of the semiarid interior of western North America. 4 At 6000 14C yr B.P., the forest biomes of the coastal Pacific Northwest and the desert biomes of the Southwest were in near-modern positions. Biomes in the interior Pacific Northwest differed from those of today in that taiga prevailed in modern cool/cold mixed forests. Steppe was present in areas occupied today