Vegetation Dynamics During the Last Deglaciation, Southeastern Great Basin, U.S.A.

Publisher Website
Google Scholar
Abstract
Vegetation changes in the southeastern Great Basin between 17,500 and 8000 yr B.P. can be reconstructed from plant macrofossil assemblages in ancient packrat (Neotomaspp.) middens. Vegetation instability after ca. 16,000 yr B.P. involved a dispoportionate number of local immigrations (arrivals) relative to apparent local extinctions (departures). At a site in modern woodland, less than 50% of the arrivals were of transients, species that subsequently went locally extinct; but at a low-elevation desert site almost all arrivals before 10,000 yr B.P. were transient species. Thus, by the close of the last glacial age, higher elevations supported vegetation that resembled present woodland, while lower elevations supported desertscrub that bore little resemblance to modern thermophilous desertscrub.Differences in the pace of plant community “modernization” in different elevational zones can be attributed to migrational lag. Woodland species survived the last glacial age at low elevations nearby, and began arriving at sites within current woodland before 11,700 yr B.P. Warm-desert plants were displaced far to the south, and began arriving after 9500 yr B.P. Moreover, their staggered arrival times suggest that low winter temperatures did not inhibit their migration during the early Holocene. These data suggest that biotic factors, particularly variable dispersal distances and consequent migrational lag, did affect deglacial vegetation change.