NEW PERSPECTIVES ON THE LATE PLEISTOCENE TO EARLY HOLOCENE VEGETATION TRANSITION IN THE NORTHERN MOJAVE DESERT

Reconstructed vegetation history in the 1980s based upon ancient woodrat midden data suggested that appearance of characteristic components of modern Mojave Desert vegetation occurred after about 8,000 years ago in the northeastern Mojave Desert near Las Vegas, Nevada, and several thousand years later in the western Mojave Desert of California. Recent examination of pollen samples from a lava tube at the Cima Volcanics suggests that elements of the Mojave Desert Shrub community appeared earlier than previously suggested in the western Mojave. Data retrieved from additional woodrat midden records collected south of the Nevada Test Site west of Las Vegas, Nevada, provide additional evidence of this transition and suggest an appearance of Mojave Desert elements by 9,200 rcyr B.P. and indicate a rapid and broad areal expansion following this. Earlier pollen research at Tule Springs by Mehringer suggested the climatic basis for this change and the Bryson and Bryson MCM model reconstruction of the climate of this region confirm the nature and timing of this early Holocene event. In addition, a dramatic change in geomorphic processes have been previously linked to the climate dynamics, and the resulting dramatic shift in the kind of vegetation and its density during the early Holocene.