A long-term vegetation history of the Mojave–Colorado desert ecotone at Joshua Tree National Park

Authors

  • Camille A. Holmgren,

    Corresponding author
    1. Geography and Planning Department, Buffalo State College, Buffalo, New York, USA
    • Geography and Planning Department, Buffalo State College, 1300 Elmwood Avenue, Buffalo, NY 14222, USA.
    Search for more papers by this author
  • Julio L. Betancourt,

    1. US Geological Survey Research Project Office, Water Resources Division, Tucson, Arizona, USA
    Search for more papers by this author
    • The contributions of J. Betancourt and K. Rylander to this article were prepared as part of their official duties as United States Federal Government employees.

  • Kate A. Rylander

    1. US Geological Survey Research Project Office, Water Resources Division, Tucson, Arizona, USA
    Search for more papers by this author
    • The contributions of J. Betancourt and K. Rylander to this article were prepared as part of their official duties as United States Federal Government employees.


  • Holmgren, C. A., Betancourt, J. L. and Rylander, K. A. 2010. A long-term vegetation history of the Mojave–Colorado Desert ecotone at Joshua Tree National Park. J. Quaternary Sci., Vol. 25 pp. 222–236. ISSN 0267-8179.

Abstract

Thirty-eight dated packrat middens were collected from upper desert (930–1357 m) elevations within Joshua Tree National Park near the ecotone between the Mojave Desert and Colorado Desert, providing a 30 ka record of vegetation change with remarkably even coverage for the last 15 ka. This record indicates that vegetation was relatively stable, which may reflect the lack of invasion by extralocal species during the late glacial and the early establishment and persistence of many desert scrub elements. Many of the species found in the modern vegetation assemblages were present by the early Holocene, as indicated by increasing Sørenson's Similarity Index values. C4 grasses and summer-flowering annuals arrived later at Joshua Tree National Park in the early Holocene, suggesting a delayed onset of warm-season monsoonal precipitation compared to other Sonoran Desert and Chihuahuan Desert localities to the east, where summer rains and C4 grasses persisted through the last glacial–interglacial cycle. This would suggest that contemporary flow of monsoonal moisture into eastern California is secondary to the core processes of the North American Monsoon, which remained intact throughout the late Quaternary. In the Holocene, northward displacement of the jet stream, in both summer and winter, allowed migration of the subtropical ridge as far north as southern Idaho and the advection of monsoonal moisture both westward into eastern California and northward into the southern Great Basin and Colorado Plateau. Copyright © 2009 John Wiley & Sons, Ltd.

Ancillary