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.
A long-term vegetation history of the Mojave–Colorado desert ecotone at Joshua Tree National Park†
Article first published online: 21 SEP 2009
Copyright © 2009 John Wiley & Sons, Ltd.
Journal of Quaternary Science
Volume 25, Issue 2, pages 222–236, February 2010
How to Cite
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., 25: 222–236. doi: 10.1002/jqs.1313
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.
- Issue published online: 20 JAN 2010
- Article first published online: 21 SEP 2009
- Manuscript Revised: 21 MAY 2009
- Manuscript Accepted: 21 MAY 2009
- Manuscript Received: 8 DEC 2008
- packrat middens;
- Joshua tree;
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.