Past and Ongoing Shifts in Joshua Tree Distribution Support Future Modeled Range Contraction
Ecological Applications, 21(1), 2011, pp. 137–149 Ó 2011 by the Ecological Society of America Past and ongoing shifts in Joshua tree distribution support future modeled range contraction 1,7 2 3 4 5,8 6 KENNETH L. COLE, KIRSTEN IRONSIDE, JON EISCHEID, GREGG GARFIN, PHILLIP B. DUFFY, AND CHRIS TONEY 1USGS, Colorado Plateau Research Station, P.O. Box 5614, Northern Arizona University, Flagstaff, Arizona 86011 USA 2Merriam-Powell Center for Environmental Research, Northern Arizona University, P.O. Box 4071, Flagstaff, Arizona 86011 USA 3NOAA Earth Systems Research Laboratory, 325 Broadway, Boulder, Colorado 80305 USA 4Institute of the Environment, University of Arizona, Tucson, Arizona 85719 USA 5Lawrence Livermore National Laboratory and University of California, Merced, California 94550 USA 6USDA Forest Service, Rocky Mountain Research Station, Missoula, Montana 59808 USA Abstract. The future distribution of the Joshua tree (Yucca brevifolia) is projected by combining a geostatistical analysis of 20th-century climates over its current range, future modeled climates, and paleoecological data showing its response to a past similar climate change. As climate rapidly warmed ;11 700 years ago, the range of Joshua tree contracted, leaving only the populations near what had been its northernmost limit. Its ability to spread northward into new suitable habitats after this time may have been inhibited by the somewhat earlier extinction of megafaunal dispersers, especially the Shasta ground sloth. We applied a model of climate suitability for Joshua tree, developed from its 20th-century range and climates, to future climates modeled through a set of six individual general circulation models (GCM) and one suite of 22 models for the late 21st century.
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