Wednesday, August 8, 2007

PS 43-63: Climate influence on shifts in the Deep Canyon ecocline, 1977-2007

Anne E. Kelly, California State University, Los Angeles / University of California, Irvine and Michael Goulden, University of California, Irvine.

Southern California’s pine forests have experienced widespread mortality in the past few years. In Deep Canyon, California, this death seems to be caused by increasing drought and warmer winters. While conifers are the most obviously affected, they are not the only species experiencing collapse. By using elevation gradients as a proxy for temperature and precipitation gradients, one would expect to see species ranges moving upward along a slope in a drying climate. I have compared Zabriskie’s 1977 study of the Deep Canyon ecocline (0m - 2600m elev.) to a modern survey to determine if 1) the mortality rate is unprecedented, 2) species ranges are moving upward, and 3) Landsat and climate data can be used to explain these shifts. Dominant species, including Pinus jeffreyi and Ceanothus greggii, have decreased in coverage by 40-50% over the transect, while increasing slightly at the highest edges of their ranges, indicating that species are indeed climbing towards more favorable climate conditions.

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