Origin and Disjunction of the Alpine Tundra Flora on San Francisco Mountain, Arizona
1965
Moore, Thomas C.
San Francisco Mountain, an extinct, eroded volcano 12,670 ft in elevation, is situated on the Colorado Plateau in northern Arizona. The summits of the two highest peaks of the mountain support a disjunct flora of approximately 51 known species of alpine tunda vascular plants on 2 square miles of area above the 11,500—ft timberline. The relict alpine tundra flora is definitely related to the tundra of the high peaks of the main Rocky Mountains to the north and northeast. At least 90% of the present alpine tundra vascular flora is believed to have migrated southward to the mountain during Pleistocene time, possibly as recently as 65,000 to 75,000 years ago. As of 10,000 to 24,000 years ago, the alpine tundra vascular flora began to be disjunct from its progenitor flora in the main Rocky Mountains. There seems to be in progress a retrogressive directional change in the tundra flora to even less complex community types than exist at present.
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