Late quaternary plant zonation and climate in southeastern Utah
Plant macrofossils from packrat middens in two southeastern Utah caves outline development of modern plant zonation from the late Wisconsin. Allen Canyon Cave (2195 m) and Fishmouth Cave (1585 m) are located along a continuous gradient of outcropping Navajo Sandstone that extends from the Abajo Mountains south to the San Juan River. By holding the site constant, changes in the floral composition for a plot of less than one hectare can be observed, even if sporadically, over tens of millennia. At Allen Canyon Cave, Engelmann spruce-alpine fir forest was replaced by the present vegetation consisting of pinyon-juniper woodland on exposed ridgetops and cliffside stands of Douglas fir, ponderosa pine, and aspen. Xerophytic woodland plants such as pinyon, plains prickly pear, and narrowleaf yucca arrived sometime in the middle Holocene between 7200 and 3400 B.P. At Fishmouth Cave, Utah juniper in Holocene middens replaced blue spruce, limber pine, Douglas fir, and dwarf and Rocky Mountain junipers in late Wisconsin samples. Quantitative climatic estimates are derived for the late Wisconsin by applying vertical gradients for temperature and precipitation to the amount of vegetation depression. The Fishmouth Cave sequence indicates a minimum lowering of 850 m for blue spruce, limber pine, and dwarf juniper. A depression of at least 700 m for Engelmann spruce and alpine fir is suggested for the Allen Canyon locality. Use of conservatively low gradients for stations below 2080 m yields a 3-4 C cooling from present mean annual temperature and 35 to 60% more rainfall than today. Steeper gradients associated with more mountainous terrain suggest a 5 C lowering in temperature and up to 120% increase over modern precipitation. 81 references, 6 figures, 10 tables.
- Research Organization:
- Univ. of Arizona, Tucson
- OSTI ID:
- 5862637
- Journal Information:
- Great Basin Nat.; (United States), Journal Name: Great Basin Nat.; (United States) Vol. 44:1; ISSN GRBNA
- Country of Publication:
- United States
- Language:
- English
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Preliminary assessment of climatic change during late Wisconsin time, southern Great Basin and vicinity, Arizona, California, and Nevada
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Terrestrial-- Basic Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
CLIMATES
COMPARATIVE EVALUATIONS
CONIFERS
CORRELATIONS
ECOSYSTEMS
FEDERAL REGION VIII
FOSSILS
NORTH AMERICA
PALEONTOLOGY
PINES
PLANTS
SPRUCES
TERRESTRIAL ECOSYSTEMS
TREES
USA
UTAH
VARIATIONS