HR: 0800h
AN: GC41A-0112    [Abstracts]
TI: A biophysical gradient analysis of climate for understanding conifer establishment in mountain ecosystems of the western U.S.
AU: * Littell, J S
EM: jlittell@u.washington.edu
AF: CSES Climate Impacts Group, Box 354235 University of Washington, Seattle, WA 98195-4235, United States
AU: Graumlich, L J
EM: lisag@cals.arizona.edu
AF: University of Arizona School of Natural Resources, 325 Bioscience East, Tucson, AZ 85721, United States
AB: Establishment of conifer trees at upper treeline is controlled by both physical and ecological phenomena. The physical limitations on tree establishment and growth as well as the ecological and edaphic factors moderating climate vary significantly across western mountain ranges, from the more maritime Cascades through the basin- and-range to the heavily continental central Rockies. In order to understand the factors limiting tree establishment and estimate rates of ecosystem change under future climate change, it is critical to understand the climatic factors limiting tree establishment. We use a multiscale approach to identify climatic patterns associated with upper treeline in nine mountain ranges: the north Cascades, central Cascades, Eagle Cap, Beaverhead, Teton, Beartooth, Wind River, Snowy, and Zirkel mountain ranges. We examined NCDC divisional, SNOTEL, snowcourse, and DAYMET seasonal averages/totals for temperature and precipitation variables to compare the climates at treeline sites identified for conifer establishment research. Divisional data from 1948-2004 indicate a strong geographical gradient in winter precipitation/PDO correlations, but according to SNOTEL data from all mountain ranges, these differences are much weaker in the more recent past. Snow water equivalent at all the sites near the PDO dipole evident in the 1948-2004 correlations appears negatively correlated with PDO. We present DAYMET, SNOTEL, and snowcourse normals for the mountain environments near the treeline sites and relate them to species composition and the nature of recent establishment.
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0476 Plant ecology (1851)
DE: 0736 Snow (1827, 1863)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1630 Impacts of global change (1225)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting