HR: 0800h
AN: GC31A-0105    [Abstracts]
TI: Climate Variability and Ponderosa Pine Colonizations in Central Wyoming: Integrating Dendroecology and Dendroclimatology
AU: * Lesser, M
EM: mlesser@uwyo.edu
AF: Program in Ecology, Department of Botany University of Wyoming, 1000 E. University Ave, Laramie, Wy 82071, United States
AU: Wentzel, C
EM: cwentzel@uwyo.edu
AF: Department of Botany University of Wyoming, 1000 E. University Ave., Laramie, Wy 82071, United States
AU: Gray, S
EM: sgray8@uwyo.edu
AF: Department of Civil and Architectural Engineering University of Wyoming, 1000 E. University Ave., Laramie, Wy 82071, United States
AU: Jackson, S
EM: Jackson@uwyo.edu
AF: Program in Ecology, Department of Botany University of Wyoming, 1000 E. University Ave, Laramie, Wy 82071, United States
AB: Many tree species are predicted to expand into new territory over the coming decades in response to changing climate. By studying tree expansions over the last several centuries we can begin to understand the mechanisms underlying these changes and anticipate their consequences for forest management. Woody-plant demographics and decadal to multidecadal climate variability are often closely linked in semi-arid regions. Integrated tree-ring analysis, combining dendroecology and dendroclimatology to document, respectively, the demographic history of the population and the climatic history of the region, can reveal ecological dynamics in response to climate variability. We studied four small, disjunct populations of Pinus ponderosa in the Bighorn Basin of north-central Wyoming. These populations are located 30 to 100 kilometers from the nearest core populations of ponderosa pine in the western Bighorn Mountains. Packrat midden studies have shown that ponderosa pine colonized the western slopes of the Bighorn Range 1500 years ago, so the disjunct populations in the basin must be younger. All trees (living and dead) at each of the four disjunct populations were mapped, cored, and then aged using tree-ring based techniques. We obtained records of hydroclimatic variability from the Bighorn Basin using four tree-ring series from Pinus flexilis (3 sites) and Pseudotsuga menziesii (1 site). The four disjunct populations were all established within the past 500 years. Initially, the populations grew slowly with low recruitment rates until the early 19th century, when they experienced one or more large recruitment pulses. These pulses coincided with extended wet periods in the climate reconstruction. However, similar wet periods before the 19th Century were not accompanied by recruitment pulses, indicating that other factors (e.g., population density, genetic variability) are also important in colonization and expansion. We are currently obtaining genetic data and carrying out population modeling to differentiate the effects of population dynamics, genetic variability, and climate variability on recruitment and expansion of these populations.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1632 Land cover change
DE: 1637 Regional climate change
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting