HR: 0800h
AN: PP11A-1426    [Abstracts]
TI: Annual Proxy Records from Tropical Cloud Forest Trees in the Monteverde Cloud Forest, Costa Rica
AU: * Anchukaitis, K J
EM: kanchuka@ltrr.arizona.edu
AF: Laboratory of Tree-Ring Research, The University of Arizona, Tucson, AZ 85721 United States
AU: * Anchukaitis, K J
EM: kanchuka@ltrr.arizona.edu
AF: Department of Geosciences, The University of Arizona, Tucson, AZ 85721 United States
AU: Evans, M N
EM: mevans@ltrr.arizona.edu
AF: Laboratory of Tree-Ring Research, The University of Arizona, Tucson, AZ 85721 United States
AU: Evans, M N
EM: mevans@ltrr.arizona.edu
AF: Department of Geosciences, The University of Arizona, Tucson, AZ 85721 United States
AU: Wheelwright, N T
EM: nwheelwr@bowdoin.edu
AF: Department of Biology, Bowdoin College, Brunswick, ME 04011 United States
AU: Schrag, D P
EM: schrag@eps.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138 United States
AB: The extinction of the Golden Toad (Bufo periglenes) from Costa Rica's Monteverde Cloud Forest prompted research into the causes of ecological change in the montane forests of Costa Rica. Subsequent analysis of meteorological data has suggested that warmer global surface and tropical Pacific sea surface temperatures contribute to an observed decrease in cloud cover at Monteverde. However, while recent studies may have concluded that climate change is already having an effect on cloud forest environments in Costa Rica, without the context provided by long-term climate records, it is difficult to confidently conclude that the observed ecological changes are the result of anthropogenic climate forcing, land clearance in the lowland rainforest, or natural variability in tropical climate. To address this, we develop high-resolution proxy paleoclimate records from trees without annual rings in the Monteverde Cloud Forest in Costa Rica. Calibration of an age model in these trees is a fundamental prerequisite for proxy paleoclimate reconstructions. Our approach exploits the isotopic seasonality in the δ¹⁸O of water sources (fog versus rainfall) used by trees over the course of a single year. Ocotea tenera individuals of known age and measured annual growth increments were sampled in long-term monitored plantation sites in order to test this proposed age model. High-resolution (200μm increments) stable isotope measurements on cellulose reveal distinct, coherent δ¹⁸O cycles of 6 to 10‰. The calculated growth rates derived from the isotope timeseries match those observed from basal growth increment measurements. Spatial fidelity in the age model and climate signal is examined by using multiple cores from multiple trees and multiple sites. These data support our hypothesis that annual isotope cycles in these trees can be used to provide chronological control in the absence of rings. The ability of trees to record interannual climate variability in local hydrometeorology and remote climate forcing is evaluated using the isotope signal from multiple trees, local meteorological observations, and climate field data for the well-observed 1997-1998 warm El Niño-Southern Oscillation (ENSO) event. The successful calibration of our age model is a necessary step toward the development of long, annually-resolved paleoclimate reconstructions from old trees, even without rings, which will be used to evaluate the cause of recent observed climate change at Monteverde and as proxies for tropical climate field reconstructions.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4920 Dendrochronology
DE: 4922 El Nino (4522)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005