Isotope-Dendrochronological Investigation of Tropical Trees from Brazil -Investigation of a New High Resolution Isotopic Paleoclimate Archive

SGER grant

Project Summary

The goal of this short-term exploratory project proposed here is to establish the first terrestrial high-resolution paleoclimate archive spanning the last 200 years based on a tree ring oxygen isotopic record in the tropics. This will be accomplished through the analysis of a very unique tree species in Brazil. The oxygen isotopic data from this study may be used to infer changes in the isotopic composition of soil water that the trees are using, which is directly related to precipitation (and thus potentially linked to atmospheric circulation). This work will be accomplished using a newly developed methodology for the optimized measurement of oxygen isotopes in organic matter. Recent work in Europe has demonstrated that trees in temperate settings can record the isotopic composition of precipitation in their ring cellulose, transferred from rain fall to soil water (which the plants have access to). This proposed project will apply the new approach of using trees as isotope-hydrologic archives. Presently there are no paleo-records of the isotopic composition of precipitation from the rainforest of South America. This approach is both novel and experimental, yet the results would provide the first annual resolution isotopic record of climate change of the last 200 years from Brazil. Isotopic analysis will be measured on individual rings from Auraucaria angustifolia, one of the few tropical tree species which have annual rings. The trees to be studied are located at the State Park of Campos de Jord‹o, in the State of S‹o Paulo (354 km Southwest of Rio De Janeiro). Additionally monthly precipitation samples from the study area will be collected for isotopic analysis and for calibration with the tree record. This approach, if successful, may serve as a link between the tropical ice cores and other terrestrial locations, improving both temporal and spatial correlations of significant climatic events, such as ENSO and/or other periods of extreme change.

Status

Presently, two field campaigns have been complete, and it is anticipated that two more field sessions will be required before all the samplse and data are collected. Additionally, one rain collection station has been installed, and the first rain water sample for stable isotope analysis will be collected at the end of February 2001 (the 1st device placed last summer was destroyed by vandals)

This work is being done jointly with PCU and the Federal University at Rio, with: Dr. Klaus Wagener and Dr. Angela de Luca Rebello Wagener