1 Stable isotopes in tree rings

500 year old oak-tree from southern Switzerland Tree rings are an extremely valuable archive of organic material, because they can provide a wealth of information about growing conditions of the past. The reconstruction of the climate is an important aim, helping us to improve our understanding of the natural variations of the climatic system. Stable isotopes have the potential to significantly extend this approach. 2 Preparation Tree rings can be dated by counting the rings and measuring the ring width. Comparison of different trees and with calibration curves allows dating every ring precisely. This is facilitated by the occurrence of "pointer years", very narrow rings due to extreme weather conditions. The tree ring sensitivity varies depending on the climatic and on the site conditions. In the figure above, the uppermost and lowest tree ring series are very complacent, indicating that tree growth was not limited by weather conditions such as temperature or precipitation amount. For isotope analysis, the rings have to be separated with a razor knife