Stable Isotopes in Dendroclimatology: Moving Beyond ‘Potential’

Abstract

When trees grow, they assimilate carbon from atmospheric carbon dioxide, and hydrogen and oxygen from soil water. The stable isotope ratios of these three elements carry signals that can be interpreted in terms of past climate because isotope ratios are climatically controlled by the tree’s water and gas exchange budgets. The traditional tree-ring proxies form the most widespread and arguably the most valuable of the high-resolution climate archives. Here we asses the added contribution that can be made to dendroclimatology using stable isotope measurements. We describe what is involved in measuring tree-ring stable isotopes, provide a brief review of progress to date, and point to the ways in which stable isotope dendroclimatology can be used to provide something new. We conclude that stable isotope ratios sometimes provide stronger climate signals than the traditional proxies, which can be useful where sample replication is limited. Stable isotopes can also be used to access different climate signals in trees, providing a more synoptic view of past climate and may also have the potential to provide a greater proportion of the lowerfrequency climate signal that is difficult to retain during statistical detrending of tree-ring width series. The use of stable isotopes may also pave the way to extracting climate signals from ringless tropical trees. We highlight the need for stable isotope dendroclimatology to move beyond papers that simply demonstrate ‘potential’ and to being to reconstruct the climate of the past. We suggest that this should be done in collaboration, not in competition, with traditional dendroclimatology.