Geoscience Reference
In-Depth Information
Chapter 6
Stable Isotopes in Dendroclimatology: Moving
Beyond 'Potential'
Mary Gagen, Danny McCarroll, Neil J. Loader, and Iain Robertson
Abstract
When trees grow, they assimilate carbon from atmospheric carbon diox-
ide, 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 bud-
gets. 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 con-
tribution 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 dendrocli-
matology 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 lower-
frequency 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 extract-
ing climate signals from ringless tropical trees. We highlight the need for stable
isotope dendroclimatology to move beyond papers that simply demonstrate 'poten-
tial' 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.
Keywords
Tree rings
·
Stable isotopes
·
Paleoclimate
