Counting tree rings: NMR helps in climate calculations

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  • Published: May 1, 2018
  • Author: David Bradley
  • Channels: NMR Knowledge Base
thumbnail image: Counting tree rings: NMR helps in climate calculations

Ring cycle

Using a decade-long sequence of annual growth rings from pine trees, scientists have then incorporated data from nuclear magnetic resonance (NMR) spectroscopy into a study to help them correlate carbon metabolism with climate change. Photo by David Bradley

Using a decade-long sequence of annual growth rings from pine trees, scientists have then incorporated data from nuclear magnetic resonance (NMR) spectroscopy into a study to help them correlate carbon metabolism with climate change.

Children are familiar with the idea that counting the rings of a felled tree will give you an estimate of the age of the tree. Trees not only play a vital role in sustaining life on Earth, but as they grow, they lock within themselves a record of how the environment treated them which can be tapped by various techniques. Now, information from the annual growth rings of pine trees have been examined with NMR spectroscopy by a team from Umeå University’s Chemical Biological Centre. The approach could unlock information about the climate to which the tree was exposed as it grew and help us model with greater precision how climate will change in the future.

Around the world

In earlier work, Jürgen Schleucher and his group demonstrated that vegetation models need to take the entire metabolism of plants, including trees into account in order to build viable climate models of carbon dioxide absorption, photosynthesis and other factors. They used historical plant material from herbariums to study the development of photosynthesis and metabolism in plants over long periods of time. Now, they are examining the ratios of carbon-13 to carbon-12 and offer details in a recent issue of the journal Scientific Reports.

Thomas Wieloch and his colleagues in Umeå, Austria, Switzerland and the USA examined the isotope ratio at all six individual C-H positions in glucose formed by photosynthesis in trees. This contrasts with standard approaches where individual C-H positions were not dissolved. They looked at this ratio in the tree rings of the Black Pine (Pinus nigra) and reproduced the well-known findings regarding carbon dioxide uptake but in addition observed several new signals associated with subsequent metabolic processes. They then examined the same signatures in the tree rings of eleven other tree species from around the world.

Sweet fingerprints

"Our results from eleven trees species show that the carbon-13 to carbon-12 ratios at individual C-H positions leave a fingerprint of the regulation of metabolism, which seems to be similar for all species," Wieloch explains. "We detected several so far unknown carbon-13 signals in the cellulose molecules of our annually resolved tree-ring samples. This, the team suggests, means that besides carbon dioxide uptake, other metabolic processes are influencing the ratio. Most intriguingly, of course, is that many tree-ring series can cover several centuries or even thousands of years and so offer data that stretched back way beyond the start of the industrial revolution.

"We really hope that our discovery that carbon-13 to carbon-12 ratios vary among the individual C-H positions of tree-ring cellulose will yield improved interpretations of isotope signals for the global carbon cycle," Schleucher says.

Related Links

Sci Rep 2018, online: "Intramolecular 13C analysis of tree rings provides multiple plant ecophysiology signals covering decades"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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