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News Article

Chemical fingerprinting of wood can pinpoint its origin

New technique could help tackle illegal logging

As the main cause of deforestation, illegal logging has been notoriously difficult to monitor due to inadequate forest policies, legislation and weak law enforcement.  Endangered species of trees are protected under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which requires that all imported wood is accompanied with documents that record the geographic origin and species of the tree, but these papers can be forged or inaccurate.  Therefore, a quick and accurate method of identifying imported wood is important for law enforcement.  A new chemical forensic technique seeks to tackle the issue by identifying the wood’s origin to a smaller area (<100 km) than ever before.

Wood from a particular species can have distinguishing characteristics, but it can be nearly impossible to tell where it originated, which can be an issue for certain populations, such as those in specific countries or large preserves.  As part of their analysis, the researchers applied the chemical fingerprinting technique to study the molecules in the annual growth rings of Douglas-fir, enabling them to distinguish the wood from two separate populations of this economically important species. 

The technique that was used in the study was called DART-TOFMS (direct analysis in real time-of-flight mass spectrometry) to measure the chemical presence and abundance of Douglas-fir trees from the Oregon Coast and Cascade mountain ranges.  The screening only requires a small sample of wood, which can be prepared for analysis in only 15 seconds.  Through molecular comparison of 188 trees, the researchers were able to tell which region a particular tree came from with 70-76% accuracy.  This is the first time that the DART-TOFMS technique has been used to identify the origin of wood samples over such small distances.

According to the research, almost 950 molecules were detected in the wood’s chemical fingerprint.  Some of the compounds could be identified by comparing their profiles with a database of molecules from other conifer tree species; however, many of these could not be identified.  Most of these “unknown” molecules differed between the wood from the two regions, making it difficult to understand why the changes within the chemical fingerprint occurred. 

“Douglas-fir may be the most important structural timber tree in North America, but we still have much to learn about its wood chemistry,” said Cronn.

The heartwood at the centre of the tree was used for the analysis.  The team analysed the three oldest annual growth rings that were shared between all of the samples, which grew in 1986 to 1988.  No conclusive differences were found between the three years, although it is possible that extreme weather events could have resulted in more dramatic differences between the chemical fingerprints of some annual rings and the team concluded that more extensive sampling would be required.

Cronn and his team are now hoping to discover whether the differences in the chemical fingerprints of the Douglas-fir trees have arisen from genetic differences between the populations, environmental differences, or a combination of the two.   They will compare trees that have identical genetic backgrounds and that have been planted in different environments. Whatever the outcome may be, Cronn believes that the research could offer new opportunities for forest research.

“If wood chemical profiles are primarily determined by the environment, we could use this technique to predict the climate in which a tree was growing.  If chemical profiles are mainly determined by genetics, this kind of analysis could be used as a rapid screen for determining genetic differences.”

Journal Reference

Kristen Finch, Edgard Espinoza, F. Andrew Jones, Richard Cronn. Source Identification of Western Oregon Douglas-Fir Wood Cores Using Mass Spectrometry and Random Forest ClassificationApplications in Plant Sciences, 2017; 5 (5): 1600158 DOI: 10.3732/apps.1600158

Article details

  • Author(s)
  • Stephanie Cole
  • Date
  • 03 August 2017
  • Source
  • Botanical Society of America
  • Subject(s)
  • Dendrochronology
  • Management