Image: Rijksmuseum An international team with Wageningen researchers has demonstrated this. Trees create an archive during their lifetime. The composition and structure of the wood reflect the environment and climate in which the tree grows. The most poignant example is the growth rings that reveal their age and their approximate origin. DNA is the high-tech next level.
Consider, for example, the oak, one of the most popular types of wood used in construction. Not every oak, even if they are of the same species, has the same genetic make-up. With the trees’ geographical spreading, different varieties have developed, typical of the tree’s geographical location. This specific genetic fingerprint can be used to determine a tree’s origin.
To date, live sapwood was used for this method. However, Wageningen PhD candidate Linar Akhmetzyanov and his colleagues have improved the technique to include dead heartwood. ‘This makes it much more useful because it is mainly the heartwood that is used as a construction material’, says forest researcher Paul Copini. But, it is also more challenging, DNA in centuries-old heartwood is often severely damaged..
Heartwood
Over time, DNA breaks down. Moreover, the wood has often been treated, which degrades DNA quality. Heartwood contains substances that impair the multiplication of DNA, which is an essential part of this method. Nonetheless, the researchers managed to develop an optimal procedure for the DNA obtained from chloroplasts (the green leaf cells).
This circular shaped DNA is reasonably well conserved, even when aged.
Paul Copini, Wageningen Environmental Research
‘This circular shaped DNA of approximately 150,000 base pairs, is reasonably well-conserved’, says Copini. The team used six markers (flags) to identify particular pieces of the DNA, the so-called fingerprint. That fingerprint was then compared to a database of 32 fingerprints of oaks from across Europe.
Proof of principle
Copini says the results are promising. Wood from a 700-year old shipwreck from the Baltic Sea near the Mönchgut peninsula was used as proof of principle. Growth rings revealed trees from the late thirteenth century south of Sweden were used. The analysis combined with DNA shows that the wood may very likely have originated from the region around the Polish port of Gdansk.
The study was published in Scientific Reports. This is just the beginning, says Copini. The researchers will see if more information may be extracted from the DNA. In conjunction with isotope research on the wood’s carbon and strontium contents, scientists are now delving deeper and deeper into the wood’s secrets.