top of page
  • Tom

ITRDB–The savior of my dissertation during pandemic

Updated: Dec 4, 2022

I’m pretty sure like many other researchers in the dendro-community, the pandemic really disrupted our research plan at the beginning. I’m not the exception: I was supposed to core trees in another country and build chronologies in the lab. All in a sudden, the border was closed, and I had no choice to change my dissertation plan on the halfway towards my degree. I was so panic (who’s not), but it took me a while to sink it down, accept the reality and consider plan b, c, d, and e.

At this depressing moment, I saw a tweet from Dr. Kim Novick. She understood the difficulties of grad students facing during the pandemic, so she recommended to explore publicly available dataset as an alternative for dissertation. This got me thinking about the unique dataset contributed by our dendro-community – the International Tree Ring Data Bank (ITRDB), which houses multiple species of over thousand tree individuals across the world. Please allow me to take a moment here to say a big thank you to all ITRDB contributors first!

What is the uniqueness of ITRDB that other publicly available data do not have? It’s tree age, very precise age. We all know how exciting it is when we core a tree, no matter it’s a big or small tree, we are always fascinated when we extract the core and look at how many rings the tree has! Of course, sometimes we may miss the pith or hit a heart-rot, but it is still the most precise way to get the tree age information.

Given canopy-dominant trees were usually sampled for climate reconstruction and uploaded to the ITRDB, such sampling methods reduce the confounding factor of tree canopy position. This is because trees in the upper canopy and the understory face a totally different climate conditions where temperature is usually cooler in the understory with the buffering effect provided by the canopy. The extensive tree-ring sampling efforts also enable us to understand the age distribution of each species so that age-dependent response can be compared for different species with very distinct life history.

Reforestation leads to forests becoming younger. Credit: Tsun Fung Au

But why age matters under global change? Well, big old trees were cut down and younger ones (with natural succession) were planted to remedy what we have done. This changed the forest age structure with more younger trees. These younger trees will be the main component to face future climate extremes like drought and how these young trees respond to drought is critical because this may impact the carbon balance in the ecosystem.

Overall, younger trees tend to be more sensitive to drought with greater growth reduction than older trees. However, when drought ends, younger trees have higher ability to recover from drought than older trees. These differences are greater within hardwood species than coniferous species.

In short-term, drought impacts on the carbon sink could be more adverse, but higher recovery ability of younger trees could be beneficial for the carbon stock in the long run. Conservation on the existing old trees should be prioritized because of their high resistance to drought. Reforestation is still beneficial, but it takes considerable time for young trees to attain maturity and gain drought resistance. Maintaining a diverse forest composition and age structure could help the ecosystem prepare for future climate change. These findings are published in Nature Climate Change with contributions from many other awesome dendrochronologists, climatologist, and ecologists.

Diverse age structure and composition could help forests withstand climate extremes. Credit: Tsun Fung Au

90 views0 comments

Recent Posts

See All
bottom of page