Friday, September 2, 2022

Counting and Measuring Tree Rings


Dendrochronology is the science of dating events such as volcanic eruptions, forest fires, and environmental changes by studying the characteristic patterns of annual growth rings in timber and tree trunks. Tree cell anatomy contributes to a better understanding of past climate events.

Irina Panyushkina pioneered one of the earliest wood anatomy studies in 1998.She spent the late ’90s in Krasnoyarsk at the Russian Academy of Sciences hunched over a microscope, peering down at paper-thin slices of wood from Arctic larch trees.

Panyushkina painstakingly counted and measured thousands of wood cells to create a 350-year climate chronology, dating from 1642 to 1993. It was among the most rigorous tree-ring–based reconstructions of past climate at the time, but it was also prohibitively tedious. To image the cells, each thin section first had to be photographed under a microscope, and then the images were imported into a computer and displayed onscreen. Panyushkina then had to click on every cell to tell the program to measure it.

Panyushkina took 9,460 photographs from 1,896 tree rings, in just 11 tree samples. The work took her four years. “It was so intensive and laborious,” says Panyushkina, who’s now at the Laboratory of Tree-Ring Research at the University of Arizona. “I said I’ll never do it again.

Fortunately, since Panyushkina's research there have been significant advances in dendrochronology and paleoclimate research because of analytical software and computing power. What would have taken weeks in the ’90s now takes days, says Jesper Björklund at the Swiss Federal Research Institute in Birmensdorf. “Using the same amount of time you can obtain roughly 100 times more data, increasing the potential for robustness and scope of each study,” he says. 

The “big jump,” Björklund says, was the development of a software called ROXAS in the early 2000s, which identifies and measures cells from high-resolution scans of tree rings.

Read more here.

Related reading: Tree Story by Valerie Trouet, Johns Hopkins University, 2020

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