This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In non-tropical forests, cold winters hinder tree growth. There, climate warming prolongs the period during which trees absorb carbon through photosynthesis and store it in wood, known as the growing season.
This could potentially mitigate further climate change as wood formation and carbon storage increases. But is this really the case? To find out, an international team including researchers from the Swiss Federal Research Institute WSL analyzed more than 50,000 wood samples from conifer forests across four continents.
Their findings have now been published in the journal Science. "Putting together this unique dataset was a long-standing collaborative effort," says Antoine Cabon, forest ecologist at WSL and the Spanish National Research Council. "Researchers from each partner institute collected wood samples regularly throughout the growing season.
Back in the laboratory, each sample had to be processed, photographed under the microscope and analyzed cell by cell." The researchers monitored xylogenesis—the formation and development of new wood cells, called xylem cells, found in the outermost tree rings. "By looking at the samples under the microscope, we can see exactly when trees are actively forming wood," says Cabon. "This allowed us to observe when this process starts and stops, and at what rate it occurs." Among the sampled sites was the Lötschental.
At different elevations in the valley in the Canton of Wallis, WSL researchers have been collecting wood samples every week of the growing season for the past 20 years. "Such long-term and frequent observations are extremely rare and valuable," says Patrick Fonti, dendrochronologist at WSL, who coordinates the monitoring. "By following the same trees over many years, we can reconstruct how wood formation responds to changing environmental conditions." Overall, researchers found that the rate at which trees produced new xylem cells had a stronger influence on annual cell production than the duration of the growing season.
The rate of wood formation also varied greatly, from one new wood cell per month to as many as two cells per day. Temperature affected the rate and duration of wood formation in different ways. Warmer conditions generally extended the growing season, but the rate of cell production did not continue to increase indefinitely.
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