Climate variability

Climate variability boosts tropical tree growth during the dry season •

A new study published in the journal nature geoscience found that the growth of tropical trees is driven by climatic variability during dry seasons. By analyzing tree ring data from tropical and subtropical trees – a reliable indicator of tree growth – a team of researchers led by the University of Arizona in the United States and Wageningen University & Research (WUR) in the Netherlands- Bas found that when the dry season is warmer and drier than normal, the growth of tropical trees is greatly reduced, suggesting that climate change may increase the sensitivity of tropical trees to climatic fluctuations.

“These (tropical) tree rings contain a wealth of information about the growth history of trees,” said study lead author Pieter Zuidema, professor of forest ecology and forest management at WUR. . “In this study, we exploit this potential. For the first time, we are getting a pantropical picture of how tropical tree growth responds to climate fluctuations.

Analyzing more than 14,000 tree-ring datasets from 350 locations in 30 tropical and subtropical countries, Professor Zuidema and his colleagues were surprised to find that during the dry season, climate seemed to have a much stronger effect. on tree growth than during the dry season. the rainy season.

“We know that photosynthesis and wood production in tropical trees typically peak during the rainy season,” said study co-author Valerie Trouet, a dendroclimatologist at the University of Arizona.

“So why are year-to-year fluctuations in trunk growth dependent on the dry season? This surprised and intrigued us. Our explanation is that water is available for a longer period of time in years with wetter or cooler dry seasons. Simply put, the growing season is longer. This then leads to greater trunk growth.

These results could help explain the large fluctuations in carbon uptake by tropical vegetation around the world, showing that in warmer or drier years tropical vegetation grows less and therefore absorbs less carbon dioxide from the atmosphere. Finally, the study suggests that slower growth may increase the risk of tree death, which would then become sources of carbon dioxide rather than carbon sinks.

By Andrei Ionescu, Personal editor