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Trees in dry areas will not benefit from warming climate

Trees sprout and grow earlier in a warming climate, but how this change affects overall tree growth is still unclear. A study conducted by Professor Eryuan Liang suggests that trees may benefit from an earlier growing season in cold and humid locations. Those in areas with dryer climates, however, will not necessarily benefit from the earlier springs associated with a warming climate. 

To conduct the study, Professor Liang and his team at the Institute of Tibetan Plateau Research (ITP) at the Chinese Academy of Sciences looked at growth rings from trees worldwide and compared them based on latitude. In particular, they were looking at the width of the growth rings.

The study was focused on tree ring width because wood formation is a catalyst for xylem maturation and determines how long the xylem will grow. Slower growth of the xylem leads to wider growth rings, which represent larger trees and more carbon storage. 

The researchers investigated when tree ring growth began and how that affected the final width of the ring. When they compared different latitudes, they found that trees located in areas above 60 degrees North benefited from an early spring. These areas include central Europe and the eastern and western coasts of North America.

However, trees on the Colorado and Tibetan plateaus, which are cold and dry, suffered from an early spring. This is likely because a longer growing season is associated with a greater likelihood of drought and spring frost.

“From these observations, we conclude that trees will grow faster under advanced springs, unless they are thirsty,” said Professor Liang.

The researchers also looked at boreal forests in northern Asia and Europe. They found that increased growth due to an earlier growing season may result in the alleviation of cold stress caused by warmer conditions. 

In Central Europe and across portions of the U.S. coastline, advanced spring improved growth, but not for the same reason. The experts found that tree growth was enhanced in these locations due to a longer growing season. 

The research shows that a warming climate may be beneficial for tree growth in some areas of the world but detrimental for others – particularly for those areas that are cooler and dryer, and where trees may already have more environmental pressure. 

“These emergent patterns of how climatic impacts on wood phenology affect tree growth at regional to hemispheric scales hint at how future phenological changes may affect the carbon sequestration capacity of extratropical forest ecosystems,” wrote the study authors. 

The research is published in the journal Nature Ecology & Evolution.

By Erin Moody , Staff Writer

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