Warmer Temperatures Linked To Earlier Spring Leaf Unfolding, New Study Shows

Climate change has led to earlier spring leaf unfolding in many deciduous, or broadleaf, trees that otherwise require colder temperatures for slow release. It turns out this sensitivity has significantly decreased since the 1980s, according to researchers from the Technical Institute of Munich (TUM). This could help scientists better understand future carbon storage and potential frost damage. 

An international team of researchers examined how leaf sensitivity changes when faced with warming temperatures. They observed leaf unfolding of seven dominant European tree species at 1245 sites in Central Europe, according to a news release.

Researchers concluded that for every degree Celsius that spring temperatures increased between 1980 and 1994, leaf unfolding occurred four days earlier. However, between 1999 and 2013, leaf sensitivity decreased and leaves only unfolded 2.3 days earlier per degree Celsius increase. 

"This lower sensitivity of trees to climate change likely reflects the reduced cold during winter that delays dormancy release," Yongshuo H. Fu, first author of the study, said in the release.

Understanding seasonal plant cycles, or phenology, is important for understanding the carbon uptake and water balance of ecosystems. A reduced sensitivity to warming temperatures could reduce the amount of carbon stored in forests.

"The European PEP725 phenological database was a perfect basis to reveal that strong winter warming in the future may result in a slowdown in the advance of spring phenology," Professor Annette Menzel from the department of ecoclimatology at TUM, said in a statement.

Ultimately, trees will benefit from the reduced risk of late spring frost damage, as increasing temperatures are expected in the future.

Their findings were recently published in the journal Nature.

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