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(CNN) – Trees will start to lose their leaves sooner as the planet warms, suggests a new study, which contradicts previous assumptions that rising temperatures are delaying the onset of fall.
Each year, in a process known as senescence, deciduous tree leaves turn yellow, orange, and red as they stunt growth and extract nutrients from the foliage, before falling from the tree before winter. The senescence of the leaves also marks the end of the period during which plants absorb carbon dioxide through photosynthesis.
Global warming has led to longer growing seasons: Spring leaves are emerging on European trees about two weeks earlier, compared to 100 years ago, the researchers said.
“Previous models assumed that because autumns will get warmer and warmer over the next century, fall will be delayed; growing seasons will generally lengthen and fall will be delayed for two to three weeks,” said the ecologist. of the Constantin Zohner ecosystem.
However, Zohner and a team of researchers have said their findings reverse this prediction.
“In fact, we predict that by the end of the century, the leaves could fall even three to six days earlier,” added Zohner, corresponding author of the article published Friday in the journal Science.
Using a combination of field observations, laboratory testing, and modeling, the experts studied data that tracked six species of European deciduous trees (European horse chestnut, silver birch, European beech, European larch, English oak, and rowan) over the past six decades.
The spring and summer productivity increases that occur as a result of elevated levels of carbon dioxide, temperature and light actually cause trees to shed their leaves earlier, the experts found.
Fall temperatures and day length were assumed to be the main environmental factors causing trees to lose their leaves, Zohner said. Now, researchers have identified a third factor: “self-limited” productivity.
“What we see now is that there is a third great mechanism that is working: the productivity (of the tree) is self-limiting. If there is already more in spring and summer, if the plant absorbs more CO2 in synthesis through spring and summer, they lose the leaves earlier, “he said.
“This is a mechanism that we also see in humans: if you start eating earlier, you will be full sooner,” he said.
The findings, Zohner said, have shown that trees have productivity limitations.
“We can’t just put more and more CO2 into the atmosphere and (expect) the trees to do a lot more, there are limits,” he said.
This story was first published on CNN.com, “Trees are losing their leaves sooner due to climate change.”
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