Every year, in a process known as aging, the leaves of deciduous trees turn yellow, orange and red because they stop growth and extract nutrients from the tree leaves, before they fall from the tree before winter. Leaf aging also marks the end of the period during which plants absorb carbon dioxide through photosynthesis.
Researchers said global warming has led to longer growing seasons – spring leaves appear in European trees about two weeks ago, compared to where they were 100 years ago.
“Previous models assumed that since autumn will become warmer and warmer over the next century, autumn will be delayed – the growing seasons will generally be longer, and autumn will be delayed by two to three weeks,” said Konstantin Zonner, an ecologist in the ecosystem.
However, Zohner and A team of researchers said their results reflected this expectation.
Using a combination of field observations, laboratory tests, and modeling, the experts studied data that tracked six types of European deciduous trees – European horse chestnut, silver birch, European beech, European pine, English oak and rowan – over the past six decades.
Experts found that increases in spring and summer productivity that come as a result of higher carbon dioxide, temperature and light levels, are causing trees to lose their leaves early.
Zonner said that low temperatures and length of day were the main environmental factors that caused the trees to lose their leaves. Now, researchers have identified a third factor – “self-restricted” productivity.
“What we’re seeing now is that there is a third huge mechanism going on – productivity (the tree) is restricting itself. If you have more that actually happens in spring and summer – if the plant absorbs more carbon dioxide in synthesis through in the spring and summer they lose their leaves early.” .
“This is a mechanism that we also see in humans – if you start eating early, you’ll be satiated early,” he said.
Zoner said the results showed that trees have limitations in productivity.
“We can’t put more and more carbon dioxide into the atmosphere and (we expect) trees to do much more than that – there are limits,” he said.