Berlin: A large-scale study of European trees suggests that the leaves of trees between the tropics and the polar regions of the Earth will start to fall in advance by three to six days by the end of the 21st century rather than lengthening by one to three weeks as current models have predicted.
The scientists, including those from the University of Munich (LMU) in Germany, said earlier studies had predicted that the shedding of leaves from these temperate trees will get later under the ongoing climate crisis.
They said early observations also supported this idea since warming caused leaves to stay on the trees later over recent decades, driving increased growing season length that could help to slow the rate of climate change.
However, the current study, published in the journal Science, showed that this trend might be reversed as increasing photosynthetic productivity begins to drive earlier autumn leaf fall or senescence.
According to the researchers, the results build on growing evidence that plant growth is limited by the ability of tree tissues to use and store carbon.
While changes in the growing-season lengths of temperate trees greatly affect global carbon balance, they said future growing-season trajectories remain highly uncertain since the environmental drivers of autumn leaf senescence are poorly understood.
Autumn leaf-shedding at the end of the growing season in temperate regions is an adaptation to stressors, such as freezing temperatures, the scientists explained.
While a common assumption is that alleviating a warmer climate could allow leaves to persist longer and consume more atmospheric carbon, the researchers said the role of photosynthesis in governing the timing of leaf senescence has not been widely tested in trees.
In the current study, the scientists used long-term observations from dominant Central European tree species from 1948 to 2015, and experiments designed to modify carbon uptake by trees, to evaluate related impacts on senescence.
"Accounting for this effect improved the accuracy of senescence predictions by 27 to 42 percent and reversed future predictions from a previously expected 2- to 3-week delay over the rest of the century to an advance of three to six days," the scientists wrote in the study.
The data revealed that increased growing-season productivity in spring and summer due to elevated carbon dioxide, temperature, or light levels can lead to earlier -- not later -- leaf senescence.
This is likely because roots and wood cease to use or store leaf-captured carbon at a point, making leaves costly to keep, the study noted.
The model built by the researchers forecasted the possibility of slight advances, no delays, in autumn leaf-dropping dates over the rest of the century.
According to the scientists, the results "substantially lower our expectations of the extent to which longer growing seasons will increase seasonal carbon uptake in forests".
However, they said the universality of this pattern in other forest types remains unknown.
The researchers believe it is important to implement such growing-season length constraints in other models that do not consider these dynamics.
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New Delhi, May 13: The dialer tune message of the Centre asking people to get vaccinated was criticised by the Delhi High Court which on Thursday said the "irritating" message was being played for "we don't know how long" asking people to get the jab when there was not enough vaccine.
"You have been playing that one irritating message on the phone whenever one makes a call, for we do not know how long, that you (people) should have the vaccination, when you (Centre) don't have enough vaccine.
"You are not vaccinating people, but you still say that vaccination lagavaiye (get vaccinated). Kaun lagayega vaccination (who will get vaccinated), when there is no vaccination. What is the point of the message," a bench of Justices Vipin Sanghi and Rekha Palli said.
"You should give it to everyone. Even if you are going to take money, give it. That is what even children are saying," the bench said and added that the government needs to be "innovative" in such things.
The court said that the government should prepare more such messages instead of preparing just one and running it always.
"Till like a tape it stops running or starts skipping, you will run it for 10 years," it said.
The bench said the government, state or Centre, have to react to the situation on the ground.
"So please have more of them (dialer messages). When a person hears a different one every time, maybe it will help him/her," the court said.
It also suggested using TV anchors or producers to create programmes, on making people aware about use of oxygen concentrators and cylinders or on vaccination, of short durations which can be aired on all channels.
It also said that celebs like Amitabh Bachchan can be asked to chip in and that all this "needs to be done soon".
The court said that a lot of "publicity and propaganda" was there last year on washing of hands regularly and wearing of masks and now there should be similar audio-visual initiatives on use of oxygen, concentrators, medications, etc.
"We are losing time. There should be a sense of urgency," the bench said and directed the Centre and Delhi government to file their reports by May 18 on what steps they are going to take for disseminating information on COVID management via print and TV media and also dialer tunes.