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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Bengaluru, Mar 28: Incumbent Mandya MP Sumalatha Ambareesh, who was denied a ticket by the BJP, on Friday said she would reveal her future course of action in the coming days after discussing with her supporters.
The multi-lingual film actress-turned-politician reiterated that BJP should have reserved the seat for itself instead of giving it to its ally Janata Dal (Secular) in the forthcoming Lok Sabha elections.
Speaking to reporters after an hour-long discussion with the BJP state president and Shikaripura MLA B Y Vijayendra, Sumalatha said, "Vijayendra expressed his opinion and expectations. I too told him about my concerns for the district and election. He asked me to join the party as he wanted me to remain with the BJP."
"Tomorrow I my supporters are coming. I told him that I will not take any decision unilaterally without consulting my supporters. It is my duty to listen to their expectations and opinion. I told him that I will make my stand clear in Mandya itself," Sumalatha said.
The Mandya MP had contested the 2019 Lok Sabha election as an independent candidate with the BJP's support defeating former Prime Minister and JD(S) patriarch H D Deve Gowda's grandson Nikhil Kumaraswamy.
She was expecting a BJP ticket to seek re-election from Mandya. However, the BJP forged an alliance with JD(S) last year in September and as per the seat-sharing deal, decided to give Mandya, Kolar and Hassan to its ally.
Now, JD(S) has decided to field former Chief Minister and Deve Gowda's son H D Kumaraswamy from Mandya.
Sumalatha said she wanted BJP to retain Mandya with itself so that it could have given a tough fight in the election and made its presence felt to the people of the region.
"Now there is no point to discuss things which have already happened. I will surely reveal my future course of action in the coming days," the MP said.
Regarding Kumaraswamy's wish to meet her, Sumalatha said she had no objection to meeting him.
Speaking to reporters after meeting Sumalatha, Vijayendra said she had responded to his request. However, she told him that she will reveal her future course of action after discussing with her supporters.
"I am of the firm belief that she will remain with us and strengthen our party. She may feel that this could be her defeat but I told her that everything will set right," the BJP state chief said.