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You might have seen pictures of leaves in cold countries turning yellow and red before falling. This usually marks the beginning of autumn. Known as leaf senescence, this process prepares the trees for the coming winter.
As a result of global warming, European trees were found to start this senescence about two weeks earlier. In a study published last month in the journal Science, researchers have now demonstrated that trees have a self-regulating mechanism that limits the photosynthesis period or the productive period. This increased photosynthesis in spring and summer could be leading to earlier senescence.
The analyses suggested that seasonal photosynthesis, autumn temperatures, and day length were the key Lead author Deborah Zani from the Institute of Integrative
Biology, ETH Zurich (Swiss Federal Institute of Technology), Switzerland explained that several other factors, such as atmospheric CO2 concentrations, summer temperatures, light levels, and precipitation also appear to influence senescence, but only indirectly through affecting photosynthesis.
The team arrived at the conclusion by studying six European deciduous tree species over the last six decades. They found a strong effect of photosynthesis on senescence. In years with increased photosynthesis in spring and summer, leaf senescence began earlier, with each 10% increase in photosynthetic activity advancing leaf senescence by eight days.