In Japan, cherry trees had never blossomed so early since 1409. Global warming has evident consequences on the early flowering of plant species, less well known are the consequences in the yellowing and fall of the leaves of deciduous species (the so-called broad-leaved trees, that is trees that lose their cover between autumn and winter, with the exception of conifers that remain evergreen, among which, however, larches are excluded). Climate change is delaying yellowing and leaf fall in the higher latitudes of the Northern Hemisphere.
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The colors of autumn in Milan: the foliage
A 34-year study
A study found this over a 34-year period, between 1982 and 2015, in forest areas above 50 degrees North latitude. In practice, as regards Europe, the territories above France and central Germany, for Asia everything north of Mongolia and for North America from the US-Canada border up. The analysis was carried out by an international research group led by Chaoyang Wu of the Chinese Academy of Sciences and the results are published in the prestigious journal of the American Academy of Sciences (PNAS).
Delay
The delay in yellowing and leaf fall in deciduous species would be due in particular to the reduction in the speed of the winds. If they blow with less intensity, the soil moisture is preserved longer, thus prolonging the vegetative period of the plants. The phenomenon could have important consequences on the absorption of atmospheric carbon dioxide and on the climate. Chaoyang Wu’s group drew on both direct and satellite observations, and then compared them with weather data for temperature, rainfall, cloud cover and wind speeds. The results showed that the drop in winds is associated with a delay in the senescence of the leaves.
The notice
On January 26, the Wakayama section of the Japanese Meteorological Observatory had announced that between 1953 and 2020 the beginning of autumn, assessed on the basis of the leaves on the trees, moved forward by about 15 days.
April 13, 2021 (change April 13, 2021 | 10:57)
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