In the summer season the foliage is green due to the presence of a particular pigment, chlorophyll. At the end of the summer, in response to environmental signals such as cold and the decrease in the length of the day, the ribs that allow the transport of fluids to and from the leaf are progressively blocked by a layer of phellogenic cells.
It is from this point that the leaf will subsequently detach. The influx of water and mineral salts is therefore rapidly reduced; at the same time, the level of chlorophyll present inside the leaf cells progressively decreases, marking the change in color of the foliage prior to their fall.
Although autumn coloring occurs wherever deciduous trees are found, the most colorful fall foliage is found in the Northern Hemisphere, with regions that include: most of mainland southern Canada; some areas of the north of the United States; Northern Europe and Western Europe north of the Alps; the Russian region of the Caucasus near the Black Sea; and East Asia (including much of northern and eastern China, as well as Korea and Japan.
In the Southern Hemisphere, colorful fall foliage can be seen in: Southern Argentina and Chile; the southern and south-eastern regions of Brazil; Southeast Australia (including Tasmania); and much of New Zealand (particularly the South Island).
As reported on Italian website Greenme.it, Marc Abrams, Penn State University Professor of Forest Ecology and Physiology, said Climate change is lengthening the growing season of trees and altering the fall leaf coloring process.
For nearly four decades, Abrams has studied how seasonal rainfall and temperature affect the timing and intensity of fall colors in central Pennsylvania.
Since 1980, the average temperature of the region has increased by 0.37 ° C, while the rainfall has increased by about 8% (8.6 centimeters more rainfall each year).
This increase in rainfall makes trees grow faster and counterbalances the rise in temperatures. In the west of the country, however, which is getting drier, the effects of climate change on trees are devastating. In general, trees in the eastern regions of the United States are adapting better to climate change thanks to more frequent and abundant rainfall.
In addition to this, the important presence of carbon dioxide in the atmosphere also helps to stimulate photosynthesis in plants: in practice, the greater the amount of CO2 in the environment, the greater the growth of plants thanks to photosynthesis.