Changing weather affects timing of autumn colours

The autumn colors in Finland this year surprised visitors as the whole country went red and yellow at the same time, instead of a gradual change from north to south.

Usually the colors change first in Finland's northernmost Lapland in September and the wave spreads south over several weeks.

Risto Jalkanen, a special researcher at the Natural Resources Institute Finland (Luke), told Xinhua that the dry weather in recent years had caused the change.

"The lack of sunlight triggers on the process where the deciduous plants transfer nutrients from its leaves," Jalkanen said, adding "But there was not much rain last year and again this year, the summer was dry and ground water was deep, and so the process became earlier."

Of the two colorful attractions in Finland, the Northern Lights have always been subject to geomagnetic conditions and "space weather", while the autumn color blaze has worked like a clock. The fact that autumn colors first appear in Lapland has developed over the decades. Lapland was the place to see the autumn colors while the temperature was still in the summer range.

Jalkanen said a local civic weather observer had told him in Rovaniemi that "the autumn colors turn on at 8 a.m. on Sept. 10", any year. The plants in Lapland are used to a shorter growing season than those in the south of the country.

Jalkanen noted, however, that there have been fluctuations over the decades and he cannot predict a permanent change.

Exceptions to the rule are plants and trees imported to Finland, as they turn red and yellow later. Jalkanen believes an adaption may take a thousand years.

Jalkanen said that the larches are the last trees to close the 2019 color season in Lapland, since "the species is not originally Northern European."