Beautiful icy hair – but how does it grow?

It may look like cotton candy. It’s not. A new study goes into the subject of hair ice and how it grows. For almost a century, this stylish way for trees to stand out in the woods has raised countless scientists’ eyebrows.

You may think it’s just a way for trees to be stylish, but actually it is not just that.

First reported in 1918 by Alfred Wegener, a geophysicist and meteorologist, it’s only now beginning to be understood. You may remember Alfred Wegener as the originator of the famous continental drift theory of 1912.

For that theory, which ultimately proved to be at least in the big part true, he had been widely criticized at the time. This is probably why not many paid attention to his statement that this really strange form of ice was not just ice, but had to do with the growing fungi which was found on dying or decaying wood.

To study this strange formation, the researchers had to do quite a bit of hunting. The hair ice develops in very specific conditions. You have to be in the area between 45 and 55 degrees latitude north, in broadleaf forests, and as the formation appears at night, you have to be there at the break of dawn, as it very quickly melts with the sun. Also, it also develops during periods when the temperatures are low, but it is invisible in snow, so they had to pick the perfect non-snowy winter day.

How did they do this experiment? Christian Mätzler of the University of Bern’s Institute of Applied Physics in Switzerland along with Gerhard Wagner of Uppsala University worked together to test the theory Wegener proposed in 1918. They treated the decaying logs with fungicide, and some they dipped in hot water. They saw that those treated with fungicide did not develop hair ice any longer.

This led Mätzler to Diana Hofman and Gisela Preuß, a chemist and a biologist, with whom he worked to find out what specific type of fungus was causing the hair ice, and how it was doing it.

Preuß found that only one type of fungus was needed for the decomposing logs to develop that brilliant white hair: namely, Exidiposis effusa. The unusual shape of the ice is the direct cause of the pores present in the dead trees. The hairs have a diameter of 0.01 mm. The fungus acts like hair gel upon the little formations, making them appear brilliant white and stay fixed in the same shape.

The study is not over, and the scientists say that they will further delve into the fungus to find exactly which component causes the beautiful wigs to grow.

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