The next time you camping in the forest sleeping in your tent, remember, the trees are sleeping as well.
That's the conclusion of a team of scientists from Austria, Finland and Hungary who wanted to know if trees followed day/night cycles similar to those observed in small plants. Using laser scanners pointed at two birch trees, the scientists recorded physical changes indicating a nighttime sleep, with the ends of the birch branches drooping by as much as 4 inches towards the end of the night.
"Our results show that the whole tree droops during night which can be seen as position change in leaves and branches," Eetu Puttonen from the Finnish Geospatial Research Institute said in a statement. "The changes are not too large, only up to 10 cm for trees with a height of about 5 meters, but they were systematic and well within the accuracy of our instruments."
A birch tree at night (left) experiences more branch dropping than during the day (right).
(Photo: Eetu Puttonen/Vienna University of Technology, TU Vienna)
The scientists explained how they scanned two trees, one in Finland and another in Austria. Both trees were scanned independently, on calm nights, and around the solar equinox to ensure a similar length of night. While the tree's branches were shown to droop lowest just before dawn, they returned to their original position in only a few hours.
"It was a very clear effect, and applied to the whole tree," András Zlinszky of the Centre for Ecological Research in Tihany, Hungary, told New Scientist. "No one has observed this effect before at the scale of whole trees, and I was surprised by the extent of the changes."
