
Tree trunks aren't perfectly fixed in diameter.
Sensitive instruments can detect tiny daily changes as water moves through a tree.
During the day, water loss through leaves can exceed water uptake by roots, causing tissues to contract slightly. They can expand again as water is replenished.
The movement is far too small to notice simply by looking at a tree.
A tree that appears completely motionless can actually be changing dimensions throughout the day.
© Swiss Federal Institute for Forest, Snow and Landscape Research