Gas bubbles inside frozen tree

When the water in tree transport system freezes in winter, gas bubbles are formed inside the ice. These bubbles are harmless as long as the tree is frozen, but when the ice melts again the gas bubbles may expand and block parts of the transport system from water transport.

We froze birch saplings in our laboratory in Viikki, tansported the frozen samples to European Radiation Research Facility in France to take pictures of the gas bubbles in frozen wood in order to better understand what determines the birth

and size of the bubble. The data analyses are ongoing and here you can see a picture where the individual wood elements (vessels and fibers) are separated and identified in a small cross section of birch wood.