By Sara Thompson
Image credit Julian Colton, from Wikimedia Commons,
Special to the Enterprise
The autumnal equinox is on September 22. After this date, the daylight will become slightly less each day until the winter solstice. This gradual change often triggers things in nature to begin to prepare and change for the coming autumn and winter seasons. Deciduous trees go through some of the most iconic changes with their leaves changing into bright colors and falling to blanket the ground. But how else do these trees change to help them to survive the winter months?
Trees are made up of nearly 80% water and is essential for all parts of the tree. When water freezes it expands and this leaves the potential for the trees to be highly damaged, yet most get through winter unharmed. Trees have several tricks they employ to protect themselves from freezing temperatures. The most noticeable is the leaves changing color and falling off. Deciduous trees drop their leaves in order to preserve the water inside the trunk and branches, reducing water loss that is so important to the life of the tree.
Inside the bark the trees continue to transform even their cells to preserve themselves through the winter. The trees are able to change the cell membranes to be more pliable, allowing more water to fill the spaces between the cells. This also helps prevent them from being punctured by ice crystals and instead just pushed and squeezed. Trees also convert the starches inside them to sugars, acting as a natural antifreeze for the living cells within. The cells going through these changes are in the centermost part of the tree and are also have some protection from the outermost parts of the tree, made up of dead cells called xylem.
These processes are gradual and if rapid temperature changes occur, they may not happen quickly enough to prevent damage to the tree. Water freezing too quickly can break the truck when it expands or puncture too many living cells. But when given the proper time, these interior and exterior changes trees go through are what keep them alive through the colder winter months, until they begin to thaw out and start their growth phases again in spring. In the coming months, when you see the leaves begin to change, remember that is only the first step of those trees winterizing themselves, there is so much more happening below the surface.
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