Why Do Trees Change Colors in the Fall?

Tree leaves change color due to water loss during cooler months.

The phenomenal changing of colors that leaves progress through creates numerous opportunities for scientific study each year, according to the USDA Forest Service. Autumn colors are influenced by three major factors: leaf pigments, length of the night and the weather.

Purpose of Leaves

Leaves manufacture nutrients and deliver them to the rest of the tree. They manufacture sugars through the process of photosynthesis, which requires the presence of the green chemical chlorophyll

Tree Hibernation

When the season changes to autumn, the amount of sunlight and water decreases and the amount of darkness increases, ending the process of photosynthesis for the season. The tree responds to this by going into a form of hibernation and shutting down energy production.

Leaf Color

With the change of seasons, the amount of chlorophyll in the leaves fades. Chlorophyll is what causes the green color in leaves. As the amount of chlorophyll drops, so does the green color, and the colors from other pigments, which are always present, starts to surface. With the loss of both sunlight and water, the leaves eventually dry up and fall off the tree.

References

• National Geographic: Why Do Fall Leaves Change Color
• USDA Forest Service: Why Leaves Change Color
• Science Made Simple: Autumn Leaves
• State University of New York: Why Leaves Change Color

Resources

• Wisconsin Department of Natural Resources: Why Do Leaves Change Color