By Isaac Walker

In three days, it will officially be fall! When the air starts to cool, nature takes its cue and begins preparing for the dormant season. This sparks many of the changes that have become icons of the season. Let’s dive into some of the details of how and why a few of these changes occur.

Leaf color: Every fall the trees turn the landscape into a fiery blaze with leaves of yellow, orange, red, and brown. We know this is because the leaves are dying, but why do they change color before they even begin to decompose? The answer lies in hidden pigments that are not visible until the fall. Most of the year, leaves are packed with chlorophyll, a green pigment that is involved in capturing light for photosynthesis, but when the trees begin to go dormant, their leaves begin to lose most of their chlorophyll revealing the vibrant warm pigments had been masked by the overwhelming greens. Anthocyanins are the red and purple pigments and are the same pigments as are found in beets and cherries. Carotenoids are yellow and orange, the same as pumpkins and carrots.

The Autumn Aroma: That crisp, distinctly fall smell that is so nostalgic and pleasing actually comes from the decaying of leaves and other plant material. The cool air traps “fall spice” scented compounds that are released when leaves break down. In warmer air, the compounds would disperse too quickly to be much noticed, but the cooler air holds those smell-good molecules close enough to the ground for us to get a whiff of them.