Fall is here and the leaves are turning colors. The white ash first showed signs, now I see some maples in my area turning yellow to red. On a trip back from Warrensburg last weekend, I noticed more colors on the colder side of the mountains than in our valley area. It won’t be long before we have the full spectrum of fall colors. What a great way to start the morning, a visual delight looking out our morning coffee windows.
As the day length grows shorter it signals the deciduous trees and bushes that winter is on the way. The season for rest is beginning. The plants start to undergo a dormancy preparation process. Many nutrients in the leaf move back into the stem of the tree to be stored, while some will stay within the leaf.
As all of this is happening, we get to see the colorful psychedelic leaf show, which would even make a Haight-Asbury hippy happy!
The fall colors of the leaves happen when the production of chlorophyll comes to a halt. An abscission layer forms at the leaf base, stopping the flow into and out of the leaf. As the leafy green color of the leaf fades away, other colors become visible. The colors come from compounds in the leaf left behind. Yellow is from the xanthophyll’s, and the orange coloring comes from carotenoids which make the popple and hickories glow on a cool fall day.
The red and purple pigments develop when the sugars in the leaves can no longer get transported out of the leaf to the stem. The sugar in the leaves breaks down to form anthocyanin’s, which give the maples the fire truck red colors.
As these compounds begin to break down and fade, the final coloring is the browns and tans left behind. An oak woods, stands out on a hill side due to the brown colors and the late leaf drop, a good way to detect where the acorns will be. Using the tree colors of the fall leaves is a great way to find various habitats and forest stands.
Once the color fades a physiological process called abscission causes the leaf stalk to separate from the stem and the leaf is free to drop to earth or get blown away with the winds.
The leaves return to earth and add to the organic matter of the forest, recycling nutrients. Some leaves become food for critters. Deer will eat the leaves of maple to get the sugar energy left in the leaf. Cows will eat maple and ash leaves when blown into a pasture. It’s a fall treat and a source of diverse nutrients and minerals. When a maple leaf falls into a stream, it will flow downstream until it collects behind a rock or other object that traps it. When a clump of them get trapped, they form what is called a leaf pack. These maple leaf packs are vital food for the stream bugs, which in turn become food for fish. It’s all about food, energy and the recycling of nutrients.
The leaves feed the soil, and the soil feeds us.
Next spring, growth will start once again and nutrients will be carried back up through the stems to the newly forming leaves. The seasonal cycle of life starts once again.
So get outside, take a hike and experience the psychedelic leaf show, we only have so many seasons in life, so enjoy them!
Rich Redman is a retired District Conservationist for the USDA Natural Resources Conservation Service and an avid outdoorsman. His column will appear regularly. He may be reached at firstname.lastname@example.org.