As the days grow shorter and temperatures drop, the Upper Peninsula's forests shift from green to a tapestry of reds, oranges, yellows, and golds. From shimmering aspens and golden birches to the fiery maples, each species tells a unique story of the changing season.
The secret to Nature's transformation lies deep within the leaves and their relationship with sunlight. This transformation is not only visually stunning but is also a fascinating example of plant biology at work.
Throughout summer, leaves are filled with chlorophyll, a green pigment essential to photosynthesis. Simply put, chlorophyll absorbs sunlight which plants can convert into energy. As a green pigment, chlorophyll is best at absorbing red and blue light. However, as days grow shorter and there is less sunlight available, trees slow down their chlorophyll production. As the chlorophyll pigment fades, other pigments become visible, and new pigments are produced.
Behind chlorophyll, carotenoids are the next most common pigments in plant leaves. These pigments are present in leaves all summer but only become visible when the green chlorophyll fades as light periods decrease. Carotenoids aid in photosynthesis by capturing additional light energy, mainly blue and green light, and protecting chlorophyll from damage caused by excessive light. Carotenoid pigments are the unsung heroes of fall as they give leaves their yellow, orange, and some red color.
Our next culprits are anthocyanins. These pigments are produced in the fall when sugars get trapped in the leaves. Anthocyanins are most common in plants with high sugar content, such as red maples and red oaks. They are known for their dark red and purple hues, which are most visible towards the end of fall.
Lastly (and perhaps least based on appearance) are tannins. Tannins are always present but become more noticeable once previous pigments fade due to lack of sunlight. Tannins mainly serve as a defense mechanism in plants used to protect the plant. These pigments are less effective at absorbing sunlight and signal the end of the leaf's lifecycle. Tannins are responsible for the brown color seen in some leaves, like oaks. Tannins are also found in plants' bark, roots, and stems.
At UPLC, we look forward to celebrating this seasonal transformation across our protected lands year after year. We encourage you to take a step outside, explore the trails, and join us in experiencing this natural wonder firsthand. This October we have multiple events to welcome you to a nearby nature preserve. Register for for a hike today at uplandconservancy.org/events!
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