When leaves change colors in the fall, it’s the result of a gorgeous transition of biology, composition, and seasonal timing. The shimmering and brilliance of fall colors may vary dramatically from year to year. Variations depends on a mixture of weather, light, and tree health.
In the spring and summer, leaves are green because they are packed with chlorophyll, the pigment plants use to capture sunlight for photosynthesis. Photosynthesis is the process used by plants to convert light energy into chemical energy. Chlorophyll is consistently being produced and broken down, as long as the days are warm and extended, the green color dominates. Chlorophyll conceals other pigments that are present in the leaf including yellow and orange carotenoids.
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| Deer ignoring the colors. |
When autumn approaches, the daylight hours are shorter and chilly temperatures alert the tree the anticipation of winter. The tree begins to dwindle down its food-making system. As chlorophyll declines, the other pigments in the leaf become prominent. Chlorophyll breaks down first because it requires energy and sunlight to stay active. When chlorophyll fades, the yellow and orange carotenoid pigments that exists in the leaf become distinguishable.
In some trees such as dogwoods and maples, the sugar in leaves become trapped. These sugars react to light and form anthocyanins, which produce brilliant, fire reds, pink, and purple hues. The potency of red colors rely on the temperatures and sunlight. Sunny days and cooler evenings but not freezing produces the radiant reds.
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| Fall at the creek's edge. |
As autumn progresses, a separation layer develops at the base of the leaf stem cutting off water and nutrients. The leaf dries, falls to the ground, and changes to brown due to tannins. The tree loosing its leaves to help conserve energy through the winter. Fall colors really are trees slowly shutting down, unveiling the hidden pigments, and preparing for dormacy. To survive winter, trees enter a dormant state, dropping leaves to conserve water and energy, converting starches to sugars for protection against freezing temperatures, and fortifying their bark for insulation.
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| Red and oranges hues of the aspens in the mountains |
As temperatures decline during morning and evening periods, fish migrate to deeper pools and runs where insect activity decreases. The eggs of mayflies and stoneflies lie dorminate in the egg stage. Winter is coming. See you on the river.
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| Eggs of mayflies and stoneflies lie dormant. |
