Gold and Red Aspens above Dune Ridges
NPS/Patrick Myers
Today is the first day of autumn! Colors are changing quickly above the dunes, making for spectacular contrasts of fall forests and stark desert dunes.
Why do most aspen trees turn yellow, but some turn orange or red? Part of it is the genetic makeup of each group of trees: aspens are connected by root systems, so that all the aspens in one group are clones of each other. The other variables are soil nutrition, amount of rain, and amount of sunlight. As leaves slow down green chlorophyll production in fall, yellowish carotenoids are exposed in aspen leaves. However, in certain trees, red anthocyanins are also created, especially in very sunny autumns. Anthocyanins act as a sunscreen for the leaves as the chlorophyll disappears.
Whatever the cause, it delights the eyes and senses to see colorful aspen leaves trembling in the autumn sun!
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092217
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