“Puffs of wind set the cottonwood tree tapping, hard leaf edges batting one another. Stiffer wind brings slaps as the waxy leaves strike with glancing blows. These are the sounds of a fast-growing cottonwood tree. Despite the heat and low air humidity, the slap of the leaves reveals their full hydration.” Cottonwood leaves recorded at Confluence Park, Denver. In background, South Platte River flows over the South Platte river weir and Denver traffic noise:


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