The surest sign of winter in my Arizona mountains is the fall change of colors. The summer’s greens are replaced by greys and browns, as ferns die back, sunflowers set seed, and the trees lose their last leaves. The change is remarkably synchronous. It feels like in a single day, summer is replaced by winter….

Quaking aspen is my favorite tree. In the autumn its leaves change color to a warm yellow, making a perfect contrast against its white and black bark. At sunset the forest glows with the light filtering through the stands of this species. I never stop learning new things about it, either. On a recent hike…