The Science of Fall Colors

As the sun dips below the horizon, casting a warm glow over the mountain slopes, a dazzling array of yellow aspen leaves illuminates the landscape, signaling the arrival of autumn in the San Juan Mountains. The air carries the faint scent of decay, a reminder of the cyclical nature of life as leaves blend into the soil, enriching it with their vibrant hues.

Deciduous trees take center stage during this seasonal spectacle, their leaves undergoing a remarkable transformation known as senescence. As the days grow shorter, chlorophyll production ceases, leading to the breakdown of this green pigment that fuels photosynthesis. With chlorophyll’s dominance waning, other pigments emerge, revealing the true diversity of plant life in the region.

Among the most iconic sights are the fiery yellow-orange hues of aspen leaves, infused with xanthophyll and carotene pigments. At lower elevations, oaks and maples paint the landscape with rich reds, courtesy of anthocyanins present in their foliage. Yet, the fall palette extends beyond these familiar shades, with each species showcasing its unique array of secondary pigments.

From the magentas of fireweed in subalpine meadows to the subtle hues of understory plants, every corner of the forest bursts with color. Against the backdrop of evergreen conifers, the contrast of golden aspens and crimson shrubs creates a vibrant tapestry, highlighting the intricate ecological dynamics at play in forest ecosystems.