Tim Fitzharris / Coniferous forest in winter, Aspen Vista, Santa Fe National Forest, New Mexico

Tim Fitzharris / Aspen and Spruce trees dusted with snow, Rocky Mountain National Park, Colorado

Tim Fitzharris / Aspens at Independence Pass, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) grove in fall colors, Maroon Bells, Snowmass Wilderness, Colorado

Daniel J. Cox / Quaking Aspen (Populus tremuloides) forest in winter, Aspen, Colorado

Daniel J. Cox / Quaking Aspen (Populus tremuloides) forest in winter, Aspen, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in winter, Aspen Vista, Santa Fe National Forest, New Mexico

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in winter, Aspen Vista, Santa Fe National Forest, New Mexico

Tim Fitzharris / Quaking Aspen (Populus tremuloides) forest in autumn, Snowmass Mountain near Quaking Aspen, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in autumn, Santa Fe National Forest near Santa Fe, New Mexico

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in autumn, Santa Fe National Forest near Santa Fe, New Mexico

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in autumn, Santa Fe National Forest near Santa Fe, New Mexico

Tim Fitzharris / Quaking Aspen (Populus tremuloides) and conifer forest covering Ruby Range, Raggeds Wilderness, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) forest and Mount Sneffels, San Juan Mountains, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) forest and East Beckwith Mountain, West Elk Wilderness, Colorado

Tim Fitzharris / East Beckwith Mountain reflected in pond, West Elk Wilderness, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) forest covering Ruby Range, Raggeds Wilderness, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees and Marcellina Mountain near Crested Butte, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees and East Beckwith Mountain, West Elk Wilderness, Colorado

Yva Momatiuk & John Eastcott / Quaking Aspen (Populus tremuloides) trees with frost-covered branches, Inyo National Forest, California

Yva Momatiuk & John Eastcott / Quaking Aspen (Populus tremuloides) and cumulus clouds above Snake River, Grand Teton National Park, Wyoming

Yva Momatiuk & John Eastcott / Quaking Aspen (Populus tremuloides) in brilliant fall colors, Grand Teton National Park, Wyoming

Yva Momatiuk & John Eastcott / Quaking Aspen (Populus tremuloides) with cumulus clouds, Grand Teton National Park, Wyoming

Yva Momatiuk & John Eastcott / Quaking Aspen (Populus tremuloides) and cumulus clouds above Snake River, Grand Teton National Park, Wyoming

Yva Momatiuk & John Eastcott / Quaking Aspen (Populus tremuloides) and cumulus clouds above Snake River, Grand Teton National Park, Wyoming

Yva Momatiuk & John Eastcott / Quaking Aspen (Populus tremuloides) in brilliant fall colors, Grand Teton National Park, Wyoming

Yva Momatiuk & John Eastcott / Quaking Aspen (Populus tremuloides) and cumulus clouds in autumn, Grand Teton National Park, Wyoming

Sebastian Kennerknecht / Quaking Aspen (Populus tremuloides) forest in autumn, Lundy Canyon, eastern Sierra Nevada, California

Tim Fitzharris / Quaking Aspen (Populus tremuloides) and Spruce (Picea sp) dusted with fresh snow, Rocky Mountain National Park, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees and Fireweed (Chamerion angustifolium), Collegiate Peaks Wilderness Area, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) in fall colors and Maroon Bells, Elk Mountains, Snowmass Wilderness, Colorado

Tim Fitzharris / Haystack Mountain with aspen forest, Maroon Bells-Snowmass Wilderness, Colorado

Tim Fitzharris / Aspen forest overlooking Fremont Lake, Bridger-Teton National Forest, Wyoming

Tim Fitzharris / Aspen forest overlooking Fremont Lake, Bridger-Teton National Forest, Wyoming

Tim Fitzharris / Quaking Aspen (Populus tremuloides) forest, Colorado

Tim Fitzharris / Marcellina Mountain and aspen forest in Raggeds Wilderness, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees covered with snow near Kebbler Pass, Gunnison National Forest, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees covered with snow near Kebbler Pass, Gunnison National Forest, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) forest in spring, Gunnison National Forest, Colorado

Tim Fitzharris / Maroon Bells peaks reflected in Maroon Lake, Snowmass Wilderness, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) forest in autumn and Ranger Peak, Grand Teton National Park, Wyoming

Tim Fitzharris / Quaking Aspen (Populus tremuloides) grove in fall colors, Maroon Bells, Snowmass Wilderness, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) grove in fall colors, Marcellina Mountain, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) grove in fall colors, Washington Gulch, Gunnison National Forest, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) grove in fall colors, Gunnison National Forest, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) forest in autumn colors on Battle Mountain, Colorado

Tim Fitzharris / Fall colors at Gunnison National Forest, Colorado

Tim Fitzharris / Fall colors at Chair Mountain, Colorado

Tim Fitzharris / Maroon Bells and Maroon Creek, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trunks, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in fall, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in fall colors, Lost Lake, Gunnison National Forest, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in fall-colors on Elk Mountains, Capitol Creek trailhead, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in fall colors, Gunnison National Forest, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees with snow, Gunnison National Forest, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in snow, autumn, near Kebbler Pass, Colorado

Tom Vezo / Quaking Aspen (Populus tremuloides) trees, in fall color, Grand Staircase-Escalante National Monument, Utah

Jim Brandenburg / Quaking Aspen (Populus tremuloides) leaves on snow, Minnesota

Daniel J. Cox / Quaking Aspen (Populus tremuloides) forest in winter, Aspen, Colorado

Daniel J. Cox / Quaking Aspen (Populus tremuloides) forest in winter, Aspen, Colorado

Michael Durham / Quaking Aspen (Populus tremuloides) trees in winter, at dusk, Nature Conservancy Zumwalt Prairie Reserve, Oregon