Quaking aspens in Kaibab National Forest, Arizona.
PHOTO: RIC ERGENBRIGHT
A moose calf strips away outer bark to feed on nutritious inner bark.
SHIN YOSHINO/MINDEN PICTURES
Detail of ponderosa pine bark.
Strips of bark peel away from a white birch.
Detail of sycamore bark.
J. PAUL MOORE
A gray tree frog blends in with bark.
Detail of red pine bark.
JIM BRANDENBURG/MINDEN PICTURES
Patterns in cottonwood bark.
BRYAN E. REYNOLDS
A seedling oak tree (foreground) grows in front of a mature oak tree.