Populus fremontii  Fremont Cottonwood
DECIDUOUS TREE.  Triangular leaves with rounded teeth and elongate points. Leaves have long petioles (stems) so they move easily in the slightest wind.  Young bark is smooth grayish-green.  An essential component of riparian ecosystems, it shades the ground and water, slows flooding, cools the air, provides food for several insect species, and offers cover and nest sites for birds.  Found in the Empires on Davidson Canyon and its larger tributaries.  Cottonwoods in the Empires are not very large; the one in the photo is typical.
FAMILY:  Salicaceae (Willow Family)