Most of the land supports an evergreen forest that includes pure or mixed stands of ponderosa pine, Douglas-fir, Engelmann spruce, lodgepole pine and subalpine fir. Brush-grass or grass are found in the non-timbered areas. There are many different animal species and places for animals to live. The Forest contains large areas of summer range for big game species, such as mule deer and Rocky Mountain elk. Trout are native to most streams and lakes, while oceangoing salmon and steelhead inhabit the many tributaries of the Salmon River.Most of the land lies within the Idaho Batholith, a large and highly erodable geologic formation. Through uplift, faulting, and subsequent dissection by streamcutting action, a mountainous landscape has developed. Elevations range from 2,600 to 9,800 feet. The major river systems represented are the Boise and Payette Rivers and the South and Middle Fork drainages of the Salmon River. The average precipitation ranges from 15 inches at lower elevations to 70 inches at higher elevations.