Thick forests cover about 95 percent of the watershed.
Douglas-fir is the dominant tree species in the basin below 3,400 feet (1,000 m) above sea level, where western redcedar thrives in moist areas and western hemlock also grows.
Douglas-fir and noble fir are the dominant species at higher elevations, and Pacific silver fir is the climax species.
Mature trees, which cover about 54 percent of the watershed, are mostly more than 500 years old and have diameters exceeding 21 inches (53 cm).
Trees between 9 inches (23 cm) and 21 inches (53 cm) in diameter cover about 34 percent of the basin, while younger, smaller trees dominate the remaining 12 percent.
The forest floors support many smaller plants such as salal and sword fern.
About 5 percent of the watershed consists of unvegetated water bodies or bare rock and a tiny fraction of meadow.

More than 250 wildlife species, including peregrine falcon, bald eagle and northern spotted owl are thought to frequent the watershed.
Migratory birds such as loons use the basin for feeding and nesting as they travel along the Pacific Flyway.
Native fish species include chinook and coho salmon, steelhead, coastal cutthroat trout, Pacific lamprey, and rainbow trout, but since 1922 the headworks dam or its successor, Dam 2, have blocked anadromous fish passage to the upper river and its tributaries.
Many amphibian and reptile species thrive near streams and ponds.
Roosevelt elk, American black bear, coyote, cougar, black-tailed deer, North American river otter, American mink, and North American beaver are among the mammals found in the watershed.
Thick forests cover about 95 percent of the watershed. Douglas-fir is the dominant tree species in the basin below 3,400 feet (1,000 m) above sea level, where western redcedar thrives in moist areas and western hemlock also grows. Douglas-fir and noble fir are the dominant species at higher elevations, and Pacific silver fir is the climax species. Mature trees, which cover about 54 percent of the watershed, are mostly more than 500 years old and have diameters exceeding 21 inches (53 cm). Trees between 9 inches (23 cm) and 21 inches (53 cm) in diameter cover about 34 percent of the basin, while younger, smaller trees dominate the remaining 12 percent. The forest floors support many smaller plants such as salal and sword fern. About 5 percent of the watershed consists of unvegetated water bodies or bare rock and a tiny fraction of meadow.
More than 250 wildlife species, including peregrine falcon, bald eagle and northern spotted owl are thought to frequent the watershed. Migratory birds such as loons use the basin for feeding and nesting as they travel along the Pacific Flyway. Native fish species include chinook and coho salmon, steelhead, coastal cutthroat trout, Pacific lamprey, and rainbow trout, but since 1922 the headworks dam or its successor, Dam 2, have blocked anadromous fish passage to the upper river and its tributaries. Many amphibian and reptile species thrive near streams and ponds. Roosevelt elk, American black bear, coyote, cougar, black-tailed deer, North American river otter, American mink, and North American beaver are among the mammals found in the watershed.
Bull Run River (Oregon)