Forests of the Pacific Northwest

Western US Geography

• Rocky Mountains

• Cascades

• Coast Range

• Columbia River Basin

• Sierra Nevada

• Great Basin

Pacific NW Geography

• Cascades

• Coast Range

• Columbia River Basin

• Do you think that the Cascades or Coast Range gets more annual precipitation?

  • similar

Environmental factors predict forest type

• Climate

  • Temperature

  • Precipitation

  • Growing season

• Geology and soil

• Disturbance (or lack of disturbance)

  • natural

  • human

• Time and Space (geography)

What is different about the precipitation on the West Coast?

• Much of the West Coast has a Mediterranean climate

  • seasonality of precipitation (Oct-March)

  • Dry summers

  • Snowpack—significant moisture for higher elevations

  • Moderate temperature: cool drier summers, mild rainy winters

  • Temperate rain forest extends from northern California to coastal British Columbia (Coast Range)

Forest regions, Pacific Northwest

• Coast Range

  • Coast redwood

  • Sitka spruce and western hemlock

• Cascades

  • Douglas-fir and western hemlock

• Within each region, forests vary by elevation as well as latitude

Coast Range

• Extends from British Columbia to northern California

• 80-100+ inches of annual precipitation make this a temperate rainforest

• Drier areas along the coast rely on dense summer fog drip for moisture

• Some of the tallest trees (up to 350 ft) on Earth:

  • coast redwood, but also Sitka spruce, and coast Douglas-fir

Coast Range - Redwood Forests

• Sequoia sempervirens, coast redwood (green)

• 1000-1500 years old

• Fire and insect-resistant, fire favors regeneration

• Extraordinary height enabled by fog drip

• Picea sistchensis is resistant to salt spray

Coast Range - Sitka Spruce and Western Hemlock Forest

• Found mostly in coastal areas in the northern Coast Range into British Columbia and Alaska

• Fog drip is a significant source of water

• Closed canopy forest of sitka spruce and western hemlock

• Grows in mixed stands; lumps together many forest types with other associated species

• Largest specimens of both species found in Olympic National Park

Cascades

• Mt. Rainier—14,400 ft

• Volcanic in origin—Mt St. Helens

• Substantial winter snowfall and snowpack that is an important water source for rivers and communities to the west

• 60-100 inches annual precipitation

• Significant carbon storage

• Significant wildlife habitat

• More public land ownership in the East

Douglas-Fir and Western Hemlock Forest

• Considered the Montane Zone (650-6500 ft)

• Formerly largest wood-producing region in US along with the southeastern United States

• Northern spotted owl habitat

• Key species:

  • Coast Douglas fir, western hemlock, western redcedar

Pacific NW Forests

• Threats

  • Insects and disease

  • Drought

  • Wildfires

  • Climate change

  • Wildland-urban interface

  • Current fire map

  • Beachie Creek Fire, 2020, Cascades