The following information came from federal surveys completed between 1988 and 1997. Although a more recent cycle of inventory measurements was completed for Washington in 2002, those data were not available for reporting. The information will be updated in the 2004 Washington Forest Health Highlights report and other more formal publications that will be produced by the Forest Service.

Washington has approximately 22 million acres of forest land which is dominated by conifer species such as Douglas-fir, western hemlock and ponderosa pine. Red alder, bigleaf maple and cottonwood are the most important broadleaf species. Forests are classified by "forest type" named for the dominant tree on the site.

In addition to the number of acres covered, forests are measured in the volume of wood present. A “cubic foot” of wood is a piece of wood that is one foot tall, one foot wide, and one foot thick. An eight-inch diameter log that is ten feet long contains about 3.5 cubic feet of wood.

The live trees in Washington’s forests total approximately 72,256 million cubic feet of wood. Sixty percent of this wood is in the major western Washington conifers Douglas-fir (29,514 million cubic feet, 40.8%) and western hemlock (13,904 cubic feet, 19.2%). The major eastern Washington conifers such as ponderosa pine, grand fir and western larch contain much less wood, because relatively dry eastern Washington forests have fewer trees, smaller trees and cover less area.

As forest trees continue to grow, some also die. The ratio of mortality (death) to growth provides information on whether forests are increasing or decreasing. If growth is greater than mortality then the ratio is greater than one and the forest volume is increasing. If growth equals mortality then the ratio equals one, and the forest volume is unchanged. If mortality is greater than growth then the ratio is less than one, more trees are dying and the forest live volume is decreasing.

The data in Figure 3 indicate that some forest types are increasing in volume and some are declining. The average ratio of mortality to net growth in Washington, outside national, state, and municipal parks is 2.68, indicating that growth is more than twice as large as mortality. In Douglas-fir, western hemlock, western redcedar and bigleaf maple forests growth is about four times mortality. Lodgepole pine, grand fir and mountain hemlock forests have growth that is about equal to mortality. Mortality exceeds growth in Engelmann spruce and subalpine fir forests.

1. Hiserote, B. and K.L. Waddell. 2003. The PNW – FIA Integrated Database User Guide: Version 1.3. Internal Publication: Forest Inventory and Analysis program, Pacific Northwest Research Station. Portland, Oregon.
2. Prepared by Paul Dunham, Forest Inventory and Analysis program, Pacific Northwest Research Station. Portland, Oregon. Re-formatted by Jeff Moore, Washington Department of Natural Resources. Olympia, Washington.