Text Size:   A+ A- A   •   Text Only
Find     
Site Image
Criterion 1 Indicator 1
Rationale
Forests are ecosystems, and their ecological processes do not follow political or ownership boundaries. The plant and animal species that live in forests generally require a contiguous forest of some minimum size over a large part of their natural range, in order to maintain viable populations. The following discussion provides a general geographic overview of Oregon’s forests, including the total amount of forest land in Oregon and the area covered by different forest types, as defined by the dominant tree species present. However, these tables and the related maps in the map packet do not show information on the vegetative structures, successional stage, stand density, or health of Oregon’s forests.
 

Can This Indicator Be Quantified
The following table shows how many acres of forest there are in Oregon, and how many acres are covered by each of the 11 main forest types. These numbers were calculated using a geographical information system (GIS) to analyze a digital map of land cover provided by the Oregon Department of Fish and Wildlife (ODFW). The original land cover map was classified into 62 different classes, and then aggregated into 23 major categories containing 11 tree species groups (see Map 1-1).
 

 
 
Table 1-1. Total forest acres in Oregon, and acres of forest types
SpeciesArea (acres)Area (as percent of state)Area (as percent of forested area within the state)
Douglas Fir6,985,07411.2824.95
Douglas Fir / Mixed Conifer3,680,0675.9413.14
Ponderosa Pine7,040,04211.3625.14
Spruce; Hemlock402,6510.651.44
True Fir; Mt. Hemlock1,976,3283.197.06
Lodgepole Pine; Jeffery Pine; Subalpine Fir1,024,9511.653.66
Western Mixed1,679,3412.716
Northeast Mixed3,094,618511.05
Deciduous270,1440.440.96
Grass/Shrub/   
Regenerating Forest1,844,9122.986.59
    
All Forested Land31,773,22251.29100
    
Juniper3,775,0946.09 
 
 
About 64 percent of western Oregon’s forests are dominated by Douglas-fir, as shown in the figure below. In the Coast Range and Cascades, Douglas-fir stands tend to have fewer associated tree species than the stands in southern Oregon, where the Douglas-fir is mixed with pine and other species. The western slope of the Coast Range also has large areas covered by spruce-hemlock forests and mixed conifer-hardwood stands. At higher elevations in the Cascades, the forests are mostly true fir-mountain hemlock type, or subalpine fir and lodgepole pine.
 
Figure 1-1. Area of forest types in western Oregon
 
 
 
East of the Cascades, lower elevation forests are largely dominated by ponderosa pine, a forest type that covers 55 percent of eastern Oregon forests, as shown in Figure 1-2. Northeast Oregon’s forests are a mix of conifer species, including pine, larch, Douglas-fir, and true fir (23 percent of eastern Oregon forests). About 4 million acres of land in eastern Oregon are dominated by juniper. It is difficult to separate these lands into forest and range types from satellite imagery, and we did not consider these as forest land for the purposes of this report.
 
Figure 1-2. Area of forest types in eastern Oregon
 

 

Trends
Oregon still has about 91 percent as much forest land now as existed in the 1600s (Oregon Forest Resources Institute, 1997). The 9 percent of forest land lost is due mainly to permanent clearing for agriculture, urbanization, industrial development, railroads, highways, and electric transmission lines. Historically the amount of forest land has always had some fluctuations due to wildfires, both lightning-caused fires and those set by Native Americans.
 

View (.pdf)
Download

Data Source and Availability
 
Data for this indicator came from the Oregon Department of Fish and Wildlife digital land cover map (Gap II).
 
http://www.gis.state.or.us/data/index.html

Reliability of Data
 
The ODFW data is the most reliable data yet developed for classifying Oregon’s different forest types. It was derived from 23 Landsat Thematic Mapper satellite scenes collected from 1991 to 1993. The minimum mapping unit is 100 hectares. In future decades the use of satellite imagery will allow Oregonians to monitor and track trends in forest extent and composition with great accuracy.

Scale
 
The ODFW digital land cover data for Oregon was derived from 25-meter resolution satellite imagery covering the entire state. This data was then classified and aggregated to a minimum mapping unit size of 100 hectares.
 

Recommended Action for Data Collection
 
In order to track trends and detect changes in the future, it is critical to use consistent techniques, classification schemes, and definitions over time. Otherwise, many apparent "changes" could result from using different definitions or classification schemes. Satellite imagery is constantly being updated, but there is no current plan to interpret and classify this data on a regular basis so that there will be a consistent historical record of Oregon’s forests.
 

Definitions
 
Biological diversity -- Also known as "biodiversity." Biological diversity is a measure of the number of different plant and animal species present in an ecosystem. The more different species present and the more diversity there is within a species, the healthier the total ecosystem.
 
Minimum mapping unit -- the smallest area that is mapped on a map. In the case of vegetation mapping, if a stand of one species is smaller than the minimum mapping unit, it will not show up on the map.
 

Selected References
 
Oregon Board of Forestry. 1995. Forestry Program for Oregon. Salem, OR.
 
Oregon Forest Resources Institute. 1997. Oregon Forest Fact Book.