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Criterion 1 Indicator 4
Forest stands have different structures, depending on the ages, diameters, and heights of trees within the forest, the mix of tree species over time, and the overall successional stage of the stand (young, mature, or old-growth forest, for example). Many ecological processes, wildlife species, and other plants besides trees are associated with various forest structures. A diversity of forest structures and successional stages, across the landscape, provides diverse habitats for many different species of plants and animals.
Indicator #3 showed how many acres of various forest types, as defined by the dominant tree species, are in reserved land classifications. This indicator takes a closer look at how many acres are in different size classes, within those total acreages of forest types in reserved areas. This more detailed information is one indication of the potential that these reserved forests have to provide diverse habitats and support biological diversity. This indication, in turn, is one measure of the overall health of Oregon’s forests.

Can This Indicator Be Quantified
GIS was used to combine and analyze three digital data sets: forest type, reserved areas, and size classes for trees. The Oregon Department of Fish and Wildlife (ODFW) provided the digital data set for forest types (see Indicator #1 for more details). The Oregon Forest Industry Council (OFIC) provided the digital data set for tree diameters, or size classes (see Indicator #2). Finally, the digital data set developed for Indicator #3 was used, for information on reserved forest areas. The analysis was done separately for western Oregon and eastern Oregon.
The next two figures show the results of the analysis for western Oregon. In the Douglas-fir forests of northwest Oregon, about half of the larger size classes and about 30 percent of the younger forests are in reserved classifications. In the Douglas-fir and mixed conifer forests of southern Oregon, about half the younger forests and 70 percent of the older stands are reserved. The vast majority of high elevation forests (true fir/mountain hemlock and pine/subalpine fir types) are in reserved areas. Only about 10 to 20 percent of the deciduous or mixed conifer deciduous forests are reserved.
Figure 4-1. Forest types in protected areas, by size class, in western Oregon
Figure 4-2. Percent of size classes, by forest type, in protected areas, in western Oregon
The next two figures show the results of the analysis for eastern Oregon. Most of eastern Oregon’s reserved areas are in the higher elevations of the Cascade Range and the mountains of northeast Oregon. Therefore, for this region, the species in the reserved areas are heavily weighted to those that grow at higher elevations: true fir/mountain hemlock and subalpine fir forest types. Relatively few acres of eastern Oregon’s predominant species, the ponderosa pine and mixed conifer forest types, are in reserved categories. Out of 6.9 million acres of ponderosa pine, only 255,000 acres (4 percent) are in reserved areas. There is a total of 2.8 million acres of northeast mixed conifer forest type, but only 215,000 acres (8 percent) are in reserved areas.   In eastern Oregon, the forests are well-distributed across the entire range of size classes, for all the forest types in reserved areas. All size classes are well-represented.
Figure 4-3. Forest types in protected areas, by size class, in eastern Oregon
Figure 4-4. Percent of size classes, by forest type, in protected areas, in eastern Oregon

  Since the 1980s, several additional areas have been designated as wilderness areas (IUCN Class 1b), or as habitat/species management areas (IUCN Class 4), in Oregon. These areas add to the total number of acres reserved under special designations, as well as adding to the variety of forest types that are under these special classifications. It is likely that the overall age and size of trees is increasing in these reserved areas.

Data Source and Availability
Digital data used to create the IUCN land protection classes was obtained from the following sources.
The data on land management allocations and forest types is readily available from state and federal land management agencies. Data on successional stages is owned and copyrighted by the Oregon Forest Industries Council (OFIC).

Reliability of Data
  Data is generally reliable.

  Data resolution is at a 25-meter pixel size. Only the western part of the state has been completed.

Recommended Action for Data Collection
  Data needs to be collected and interpreted in a similar manner for eastern Oregon.

  See Indicator #3 for definitions of terms used in this indicator.

Selected References
Gland, Switzerland and Cambridge, United Kingdom. 1994. Guidelines for protected area management categories. World Conservation Monitoring Center, IUCN.
Johnson, Norman K., and Sarah Crim, Klaus Barber, Mike Howell, Chris Cadwell. 1993. Sustainable harvest levels and short-term timber sales for options considered in the report of the Forest Ecosystem Management Assessment Team: methods, results, and interpretations. USDA Forest Service Pacific Northwest Region, Portland, OR. 96 pp