Northwest Forest Plan

Interagency Regional
Monitoring Program

10 Year Report for the Northwest Forest Plan

Related Information

Old Growth

This website provides links to the 10-year report summarizing the scientific assessment of the status and trends of late-successional and old-growth forests (also called "older forests") between 1994 and 2003 on federal lands affected by the Northwest Forest Plan.

Periodic assessment of older forests is important for evaluating the effectiveness of the Northwest Forest Plan. Monitoring determines the status and trends of older forests, and evaluates the likelihood of the Plan achieving the planned goals and objectives for maintaining and restoring older forests. The report addresses questions of the nature, "How much older forest is there? Where is it? How much has it changed and from what causes?"

Abstract

We monitored the status and trend of late-successional and old-growth forest (older forest) on 24 million ac of land managed by the Forest Service, Bureau of Land Management, and National Park Service in the Northwest Forest Plan (the Plan) area between 1994 and 2003. We developed baseline maps from satellite imagery of older forest conditions at the start of the Plan. We used remotely sensed change detection to track losses of older forests on federally managed lands to stand replacing harvest and wildfire, and we analyzed the amounts and spatial distribution of older forests by using the mapped data. We also performed statistical analysis on inventory plot information collected on Forest Service and Bureau of Land Management lands. These analyses provided statistically rigorous estimates of older forest acres bracketed by confidence intervals. We analyzed remeasured inventory plots to estimate net change in the amount of older forests on federally managed lands.

We estimated the amount of older forest at the start of the Plan corresponding to three different older forest definitions based on average tree size, canopy layering, canopy closure, and life form. The results ranged from 7.87 million ac (± 1.96 million ac) of federally managed lands with average tree size at least 20 in (medium and large older forest), to 7.04 million ac (± 1.93 million ac) using a definition that recognizes variation in regional forest vegetation (older forest with size indexed to potential natural vegetation zone). We found 2.72 million ac (± 0.35 million ac) were in stands with average tree size 30 in and greater, with multistoried canopies (large, multistoried older forest). At least 1.7 million ac of existing “medium and large” older forest were in fire-adapted vegetation types characterized by high fire frequency and low severity in the Eastern Cascades and Klamath provinces. Up to 1 million additional older forest ac occurred in dry mixed-conifer types in the Western Cascades.

Our data from remeasured inventory plots indicated that the annual net rate of increase of “medium and large” older forest was about 1.9 percent, outpacing losses from all sources. The extrapolated gain in older forest 20 in was between 1.25 million ac and 1.5 million ac in the first decade after the Plan. The gain came primarily from increases in the area of forest at the lower end of the diameter range for older forest. The net increase took into account the older forest removed by stand-replacing harvest, 0.2 percent of the total (about 16,900 ac on all federally managed lands), and the amount burned by stand-replacing wildfire, about 1.3 percent (about 102,500 ac on all federally managed lands). The area mapped as logged or burned had an error estimate of between 7 and 12 percent.

The initial amount, distribution, and arrangement of older forest on federally managed land appears to have met or exceeded Northwest Forest Plan expectations. But the large amount of older forest susceptible to catastrophic wildfire may be a concern for managers. Losses to wildfire in the first decade were in line with assumptions for the Plan area, but rates of loss were highly variable among provinces, with the highest rates of loss occurring in the dry provinces. Loss of older forest to harvest was a fraction of the approximately 230,000 ac of older forest expected to have been harvested. Overall gain was about twice the 600,000 ac expected during the first decade of the Plan.

Older forest maps based on remote sensing allowed for a spatial assessment of landscape patterns, but map accuracy was low in some areas, especially the Eastern Cascades. Remotely sensed change detection was highly accurate for assessing older forest losses to catastrophic disturbance (clearcutting and stand-replacing wildfire). But technological improvements are needed to use remotely sensed data for detecting less severe disturbance from partial harvest or less severe burning. Plot data were not of sufficient resolution to allow for spatial analysis or to identify causes of change. But estimates made from plot data were unbiased, accurate, and precise. Future monitoring work will pursue approaches that tie the plot-based and mapped data sets together more closely.

Keywords: Northwest Forest Plan, effectiveness monitoring, late-successional and old-growth forests, remote sensing, existing vegetation, change detection, Pacific Northwest, Forest Service, Bureau of Land Management, land use allocations, late-successional reserves, physiographic provinces.

Final Report

The Northwest Forest Plan status and trends for late-successional and old-growth forest are available in final format as a general technical report (GTR) identified as PNW_GTR646 by the Pacific Northwest Research Station. The final report for late-successinal and old-growth forest has received extensive technical reviews and external blind peer review. Copies of the reconciliation letter for external peer review comments are included.  These comments have been considered and incorporated into the final report.

Bibliographic Citation

Moeur, M.; Spies, T.; Hemstrom, M., Alegria, J.; Browning, J.; Cissel, J.; Cohen, W.; Demeo, T.; Healey, S.; Warbington, R. [In press]. Status and trends of late-successional and old-growth forests under the Northwest Forest Plan. Gen. Tech. Rep. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station.

Powerpoints

Presenter Powerpoint Presentation Format
Melinda Moeur - US Forest Service Region 6 Status and Trends of Late-successional and Old Forest PDF, 9 MB
Warren Cohen - US Forest Service, PNW Research Mapping Vegetation Across the Northwest Forest Plan Integrating Two Remote Sensing Approaches PDF, 1 MB
Jim Alegria - Bureau of Land Management - Oregon- University of Lausanne, Switzerland Planning and Monitoring Applications from Vegetation Program PDF, 5.2 MB
Miles Hemstrom - US Forest Service, PNW Research The Bumpy Road to Monitoring Late-successional Forests under the NWFP PDF, 833 kb
Thomas Spies - US Forest Service, PNW Research Station Conservation of Old Forests in a Dynamic Landscape PDF, 2.2 MB