After the summer of fire we had in Oregon and the West, there has been a lot of discussion about the causes of all those fires. Some argue climate change, while others blame a lack of forest management. The truth is that both factors are to blame.
A recent study from Oregon State University and a new publication from the U.S. Forest Service Pacific Northwest Research Station highlight the need for more active management on National Forests, as a changing climate contributes to more severe fire seasons.
In the study, Matthew Reilly, a recent Ph.D. graduate from the OSU College of Forestry, led a team of researchers who analyzed patterns of landscape change in the eastern Cascades of Washington, Oregon and northern California. The team examined low-, medium- and high-intensity fires in ponderosa pine, mixed conifer and subalpine forests from 1985 to 2010.
The study found that about 30 percent of subalpine forests and 10 percent of mixed conifer and ponderosa pine forests burned during the 25-year study period. About a third of the area burned with high severity. The study also found that forest restoration work to make forests more fire-resilient has fallen far short of the level needed to make a difference on a landscape scale.
The study covered all forestlands. But in eastern Oregon, nearly 70 percent of the forestland is managed by the federal government, predominantly by the U.S. Forest Service, so the results seem to be most applicable to National Forests.
The Reilly team’s study has been published online by the academic journal Ecological Applications, and you can read a full report of the findings here. A news release from OSU about the study is also available here.
Like the OSU study, a new report demonstrates the need for more active management on National Forests in Oregon. Oregon’s Forest Resources, 2001-2010: Ten-Year Forest Inventory and Analysis Report is now available online through the Forest Service TreeSearch webpage. This publication is an overview of the status of Oregon’s forests based on the latest data from the PNW Research Station’s Forest Inventory and Analysis (FIA) program, and includes an extensive set of 51 summary data tables. Additional inventory information and another 89 summary tables are included in the online supplement.
This report has tons of great information and will be the subject of future blogs. However, I want to call attention to its discussion of the current rates of tree growth, removals and mortality on National Forest System lands.
The table below is a summary of average annual volume and percentage of growth, mortality and removals on National Forest timberland in Oregon. Timberland is the portion of the forest that is productive enough to manage for timber production and is not reserved for wilderness areas, parks or other non-timber uses.
The data shown in this table is for eastern Oregon, western Oregon and all of Oregon. What jumps out at me from this data is the relationship between mortality and removals. Overall, National Forest timberlands had 56 percent mortality of their growth and only 9 percent removals, which includes harvests and non-commercial cutting. This mortality figure contrasts sharply with state and private forests, which had 19 percent and 12 percent mortality, respectively.
Mortality can be from fire, disease, insects or blowdown. The FIA inventory doesn’t break it down by causes, but historically disease and insects account for the largest volume of tree mortality in Oregon.
The high rate of mortality on National Forest timberlands is in direct contrast with the low rate of removals, including timber harvest. A very different relationship is evident on non-National Forest timberlands.
Non-National Forest timberlands (state and private) have combined mortality rates of 13 percent and combined removal rates of 92 percent. Clearly, timberlands that are more actively managed, as indicated by removal rates, are healthier, as indicated by mortality rates. These forests have fewer dry, dead trees, also known as “zombie trees,” that can fuel the spread of a wildfire. This makes them much less vulnerable to catastrophic fires.
In the end, the best way forward to reduce catastrophic fires is the same way to reduce tree mortality on National Forest timberlands: increased active management. That’s because it not only helps reduce mortality, it also increases a forest’s fire resiliency.
For the forest,
Director of Forestry