Forests: Current Research

Direct Impacts of Climate on Forest Growth, Disturbance and Function



Stakeholders in Pacific Northwest forests are a diverse group, ranging from the timber industry to forest managers on public lands to outdoor enthusiasts. Principal concerns of these groups include potential declines in forest productivity, changing forest species composition, and loss of wilderness values and biodiversity. We are using basic research in climate-vegetation relationships to provide estimates of future changes to forests of the PNW in direct response to changing climate.

Eco-physiological research, using dendrochronology, suggests that Douglas-fir forests in the PNW will become increasingly water-limited as temperatures increase, reducing productivity in montane ecosystems and eventually in low-elevation westside forests. Statistical models of tree species distributions predict changes in forest composition due to warming temperatures, particularly on the east side of the Cascades. We may see substantial shifts to species associated with warmer drier climates. Productivity of high-elevation forests will likely increase, as limiting factors associated with winter temperatures and snowpack decrease in strength.

We are also investigating the linkages between climate (precipitation, temperature, water balance deficit, and soil moisture) and area burned by fire in different ecosystems of the Pacific Northwest. Results to date suggest that land managers, both private and public, will need to develop adaptation strategies to manage changing ecosystems. For example, concepts such as reference conditions and historic ranges of variability will need to be re-evaluated as management tools because the trajectories of forest ecosystems will be away from conditions with which we are familiar.


U.S. Forest Service, College of Forest Resources, University of Washington

Primary Funding

U.S. Forest Service

Selected References

For publications on climate impacts on PNW forest ecosystems, please see CIG Publications.

Littell, J.S., D.L. Peterson, and M. Tjoelker. 2008. Douglas-fir growth-climate relationships along biophysical gradients in mountain protected areas of the northwestern U.S. Ecological Monographs 78(3): 349368.

Littell, J.S., D. McKenzie, D.L. Peterson, and A.L. Westerling. 2009. Climate and wildfire area burned in Western U.S. ecoprovinces, 1916-2003. Ecological Applications 19(4): 10031021.