Old-growth coniferous forests of the Pacific Northwest are among the most productive temperate ecosystems and have the capacity to store large amounts of carbon for multiple centuries. To date, there are considerable gaps in modeling ecosystem fluxes and their responses to physiological constraints in these old-growth forests. These model shortcomings limit our ability to understand and project how the old-growth forests of the Pacific Northwest will respond to global climate change. This study applies the cohort-based Ecosystem Demography Model 2 (ED2) to the Wind River Experimental Forest (Washington, USA), a well-studied old-growth Douglas-fir–western hemlock ecosystem. ED2 is calibrated and validated using an extensive suite of forest inventory, eddy covariance, and biophysical observations. ED2 is able to reproduce observed forest composition and canopy structure, and carbon, water, and energy fluxes at the site. In the simulations, the effect of limited water supply on ecosystem carbon fluxes is mediated primarily by the forest’s gross primary productivity (GPP) response, rather than its heterotrophic respiration response. The simulation indicates that stomatal conductance is mainly determined by soil moisture during periods of low vapor pressure deficit (VPD). However, when VPD is high, stomatal conductance is greatly reduced regardless of soil moisture status. During summer droughts, reduced soil moisture and increased VPD result in considerable stomatal closure and GPP reduction, which in turn decreases net carbon uptake. Cohort-based scheme integrates all canopy layers (species) that have distinct sensitivity to microclimate and respond distinctly to drought. This study is an initial first step to explore the potential importance of cohort-based model in simulating forest with complex structure, and to lay the foundation for applying cohort-based model at regional scales across the Pacific Northwest.
Research Highlights: Two genets of Armillaria altimontana Brazee, B. Ortiz, Banik, and D.L. Lindner and five genets of Armillaria solidipes Peck (as A. ostoyae [Romagnesi] Herink) were identified and spatially mapped within a 16-year-old western white pine (Pinus monticola Doug.) plantation, which demonstrated distinct spatial distribution and interspecific associations. Background and Objectives: A. solidipes and A. altimontana frequently co-occur within inland western regions of the contiguous USA. While A. solidipes is well-known as a virulent primary pathogen that causes root disease on diverse conifers, little has been documented on the impact of A. altimontana or its interaction with A. solidipes on growth, survival, and the Armillaria root disease of conifers. Materials and Methods: In 1971, a provenance planting of P. monticola spanning 0.8 ha was established at the Priest River Experimental Forest in northern Idaho, USA. In 1987, 2076 living or recently dead trees were measured and surveyed for Armillaria spp. to describe the demography and to assess the potential influences of Armillaria spp. on growth, survival, and the Armillaria root disease among the study trees. Results: Among the study trees, 54.9% were associated with Armillaria spp. The genets of A. altimontana and A. solidipes comprised 82.7% and 17.3% of the sampled isolates (n = 1221) from the study plot, respectively. The mapped distributions showed a wide, often noncontiguous, spatial span of individual Armillaria genets. Furthermore, A. solidipes was found to be uncommon in areas dominated by A. altimontana. The trees colonized by A. solidipes were associated with a lower tree growth/survival and a substantially higher incidence of root disease than trees colonized only by A. altimontana or trees with no colonization by Armillaria spp. Conclusions: The results demonstrate that A. altimontana was not harmful to P. monticola within the northern Idaho planting. In addition, the on-site, species-distribution patterns suggest that A. altimontana acts as a long-term, in situ biological control of A. solidipes. The interactions between these two Armillaria species appear critical to understanding the Armillaria root disease in this region.
Although a natural ecological process, wildfire in unhealthy forests can be uncharacteristically destructive. Fuel treatments—such as thinning, mowing, prescribed fire, or managed wildfire—can help reduce or redistribute the flammable fuels that threaten to carry and intensify fire. Using both field-tested data and computer simulations, Pacific Northwest Research Station scientists are addressing critical questions such as Are we treating enough of the landscape to restore fire-adapted forests? Are fuel treatments effective at changing fire behavior? Together with land managers, fuel planners, and other partners, our scientists are helping public land management agencies move toward a future of fire-resilient forests and communities.
Warming temperatures are projected to greatly alter many forests in the Pacific Northwest. MC2 is a dynamic global vegetation model, a climate-aware, process-based, and gridded vegetation model. We calibrated and ran MC2 simulations for the Blue Mountains Ecoregion, Oregon, USA, at 30 arc-second spatial resolution. We calibrated MC2 using the best available spatial datasets from land managers. We ran future simulations using climate projections from four global circulation models (GCM) under representative concentration pathway 8.5. Under this scenario, forest productivity is projected to increase as the growing season lengthens, and fire occurrence is projected to increase steeply throughout the century, with burned area peaking early- to mid-century. Subalpine forests are projected to disappear, and the coniferous forests to contract by 32.8%. Large portions of the dry and mesic forests are projected to convert to woodlands, unless precipitation were to increase. Low levels of change are projected for the Umatilla National Forest consistently across the four GCM’s. For the Wallowa-Whitman and the Malheur National Forest, forest conversions are projected to vary more across the four GCMbased simulations, reflecting high levels of uncertainty arising from climate. For simulations based on three of the four GCMs, sharply increased fire activity results in decreases in forest carbon stocks by the mid-century, and the fire activity catalyzes widespread biome shift across the study area. We document the full cycle of a structured approach to calibrating and running MC2 for transparency and to serve as a template for applications of MC2.
Because wildfire size and frequency are expected to increase in many forested areas in the United States, organizations involved in forest and wildfire management could arguably benefit from working together and sharing information to develop strategies for how to adapt to this increasing risk. Social capital theory suggests that actors in cohesive networks are positioned to build trust and mutual understanding of problems and act collectively to address these problems, and that actors engaged with diverse partners are positioned to access new information and resources that are important for innovation and complex problem solving. We investigated the patterns of interaction within a network of organizations involved in forest and wildfire management in Oregon, USA, for evidence of structural conditions that create opportunities for collective action and learning. We used descriptive statistical analysis of social network data gathered through interviews to characterize the structure of the network and exponential random graph modeling to identify key factors in the formation of network ties. We interpreted our findings through the lens of social capital theory to identify implications for the network’s capacity to engage in collective action and complex problem-solving about how to adapt to environmental change. We found that tendencies to associate with others with similar management goals, geographic emphases, and attitudes toward wildfire were strong mechanisms shaping network structure, potentially constraining interactions among organizations with diverse information and resources and limiting opportunities for learning and complex problem-solving needed for adaptation. In particular, we found that organizations with fire protection and forest restoration goals comprised distinct networks despite sharing concern about the problem of increasing wildfire risk.
The 2014 Carlton Complex Fire in north-central Washington was a “megafire.” It burned 167,000 acres within 24 hours, driven by strong warm winds through a drought-ridden landscape.
Station scientists wanted to know how nonindustrial private forest owners in eastern Oregon perceive and address wildfire risk. They discovered that 75 percent of surveyed owners of ponderosa pine forests had treated some portion of their land between 2003 and 2008.
A core goal of the National Cohesive Wildland Fire Management Strategy is to manage fuels at the landscape scale to restore and maintain fire-resilient landscapes. Prescribed burning and mechanical tree removal are two common ways to reduce hazardous fuels.
Fuels-reduction treatments are an opportune time to remove trees in poor health and significantly increase the proportion of high-vigor trees remaining in the stand after treatment.