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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington; a Synthesis of the Relevant Biophysical Science and Implications for Future Land Management
Abstract and Figures
Land managers in the Pacific Northwest have reported a need for updated scientific
information on the ecology and management of mixed-conifer forests east of the
Cascade Range in Oregon and Washington. Of particular concern are the moist
mixed-conifer forests, which have become drought-stressed and vulnerable to
high-severity fire after decades of human disturbances and climate warming. This
synthesis responds to this need. We present a compilation of existing research
across multiple natural resource issues, including disturbance regimes, the legacy
effects of past management actions, wildlife habitat, watershed health, restoration
concepts from a landscape perspective, and social and policy concerns. We provide
considerations for management, while also emphasizing the importance of local
knowledge when applying this information at the local and regional level.
Figures - uploaded by Kevin O'Hara
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... East-side forests are characterized by short growing seasons and low summer moisture, with spatial heterogeneity created by deeper soils and north-facing slopes (Franklin and Dyrness 1988, Stine et al. 2014). Fire regimes differ by elevation, with low-severity, high-frequency fire typical at lower elevations, and high-severity, low-frequency fire at higher, wetter sites, with a mixed-severity and frequency regime in between (Stine et al. 2014). ...
... East-side forests are characterized by short growing seasons and low summer moisture, with spatial heterogeneity created by deeper soils and north-facing slopes (Franklin and Dyrness 1988, Stine et al. 2014). Fire regimes differ by elevation, with low-severity, high-frequency fire typical at lower elevations, and high-severity, low-frequency fire at higher, wetter sites, with a mixed-severity and frequency regime in between (Stine et al. 2014). Local spatial heterogeneity in plant communities is high, with north-facing slopes often supporting more mesic plant communities than adjacent south-facing slopes, and both fire and logging causing a patchwork of different stand conditions and ages. ...
... Nonclimatic stressors for early-seral habitat include timber and wood harvest, wildfire, roads, invasive species, grazing, and recreation (Stine et al. 2014, USDA FS 2011. Loss of large snags, logs, and remnant trees following fire or harvest can have negative effects on wildlife habitat in early-seral landscapes. ...
Climate change will affect physical hydrological processes and resource values that are influenced by hydrology, including water available for human uses, water quality, roads, and developed infrastructure. Climate change is likely to alter the amount,
timing, and type of precipitation, leading to less snow, receding glaciers, more winter precipitation as rain, earlier snowmelt, and fewer summer precipitation events. Anticipated streamflow changes include higher winter peak flow events associated with increased rain and rain-on-snow in mid to higher elevations, and overall declines in summer baseflows. Slower groundwater recession in areas with permeable volcanic rocks may dampen peak-flow increases and summer low-flow declines. Increasing temperature and changes in the amount and timing of precipitation and runoff will also affect water quality, water availability, soils, and vegetation. Roads and trails that were built decades ago are highly sensitive to climate change because
of declining condition. Culverts remaining in place beyond their design life are less resilient to high flows and bed load movement and have a higher likelihood of structural failure. In the face of higher severity storms, aging infrastructure and outdated design standards can lead to increased incidents of road failure.
In-stream restoration techniques (e.g., adding wood to streams) will improve hydrologic connectivity in floodplains and increase water storage capacity. Reintroducing or supporting populations of American beaver (Castor canadensis Kuhl) may also help to slow water movement and increase water storage. Working across boundaries on water protection plans and water conservation will help
ensure adequate water supplies. Sediment delivery to streams from roads can be reduced by disconnecting ditch lines from streams during watershed restoration, timber projects, vegetation management, and road management. Landslide risk will be reduced by stabilizing slopes, mapping landslide risk, locating or relocating
roads in areas that are less vulnerable to landslides, and decommissioning roads in vulnerable locations. Streamflow projections that consider climate change can inform decisions on structure type and sizing at stream crossings, as well as decisions about travel management and restoration. Increasing resilience of
recreation facilities, stream crossings, historical and cultural sites, and points of diversion to peak flows will improve public safety.
... The assumption that eastern Cascade mid-elevation forests have intermediate or "mixed" fire regimes both in terms of severity and frequency is understandable, but not necessarily correct (Agee, 1994). Mixed-conifer forest fire regimes can vary depending on moisture levels, topography, and site aspect (Agee, 1993;Stine et al., 2014). At present, dry mixed-conifer forests typically experience more frequent low-severity fires, primarily due to less fuel, while moist mixed-conifer forests may see more variability in fire severity and frequency, as well as stand structure and age (Hessburg et al., 2007). ...
... Given the large spatial extent of MEMC forests in the eastern Cascades, and in light of current and future climate change, a thorough understanding of the regional fire regime as evidenced at this site and others like it will provide valuable information about wildfire disturbance dynamics. These efforts can contribute to developing better policy aimed at managing the long-term resiliency of these forests (Buechling and Baker, 2004;Everett et al., 1999;Hagmann et al., 2014, Haugo et al., 2010Stine et al., 2014). ...
... with findings from several dendrochronological-based studies of historic fire activity in MEMC forests of eastern Washington and Oregon (see Stine et al., 2014 for a review). ...
Fire histories of mid-elevation mixed-conifer forests are uncommon in the eastern Cascades, limiting our understanding of long-term fire dynamics in these environments. The purpose of this study was to reconstruct the fire and vegetation history for a moist mid-elevation mixed-conifer site, and to determine whether Holocene fire activity in this watershed was intermediate to fire regimes observed at higher and lower elevations in the eastern Cascades. Fire activity and vegetation change was reconstructed using macroscopic charcoal and pollen analysis of sediment core from Long Lake. This site is located ~45 km west of Yakima, WA, and exists in a grand fir-dominated, mixed-conifer forest. Results show low fire activity from ca. 9870 to 6000 cal yr BP, after which time fire increased and remained frequent until ca. 500 cal yr BP. A woodland environment existed at the site in the early Holocene, with the modern coniferous forest establishing ca. 6000–5500 cal yr BP. A mixed-severity fire regime has existed at the site for the past ~6000 years, with both higher- and lower-severity fire episodes occurring on average every ~80–100 years. However, only one fire episode occurred in the Long Lake watershed during the past 500 years, and none within the past ~150 years. Based on a comparison with other eastern Cascade sites, Holocene fire regimes at Long Lake, particularly during the late Holocene, appear to be intermediate between those observed at higher- and lower elevation sites, both in terms of fire severity and frequency.
... jeffreyi), and mixed evergreen forests of Douglas-fir, tanoak (Notholithocarpus densiflorus), madrone (Arbutus menziesii), and myrtlewood (Umbellularia californica). Historical fire regimes were generally characterized by low-severity fires 3 with return intervals of 5-25 years, and moderate-severity fire regimes with return intervals of 25-75 years , 2018, Agee 1996, Heyerdahl et al. 2001, Hessburg et al. 2007Perry et al. 2011, Stine et al. 2014). ...
... In many dry zone forests, broad-scale re-alignment is required (Kates et al. 2012, Stine et al. 2014, Hessburg et al. 2016. The cumulative interactions of increasing moisture deficits, insect vulnerability, and occurrence of uncharacteristically large and severe fires within the fireprone provinces rises to this level of concern (Jones et al. 2016). ...
The 1994 Northwest Forest Plan signified a watershed moment for natural resource management on federal lands in the Pacific Northwest. It established clear priorities for ecologically motivated management of terrestrial and aquatic ecosystems and biodiversity conservation on nearly 10 million hectares of public lands in Oregon, Washington, and northern California. Conservation reserves were the primary means of safeguarding remaining old forest and riparian habitats, and the populations of northern spotted owl, marbled murrelet, and Pacific salmon that depend on them. As envisioned, reserves would provide habitat for the protected species during a lengthy recovery period. However, reserve strategies were grounded on two tacit assumptions: the climate is stable, and there are limited disruptions by invasive species; neither of which has turned out to be true. Managing for northern spotted owls and other late-successional and old forest associated species within the context of static reserves has turned out to be incredibly challenging. As climatic and wildfire regimes continually shift and rapidly reshape landscapes and habitats, conservation efforts that rely solely on maintaining static conditions within reserves are likely to fail, especially in seasonally dry forests. Forest planners and managers are now occupied with efforts to amend or revise Forest Plans within the NWFP area. According to the 2012 Planning Rule, their charge is to focus management on restoring ecosystem integrity and resiliency and address impacts of climate change and invasive species. Here, we integrate information from ecological and climate sciences, species recovery planning, and forest plan monitoring to identify management adaptations that can help managers realize the original Plan goals as integrated with the goals of the 2012 Planning Rule. There are no guarantees associated with any future planning scenario; continual learning and adaptation are necessary. Our recommendations include managing for dynamic rather than static conditions in seasonally dry forests, managing dynamically shifting reserves in wetter forests, where dynamics occur more slowly, reducing stressors in aquatic and riparian habitats, and significantly increased use of adaptive management and collaborative planning.
... stand-replacing wildfires are a primary driver of succession in western forests, but such fires were historically rare, typically recurring on timescales of > 100 years [4,5]. With climate change, these extreme fire events have become increasingly common [6][7][8], and are likely to play a pivotal role in reshaping North American forest communities [9][10][11]. ...
... Hereafter we use "Washington" and "BC" to refer to the whole landscape in each region. Our study areas have high-severity fire regimes typical of western sub-boreal and montane forests, with large, stand-replacing fires recurring every 100-300 years on average [4,5]. ...
Background
Wildfires and forestry activities such as post-fire salvage logging are altering North American forests on a massive scale. Habitat change and fragmentation on forested landscapes may threaten forest specialists, such as Pacific marten (Martes caurina), that require closed, connected, and highly structured habitats. Although marten use burned landscapes, it is unclear how these animals respond to differing burn severities, or how well they tolerate additional landscape change from salvage logging.
Methods
We used snow tracking and GPS collars to examine marten movements in three large burns in north-central Washington, USA (burned in 2006) and central British Columbia, Canada (burned in 2010 and 2017). We also assessed marten habitat use in relation to areas salvage-logged in the 2010 burn. We evaluated marten path characteristics in relation to post-fire habitat quality, including shifts in behaviour when crossing severely-disturbed habitats. Using GPS locations, we investigated marten home range characteristics and habitat selection in relation to forest cover, burn severity, and salvage logging.
Results
Marten in the 2006 burn shifted from random to directed movement in areas burned at high severity; in BC, they chose highly straight paths when crossing salvage-blocks and meadows. Collared marten structured their home ranges around forest cover and burn severity, avoiding sparsely-covered habitats and selecting areas burned at low severity. Marten selected areas farther from roads in both Washington and BC, selected areas closer to water in the 2006 burn, and strongly avoided salvage-logged areas of the 2010 burn. Marten home ranges overlapped extensively, including two males tracked concurrently in the 2010 burn.
Conclusions
Areas burned at low severity provide critical habitat for marten post-fire. Encouragingly, our results indicate that both male and female marten can maintain home ranges in large burns and use a wide range of post-fire conditions. However, salvage-logged areas are not suitable for marten and may represent significant barriers to foraging and dispersal.
... The result is a mosaic of forest successional patches that reside within the larger physiognomic patchwork. As with physiognomic types, frequent disturbance can override site potential and inhibit succession to closed-canopy forests or dominance by fire-intolerant species (Agee 1996, 1998, Hessburg et al. 2005, North et al. 2009, Stine et al. 2014a). ...
... Frequent fire reduces the intensities and severities of subsequent fires by maintaining tree densities and live and dead fuel loads at levels below those that local site productivity could readily support (Reynolds et al. 2013, Stine et al. 2014a, Safford and Stevens 2017, Addington et al. 2018 ...
Implementation of wildfire‐ and climate‐adaptation strategies in seasonally dry forests of western North America is impeded by numerous constraints and uncertainties. After more than a century of resource and land use change, some question the need for proactive management, particularly given novel social, ecological, and climatic conditions. To address this question, we first provide a framework for assessing changes in landscape conditions and fire regimes. Using this framework, we then evaluate evidence of change and lack of change in contemporary conditions relative to those maintained by active fire regimes, i.e., those uninterrupted by a century or more of human‐induced fire exclusion. The cumulative results of more than a century of research document a persistent and substantial fire deficit and widespread alterations to ecological structures and functions. These changes are not necessarily apparent at all spatial scales or in all dimensions of fire regimes and forest and nonforest conditions. Nonetheless, loss of the once abundant influence of low‐ and moderate‐severity fires suggests that while some ecosystems within these landscapes may not be directly altered by fire exclusion, even the least fire‐prone among them may be affected by alteration of the surrounding landscape and, consequently, ecosystem functions. Vegetation spatial patterns in fire‐excluded forested landscapes no longer reflect the heterogeneity maintained by interacting fires of active fire regimes. Live and dead vegetation (surface and canopy fuels) is generally more abundant and continuous than before European colonization. As a result, current conditions are more vulnerable to the direct and indirect effects of seasonal and episodic increases in drought and fire, especially under a rapidly warming climate. Long‐term fire exclusion and contemporaneous social‐ecological influences continue to extensively modify seasonally dry forested landscapes. Management that realigns or adapts fire‐excluded conditions to the seasonal and episodic increases in drought and fire can moderate ecosystem transitions as forests and human communities adapt to changing climatic and disturbance regimes. As adaptation strategies are developed, evaluated, and implemented, objective scientific evaluation of ongoing research and monitoring can aid differentiation of warranted and unwarranted uncertainties.
... Another consequence of a changed climate, combined with the homogeneous character of forests that are managed for industrial purposes, is that these forests become more susceptible to pests (Folke et al., 2004) and fires (Stine et al., 2014;Hessburg et al., 2019) which can also affect riparian vegetation. The climate crisis is expected to cause earlier starts of the fire season (Stocks et al., 1998), higher fire intensity and larger fire areas (Dale et al., 2001). ...
Riparian zones are species-rich and functionally important ecotones that sustain physical, chemical and ecological balance of ecosystems. While scientific, governmental and public attention for riparian zones has increased over the past decades, knowledge on the effects of the majority of anthropogenic disturbances is still lacking. Given the increasing expansion and intensity of these disturbances, the need to understand simultaneously occurring pressures grows. We have conducted a literature review on the potential effects of anthropogenic pressures on boreal riparian zones and the main processes that shape their vegetation composition. We visualised the observed and potential consequences of flow regulation for hydropower generation, flow regulation through channelisation, the climate crisis, forestry, land use change and non-native species in a conceptual model. The model shows how these pressures change different aspects of the flow regime and plant habitats, and we describe how these changes affect the extent of the riparian zone and dispersal, germination, growth and competition of plants. Main consequences of the pressures we studied are the decrease of the extent of the riparian zone and a poorer state of the area that remains. This already results in a loss of riparian plant species and riparian functionality, and thus also threatens aquatic systems and the organisms that depend on them. We also found that the impact of a pressure does not linearly reflect its degree of ubiquity and the scale on which it operates. Hydropower and the climate crisis stand out as major threats to boreal riparian zones and will continue to be so if no appropriate measures are taken. Other pressures, such as forestry and different types of land uses, can have severe effects but have more local and regional consequences. Many pressures, such as non-native species and the climate crisis, interact with each other and can limit or, more often, amplify each other’s effects. However, we found that there are very few studies that describe the effects of simultaneously occurring and, thus, potentially interacting pressures. While our model shows where they may interact, the extent of the interactions thus remains largely unknown.
... An important old-growth conservation strategy is mechanical thinning of stands to reduce competition around old-growth trees and make them more resistant to uncharacteristically severe drought, insect, and fire effects (Fettig et al. 2007, Millar andStephenson 2015). An increasing number of shade-tolerant trees that recruited into eastern Oregon forest stands in the absence of fire are ≥53 cm, and scientists and managers are concerned that the 21-inch rule limits the ability to adapt stands to future climate and disturbance stressors (Stine et al. 2014, Johnston 2017, Spies et al. 2018. ...
Abstract The U.S. Forest Service is reconsidering policies that limit the size of trees that can be removed in the course of restoration treatments in dry forests of eastern Oregon. To evaluate the effects of diameter limits on the ability of managers to meet restoration objectives, we used an existing network of long‐term research plots to summarize historical and contemporary structure and composition of mixed‐conifer forests within a one million‐ha study area in eastern Oregon. Then, we used a novel thinning simulation procedure to quantify the degree to which thinning using different diameter limits restored stands to historical conditions. Contemporary mixed‐conifer forests within the study area are significantly denser, have more basal area, and have a greater proportion of shade‐tolerant species than historical conditions. Our simulations of thinning under current policy that prohibits cutting of trees ≥53 cm show that a quarter of mixed‐conifer stands cannot be restored to within the historical range of basal area or density. Those stands that could be restored to within historical basal area ranges still had a substantially higher component of shade‐tolerant trees than historical stands. Permitting larger shade‐tolerant trees to be removed allowed restoration of all or most of stands to within historical structural and compositional ranges. Forest conditions in the late 1800s may not necessarily provide the best template for management because climate and disturbance projections suggest that eastern Oregon forests will be less well suited to shade‐tolerant species in the future. Adapting stands to future conditions will require robust monitoring of forest structural and compositional response to restoration treatments.
Fire has been an important catalyst of change in Pacific Northwest forests throughout the Holocene. The role of fire varied across this biophysically diverse region prior to European colonization, but fire exclusion and logging drastically altered forest conditions during the 19th and 20th centuries. Despite recent increases in area burned and several large wildfires with devastating social and economic consequences, area burned in recent decades remains far less than under historical regimes across most of the region. Some dry forest landscapes have experienced profound change through uncharacteristically severe fires. In moist and cold forest landscapes, wildfires have enhanced biodiversity through the creation of structurally complex early-seral habitats. Area burned is expected to double or triple in the future under a warming climate. Strategies to adapt to future wildfires vary among historical regimes and biophysical settings and will require collaborative engagement and adaptive management to facilitate ecological change at meaningful scales.
The overwhelming majority of information on historical forest conditions in western North America comes from public lands, which may provide an incomplete description of historical landscapes. In this study we made use of an archive containing extensive timber survey data collected in the early 1920’s from privately owned forestland. These data covered over 50,000 ha and effectively represent a 19% sample of the entire area. The historical forest conditions reconstructed from these data fit the classic model of frequent‐fire forests: large trees, low density, and pine‐dominated. However, unlike other large‐scale forest reconstructions our study area exhibited relatively low overall variability in forest structure and composition across the historical landscape. Despite having low variability our analyses revealed evidence of biophysical controls on tree density and pine fraction. Annual climatic variables most strongly explained the range in historical tree densities, whereas historical pine fraction was explained by a combination of topographic and climatic variables. Contemporary forest inventory data collected from both public and private lands within the same general area, albeit not a direct remeasurement, revealed substantial increases in tree density and greatly reduced pine fractions relative to historical conditions. Contemporary forests exhibited a far greater range in these conditions than what existed historically. These findings suggest that private forestland managed with multi‐aged silviculture may be similar to public forestland with respect to departure in forest structure and compositions from that of historical forests. However, there may be differences between management objectives that favor timber production, more typical on private lands, versus those that favor restoration, increasingly supported on public lands.
Wildland fires (WLF) have become more frequent, larger, and severe with greater impacts to society and ecosystems and dramatic increases in firefighting costs. Forests throughout the range of ponderosa pine in Oregon and Washington are jeopardized by the interaction of anomalously dense forest structure, a warming and drying climate, and an expanding human population. These forests evolved with frequent interacting disturbances including low-severity surface fires, droughts, and biological disturbance agents (BDAs). Chronic low-severity disturbances were, and still are, critical to maintaining disturbance resistance, the property of an ecosystem to withstand disturbance while maintaining its structure and ecological function. Restoration of that historical resistance offers multiple social and ecological benefits.
Moving forward, we need a shared understanding of the ecology of ponderosa pine forests to appreciate how restoring resistance can reduce the impacts of disturbances. Given contemporary forest conditions, a warming climate, and growing human populations, we predict continued elevation of tree mortality from drought, BDAs, and the large high-severity WLFs that threaten lives and property as well as ecosystem functions and services. We recommend more comprehensive planning to promote greater use of prescribed fire and management of reported fires for ecological benefits, plus increased responsibility and preparedness of local agencies, communities and individual homeowners for WLF and smoke events. Ultimately, by more effectively preparing for fire in the wildland urban interface, and by increasing the resistance of ponderosa pine forests, we can greatly enhance our ability to live with fire and other disturbances.
We conducted a regional-scale evaluation of landscape permeability for large carnivores in Washington and adjacent portions of British Columbia and Idaho. We developed geographic information system based landscape permeability models for wolves (Canis lupus), wolverine (Gulo gulo), lynx (Lynx canadensis), and grizzly bear (Ursus arctos). We also developed a general large carnivore model to provide a single generalization of the predominant landscape patterns for the four focal species. The models evaluated land cover type, road density, human population density, elevation, and slope to provide an estimate of landscape permeability. We identified five concentrations of large carnivore habitat between which we evaluated landscape permeability. The habitat concentration areas were the southern Cascade Range, the north-central Cascade Range, the Coast Range, the Kettle-Monashee Ranges, and the Selkirk-Columbia Mountains. We evaluated landscape permeability in fracture zones between these areas, including the 1-90 Snoqualmie Pass area, the Fraser-Coquihalla area, the Okanogan Valley, and the upper Columbia and Pend Oreille River valleys. We identified the portions of the Washington state highway system that passed through habitat linkages between the habitat concentration areas and areas accessible to the focal species. This analysis provides a consistent measure of estimated landscape permeability across the analysis area, which can be used to develop conservation strategies, contribute to future field survey efforts, and help identify management priorities for the focal species.
Indigenous populations are projected to face disproportionate impacts as a result of climate change in comparison to nonindigenous populations. For this reason, many American Indian and Alaska Native tribes are identifying and implementing culturally appropriate strategies to assess climate impacts and adapt to projected changes. Traditional ecological knowledge (TEK), as the indigenous knowledge system is called, has the potential to play a central role in both indigenous and nonindigenous climate change initiatives. The detection of environmental changes, the development of strategies to adapt to these changes, and the implementation of sustainable land-management principles are all important climate action items that can be informed by TEK. Although there is a significant body of literature on traditional knowledge, this synthesis examines literature that specifically explores the relationship between TEK and climate change. The synthesis describes the potential role of TEK in climate change assessment and adaptation efforts. It also identifies some of the challenges and benefits associated with merging TEK with Western science, and reviews the way in which federal policies and administrative practices facilitate or challenge the incorporation of TEK in climate change initiatives. The synthesis highlights examples of how tribes and others are including TEK into climate research, education, and resource planning and explores strategies to incorporate TEK into climate change policy, assessments, and adaptation efforts at national, regional, and local levels.
The concept of resilience has evolved considerably since Holling's (1973) seminal paper. Different interpretations of what is meant by resilience, however, cause confusion. Resilience of a system needs to be considered in terms of the attributes that govern the system's dynamics. Three related attributes of social-ecological systems (SESs) determine their future trajectories: resilience, adaptability, and transformability. Resilience (the capacity of a system to absorb disturbance and reorganize while undergoing change so as to still retain essentially the same function, structure, identity, and feedbacks) has four components-latitude, resistance, precariousness, and panarchy-most readily portrayed using the metaphor of a stability landscape. Adaptability is the capacity of actors in the system to influence resilience (in a SES, essentially to manage it). There are four general ways in which this can be done, corresponding to the four aspects of resilience. Transformability is the capacity to create a fundamentally new system when ecological, economic, or social structures make the existing system untenable. The implications of this interpretation of SES dynamics for sustainability science include changing the focus from seeking optimal states and the determinants of maximum sustainable yield (the MSY paradigm), to resilience analysis, adaptive resource management, and adaptive governance.
Photographs taken before 1925 were compared with photos taken as recently as 1992 to interpret changes within ecosystems in the Blue Mountains of Oregon. Nearly all systems exhibited some degree of conversion from herbaceous to woody forms of vegetation. Nonforested ecosystems improved markedly except in the riparian-aquatic habitats. Forested ecosystems were stressed from stand stagnation, conversion from pine to fir, serious insect infestations, and crown fires. -from Authors
