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

Peter Stine, Paul Hessburg, Thomas Spies, Marc Kramer, Christopher J. Fettig, 

Andrew Hansen, John Lehmkuhl, Kevin O’Hara, Karl Polivka, Peter Singleton, 

Susan Charnley, Andrew Merschel, and Rachel White 

United States Department of Agriculture

Forest 

Service

Pacific Northwest 

Research Station

General Technical Report

PNW-GTR-897

September

2014
Authors

Peter Stine is a biogeographer and Christopher Fettig is a research entomologist, 

U.S. Department of Agriculture, Forest Service, Pacific Southwest Research 

Station, 1731 Research Park Drive, Davis, CA 95618; Paul Hessburg is a research 

ecologist, John Lehmkuhl is an emeritus scientist, Karl Polivka is a research fish 

biologist, and Peter Singleton is an ecologist, U.S. Department of Agriculture, 

Forest Service, Pacific Northwest Research Station, Forestry Sciences Laboratory, 

1133 N. Western Ave., Wenatchee, WA 98801; Thomas Spies is a research forester, 

U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, 

Forestry Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331; Susan 

Charnley is a research social scientist, and Rachel White is a science writer/editor, 

U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, 

Forestry Sciences Laboratory, 620 SW Main St., Suite 400, Portland, OR 97205; 

Marc Kramer is an associate professor, University of Florida, 3165A McCarty Hall, 

Gainesville, FL 32611; Andrew Hansen is a professor, Montana State University, 

Landscape Biodiversity Lab, 310 Lewis Hall, Bozeman, MT 59717; Kevin O’Hara 

is a professor, University of California–Berkeley, Department of Environmental 

Science, Policy, and Management, 130 Mulford Hall #3114, Berkeley, CA 94720; and 

Andrew Merschel is faculty research assistant, Department of Forest Ecosystems 

and Society, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331.

Cover photographs: (upper left and lower right) Okanogan-Wenatchee National 

Forest, Washington, by John Marshall; (lower left) Columbia River Gorge, Oregon, 

by Miles Hemstrom; (upper right) Deschutes National Forest, Oregon, by Tom Spies.

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provider and employer. 
Abstract

Stine, Peter; Hessburg, Paul; Spies, Thomas; Kramer, Marc; Fettig, Christopher J.; Hansen, Andrew; Lehmkuhl, John; O’Hara, Kevin; Polivka, Karl; 

Singleton, Peter; Charnley, Susan; Merschel, Andrew; White, Rachel. 2014. 

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. Gen. Tech. Rep. PNW-GTR-897. Portland, OR: U.S. 

Department of Agriculture, Forest Service, Pacific Northwest Research Station. 

254 p. 

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.

Keywords: Disturbance ecology, landscape restoration, land management, 

resilience, stewardship.
ii

Executive Summary

Millions of hectares of Western forests have been negatively affected by drought 

and by insect and disease outbreaks, and are overloaded with fuel, priming them for 

unusually severe and extensive wildfires. In light of these trends, public support for 

forest restoration has grown. One priority of the USDA Forest Service is to restore 

resiliency to forest and range ecosystems, enabling them to cope with an uncertain 

future. Natural resource managers and policymakers are awash in information from 

a growing body of science, with little time to sort through it, let alone assimilate the 

many different sources and interpretations of the best available science. 

Regional research and management executives requested a review of the large 

body of scientific information on eastside moist mixed-conifer (MMC) forests 

within the context of the broader forest landscape in eastern Oregon and Washington. This focus was motivated by a lack of up-to-date management guidelines, 

scientific synthesis, and consensus among stakeholders about management direction 

in the diverse MMC type. 

Understanding complex ecological and social processes and functions across 

landscapes requires an integrated assessment that combines multiple scientific 

disciplines across spatial and temporal scales. Accordingly, this synthesis compiles 

existing research, makes connections across disparate sources, and addresses 

multilayered natural resource issues. It has been prepared to assist land managers in 

updating existing management plans and on-the-ground projects that are intended 

to promote resilience in MMC forests and riparian areas. We consider management 

flexibility at the local scale critically important for contending with specific legacy 

effects of management and the substantial ecological variation in MMC forest 

conditions, as well as for adapting management to local social and policy concerns.

Our hope is that this synthesis will serve as a reference that provides a condensed and integrated understanding of the current state of knowledge regarding 

MMC forests, as well as an extensive list of published sources where readers can 

find further information. We also hope to enhance cross-disciplinary communication and enrich dialogue among Forest Service researchers, managers, and external 

stakeholders as we address common restoration concerns and management challenges for MMC forests in eastern Oregon and Washington.

Key sections of this synthesis include:

• A description of MMC forests and their context in the broader landscape 

of eastern Oregon and Washington.

• Key concepts of restoration and the landscape perspective.

• A comprehensive summary of pre-Euro-American settlement conditions 

in MMC forests.

One priority of the 

USDA Forest Service 

is to restore resiliency 

to forest and range 

ecosystems, enabling 

them to cope with an 

uncertain future. 
iii

• A description of the socioeconomic context in the region.

• A summary of human impacts on MMC forests.

• Broad management implications of research findings.

• A practical list of management considerations for diagnosing restoration 

needs and designing landscape approaches.

Moist Mixed-Conifer Forests

Mixed-conifer forests are a major component of the dry-to-wet conifer forest complex that is widely distributed across eastern Oregon and Washington. Among other 

factors, these forests are important for carbon sequestration, watershed protection, 

terrestrial and aquatic wildlife habitat, and outdoor recreation, and they provide 

economic opportunities through provisioning of a wide variety of forest products. 

MMC forests cover a large area east of the crest of the Cascade Range in Oregon 

and Washington, where grand fir, white fir, and Douglas-fir are the dominant latesuccessional tree species. MMC forests can be considered intermediate between 

drier conifer forests where pine was historically dominant and fire was typically 

frequent and low in severity, and wetter or cooler mixed-conifer forests where fire 

was less frequent and burned at higher severities. The MMC forest type is in a 

central position along a complex moisture, composition, and disturbance gradient of 

conifer forests in this region. This forest type is diverse and difficult to define, but 

potential vegetation types and current conditions can be used to help identify places 

where stands and landscapes need restoration. Historically, the forest landscape 

(from dry to wet) was a mosaic driven by variation in climate, soils, topography, 

and low- to mixed- and occasional high-severity fire.

Decades of wildfire suppression and exclusion, domestic livestock grazing, 

and selective and clearcut timber harvesting have interacted to alter the structure, 

composition, and disturbance regimes of these forests. MMC forests have become 

denser, have lost large individuals of fire-resistant tree species, and, on many sites, 

have become dominated by dense patches of shade-tolerant tree species that are less 

resistant to fire and less resilient to drought. These vegetation changes and management activities have shifted fire regimes toward less frequent, but larger and more 

severe fires, which tend to simplify the landscape into fewer, larger, and less diverse 

patches resulting in more homogenous conditions. Currently, many mixed-conifer 

forests are denser and more uniform in structure, and contain more live and dead 

fuel than they did historically. But the relative effects of human-caused changes, 

like fire suppression and timber harvesting, on these forests differ widely across the 

region. Thus, it is important to develop local, first-hand knowledge of the historical 

and contemporary disturbance regimes of these forests.
iv

Key Management Considerations

As we reviewed the scientific literature, our primary objective was to synthesize 

the large body of information into succinct findings that are supported by credible 

research and relevant to practitioners and others interested in management of MMC 

forests. Some of our findings are that:

• Historical range of variation (HRV) is useful as a guide but not as a 

target. Returning to it is no longer feasible or practical in some places 

because of changing climate, land use, and altered forest structure and 

composition. The contemporary concept of restoration goes beyond the 

oft-stated goal of reestablishing ranges of resource conditions that existed 

at some time in the past (e.g., prior to Euro-American settlement). Our 

ecological process-oriented approach supports restoration of conditions 

that may have occurred in the past under certain circumstances. However, 

the objective of ecological restoration is to create a resilient and sustainable 

forest under current and future conditions. It must be forward looking. 

Managers have some capacity to influence the future range of variability 

(FRV) to achieve desired future ecosystem conditions for a landscape.

• Disturbance regimes have been significantly altered after 150 years of 

Euro-American land use. Wildfires (along with insects, pathogens, and 

weather) were the dominant disturbance process shaping historical forest 

structure and composition. Low-, mixed-, and high-severity fires occurred 

in MMC forests, varying in size and occurrence across ecoregions. Small 

and medium fires were the most numerous, but large fires accounted for the 

majority of the area burned. Forests today neither resemble nor function as 

they did 150 years ago. 

• Moist mixed-conifer forests are more vulnerable to large, highseverity fire and insect outbreaks. Widespread anthropogenic changes 

have created more homogenized conditions in this forest type, generally 

in the form of large, dense, and multilayered patches of fire-intolerant tree 

species. These changes have substantially altered the resilience mechanisms 

associated with MMC forests. 

• Patterns of vegetation structure and composition in an eastside forest 

landscape shaped by intact disturbance regimes are diverse and differ 

over space and time. Resilience in these forests depends on this ecological 

heterogeneity. Euro-American settlement and early management practices 

put these landscapes on new and rapidly accelerating trajectories of change 
v

in vegetation composition and structure. Despite the change and variability, topography, soils, and elevation constrain these vegetation patterns and 

provide a template for understanding and managing landscape patterns. For 

example, south-facing aspects and ridges tended to burn more often and 

less severely than north-facing aspects and valleys. Landscape restoration 

strategies can capitalize on these tendencies. 

• Several wildlife species of conservation concern require structural 

complexity typical of mature and old forests, which are currently limited 

or at risk. With no action, maintaining adequate area and spatial patterns 

of old-forest habitats will be a challenge with the anticipated increases 

in severe fire and insect infestations expected in response to changed 

forest conditions and climate change. Restoration at a landscape scale 

will encounter challenges in retaining existing old-forest patches while 

transitioning to a more heterogeneous and resilient forest condition.

• Community-based collaborative groups can facilitate restoration in eastside national forests. One of the major constraints to increasing the pace 

and scale of restoration treatments on lands administered by the National 

Forest System (NFS) in eastern Oregon has been the lack of social agreement about how to achieve it. The Forest Service promotes collaboration 

as a means for helping diverse stakeholder groups come together and find 

an agreeable path forward. The creation of local groups and the Forest 

Service’s Collaborative Forest Landscape Restoration Program both offer 

innovations and demonstrate opportunities to improve capacity for restoration through collaborative processes.

Potential Applications

In the midst of complicated social and political forces, forest managers make decisions that require the application of complex scientific concepts to project-specific 

conditions. Decisions often must balance risks (e.g., elimination of fuels hazards 

vs. preservation of old-forest conditions) while acknowledging and allowing for 

uncertainties. Decisionmakers also must weigh tradeoffs associated with alternative 

courses of action to obtain multiple-use policy and land management objectives. 

We acknowledge this difficult task and the concurrent need to have access to and 

thoughtfully apply the best available scientific information.

It is not the role of the research community to direct management decisions. 

However, synthesis of research, identification of core scientific findings, and 

discernment of management implications in specific contexts are appropriate roles. 
vi

Research also has a role of working alongside managers to learn from successes and 

failures. We provide considerations for management and emphasize that their application to local and regional landscapes requires the skill and knowledge of practitioners to determine how best to apply them to a local situation with its particular 

management history. Legacy effects do matter, and one size does not fit all. 

In chapter 5, we synthesize principle findings gleaned from the body of scientific literature (summarized in chapter 4) as they pertain to management of MMC 

forests. These constitute the “take-home” messages that are intended to assist land 

managers in the execution of their work.

The social agreement and institutional capacity for restoring MMC forests 

is every bit as important as the scientific foundation for doing so. The ability to 

institute the kinds of changes managers will consider is directly a function of the 

capacity of the larger community to form working partnerships and a common 

vision.

Some of the potential changes in forest management evoked within this document represent a departure from “business as usual.” Land managers will decide 

how to proceed, and this will depend in large part on budget, policy, local circumstances, and ultimately the judgment of line officers. However, there are some ideas 

and observations from past work, both research and management, that suggest the 

need for some prudent adjustments in management approach. 
vii

Contents 

1 Chapter 1—Introduction

1 Purpose and Scope of This Synthesis

4 Current Management Context and Restoration Mandate

8 Structure of This Report—Where to Find Sections of Interest

9 Chapter 2—Definition of Moist Mixed-Conifer Forests and the Regional Context

17 Chapter 3—Ecological Principles of Restoration and Landscapes

18 The Concept of Resilience

21 Ecological Principles for Landscape Planning and Management

29 Chapter 4—Scientific Foundations

29 Ecological Composition, Patterns, and Processes Prior to EuroAmerican Settlement (Before About 1850)

31 Where Is the MMC Forest Located?

39 Vegetation Classification and Disturbance Regimes

53 Landscape Concepts

60 Natural Disturbance Factors

75 Animals of the Moist Mixed-Conifer Ecosystem

87 Aquatic Habitats

95 Human Impacts to Moist Mixed-Conifer Systems: Influences of the 

Last 100 to 150 Years

97 Timber Harvest and Associated Activities

98 Fire Exclusion and Natural Fire Dynamics

99 Grazing

100 Land Development

102 Climate Change

108 Changes in Vegetation

115 Changes in Disturbance Factors: Insects and Disease

115 Effects of Altered Disturbance Regimes, Land Use, and Climate Change

on Animal Populations and Habitats

128 Current Socioeconomic Context

130 Wood Processing Infrastructure and Business Capacity for

Forest Restoration

133 Biomass Utilization

135 Tribal Concerns

137 Recreation

139 Summary of Key Scientific Findings and Concepts

139 Landscapes

141 Disturbances

142 Vegetation
viii

144 Wildlife and Fish

146 Management Applications in the Field

147 Chapter 5—Management Considerations

147 Key Concepts to Consider in Management of MMC Forests

157 Stand Management—Silvicultural Tools and Their Role in 

Landscape Management

165 Chapter 6—Social Agreement and Institutional Capacity for 

Restoring Moist Mixed-Conifer Forests

165 Social Acceptability of Restoration Treatments Among Members 

of the Public

168 Collaboration

170 Institutional Capacity

170 Create Landscape Management Demonstration Areas

171 Incorporate the “All-Lands” Initiative

172 Revisit Current Management Constraints; Eastside Screens

175 Chapter 7—Conclusions

178 Acknowledgments

178 Metric Equivalents

178 Literature Cited

229 Appendix 1—List of Practical Considerations for Landscape 

Evaluation and Restoration Planning

235 Appendix 2—Regional-Scale Fire Regimes Group Classification 

for Oregon and Washington 

238 Appendix 3—Reconstructed Historical Vegetation Conditions 

Within Sampled Areas of the Blue Mountains Province 

250 Glossary
1

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

There is and always will be uncertainty and unpredictability in managed 

ecosystems, both as humans experience new situations and as these systems 

change because of management.

Surprises are inevitable. Active learning is the way in which this uncertainty is winnowed. Adaptive management acknowledges that policies 

must satisfy social objectives but also must be continually modified and be 

flexible for adaptation to these surprises. Adaptive management therefore 

views policies as hypotheses—that is; most policies are really questions 

masquerading as answers. Since policies are questions, then management actions become treatments in the experimental sense. The process 

of adaptive management includes highlighting uncertainties, developing 

and evaluating hypotheses around a set of desired system outcomes, and 

structuring actions to evaluate or “test” these ideas.

—Lance Gunderson (2000), Annual Review of Ecology and Systematics

Purpose and Scope of This Synthesis

Fire-prone mixed-conifer forests east of the crest of the Cascade Range in Oregon 

and Washington (hereafter, “the east side”) provide clean water, recreation, wildlife 

habitat, and many other important ecosystem goods and services (fig. 1). However, 

over the last century, many of these forests have become denser and less resilient to 

disturbance as a result of human activity, altered disturbance regimes, and climate 

warming. In the last few decades, many of these forests have also become further 

drought stressed and increasingly vulnerable to high-severity fire (Westerling et al. 

2006) and insect outbreaks as a result of climate change (Preisler et al. 2012). 

In the Pacific Northwest, research and management executives from the USDA 

Forest Service recently highlighted the need to update management guidance, 

scientific synthesis, and consensus among stakeholders regarding these challenges. 

This synthesis responds to this need. In particular, executives asked us to focus on 

eastside moist mixed-conifer (MMC) forests (see definition in chapter 2), within 

the context of the broader forest landscape on the east side. We have written this 

synthesis for a diverse audience of forest planners, managers, and engaged citizens. 

For this effort, we convened a team of government and university scientists to 

review the literature, synthesize knowledge and management options, and compile a 

bibliography. Team members were selected based on their experience and expertise, 

spanning a range of disciplines including aquatic ecology and fish biology, climate 

change, disturbance ecology, fire and forest ecology, landscape ecology, silviculture, social science, and wildlife biology. 

Chapter 1—Introduction
2

GENERAL TECHNICAL REPORT PNW-GTR-897

Figure 1—A moist mixed-conifer forest, Glass Creek Watershed, Okanogan-Wenatchee National 

Forest, eastern Washington. 

John Marshall
3

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

We focused the synthesis on the ecology of MMC forests but acknowledge that 

decisionmakers must address major issues surrounding the needs and values of 

human communities, so these decision processes are addressed as well. The forests 

of the east side represent complex patchworks of temperature, moisture, productivity, climate, and disturbance regimes, and their associated forest types (fig. 2), so 

we occasionally discuss forest types that adjoin the MMC type to improve overall 

context. The synthesis specifically addresses:

• Vegetation, landscape, and disturbance ecology.

• Wildlife habitats and populations; and aquatic ecosystems and 

associated species.

• Landscape approaches and perspectives.

• Silvicultural approaches.

• Climate change influences and climate futures.

Research findings summarized here can make a valuable contribution to 

restorative management, but it will be up to managers and program leaders to 

consider the unique ecological conditions of each landscape and to determine how 

this information guides specific land management decisions. To that end, findings 

here are intended to conceptually frame—not prescribe—land management. Such 

guidance is available in the new Forest Service Planning Rule (36 CFR Part 219), 

an important new administrative rule that applies current science to planning and 

Figure 2—A mixed-conifer landscape, Middle Fork of Gold Creek, Okanogan-Wenatchee National Forest, eastern Washington. 

John Marshall
4

GENERAL TECHNICAL REPORT PNW-GTR-897

management. We consider management flexibility at the local site level critically 

important for contending with specific legacy effects of management and the 

substantial ecological variation in MMC forest conditions, as well as for adapting 

management to local policy concerns.

In related dry mixed-conifer and ponderosa pine (Pinus ponderosa Lawson & 

C. Lawson) forest types, research and social license to begin restoration is relatively 

more advanced (e.g., see Franklin et al. 2013, Jain et al. 2012), and managers are 

proceeding with restoration treatments (e.g., see Hessburg et al. 2013, OWNF 2012). 

However, we include the pine and dry mixed-conifer types in our discussions 

because these dry and MMC types are entwined spatially and ecologically in 

eastern Oregon and Washington. 

Current Management Context and Restoration Mandate

Federal and state forest managers are charged with maintaining and restoring 

diverse, resilient (see “Glossary”), and productive forests in these fire-prone 

landscapes. Restoration can increase the resilience of eastside MMC forests, and 

reduce the ecological costs of high-severity wildfire and economic costs of fire 

suppression activities and postfire rehabilitation, along with the ecological and 

socioeconomic threats to adjoining state, private, and tribal lands. But achieving 

these goals is challenging without sufficient investment. Twentieth-century 

harvesting of large trees has reduced commercial operability in many eastside 

forests (e.g., see Rainville et al. 2008), and the value of remaining commercial 

products is often insufficient to cover the costs of restoration.

Developing and implementing sound management strategies requires up-todate knowledge of biological and physical processes that regulate forest ecosystem 

structure and function. We also require information on how humans have modified 

these processes, especially disturbance processes, which are a key to sculpting 

habitat and structural patterns (e.g., see Spies 1998). In this context, a number of 

factors are particularly relevant to eastside MMC forests:

• The processes and patterns of eastside forests have been altered over the 

past 100 to 150 years (depending upon location) by the combined cumulative 

effects of mining, livestock grazing, road and railroad construction, conversion of grasslands and shrublands to agriculture, timber harvesting, 

fire suppression and exclusion, urban and rural development, invasions of 

alien plant and animal species (including pathogens, insects, and aquatic 

organisms), expanding infestations of native diseases and insects, and 

anthropogenically induced climate change. 

We consider management flexibility at the 

local site level critically 

important for contending with specific legacy 

effects of management 

and the substantial 

ecological variation in 

moist mixed-conifer 

forest conditions, as 

well as for adapting 

management to local 

policy concerns.
5

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

• In many areas (e.g., those not burned in recent decades), today’s dry and MMC 

forests are denser, have more small trees and fewer large fire-tolerant trees, 

and are dominated by shade-tolerant and fire-intolerant tree species. These 

conditions have reduced the fire and drought tolerance of these forests. Large 

increases in surface and canopy fuel loads are widespread, resulting in greater 

risk of large and often severe wildfires, especially during extreme fire weather 

conditions. Furthermore, high stand densities increase competition for growing space among trees, thereby reducing the amount of water and nutrients 

available to individual trees and increasing their susceptibility to some insect 

and disease disturbances. These changes threaten the long-term sustainability 

of dry and MMC forests in general, and in particular the long-term survival of 

remaining large and very large trees that persist in overcrowded conditions.

• Climate change is already transforming forests in eastern Oregon and 

Washington because it is linked to ongoing drought as well as elevated levels 

of tree mortality attributed to insects, diseases, and wildfire. This transformation is occurring at a brisk pace, and the window of opportunity for effecting 

change in this trajectory is relatively short (likely a few decades).

Mandated conservation of threatened or endangered species, some of which 

have been threatened by landscape alterations (first bullet above), has added ecological and regulatory complexity to forest management. For example, in the eastern 

Cascades, restoration of dry and MMC forests, fire regimes, and fuel patterns 

is often constrained by the need to minimize disturbance in areas around active 

nest locations of the northern spotted owl (NSO) (Strix occidentalis caurina), to 

conserve its dense, late-successional and old-forest nesting, roosting, and foraging 

habitats. 

Currently, many landscapes of the east side have late-successional forest patterns that are out of sync with past and current fire regimes and are ecologically 

unsuited to providing large contiguous areas of late-successional habitat over time. 

In addition, much of the structural diversity in those stands is relatively short-lived 

because of the dominance of shade-tolerant tree species. Conservation of habitat for 

old forest species including NSO, northern goshawk (Accipiter gentilis), and pileated woodpecker (Dryocopus pileatus) needs to address the sustainability and continuous recruitment of that habitat. The revised recovery plan for the NSO (USFWS 

2011) has called for an active management approach for sustaining and recruiting 

old forest habitats in fire-prone forests of eastern Washington and Oregon. Similar 

considerations are also an issue for species outside of the range of the NSO, particularly northern goshawks and pileated woodpeckers.
6

GENERAL TECHNICAL REPORT PNW-GTR-897

Forest environments throughout the east side are ecologically and physiographically variable: rates of change in forest conditions and effects of historical 

influences vary with forest type, cultural geography, and physiographic region. 

Although broad-scale direction can have value at times, one-size-fits-all solutions 

generally will not work. Instead, considerations of local conditions, land use histories, and biophysical and landuse classifications can help address this variability. 

Managers report that maps of forest types across the east side are inconsistent in their classifications of vegetation associations. This creates a significant 

challenge for managing that vegetation for myriad uses and habitats. Managers 

also lack adequately detailed characterizations of how each forest type has been 

affected by natural, human, and climatic influences.

The relative merits of active versus passive management of forests to achieve 

ecological and socioeconomic goals are subject to fierce debate, which is driven by 

wide-ranging and often competing or conflicting societal values and is not likely 

to subside. Many citizens have expectations for sustainable delivery of ecosystem 

services from forests on public lands. Delivery is confounded by uncertainties 

regarding the long- versus short-term effects of various management practices on 

goods, services, and values. 

In the Western United States, Forest Service priorities focus on restoring ecosystems, managing wildland fires, and strengthening communities while providing 

jobs (Chief of the Forest Service address to the Pinchot Institute, 2013). Restoration on public lands1

 implies reenabling forests and grasslands and their associated 

species to adequately cope with increased climate-related stresses, and enhancing 

their recovery from climate-related disturbances, while continuing delivery of 

forest-derived values, goods, and services to citizens. A central purpose of 

restoration then is to reestablish the adaptive and resilient capacities of landscapes and ecosystems in each unique physiographic region. A second, related 

purpose is to restore the adaptive capacity and social resilience of associated 

human communities, while restoring ecological systems. The first purpose is 

served by restoring ecological patterns and processes that are in synchrony with 

the biota, geology, and climate. The second is served by enabling human communities to derive benefit from forest goods and services while conducting restoration 

and maintenance activities.

1

 The USDA Forest Service has defined restoration as “the process of assisting the recovery 

of an ecosystem that has been degraded, damaged, or destroyed. Ecological restoration 

focuses on reestablishing the composition, structure, pattern, and ecological processes 

necessary to facilitate terrestrial and aquatic ecosystem sustainability, resilience, and 

health under current and future conditions” (USDA FS 2013).

A central purpose 

of restoration is 

to reestablish 

the adaptive and 

resilient capacities 

of landscapes and 

ecosystems in each 

unique physiographic 

region.
7

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

The concept of restoration includes, but is larger than, the goal of reestablishing 

the historical range of variability (HRV). A process-oriented approach supports 

restoring ranges of conditions that have occurred in the past (e.g., eradicating 

invasive species and reconnecting fragmented habitats of threatened or endangered 

species), in environments where the future climate will strongly resemble the 

recent climate, and where the results are socially understood and acceptable. Where 

the future climate is not expected to resemble the recent climate, the objective of 

ecological restoration would be to create resilient forests and rangelands that are 

adapted to the future climate. This idea is captured in the related notion of future 

range of variability, or FRV, as coined by several authors (Binkley and Duncan 

2010, Hessburg et al. 2013, Keane et al. 2009, Moritz et al. 2011, Weins et al. 2012). 

In addition to being forward-looking, contemporary concepts of ecological restoration may emphasize social context and the connectivity and interactions among 

people, societies, and the biophysical elements of ecosystems. For some landscapes, 

it will simply be impossible and inadvisable to return them to prior conditions (Harris et al. 2006), while for others it may be well advised.

To effectively implement restoration goals across eastside mixed-conifer forests, managers can consider applying already completed assessments of conditions 

across the eastside landscape (e.g., the Interior Columbia Basin Ecosystem Management Project and Eastside Forest Ecosystem Health assessments), perhaps expanding on them, and then prioritizing the location and nature of treatments that would 

be most beneficial to ecosystems and to people. This will involve both regional and 

local landscape assessment. 

In some places, there may be a need to increase the pace and scale of restoration to address a variety of immediate threats—including fire, climate change, bark 

beetle infestations, and others—for the health of public forest ecosystems, watersheds, and natural-resource-dependent communities. However, for these efforts to 

be sustainable, both ecological and socioeconomic vantage points would be best 

considered in the context of regional and local landscape patterns and processes, 

because in the long run the natural system must support the social system.
8

GENERAL TECHNICAL REPORT PNW-GTR-897

Structure of This Report—

Where to Find Sections of Interest 

Overview of contents—This report progresses from a review of the relevant 

science to a presentation of management considerations. 

Chapter 2 discusses how MMC types fit within a regional coniferous mosaic. 

In this chapter, the reader will understand our definition of MMC forests, what 

forest types are typically included within this classification, and generally where 

they are located.

Chapter 3 presents ecological concepts that are foundational to landscape 

restoration. 

Chapter 4 explains and summarizes the detailed scientific information that constitutes our synthesis. We provide a large number of citations to guide the reader 

through the scientific literature. Major findings are also summarized in chapter 4. 

Appendix 3 is provided to complement chapters 4 and 5.

Chapter 5 is the core of this report, in which the reader will find relevant management concepts gleaned from the scientific literature. We also provide a list of 

considerations that can help guide a landscape evaluation process. This list arises 

from recent experiences of eastside land managers who have adopted a landscape 

perspective and are conducting landscape evaluations. Silvicultural options and 

innovations are discussed as they relate to landscape prescriptions and their 

component stand-level prescriptions. We also present ideas about adjustments 

that may help increase institutional capacity to implement the ideas contained in 

this report. We close this section with an overview of the socioeconomic conditions that underlie most land management decisions. 

Chapter 6 provides a brief discussion of the important institutional considerations that influence how these concepts might be implemented. This chapter also 

presents a summary discussion on the socioeconomic issues that are clearly in the 

foreground of any management strategy that seeks to restore lands and resources. 

Chapter 7 provides brief conclusions and summary thoughts about how our 

findings may be incorporated into land management and project-level plans. 
9

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Moist mixed-conifer (MMC) forests are diverse and cover a large area east of the 

crest of the Cascade Range in Oregon and Washington, where grand fir (Abies 

grandis (Douglas ex D. Don) Lindl.), white fir (Abies concolor (Gord. & Glend.) 

Lindl. ex Hildebr.), and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) are 

the potential late-successional (climax) tree species (fig. 3). These forests grow in 

environments that are subsets of the white fir–grand fir and Douglas-fir “series,” 

broad potential vegetation types used by Forest Service managers (Powell et al. 

2007, Simpson 2007) to characterize the land’s general ecological and vegetative 

capability. 

Depending upon the environment and local site climate, patches of MMC 

forest typically occur where the current vegetation (not necessarily the same as 

potential natural vegetation or the vegetation that would develop under historical 

fire regimes) is a mixture of shade-intolerant ponderosa pine (Pinus ponderosa

Chapter 2—Definition of Moist MixedConifer Forests and the Regional Context 

Figure 3—A mixed-conifer forest with overstory of ponderosa pine and patchy understory of post-1900 grand fir on the Sisters Ranger 

District, Deschutes National Forest, central Oregon.

Tom Spies
10

GENERAL TECHNICAL REPORT PNW-GTR-897

Lawson & C. Lawson) or western larch (Larix occidentalis Nutt.), and shadetolerant Douglas-fir, white or grand fir, and occasionally Engelmann spruce 

(Picea engelmannii Parry ex Engelm.), as in the moist grand fir zone of the Blue 

Mountains (Powell 2007). In areas of complex, dissected topography, the MMC 

forest intermingles with ponderosa pine and dry mixed-conifer types and wetter 

or cooler conifer types (fig. 4) (Powell et al. 2007, Simpson 2007). Other conifers 

occasionally associated with MMC forest include lodgepole pine (Pinus contorta

Douglas ex Loudon), western white pine (Pinus monticola Douglas ex D. Don), 

sugar pine (Pinus lambertiana Douglas), Shasta red fir (Abies magnifica A. Murray 

bis), Pacific silver fir (Abies amabilis (Douglas ex Loudon) Douglas ex Forbes), 

and western hemlock (Tsuga heterophylla (Raf.) Sarg.). Dry ponderosa pine and 

dry mixed-conifer conditions tend to occupy lower montane settings, ridgetops, 

and southern exposures, whereas MMC conditions typically occur in mid to upper 

montane settings; on northerly and sometimes southerly aspects, especially in the 

upper elevations; in valley bottoms; and in lower headwall positions.

The focus of this report is not so much about forests of a particular moisture 

class, but mixed-conifer forests where fire exclusion has altered forest composition, 

structure, and function from their historical range of variability. Wetter mixedconifer forests with longer fire return intervals may also have restoration needs, 

but these typically are not associated with changed fire regimes and thus are not 

examined in this report. The historical vegetation of MMC forest was controlled 

by frequent to moderately frequent fires (<20 to 50 years) that burned with mixed 

severity, containing both low- and high-severity patches. In most parts of the MMC 

forest, this fire frequency has been suspended, and disturbance regimes have been 

altered through a combination of historical drivers including grazing, loss of Native 

American fire ignitions, and active fire suppression. Consequently, the current 

MMC forest vegetation contains a significantly greater component of shade-tolerant 

tree species (e.g., white or grand fir or understory Douglas-fir) than occurred in the 

historical vegetation. Under historical or more fire- and drought-resilient states, 

these shade-tolerant species would have been less common in the understory in 

many areas, and large fire-resilient ponderosa pine, Douglas-fir, and western larch 

would have dominated the canopy layer. See appendix 3 for additional information 

about the variety of historical forest conditions that occurred in the Blue Mountains 

forest province early in the 20th century. Data are adapted from the Interior Columbia Basin Assessment (Hessburg et al. 1999a, 2000a).

Dry mixed-conifer and ponderosa pine sites (ponderosa pine series, or drier 

grand-fir/white or Douglas-fir subseries) typically experienced frequent fire return 

intervals (10 to 25 years), and exhibited a relatively open forest structure. Wetter 
11

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 4—Dry mixed-conifer and pine-oak, grading into moist mixed-conifer in a drainage, 

Columbia River Gorge, near Rowena, Oregon. 

Miles Hemstrom
12

GENERAL TECHNICAL REPORT PNW-GTR-897

and cooler mixed-conifer sites experienced longer fire return intervals (>50 years), 

and greater frequency of higher severity fire, and would have had a component of 

older shade-tolerant trees in the overstory, with dense areas of multistoried forest. 

Because few detailed fire history studies exist for the mixed-conifer forest in general, we use potential vegetation types (PVTs, see discussion below) as a surrogate 

for the fire regime and the degree to which mixed-conifer forests have departed in 

terms of composition and structure. These potential natural vegetation types, which 

include both series and approximations of subseries (e.g., dry, dry-moist, moist, and 

moist to wet variants of grand, white, and Douglas-fir series) can be a starting place 

for identifying the environments and locations of MMC forest (table 1). The PVTs 

used by managers (e.g., series, subseries, and plant associations) are often the best 

available source of local information, but are only an approximate surrogate for the 

fire regime of a site or local landscape. Figure 5 illustrates the continuum of forest 

types found along an elevational gradient on the east side of the Cascade Range and 

the relationship of forest type to general fire regimes.

Table 1—Area of major forest potential vegetation types in eastern Oregon and Washington 

All Federal lands

ownerships Wilderness Other Total Nonfederal

Hectares

Potential vegetation type:

Douglas-fir (dry) 1 818 129 57 050 740 450 797 500 1, 020 629

Grand fir/mixed conifer (cool/moist) 1 654 634 169 229 929 871 1 099 100 555 534

Grand fir (warm/dry) 433 195 24 283 335 693 359 977 73 218

Mixed conifer (cold/dry) 98 149 3056 73 966 77 022 21 127

Mixed conifer (dry) 1 096 662 15 495 442 618 458 114 638 548

Lodgepole pine 180 526 1646 114 442 116 087 64 439

Mountain hemlock 505 756 171 993 225 136 397 129 108 627

Pacific silver fir 172 084 59 154 84 780 143 934 28 150

Ponderosa pine 1 804 724 10 645 1 040 868 1 051 514 753 210

Subalpine fir 616 773 172 152 343 853 516 005 100 768

Western hemlock 304 794 10 214 180 064 190 278 114 516

Other potential vegetation types 18 675 361 6 136 634 12 538 727

 Total 27 360 787 11 343 294 16 017 493

Source: the Integrated Landscape Assessment Project.
13

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Annual precipitation (inches)

145 ~60 ~40 10 Elevation

Alpine

Fire severity

High

Mixed

Low

Fire interval (years)

<20

20–40

>40

Subalpine/

mountain

hemlock

Wet

mixed

conifer

Moist

mixed

conifer

Dry

mixed

conifer

Ponderosa pine Juniper woodland

Idealized PVT distribution

East slope, Oregon Cascades

Figure 5—Continuum of forest types found along an elevational gradient on the east side of 

the Cascade Range and the relationship of forest type to general fire regimes. PVT = potential 

vegetation type.

Variation in slope, topographic position, and landscape context can create a 

high degree of variation in fire regimes within the same PVT. For example, for a 

given PVT, areas with steep or concave slopes often experience more high-severity 

fire than gentler and more convex slopes. Likewise, MMC PVT patches embedded 

within large dry forest patches or adjacent to grass or shrub patches may experience 

a higher fire frequency than they would if they were embedded in MMC forest. 

Context matters, and is critical to interpreting the native fire regime. Final determination of MMC forest for restoration purposes should be based on landscape 

context, local environment, and disturbance history. Figure 6 provides a conceptual 

model of the complex ecological setting in which we find MMC forests. There are 

many biological and physical conditions that will influence what kind of vegetation 

is found at a site. 

Variation in slope, 

topographic position, 

and landscape context 

can create a high 

degree of variation 

in fire regimes within 

the same potential 

vegetation type. 
14

GENERAL TECHNICAL REPORT PNW-GTR-897

Figure 6—Conceptual model of the complex ecological setting of moist mixed-conifer forests. 

Climate-Soil-Topography

Landscape Context

How to Think About Mixed-Conifer Forests

More than structure and potential vegetation type at a site

States Processes

Succession

Competition

Growth

Dispersal

Structure

Composition Disturbance

Fire Water

Pathogens

Seeds

The MMC type is widely distributed across the east side (fig. 7) occupying 

particular environments and elevations along the east slope of the Cascade Range 

and large patches within the northern and central portions of the Blue Mountains. 

It often is sandwiched between the drier mixed-conifer and pine types and cooler 

and wetter mixed-conifer types. Figure 7 is intended to give a general depiction of 

the distribution of MMC forest. No standard, peer-reviewed maps of dry, moist, or 

wet PVTs exist for the entire region. See “Ecological Composition, Patterns, and 

Processes Prior to Euro-American Settlement (Before About 1850)” in chapter 4 for 

more details on sources of regional information and details on vegetation in general. 
15

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 7—Map of selected potential vegetation types that support mixed-conifer forests in eastern Oregon and 

Washington, using data from the Integrated Landscape Assessment Project (Pacific Northwest Research Station 

and Oregon State University). 

National forests of Oregon and Washington

Wenaha River watershed

Selected forested potential vegetation groups

Cool/wet conifer

Dry mixed conifer

Dry pine

Moist mixed conifer

0 20 40 80 120 Miles

o
16

GENERAL TECHNICAL REPORT PNW-GTR-897
17

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Restoration of ecological processes and patterns requires a multi-scale spatial and 

temporal perspective. Historically, the forests in eastern Oregon and Washington 

were diverse and complex in their species composition and structure (e.g., tree 

sizes, ages, density, layering, clumpiness). These patterns influenced the frequency, 

severity, and spatial extent of native insect, disease, wildfire, and abiotic disturbance processes such that signature “disturbance regimes” were apparent. However, 

a century or more of management has significantly altered patterns of structure and 

composition, and as a direct consequence, the associated disturbance regimes are 

highly altered as well. Figure 8 illustrates the large disparity in historical vs. current 

species composition and structure of forests in eastern Oregon and Washington.

Moist mixed-conifer (MMC) forests were and continue to be hierarchically 

structured systems with complex interactions between spatial scales. Part of what 

concerns us today is uncertainty driven by these cross-scale disturbance interactions. For example, very large wildfires, insect outbreaks, and changes in winter 

Chapter 3—Ecological Principles of 

Restoration and Landscapes

Changes in Structure and Composition

Diameter Distribution

30

20

10

0

60

40

20

0

White fir (n = 100) Dry Moist

Ponderosa pine (n = 1,347)

Historical Current

Douglas-fir (n = 269)

White fir

Ponderosa pine

Douglas-fir

200

160

120

80

40

0

Small Large Small Large

Number of trees

Density (trees/hectare)

60

40

20

0

30

20

10

0

60

40

20

0

40 percent large trees 7 percent large trees 10 percent large trees

White fir

Ponderosa pine

Douglas-fir

Small Large

200

150

100

50

0

4

3

2

1

0

15

10

5

0

Figure 8—Disparity in historical vs. current species composition and structure of forests in eastern Oregon and Washington.
18

GENERAL TECHNICAL REPORT PNW-GTR-897

snowpack and hydrology occurring at a regional scale threaten to alter meso-scale 

patterns and disturbance processes of local landscapes. Simply working at mesoscale (local landscapes, e.g., watersheds and subwatersheds) does not address these 

concerns. The answer lies in regional- or ecoregional-scale solutions.

At a meso-scale, patterns of forest structure and composition emerge, which are 

primarily maintained by interactions among environments, topography, weather, 

soils, geomorphology, and disturbances. But other broader and finer scale patterns 

also exist, and these are also influential to maintaining and changing meso-scale 

vegetation patterns over space and through time.

Forest ecosystem responses to disturbances or weather changes are often 

nonlinear, or involve complex feedback loops or time lags, particularly when we 

allow for longer observation periods. Thus, some interactions are relatively more 

unpredictable and may not manifest in any sort of change in the short term, until 

some kind of threshold is reached (Malamud et al 1998, Moritz et al. 2013, Peterson 

2002). The challenge for scientists and managers seeking to restore landscape 

resilience is to develop a better understanding of ecological complexity that can 

more readily be translated into practical strategies for restoration.

Our review of recent theory, observation, and understanding in the field of 

landscape ecology shows it is critical to consider long-term spatial and temporal 

phenomena prior to drawing conclusions or developing simplified decision rules 

based solely on temporally short or narrow geographic observation windows.

The Concept of Resilience

The resilience of current and future forest ecosystems is a major concern of land 

managers today. The concept of resilience promises a robust alternative to management goals based on static conditions or simple applications of the historical range 

of variability (HRV). However, resilience is not an easily defined concept in a 

practical sense (Gunderson 2000). Furthermore, operational metrics of resilience 

have received little attention to date (Carpenter et al. 2001). To become more 

operational, resilience must be defined in terms of specific system attributes and 

in relation to specific disturbances or perturbations. It is important to understand 

that resilience is a relative term and is constrained by space and especially time. 

Eventually change will be significant enough that a previously resilient system will 

reset itself into a new state. Thus, some bounding of space and time is necessary to 

define resilient states.

Forest ecosystem 

responses to 

disturbances or 

weather changes 

are often nonlinear, 

or involve complex 

feedback loops or time 

lags, particularly when 

we allow for longer 

observation periods. 

The concept of 

resilience promises 

a robust alternative 

to management 

goals based on static 

conditions or simple 

applications of the 

historical range 

of variability. 
19

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Folke (2006) and Gunderson (2000) have identified three conceptual domains 

of resilience: (1) engineering resilience, which focuses on recovery or return time 

to a stable equilibrium (e.g., return to a particular forest structure or composition); 

(2) ecological resilience, which focuses on maintaining function and persistence 

with multiple equilibria (e.g., HRV); and (3) socioecological resilience, which 

focuses on reorganization, adaptive capacity, and multiscale interactions among the 

many community members, stakeholders, and responsible government organizations that have an interest in the outcome of land management. Although we focus 

mainly on ecological resilience in this report, we acknowledge that the ecological system is imbedded in a socioeconomic system that interacts with ecological 

systems. 

The degree of alteration of an ecosystem and its dynamics (patterns of change 

over time and space) must be understood before we can consider if and how the 

system can be restored (fig. 9). 

Ecosystem Resilience

Pre-1850

conditions

(fire, insects,

disease) 

Inertia

Elasticity

Composite

of ecosystem

condition

Time 

Logging, 

fire exclusion, 

grazing, insects, etc.

Current condition

(changes in forest

structure and species

composition)

Future forest

condition after

restoration

Restoration 

efforts

Figure 9—Ball and cup heuristic of ecosystem stability (adapted from Gunderson 2000). Valleys represent the boundaries in which 

ecosystems are coping with disturbances, balls represent the ecosystem, and arrows represent disturbances. Some disturbances push 

the system out of a past “stable” state into a different ecosystem condition. The influences of inertia and elasticity are indicated in 

the diagram.
20

GENERAL TECHNICAL REPORT PNW-GTR-897

Westman (1978) suggested five characteristics that depict the potential resilience of a system: 

Inertia: The resistance of a system to disturbance. 

Elasticity: The speed with which a system returns after disturbance.

Amplitude: A measure of how far a system can be moved from a previous state 

and still return.

Hysteresis: The lagging of an effect behind its cause, such as delayed response of 

the system to a disturbance.

Malleability: The difference between the pre- and postdisturbance conditions. The 

greater or lesser the malleability, the lesser or greater will be the system’s resilience.

These technical terms from systems analysis illustrate the complexity of system 

responses to change and the challenge of restoring dynamic systems. The characteristics of resilience described here are not all measured with equal ease; some may 

simply be immeasurable in a short period because of a lack of historical data or 

reliable ecosystem models (Westman 1978). Given these limitations on data availability and the overall understanding of ecosystem interactions, we are reminded 

of a compelling need to employ an adaptive management approach in both research 

and monitoring, where we can track the results of management efforts and follow 

disturbances and recovery efforts over a long term. This would give managers the 

ability to inform subsequent management decisions with what was learned from 

previous management decisions and thus make appropriate adjustments. It also suggests the value and need for ecosystem models and tools that can include consideration and measurement of both inertia and resilience. Early versions of these tools 

have given us a better understanding of the complex dynamics of forest ecosystems 

and, in turn, how we can craft management strategies to achieve desired outcomes. 

In short, management for ecosystem resilience necessitates iterative steps to allow 

for adjustments at each juncture of trial and learning.

Resilience does not always result in desirable conditions on the land (Folke 

2006). Degraded and nonnative vegetation can also be resilient in its own way; e.g., 

landscapes dominated by cheatgrass (Bromus tectorum L.), which is generally considered undesirable, can be resilient in the face of restoration efforts by land managers. In this example, managers have experienced significant difficulties attempting 

to restore sagebrush steppe ecosystems invaded by cheatgrass (Chambers et al. 

2009, D’Antonio et al. 2009). 
21

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Landscapes often have considerable inertia because of alterations of pattern 

and process after more than a century of human activity. For example, Wallin et al. 

(1994) found that landscape patterns generated by past forest management or disturbance can take decades or centuries to restore (see also Heinselman 1973). Hysteresis 

(in a large dose) can operate in altered landscapes to create undesirable resilience or a 

delay in desired response to management. For example, the widespread accumulation 

of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and, to a lesser degree, grand 

fir (Abies grandis (Douglas ex D. Don) Lindl.) across many eastside landscapes now 

means that disturbance patches created by management or wildfire are more likely to 

regenerate to Douglas-fir and grand fir than they would have in the recent past. These 

relations can create significant challenges in executing successful restoration because 

of the large scale of the effect.

Ecological Principles for Landscape Planning 

and Management

Our perspective on the scientific principles underlying restoration of landscape 

resilience in eastside landscapes is based on three central ideas: (1) the biophysical 

environment (i.e., vegetation, climate, geology, and topography) and disturbances 

interact to control system behavior at several key spatial and temporal scales; (2) 

Euro-American activities have altered these ecological interactions and reduced 

landscape resilience; and (3) increasing resilience of desired conditions requires 

management actions that restore processes and patterns at these key scales. Without 

a broad geographic and ecosystem perspective that includes the past, present, and 

future role of humans and the climate, it will be impossible to restore resilient forests 

across a wide range of ecoregions and landscapes. Such a systems view should 

enable more effective application of treatments to meet restoration or resilience goals. 

We use the terms local and regional to describe landscapes. We define local 

landscapes as variably sized areas, typically ranging in size from one to several 

subwatersheds (hydrologic unit code [HUC] 6 or 12-digit watersheds) (Sieber et al. 

1987) (see also the National Hydrography Dataset at http://nhd.usgs.gov/), or 

a watershed (HUC 5 or 10-digit watershed). These subwatersheds collectively 

reside in a single ecological subregion (sensu Hessburg et al. 2000a), and exhibit 

characteristic patchworks of successional stages and topography consistent with 

the climate, biota, physical processes, and disturbance regimes of that subregion. 

Subwatersheds (i.e., HUC level 6) typically range in size from about 10,000 to 

40,000 ac (4050 to 16 200 ha), but larger and smaller subwatersheds also occur. 

We define a regional landscape as the complete collection of all local landscapes 

that comprise an ecological subregion. 
22

GENERAL TECHNICAL REPORT PNW-GTR-897

We define (local or regional) landscape resilience as the capacity of the ecosystems to absorb disturbance and climate change while reorganizing and changing but 

essentially retaining the same function, structure, identity, and feedbacks (adapted 

from Walker et al. 2004). Resilient landscapes maintain a dynamic range of species, 

vegetation patterns, and patch size distributions (broad- or meso-scale) that emerge 

under the constraints of the climate, geology, disturbance regimes, and biota of the 

area. 

In this chapter, we outline eight core ecological principles that are foundational 

to restoring eastside forests, including MMC forests. We expand on these in later 

chapters; however, our aim here is to highlight key ideas that motivate our thinking.

Physical and biological elements of an ecosystem interweave, creating distinctive patterns on a landscape. Climate, interacting with vegetation, disturbance, 

topography, soils, and geomorphology created domains of ecosystem behavior at 

local and regional landscape scales. During every historical climate period, a range 

of patterns and patch sizes of forest successional stages likely emerged. This emergent natural phenomenon is referred to as the natural range of variation (NRV), 

also referred to as the HRV. As the climate shifted, so did the NRV. The notion of 

a static NRV is a common misperception and provides a misleading objective for 

land managers. It does not exist. Prolonged periods of warming or cooling, wetting 

or drying, or combinations of these have occurred repeatedly over time. Whenever 

these changes have happened, they have pushed the NRV in new directions. But 

sudden and extensive shifts in the NRV were typically constrained, except under 

the most extreme climatic circumstances, by the lagged landscape memory encoded 

in existing patterns of living and dead vegetation. This is the quality of a natural 

system that we represent as landscape resilience. 

Vegetation dynamics and fire regimes of MMC forests were and are among the 

most variable. In the historical forest, this forest type exhibited low-, mixed-, and 

high-severity fires; the amount of each severity type varied with the climate regime, 

and by physiographic region. Patterns of vegetation structure and composition and 

fire frequency and severity changed gradually across landscapes with variation in 

climate and the impacts of settlement and early management. But before management, fire regimes of MMC forests were variable, depending on topography and 

ecoregion. In some locations, fires occurred relatively frequently (every 10 to 30 

years), in others, fire frequency was more variable (25 to 75 years). In the former, 

fire severity would have been primarily low- and mixed-severity, with surface fire 

effects dominating. In the latter case, fire severity would be primarily mixed- and 

high-severity, with active and passive crown fire effects dominating. In some 

ecoregions, the fire regimes and tree composition of the dry ponderosa pine, dry 

We are motivated by 

eight core ecological 

principles that are 

foundational to 

restoring eastside 

forests, including 

moist mixed-conifer 

forests. 
23

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

mixed conifer, and MMC types were quite similar and there were no clear lines of 

demarcation. In others, the differences in these types in terms of aspect orientation, 

tree density, layering, and species mixes were pronounced. With the advent of fire 

suppression, understories of the ponderosa pine (Pinus ponderosa Lawson & C. 

Lawson) and dry mixed-conifer forests were in-filled largely by ponderosa pine 

and shade intolerant Douglas-fir, respectively, but the MMC forests were in-filled 

by grand or white fir (Abies concolor (Gord. & Glend.) Lindl. ex Hildebr.) and 

Douglas-fir. Grand fir and Douglas-fir understories may have been transient in some 

historical MMC forests: if they got established during a period without fires, they 

may or may not have been eliminated by subsequent frequent low-severity fires. 

During longer intervals between fires, significant fuel ladders may have developed 

and mixed-severity fire effects would have been typical. On wet mixed-conifer 

forest sites, shade-tolerant tree species were persistent and fire intervals were long 

enough to allow development of old shade-tolerant trees and larger patches of dense 

multilayered forests within stands and landscapes.

Eastside forest patterns and influential processes are constantly shifting over 

space and time. However, topography, soils, and elevation constrain these patterns and provide a relatively simple template for understanding and managing 

landscapes for them. As a first approximation, the topographic and edaphic patterns 

of landscapes provide a natural template for pattern modification and restoration. 

For example, spatial patterns of ridges and valleys, and north- and south-facing 

aspects, strongly represent characteristic patterns and size distributions of historical 

vegetation patches. North-facing aspects and valley bottoms historically supported 

the densest and most complex forest structures, and when fires occurred, these sites 

experienced more severe fire behavior than south-facing aspects and ridges, owing 

to site climate and growing season factors. The same is true today. In contrast, 

south-facing aspects and ridges tended to burn more often and less severely than 

north-facing aspects and valleys. Wildfire conditions in summer were typically 

drier and fine fuels were conditioned for burning, even during average summer 

burn conditions. 

Ecosystems and their component parts are organized in an interactive, hierarchical arrangement. Processes associated with the regional landscape exert 

a measure of control over patch dynamics of local landscapes, and ultimately, 

some fine-scale patterns and processes within patches. For this reason, no forest 

type, its disturbance regime, or its variation may be thought of in isolation. Some 

landscapes are dominated by one topographic aspect (e.g., north- or south-facing); 

consequently, vegetation on minor aspects may be different than would otherwise 

be expected from knowledge of their site conditions alone. In landscapes with more 
24

GENERAL TECHNICAL REPORT PNW-GTR-897

southerly aspects and ridges, corresponding northerly aspects typically also see 

more frequent fires and lower than typical severity. Knowledge of specific context 

and scale can help guide patch-level decisions. 

Postsettlement human activities have resulted in increasingly homogenized 

forests and, in turn, significant changes in the scope and effects of natural 

disturbances. Widespread human-caused changes to vegetation structure, composition, and fuelbeds have created more homogenized conditions in the MMC forest, 

generally in the form of large, dense, and multilayered patches of intermediate-aged 

fire-intolerant tree species. These changes have increased the area and frequency of 

large, high-severity fire patches, and the extent and frequency of other biotic disturbances (e.g., bark beetle and budworm outbreaks). The changes have also substantially altered the resilience mechanisms associated with the native forests. Climate 

and the characteristic disturbance regimes and landscape patterns regulated the 

composition, frequency, and size of the largest patches. Prior to Euro-American 

settlement, local and regional landscapes had developed over a period long enough 

for coarse and fine-scale patterns and species composition to be in some degree of 

synchrony with their physical environments and the climate system. Much of this 

synchrony has been lost through the cumulative effects of relatively recent human 

activities on the landscape. Current and future fire regimes and landscape patterns 

are on new trajectories trending away from a previously established resilience. To 

restore this coupling between patterns and processes (wildfire, insects, pathogens, 

and weather), forest structure, composition, and landscape patterns must be modified at a scale that is consistent with the scale of the current vulnerabilities. Pattern 

modifications should be consistent with the inherent disturbance regimes of large 

landscapes and forest types, and with the climate regime. 

Rare ecological events can have a disproportionately large effect on ecosystems. Rare, large-scale events (disturbance, climatic, biotic, geologic) can 

significantly affect future landscape dynamics, especially if their frequency, size, 

or severity are unprecedented for the climatic, biotic, and environmental conditions. Large wildfires, dramatic climatic extremes, rapid changes in plant and 

animal species distributions, and large insect outbreaks are examples of natural 

and human-caused events that are rare but can have a strong and lasting effect on 

future landscape patterns and processes. Typically, these events are hard to predict 

and some are outside the control of managers. Nevertheless, they shape current 

landscapes and can be anticipated when developing and gaging the extent and 

timing of risk mitigation strategies. To a modest degree, managers can, through 

cumulative smaller actions, prepare landscapes in a manner that reduces the likelihood or impact of these large and rare events. However, to be effective, the timing 

and extent of the actions must match the level of inertia that supports the large-scale 
25

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

events. For example, large areas of eastern Oregon and Washington are susceptible 

to chronic western spruce budworm (Choristoneura occidentalis) infestation owing 

to the wide prevalence of Douglas-fir, grand fir, and white fir in large, dense, 

multilayered patches. Changing this situation would require the reduction in the 

prevalence, complex layering, and density of these host tree species over a very 

large area to match the scale of the vulnerability to this disturbance.

Resilience depends on ecological heterogeneity and varies with spatial and 

temporal scale. At no time were all patches of a landscape resistant to fires or 

other disturbances. At any given time, some patches within a landscape were 

always susceptible to insect attack, stand-replacing fires, pathogen infections, or a 

combination of these. In some ecoregions, as much as 25 to 35 percent of the forest 

had been recently burned by high-severity fire, and a significant area was in an 

early-seral condition (grass, shrub, or seedling/sapling) or was recently burned and 

recovering (e.g., see the tables in app. 3). This is how forest habitats with complex 

structure and age classes continuously emerged on the landscape and were retained 

despite ongoing disturbances. In other ecoregions, where surface fire effects 

stemming from low- and mixed-severity fires were clearly dominant, fine-scale 

patterns in forest composition, structure, and tree age created a fine-scale mosaic 

of susceptibility to disturbance. This is how forest habitats with fine-scale structure 

and age classes continuously emerged on this landscape. The interplay of fine- and 

coarse-scale drivers (e.g., disturbance, topography, soils, and microclimate) across 

the regional landscape created fine-, meso-, and coarse-scale forest habitats with 

complex structure and age classes. In this way, local and regional landscapes, but 

not all stands or patches, were resilient.

Completely natural or historical landscape patterns cannot be the goal for 

current and future climate and landscape conditions. However, the past (e.g., 

HRV) can be an important guide to creating resilient forests. Knowledge of how 

forests and landscapes changed in response to disturbances and climate variation 

in the past is valuable for providing future forests and landscapes that have desired 

ecological patterns and processes. Where human-driven changes (e.g., fire suppression, grazing, past logging) have significantly altered forests relative to HRV, it will 

take significant inputs of human energy (i.e., ecologically motivated management) 

to create desired landscape conditions. 

The size, diversity, and complexity of eastside mixed-conifer landscapes necessitate a prioritized approach to management. Though generalized, this concept, as 

well as those listed above, are critical to restoring resilience in these forests. These 

concepts have a strong ecological foundation, focus on restoring a more natural 

coupling of pattern and process, and can help managers create conditions that 
26

GENERAL TECHNICAL REPORT PNW-GTR-897

conserve options, are adaptable, and can be implemented with available skills and 

abilities common on the staff of a forest or district (or equivalent). Developing this 

characterization of a forest, although new to contemporary forest management, is 

not overly difficult and will enable a much more effective treatment strategy at the 

stand level where managers typically do their on-the-ground work.

Topography as a Template for Landscape Heterogeneity 

Previous research efforts have highlighted the predictive importance of topography (and more broadly, geomorphology) in landscape management (e.g., see 

Underwood et al. 2010). Studies and assessments from mixed-conifer forests 

(e.g., Hessburg et al. 2005, 2007; North et al. 2009; Taylor and Skinner 2003) 

have established that patterns of forest condition and fire behavior are strongly 

affected by topographic and physiographic features. Variability in soils also 

contributes to landscape heterogeneity, usually at a finer spatial scale. There 

are simple rules-of-thumb that can be gleaned from this work and applied to 

landscape management.

Simple partitioning of the landscape into basic topographic positions, 

such as drainage bottoms, ridgetops, or south- and north-facing slopes, is 

a straightforward method for parsing the forest into subunits with different 

inherent growth potential and disturbance regimes. Aspect patches of all sizes 

can be used to tailor treatments to the landscape; these can be readily generated in a geographical information system (GIS). There are now a number of 

easy-to-use GIS tools for doing this on any landscape using standard digital 

elevation model (DEM) data. The following provides a brief overview of some 

of the insights that topography provides.

South-facing aspects and ridges tended to burn more often and less 

severely than north-ridges, and fine fuels were typically conditioned for 

burning, even during average summer burn conditions. One can imagine that 

ridges, with their more exposed conditions and open grown forests, provided 

a rather elaborate network of natural fuel breaks owing to high lightning ignition frequency and limited fuel accumulations. This was typically not the case 

on north-facing aspects and in valleys, hence their reduced fire frequency. 

Although exceptions to these generalizations abound, landscape restoration 

can capitalize on these general tendencies without using a one-size-fits all 

approach. Instead, landscape restoration can apply a rule-of-thumb approach, 

as follows.

Simple partitioning 

of the landscape into 

basic topographic 

positions is a 

straightforward 

method for parsing the 

forest into subunits 

with different inherent 

growth potential and 

disturbance regimes.
27

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Managing south-facing aspects and ridgelines. In application, southerly aspects and ridges 

could be managed to support fire-tolerant species in clumped and gapped distributions by: (1) 

favoring very large-, large-, and medium-sized trees so that they occupied, e.g., 40 to 50 percent 

of the tree cover in the majority of these patches, and represented, e.g., 50 to 60 percent of their 

total area; (2) stocking to support a dominance of surface fire behavior stemming from lowand mixed-severity fires, and tree densities that support endemic but not epidemic bark beetle 

populations (i.e., resulting in the mortality of only a few trees over time); (3) maintaining tree 

species composition that strongly discourages the spread and intensification of root diseases, 

while allowing their presence; and (4) maintaining stocking on south slopes and ridges by low 

and free thinning and similar methods, especially by prescribed burning at regular intervals. 

Size class and canopy cover dominance would certainly vary from place to place, but ranges 

of conditions could be calibrated from historical reconstructions and modified as needed by 

incorporating expected climate changes. Prescribed burning and thinning activities could 

discriminate against the most severe dwarf mistletoe infestations. This would adequately mimic 

historical fire influence, but allow some of the most ecologically beneficial aspects of dwarf 

mistletoe infestation. Where fire- and drought-tolerant species are not dominant on south slopes 

and ridges, managers can regenerate them using methods that are best adapted to local site 

conditions. 

Managing north aspects and valley bottoms. In application, north aspects and valley bottoms 

tend to support a mix of fire-tolerant and fire-intolerant tree species in relatively dense, often 

multilayered arrangements. Stocking can support surface and crown fire behavior stemming 

from mixed- and high- with occasional low-severity fires. Landscape patchiness of denser north 

aspect and valley bottom forest conditions can help constrain the frequency, severity, and duration of defoliator and bark beetle outbreaks. Ideal stocking on north slopes and valleys would 

reflect species compositions that encourage or allow the spread of root disease as a natural 

process; mixed fire-tolerant and fire-intolerant species compositions should adequately restrain 

the spread of root diseases while allowing ecologically beneficial fine-scale habitat and forage 

conditions stemming from root disease centers. Stocking on north slopes and valleys may be 

maintained by free selection thinning or similar methods, especially where density is quite high 

and layering is simple. Where fire-tolerant species are not present in north-facing slopes and 

valley bottom settings, they may be regenerated using methods that are adapted to local site 

conditions, depending on other local habitat constraints. Some patches may be dominated by 

drought- and fire-intolerant species without harm to the larger landscape. 

Forest types and their fire regimes are interconnected. Disturbance regimes and their variations in each forest type offered a regulating influence in adjacent but differing forest types. 

For this reason, no forest type and its disturbance regime and variation may be thought of in 

isolation. Some landscapes have significantly more north- or south-facing aspects than others;

(continued on next page)
28

GENERAL TECHNICAL REPORT PNW-GTR-897

(from page 27)

consequently, variations emerge that increase landscape complexity and these should be 

noted. In landscapes with more southerly aspects and ridges,north-facing aspects typically see more frequent fires and lower than typical severity. The converse is also true. 

These ideas can help shift the focus away from an overly simplistic topographically driven 

landscape template.

Figure 10 illustrates this intrinsic landscape pattern driven by topographic position 

with two photographs of Mission Peak on the Wenatchee National Forest. The photo from 

1934 shows very little tree growth on the south-facing slopes and ridgetops with dense 

forest on the north-facing slopes and drainage bottoms. Because of fire exclusion, the 

forests have filled in as shown by the 2010 photo. 

Figure 10—The Mission Peak area on the Okanogan-Wenatchee National Forest; a comparison between 

1934 and 2010 of forest density and structure. 

John Marshall
29

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Ecological Composition, Patterns, and Processes Prior 

to Euro-American Settlement (Before About 1850)

The mountains of Oregon and Washington exert strong orographic control on 

climate, vegetation, disturbance, and land use across the region. Steep precipitation 

and temperature gradients have a significant influence on the vegetation east of the 

Cascade Divide (Franklin and Dyrness 1988) (fig. 11). Moist mixed-conifer (MMC) 

forest patches frequently occur within a broader continuum of mixed-conifer forest 

types (fig. 12) and within topographic locations juxtaposed with mixed conifer 

or ponderosa pine vegetation types, or grassland and shrubland patches (fig. 13) 

(Hessburg et al. 1999a, 2000b; Spies et al. 2006). This mosaic of landscape composition and physiognomic conditions can alter the disturbance regime as well as the 

functioning of these patches across broader spatial scales. For example, the frequent 

fire regimes of grassland and shrubland influence adjacent forests by increasing 

their fire frequency. This occurs because grass and shrub patches often function 

as “conveyor belts,” readily spreading wildfire to adjacent patches. Likewise, dry 

mixed-conifer patches that experience frequent surface fires can also influence 

adjacent MMC patches. However, when MMC forest is surrounded by cold or wet 

forest types, the fire regime may be influenced by this context; and fires may tend 

to be less frequent and more severe.

Chapter 4—Scientific Foundations

Figure 11—At the regional scale, the moisture gradient is structured by large-scale topographic features, such as the Cascade Mountains, 

and a prevailing south-southwest storm track.

B. Nguyen
30

GENERAL TECHNICAL REPORT PNW-GTR-897

Figure 12—A simple schematic illustrating a typical landscape gradient of different forms of mixed conifer, from the dry type through 

the moist types to the wet types. 

Figure 13—A common gradient of grasslands/shrublands to dry forests and moist forests. Blue Mountains near Pendleton, Oregon. 

Miles Hemstrom Illustration by Stevie Ruda
31

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Where Is the MMC Forest Located?

No standardized, peer-reviewed maps of the potential vegetation subseries covering 

the MMC forest are published for the entire region. The Region 6 Area Ecology 

Program has developed plant association classifications and maps for individual 

subregion ecology areas, but the names and environmental conditions of the plant 

associations differ. Currently the region is using the vegetation classification 

represented in the Integrated Landscape Assessment Program (a partnership jointly 

managed by the Forest Service Pacific Northwest Research Station and Oregon 

State University’s Institute of Natural Resources) for defining MMC forest distribution and abundance (fig. 7, table 2). The map we presented is intended solely for the 

purpose of initial regional-scale planning and analysis and has limited spatial accuracy for project planning. Local classifications and maps that are spatially accurate 

at a patch scale are more appropriate for defining the distribution of the MMC forest 

for project level planning and management.

Other classification strategies also exist (e.g., Henderson et al. 2011, Simpson 

2007) for vegetation zones that have resulted in different depictions of this forest 

type across the region. Confounding this issue, national forests often have their own 

local maps of potential vegetation types (PVTs) that they use for management, and 

the scale of these maps varies from forest to forest. These maps do not correspond 

to the regional maps shown here. We suggest that any future regionwide strategy 

for MMC forest be underpinned with a single map that uses a regionally coherent 

classification standard and mapping protocol. The map would accurately identify 

the major areas that support the MMC type, and its relation to other types. This 

regional map would enable cross-forest data sharing and landscape assessment and 

management coordination. Local forest-level maps would then be needed to estimate departure from historical dynamic and threats to forest resilience. 

Mixed-Conifer Plant Association Classification

The plant associations of series associated with mixed-conifer forest can be 

placed into different moisture/fire regime groups using published and unpublished information (table 2). We present these as a first approximation for 

defining the occurrence of different mixed-conifer-disturbance regime types 

and aid to communication. As stated elsewhere, potential vegetation types 

(e.g., series, subseries, and associations) are only approximate indicators of 

fire regime, a concept which is best applied at landscapes scales (larger areas 

that are mosaics of local climate, topography, soils and vegetation). 

(continued on next page)

Local classifications 

and maps that are 

spatially accurate at a 

patch scale are more 

appropriate for defining 

the distribution of the 

moist mixed-conifer 

forest for project 

level planning and 

management.
32

GENERAL TECHNICAL REPORT PNW-GTR-897

(from page 31)

We grouped plant associations of the grand fir, Douglas-fir, and Shasta red 

fir (Abies magnifica A. Murray bis) series into subgroups based on moisture 

and historical fire regime: dry-low severity, moist-dry-low- to mixed-severity, 

moist-mixed severity, and moist to wet-high-severity (table 2). Associations in 

the subalpine fir and Shasta red fir series were included if ponderosa pine is 

an overstory component in the series or if plant association guides mentioned 

that low-severity fires were part of the historical fire regime. We assigned 

plant associations to a mixed-conifer moisture-fire regime group based on 

published information and expert opinion about the historical disturbance 

regime, environmental setting, and species composition. Plant associations in 

dry environments where historical fire regimes were predominately low severity and ponderosa pine was common in both the overstory and understory 

were classified as dry mixed-conifer.

Plant associations were classified as MMC forest if the following conditions were met: (1) mixed-severity fire regime; (2) intermediate environmental 

setting; and (3) Douglas-fir or grand fir are the most common understory tree 

species and are co-dominant in the overstory with ponderosa pine or other 

early-seral dominant, or those tree species are predicted to be dominant in the 

overstory and understory community based on the primary indicator plant 

species. Plant associations that could not be classified as dry or moist because 

of broad variability in historical disturbance regimes and species composition were classified as moist-dry. We expect the variability in the moist-dry 

group represents associations where dry and MMC forest intermingle on the 

landscape. The moist to wet classification was given to all plant associations 

with an infrequent, high-severity fire regime and species composition that 

were inconsistent with our definition of eastside mixed-conifer forest. Some of 

these associations would be classified as “moist” in some subregions but their 

historical fire regimes are still dominated by high-severity fire at relatively 

longer intervals. In these latter associations, ponderosa pine was usually 

absent in all strata; early-seral species including lodgepole pine, Douglas-fir 

and western larch were often even-aged; and shade-tolerant fire-intolerant 

species were common in the overstory. Plant associations in these moist to 

wet environments may still merit restoration due to past timber management 

activities, but fire does not play the same role as it does in dry and MMC 

forests, and it is unlikely that fire exclusion has modified structure, composition in these wetter types. 
33

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 2—Mixed-conifer plant associations grouped by moisture and approximate fire regime (app. 2) 

Vegetation series/

National forest (NF)/regiona plant association Extentb Species compositionc SourcedDry with low-severity fire—characterized by low-severity fires and relatively short return intervals of less than 35 years. Natural fire regimes in order of prevalence are I, III A, III B, and IV A.Blue and Ochoco Mountains Douglas-fir/elk sedge Widespread PSME, PIPO, ABGR Johnson and Clausnitzer 1992Blue and Ochoco Mountains Grand fir/elk sedge Widespread ABGR, PIPO, PSME Johnson and Clausnitzer 1992Blue and Ochoco Mountains Grand fir/pinegrass Widespread ABGR, PIPO, PSME, LAOC, PICO Johnson and Clausnitzer 1992

Johnson and Simon 1987

Blue and Ochoco Mountains Grand fir/birchleaf spirea Intermediate ABGR, PSME, LAOC, PIPO Johnson and Clausnitzer 1992Blue and Ochoco Mountains Douglas-fir/mountain snowberry Minor PSME, PIPO, JUOC Johnson and Clausnitzer 1992

Johnson and Simon 1987

Blue and Ochoco Mountains Douglas-fir/common snowberry Widespread PSME, PIPO, LAOC, JUOC Johnson and Clausnitzer 1992

Johnson and Simon 1987

Blue and Ochoco Mountains Douglas-fir/pinegrass Widespread PSME, PIPO, ABGR Johnson and Clausnitzer 1992

Johnson and Simon 1987

Blue and Ochoco Mountains Douglas-fir/birchleaf spirea Intermediate PSME,PIPO Johnson and Simon 1987Colville NF Ponderosa pine–Douglas-fir/bluebunch Minor PIPO, PSME Williams et al. 1995

wheatgrass

Colville NF Douglas-fir/snowberry Intermediate PSME, PIPO, LAOC Williams et al. 1995Colville NF Douglas-fir/mountain snowberry Minor PSME, PIPO, LAOC Williams et al. 1995Colville NF Douglas-fir/pinegrass Widespread PSME, LAOC, PIPO Williams et al. 1995Deschutes, Mount Hood NFs Douglas-fir/bitterbrush Intermediate PIPO, PSME, CADE, JUOC Simpson 2007Deschutes, Mount Hood NFs Douglas-fir/greenleaf manzanita Intermediate PIPO, PSME, CADE Simpson 2007Fremont-Winema, Mount Hood NFs Douglas-fir/common snowberry Intermediate PSME, PIPO, QUGA, JUOC Simpson 2007Fremont-Winema, Mount Hood NFs Douglas-fir/mahala mat Intermediate PIPO, PSME, CADE Simpson 2007Fremont-Winema, Deschutes, Grand fir/pinegrass Minor (in PIPO, PSME, ABGR Simpson 2007

Mount Hood NFs east Cascades)

Fremont-Winema, Deschutes, Grand fir/common snowberry Widespread PIPO, ABGR, PSME Simpson 2007

Mount Hood NFs

Fremont-Winema, Deschutes, Grand fir/greenleaf manzanita Widespread PIPO, ABGR, PICO Simpson 2007

Mount Hood NFs

Fremont-Winema NF Grand fir/wooly wyethia Minor PIPO, ABGR, PICO Simpson 2007

Fremont-Winema NF Grand fir/mahala mat Intermediate PIPO, ABGR, CADE, JUOC Simpson 2007Mount Hood NF Douglas-fir/elk sedge Widespread PIPO, PSME, QUGA, ABGR Topick et al. 1988

Mount Hood NF Douglas-fir/western fescue Intermediate PSME, PIPO, ABGR, QUGA Topick et al. 1988Mount Hood NF Douglas-fir/snowberry Intermediate PIPO, PSME, ABGR Topick et al. 1988Mount Hood NF Douglas-fir/pinemat manzanita Minor PIPO, PSME, ABGR Topick et al. 1988Mount Hood NF Grand fir/elk sedge Widespread PSME, ABGR, PIPO Topick et al. 1988Mount Hood NF Grand fir/snowberry Most widespread PSME, ABGR, PIPO Topick et al. 1988Okanogan NF Ponderosa pine–Douglas-fir/bluebunch Widespread PIPO, PSME Williams and Lillybridge 1983

wheatgrass
34

GENERAL TECHNICAL REPORT PNW-GTR-897 Table 2—Mixed-conifer plant associations grouped by moisture and approximate fire regime (app. 2) (continued) Vegetation series/ National forest (NF)/regiona plant association Extentb Species compositionc Sourced Okanogan NF Douglas-fir/pinegrass Most widespread PSME, LAOC, PIPO, PICO, POTR5 Williams and Lillybridge 1983 Okanogan NF Douglas-fir/bearberry Intermediate PSME, PICO, PIPO, LAOC Williams and Lillybridge 1983 Okanogan NF Douglas-fir/mountain snowberry Intermediate PSME, PIPO, LAOC Williams and Lillybridge 1983 Wenatchee NF Oregon white oak/bluebunch Minor QUGA, PIPO Lillybridge et al. 1995 wheatgrass Wenatchee NF Oregon white oak/pinegrass– Minor QUGA, PIPO, PSME Lillybridge et al. 1995 elk sedge Wenatchee NF Oregon white oak/California Minor QUGA, PIPO, PSME, POTR5 Lillybridge et al. 1995 hazel–common snowberry Wenatchee NF Ponderosa pine/pinegrass– Minor PIPO, PSME Lillybridge et al. 1995 bluebunch wheatgrass Wenatchee NF Ponderosa pine/bitterbrush– Intermediate PIPO, PSME Lillybridge et al. 1995 bluebunch wheatgrass

Wenatchee NF Douglas-fir/elk sedge Intermediate PSME, PIPO Lillybridge et al. 1995Wenatchee NF Douglas-fir/bitterbrush– Widespread PIPO, PSME Lillybridge et al. 1995

bluebunch wheatgrass

Wenatchee NF Douglas-fir/bitterbrush–pinegrass Widespread PIPO, PSME Lillybridge et al 1995Wenatchee NF Douglas-fir/bluebunch wheatgrass Widespread PSME, PIPO Lillybridge et al. 1995Wenatchee NF Douglas-fir/pinegrass– Intermediate PIPO, PSME Lillybridge et al. 1995

bluebunch wheatgrass

Wenatchee NF Douglas-fir/pinegrass widespread PSME, PIPO, PICO, LAOC Lillybridge et al. 1995Wenatchee NF Douglas-fir/snowberry– Intermediate PSME, PIPO Lillybridge et al. 1995

bluebunch wheatgrass

Wenatchee NF Douglas-fir/snowberry–pinegrass Widespread PSME, PIPO Lillybridge et al. 1995Wenatchee NF Douglas-fir/snowberry Widespread PSME, PIPO Lillybridge et al 1995Wenatchee NF Douglas-fir/mountain snowberry Intermediate PIPO, PSME Lillybridge et al. 1995Wenatchee NF Douglas-fir/shiny-leaf spirea–pinegrass Widespread PSME, PIPO Lillybridge et al. 1995Wenatchee NF Grand fir/pinegrass Most widespread PSME, PIPO, ABGR, PICO Lillybridge et al. 1995Wenatchee NF Grand fir/mountain snowberry Minor PSME, PIPO, ABGR Lillybridge et al. 1995Wenatchee NF Grand fir/pinemat manzanita Widespread PSME, PIPO, ABGR, PICO, LAOC Lillybridge et al. 1995Warm Springs Indian Reservation Ponderosa pine–Douglas-fir/bitterbrush Intermediate PSME, PIPO CADE Marsh et. al 1987Warm Springs Indian Reservation Ponderosa pine–Douglas-fir/ Widespread PIPO, PSME, CADE Marsh et. al 1987

bitterbrush-ceanothus

Warm Springs Indian Reservation Ponderosa pine–Douglas-fir/snowberry Intermediate PSME, PIPO CADE Marsh et. al 1987Warm Springs Indian Reservation Ponderosa pine–Douglas-fir/bitterbrush Intermediate PIPO, JUOC, QUGA Marsh et. al 1987

(Mutton)

Warm Springs Indian Reservation Ponderosa pine–Douglas-fir/snowberry Intermediate PSME, PIPO CADE Marsh et. al 1987

 (Mutton)
35

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 2—Mixed-conifer plant associations grouped by moisture and approximate fire regime (app. 2) (continued)

Vegetation series/

National forest (NF)/regiona plant association Extentb Species compositionc SourcedWarm Springs Indian Reservation Ponderosa pine–Douglas-fir/greenleaf Intermediate PSME, PIPO, CADE, QUGA Marsh et. al 1987

manzanita–ceanothus (Mutton)

Warm Springs Indian Reservation Ponderosa pine–Douglas-fir/snowberry Intermediate PSME, PIPO QUGA Marsh et. al 1987

 (Mutton)

Warm Springs Indian Reservation Ponderosa pine–Douglas-fir/prairie Intermediate PIPO, PSME, JUOC, QUGA Marsh et. al 1987

smoke avens–mule’s ears (Mutton)

Moist-dry with low- to mixed-severity fire—Characterized by low to moderate-severity fire with intervals intermediate between the dry and moist group. Large highseverity fires rarely occur. Natural fire regimes in order of prevalence are III A, III B, I, IIIC, and IV A.Blue and Ochoco Mountains Douglas-fir/oceanspray Intermediate PSME, PIPO Johnson and Clausnitzer 1992Blue and Ochoco Mountains Grand fir/grouse huckleberry Intermediate ABGR, LAOC, PSME, LAOC, Johnson and Clausnitzer 1992

PICO, PIPO

Blue and Ochoco MountainsWallowa-Snake Province Douglas-fir/Rocky Mountain maple– Intermediate PSME, PIPO Johnson and Simon 1987

mallow ninebark

Blue and Ochoco MountainsWallowa-Snake Province Douglas-fir/big huckleberry Intermediate PSME, PIPO, LAOC Johnson and Clausnitzer 1992

Johnson and Simon 1987

Blue and Ochoco Mountains; Douglas-fir/pinemat manzanita/ Minor PSME, PIMO, ABLA Johnson 2004

Strawberry Mountains elk sedge

Blue and Ochoco MountainsWallowa-Snake Province Douglas-fir /mallow ninebark Widespread PSME, PIPO, LAOC Johnson and Clausnitzer 1992

Colville National Forest Douglas-fir/ninebark Most widespread PSME, PIPO Williams et al. 1995Colville National Forest Douglas-fir/ninebark–twinflower Widespread PSME, LAOC, PIPO Williams et al. 1995Colville National Forest Douglas-fir/big huckleberry Intermediate PSME, LAOC, PICO Williams et al. 1995Colville National Forest Douglas-fir/dwarf huckleberry Minor PSME, PICO, LAOC,PIPO, PIEN Williams et al. 1995Colville National Forest Grand fir/ninebark Widespread PSME, LAOC, PIPO, ABGR Williams et al. 1995Colville National Forest Grand fir/dwarf huckleberry Minor PICO, PSME, LAOC, ABGR Williams et al. 1995Deschutes, Mount Hood NFs Douglas-fir/chinquapin Widespread PSME, PIPO, CADE, PILA Simpson 2007

Deschutes, Mount Hood NFs Douglas-fir/oceanspray Minor PSME, PIPO, QUGA, JUOC Simpson 2007Deschutes, Mount Hood NFs Grand fir/oceanspray Intermediate PSME, PIPO, ABGR Simpson 2007Fremont-Winema, Deschutes, Douglas-fir/starflower Widespread PSME, PIPO, CADE Simpson 2007

Mount Hood NFs

Fremont-Winema, Deschutes, Douglas-fir/creeping snowberry Intermediate PSME, PIPO, CADE, QUGA Simpson 2007

Mount Hood NFs

Fremont-Winema, Deschutes, Douglas-fir/prince's pine Intermediate PSME, PIPO, CADE Simpson 2007

Mount Hood NFs

Fremont-Winema NF Grand fir/creeping snowberry Intermediate PIPO, ABGR, PICO, PSME Simpson 2007

Fremont-Winema, Deschutes, Grand fir/golden chinquapin Widespread PSME, PIPO, ABGR Simpson 2007

Mount Hood NFs
36

GENERAL TECHNICAL REPORT PNW-GTR-897 Table 2—Mixed-conifer plant associations grouped by moisture and approximate fire regime (app. 2) (continued) Vegetation series/ National forest (NF)/regiona plant association Extentb Species compositionc Sourced Fremont-Winema, Deschutes, Grand fir/western starflower Widespread PSME, ABGR, PIPO Simpson 2007 Mount Hood NFs Fremont-Winema, Deschutes, Grand fir/common prince’s pine Widespread PIPO, ABGR, PICO, PSME Simpson 2007 Mount Hood NFs Fremont-Winema, Deschutes, Grand fir/starry false-solomonseal Widespread PIPO, ABGR, PICO Simpson 2007 Mount Hood NFs Mount Hood NF Douglas-fir/oceanspray/elk sedge Widespread PSME, PIPO, QUGA, ABGR Topick et al. 1988 Mount Hood NF Grand fir/starflower Widespread PSME, ABGR, PIPO Topick et al. 1988 Fremont-Winema, Deschutes, Grand fir/long-stolen sedge Intermediate PIPO, PICO, ABGR Simpson 2007 Mount Hood NFs Fremont-Winema, Deschutes, Grand fir/pinemat manzanita Intermediate ABCO, PICO, PIPO, PIMO Simpson 2007 Mount Hood NFs Mount Hood NF Grand fir/chinkquapin Minor ABGR, PSME, PICO, LAOC, PIPO Topick et al. 1988

Okanogan NF Douglas-fir/ninebark Minor PSME, LAOC, PICO, PIPO Williams and Lillybridge 1983Okanogan NF Douglas-fir/boxwood Minor PSME, PIPO, POTR5 Williams and Lillybridge 1983Okanogan NF Douglas-fir/huckleberry Intermediate PSME, LAOC, PICO, PIPO Williams and Lillybridge 1983Okanogan NF Subalpine fir/pinegrass Intermediate PSME, ABLA,PICO, LAOC, PIPO Williams and Lillybridge 1983Wenatchee NF Douglas-fir/huckleberry (three minor Minor PSME, LAOC, PICO, PIPO Lillybridge et al. 1995

huckleberry associations)

Wenatchee NF Grand fir/pinegrass– lupine Intermediate PSME, PIPO, ABGR, PICO, LAOC Lillybridge et al. 1995Wenatchee NF Grand fir/heartleaf arnica Intermediate PSME, ABGR, LAOC, PIPO, PIEN Lillybridge et al. 1995Wenatchee NF Grand fir/oceanspray–pinegrass Intermediate PSME, ABGR, PIPO, LAOC Lillybridge et al. 1995Wenatchee NF Grand fir/Cascade Oregon grape– Intermediate PSME, ABGR, PICO, LAOC, PIPO Lillybridge et al. 1995

pinegrass

Wenatchee NF Grand fir/common snowberry–pinegrass Intermediate PSME, ABGR, PIPO Lillybridge et al. 1995Warm Springs Indian Reservation Mixed conifer/snowberry/elk sedge Intermediate PIPO, PSME, ABGR Marsh et. al 1987Warm Springs Indian Reservation Mixed conifer/ceanothus Widespread PIPO, PSME, ABGR, CADE Marsh et. al 1987Warm Springs Indian Reservation Mixed conifer/snowberry Widespread PSME, PIPO ABGR Marsh et. al 1987Warm Springs Indian Reservation Mixed conifer/boxwood Intermediate ABGR, PSME, PIPO, LAOC Marsh et. al 1987Warm Springs Indian Grand fir/boxwood Intermediate ABGR, PSME, PIPO, LAOC Marsh et. al 1987

Reservation

Moist with mixed-severity fire—Characterized by moderate to high-severity fire with lesser amounts of low-severity fire in comparison to the moist-dry group. Fire return intervals are usually longer than 50 years. Natural fire regimes in order of prevalence are III B, III C, III A, IV B, and IV A.Blue and Ochoco MountainsWallowa-Snake Province Grand fir/big huckleberry Widespread ABGR, LAOC, PSME, PIEN, Johnson and Clausnitzer 1992 

ABLA, PIPO, PICO

Johnson and Simon 1987Wallowa-Snake Province Grand fir/Rocky Mountain maple Intermediate ABGR, PIEN, PSME, LAOC, PIMO Johnson and Clausnitzer 1992

Johnson and Simon 1987
37

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 2—Mixed-conifer plant associations grouped by moisture and approximate fire regime (app. 2) (continued)

Vegetation series/

National forest (NF)/regiona plant association Extentb Species compositionc SourcedBlue and Ochoco Mountains Grand fir/Columbia brome Intermediate ABGR, PSME, LAOC, PIEN Johnson and Clausnitzer 1992Blue and Ochoco Mountains Grand fir/grouse huckleberry–twinflower Intermediate ABGR, PIEN, LAOC, PSME Johnson and Clausnitzer 1992Blue and Ochoco MountainsWallowa-Snake Province Grand fir/twinflower Widespread ABGR, PIEN, PSME, LAOC, PICO, Johnson and Clausnitzer 1992

ABLA, PIPO, PIMO Johnson and Simon 1987

Wallowa-Snake Province Grand fir/queenscup beadlilly Widespread ABGR, LAOC, PSME, PIEN Johnson and Clausnitzer 1992Johnson and Simon 1987Colville National Forest Grand fir/big huckleberry/queenscup Intermediate PSME, LAOC, ABGR, PICO, Williams et al. 1995

beadlilly

Fremont-Winema, Deschutes NFs Mountain hemlock/golden chinquapin Widespread ABCO, ABPR, PICO, PIMO, PIPO, Simpson 2007

PSME, TSME

Fremont-Winema, Deschutes NFs Shasta red fir/golden chinquapin Intermediate ABPR, PICO, PILA, PIMO, PIPO Simpson 2007Fremont-Winema, Deschutes NFs Shasta red fir/common prince's pine Intermediate ABPR, PICO, PIMO, PIPO Simpson 2007Fremont-Winema, Deschutes NFs Shasta red fir/pinemat manzanita Intermediate ABPR, PICO, PIMO, PIPO Simpson 2007Fremont-Winema, Deschutes, Grand fir/twinflower Widespread PSME, ABGR, PIPO Simpson 2007

Mount Hood NFs

Fremont-Winema, Deschutes, Grand fir/queenscup beadlily Widespread ABGR, PSME, PIPO, TSME Simpson 2007

Mount Hood NFs

Fremont-Winema, Deschutes, Grand fir/vanilla leaf Widespread ABGR, PSME, PIPO, CADE, TSME Simpson 2007

Mount Hood NFs

Fremont-Winema, Deschutes, grand fir/wild ginger Intermediate PSME, ABGR, PIPO, ABMA/ABPR Simpson 2007

Mount Hood NFs

Mount Hood NF Grand fir/twinflower Widespread ABGR, PSME, PIPO Topick et al. 1988Mount Hood NF Grand fir/vanilla leaf Widespread PSME, ABGR, PIPO, PICO, LAOC, Topick et al. 1988

TSHE, ABPR

Mount Hood NF Grand fir/skunk leaved polemonium widespread ABGR, PSME, PICO, LAOC, PIEN, Topick et al. 1988

PIPO

Okanogan NF Subalpine fir/vaccinium Widespread LAOC, PSME, PICO, PIEN, ABLA Williams and Lillybridge 1983Wenatchee NF Grand fir/shiny-leaf spirea–bracken fern Intermediate PSME, PIPO, ABGR, PIMO Lillybridge et al. 1995Wenatchee NF Grand fir/vine maple–queencup beadlily Intermediate PSME, ABGR, PIPO Lillybridge et al. 1995Wenatchee NF Grand fir/Cascade Oregon-grape Widespread PSME, ABGR, LAOC, PIPO Lillybridge et al. 1995Wenatchee NF Grand fir/vanilla leaf Intermediate ABGR, PSME, LAOC, PIMO, PIPO Lillybridge et al. 1995Wenatchee NF Grand fir/vine maple–prince's pine Intermediate PSME, ABGR, PIPO, PICO, Lillybridge et al. 1995Warm Springs Indian Reservation Grand fir/snowberry Widespread ABGR, PSME, PIPO, Marsh et. al 1987Warm Springs Indian Reservation Grand fir/vine maple Widespread PSME, ABGR, PIPO Marsh et. al 1987Warm Springs Indian Reservation Grand fir/big leaf huckleberry Widespread ABGR, PSME, LAOC, PIMO Marsh et. al 1987Warm Springs Indian Reservation Grand fir–Lodgepole pine/ boxwood/ Intermediate PICO, ABGR PIPO, ABLA, Marsh et. al 1987

pinegrass
38

GENERAL TECHNICAL REPORT PNW-GTR-897 Table 2—Mixed-conifer plant associations grouped by moisture and approximate fire regime (app. 2) (continued) Vegetation series/ National forest (NF)/regiona plant association Extentb Species compositionc Sourced Moist to wet with high-severity fire—Higher severity fire tends to dominate in most events and return intervals are usually greater than 100 years. Natural fire regimes in order of prevalence are III C and IV B. Blue and Ochoco Mountains Grand fir/oakfern Minor ABGR, PIEN, PSME, LAOC, Johnson and Clausnitzer 1992 ACGL, TABR Blue and Ochoco Mountains Grand fir/sword fern–ginger Intermediate ABGR, PSME, LAOC, PIEN Johnson and Clausnitzer 1992 Blue and Ochoco Mountains Wallowa-Snake Province Grand fir/Pacific yew/ queen's cup Intermediate ABGR, PIEN, PSME, LAOC, TABR Johnson and Clausnitzer 1992 beadlilly Johnson and Simon 1987 Blue and Ochoco Mountains Grand fir/Pacific yew/ twinflower minor ABGR, PSME, LAOC, PIEN, TABR Johnson and Clausnitzer 1992 Blue and Ochoco Mountains Grand fir/false bugbane Intermediate ABGR, PIEN, ABLA, LAOC, PICO, Johnson and Clausnitzer 1992 TABR

Colville National Forest Grand fir/Douglas maple/queencup Intermediate PSME, LAOC, ABGR Williams et al. 1995

beadlilly

Mount Hood National Forest Grand fir–Engelmann spruce/ Minor ABGR, PIEN, PSME, PICO Topick et al. 1988

starry solomonplume

Mount Hood NF Grand fir/vanilla leaf–vine maple Widespread PSME, PIPO, ABGR, CONU Topick et al. 1988Note: This table is intended as an interim classification subject to further revision as new information becomes available. Note that terms used to describe climatic environment are relative terms and have different definitions among regions. Therefore, this regional classification may differ from local classifications.a National forest/region = subregion of the plant association. b Extent = geographic distribution and approximate area of a plant association relative to other associations within the region.c Species composition = all tree species recorded in each association, ordered by prominence within each association. 

ABGR = Abies grandis (grand fir); ABLA = Abies lasiocarpa (subalpine fir); ABPR = Abies procera (noble fir); 

ACGL = Acer glabrum (Rocky Mountain maple); CADE = Calocedrus decurrens (incense cedar); CONU = Cornus nutallii

(Pacific dogwood); JUOC = Juniperus occidentalis (western juniper); LAOC = Larix occidentalis (western larch); PICO = Pinus contorta (lodgepole pine); PIEN = Picea engelmannii (Engelmann spruce; PILA = Pinus lambertiana(sugar pine); PIMO = Pinus monticola (western white pine); PIPO = Pinus ponderosa (ponderosa pine); PSME = Pseudotsuga menziesii (Douglas-fir); QUGA = Quercus garryana (Oregon white oak); TABR = Taxus brevifolia (Pacific yew); TSHE = Tsuga heterophylla (western hemlock); TSME = Tsuga mertensiana (mountain hemlock).

d Source = citation for plant association description.
39

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Vegetation Classification and Disturbance Regimes

Effective restoration depends on having an accurate classification of vegetation 

and its disturbance regime. There are various schemas for classifying vegetation 

for purposes of ecological stratification, including current vegetation, historical 

vegetation, and potential natural vegetation (PNV). PNV in application is organized 

into a taxonomic hierarchy consisting of series, subseries, and plant associations, 

which are named for dominant overstory and undergrowth plants (Powell 2007). 

The standard system of vegetation classification and mapping used by the Forest 

Service and other federal agencies is based on this taxonomic hierarchy. Mixed 

conifer is composed of grand fir, white fir and Douglas-fir series, but the distinction 

of dry, moist and wet mixed-conifer types (i.e., disturbance regimes) requires the 

use of lower levels in the hierarchy, including subseries and groups of plant associations. We provide a first approximation for how associations could be grouped into 

four moisture/disturbance regime classes, (equivalent to subseries; table 2), but 

caution that this classification is interim and subject to revision as more knowledge 

becomes available. In this synthesis we use the term PVT in a general way to refer 

to any potential natural vegetation class regardless of level in the hierarchy (series, 

subseries, and plant associations).

A PVT is the native, late-successional (or “climax”) plant community that 

reflects the regional climate and the dominant plant species of an area that would 

occur on a site in the absence of disturbance (Pfister and Arno 1980). This approach 

assumes that disturbances still occur, but that the composition of the late-successional community occurring when disturbance is absent is a reasonable indicator 

of the biophysical environment. Hence, PVTs may be considered as approximate 

surrogates for the environmental conditions of a site (in terms of moisture, solar, 

nutrient, and temperate regimes) that exert some control on productivity, habitat 

potential, regeneration rates, and the frequency and severity of disturbance regimes.

Concepts of orderly succession and climax vegetation are questionable in 

mixed-conifer and other fire-prone eastside environments (O’Hara et al. 1996). 

These forests actually exhibit non-equilibrium dynamics, where the potential 

climax conditions were typically never realized due to myriad interacting and 

multi-scale disturbance processes, especially fire, that both advanced and retarded 

succession. Potential natural vegetation classifications can also take into account the 

reality that vegetation structure and composition is altered and controlled by periodic wildfire (Winthers et al. 2005). Much of the dry and MMC forests in Oregon 

and Washington would belong to these “fire climax” potential natural vegetation 

types. Despite these complexities of nature and the limits of our conceptual models, 
40

GENERAL TECHNICAL REPORT PNW-GTR-897

PVTs can be a useful starting place for identifying the ecological potential, fire 

regime, and restoration needs for an area. 

At finer scales (below subseries) the plant association is a unit defined on the 

basis of a characteristic range of species composition, diagnostic species occurrence, habitat conditions, and physiognomy (USDA FS 2005). A number of plant 

associations are included in the MMC type and some grade into the drier or wetter mixed-conifer types. See the list in table 2 for an interim assignment of plant 

associations to our mixed-conifer moisture/disturbance regime types. 

Tree species of the MMC forest are characterized as either early-, mid-, or 

late-successional (late-seral), and as either shade-intolerant or tolerant, respectively. 

The most common early-seral forest tree species are western larch (Larix occidentalis Nutt.), ponderosa pine (Pinus ponderosa Lawson & C. Lawson), lodgepole 

pine (Pinus contorta Douglas ex Loudon), western white pine (Pinus monticola

Douglas ex D. Don), trembling (quaking) aspen (Populus tremuloides Michx.; 

especially where a seasonally high water table exists), Douglas-fir (Pseudotsuga 

menziesii (Mirb.) Franco), and mixed conditions of these types. With the exception 

of Douglas-fir, each of these species is shade-intolerant, all readily regenerate after 

fire, and western larch, ponderosa pine, and Douglas-fir can become exceptionally 

fire-tolerant as they advance in age, owing to an ever thickening bark (Agee 1993). 

Dominant late-seral tree species are grand fir (Abies grandis (Douglas ex D. Don) 

Lindl.), white fir (Abies concolor (Gord. & Glend.) Lindl. ex Hildebr.; in central and 

southern Oregon), and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) and Engelmann spruce (Picea engelmannii Parry ex Engelm.), where local environmental 

conditions (e.g., cold-air drainage or pockets) occur that will promote dominance of 

these species. All are shade-tolerant and fire-intolerant. Exceptions can occasionally 

be found in mature grand fir and white fir, which may also possess a thick bark and 

occasionally occur in park-like stands (Hessburg et al. 1999a, 2000a). 

Under native fire regimes, the MMC forest would have displayed highly variable structure and composition regionally, making it among the most diverse and 

complex of all forest types (e.g., see the tables in app. 3 for the Blue Mountains 

province). The MMC forest landscape included a wide range of cover type and 

structural class combinations that would derive from a mixture of low- to mixedseverity fires with lesser amounts of high-severity fire in the mix (e.g., see app. 3, 

Hessburg et al. 2007, Perry et al. 2011). Recent studies in MMC forest in central 

Oregon suggest that the amount of low- and mixed-severity fire and forest structure 

(e.g., density) and tree layer composition in pre-Euro-American times may not have 

differed much from nearby dry mixed-conifer PVT (Hagmann et al. 2013, Merschel 

2012). 

Under native fire 

regimes, the moist 

mixed-conifer forest 

would have displayed 

highly variable structure and composition 

regionally, making 

it among the most 

diverse and complex 

of all forest types.
41

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

The PVT is not the same as the current or actual vegetation, which may exist 

in an early-, mid-, or late-successional state or in a nonnative and human-altered 

state (e.g., agricultural patch, urban or rural development area, pasture, or road 

right-of-way). The difference between the current and potential vegetation types 

can be important to restoration and should be known before undertaking restoration activities. The current vegetation type needs to be considered to determine 

which restoration trajectories are most probable, given local site conditions, 

landscape context, disturbance history, and potential climate change effects. 

Finally, with changing climate, PVT classifications based on the relationship of 

potential late-successional communities to their environment will be related to current and recent past climate conditions, but not to the future climate. Consequently, 

managers are best served by using a variety of sources of information about a site, 

including potential climate change effects, when making management decisions. 

Individual trees or populations exposed to climate conditions outside their climate 

niches may be maladapted, resulting in compromised productivity and increased 

vulnerability to disturbance. In some locations the future will not resemble the 

past with respect to potential vegetation, and assemblages of tree species that we 

currently recognize may be quite different in the future. This will be especially 

true where there is a rapid change in environment and vegetation (e.g., current 

ecotone edges). We suggest that a current PVT map be developed to the full extent 

of subwatersheds of each national forest, using regionally standardized protocols 

for PVT definitions and mapping.

Although it is generally accepted that the PVTs differ in their disturbance 

regimes, only a handful of dendroecological and landscape reconstruction studies have characterized variability in wildfire regimes in eastern Washington and 

Oregon (Agee 1994; Hessburg et al. 2007; Heyerdahl et al. 2001, 2013; Perry et 

al. 2011; Wright and Agee 2004), and have been conducted in the eastern Washington Cascades and Blue Mountains. More work is needed to better understand 

fire regime variability and relations with physiography. Studies of dry and MMC 

forests, which were characterized by highly variable low-, mixed-, and highseverity fire regimes, have been conducted in three eastern Washington ecoregions 

(Hessburg et al. 2007), and data are available to complete similar studies in the 

Blue Mountains and eastern Cascades of Oregon.

Similarly, syntheses of existing studies indicate relatively high variation in 

fire frequency within major plant series, especially at longer return intervals. For 

example, fire return intervals in the grand fir series range from 17 to 100 years 

(Agee 1994). Agee (1994, p. 17) stated that “the [warmer and drier] mixed-conifer 

forests of the Douglas-fir, white fir, and grand fir series show the most frequent 
42

GENERAL TECHNICAL REPORT PNW-GTR-897

fire activity of all eastside forests, although cooler, wetter sites of the grand fir 

series have longer fire return intervals. Frequent fires in drier plant associations of 

these series are likely due to higher productivity of fine dead fuels needed to carry 

another fire compared to the ponderosa pine series.” Hessburg et al. (2007) corroborated this finding. In dry mixed conifers, they found that low- and mixed-severity 

fires dominated by surface fire effects affected most of the area of this type. In the 

MMC type, they found that mixed-severity fires were also dominant, but crown fire 

effects stemming from mixed-and high-severity fires were more obvious.

High variability in fire regimes as a function of environmental and vegetation context means that the correspondence of a MMC PVT with a particular 

narrow range of frequency and severity of fire and other disturbances should be 

viewed with caution. Variation in effects of fire suppression and logging on forest 

structure and composition is relatively large within the MMC type, especially as 

it is expressed in different geographic areas of the region. Thus, it is important 

to develop first-hand knowledge of the historical and contemporary disturbance 

regimes of local landscapes, and of their expression by PVT. Other factors to be 

considered when assessing the local disturbance regime include topography, soil 

physical and chemical characteristics, overall geomorphology, disturbance and 

management history, and climatic variability. Figures 14 and 15 illustrate the 

inherent heterogeneity that typically exists on these complex landscapes. Figure 14 

shows the complex spatial configuration that results simply from basic topographic 

position at the southern end of the Wallowa-Whitman National Forest. Figure 15 

illustrates the more complex patchwork of landscape units that result from a combination of topography, simplified categories of precipitation, and soils in the Wenaha 

River watershed on the Umatilla National Forest. This is a simple example of the 

concept of using a Land Type Association (LTA) that incorporates a number of 

landscape features into an ecological classification system based on the associations 

of biotic and environmental factors, which include climate, physiography, water, 

soils, hydrology, and potential natural communities. 

General patterns of landforms, climate, and vegetation—

The ecological dynamics of the region are set within a geological and geomorphic 

template that controls climate, vegetation, and disturbance. Plate tectonics and 

volcanism, along with glacial and fluvial processes over geologic time, have produced distinct land surface forms, environments, and biotic assemblages across 

Oregon and Washington. These bio-geo-climatic contexts provide the basis to 

classify province-scale ecoregions (fig. 16) (Bailey 1995, Omernik 1987), and 

ecological subregions (Hessburg et al. 2000b) that reside within them. The location 

of the region on the windward Pacific Coast results in a predominantly marine-type 
43

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 14—A map of the lower Grande Ronde Watershed on the Wallowa-Whitman National Forest in northeast Oregon, 

illustrating the spatial heterogeneity of the watershed simply as a function of basic topography.
44

GENERAL TECHNICAL REPORT PNW-GTR-897

climate west of the Cascade Mountains, while east of the Cascades, the climate 

possesses both continental and marine characteristics (Western Regional Climate 

Center, http://www.wrcc.dri.edu). In fall and winter, a low-pressure system in the 

North Pacific Ocean brings moist and mild (i.e., pacific) westerly airflow across the 

region, resulting in a wet season that begins in mid to late October, reaches a peak 

in winter (January to March), then gradually decreases later in spring. Blocking 

pressure in the North Pacific in summer brings a prevailing westerly and northwesterly flow of comparatively dry, cool, and stable air into the Pacific Northwest.

Figure 15—A map of the Wenaha River watershed on the Umatilla National Forest in northeast Oregon, illustrating the landscape 

complexity derived from an integration of simplified topography, soils, and climate spatial data. 
45

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 16—Ecological regions of Oregon and Washington based on the LEVEL III Ecoregions of the 

Continental United States, Environmental Protection Agency (revised in April 2013). 

The orographic effects of the deeply dissected mountain ranges in the region 

result in occasionally heavy precipitation on the west slope of the Cascades and 

at higher elevations and relatively dry conditions on the east slope and at lower 

elevations (fig. 17). Temperatures vary from mild maritime conditions west of the 

Cascades crest to continental and temperate or Mediterranean conditions east of the 

Cascades. 

Plant life forms and community types vary predictably across these landforms 

and climatic gradients. The Douglas-fir/western hemlock (Tsuga heterophylla (Raf.) 

Sarg.) habitat type dominates west of the Cascade crest, except in the Willamette 

River, Umpqua River, and Rogue River valleys in the rain shadow of the Coast 

Mountains and portions of the Puget Trough (in the rain shadow of the Olympic 

Mountains), where oak savannas and dry coniferous forests occur (Franklin and 

Dyrness 1973). From the Cascades crest east to the west slope of the Rocky Mountains, there is a strong climate-induced stratification of vegetation types from valley 

bottoms to mountain tops. Sagebrush and grassland habitats dominate the Columbia 

Basin, the Great Basin, and the Snake River Plain. Ponderosa pine and juniper 

(Juniperus L.) habitats make up the lower forest and woodland ecotone. Douglas-fir 

occupies intermediate elevations, western larch and grand fir occupy still higher 

elevations, and Engelmann spruce and subalpine fir are found near upper tree line. 

Lodgepole pine inhabits subalpine environments and other low and mid-montane 
46

GENERAL TECHNICAL REPORT PNW-GTR-897

environments that are prone to cold air pooling. Gradients extending from dry, 

low-elevation rangeland vegetation to moist conifer forests are especially sharp 

in the East Cascades, Okanogan Highlands, and Blue Mountains. In these locations, topographic controls (e.g., aspect, slope position) on vegetation composition, 

density, and productivity are also especially pronounced.

At the coarsest level, net primary productivity (NPP) is limited by temperature 

at the highest elevations, by moisture in the driest locations east of the Cascades 

crest, and by insolation (direct sunlight) west of the Cascades crest (Running et 

al. 2004). As a consequence, NPP is highest in the Coast and Cascade Ranges, 

intermediate in the East Cascades, Okanogan Highlands, and Blue Mountains, and 

lowest in the Columbia River basin and the Great Basin (Verschuyl et al. 2008). 

Annual precipitation (inches)

0–10

10–20

20–40

40–60

60–80

80–120

120+

National forest

} Dry to moist mixed conifer

Precipitation varies across the 

mixed-conifer region from dry to wet 

But precipitation is only part of the 

story of moisture availability:

• Local climate

• Soil

• Topography

0 100 Kilometers

o

C A S C A D E R A N G E

BLUE

MTNS

WASH INGTON

OREGON

Figure 17—Generalized annual precipitation map of eastside Oregon and Washington. Note the significant rain 

shadow created by the Cascade Range and relatively high precipitation in some areas of the Blue Mountains.
47

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Vegetation dynamics—

Vegetation dynamics result from the interplay between succession and disturbance 

processes. In the simplest case, vegetation development at a patch scale may be 

characterized by change in composition and structure following stand-replacement 

disturbance (e.g., from fire, insects, or disease). In such cases, succession can initially be relatively rapid (years to decades) and obvious, but successional change is 

occurring all the time, even centuries after major disturbances. The rate and nature 

of succession is advanced or retarded by a myriad of major and minor disturbances 

(O’Hara et al. 1996, Oliver and Larson 1996). In this sense, at each occurrence, disturbances may reset the vegetation condition of any patch on new trajectories that 

play out over space and time (Peterson 2002, Peterson et al. 1998). Patch boundaries 

are non-stationary as well. Patches are blended or bisected by disturbances of various kinds and combinations. 

Large or severe disturbances may imprint the landscape for centuries before 

attenuating. The effects of small and low-intensity disturbances can be shorter in 

duration but still shape succession by altering site and microsite conditions that 

affect plant life histories by their influence on seed-fall, seed dispersal, post-dispersal seed losses, germination and recruitment, growth and mortality of juvenile and 

adult plants, reproduction, and a range of other factors. 

Given the environmental complexity, diversity of species and processes, and 

variation in frequency and severity of disturbances that affect MMC forest, the 

number of successional pathways and development stages is quite large (fig. 18). 

Consequently, the structure and composition of the MMC forest across eastern 

Oregon and Washington was highly diverse under pre-Euro-American disturbance 

regimes. It was a mosaic driven by low- to mixed- and occasional high-severity fire, 

and the patchwork of size and age class structure and species composition differed 

considerably. With wildfire exclusion, domestic livestock grazing, and timber harvesting, the fire regime has shifted toward increasingly larger and more severe fires, 

which tend to simplify the landscape into fewer, larger, and less-diverse patches and 

ultimately more homogenous landscapes. 

Ecological researchers are just beginning to understand ecoregional variation 

in the dynamics, structure, and composition of MMC forests. Given the generally sparse network of dendroecological and landscape reconstruction studies 

(especially in Oregon) our understanding of ecoregional and PVT-scale variation is 

provisional. In the eastern Cascades of Washington where high-severity fire was a 

component of the disturbance mix, the vegetation in MMC was a mosaic of small 

to very large patches comprised of early-, mid-, and late-successional forest conditions, and a broad variety of pure and mixed-cover types. In the eastern Cascades 

Large or severe 

disturbances may 

imprint the landscape 

for centuries before 

attenuating. 
48

GENERAL TECHNICAL REPORT PNW-GTR-897

Figure 18—Conceptual model of vegetation states and transitions associated with fire severity. Under low- to mixed-severity fire 

regimes, moist mixed-conifer forest landscapes were dominated by patches characterized by old trees and relatively open understories 

or old trees in a mosaic of open and dense understory patches (bold boxes in upper right). Forest structure and composition shifted 

among various structurally diverse stages (boxes in upper non-gray area) depending on ecoregion, fine-scale environmental variation, and amount of high-severity fire. Under fire exclusion and even-age management, forest structure and disturbance regimes have 

shifted potential forest stages and pathways into the lower region of the diagram (gray area) where the amount of dense old forest, 

high-severity fire, and uniform young forest is much greater than it would have been under the pre-Euro-American fire regime. Some 

old, dense multi-strata forest would have existed under the pre-Euro-American period but it probably was a small portion of the moist 

mixed-conifer type across the region.

Stand initiation;

no remnants

Open with

remnants Old dense

Multi-strata

Old

Open

Old

Mosaic

Open

Stem exclusion

Closed

Stem exclusion

Understory

Reinitiation

Young

Single-strata

Mature

Single-strata Mature

Multi-strata

Young

Multi-strata

Mature

Single-strata

with remnants

Low-severity fire

Mixed-severity fire

High-severity fire

No fire

Illustration by Tom Spies
49

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

of Oregon, where the disturbance mix may have had less high-severity fire, MMC 

forests might have been a mosaic of large shade-intolerant forest species that can 

resist fire, and sparse or patchy understories of species that regenerated in areas that 

were disturbed by surface fires, insects, or disease, or in patches where disturbance 

had not occurred for several decades (Merschel 2012). On drier sites where fires 

were less severe and more common (<25 years), the environment may have favored 

growth and establishment of ponderosa pine or Douglas-fir, and understories would 

have been relatively open or patchy as surface fires from low- and mixed-severity 

fires periodically cleared them out. More work is underway and in time our understanding of this complex issue will be more complete. 

Some sites within the mosaic of MMC forest would have had long intervals 

(>75 to 100+ years) between fires. It is on these sites that dense, multilayered forest 

conditions would have developed. In areas of high topographic complexity (e.g., 

eastern Washington Cascades and Blue Mountains) such sites are found on northfacing slopes at mid to upper elevations or at lower elevations near streams where 

moisture conditions would have made fuels too wet to burn except under infrequent 

hot dry weather conditions (Camp 1999, Camp et al. 1997). In areas of simpler 

topography defined by broad elevation gradients and isolated cinder cones (e.g., 

eastern Oregon Cascades), elevation and climate may explain the distribution of 

shade-tolerant species and fire regimes (Merschel 2012). Thus, many successional 

pathways occur in these landscapes but only a few of them would have reached old 

forest conditions where forests are relatively dense and dominated by shade-tolerant 

species, which are maladapted to fire-prone environments and droughty climate. 

Despite the variation in disturbance regimes and environments, historical stand 

densities of large fire-tolerant trees in both dry and MMC were typically low and 

fell within a relatively narrow range (table 3). Of 15 estimates of historical small, 

medium, and large tree stand densities from different dry and MMC types and 

environments (based on seven total studies), 12 estimates fell within the range of 40 

to 170 trees per hectare (16 to 70 trees per acre) and most of these estimates probably represent the minimum because most trees from cohorts that were regenerated 

in the 18th and 19th centuries were removed by disturbances. Regardless of their 

size, those that remain are simply the subset of survivors. Historical densities of 

large trees, most of them ponderosa pines and Douglas-firs, appear to fall within 

a relatively narrow range of low values from around 20 to 40 trees per hectare (8 

to 16 trees per acre) (table 3). Figure 19 illustrates the strong contrast in historical 

versus current tree density in five locations in eastern Oregon and Washington.
50

GENERAL TECHNICAL REPORT PNW-GTR-897 Table 3 —Historical and current density (trees per hectare) of large diameter (typically >50 cm) trees in dry and moist mixed-conifer forest Forest Region description Historical density Current density Source Notes Mean ± standard deviation (range) and time period Eastern slope of the Mixed-dry 35 ± 15 (3–105) 21 ± 12 (0–45) Hagmann et al. Historical density is reported for trees >53 cm diameter at breast Cascade Range, 1914–1922 1997–2006 2013 height (dbh) based on timber inventory transects that covered southern Oregon 10 to 20 percent (6646 ha) of a 38 641-ha study area of pon- derosa pine and dry and moist mixed-conifer forest. Current Mixed-moist 35 ± 17 (3–147) 16 ± 15 (0–114) density is based on 24 current vegetation survey (CVS) plots 1914–1922 1997–2006 within the study area, and density is reported for all trees >53 cm dbh. Inventory plots were assigned to habitat types (dry or moist) using mapped potential vegetation types (ILAP). Warm Springs Indian Mixed-dry 24 ± 10 (1–62) NA Hagmann, Historical density is reported for trees >53 cm dbh based on Reservation, eastern 1922–1925 unpublished timber inventory transects. Plot size varied by species. slope of the Cascade data, 2013a Transects covered >20 percent (6952–11 327 ha) of a 32 293–ha

Range, Oregon Mixed-moist 26 ± 12 (0–102) NA study area of dry and MMC forest. Inventory plots were

1922–1925 assigned to habitat types using mapped potential vegetation

types (ILAP).

Eastern slope of the Mixed-dry/moist HDSGb—32 HDSG—77 Ohlson and For trees >40 cm (16 in) dbh. See table 5 for more information.

Cascade Range, (estimates for WDSH—2 WDSH—82 SchellhaasWenatchee National several Douglas-fir WDTS—41 WDTS—99 1999c

Forest, Washington potential vegetation WMSH—27 WMSH—94

types) CDG—28 CDG—71

1899 1999

Blue Mountains, Mixed-conifer 27–32 NA Forest Service Historical density reported for trees > 50 cm.

central Oregon 1916–1932 inventories

Eastern slope of the Mixed-dry 28 ± 19 (0–71) 17± 17 (0–50) Merschel et al. Sample sites (~ 1.0 ha) were widely and randomly distributed in

Cascade Range, (Douglas-fir) Early 20th century 14 sample sites [N.d.] mature forest mapped in any of the mixed-conifer dry or mixedcentral Oregon 2009–2010 conifer dry plant association groups. The number of sample

sites used in each estimate is noted following the reported

Mixed-dry 30 ± 19 (17–85) 20 ± 15 (0–45) density. Density is reported only for shade-intolerant trees

(grand fir) Early 20th century 16 sample sites >50 cm. Historical density is based on diameter reconstruction

2009–2010 of cut stumps, and current density is based on live trees only.

Estimates refer to areas that were selectively logged, but 66

Mixed-moist 21 ± 17 (0–67.5) 12.9 ± 11 (0–45) of 177 sites sampled had no evidence of logging. Period of 

Early 20th century 24 sample sites historical density is estimated to be early to mid-20th century.

2009–2010

Ochoco Mountains, Mixed-dry 32 ± 13.8 (5–64) 25.1 ± 15 (0-64)

central Oregon (Douglas-fir) Early 20th century 26 sample sites

2009–2010

Mixed-dry 38 ± 19 (7.1–67) 19 ± 20 (0-65)

(grand fir) Early 20th century 14 sample sites

2009–2010

Mixed-moist 18 ± 16 (0–48) 13 ± 13 (0-40)

Early 20th century 14 sample sites

2009–2010
51

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 3 —Historical and current density (trees per hectare) of large diameter (typically >50 cm) trees in dry and moist mixed-conifer forest (continued)

Forest

Region description Historical density Current density Source Notes

Mean ± standard deviation (range)

 and time period

Eastern slope of the Mixed-conifer NA 38 TPH Johnston 2013, Density is reported for trees >50 cm in unlogged areas and

Blue Mountains, 2012 unpublished provides an estimate of historical large tree density in logged

eastern Oregon datad areas in dry and MMC forests.

Eastern slope of the Mixed-dry NA 21 ± 23 Reilly 2012, Density based on forest CVS plots distributed on a 2.5 by 2.5 km

Cascade Range and (n = 512) unpublished grid (5 km in wilderness areas) throughout national forests of

foothills, Oregon 1994–2004 datae Oregon and Washington. Sample sites include developmental

and Washington stages ranging from early seral in recently disturbed areas 

Mixed-moist NA 27 ± 27 (n = 280) (logging, wildfire, etc.) to mature old-growth forest. Density 

1994–2004 estimates are reported for trees >50 cm dbh. The number of 

CVS plots used to calculate density is reported in parentheses. 

Mixed-dry NA 19 ± 16 (n = 471) CVS plots were assigned to PVTs based on ILAP.

1994–2004

Blue Mountains Mixed-moist NA 23 ± 21 (n = 1041)

ecoregion, Oregon 1994–2004

and Washington

a On file with: Keala Hagmann, School of Environmental and Forest Sciences, University of Washington, Box 352100, Seattle, WA 98195. b Plant association groups with respective plant associations: 

HDSG (Hot/Dry/Shrub/Grass):

Pinus ponderosa/Agropyron spicatumPseudotsuga menziesii/Agropyron spicatumPinus ponderosa/Purshia tridentata/Agropyron spicatumPseudotsuga menziesii/Purshia tridentata/Agropyron spicatumPseudotsuga menziesii/Symphoricarpos albus/Agropyron spicatum

WDSH (Warm/Dry/Shrub/Herb):

Pseudotsuga menziesii/Arctostaphylos uva-ursiPseudotsuga menziesii/Arctostaphylos uva-ursi/Purshia tridentataPseudotsuga menziesii/Spirea betulifolia var. lucida

WDTS (Warm/Dry/Tall Shrub):

Pseudotsuga menziesii/Physocarpus malvaceusPseudotsuga menziesii/Physocarpus malvaceus/Linaea borealis var. longiflora

c Unpublished study of stand development in mixed-conifer forest on the Malheur National Forest. 

 On file with: James G. Johnston, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331.

d Ohlson, P.; Schellhaas, R. 1999. Historical and current stand structure in Douglas-fir and ponderosa pine forests.  Unpublished report. Portland, OR: U.S. Department of Agriculture, Forest Service, Okanogan and Wenatchee National Forests.e On file with: Matthew Reilly, Department of Forest Ecosystems and Society, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331.

Note: see table 5 for more information. Diameter thresholds, methods of estimation, and spatial coverage used to develop 

estimates differs among authors. 

WMSH (Warm/Mesic/Shrub/Herb): 

Pseudotsuga menziesii/Symphoricarpos albusPseudotsuga menziesii/Symphoricarpos albus/Calamagrostis rubescens

CDG (Cool/Dry/Grass):

Pseudotsuga menziesii/Arctostaphylos uva-ursi/Calamagrostis rubescensPseudotsuga menziesii/Purshia tridentata/Calamagrostis rubescensPseudotsuga menziesii/Spirea betulifolia var. lucida/Calamagrostis rubescens
52

GENERAL TECHNICAL REPORT PNW-GTR-897

Historical Versus Current Density

Dry Moist

Northeast Oregon North-Central Oregon Central Oregon Southern Oregon Central Washington

800

600

400

2000

800

600

400

2000

800

600

400

2000

800

600

400

2000

800

600

400

2000

Tree density (trees per hectare)

Period

Historical

Current

Figure 19—Historical versus current tree density in dry and moist mixed-conifer forest 

summarized from five study areas. Methods used to calculate density vary by reference 

period and study region, and diameter thresholds for tree density vary slightly among 

regions (10 to 15 cm). See the notes section in table 5 for citations and detailed information on how density was estimated in each region and time period.
53

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Landscape Concepts

Provincial or regional landscapes consist of nested local landscapes, which are 

themselves comprised of yet smaller land units often referred to as stands or patches 

(Wu and David 2002, Wu and Loucks 1995). At each nested scale, species and 

ecosystems are controlled by spatial and temporal heterogeneity of patterns and 

processes. What occurs within a patch is affected by its surroundings and viceversa. Figure 20 shows four east-west transects across montane regions of eastern 

Oregon and Washington and illustrates the continuous gradients of forest types that 

are found on these landscapes. MMC and other mixed-conifer types are thus part 

of a complex and intermingled landscape mosaic. The outcome of silviculture at the 

stand or patch level is thus inextricably linked to the interacting parts of the local 

and regional landscapes. 

Regional or broad-scale patterns of biota (e.g., life form zones and broad land 

cover types), geologic substrates (surface lithologies), geomorphic processes (land 

surface forms), and climatic patterns (e.g., spatial patterns of seasonal temperature, 

precipitation, solar radiation, and wind) constrain ecological patterns and processes 

occurring at a meso-scale. We call these constraints top-down spatial and temporal 

controls. For example, Bunnell (1995) found that the species composition of vertebrates in forest types is controlled by the disturbance regimes and mix of forest 

development stages found in biogeoclimatic zones in British Columbia, Canada. 

Changes to regional climate over relatively long time frames (100 to 1,000 years) 

affects relatively large spatial domains (1 million to 10 million ha). In other words, 

multi-century to millennial-scale changes in climate and geology can have a significant influence on species ranges. New plant and animal communities are potentially 

organized, new landform features emerge, and new patterns of environments and 

dominant disturbance regimes arise. A well-known example of landform effects 

in eastern Oregon is the eruption of Mount Mazama (current Crater Lake) about 

7,700 years ago, which created a landscape of deep pumice deposits that control the 

composition and productivity of forest vegetation across central Oregon (Franklin 

and Dyrness 1988).

Likewise, fine-scale patterns of endemic disturbances (e.g., native insects and 

pathogens), topography, environments, vegetation, and other ecological processes 

provide critical context for patterns and processes over narrower scales or extent. 

These are termed bottom-up spatial and temporal controls. Bottom-up controls 

occur over relatively small spatial domains (1 to 100 ha), and drive processes that 

can vary temporally from hourly to annual time scales. For example, cool, moist, 

north-facing slopes can create fire “refugia” in which disturbance regimes and 

environment favor the development of forest containing old, fire-intolerant tree 

What occurs within a 

patch is affected by 

its surroundings and 

vice-versa.
54

GENERAL TECHNICAL REPORT PNW-GTR-897

Topographic Profiles of Forest Types Derived From the PVT Maps

Oregon Blue Mountains Profile 2—Simpson Oregon Deschutes Profile 2—Simpson

Washington Cascades Profile 3—Simpson Washington East Profile 2—Simpson

Elevation (meters)

2000

1500

1000

500

0 10 20 30 40 50 

Kilometers

Elevation (meters) Elevation (meters)

1800

1600

1400

1200

1000

800

600

Elevation (meters)

1500

1000

500

0 10 20 30 40 

Kilometers Kilometers

1500

1000

500

0

0 10 20 30 40 

0 10 20 30 40

Kilometers

Ponderosa pine

Ponderosa pine–lodgepole pine

Dry/moist Douglas-fir

Dry white fir–grand fir

Cold dry white fir–grand fir

Moist white fir–grand fir/wet Douglas-fir

Wet white fire–grand fir

Lodgepole pine

Mountain hemlock/silver fir

Subalpine fir

Western hemlock

Other

Multiple PVTs

Figure 20—Profiles of predominant forest types, derived from potential vegetation types (PVTs) of Simpson (2007), across an eastwest transect for four locations in eastern Oregon and Washington. Topography is exaggerated to show topographic effects. 
55

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

species (Camp et al. 1997) (fig. 21). These small patches of old forest tree species 

can serve as seed sources that can affect rates and patterns of succession across the 

larger landscape (Wimberly and Spies 2001).

Figure 21—At the localized scale, mountainous terrain creates localized gradients in soil moisture, 

driven principally by differences in exposure to sunlight and wind (e.g., dry windy south-facing 

aspects versus cool moist north-facing hillslopes).

At all spatial and temporal scales of the hierarchy, landscapes exhibit transient 

patch dynamics and nonequilibrium behavior, resulting in ecosystem patterns and 

processes that may or may not change in linear or predictable ways. This is due to 

both random and deterministic properties of the supporting land and climate systems, and of ecosystem processes occurring at each level. Lower-level processes are 

incorporated into the next higher level of structures and processes, and this happens 

at all levels (figs. 11 and 21) (Wu and Loucks 1995).

Landscape patterns drive processes at local and regional landscape scales; 

at either scale, no two landscapes exhibit the same patterns across space or time. 

However, landscape patterns historically exhibited predictable spatial pattern characteristics. For example, a large sample of local landscapes (e.g., subwatersheds) 

comprised of dry and MMC forest in the lower and mid-montane settings, with 

subalpine forests in upper montane environments, reflected a predictable frequencysize distribution of cover type and structural class patch sizes (figs. 22 and 23). 
56

GENERAL TECHNICAL REPORT PNW-GTR-897

Here, think of histograms showing patch sizes in an inverse-J shaped distribution, 

with many small to medium-sized patches, and fewer large patches (fig. 23). Patterns and spatial arrangements of combined cover type and structural stage patch 

sizes (synonymous with O’Hara et al. [1996] structural classes) and their associated 

fuel beds provided constraint to the patch size and severity of disturbances. These 

patterns worked in concert with patterns of topography and weather influences to 

limit disturbance (Malamud et al. 1998, 2005; Moritz et al. 2010; Perry et al. 2011). 

This constraint probably appeared to be relatively stationary over multidecadal 

timeframes, but varied over multicentury periods. 

As top-down controls such as regional climate or land surface forms 

significantly changed over large spaces and long time frames, these ranges were 

constantly being nudged and redefined. Moreover, because context and constraint 

Figure 22—A sample of seven historical (ca. 1900) maps of combined cover type and structural class conditions from subwatersheds of 

the eastern Washington Cascades. Gray tones indicate unique cover type-structural class combinations. Note the highly variable patch 

sizes, with many small and fewer large patches. Despite their fewer numbers, the large patches actually make up the majority area of 

each subwatershed (adapted from Perry et al. 2011).
57

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 23—Frequency-size distributions of reconstructed historical (ca. 1900) fire severity patches in three ecoregions of the eastern 

Washington Cascades. Low, mixed, and high denote severity corresponding with <20 percent, 20 to 70 percent, and >70 percent of the 

overstory crown cover or basal area killed by fires, respectively. Data are from Hessburg et al. (2007). See Hessburg et al. 2000a for 

ecoregion details. 

varied in the long term, the processes and patterns they reflected also varied 

over time. In a warming climate, e.g., the envelope of ecological patterns and 

processes at each level in the spatial hierarchy (literally the range of variation, 

RV) is reshaped by the strength and duration of warming (fig. 24). Reshaping of 

landscape patterns within a level can be figuratively represented as an envelope of 

conditions that drifts directionally in time (e.g., Nonaka and Spies 2005). Hessburg 

et al. (2000b) developed quantitative ecoregions for the interior Columbia River 

basin. They showed that there are strongly overlapping spatial patterns of regional 

climate, geology, and geomorphic processes (fig. 25). Later, they showed that these 

ecoregions explained some of the variance between various physiographic settings 

in the amount of low-, mixed-, and high-severity fires (Hessburg et al. 2004). This 

was first-order evidence of broad-scale spatial controls on meso-scale fire regimes.
58

GENERAL TECHNICAL REPORT PNW-GTR-897

Figure 24—Comparing the historical range and variation (HRV, green dots and squares) and future range and variation (FRV, red dots 

and squares) with climate warming of five class metrics (paired in all possible combinations) of combined cover type–structural class 

patch types from a 10-percent random sample of subwatersheds of an eastern Washington Cascades ecoregion. The class metrics are 

the percentage of landscape area (PL_H, percent), the largest patch index (LPI_H, percent of the landscape), the patch density (PD_H, 

#/10,000 ha), the mean patch size (MPS_H, ha), and the edge density (ED_H, m/ha). The green square outlines the median 80 percent 

range of the subwatershed HRV sample. The red square outlines the median 80 percent range of the subwatershed FRV sample. Note 

the strong overlap between the HRV and FRV ranges in the pairwise combinations. In this example, we show paired combinations in 

a 2-space representation. Although impossible to graph here, one can imagine these metrics combined in a 5-space representation. In 

landscape analysis, any number of measures may be combined in an n-space representation to portray the HRV, the FRV, or both. In 

this way, departures or significant changes in spatial patterns of any contemporary landscape can be compared with the HRV and FRV 

to decipher the main characteristics of the changes.
59

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 25—Ecological subregions of the interior Columbia River basin (Hessburg et al. 2000a). Names corresponding with ESR numbers 

are of the form: [ESR number = Bailey’s (Bailey et al. 1994) ecoregion—Dominant Precipitation class(es)—Dominant Temperature 

class(es)—Dominant Potential Vegetation Group(s)—Dominant Solar Radiation class(es)]: 1 = M330–Wet–Warm–MF–Mod solar; 

2 = M333–Moist–Warm–MF/DF–Low solar; 3 = M333–Moist–Cold–MF–Low solar; 4 = M242C–Wet–Warm–MFCF–Low solar; 5 

= M242C–Moist–Warm–MF/CF–Mod solar; 6 = M242C–Wet–Cold–CF–Mod/Low solar; 7 = 342I–Dry–Warm–DS–Mod solar; 8 = 

M333A–Dry–Warm/Hot–DG–Mod solar; 9 = 300–Moist/Dry–Warm–DS/CS–High solar; 10 = 342I–Dry–Hot–DS/DG–Mod solar; 11 = 

200/300–Dry/Moist–Warm–MF/DF–Mod solar; 12 = M330–Moist–Warm–DF–Mod solar; 13 = 200/300–Moist–Warm/Cold–MF–Mod 

solar; 14 = M333A–Moist–Warm/Cold–MF–Mod solar; 15 = M332–Moist/Wet–Cold–CF/DF–Mod/High solar; 16 = 330–Moist–Hot–

DG–Mod solar; 17 = M333C–Wet–Cold–MF/CF–Low solar; 18 = M330–Moist–Warm–DF/DG–Mod solar; 19 = M330–Wet–Cold–MF/

CF–Mod solar; 20 = M330–Moist–Cold/Warm – MF–Mod solar; 21 = 331A–Moist–Warm–DG–Low solar; 22 = 200–Moist/Dry–Warm–

DF–Very high/High solar; 23 = M333D–Wet–Warm/Cold–MF–Low solar; 24 = M332–Moist/Wet–Cold–CF/DF/MF–High solar; 25 = 

M332–Moist–Cold–DF/CF–High solar; 26 = M332–Moist/Dry–Cold–CF–High/Mod solar; 27 = 300–Dry–Warm–CS/DF–High solar; 

28 = 200 – Moist–Warm–DF/DG–High solar; 29 = M332–Dry–Cold–DS/CS–High solar; 30 = 300–Moist–Warm–DG/DF–Mod solar; 

31 = 300–Moist–Warm–DF/DG–Mod solar; 32 = M332F–Moist–Cold/Frigid–CF–High/Very high solar; 34 = M332–Moist–Warm/ 

Cold–DF/CS–High solar; 35 = M332–Moist–Cold–CF/DG–High/Very high solar; 36 = M332–Dry–Cold/Warm–DS/CS – High solar; 

37 = M332B–Wet–Cold–RK/CF–Mod solar; 38 = M332–Moist–Cold–CF/DF/DG–Mod solar; 39 = M332B–Moist–Warm/Cold–DF/CF/

DG–Mod solar; 40 = 200–Moist–Warm/Cold–DF–High/Very high solar; 41 = M242C–Moist–Warm–MF/DF/CF–High solar; 42 = 300–

Dry–Warm–DS/CS–Very high solar; 43 = M331D–Moist–Cold–CF/DF/WD–Very high solar; 44 = 342–Dry/Moist–Warm–DS/CS–Very 

high solar; 45 = 342H–Dry–Warm/Hot–DS/CS–High solar; 46 = M242C – Moist–Warm–DF–High solar; 47 = 342C–Dry–Hot–DS/RS–

High solar; 48 = 342–Dry–Warm–DS–High solar; 50 = M331–Moist/Wet–Cold/Frigid–CF–High solar; 51 = 300–Moist/Dry–Warm–DS/

WD–High solar; 52 = M331–Moist–Cold–CF/WD – High solar; 53 = M242C–Moist–Cold–CF–Mod solar; 54 = M332–Moist–Warm–

MF/DF–Mod solar; 55 = M331D–Moist – Cold–WD–High solar. Potential Vegetation Groups are: AL = Alpine; CF = Cold Forest; CS = 

Cool Shrub; DF = Dry Forest; DG = Dry Grass; DS = Dry Shrub; MF = Moist Forest; RS = Riparian Shrub; RW = Riparian Woodland; 

RK = Rock; WA = Water; WD = Woodland. Precipitation classes are: Very Dry = 0–150 mm/yr; Dry = 150–400 mm/yr; Moist = 

400–1100 mm/yr; Wet = 1100–3000 mm/yr and Very Wet = 3000–8100 mm/yr. Temperature classes are: Frigid = –10––1 °C; Cold = 

0–4 °C; Warm = 5–9 °C; Hot = 10–14 °C. Solar radiation classes are: very low = 150–200 W/m2

; low = 200–250 W/m2; moderate = 

250–300 W/m2

; high = 300–350 W/m2; very high = 350–400 W/m2. Mixed composition of attributes is indicated with a “ / ” and mixed 

attributes are listed in order of decreasing abundance. Sampled subwatersheds shown are those sampled by Hessburg et al. 2000a.
60

GENERAL TECHNICAL REPORT PNW-GTR-897

Changes that are small in amplitude and short term relative to the tolerances of 

dominant organisms (often multiannual to multidecadal) will do little to reshape the 

envelope because of the strength of system memory (inertia and elasticity; existing 

patterns of disturbance and recovery), expressed in successional stages and composition of vegetation. But large-amplitude and long-term changes relative to organism tolerance (often over several decades to centuries) reshape pattern envelopes 

by imprinting those landscapes with new disturbance and recovery patterns over 

large areas. For example, changes to the climate of the Southwestern United States 

desert biome since the last glacial maximum have been so substantial that plant and 

animal species ranges have fundamentally shifted and reorganized, along with their 

disturbance regimes (Betancourt et al. 1990). 

It is informative for managers to understand the ranges of structural and compositional conditions that occur within landscapes of a region or subregion. Forest 

ecosystem response will be consistent with the current biophysical conditions and 

their disturbance regimes, including current climate forcing. For example, it is not 

clear how much the existing distribution of MMC forest will change with projected 

future climates and altered disturbance regimes. Fine-scale and gradual processes 

of mortality, dispersal, and range expansion are probably operating now to “adjust” 

patterns of species and ecosystems to the prevailing climate and disturbance trends 

of recent decades. Knowledge of factors controlling movement of species across 

landscapes provides insights to managers about how current landscape conditions 

will likely change, and thus how MMC forests may be able to persist under a 

changing climate. Multiscale research and monitoring are needed to elucidate these 

trends. Such information would enable a clearer vision to anticipate trends and 

develop tools for maintaining management options. 

Natural Disturbance Factors

In this section, we highlight key disturbance factors in the MMC forest. Disturbance regimes vary across climate and environmental gradients in a relatively 

predictable fashion. These disturbances strongly influence vegetation composition, 

structure and habitat conditions, which themselves influence the variability of 

disturbances. These are brief synopses of complex topics, and we encourage the 

reader to delve deeper into the literature cited for more detail. 

Wildfire—

Fire histories are not adequately documented in many moist forests in eastern 

Oregon and Washington. Our knowledge of past fire regimes and forest structure 

comes from proxy records, all of which are rich sources of data, but none of 

which is complete. Tree rings are one source of empirical data that can lead to 

Large-amplitude and 

long-term changes 

relative to organism 

tolerance (often over 

several decades to 

centuries) reshape 

pattern envelopes 

by imprinting those 

landscapes with 

new disturbance and 

recovery patterns 

over large areas.
61

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

multicentury reconstructions of fire and forest history, but only over small areas. 

Fire and forest vegetation histories reconstructed from aerial photos from the 1930s 

and 1940s are another source of empirical data, and although many such reconstructions predate most logging, most represent conditions that occurred 30 to 60 

years after fires were already excluded. Thus our inferences are constrained by data 

limitations, especially when we need to apply them to particular potential vegetation types or ecoregions.

Historical fire regimes across the region—In this region, several spatially extensive studies have reconstructed multicentury histories of low-severity fire regimes 

from fire scars in dry and MMC forests and inferred their climate, topographic, 

and land-use drivers at landscape and regional scales (Everett et al. 2000, Hessl 

et al. 2004, Heyerdahl et al. 2001, Kellogg et al. 2008, Wright and Agee 2004). 

However, few studies have focused specifically on MMC forests as we define 

them (Hessburg et al. 1999a, 1999c, 1999d, 2007; Heyerdahl et al. 2001; Perry et 

al. 2011; Tiedemann and Woodard 2002; Woodard 1977; Wright and Agee 2004). 

These studies suggest that mixed-severity fire was likely a dominant influence with 

smaller amounts of low- and high-severity fire. Current forest structure and life 

history strategies of trees typically found in mesic forests support our assumptions 

that historical fires were less frequent than in dry ponderosa pine and mixed-conifer 

forests and were of mixed severity (Agee 1993).

Although we have little quantitative information on the size (but see Perry et 

al. 2011) and frequency of past fires in MMC forests, mean fire return intervals 

may have much less importance than the range of fire intervals in this forest type 

(Halofsky et al. 2011). From only a few reconstructed fires (e.g., eight fires in 

Heyerdahl et al. 2001), there was a broad range of return intervals (several decades 

to more than 100 years, often within a single stand), but information on historical 

fire size was unobtainable with these methods. No studies have been designed to 

identify fine-scale variation in fire severity (i.e., patch size) within individual fires 

and only one within PVTs (see Hessburg et al. 2007). Landscape-scale reconstructions of forest structure from early to mid-20th century aerial photographs across 

the region also indicate that fires were of mixed severity (Hessburg et al. 2007). 

Perry et al. (2011) provided fire severity patch size distributions relating to dry and 

MMC forests in eastern Washington using the Hessburg et al. (2007) data set.

Historical fire regimes in MMC forests of this region likely varied across a 

broad range of spatial and temporal scales in response to regional variation in 

climate and physical geology, and local variation in topography and environments 

(Gedalof et al. 2005, Heyerdahl et al. 2001, Littell et al. 2009). These factors also 

control vegetation distribution, but PVT as mentioned above is only one predictor 
62

GENERAL TECHNICAL REPORT PNW-GTR-897

of historical fire frequency or severity (Hessburg et al. 2007, Heyerdahl et al. 2001). 

Historical fire regimes have been reconstructed in MMC forests elsewhere in the 

Interior West, but presently we do not have enough information about spatial and 

temporal variation in the drivers of fire in these forests to know how well these 

reconstructions capture historical fire regimes throughout eastern Oregon and 

Washington. Low-severity fires were strongly synchronized in dry forests across 

the region by climate in the past (Heyerdahl et al. 2008) and the same may be true 

for moist forests, but the case has not been clearly made. Historical fire severity 

patterns have been reconstructed using dendroecological methods from about 

10 percent of the total area of dry and MMC forests of the eastern Cascades in 

Washington. Extensive data sets are available from the Hessburg et al. (1999a, 

1999b, 1999c, 1999d) Interior Columbia River Basin data archive to continue this 

work in the Blue Mountains and eastern Oregon Cascades. 

Fire dynamics: resulting spatial patterns and tree mortality rates—Fire is a 

significant driver of mixed-conifer forest and aquatic ecosystems. The periodic 

influences of fire largely control the rates and patterns of succession and determine 

forest structure and composition, and aquatic and riparian condition. Despite recent 

contributions to the literature, there is still much scientific uncertainty and lack of 

consensus on the characteristics of fire regimes of mixed-conifer forests (amounts 

of low, mixed, and high severity), and how these varied by ecoregion. This lack 

of understanding (and investment in understanding) of the fire ecology of MMC 

forests limits the ability of managers to effectively identify appropriate steps toward ecosystem restoration. We do know that natural fire regimes in MMC forests 

varied somewhat predictably within areas that shared a similar climate and vegetation type, as well as topographic, edaphic (soil related), and environmental settings 

(Perry et al. 2011) (app. 3). 

Low- to mixed-severity fires produced a highly variable mosaic of living and 

dead trees at multiple spatial scales, resulting in patchy regeneration in stands and 

landscapes, and perpetuating the low- and mixed-severity fire cycle. Low-severity 

fires (killing less than 25 percent of the overstory) typically occurred where fires 

were most frequent (e.g., every 10 to 30 years). MMC patches that experienced 

low-severity fire occurred in areas and slope positions that were adjacent to dry 

mixed-conifer and ponderosa pine woodlands. Low- and mixed-severity fire appear 

to be dominant in the eastern Cascades and parts of the Blue Mountains based on 

recent and ongoing work (Merschel 2012). Elevation and aspect influences on plant 

available soil moisture played important roles. Figure 26 illustrates a forest subject 

to a typical low-severity fire regime.
63

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 26—An example of a low-severity prescribed fire. These fires are characterized by minimal 

short-term ecosystem effects. The result of a low-severity fire is fuel reduction and topkill of 

understory vegetation. 

Tom Iraci

Mixed-severity fires (killing 25 to 75 percent of the overstory) were common in the MMC forest because much of the area in these productive systems 

was visited by wildfires on a relatively infrequent basis (i.e., about every 25 to 75 

years). This allowed for the development of a patchy vegetation mosaic, with patchy 

patterns of surface and ladder fuels, and both open and closed canopy conditions 

(app. 3). One may contrast fire severity in this way: low-, mixed-, and high-severity 

fires produced fine-, meso-, and broad-scale patchiness of tree structure and species composition within local and regional landscapes. Figure 27 illustrates a forest 

subject to a typical mixed-severity fire regime.

High-severity fires (resulting in over 75 percent overstory mortality) occurred 

occasionally (Agee 1990, 1993, 1994, 1998; Baker 2012; Hessburg, et al. 2007; 

Heyerdahl et al. 2001, 2008; Williams and Baker 2012), especially where fire return 

intervals exceeded 100 to 150 years. These conditions tended to occur in slope and 

aspect conditions adjacent to wet and cool to cold forests (e.g., western hemlock, 

mountain hemlock [Tsuga mertensiana (Bong.) Carrière], Shasta red fir, and Pacific 

silver fir [Abies amabilis (Douglas ex Loudon) Douglas ex Forbes)]) and did not 

appear to dominate the fire regime of MMC forests. Figure 28 illustrates a forest 

subject to a high-severity fire regime.
64

GENERAL TECHNICAL REPORT PNW-GTR-897

Figure 27—An example of the impacts of a mixed-severity fire, exhibiting a wide range of effects on 

the dominant vegetation. Some areas exhibit low fire severity, with little damage to overstory trees, 

while others exhibit moderate fire severity. Some areas exhibit high severity as indicated by complete 

mortality of the overstory. 

John Marshall

Figure 28—An example of a high-severity fire, characterized by high levels of tree mortality, 

significant fuel consumption, and often extensive soil heating. 

John Marshall
65

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Landscape patterns: patch size and shape resulting from fire—There is still much 

to learn, but we know from fire history reconstructions using fire scars that small 

(1 to 50 ha [~2 to 123 ac]) to medium-sized (100 to 5,000 ha [~247 to 12,355 ac]) 

fires were most numerous, and pock-marked the landscape. They represented 85 to 

95 percent of fire events, but only accounted for 5 to 15 percent of all of the landscape area burned by historical wildfires (Malamud et al. 1998, 2005) (fig. 29). The 

primary role of these smaller fires was to spatially isolate patterns of combustible 

surface and canopy fuels across the landscape (Moritz et al. 2010). In fact, the 

common small fires (that are currently suppressed) played a key role in shaping the 

larger landscape. Burned and newly recovering patches to some extent spatially 

interrupted the flow of larger fires, often limiting their spread. This was the primary 

mechanism maintaining the frequency-size distributions of wildfires. Large fires 

(>5000 ha [12,355 ac]) were much rarer, but they typically burned most of the landscape area that was subject to fire (75 to 95 percent). Number of patches

105

104

103

102

101

100

Fire size distributions

Pre-management era

Modern era

Frequency-size shifts

Area (hectares)

100 101 102 103 104 105 106

Figure 29—A comparison of fire size distributions in the pre-management and modern era. This 

illustrates the frequency-size shift toward larger burn patches in the modern era. 

We know from fire 

history reconstructions 

using fire scars that 

small to mediumsized fires were most 

numerous, and pockmarked the landscape.
66

GENERAL TECHNICAL REPORT PNW-GTR-897

The distribution of fire event sizes approximated the negative exponential (an 

inverse-J distribution in the native form), and this appeared to be true regardless 

of fire severity (Perry et al. 2011). Overall fire frequency controlled the size of the 

largest fires. Numerous small- and medium-sized fires created patches of burned 

areas, in some stage of recovery, which reduced the likelihood of future fire spread. 

This mechanism likely provided a self-reinforcing type of resilience to the regional 

landscape. With relatively high fire frequency (as in surface fire dominated fire 

regimes), the largest fires were generally smaller than with relatively low fire 

frequency (characteristic of high-severity fire regimes).

Both landscapes and patches provided important feedbacks to wildfire frequency, severity, and size. At a landscape scale, low-, mixed-, and high-severity 

fires likely maintained patchworks of burned and recovering vegetation. Patches 

varied by size, age, density, layering, species composition, and surface fuelbed, 

and these landscape patterns spatially interrupted conditions that supported large 

disturbances, except under extreme conditions. Low- and mixed-severity fires also 

provided important patch level feedbacks, which encouraged subsequent low- or 

mixed-severity fires (Agee 2003, Agee and Skinner 2005, Hessburg and Agee 

2003). Such fires frequently reduced surface fuels, which favored shorter flame 

lengths, and reduced fireline intensities (rate of heat release per unit length of fire 

front). They also increased the height to live crowns, which favored less torching, 

and reduced the likelihood of crown fire initiation. They decreased crown density, 

which reduced crown fire initiation and spread potential, favored young forest tree 

species, which increased tree survival during wildfires and droughts, and favored 

medium- and large-sized trees, which increased tree survival during wildfires. 

Finally, low- and mixed-severity fires produced patchy tree and surface fuel cover, 

which favored fire-tolerant species, and repeated low- and mixed-severity fires.

During periods of extreme weather or during rare climate events, wildfires 

could become very large, and fire behavior was often unrelated to the initial forest 

conditions, but was instead correlated with the conditioning climate or weather 

influences. Fire size distributions and the vegetation patchwork that supported them 

have been altered by a host of management and settlement influences, which we 

have summarized.

Insects—

In eastern Oregon and Washington, several insect species are significant disturbance factors in MMC forests, including four native bark beetle species and two 

native defoliating species (Hayes and Daterman 2001, Hayes and Ragenovich 2001, 

Torgersen 2001). In addition to these, there is one nonnative defoliating species and 
67

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

one nonnative sap-sucking species of importance (table 4). The impact of these 

insects is influenced by other disturbances (e.g., root disease, extreme weather 

events, wind storms, or wildfire) while outbreaks influence the frequency, severity 

and extent of other disturbances.

Unlike defoliating insects, bark beetles feed on the phloem tissue beneath the 

bark, often directly killing the host quickly via girdling. Beetles that initiate host 

selection are often killed by drowning or immobilization in resin, so successful 

colonization requires a minimum number of beetles to “mass attack” the tree and 

overcome its defenses (Franceschi et al. 2005). This number varies, as more vigorous hosts require higher densities of beetles (Fettig et al. 2007). Therefore, the 

legacy of past disturbances influences the susceptibility of forests to future bark 

beetle outbreaks by affecting their structure and composition. Many bark beetle 

species exhibit a preference for larger diameter trees growing in high-density 

stands with a high percentage of host type (Fettig et al. 2007). Larger diameter trees 

generally provide for a higher reproductive potential and probability of survival 

(e.g., Graf et al. 2012, Reid and Purcell 2011) because of the greater quantity of 

food (phloem) available on which larvae feed. The effects of density are mediated 

through factors that affect host finding and colonization success, primarily microclimate, tree spacing, and changes in host vigor as mediated through the influence 

of growing space. Over the last decade, the majority of insect-caused tree mortality 

detected during aerial surveys in the region has been attributed to outbreaks of the 

mountain pine beetle (Dendroctonus ponderosae). The impact of this insect seems 

to be increasing in eastern Oregon and Washington, likely owing to changes in tree 

density and the abundance of preferred hosts (table 4), and is expected to intensify 

in the future (see “Climate Change” on page 102 and “Changes in Disturbance 

Factors: Insects and Disease” on page 115). 

Defoliators consume, mine, or skeletonize the foliage of trees and may cause 

tree mortality depending on the species and host, and the timing, frequency and 

severity of feeding. Without question, the two most important defoliators in MMC 

forests of eastern Oregon and Washington are the Douglas-fir tussock moth (Orgyia 

pseudotsugata) and western spruce budworm (Choristoneura occidentalis) (table 

4, figs. 30 and 31), which are notable for their infrequent, but occasional large-scale 

outbreaks (Torgersen 2001). Natural enemy populations (parasites, predators, and 

parasitoids) have a strong regulatory effect on their populations resulting in long 

time lags between outbreaks. In particular, western spruce budworm populations 

are well-coordinated with climate (Kemp et al. 1985, Volney and Fleming 2007). 

From the 1950s to 1980s, large-scale efforts were implemented to control Douglasfir tussock moth and western spruce budworm outbreaks using aerially applied 
68

GENERAL TECHNICAL REPORT PNW-GTR-897

Table 4—Insects considered major disturbances in moist mixed-conifer forests of eastern Oregon 

and Washington

 Primary host(s)

Common name Scientific name in region Scale of outbreaks Impacts

Bark beetles:

Douglas-fir beetle Dendroctonus Douglas-fir Local to landscape Mortality of individual trees or small 

 pseudotsugae groups of trees is typically associated 

with defoliation, drought, windthrow, 

wildfire, or root disease. Once 

established, outbreaks may cause 

large amounts of tree mortality over 

extensive areas.

Fir engraver Scolytus ventralis Grand fir, Local to landscape Mortality of individual trees or 

white fir small groups of trees is typically 

associated with drought and 

defoliation. Once established, 

outbreaks may cause large amounts 

of tree mortality. 

Mountain pine beetle Dendroctonus Lodgepole pine, Local to regional Episodic outbreaks are a common 

 ponderosae ponderosa pine, occurrence, but the magnitude and 

western white extent of recent outbreaks have

pine exceeded the range of historic

variability in much of the Western

 United States.

Western balsam Dryocoetes confusus Grand fir, Local to landscape Mortality of individual trees or

 bark beetle subalpine fir small groups of trees is common

and associated with windthrow.

Defoliators and other:

Balsam woolly adelgid Adelges piceae Grand fir, silver Local Accidentally introduced into the

fir, subalpine fir United States from Europe and first

detected in the Pacific Northwest 

in 1929. Adelgids are sap-sucking 

 insects. Feeding causes abnormal 

growth responses in affected trees 

termed “rotholtz.” Severe infestations 

cause growth loss, top-kill, and tree 

mortality. 

Douglas-fir tussock moth Orgyia pseudotsugata Douglas-fir, Local to regional Larval feeding causes growth loss,

grand fir, white top-kill, and tree mortality. Outbreaks

fir, subalpine fir are often short-lived. 

Larch casebearer Coleophora laricella Western larch Local Accidentally introduced into the 

United States from Europe and first 

detected in the Pacific Northwest in 

the 1950s. Larvae mine needles. 

Severe defoliation occurs, but larch (a 

deciduous conifer) withstands 

repeated defoliation. Growth loss is 

common, but tree mortality is rare. 

Western spruce Choristoneura Douglas-fir, Local to regional Early instar larvae mine needles

 budworm occidentalis grand fir, white and buds. Late instar larval feeding

fir, subalpine fir, causes growth loss, top-kill, and tree

western larch mortality. Feeding on staminate

flowers and conelets affects 

 regeneration.
69

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 30—Douglas-fir tussock moth larvae.

William M. Ciesla, Forest Health Management International, Bugwood.org

Figure 31—Spruce budworm larvae. 

Lia Spiegel
70

GENERAL TECHNICAL REPORT PNW-GTR-897

chemical and biological (bacteria- and virus-based) insecticides, but were thought 

to have little effect on population dynamics or levels of tree mortality (Torgersen 

2011, Torgersen et al. 2005). A successful example of classical biological control 

has significantly limited the impact of larch casebearer (Coleophora laricella) in 

the region (Ryan 1997). 

Although insect infestations affect timber and fiber production, and indirectly 

affect a range of ecosystem goods and services, numerous organisms depend on 

insect-related disturbances for their existence. Trees weakened or killed by insects 

and other disturbances (e.g., pathogens) can result in the transience of old forest 

structural conditions, and also create structure and food sources that have significant value to wildlife communities. The section “Animals of the Moist MixedConifer Ecosystem” on page 75 provides some detail on the role of snags and 

downed logs to wildlife. Furthermore, mortality of individual or small groups of 

overstory trees has a significant influence on the fine-scale spatial heterogeneity of 

mixed-conifer forests (Fettig 2012). For example, some insects, specifically bark 

beetles, inflict density-dependent tree mortality (Fettig et al. 2007), and consequently maintain a mix of tree species, ages, sizes and spatial heterogeneity that 

influence other disturbances (e.g., wildfire). 

There is some evidence that large-scale tree mortality events associated 

with insect outbreaks may increase fire risk and severity in affected forests. In 

recent years, these relationships have been studied most extensively in lodgepole 

pine forests affected by mountain pine beetle (fig. 32). Although there is some 

disagreement over predicted changes in fire behavior during and after mountain 

pine beetle outbreaks (reviewed most recently by Jenkins et al. 2014), most studies 

predict increases in surface fire rates of spread and fireline intensities resulting 

from increases in fine fuel loadings and reductions in sheltering (e.g., Hicke et al. 

2012, Klutsch et al. 2011, Page and Jenkins 2007). During outbreaks, changes in 

foliar chemistry and moisture content may also increase probabilities of torching 

and crowning, and the likelihood of spotting (Jolly et al. 2012, Page et al. 2012). 

Similarly, feeding by defoliators reduces crown cover, increasing the amount of 

light reaching the forest floor and influencing understory and mid-story vegetative 

dynamics. For example, western spruce budworm outbreaks have been shown to 

increase surface fuel loads, yet changes in fire behavior were not significant 

(Hummel and Agee 2003).

The current structure and composition of dry and MMC forests is thought to 

be more susceptible to large-scale defoliation by Douglas-fir tussock moth and 

western spruce budworm in areas where fire suppression and selective harvesting 

of ponderosa pine and larch have favored Douglas-fir, grand fir, and white fir. 

Although insect 

infestations affect 

timber and fiber 

production, and 

indirectly affect a 

range of ecosystem 

goods and services, 

numerous organisms 

depend on insectrelated disturbances 

for their existence.
71

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Defoliation, largely the result of infestation of these two insects, often predisposes 

trees to subsequent mass attack by other insects, specifically bark beetles such as 

the Douglas-fir beetle (Dendroctonus pseudotsugata). 

Diseases—

In eastern Oregon and Washington, several notable forest pathogens produce 

significant disturbance in MMC forests, including five host-specialized dwarf 

mistletoes and four native root pathogens. Disturbance comes in the form of tree 

mortality and reduced tree growth, both of which are influential to forest succession 

and stand dynamics processes. Numerous stem decay organisms are also common 

in large and older trees of most species. These are excluded for brevity here, but we 

urge interested readers to delve into this literature. For a concise survey of the most 

common diseases and insects affecting inland Pacific Northwest forests, we refer 

the reader to Goheen and Willhite (2006), and recommended references therein.

Figure 32—Mortality of lodgepole pine attributed to mountain pine beetle (Dendroctonus ponderosae) in northern Utah. In 

recent years, the effects of mountain pine beetle on fuels and fire behavior have been studied most extensively in the lodgepole 

pine forests of the Rocky Mountains. This species, however, now represents a significant threat to the mixed-conifer forests of 

eastern Oregon and Washington. 
72

GENERAL TECHNICAL REPORT PNW-GTR-897

Four tree-killing root diseases naturally occur in MMC forests: laminated 

root rot, caused by Phellinus weirii; Armillaria root disease, caused by Armillaria 

ostoyae; and both the P- and S-type annosum root diseases (formerly Heterobasidion annosum, now H. irregular and H. occidentale, respectively) (Filip 1990; Filip 

and Goheen 1982, 1984; Goheen and Filip 1980; Hadfield et al. 1986). Root diseases 

were common (<5 to 10 percent of patches affected) but not dominant in most 

presettlement-era MMC forests, where they provided structural diversity within 

patches and enhanced heterogeneity in size of openings, amount and shape of edge, 

and size of patches. They were likely most visible in areas with relatively infrequent fire, and less visible in areas influenced by frequent low- and mixed-severity 

fires (e.g., south-facing slopes and ridges), and where the dominant tree cover was 

ponderosa pine or western larch. 

Laminated root rot infects and kills susceptible Douglas-fir, grand fir, and 

white fir that grow in patches missed by fire. Transmission of the fungus that causes 

this disease occurs via mycelial growth, when roots of susceptible host trees come 

in contact with those of infected trees. Because the root systems of host trees are 

often well rotted after they are infected, these trees usually fall over in a jackstraw 

arrangement (Hadfield et al. 1986). Owing to the dominance of historical wildfires 

and the relative rarity of root rot centers (in comparison with current conditions), 

historical root disease centers likely provided small to large gaps that contained 

root disease resistant hardwood shrubs and trees and other resistant conifer species, 

which enhanced plant species richness, and provided mast and a variety of habitats 

suitable for small mammals (Maser et al. 1979; Thomas et al. 1979a, 1979b). 

Armillaria root disease also infects and kills susceptible grand and white fir, 

and occasionally Douglas-fir that grow in patches missed by fire. Transmission 

of the fungus that causes this disease occurs when roots of susceptible host trees 

come in contact with those of infected trees. Inter-tree transmission is facilitated by 

fungal mycelia and by specialized root-like fungal structures called rhizomorphs. 

Armillaria root disease ecology at the end of the 19th century was probably very 

similar to that of laminated root rot. Armillaria root disease probably played a role 

in forest succession and stand dynamics of many refugia dominated by grand or 

white fir. Refugia were found in shaded draws, on cool north slopes, in riparian 

areas and stream confluence zones (Camp et al. 1997), and adjacent to rock outcroppings and talus slopes, where fires burned with difficulty. This pathogen also 

overwhelmed low-vigor, mature, weakened, and injured trees, and those stressed 

by drought or lightning strike, scorched by fire, or attacked by other root pathogens 

(Filip and Goheen 1982, Goheen and Filip 1980). Thus, it is fairly common to find 

more than a single root pathogen colonizing trees.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

P- and S-type annosum root disease centers were relatively uncommon in 

presettlement-era forests. These diseases require freshly cut stumps or wounds 

for windborne spores to infect and initiate new root-disease centers. Before tree 

harvesting, annosum root disease existed as a butt rot of trees with root collar and 

stem wounds. In central, southern, and northeastern Oregon, stands that have had 

multiple entries to harvest trees have been shown to have the highest annosum root 

disease and associated bark beetle-caused tree mortality (Filip et al. 1992; Schmitt 

et al. 1984, 1991). Most surprising in the MMC forest is the rate of increase in 

S-type annosum root disease (H. occidentale) in grand and white fir. These forests 

contain large increases in S-type annosum because stumps were infected by spores 

when stands were logged (Filip et al. 1992, Hadfield et al. 1986, Otrosina and Cobb 

1989). Because S-type isolates are primarily pathogenic on true firs and spruces, 

the roles these stumps will play in the future incidence of disease is uncertain. 

Infection centers will continue to expand until fire or silvicultural activities create 

conditions for the reintroduction of young forest species.

Pine stump infection by P-type annosum (H. irregular) is often high in Douglas-fir and grand fir forests, but mortality in ponderosa pine is uncommon. With 

prolonged warming, however, P-type annosum may become more serious on what 

are now mesic white and grand fir sites.

In the current condition, all major tree-killing root diseases except P-type annosum are widespread, following landscape colonization by grand fir, white fir, and 

Douglas-fir (Hessburg et al. 1994). Collectively, the effects of root diseases on tree 

growth and mortality, and their contributions to flammable fuels are ecologically 

significant. At a watershed or subwatershed scale, as much as 7 to 10 percent of the 

area can be influenced at any one time by active infection centers.

Dwarf mistletoes have occurred for many millennia in Douglas-fir, ponderosa 

pine, western larch, lodgepole pine, and true firs but none was particularly threatening to the long survival of its host species (Alexander and Hawksworth 1975, 

Parmeter 1978, Tinnin 1981). Douglas-fir dwarf mistletoe (Arceuthobium douglasii) 

and western larch dwarf mistletoe (A. laricis) were probably common in mid-seral 

and old forests before the 20th century. Areas infested with these mistletoes tended 

to be the more mesic plant associations, in which fires appeared with moderate 

frequency. Mistletoes were probably most common on south-facing slopes, where 

fires were low- or mixed-severity, maintaining multiple cohorts, sizes, ages and 

layers of host trees. High-intensity fires would typically eliminate most (but not 

all) mistletoe-infested trees over large areas, and mistletoes would slowly re-invade 

from the perimeter at the rate of 3 to 4.5 m (10 to 15 ft) a decade (Hawksworth 

1958, 1960; Parmeter 1978; Wagener 1965), or from islands of infested trees that 
74

GENERAL TECHNICAL REPORT PNW-GTR-897

escaped burning. Especially in ponderosa pine and Douglas-fir, severe mistletoe 

infections provide an abundance of mistletoe brooms, fine fuels, resinous stems, 

branches, and cankers. Even low- and moderate-intensity fires would often torch 

these trees, destroying severely infected trees and infection centers (Koonce and 

Roth 1980, Parmeter 1978, Weaver 1974). No doubt active and passive crown fires 

were initiated in areas of severe mistletoe infestation. 

Dwarf mistletoe in Douglas-fir was probably more common on northerly 

aspects and in riparian areas, where the interval between fires was longer. Under 

historical fire regimes, Douglas-fir dwarf mistletoe was probably widely distributed 

but at low to moderate severity (Arno 1988, Fischer and Bradley 1987, Harrington 

1991). Mature Douglas-fir, with thick outer bark and crown bases elevated well 

above the forest floor, were quite resistant to surface fires. Douglas-fir dwarf mistletoe was well distributed in scattered, thick-barked overstory trees that had developed on young forest dominated landscapes under the influence of low-intensity 

fire, but further influence was minimal because understory Douglas-fir stocking 

was minimal. 

Conversely, young Douglas-fir had thin, resinous outer bark and crowns close 

to the forest floor, two characteristics that increased vulnerability to surface fires. 

When mistletoe brooms occurred on young trees, the likelihood of tree torching 

was increased (Harrington 1991, Tinnin 1984, Tinnin and Knutson 1980). Under the 

right wind and weather conditions, fires crowned from mistletoe-infected understories. In addition, mistletoe brooms in Douglas-fir nullified benefits of inter-tree 

competition and natural branch pruning by maintaining a flammable link with the 

forest floor. In patches where Douglas-fir was abundant in the understory, e.g., in 

northerly aspects, Douglas-fir dwarf mistletoe was probably quite abundant.

Given the range of fire frequency and severity in historical MMC forests, the 

western larch mistletoe was likely the most prevalent and influential in terms of tree 

growth and mortality. Western larch dwarf mistletoe was perhaps the most widespread of mistletoes in old forest stands. Of all the dwarf mistletoes, larch mistletoe 

survived fire in overstory western larch with the greatest constancy (Bolsinger 

1978), perhaps because of larch’s exceptional resistance to damage by fire (Lotan et 

al. 1981), its resistance or tolerance to both tree-killing and opportunistic root pathogens (Filip and Schmitt 1979, Hadfield et al. 1986), and the lack of primary bark 

beetle associates. Larch mistletoe brooms are weak and brittle and frequently break 

off when still relatively small. Under historical fire regimes, branch litter accumulating under infected hosts caused lethal fire scorching of some infected trees (Alexander and Hawksworth 1975). According to Tinnin et al. (1982), the increased burn 

potential accentuated the advantage of fire-adapted species such as western larch.
75

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Dwarf mistletoes create brooms in trees, sometime quite large, and this produces critically important habitat structure for many species of wildlife. Brooms are 

used for nesting, roosting, and hiding cover (e.g., see Bull and Henjum 1990, Bull 

et al. 1989, Forsman 1983, Sovern et al. 2011). Birds and squirrels also contributed 

to reintroduction of mistletoes to large host patches (Hawksworth et al. 1987). 

Mistletoes would persist in residual ponderosa pine and western larch overstory 

trees by virtue of their resistance to fire, or from irregularities in fuel continuity or 

arrangement, or fire behavior, and the spread of these mistletoes to newly regenerating patches would be much quicker (Parmeter 1978). The presence of mistletoe 

brooms is a prime example of a long-standing struggle between objectives to manage for wood production (i.e., foresters would be inclined to remove diseased trees) 

and objectives to maintain or enhance wildlife habitat (wildlife specialists would 

advocate keeping these trees). 

At least 40 percent of all of the Douglas-fir, western larch, ponderosa pine, and 

lodgepole pine forests east of the Cascade crest are infected with dwarf mistletoe 

(Bolsinger 1978). Infections are more widely distributed and have had a greater 

impact on tree health than ever before, except where large wildfires have recently 

occurred. Because of fire exclusion and selective timber harvesting, many remaining forests are densely stocked and multilayered, conditions that are conducive to 

spread of mistletoes. Conifers such as Douglas-fir or ponderosa pine with severe 

mistletoe infections exhibit declining crown vigor and reduced resistance, and are 

eventually attacked and killed by bark beetles and opportunistic root pathogens like 

Armillaria root disease (Hadfield et al. 1986, Morrison et al. 1991).

Animals of the Moist Mixed-Conifer Ecosystem

The landscape ecology concepts of resilience and natural range of variation 

described in the previous sections of this report provide important tools for understanding animal habitat and population function within MMC forests of the Pacific 

Northwest. Native animals evolved in the context of historical disturbance regimes 

and resultant landscape patterns. Managing for the natural range of variability 

(NRV) provides a conceptual starting point for capturing the habitat needs of native 

wildlife. Landscape resilience is also important to animal populations because it 

represents the tendency of a landscape to return to conditions that the native animal 

community is adapted to. Landscapes that are not resilient may shift into novel 

environmental conditions that can contribute to substantial changes in the animal 

community and loss of biodiversity. However, it is important to note that simply 

managing for resilient landscape conditions that are within the NRV may not be 

sufficient for the conservation of all animals (Wiens et al. 2008). 

Native animals evolved 

in the context of 

historical disturbance 

regimes and resultant 

landscape patterns. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

Some native species have been affected by threats not related to habitat amount 

and distribution, including interactions with invasive species (e.g., northern spotted 

owls [NSO] [Strix occidentalis caurina] and barred owls [Strix varia] [Gutierrez 

et al. 2007]), exposure to exotic diseases (e.g., bighorn sheep [Ovis canadensis] 

[Schommer and Woolever 2008]), or sensitivity to effects of specific human activities (e.g., disturbance associated with roads or recreation [Gaines et al. 2003]). 

Conservation of these species often requires more specific strategies that address 

habitat in combination with the specific risks to which they are sensitive. Several 

recent assessments have used this conceptual approach to compare the current 

landscape to estimates of habitat patterns under historical disturbance regimes 

to provide a “coarse filter” for evaluating the amount and distribution of habitat 

conditions, in conjunction with “fine filter” assessments of conditions for selected 

individual species that are sensitive to specific risks (Gaines et al., in press; Suring 

et al. 2011; Wales, et al. 2011, Wisdom et al. 2000). Results of these assessments are 

summarized in “Effects of Altered Disturbance Regimes, Land Use, and Climate 

Change on Animal Populations and Habitats” on page 115. Our focus in this section 

is to provide an overview of important considerations for managing fish and wildlife habitat and animal populations in MMC forests.

As highlighted in previous sections, the MMC forest type is characterized by 

environmental conditions that are intermediate between warm/dry and cold/wet 

forest types that are often adjacent to or intermixed with the MMC. This pattern 

results in an animal community that is composed of an overlapping mix of species 

that are also found in the adjacent forest types. The composition of the animal 

community and abundance of individual species within MMC forests depends on 

many factors including landscape patterns, forest structure, and how wet or dry 

conditions are within an individual stand and the surrounding landscape.

Using the wildlife habitat relationships database of Johnson and O’Neal (2001), 

Lehmkuhl (2005) concluded that bird and mammal communities in eastside interior 

MMC forests were a mix of species typical of low-severity low-elevation ponderosa 

pine forest (84 percent species similarity) and high-elevation high-severity mixedconifer forest (71 percent species similarity). About 40 percent of all species were 

shared in common among the three types. Mixed-conifer forest was more similar 

to ponderosa pine forest in supporting relatively more generalist or young forest 

species than higher elevation forests. Within eastside habitat types and disturbance 

regimes, the fire-prone ponderosa pine cover type supports the most species of 

amphibians, reptiles, and birds; whereas mammals are most species-rich in mixedconifer types (Bunnell 1995; Kotliar et al. 2002; Sallabanks et al. 2001, 2002).
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Habitats Within Habitats—Multiscalar Landscape Example of Canada Lynx

B R I T I S H

C O L U M B I A

W A S H I N G T O N

O R E G O N

I D A H O

M O N TA N A

A L B E R T A

90%

80%

70%

60%

50%

40%

30%

20%

10%

Open area

Large-scale

Species range represents 

the distribution of appropriate 

biotic and abiotic conditions 

for the species.

Meso-scale

Landscape unit

with sufficient

resources to

support an

individual or

pair. These units 

are inherently

patchy.

Fine-scale

Habitat features that

provide specific habitat

components for survival

and reproduction.

Denning

Foraging Cover

Figure 33—Wildlife habitat is represented at different scales. Individual animals are connected to key features of their 

environment over a confined spatial domain, small groups of a species interact regularly over a larger area, and populations 

of a species are distributed across large geographic areas. This multiscalar view illustrates the importance of considering 

habitat requirements of a species at different spatial scales. 

A key concept for understanding animal distribution and abundance in MMC 

forests is that animals need to acquire a variety of resources to meet their lifehistory needs and most animals use a variety of different habitats and structural 

features to acquire those resources. Morrison et al. (1998: 10) described wildlife 

habitat as “an area with a combination of resources (like food, cover, water) and 

environmental conditions (temperature, precipitation, presence or absence of predators and competitors) that promotes occupancy by individuals of a given species 

(or population) and allows those individuals to survive and reproduce.” In MMC 

forests, these wildlife habitat components are emergent properties of the forest 

communities and their growth, disturbance, and stand dynamics (sensu Oliver and 

Larsen 1996) processes. How these processes work at a variety of scales is important in determining where habitat components occur and whether they are arranged 

in a manner that allows animals to survive and reproduce. Like landscapes, areas 

used by animals can be thought of as “habitats within habitats” (fig. 33). 
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GENERAL TECHNICAL REPORT PNW-GTR-897

Landscape heterogeneity at a variety 

of scales plays an 

important role in 

determining the 

assortment of habitat 

conditions and resources available to 

the animal community 

in that landscape.

At the finest scale, animals use habitat features associated with specific forest 

structure attributes (e.g., snags for foraging and nesting); at the meso-scale (subbasin or watershed scale), they must find the appropriate configuration of those 

resources to meet their life-history requirements (e.g., the right combination of food 

availability and security from predators); and at the broadest scale, animals need to 

be able to move to find mates, disperse to new areas, prevent genetic isolation, and 

maintain broad-scale population function (meta-population dynamics). Selection of 

a finer-scale habitat feature is therefore constrained by habitat selection decisions 

made at broader scales (e.g., the forest stand an animal chooses to use is constrained 

by the variety of stands within the watershed where the animal is located [Johnson 

1980]). 

Landscape heterogeneity at a variety of scales plays an important role in determining the assortment of habitat conditions and resources available to the animal 

community in that landscape. At the broadest scale, the distribution of wildlife 

and fish species is determined by regional to subcontinental gradients in climate, 

topography, soils, and vegetation (Hansen et al. 2011). The tolerances of species to 

these biophysical gradients result in predictable patterns of community diversity. 

Across Oregon and Washington, species richness of birds, trees, and shrubs is 

highest in the Okanogan Highland and Siskiyou ecoregions (Hansen et al. 2006, 

Swenson and Waring 2006). The lower forest ecotones across the East Cascades, 

Okanogan Highlands, and Blue Mountains are also high in species diversity (Olson 

et al. 2001). These locations have intermediate precipitation, warm growing season 

temperatures, and intermediate primary productivity. These conditions provide 

diverse food resources, variable vegetation structure, and high levels of habitat 

diversity, with grassland/shrubland, dry forest, and moist forest habitats all in 

proximity. Amphibian diversity is low in the eastern Cascades compared to western 

Oregon and Washington, primarily because the dry climate in the eastern Cascades 

is less conducive to occupancy by amphibians (Olson et al. 2001). 

The spatial patterning of habitats across Oregon and Washington is also 

important in influencing connectivity for wildlife and fish populations. Genetic 

diversity, metapopulation dynamics, and population viability for many species 

is dependent upon the ability of individuals to move across landscapes (Bennett 

2003, Crooks and Sanjayan 2006, Hilty et al. 2006). Regional-scale landscape 

permeability patterns for forested landscapes in eastern Washington and Oregon 

(fig. 34) are important because these forests serve as important potential source 

areas for a variety of species in their own right, and they provide critical linkages 

between ecosystems in the Rocky Mountains, the Cascade Range, and into Canada 

(Singleton et al. 2002, Theobald et al. 2012, WHCWG 2010). 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Meso-scale landscape patchiness determines the arrangement of habitat 

resources for animals. A critical feature of wildlife habitat in mixed-conifer landscapes in eastern Washington and Oregon is the multiscale (landscape and stand) 

diversity and juxtaposition of patch types of differing composition and structure 

(Perry et al. 2011). Habitat heterogeneity on presettlement landscapes was largely 

a result of mixed-severity fire. As reviewed in previous sections of this report, the 

combination of extensive topographic variability, other intrinsic factors of the landscape (e.g., soils, accumulation of fuels, etc.), and the vagaries of weather interacted 

in each fire event to create complex mosaics of habitat with soft boundaries that 

distinguish the effects of varying fire severity. Forest patches in different stages of 

development typically have different habitat characteristics and provide different 

sorts of habitat features (Johnson and O’Neal 2001, Thomas 1979). These processes 

result in a variety of forest structure and composition patterns that can support 

different terrestrial wildlife communities (Smith 2000). Again, NRV provides a 

Figure 34—At a regional scale, habitat for large carnivores is more or less permeable to movement, depending on various vegetation and 

topographic conditions. This information is an important consideration when planning treatments for forests at a landscape scale. 
80

GENERAL TECHNICAL REPORT PNW-GTR-897

conceptual guide for providing the mosaic of habitat conditions that native species 

evolved with, but species with specific habitat needs or sensitive to specific risks 

often require special consideration (e.g., Suring et al. 2011).

Fine-scale within-stand diversity of vegetation composition and structure 

provides specific wildlife habitat features required for denning, nesting, foraging, 

and security for individuals of many wildlife species. Different stand development 

stages provide different habitat structures and resources.

Recently disturbed patches tend to support high plant productivity, and often 

exhibit a particularly high diversity of plant and animal species, including many 

specialist species (Hagar 2007, Swanson et al. 2011) (fig. 35). Focal species for 

assessing early-seral and postfire habitats in interior MMC communities in the 

Pacific Northwest include fox sparrow (Passerella iliaca), white-headed woodpecker (Picoides albolarvatus), western bluebird (Sialia mexicana), and Lewis’s 

woodpecker (Melanerpes lewis) (Gaines et al., in press; Wales et al. 2011). 

Figure 35—Postfire and other recently disturbed forest sites provide productive habitat for many wildlife species. This recently burned 

area on the Okanogan-Wenatchee National Forest has shrub and herbaceous vegetation that provides habitat features generally not found 

in more mature forests.

Peter Singleton
81

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Early successional habitats are also important for ungulate summer forage. 

Recent research has highlighted the importance of high-quality late-summer forage 

for elk survivorship and reproduction (Cook et al 2013). Early-seral openings within 

MMC forests can play a particularly important role by providing late-summer 

forage resources for ungulates (Lehmkuhl et al. 2013). Several species of migratory songbirds are also associated with deciduous shrub communities found in 

early-seral forest patches (Betts et al. 2010). Structural legacies (including live trees, 

snags, and logs) from predisturbance stands contribute important habitat components in recently disturbed areas by providing cavities, perches, escape cover, and 

protected microclimates (Bull et al. 1997, Franklin et al. 2000, Van Pelt 2008). The 

abundance of large snags and logs is a particularly important characteristic of postfire habitats (Smith 2000).

Vertebrate communities within even-age young forest patches are generally less 

diverse and abundant than those found in other stand development stages, particularly for sites dominated by dense, closed-canopy conditions with little structural or 

understory diversity. Nevertheless, mid-seral stands can provide important ecological functions, depending on specific habitat conditions and landscape context. 

Dense even-age stands can provide security cover for prey species where conditions 

support the prey but prevent effective access for foraging predators. For example, 

avian predators like NSO and northern goshawks (Accipiter gentilis) select areas 

with structurally diverse forest canopies to facilitate foraging, even while their 

prey can often be relatively abundant in nearby dense stands (e.g., Greenwald et 

al. 2005). The presence of biological legacies (big old trees, snags, and logs) from 

predisturbance stands can provide important structural diversity in mid-seral stands 

by breaking up an otherwise continuous canopy, providing cavities for nesting and 

denning, and adding structure to the forest floor (Bull et al. 1997, Franklin et al. 

2000). Mid-seral stands also serve an important role as “old growth in waiting.” 

Late-successional forest conditions can be relatively transient in interior mixedconifer forests compared to forests west of the Cascade Mountains owing to the 

variety of disturbance processes associated with this forest type (reviewed in this 

section and in “Natural Disturbance Factors” and “Aquatic Habitats”). Mid-seral 

forest stands can provide an important “conveyor belt” of forest stands that are 

developing structural characteristics of older forests that can serve as replacements when other older stands are affected by disturbance. Active management to 

facilitate the development of old forest characteristics including canopy structural 

diversity and small openings has become an important principle for management 

of mid-seral stands and is particularly important for the recruitment of old forest 

habitat conditions for wildlife (Franklin and Johnson 2012).
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GENERAL TECHNICAL REPORT PNW-GTR-897

Older forests with a diversity of tree ages and sizes (including larger, older 

trees) provide many unique ecological functions. Across the variety of forest 

structural conditions found in MMC forests, animal abundance and species diversity are favored by structural complexity in the form of varied tree sizes, abundant 

snags, and coarse woody debris (McComb 2001). Big old trees, living and dead, 

standing and down, provide unique and important habitat structures within old 

forest stands (reviewed by Bull et al. 1997, Thomas et al. 1979, and Van Pelt 2008). 

For example, snags and down logs provide denning and resting sites for American 

marten (Martes americana) (Bull et al. 2005). Long-legged myotis bats (Myotis 

volans) roost in snags and bark crevices of large old trees (Ormsbee and McComb 

1998). Stout lateral epicormic branches can provide nest sites for northern goshawks 

and other species (Daw and DeStefano 2001). Cavities (in snags or living trees) are 

particularly important keystone structures for wildlife communities. Such cavities 

are created by the interactions of pathogens, fire, strong winds, and primary cavity 

excavators, and are subsequently used by a variety of species (Bednarz et al. 2004, 

Parks et al. 1999).

The security, thermal, and moisture characteristics found beneath and within 

large down logs can be especially important for small mammals, amphibians, 

reptiles, and invertebrates (Bull et al. 1997). Large old trees, especially in dense 

mixed-conifer patches, have higher loads of epiphytic forage lichens, which are 

critical winter food for some species (Lehmkuhl 2005). 

The multilayer canopies found in older stands contribute to unique thermal 

characteristics within stands and provide structural complexity important for 

arboreal mammals and their avian predators. Goshawks and NSO use multilayered 

canopies (often found in MMC forests subject to periodic fire) because such layering provides room to fly within forest stands. Canopy gaps allow for understory 

tree establishment and allow for sunlight to penetrate the canopy to the forest floor, 

contributing to understory productivity and diversity. Understory productivity is 

the foundation of food availability for many species. For example, northern flying 

squirrels (Glacomys sabrinus) are more abundant in stands with diverse understories with plants that provide critical fruit and mast foods (Lehmkuhl et al. 2006b); 

diverse understory vegetation can provide important forage resources for ungulates 

(Lehmkuhl et al. 2013); and fruit-bearing shrubs provide important food resources 

for black bears (Ursus americanus) and other species (Lyons et al. 2003).

Typical focal species for assessment of MMC old forest habitat conditions in 

Washington and Oregon are northern goshawk and pileated woodpecker (Dryocopus pileatus) (Gaines et al., in press; Wales et al. 2011; Wisdom et al. 2000). 

Northern goshawks are broadly distributed throughout the Interior West, and are 

The security, thermal, 

and moisture characteristics found beneath 

and within large 

down logs can be 

especially important 

for small mammals, 

amphibians, reptiles, 

and invertebrates.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Impacts of Wildlife Herbivory 

Herbivory (i.e., grazing and browsing) by wild 

ungulates, primarily elk, can significantly affect 

forested and grassland ecosystems and is worthy of 

consideration in any management plan (see Lehmkuhl et al. 2013 for a recent review). Elk and deer 

can account for a significant portion of the animal 

unit months (AUMs) on a range: e.g., elk and deer 

made up about 90 percent of the estimated 78,000 

AUMs on the Yakima elk herd range in the eastern 

Washington Cascades. Utilization rates in grassland 

and forest are typically 40 to 60 percent of annual 

production, with herbivory concentrated in productive riparian areas and meadows but occurring in 

all forest types. Herbivory effects may intensify 

in some areas with a spring and summer forage 

base that has declined since the early 1900s with 

meadow contraction, development of dense forests 

due to fire suppression, regrowth of old burns and 

pre-1990 clearcuts, and infrequent forest clearcut 

harvesting as a result of regulatory changes during 

the last 20 years. Sustaining livestock and elk on a 

diminishing habitat base may have degraded habitat 

and enhanced establishment of exotic species in 

sensitive meadow and riparian areas. 

The impact of wild ungulate herbivory has been 

well documented in the Blue Mountains from longterm exclosures and other research. In Douglas-fir 

and grand fir forests, Riggs et al. (2000) found that 

ungulate herbivory seriously depressed biomass of 

shrub genera Acer, Linnaea, Amelanchier, Salix, 

Sorbus, Ceanothus, Physocarpus, and Rubus outside 

of 25-year-old exclosures, within which understory 

biomass was two times greater than that outside 

exclosures. Johnson (2007) found that the shrubs 

Rosa, Symphoricarpos, and Purshia increased 

dramatically in the absence of long-term browsing 

in shrubland communities in the Blue Mountains. 

Tiedemann and Berndt (1972) reported five times 

more shrub cover, primarily snowbrush ceanothus 

(Ceanothus velutinus) with Saskatoon serviceberry 

(Amelanchier alnifolia), chokecherry (Prunus

virginiana), and common snowberry (Symphoricarpos albus), inside versus outside a 30-year-old 

exclosure in a Douglas-fir/pinegrass (Calamagrostis

rubescens) habitat type dominated by ponderosa 

pine with Douglas-fir. Likewise in the eastern 

Washington Cascades, Lehmkuhl et al. (2013) 

documented high long-term grazing impacts on 

some species of typical and atypical forage shrubs, 

such as common snowberry, oceanspray (Holodiscus 

discolor), and pinemat manzanita (Arctostaphylos 

nevadensis) in mid-elevation Douglas-fir and grand 

fir cover types, sticky currant (Ribes viscosissimum) 

in high-elevation subalpine fir cover types, and little 

sagebrush (Artemisia arbuscula), scabland sagebrush (A. rigida), and desert bitterbrush (Purshia 

tridentate) in low-elevation nonforest cover types. 

Impacts on ungulate herbivory on shrubs are likely 

underestimated because historically high levels 

of herbivory by both wild ungulates and livestock 

in the study area already may have suppressed or 

eliminated highly palatable shrubs.

Proposed forest restoration management in 

the Blue Mountains (mainly the Douglas-fir and 

dry grand fir types) to reduce uncharacteristic fuel 

loads and restore resilient stand structures and 

processes likely will increase the forage base for 

ungulates by reducing canopy cover to <40 percent 

and stimulating understory development (Hedrick 

et al. 1968, Long et al. 2008, Lyon and Christensen 

2002, Skovlin et al. 1989, Vavra et al. 2005; but see 

Sutherland and Nelson 2010). Opening the canopy 

of long-closed stands with diminished seed banks of 

herbaceous species might increase invasive species 

cover (McGlone et al. 2009, Sabo et al. 2009; but see 

Wienk et al. 2004); however, responses of invasive 

species can vary considerably because of site 

conditions (Sutherland and Nelson 2010) and can be 

mitigated by management (e.g., weed control along 

roads). See Lehmkuhl et al. (2013) for a complete 

discussion of restoration impacts on ungulate 

habitat. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

associated with structurally diverse old forest conditions that provide nest sites and 

foraging opportunities (reviewed by Greenwald et al. 2005, and Squires and Kennedy 2006). Pileated woodpeckers are also broadly distributed in wet to dry mixedconifer forests throughout the Interior West. They are strongly associated with large 

snags and down logs for nesting and foraging (Bull and Holthausen 1993, Bull et al 

1992). American marten are also included as a focal species for assessment of old 

forest conditions, but are more closely associated with forest types that are colder 

and wetter than the moist mixed-conifer forest (Gaines et al., in press; Munzing 

and Gaines 2005).

Conservation concerns about the NSO, a federally listed threatened species, 

have had a substantial impact on management of MMC forests in the eastern 

Cascade Range (USFWS 2011). We do not have the space for an exhaustive review 

of the substantial literature on NSO in the eastern Cascade Range, however we will 

highlight a few key aspects of spotted owl biology directly related to MMC forests. 

These highlights are important for understanding spotted owl management in MMC 

forests, but they also provide some useful insights for conservation of other old 

forest species associated with MMC forest outside of the range of the NSO (management considerations for old forest species are discussed in “Effects of Altered 

Disturbance Regimes, Land Use, and Climate Change on Animal Populations and 

Habitats” on page 115).

Spotted owls in the eastern Cascade Range have similar requirements for 

spatial and structural heterogeneity as in other parts of their range (reviewed by 

Courtney et al. 2004), but differences in disturbance processes (i.e., mixed-severity 

fire regimes, past selection harvest practices, and presence of mistletoe clumps) 

contribute to some differences in apparent habitat associations. The classic description of NSO nesting, roosting, and foraging habitat is “a multilayered, multispecies 

canopy dominated by large (>76.2 cm [30 in] diameter at breast height [d.b.h.]) 

conifer overstory trees, and an understory of shade-tolerant conifers or hardwoods; 

a moderate to high (60 to 80 percent) canopy closure; substantial decadence in the 

form of large, live coniferous trees with deformities—such as cavities, broken tops, 

and dwarf mistletoe infections; numerous large snags; ground-cover characterized by large accumulations of logs and other woody debris; and a canopy that 

is open enough to allow owls to fly within and beneath it” (Thomas et al. 1990: 

164). Although NSOs in the eastern Cascade Range inhabit patches that meet this 

description (particularly in moist sites), they also use patches with smaller trees, 

where structural heterogeneity is enhanced by the presence of mistletoe brooms 

and biological legacies from previous, more open stand conditions (Buchanan et al. 

1995, Everett et al. 1997, Sovern et al. 2011). These stand structure conditions are 
85

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

often highly divergent from historical conditions (Everett et al. 1997, Hessburg et 

al. 2005, Lehmkuhl et al. 1994), and provide fuel characteristics and spatial patterns 

that are conducive to uncharacteristically high-intensity, widespread wildfire events 

(Agee 2003). 

Spatial and structural heterogeneity is also important for spotted owl prey. 

Bushy-tailed woodrats (Neotoma cinerea) and northern flying squirrels compose 

more than 50 percent of NSO prey biomass in these areas (Forsman et al. 2001, 

2004). Lehmkuhl et al. (2006a, 2006b) found that bushy-tailed woodrats and 

northern flying squirrels were associated with the presence of large snags, mistletoe 

brooms, and downed logs, with woodrats being found in both mixed-conifer and 

ponderosa pine types. Presence of diverse understory vegetation that provided 

a variety of food items was also important for flying squirrels (Lehmkuhl et al. 

2006b).

Competitive interactions with barred owls are an important factor contributing 

to recent NSO population declines (Forsman et al. 2011). Spotted owl populations in 

Washington and northern Oregon declined by approximately 40 to 60 percent from 

1989 to 2008 (Forsman et al. 2011). Many experts expect that NSO populations will 

continue to decline through much of their range as barred owl numbers increase 

(USFWS 2011). Barred owls in the eastern Cascade Range are most abundant in 

flatter valley bottom moist forest settings (Singleton et al. 2010). Interactions with 

barred owls may have contributed to the displacement of NSO pairs into drier 

midslope settings as early as the 1990s when most NSO activity centers were documented, resulting in relatively few historical NSO sites being documented in valleybottom MMC settings that otherwise appear to be suitable NSO habitat (Singleton 

2013). Persistence of the NSO population in mixed-conifer forest landscapes may 

depend on the ability of the local NSO population to adapt to the presence of barred 

owls (Gutteriez et al. 2007). Substantial habitat loss from natural or human-caused 

disturbances (e.g., fire or forest management activities) has the potential to exacerbate the negative impacts of interactions with barred owls by increasing competition for limited habitat resources (Dugger et al. 2011, Forsman et al. 2011). 

Several other unique habitats also occur in landscapes that support MMC 

forests, including deciduous forest patches, meadows, riparian areas, rock piles, 

cliffs, and caves (reviewed in Johnson and O’Neil 2001 and Thomas et al. 1979). 

Deciduous tree patches provide important habitat characteristics for a variety of 

species (Hagar 2007), particularly migratory birds (Betts et al. 2010), and can 

provide abundant cavities for woodpeckers and other species (Martin et al. 2004). 

Aspen stands were an important component of the historical landscape in areas 

that support MMC forest, but the availability of aspen habitats has been reduced 
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GENERAL TECHNICAL REPORT PNW-GTR-897

substantially by altered disturbance regimes and herbivory impacts from both 

native and domestic animals (Shirley and Erickson 2001, Strong et al. 2010). Natural 

moist meadows are another particularly productive community within landscapes 

that support MMC forest. Meadows provide important ungulate forage resources 

(Lehmkuhl et al. 2013) and contribute to unique edge conditions that are important 

for a variety of wildlife including great grey owls (Strix nebulosa) (Bull and 

Henjum 1990) and long-eared owls (Asio otus) (Bull et al. 1989).

Area of meadows has been reduced by tree encroachment as a consequence of 

altered disturbance regimes (Haugo and Halpern 2007). Meadow communities have 

also been altered by domestic livestock grazing and intense use by native ungulates 

(Beebe et al. 2002). Large carnivores (particularly wolves) historically played 

an important role in limiting concentrations of native ungulates in these highly 

productive areas (Beschta and Ripple 2009). Ecological functions of streams and 

associated riparian areas are reviewed below, but it is worth emphasizing that in the 

context of animal habitat in disturbance-prone landscapes, riparian areas can provide unique linear landscape features that contribute to important ecological flows 

through the landscape, including animal movement. Rocks, cliffs, and caves also 

provide unique landscape elements that can be important for many species (Thomas 

1979). Rocky talus and scree slopes can provide unique habitat features for amphibians including larch mountain salamander (Plethodon larselli) (Crisifulli 2005) and 

secure areas for rodents including bushy-tailed woodrats and pika (Simpson 2009). 

Cliffs provide nesting opportunities for raptors (including peregrine falcon [Falco 

peregrinus]), and caves can provide hibernacula for bats.

The literature on wildlife habitat associations within MMC forests in western 

North America is vast and beyond the scope of this document. However, two 

main themes emerge from our review of the information: (1) natural disturbance 

processes play a key role in the development of stand structure conditions and 

landscape patterns that determine habitat values for animals, and (2) biological 

legacies (big old trees, snags and logs) provide important habitat structures across 

all stages of stand development. Within-stand structure is influenced by disturbance 

processes that function at a variety of scales. Endemic levels of disturbance can 

contribute to stand and landscape heterogeneity, while large-scale, high-intensity 

disturbances can reduce stand and landscape heterogeneity. Within-stand structural 

diversity is generally much greater in stands with a variety of tree age and size 

classes, even if those stands are recently disturbed or dominated by younger trees. 

Big trees and logs are often a legacy of previous stand conditions that have been 

retained after some disturbance event, like fire or harvest (Franklin et al. 2000). 

The variety of extremely valuable habitat structures provided by these large old 
87

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

trees include cavities, large branches, broken tops, brooms, and platforms (Bull et 

al. 1997). The presence of large old trees within a stand can make a big difference 

for wildlife habitat values in both old and young forests. 

Aquatic Habitats

From the literature, two concepts emerge as foundational for managing linked 

terrestrial and aquatic ecosystems: (a) watersheds and their aquatic habitats and 

species are dynamic and adapted to insect, disease, weather, and wildfire disturbances, and (b) the climate will continue to have a profound influence on terrestrial 

and aquatic ecosystems, disturbance processes, and their interactions (Bisson et al. 

2003; Luce et al. 2013, 2014; Tague and Grant 2009).

Disturbances play a vital role in structuring aquatic ecosystems. Wildfires 

influence hydrological and physical processes, such as surface erosion, sedimentation, solar radiation, wood recruitment, and nutrient exchange in streams (Benda et 

al. 2003, Luce et al. 2009, Miller et al. 2003, Wondzell and King 2003). The timing 

and severity of erosion and sedimentation differ by the physical geography, geology, and geomorphic processes; precipitation; and fire regime. Erosion contributes 

to sedimentation and can depend on riparian vegetation density and the speed of 

vegetation recovery after disturbance. Chronic erosion delivers fine sediment for a 

fairly long time, usually in the absence of revegetation after disturbance, or it comes 

from road rights-of-way, trails, and bulldozer lines. Postfire riparian erosion results 

in larger pulsed sediment and wood delivery to streams, and in some circumstances, channels can be reorganized, affecting aquatic habitats (Benda et al. 2003, 

Miller et al. 2003, Minshall 2003, Reeves et al. 1995). Water retention properties 

of the soils and reduced evapotranspiration from vegetation loss in the surrounding landscape affect runoff dynamics. Over time, coarse wood and sediment are 

depleted. Fluvial action and rot tend to break down stream wood, which can then be 

transported downstream along with sediment and rock. These processes continue 

until the system is replenished by subsequent postfire erosional events (Benda et al. 

2003, Miller et al. 2003).

In general, episodic large-scale disturbances (e.g., fire) to aquatic ecosystems 

are inevitable and often beneficial when spaced out over long periods, and this 

knowledge can form an important ecological foundation for fire and forest management. Anadromous and resident species in such landscapes evolved with these 

disturbances and the attendant shifts in habitat quantity and quality. These species 

are affected by habitat reorganization associated with wildfires, including addition 

of wood material and sediment deposition; thus, they are considered to be fireadapted. The natural frequency, severity, and extent of historical fires governed the 

Disturbances play a 

vital role in structuring 

aquatic ecosystems. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

pulse of erosional events that carried wood, rocks, and soil to streams and created 

variation in the level of stream shading and aquatic habitat available to fish provided 

by riparian vegetation. Fish populations have been shown to recover rapidly to the 

natural fire regime in burned reaches, depending on connectivity of stream networks 

(Burton 2005). Thus, restoration of conditions that promote a natural fire regime will 

benefit fish populations overall. Where fish populations are robust, recolonization of 

stream segments disturbed by fire is tenable (Burton 2005).

This dynamic view diverges from traditional frameworks that suggest that 

aquatic ecosystems should be managed as stable systems perpetually maintained for 

select species. Stable equilibrium and balance of nature views are equally intractable 

in terrestrial and aquatic ecosystems. The dynamic view of aquatic systems accepts 

patterns of disturbance and recovery across landscapes as necessary processes to 

interconnect mosaics of diverse and changing habitats and communities. 

Streams draining burned areas of the Entiat Experimental Forest (EEF) on the 

east side of the Cascades crest in Washington had peak flows 120 percent higher 

than prefire conditions (Siebert et al. 2010). Additionally, there were deeper snowpacks and more rapid snowmelt as a result of the disturbance. However, only the 

upper elevations of the EEF consist of mixed-conifer forest with slightly higher 

moisture (mean annual precipitation at mid-elevation = 580 mm) (Seibert et al. 

2010). Similar hydrologic issues could likely prevail following fire disturbance in 

moist forests. The primary lesson from Siebert et al. (2010) is that prefire hydrologic 

data are essential to quantifying the postfire response.

Climate change affects forest landscapes, wildfire regimes, aquatic habitats, 

management options, and their interactions. Climate variability can have important effects on stream hydrology (Jain and Lall 2001, Poff et al. 2002, Tague and 

Grant 2009) and related physical processes (Bull 1991, Meyer et al. 1992, Pederson 

et al. 2001, Schumm and Hadley 1957). Changes in hydrology can happen rather 

abruptly (i.e., 10 to 100 years), and decadal- to multidecadal-scale climate regime 

shifts can influence stream flows more than the management practices on which we 

focus most attention (Jain and Lall 2001). April 1 snowpack has declined in mountainous regions across the Western United States (Mote 2003, Mote et al. 2005). 

Changes are largely attributed to elevated winter and spring temperatures (Hamlet et 

al. 2007, Stewart et al. 2005). Snowpack decline is expected to continue as temperatures rise throughout the region. Changes in the timing and magnitude of precipitation are expected because of interactions between rising air temperatures, snowfall, 

and rainfall across complex local terrain. Warming will result in more precipitation 

falling as rain than snow, and earlier snowmelt timing (e.g., Hamlet et al. 2005).
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Climate change profoundly affects processes that create and maintain aquatic 

habitats. Some effects are direct, particularly those involving stream temperature, 

water yield, peak flows, and timing of runoff (Luce et al. 2014). Other effects 

occur indirectly as climate change forces alteration of the structure and distribution of forest communities and the characteristics of wildfire. These processes will 

indirectly affect fish in relevant watersheds. Altered snowmelt run-off regimes in 

the mixed-conifer forests will affect downstream fish-bearing reaches. Discharge 

patterns affect water depth; thus, earlier low flows downstream may reduce habitat 

availability for fish dependent on deeper, slower flowing habitats. Changing precipitation and fire regimes are expected to compound the effects of warming trends 

by shifting hydrologic patterns and those of sediment transport and solar radiation 

(Dunham et al. 2007, Isaak et al. 2010). The structure and composition of riparian 

vegetation imparts important influences on temperature and soil moisture gradients 

immediately adjacent to streams (Anderson et al. 2007).

Fish and other aquatic biota are likely to be affected by wildfire and climate 

change in MMC forests. Aquatic ecosystems consist of interacting species at all 

trophic levels. Productivity in each level can depend on inputs and transfers across 

the terrestrial-aquatic ecotone. Movement of terrestrially derived production into 

streams can affect primary production with implications further up the food web, 

including aquatic insects and fish (e.g., Baxter et al. 2004, Nakano et al. 1999). 

Resources transported downstream and organic matter of terrestrial origin can alter 

downstream fish-bearing habitats according to spatial variation in the headwaters 

(Baxter et al. 2004, Binckley et al. 2010, Wipfli et al. 2007). Convergence of loworder streams that drain large landscapes at downstream habitats potentially results 

in productivity “hot-spots” (e.g., Kiffney et al. 2006). Efforts to establish transport 

distances and specific responses in fish have been limited in mixed-conifer areas 

(but see Polivka et al. [N.d.]1). Nevertheless, some successional stages can have 

measurable influence on the standing crop of aquatic macroinvertebrates (Medhurst 

et al. 2010).

Streams in dry and MMC forests are not especially diverse in terms of fish 

species, but they do consist of species that are sensitive to temperature increases 

in spawning and rearing streams and that respond to disturbances such as wildfire. 

Less is known about how fire will affect macroinvertebrate communities that serve 

1

 Polivka, K.M.; Dwyer, G.; Mehmel, C.J.; Sirianni, K.M.; Novak, J.L. [N.d]. Effects of 

temperature and virus persistence time on wild and pesticide strains of the nucleopolyhedrovirus (NPV) pathogen of larval Douglas-fir tussock moth (Orgyia pseudotsugata). 

Manuscript in preparation. On file with: Karl Polivka, Pacific Northwest Research 

Station, Forestry Sciences Laboratory, 1133 N. Western Ave., Wenatchee, WA 98801.
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GENERAL TECHNICAL REPORT PNW-GTR-897

as food resources for fish. Successional patterns following disturbance can affect 

macroinvertebrate communities, but it is unclear whether changes at one trophic 

level will be detectable at levels above (i.e., fish) (Medhurst et al. 2010).

In fish-bearing streams of Idaho, the intensity of fire determined the density 

and age structure of rainbow trout (Oncorhynchus mykiss) (Dunham et al. 2007). 

Relative to controls, streams adjacent to habitats that burned showed relatively 

more rapid growth of age 1+ rainbow trout, an effect that was augmented in streams 

that were physically re-organized by erosion and sedimentation following the fire 

(Rosenberger et al. [N.d.]). This study ranged from lower elevation dry forest to 

elevations containing MMC and subalpine forest in the Boise River basin. Fish 

recovery following riparian fire can be fairly rapid in streams where there is a 

robust local population to recolonize disturbed habitat, and management of fire 

severity might be most important in areas where local populations are weak and 

isolated (Burton 2005). Management of roads might also be necessary, given that 

fragmentation of stream habitat might not only affect the ability of a fish population 

to recolonize stream segments affected by fire, but might also affect patterns of 

genetic diversity in resident trout species (Neville et al. 2009). 

Cutthroat trout (Onchorhynchus clarki) and bull trout (Salvelinus confluentus) 

are the most temperature-sensitive species likely to be present in mixed-conifer 

zones. Bull trout occupy the coldest freshwater habitats of all salmon and trout 

species and these habitats are predicted to be severely affected by climate change 

in coming decades (Isaak et al. 2010, Rieman et al. 2007, Wenger et al. 2011). Bull 

trout life histories include migratory forms that spawn and rear in cold streams 

close to headwaters, then migrate downstream to larger rivers where they live 

as adults prior to spawning (“migratory”) or migrate to lakes following rearing 

(“adfluvial”). Fragmentation of cold water habitats by stream warming can increase 

physiological stress to bull trout and decrease interconnectivity of adequate spawning and rearing aggregations. In the “resident” life history form, bull trout remain 

in cold headwater streams for spawning and rearing, and as adults. Thus, they 

are subject to these physiological stressors at all life stages. Cutthroat trout are 

also common to upland streams in mixed-conifer forests of the eastern Cascades. 

Management for the persistence of these and other coldwater fish species in the 

face of climate change should again focus on maintaining strong, genetically 

diverse populations in well-connected stream networks. This may mean road 

management as a means of addressing climate change, by increasing passage and 

opening stream networks. In small streams within mixed-conifer watersheds of the 

Wenatchee River sub-basin, cutthroat trout density and total biomass are limited 
91

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

by higher flows (fig. 36).2 Thus, changing flow regimes as a result of precipitation 

and snowmelt-timing shifts can potentially have consequences for the persistence 

of populations of this species.

0.4

0.3

0.2

0.1

0

Density (m-2)

0 0.1 0.2 0.3 0.4 0.5 0.6

Current speed (m s-1)

0.4

0.3

0.2

0.1

0

Biomass (g m-2)

0 0.1 0.2 0.3 0.4 0.5 0.6

Flow (m s-1)

Figure 36—(Left) Cutthroat trout (Oncorhynchus clarki) density as a function of current velocity in habitat units (usually pools) 

distributed among six first-order streams in moist mixed-conifer forests in the Wenatchee River Basin (Washington, USA). Decreasing 

linear relationship was significant with much unexplained variation (F1,43 = 7.75, p = 0.008, r2 = 0.133). (Right) Cutthroat trout biomass 

as a function of current velocity in habitat units (usually pools) distributed among six first-order streams in moist mixed-conifer forests 

in the Wenatchee River Basin (Washington, USA). Decreasing linear relationship was significant with much unexplained variation 

(F1,43 = 8.34, p = 0.006, r2 = 0.143) (see footnote 2).

2

 Bennett, R.L.; Polivka, K.M. [N.d]. Factors important to monitoring of headwater fish 

populations and possible effects of landscape features. Manuscript in preparation. On file 

with: Karl Polivka, Pacific Northwest Research Station, Forestry Sciences Laboratory, 1133 

N. Western Ave., Wenatchee, WA 98801.

Active management can restore a full spectrum of ecological patterns 

and processes. Long-term restoration and maintenance of the physical, biotic, 

and ecological processes that are important to maintaining diverse terrestrial 

and aquatic systems requires strategies that go beyond simply treating fuel 

accumulations, attempting to prevent high-severity fires, or attempting to 

maintain existing fish strongholds. The most effective means to minimize negative 

consequences of expected climate change, and related effects on aquatic systems, 

is to protect the evolutionary capacity of these systems to respond to disturbance. 

In this light, management would focus on protecting relatively undisturbed aquatic 

habitat, and, where necessary, restoring habitat structure, the processes that 

support it, and the life history complexity of native species, to the best practical 

extent (Gresswell 1999). Restoring degraded aquatic ecosystems requires a similar 

perspective. To conserve or promote resiliency in aquatic (as in terrestrial) systems, 
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GENERAL TECHNICAL REPORT PNW-GTR-897

land managers can turn their focus to conserving and restoring the physical and 

biological processes and patterns that create and maintain diverse networks of 

habitats and populations, rather than engineering the condition of the habitats 

themselves (Benda et al. 2003, Ebersole et al. 1997, Frissell et al. 1997, Gresswell 

1999, Minshall 2003, Naiman et al. 2000, Rieman et al. 2003). This means that 

management is capable of restoring (1) natural patterns in the timing and amount 

of stream flows (Poff et al. 1997); (2) natural production and delivery of coarse 

sediment and large wood to streams (Beechie and Bolton 1999, Meyer and Pierce 

2003, Reeves et al. 1995); (3) riparian communities that function as sources of 

organic material, shade, and stream buffering (Gregory et al. 1991); (4) streams, 

flood plains, and hyporheic zones that are reconnected (Naiman et al. 2000); and 

(5) habitats that are required for the full expression of native life history strategies, 

gene flow and variability, and demographic support among populations (Dunham 

et al. 2003, Gresswell et al. 1994, Healey and Prince 1995, Poole et al. 2001, 

Rieman and Dunham 2000; Rieman et al. 2003, Roghair et al. 2002). Management 

maintains forests and streams that can respond to and benefit from disturbances 

across a broad range of event sizes and intensities, rather than minimizing the threat 

of the disturbance. 

Logical priorities for restoration activities emerge from an evaluation of the 

changes and constraints imposed by these changes (e.g., Beechie and Bolton 1999, 

Luce et al. 2001, Pess et al. 2002). Habitat loss and fragmentation, channelization, 

chronic sediment inputs, accelerated erosion, and changes in hydrologic regime 

(Lee et al. 1997, NRC 1996) are all problems that merit attention. However, restoring physical connections among aquatic habitats may be one of the most effective 

first steps to restoring productivity and resilience of many native fish populations 

(Rieman and Dunham 2000, Roni et al. 2002), given that network connectivity is 

a key component of the adaptive response by fish to disturbances (Burton 2005). 

Eliminating the threat of large and severe disturbance may be insufficient to prevent 

local fish population extinctions in many streams (Dunham et al. 2003, Rieman et 

al. 2003). 

The geographic location and sensitivity of watersheds can be used to guide 

priority setting for management actions (Rieman et al. 2000, 2010). From an aquatic 

conservation and restoration perspective, priorities for active vegetation and fuels 

management occur as follows: 

Priority 1. Watersheds in which the threat of extensive, high-severity fire is 

high and local populations of sensitive aquatic species are at risk because they 

are isolated, small or vulnerable to invasion of exotic fish species (Dunham et al. 

2003, Kruse et al. 2001). In these instances, the first priority for management is to 

restore connectivity among patches of favorable fish habitat (Dunham et al. 2003, 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Rieman et al. 2003). Where this is impractical, active forest management to reduce 

the severity and impact of potential fires could be an important short-term strategy 

(Brown et al. 2001, Rieman et al. 2003). 

Priority 2. Watersheds in which there is little to lose, but much to gain. In some 

watersheds, habitat degradation is extensive and remaining native fish populations 

are depressed or locally extinct. Watersheds that are heavily roaded and influenced 

by past intensive management often contain forests vulnerable to severe fires 

(Hessburg and Agee 2003, Rieman et al. 2000). Existing road systems can initially 

facilitate understory vegetation treatments and fuel reduction, and can subsequently 

be removed, moved, or improved to reestablish hydrologic and biological connectivity (e.g., Roni et al. 2002). Here, short-term risk of ground-disturbing activities may 

be offset by the potential long-term benefit of reconnecting and expanding habitats 

and populations. In many of these locations, ongoing treatment with fire will likely 

be needed. 

Priority 3. Watersheds in which sensitive aquatic species are of limited significance. Given that the vulnerability of dry and MMC forests to high-severity 

fire is associated with lands that have been intensively managed (and absent any 

subsequent composition or stocking management following treatment), the need 

for active fire and fuels management now may be greatest in areas where aquatic 

ecosystems and related physical processes have been most significantly altered 

(Rieman et al. 2000). In some locations, complete restoration of all native plants 

and animals may be impractical. These are logical places to experiment with 

active management, where learning can proceed without taking unacceptable risks 

(Ludwig et al. 1993; see Rieman et al. 2010 for an example).

Management for climate change requires consideration of dynamic hydrologic 

simulations that are used to represent climate change scenarios (e.g., see Hamlet et 

al. 2005, Miller et al. 2003). These must relate sensitivity of models and inferences 

to the main assumptions about climate change, and the low-frequency climate 

variability that is assumed (e.g., decadal and longer scale fluctuations). Additionally, dialogue between landscape ecologists and hydrologists will be necessary to 

integrate the effects of climate change on watersheds in MMC forests and how 

these will be transmitted across the terrestrial-aquatic ecotone to stream habitats. 

In other words, climate will affect fire frequency and intensity, and management 

options for aquatic habitats will require consideration of processes discussed above 

and how the ecological outcome is related to them (Bisson et al. 2003). Landscape 

heterogeneity will contribute to the issues faced on the ground by managers in 

MMC ecosystems throughout the interior northwest (Rieman et al. 2003).
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GENERAL TECHNICAL REPORT PNW-GTR-897

There will be key uncertainties to consider in the management of aquatic 

habitat in MMC landscapes as well. Variable incidences of fire, variable need 

for fuels treatment, variable current quality of aquatic habitat, and management 

tradeoffs between human well-being (property, resources) and conservation 

all increase the complexity of management decisions (Bisson et al. 2003). 

Establishment of an effective adaptive management program will incorporate all 

of these considerations, as well as the spatial and temporal scale. Specific areas 

might require a more explicit management approach, whereas across the entire 

MMC forest ecosystem, a more generalized approach based on existing research 

might be effective (Bisson et al. 2003). Success will depend on continued 

dialogue between landscape ecologists, aquatic ecologists, and forest managers. 

Also stakeholders in the public should be asked to consider the scientific 

recommendations and to participate in further development of management 

and research objectives.

Riparian habitats—

There are relatively few studies that focus specifically on the historical disturbance 

regimes and structure and composition of riparian zones of mixed-conifer forests. 

The little that we do know comes from what can be gleaned from the studies of 

Agee (1988, 1994), Camp (1999), Camp et al. (1997), Everett et al. (2003), Fetherston et al. (1995), Garza (1995), Gregory et al. (1991), Gresswell (1999), Naiman and 

Decamps (1997), Naiman et al. (1993, 1998), Olson (2000), Olson and Agee (2005), 

Skinner (1997), Taylor and Skinner (1998, 2003), and Wright and Agee (2008). With 

the exception of low-gradient stream reaches (e.g., ≤5 degrees of in-stream slope 

angle), the fire regimes of riparian zones track fairly well with those of the adjacent 

upslopes. In contrast, the disturbance regime of low-gradient and often fish-bearing 

reaches tracks with the hydrologic regime. Low-gradient reaches were often depositional zones during flood events, with intact flood plains, and often supported 

hardwood tree and shrub vegetation cover. Disturbance in these environments was 

typically driven by flooding and ice flows, and their spatial and temporal variability, 

rather than wildfires, although wildfires do burn through these areas. 

Gaining a better understanding of the historical disturbance regimes and vegetation patterns of riparian zones is a fertile area of research. The existing datasets 

of the Interior Columbia River Basin mid-scale assessment (Hessburg et al. 1999a, 

2000a) provide extensive reconstructions of now nearly 400 subwatersheds whose 

riparian zones could be reevaluated to provide further insights on successional 

patterns and historical fire severity.

We also know that riparian areas are key wildlife habitats in interior dry forests 

because of the presence of free water, cool moist microclimates, and soil moisture 

Riparian areas are 

key wildlife habitats 

in interior dry 

forests because of 

the presence of free 

water, cool moist 

microclimates, and soil 

moisture that supports 

diverse vegetation. 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

that supports diverse vegetation (Lehmkuhl et al. 2007b, 2008). Small mammals 

are more diverse in dry forest riparian areas compared to adjacent uplands. Several 

species, such as the water shrew (Sorex palustris), are associated with free water, 

whereas species typical of wet or mesic forests become obligate riparian species as 

the surrounding upland vegetation becomes dryer (Lehmkuhl et al. 2008). Forest 

birds are no more diverse in riparian areas than in adjacent uplands, but the composition of birds differs with the addition of many riparian obligate species associated 

with deciduous trees, dense shrubs, and herbaceous vegetation (Lehmkuhl et al. 

2007b). 

Postfire riparian conditions can have long-term effects on aquatic biota owing 

to changes in temperature and sedimentation according to local geomorphology and 

burn severity. In fish-bearing streams of Idaho, the intensity of fire determined the 

density and age structure of rainbow trout (Dunham et al. 2007). Relative to controls, 

streams adjacent to habitats that burned showed relatively more rapid growth of 

age 1+ rainbow trout, an effect that was augmented in streams that were physically 

reorganized by erosion and sedimentation following the fire (Rosenberger et al. 

[N.d.]). This study ranged from lower-elevation dry forest, to elevations containing 

MMC and subalpine forest in the Boise River basin. These observations are thus 

relevant to management strategies in mixed-conifer forests at higher elevations.

Human Impacts to Moist Mixed-Conifer Systems: 

Influences of the Last 100 to 150 Years

Humans have inhabited parts of eastern Oregon and Washington for more than 

10,000 years. Native American communities developed many land management 

practices to serve their needs for sustenance and used fire extensively in woodland 

environments east of the Cascades (Agee 1993; Langston 1995; Robbins 1997, 1999; 

Robbins and Wolf 1994; White 1983, 1991, 1992, 1999). However, there is limited 

knowledge of the impacts of their management on MMC forests (Whitlock and 

Knox 2002). 

With the arrival and settlement of Euro-Americans in the early 1800s came 

another wave of human impacts. Key change agents included initial widespread 

timber harvests, highly effective fire prevention and suppression (largely since 

the 1930s), extensive sheep and cattle grazing and livestock fencing, development 

of extensive road and railroad networks, subdivision of regional landscapes by 

ownership, widespread and repeated timber harvest entry via selection cutting and 

clearcut logging, conversion of native grasslands and shrublands to agricultural uses, 

and urban development. As a result, today these forests neither resemble nor function 

as they once did 100 or 200 years ago.
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GENERAL TECHNICAL REPORT PNW-GTR-897

Changes to the landscape that naturally flowed from these impacts include:

• A highly fragmented range of forest patch sizes, stemming from 4, 8, and 

16 ha (10, 20, and 40 acre) treatment areas and from other land uses near 

urban areas. The resulting patchiness differed greatly from the original 

spatial pattern of the landscape. In some places, patches created by repeated 

harvesting entries created homogenous forest with a skewed species 

composition and more uniform age and size classes. The original mosaic, 

more of a gradient of seral stages created by the complex patterns of fire 

and other tree mortality factors, included an array of different sized patches 

and a full complement of seral or successional stages. 

• After regeneration harvests, a more homogenized forest structure emerged, 

in which treatments drove stand structure and composition toward a single 

cohort and commercially desired species. After selection cutting, stand 

structure moved toward multiple cohorts because of continuous regeneration and release (some stands were entered several times), and species 

composition moved toward domination by shade-tolerant species in dense 

multilayered arrangements.

• A simplified vegetation mosaic was created by removal of large, firetolerant trees over repeated harvest entries, which typically left many 

smaller and fewer large trees. The result was ever increasing density and 

a surplus (in comparison with the native disturbance regimes) of young 

and mid-aged forests. 

• A shift from fire-tolerant to intolerant tree species composition (timber 

harvest removed large ponderosa pine, Douglas-fir, western larch, western 

white and sugar pine [Pinus lambertiana Dougl.], and regenerated grand fir, 

white fir, Douglas-fir, and subalpine fir dominated stands). 

• An increased vulnerability to large and severe fires, insect outbreaks, 

and disease pandemics. 

• Fewer grasslands and shrublands. 

Management activities have also had a profound effect on the spread of nonnative species, especially in the dry rangeland and forest ecosystems. As the 

climate continues to change, conditions for spread of some nonnative invasive (e.g., 

cheatgrass [Bromus tectorum]) and native invasive (e.g., barred owl) species will 

improve. Despite substantial efforts to control invasive species in the United States, 

the threat will remain high in coming years unless significant steps are taken to 

slow the advance of invasive plants and animals.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 37—Timber harvest and road development over the last 100 years have had an impact on 

the spatial configuration of mixed-conifer forests in eastern Oregon and Washington. The upper 

image shows a portion of the Umatilla National Forest without stand management, fragmentation 

with land ownership, and roads. The lower image shows the effects of land ownership, roads, and 

harvest units on forest pattern. Images are from Google EarthTM. 

Timber Harvest and Associated Activities

Timber harvest and road development over the last 100 years have had a significant 

impact on the landscape patterns of MMC forests in eastern Oregon and Washington (fig. 37). Harvest activity was quite intense for nearly five decades beginning 

at the start of World War II. Clearcutting, selective harvesting, and subsequent 

planting for reforestation created substantial areas of structurally simple early- to 

mid-aged stands. Present-day stand structure of these previously harvested areas is 
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GENERAL TECHNICAL REPORT PNW-GTR-897

predominantly even-aged where regeneration harvesting was practiced and unevenaged where selection cutting was more common, with tree species and genetic 

compositions that are often not particularly well-adapted to the environment. Large 

and old live and dead trees (snags) are conspicuously absent from many forests 

(Churchill et al. 2013; Franklin and Johnson 2012; Hessburg et al. 2003, 2005; 

Larsen and Churchill 2008, 2012; Merschel 2012). 

Historical replanting at many sites used maladapted seedling stock from distant 

seed sources, and frequently with species compositions that were not ecologically 

appropriate for the site conditions (e.g., overly high proportions of economically 

important ponderosa pine and Douglas-fir). Seed collection zones were not yet 

established and there was only rudimentary understanding of the relationships 

linking seed provenance adaptation to particular site conditions. Prior to replanting, 

broadcast burning treatments were often employed. If omitted, significant surface 

fuel accumulations were often left behind (Agee 1998, Hann et al. 1997, Hessburg 

et al. 1999a, Huff et al. 1995). These and others factors have limited the function 

of some present-day MMC forests and the ecosystem services that can be obtained 

from them. Some of the post-harvest stands across this region contain large (more 

than about 53 cm [21 in] d.b.h.) young trees with species compositions and stand 

structures that may succumb to bark beetles or fire, and may benefit directly from 

manipulation of tree species composition and density.

Since the early 1990s, when certain management constraints (e.g., the “eastside 

screens”) were adopted, timber harvest has been scaled back by about 90 percent. 

Currently, the scale and scope of active management focuses on a limited number 

of cautiously selected locations, primarily for the purposes of restoring ecological 

processes and reducing fuel loads. 

Fire Exclusion and Natural Fire Dynamics

Fire frequency in the region declined because of land-use changes in limited areas 

as early as 1880 or 1890. By 1900, fire frequency in dry forest types was in sharp 

decline (Everett et al. 2000; Haugo et al. 2010; Hessburg et al. 1999a, 1999c, 2000a, 

2005, 2007; Hessl et al. 2004; Heyerdahl et al. 2001, 2008; Wright and Agee 2004), 

resulting in further changes to forest structure and composition. In the absence of 

fire, forest density increased, the role of shade-tolerant tree species expanded, and 

fuel loads have increased (Baker 2012; Everett et al. 1994; Hessburg et al. 2000b, 

2003, 2005; Huff et al. 1995; Lehmkuhl et al. 1994; Merschel 2012; Perry et al. 

2011). Not coincidentally, human population densities have increased rapidly as 

many people prefer to live at the lower forest ecotone. The amount of area classified 

as wildland-urban interface (WUI) has increased dramatically in recent decades 

(Gude et al. 2008, Radeloff et al. 2005). 

In the absence of 

fire, forest density 

increased, the role of 

shade-tolerant tree 

species expanded, 

and fuel loads have 

increased.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Departure from historical fire regimes—

Land use activities and fire-suppression efforts from the early 20th to early 21st

centuries have been effective at controlling small fires, eliminating the landscape 

patchiness that was historically important for interrupting fire flow at large spatial 

scales (Moritz et al. 2011, Perry et al. 2011). Large wildfires today typically result 

from rare or extreme weather or climatic events (Littell et al. 2009, Moritz et al. 

2011). That was also the case historically. The significant difference associated with 

20th century vegetation and climate change is the increase in frequency of very 

large (>10,000 ha) wildfires in many ecoregions of the West as a result of both more 

flammable landscapes and changing weather conditions. Owing to their increasing 

frequency and size, some large wildfires may synchronize large areas of the mixedconifer landscape, setting the stage for more large and severe fires in the future. 

This happens because large fires, especially those dominated by crown-fire effects, 

can simplify and homogenize landscape patterns of species composition, tree size, 

age, density, and layering.

However, this is not always the case. A recent study in California found that 

some wildfires can achieve ecological and management goals by reducing landscape-scale fire hazard and increasing forest heterogeneity (Miller et al. 2012). This 

is likely to be true when the pattern and dispersion of fire severity and fire event 

patches are more or less consistent with the native fire and climatic regimes. We 

note here that despite referenced changes in fire regimes, many contemporary fires 

are still substantially dominated by mixed-severity fire, and the building blocks for 

landscape restoration are readily apparent. One can still observe the interactions of 

bottom-up, local (e.g., stand and landscape structure, topography), and top-down 

spatial controls on fire extent and fire severity (Perry et al. 2011). 

Grazing

Sheep and cattle entered the region with the first settlers, but the earliest of them 

focused on agriculture, and their herds were typically small, including just enough 

livestock to work and support their family farms. Cattlemen initially believed 

that their stock could survive the harsh winters, and by 1860 there were at least 

200,000 head of cattle in the region. A severe winter in 1861–1862 killed many 

cattle (Galbraith and Anderson 1991). Severe winters occurred again in 1880–1881 

and in 1889–1890, after which most cattlemen recognized that shelter and feed were 

required for a sustainable operation. 

By the late 1880s, severe grazing by cattle left the rangelands stressed (overgrazed). Large cattle herds also grazed adjacent dry forests and nearby grassy riparian zones. Because cattle require a lot of water, they preferred to graze the riparian 

zones, creek bottoms, and wet meadows that supported lush grasses through the dry 
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GENERAL TECHNICAL REPORT PNW-GTR-897

summers, and provided a ready supply of water. Riparian zones constitute 1 to 4 

percent of the land area of eastern Oregon and Washington national forests (Kauffman 1988), yet supply more than 80 percent of the grasses and herbs consumed by 

livestock (Roath and Krueger 1982). 

Introductions of sheep, which require less water and are capable of using 

varying rangeland conditions, boomed in the mid- to late 1880s coincident with the 

decline in cattle. Eventually sheep numbers outstripped cattle, and violent conflicts 

often arose between Basque and Mormon sheepherders and resident cattlemen. The 

battles were the fiercest in Crook, Lake, Wheeler, and Deschutes Counties in southcentral Oregon, where 8,000 to 10,000 sheep were killed per year for several years 

(Galbraith and Anderson 1991). Extensive grazing by sheep left native bunchgrasses 

and forbs in worse condition than was caused by cattle grazing. By the late 19th century, numerous exotic plants such as the bull and Canada thistles (Cirsium vulgare

and C. arvense), cheatgrass, Dalmation and yellow toadflax (Linaria dalmatica and 

L. vulgaris), diffuse and spotted knapweeds (Centaurea diffusa and C. maculosa), 

and leafy spurge (Euphorbia esula) had become established in the region (Hann et 

al. 1997; Langston 1995; Wissmar et al. 1994a, 1994b).

Grazing permits and fees were required on national forest lands beginning 

in 1906, although grazing intensity increased until the 1920s (Wilkinson 1992). 

Congress approved the Taylor Grazing Act of 1934, which regulated grazing on 

the public domain (later, Bureau of Land Management lands) through the use of 

permits; subsequently, cattle and sheep numbers declined. Recent assessments of 

grassland condition suggest that grasslands are slowly recovering from some of the 

impacts of historical grazing, and current conditions are perhaps the best they have 

been in 100 years (e.g., see Harvey et al. 1994, Johnson et al. 1994, Skovlin and 

Thomas 1995). However, because of countless nonnative plant species introductions, some changes in native plant community structure and productivity are likely 

permanent (Lehmkuhl et al. 2013). There is ongoing public debate over whether 

livestock grazing on public lands should be continued under the Taylor Grazing Act 

(e.g., see Belsky et al. 1999, Beschta et al. 2012). Although public land managers 

have made steady progress in reducing cattle impacts to riparian vegetation and 

sediment load in small streams and creek bottoms, this is likely an area for continued improvement.

Land Development

The national forests of eastern Oregon and Washington are largely surrounded 

by private lands. Throughout most of the 1900s, these lands were used for natural 

resource extraction or agriculture. In recent decades, rural home development has 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

expanded. The rapid increase of these exurban homes adjacent to wildlands poses 

a major threat to ecological functioning, fire management, and native biodiversity. 

Exurban development can fragment habitats, create barriers to animal movement 

and other ecological processes, alter natural disturbance, extirpate top predators, 

increase weeds, increase mesocarnivores (medium-sized predators) and diseases, 

and ultimately, cause local extirpation of some native species (Hansen et al. 2005, 

McKinney 2002, Pickett et al. 2001). The presence of homes in the WUI also 

strongly affects fire management options in adjacent national forests, increasing 

the need to suppress fire to protect property and lives, requiring identification and 

mitigation of hazard trees, and increasing firefighting costs.

Theobald et al. (2011) evaluated changes in abundance and connectivity of 

“high-quality” forest patches resulting from land use changes in the Western 

United States. They estimated that land uses associated with residential development, roads, and highways have caused roughly a 4.5-percent loss in area (20 000 

km2

 [7,722 mi2]) of large, unmanaged forested patches, and continued expansion 

of residential land will likely reduce forested area by another 1.2 percent by 2030. 

Projected losses for 2000–2030 were particularly high in Oregon and Washington 

(fig. 38). When considering both patch size and overall landscape connectivity for 

forests across the West in 2000, the most important forested areas were found in the 

Cascades Ecoregion and the Canadian/Middle Rockies Ecoregion, which includes 

the Okanogan Highlands and the Blue Mountains (Theobald et al. 2011). This 

Figure 38—For biomes in Oregon and Washington, the model results among scenarios indicate 

that Rocky Mountain subalpine conifer in the Blue Mountains and Cascade Range will undergo 

the greatest loss in area. Data from Rehfeldt et al. (2012).

90

80

70

60

50

40

30

20

10

Remaining unchanged 

0

(percent)

Oregon coastal conifer

Cascade-Sierran montane conifer

Rocky Mountain montane conifer

Cascade-Sierran subalpine conifer

Rocky Mountain subalpine conifer

Interior cedar-hemlock

Great Basin shrub-grassland

2030

2060

2090
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GENERAL TECHNICAL REPORT PNW-GTR-897

analysis illustrates the high contribution to subcontinental forest connectivity made 

by forests in Oregon and Washington, and the vulnerability of this connectivity to 

future land use changes. 

Climate Change

Climate change is affecting MMC forests in eastern Oregon and Washington 

through changes that include warmer temperatures (Mote and Salathé 2010) and 

snowpack declines (fig. 39; Mote 2003, Mote et al. 2005). Over the next 100 years, 

because CO2 concentrations are projected to rise, these impacts will likely increase 

in magnitude and extent over the region (Littell et al. 2010). Impacts to terrestrial 

ecosystems include increased fire frequency and severity, increased susceptibility 

to some insects and diseases (Fettig et al. 2013, Preisler et al. 2012), and increases 

in the presence of some invasive species (CIG 2009). Regionally, increased summer temperature and decreased summer precipitation and snowpack (Cayan et al. 

2001) are projected to result in a doubling of the area burned by fire by the 2040s 

and a tripling by the 2080s (CIG 2009). Changes in the length and timing of seasons, especially the growing season, the timing of bud break (phenology), and the 

seasonal availability of soil moisture are expected to produce large positive and 

negative shifts in forest growth, with a net effect of increased forest mortality in 

the eastern Cascades (Choat et al. 2012, Grant et al. 2013, Williams et al. 2012). 

In addition to the general regional changes in temperature and precipitation 

predicted by various regional models there is the likelihood that change at the local 

scale could be quite variable owing to high variability in physiographic environments where MMC forests are found (Daly et al. 2007). While most areas may 

become warmer, some may become moister and others drier, particularly during 

certain seasons of the year. Canyon bottoms may remain cool due to accentuated 

cold air drainage. 

For wildlife, changes in climate and vegetation will impact habitat characteristics, reproductive success, and food and water availability. These changes will 

alter species assemblages and distributions, migration routes, interactions with 

competitors and predators, and may impact population viability for many species 

(Staudinger et al. 2013). Impacts may be particularly severe for currently rare or 

endemic species with restricted distributions (Parmesan 2006). Anticipated changes 

to wildlife include (1) the susceptibility of high-elevation habitats and species 

dependent on snowpack (e.g., wolverine [Gulo gulo] for the Blue Mountains), (2) 

impacts on wetlands and associated species, especially those sensitive to water temperature (e.g., tailed frog [Ascaphus montanus]), and (3) phenological mismatches 

for migratory birds and other species (Parmesan 2006). Changes are expected 

to happen more quickly than species’ potential to adapt (Staudinger et al. 2013). 

In addition to general 

regional changes 

in temperature and 

precipitation predicted 

by models is the 

likelihood that change 

at the local scale could 

be quite variable owing 

to high variability 

in physiographic 

environments where 

moist mixed-conifer 

forests are found.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 39—Historical snowpack decline in the Pacific Northwest region 1950–2000 (Mote 2009).

Maintaining landscape patterns that allow species to move in response to changes 

in climatic and habitat conditions may be particularly important for conservation 

of sensitive species (Heller and Zavaleta 2009, Nuñez et al. 2013).

Change in climate and disturbance: 1950 to present— 

El Niño/Southern Oscillation (ENSO) remains the most important coupled oceanatmosphere phenomenon to cause climate variability on seasonal to interannual 
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GENERAL TECHNICAL REPORT PNW-GTR-897

time scales in the Pacific Northwest. Across decadal timescales, longer-term 

oscillations such as the Pacific Decadal Oscillation (PDO) come into play. The PDO 

was in an extended cool phase from about 1945 to 1976 and in a warm phase from 

1977 to 1998 (Mantua and Hare 2002, Mantua et al. 1997, Mote et al. 2003, Waring 

et al. 2011). Minimum temperatures have increased most rapidly in the semiarid Columbia River basin and the Great Basin, and in semi-arid portions of the 

Okanogan Highlands, but have changed relatively little west of the Cascade Crest 

and in the Blue Mountains (fig. 40). Mean average temperature has been observed 

to have increased by 0.8 °C (1.50 °F) since 1900 (Mote and Salathé 2010). Climate 

Figure 40—Changes in minimum temperature throughout the Pacific Northwest. Source: 

Waring et al. 2011.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

forecasting models, when averaged, project increases in annual temperature of 1.1 

°C (2.0 °F) by the 2020s, 1.8 °C (3.2 °F) by the 2040s, and 3.0 °C (5.3 °F) by the 

2080s, compared with the average temperature from 1970 to 1999. 

Trends in historical and projected future changes in precipitation in the Pacific 

Northwest are less clear than for temperature (Stephens et al. 2010). For example, 

precipitation in the Pacific Northwest has increased by 13 to 38 percent since 1900, 

but has shown substantial interannual and interdecadal variability during the 20th

century (Mote et al. 2003), which current climate models are unable to simulate 

under future warming scenarios (Ault et al. 2012). Some, but not all models predict 

slight future increases in annual precipitation (1 to 2 percent in 2030 to 2059, and 

2 to 4 percent in 2070 to 2099; Littell et al. 2009). 

The ecoregions of eastern Oregon and Washington (notably the eastern Cascades and the Blue Mountains) have a Mediterranean type of climate characterized 

by warm dry summers and cool moist winters. The lack of summer precipitation 

coupled with earlier springs and later winters suggest increased vulnerability of 

forests and forest associates to climate change. Anticipated changes in fire regimes 

in the Northwest United States is a direct result of these changes in climate (Westerling et al. 2006). The following summarizes the key climate change projections and 

impacts to moist mixed conifer forests in the Pacific Northwest region (CIG 2009, 

IPCC 2013, Mote et al. 2005).

Projected outcomes:

• Reduced snowpack amounts (up to 50 percent projected decline)

• Increased rain on snow

• Warmer air temperatures (up to 3 °C by 2080)

• Change in the timing of snowmelt (earlier)

• More climate extremes

Projected impacts to moist mixed-conifer forests:

• Reduced soil moisture

• Increased drought stress

▪ Increased fire intensity, severity, and frequency

▪ Increased susceptibility to insect attack

• Phenologic shifts (earlier onset of budbreak, longer growing season)

Climate change impacts on forest ecosystems—

Climate change influences on forest tree species are a function of the ecophysiological tolerances unique to each species. Waring et al. (2011) used a process-based 

forest model to estimate changes in tree species competitiveness (influenced by a 

variety of ecological factors) between 1950–1975 and 1995–2005 based on climate 
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GENERAL TECHNICAL REPORT PNW-GTR-897

effects on simulated leaf area index (LAI). Although LAI may not be the prime 

indicator of a conifer tree’s capacity to respond to changing climates, it provides 

an index of potential response. Across their western North America study area, 

they found a significant decrease in the competitiveness of over 50 percent of the 

evergreen species in ecoregions in the northern and southern portions of the study 

area. Within Oregon and Washington, competitiveness changed little in the West 

Cascades and was moderately reduced in the East Cascades, the Okanogan Highlands, and the Blue Mountains (fig. 41). Furthermore, regions exhibiting reduced 

competitiveness under climate change scenarios were predicted to experience 

higher rates of disturbance by insects, fire, and other factors (Waring et al. 2011). 

These changes in climate are also projected to influence the area of suitable 

climate for vegetation types differently and shift vegetation assemblages over the 

landscape. Rehfeldt et al. (2012) developed climate envelope models for biomes 

of North America and projected change in area and distribution under six climate 

change scenarios. However, there is still debate about whether this approach 

realistically captures physiological tolerances of forest species (Loehle 2011). 

Figure 41—Map presenting the proportion of 15 coniferous species predicted as no longer well-adapted in the years 1995–2005 

compared with baseline conditions (1950–1975). From Waring et al. (2011).
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

We acknowledge that limitations to the use of climate envelope approaches for 

modeling potential species distribution changes are well known (Fettig et al. 2013). 

Nonetheless, modeling approaches provide some insight into the possible magnitude 

and geography of projected changes in species distribution in the coming decades. 

For biomes in Oregon and Washington, model results among scenarios estimate 

that all Oregon Coastal Conifer and Interior Cedar-Hemlock types will undergo 

the least reduction in the areas they currently occupy. Subalpine biomes in the 

Cascades and the Rockies are projected to eventually undergo substantial reduction 

in currently occupied areas, with only 27 percent and 19 percent of these biome 

types remaining. Drier conifer forest area is also forecasted to decline substantially: 

41 percent of Rocky Mountain Montane Conifer, which currently occurs in the 

Okanogan Highlands and the Blue Mountains, is forecasted to remain in 2060. 

Importantly, by 2090, only 12 to 57 percent of the current area is forecasted to have 

climates suitable to the biomes occurring there today, although the rate of decline is 

uncertain. Of course we do not know how extensive the geographic shift in biomes 

will eventually be, because there are many complex ecological interactions that 

will play out over time, and ecophysiological modeling is in its infancy. Current 

models give us an indication of how dramatic the changes could be. Nonetheless, 

some areas currently occupied by subalpine forest in the Cascades, for example, 

will likely become suitable as mixed-conifer forests now found at mid elevations. 

Climate in the Northeast Cascades of Washington becomes suitable for the Coastal 

Hemlock Biome type. Forest areas in the Okanogan Highlands and Blue Mountains 

are largely replaced by climates suitable for the Great Basin Shrub-Grassland type.

Forest productivity is also projected to change under future climates. Productivity is forecasted to increase in what are currently subalpine and alpine zones across 

the region and to decline in the drier forests, which are largely at the lower forest 

ecotone in the East Cascades, Okanogan Highlands, and Blue Mountains (Latta 

et al. 2010). Concomitantly with warmer temperatures, forests may respond to 

increased atmospheric CO2 concentrations through increased water use efficiency. 

However, forest growth response to rising CO2 is less clear than it appears it will be 

for temperature, perhaps because soil moisture availability is expected to decline 

(Peñuelas et al. 2011). Warming may allow some insect species (e.g., some bark 

beetles) to complete extra generations per year, and adult emergence and flight 

activity could occur earlier and last longer. Cold-induced mortality of insects 

during winter may also decrease. For example, model simulations indicate that the 

climatic suitability for mountain pine beetle will increase during the next several 

decades in eastern Oregon and Washington (Bentz et al. 2010, Preisler et al. 2012), 

2
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GENERAL TECHNICAL REPORT PNW-GTR-897

and when combined with current forest conditions (Fettig et al. 2007, Hicke and 

Jenkins 2008), higher levels of tree mortality are expected.

Conversely, there could be some reductions in insect-induced tree mortality 

when warming increases susceptibility to predators, parasitoids, or pathogens. 

Preliminary evidence suggests that warmer conditions might shorten the incubation period (time between infection and mortality) of the baculovirus that limits 

Douglas-fir tussock moth populations (see footnote 2). Given projected warming 

in winter and decreases in precipitation in summer, the impact of western spruce 

budworm will likely decrease in the future relative to the current distributions of 

susceptible forest types in this region (Williams and Liebhold 1995). The insect 

hibernates in winter, and elevated temperatures during this period reduce survival. 

Warming may also change the timing and synchrony of bud break in Douglas-fir, 

which in turn may influence outbreak frequency and severity. Projected climate 

change impacts to MMC forests in the region are likely to be manifest through 

ENSO and other oscillations such as the PDO. Moreover, the multiscale (broadscale and fine topographic) nature by which climate change is likely to manifest 

across the landscape necessitates a multiscale hierarchy such as the one we have 

outlined in previous sections of this synthesis (CIG 2009, IPCC 2013, Mote et al. 

2005):

• El Niño/Southern Oscillation remains the most important coupled oceanatmosphere phenomenon to cause climate variability on seasonal to 

interannual time scales in the Pacific Northwest.

• Projected changes in climate will be manifest at both highly localized 

and broad regional scales for moist mixed-conifer forests.

• Necessitating the need for multiscale, hierarchical approach to address 

future climate change impacts.

Changes in Vegetation

Changes in the structure and composition of forests since Euro-American settlement are well documented (Hessburg and Agee 2003). For example, forests are 

now typically several times denser in most locations than under native fire regimes 

(Camp 1999, Hagmann et al. 2013, Merschel 2012, Perry et al. 2004) (table 5). 

However, one recent study (Baker 2012) has indicated that these forests were 

“generally dense” (100 trees per acre [275 trees per hectare]) in the late 1800s and 

suggested that the amount of change in the structure of these forests and the need 

for density reduction has been overstated. It is unclear how density estimates from 

the Baker study apply to MMC forests, which are a subset of the ponderosa, dry 

mixed-conifer, and lodgepole pine stands that he sampled, as less than 1 percent of 

the trees were identified as white or grand fir. This suggests that either his records 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 5—Historical and current tree density (trees per hectare, TPH) estimates in dry and moist mixed-conifer forests

Forest Historical Current

Region description density density Source Notes

Mean ± standard deviation (range)

 and time period

Eastern slope of the Mixed-dry 64 ± 22 286 ± 130 Hagmann et al. 2013 Historical density is reported for trees >15.2 cm diameter at

Cascade Range, (14–156) (109–572) breast height (d.b.h.) based on timber inventory transects that

southern Oregon 1914–1922 1997–2006 covered 10 to 20 percent (6646 ha) of a 38 641 ha study area

of ponderosa pine and dry and moist mixed-conifer forest.

Mixed-moist 78 ± 37 233 ± 90 Current density is reported for trees >15 cm d.b.h. and is based

(0–296) (104–378) on 24 current vegetation survey plots within the sample area.

1914–1922 1997–2006 Inventory plots were assigned to habitat types using mapped

potential vegetation types (ILAP).

Warm Springs Indian Mixed-dry 65 ± 25 NA Hagmann, Historical density is reported for trees >15.2 cm d.b.h. based on

Reservation, eastern (6–188) unpublished timber inventory transects that covered 20 percent (32 293 ha)slope of the Cascade 1922–1925 data, 2013a of a 158 354 ha study area of dry and moist mixed-conifer

Range, Oregon forest. Inventory plots were assigned to habitat types using

Mixed-moist 70 ± 32 NA mapped potential vegetation types (ILAP).

(0–289)

1922–1925

Austin-Whitney Tract Mixed-dry 120 NA Munger 1912 Density is reported for trees >10 cm d.b.h. Munger specifically 

in the Blue Mountains 1910 (summarized by inventoried “well stocked” stands.of northeast Oregon David Powell)

Crawford Creek Tract Mixed-dry 126 NA

in the Blue Mountains 1912near Unity, Oregon

Lookinglass Creek Mixed-moist 162 NA

Tract in the Wallowa 1910Mountains of northeastOregon

Eastern slope of the Mixed-dry 136 NA Munger 1917 Density is reported for trees >10 cm d.b.h. Munger specifically

Cascade Range, 1912 inventoried “well stocked” stands.central Oregon

Eastern slope of the Mixed-conifer 275 NA Baker 2012 General land office survey records were used to estimate stand

Cascade Range, Late 1800s density. Estimates for a 398 346 ha area are based on 11 856

central Oregon trees marking section and quarter-section corners. Four trees

were used to estimate density at section corners, and two wereused at quarter corners. This inventory area includedlodgepole pine forests, which can have high stand densities.
110

GENERAL TECHNICAL REPORT PNW-GTR-897 Table 5—Historical and current tree density (trees per hectare, TPH) estimates in dry and moist mixed-conifer forests (continued) Forest Historical Current Region description density density Source Notes Mean ± standard deviation (range) and time period Eastern slope of the Mixed-dry 447 ± 186.8 NA Merschel et al. [N.d.] Density is reported for trees >10 cm d.b.h. Sample sites (1.0 ha) Cascade Range, Douglas-fir) ( (227–778) were widely distributed in mature forest mapped in any of central Oregon 14 sample sites the mixed-conifer dry or mixed-conifer dry plant association 2009–2010 groups. The number of sample sites used in each estimate is reported following the reported density. Mixed-dry NA 536 ± 185 (grand fir) (113–825) 16 sample sites 2009–2010 Mixed-moist NA 429 ± 200 (52–900)

24 sample sites

2009–2010

Ochoco Mountains, Mixed-dry NA 274 ± 132

central Oregon (Douglas-fir) (95–533)

26 sample sites

2009–2010

Mixed-dry NA 203 ± 102

(grand fir) (76–430)

19 sample sites

2009–2010

Mixed-moist NA 312 ± 211

(67–799)

26 sample sites

2009–2010

Eastern slope of the Dry and moist 40–80 in 868 Perry et al. 2004 Age and size were sampled for live trees at thirteen 0.2-ha sites.

Cascade Range, mixed-conifer 8 stands,<30 (335–1415) Historical density refers to the number of trees per hectare >150

central Oregon in 5 stands. ~2004 years in age. Current density refers to all trees >5 cm d.b.h.

Refers to trees 

>150 years old.

Eastern slope of the Mixed-conifer- HDSGb —119 HDSG—218 Ohlson and Historical density was estimated using 52 one-tenth-acre plots. 

Cascade Range, dry WDSH—168 WDSH—326 Schellhaas 1999 Authors suggest that changes in fire regime and associated

northern Washington WDTS—315 WDTS—293 changes in structure began in the 1860s and that maximum

CDG—311 CDG—376 density was reached in the mid-20th century. Historical

WMSH—113 WMSH—556 reconstructed densities and current densities are reported

1899 1999 for all trees >12.7 cm d.b.h., and are stratified by different 

Douglas-fir potential vegetation types ranked from most xeric to most mesic. WMSH would correspond to moist mixedconifer potential vegetation types. It had a fire return interval of <19 years. The relatively high historical density in WDTS, a type related to a mixed severity fire that occurred in 1886.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 5—Historical and current tree density (trees per hectare, TPH) estimates in dry and moist mixed-conifer forests (continued)

Forest Historical Current

Region description density density Source Notes

Mean ± standard deviation (range)

 and time period

Eastern slope of the Mixed-dry NA 470 ± 267 M. Reilly, Density is reported for trees >10 cm d.b.h. Density is based on

Cascades Range and (n = 512) unpublished datac forest current vegetation survey (CVS) plots distributed on a 

foothills, Oregon 1994–2004 2.5 by 2.5 km grid (5 km in wilderness areas) throughoutand Washington national forests of Oregon and Washington. Sample sites

include developmental stages ranging from early seral inrecently disturbed areas (logging, wildfire, etc.) to matureold-growth forest. The number of CVS plots used to calculatedensity is reported in parentheses. CVS plots were assigned toPVTs based on ILAP map.

Note: Dry mixed-conifer forests are included because several studies indicate that historical and current disturbance regimes and stand densities of the twosites overlap to a large degree (see table 2). Diameter thresholds, methods of estimation, and spatial coverage used to develop estimates varies among authors.a On file with: Keala Hagmann, School of Environmental and Forest Sciences, University of Washington, Box 352100, Seattle, WA 98195. b Plant association groups with respective plant associations:

HDSG (Hot/Dry/Shrub/Grass):

Pinus ponderosa/Agropyron spicatumPseudotsuga menziesii/Agropyron spicatum

Pinus ponderosa/Purshia tridentata/Agropyron spicatum

Pseudotsuga menziesii/Purshia tridentata/Agropyron spicatum

Pseudotsuga menziesii/Symphoricarpos albus/Agropyron spicatum

WDSH (Warm/Dry/Shrub/Herb): 

Pseudotsuga menziesii/Arctostaphylos uva-ursi

Pseudotsuga menziesii/Arctostaphylos uva-ursi/Purshia tridentata

Pseudotsuga menziesii/Spirea betulifolia var. lucida

WDTS (Warm/Dry/Tall Shrub): 

Pseudotsuga menziesii/Physocarpus malvaceus

Pseudotsuga menziesii/Physocarpus malvaceus/Linaea borealis var. longiflora

WMSH (Warm/Mesic/Shrub/Herb): 

Pseudotsuga menziesii/Symphoricarpos albus

Pseudotsuga menziesii/Symphoricarpos albus/Calamagrostis rubescens

CDG (Cool/Dry/Grass) 

Pseudotsuga menziesii/Arctostaphylos uva-ursi/Calamagrostis rubescens

Pseudotsuga menziesii/Purshia tridentata/Calamagrostis rubescens

Pseudotsuga menziesii/Spirea betulifolia var. lucida/Calamagrostis rubescens

c On file with: Matthew Reilly, Department of Forest Ecosystems and Society, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331.
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GENERAL TECHNICAL REPORT PNW-GTR-897

did not sample much MMC forest or that there were few individuals of these Abies

species present in the late 1800s. Hagmann et al. (2013) examined stand inventory 

records from the 1920s in landscapes that overlap areas sampled by Baker (2012) 

and found much lower tree densities for the same areas. Munger (1917) reported a 

density of 55 large trees per acre for ponderosa pine forest, and 61 in dry mixedconifer forests in the eastern Cascades in the early 20th century. That study characterized dry mixed-conifer stands as open with widely spaced trees, but noted that 

the forests consisted of open stands of mature trees interrupted by treeless areas and 

denser patches of young trees. 

Although total stand densities have increased several fold, the densities of large 

trees (>50 cm [~20 in]) have declined in many areas within older mixed-conifer 

forest areas (excluding clearcut areas) by as much as 50 percent based on a few 

studies (table 3). The decline has been observed in both Oregon and Washington 

and is likely a result of selective logging of large pines and Douglas-firs during the 

20th century. One study from Washington reported increases in the density of large 

trees.3

Heyerdahl showed that fire occurrence in several pine and mixed-conifer forest 

patches in central Oregon strongly declined after 1880, and grand fir establishment 

started to increase in the 1880s and 1890s (Heyerdahl et al. 2001 and unpublished 

data; Merschel 2012). If we assume that the presettlement density of trees in 

mixed-conifer patches was 50 to 100 trees per hectare (20 to 40 trees per acre), then 

current densities for mixed-conifer forests may be two to six times the historical 

densities of some patches. For example, several recent studies have estimated 

current mixed conifer densities at about 200 to more than 300 trees per hectare (80 

to more than 120 trees per acre) (Camp 1999, Merschel 2012, Perry et al. 2004). 

Under the recent disturbance regime of fire suppression and logging of old trees, 

MMC forests often consist of scattered remnants of medium- to large-sized shadeintolerant dominant trees, with medium-sized shade-tolerant co-dominant trees, and 

often several dense layers of intermediate and overtopped or suppressed shadetolerant trees (Oliver and Larsen 1996). Thus, land use and fire regime changes have 

shifted successional pathways from dynamic fine scale mosaics driven by low- to 

mixed-severity fire to coarser grained, more homogenous patch types driven by 

high-severity fire. 

Seed availability, either the absence of seeds of a species or the presence 

of nearby seed sources (e.g., a kind of “mass effects” in which a high rate of 

3

 Ohlson, P.; Schellhaas, R. 1999. Historical and current stand structure in Douglas-fir and 

ponderosa pine forests. Unpublished report. Portland, OR: U.S. Department of Agriculture, 

Forest Service, Okanogan and Wenatchee National Forests.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

propagule input maintains species on sites that are not well suited for reproduction 

or long-term survival) (Shmida and Wilson 1985), can have a strong influence on 

community development, and is often overlooked as a factor in succession. For 

example, fire suppression has led to an increase of grand or white fir in many forest 

environments, which has converted many acres of open ponderosa pine forests to 

dense mixed-conifer forests (Everett et al. 1994, 1997; Hann et al. 1997; Hessburg et 

al. 1999a, 2000a). In many cases, the true firs and Douglas-fir may be establishing 

on sites that are less optimal for their growth only because there are massive 

amounts of seeds in the local landscape (these species dominate the seed rain) 

that swamp out some of the environmental and ecological controls over species 

distributions within a community. The densification of these stands could inhibit 

regeneration of early-seral species such as ponderosa pine and western larch, which 

are an important component of the overstory, and require relatively open conditions 

and frequent disturbance for establishment. In many areas, high-grade logging over 

the 20th century has reduced the densities of these large young forest dominants 

(Harrod et al. 1999), and they will not return to these sites without disturbances 

that open the canopy, reduce the overall seed rain of the shade-tolerant species, and 

reduce stem densities. 

Old-growth forests are one of the most ecologically and socially valuable 

successional stages in the Pacific Northwest (Spies and Duncan 2009), but they are 

also quite variable in structure and dynamics, especially between the west and east 

sides of the Cascade Range. The classic old-growth forests of the coastal portion of 

the Pacific Northwest—fire-infrequent forests that contain large, emergent, longlived conifers (e.g., Douglas-fir) and dense multilayered mid- and understories of 

shade-tolerant trees (e.g., western hemlock)—have analogs on the east side of the 

Cascades. Fire-infrequent old growth on the east side establishes through different pathways and exists under differing conditions. Much of what developed prior 

to the onset of the timber utilization era, beginning in the later part of the 1800s, 

consisted of large old ponderosa pine and Douglas-fir in the upper canopy, with 

occasional western larch and shade-tolerant white/grand fir in the upper canopy and 

white/grand fir filling lower canopy layers (Merschel 2012). However, this old-forest 

type would have been uncommon in the drier, fire-prone landscapes, occupying 

moist, less fire-prone sites. For example, Agee (2003) estimated that only 10 to 

17 percent of MMC forest sites would have supported dense old forests under the 

native fire regime, although some individual watersheds may have had as much as 

20 to 35 percent (Hessburg et al. 1999a, 2000a). 

The composition of patches of old-growth trees on the east side also depended 

very much on topographic position. Solar insolation and soil moisture retention, 
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GENERAL TECHNICAL REPORT PNW-GTR-897

key factors in determining growing potential and relative drought stress, are 

considerably different depending on slope aspect and slope position. Thus the 

species composition and structure of patches of old forest are quite different at the 

bottom of a drainage, where soil moisture and shade enable the growth of mixed 

species of denser, multilayered patches compared with patches on a south-facing 

midslope, which tend to be single layers of more sparse groups of predominantly 

large pines. 

Another important difference between older, structurally diverse, interior MMC 

forest stands is that they do not persist for long periods as westside old growth 

does. It is important to continually recruit forest stands into this older, structurally 

diverse condition because forests on the east side do not stay in that condition. The 

transience of old forest conditions in interior MMC forest is a consequence of the 

unique assemblage of primary disturbances (e.g., fire, insects, and diseases) found 

in these drier landscapes. The dense, multilayered old forests that have developed 

under extended periods of fire exclusion are vulnerable to a host of disturbance 

factors and are unlikely to persist except where local topography, soils, and microclimate are suitable (e.g., sufficient soil moisture). By contrast, the sparser, singlelayered old forests, dominated by large pines, are capable of persisting for as long 

as 500 years.

Historically, the most common expression of old growth would have been a 

“fire climax” (Perry et al. 2008) or old single-story, park-like forest (sensu O’Hara 

1996), where various combinations of large, old, fire-resistant ponderosa pine, 

Douglas-fir, and western larch would occur in the canopy over a relatively open but 

variable and ephemeral understory of pines or shade-tolerant tree species depending on the fire frequency at the site. On sites with longer fire return intervals (>25 

years) dominated by mixed-severity fire regimes, the canopies of the fire-dependent 

old growth would include patches (fractions of an acre to several acres) formed by 

small mixed-severity disturbances from fire or insects and disease. In many landscapes, streamside environments would have longer fire return intervals (>50 years), 

and support old growth stands with larger components of fir in the understories and 

sometimes in the overstories.

Young forest communities may have been altered as well, but we have less 

information about the amounts and patterns of open plant communities maintained 

by high-severity fire, which was a variable component within the mixed-severity 

regime of the mixed-conifer forest. Of special interest, clonal aspen patches, often 

imbedded within mixed-conifer forests, have been heavily affected by fire exclusion 

owing to their relatively short life expectancy (stands begin to deteriorate at 55 to 

60 years of age and are pathologically old and decadent at 90 to 110 years; Bartos 

The composition of 

patches of old-growth 

trees on the east side 

depends very much on 

topographic position. 

Solar insolation and 

soil moisture retention, 

key factors in determining growing potential 

and relative drought 

stress, are considerably different depending on slope aspect 

and slope position.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

2000). Wildfires normally revitalized aspen clones, with some patches sprouting 

10,000 to 20,000 stems per hectare (24,710 to 49,421 stems per acre) in early life 

stages after fires. Ungulate browsing, both wild and domestic, and a host of stem 

cankers, foliar diseases, and insect defoliators naturally thin aspen clones to a few 

hundred stems per hectare after several decades.

Changes in Disturbance Factors: Insects and Disease

The frequency, severity, and scale of insect outbreaks in MMC forests of eastern 

Oregon and Washington vary considerably (table 5), even by species. In short, 

effects on vegetation range from short-term reductions in crown cover (e.g., larch 

casebearer), to modest increases in background levels of tree mortality (e.g., balsam 

wooly adelgid [Adelges piceae]), to regional-scale outbreaks resulting in extensive 

amounts of tree mortality under some circumstances (e.g., Douglas-fir tussock moth 

and western spruce budworm). Of more recent concern is the impact of mountain 

pine beetle outbreaks in the region (see “Animals of the Moist Mixed-Conifer 

Ecosystem”). Wickman (1992) noted that historically the impacts of insects on 

mixed-conifer forests were typically of shorter duration and lower severity than was 

observed in recent decades. A heterogeneous landscape is thought to be more resilient to insect- and disease-caused disturbances (Fettig et al. 2007, Filip et al. 2010). 

Although it is difficult to isolate the confounding effects of recent management 

practices and climatic changes, a more heterogeneous landscape likely ensured that 

most disturbances in MMC forests were more brief and spatially confined in the 

past (Hessburg et al. 1994). This has been well documented for dry mixed-conifer 

forests in the region, and it is likely a similar trend existed for MMC forests as they 

are interconnected with dry mixed-conifer forests that are now substantially modified by fire exclusion and selective harvesting (Hessburg et al. 1994, Lehmkuhl et 

al. 1994). 

Outbreaks of forest diseases caused by native and introduced pathogens are 

generally thought to become more frequent and severe as a result of climate change 

(Sturrock et al. 2011). However, diseases caused by pathogens directly affected by 

climate (e.g., needle blights) are predicted to have a reduced impact under warmer 

and drier conditions. For thorough reviews on the expected effects of climatic 

change on forest pathogens, see Dale et al. (2001) and Sturrock et al. (2011).

Effects of Altered Disturbance Regimes, Land Use, and 

Climate Change on Animal Populations and Habitats

There have been significant changes to fish and wildlife populations associated 

with MMC forests during the last 150 years. The effects of human land uses and 

altered disturbance regimes discussed in previous sections of this report have 
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GENERAL TECHNICAL REPORT PNW-GTR-897

had a significant impact on fish and wildlife populations across this entire area. 

Additionally, climate change has already produced observable changes in animal 

communities in the Pacific Northwest (Hixon et al. 2010), and those changes are 

likely to intensify in the future (Dalton et al. 2013).

Regional landscape assessments over the past 20 years have documented the 

profound effects of historical human use and forest management on mixed-conifer 

and other wildlife habitats of eastern Oregon and Washington (Everett et al. 1994; 

Hann et al. 1997; Hessburg et al. 1999a, 2000a; Lehmkuhl et al. 1994; USDA FS 

1996). The area and condition of grasslands, shrublands, and old forest multistory 

and late-seral single-story forests, and the forest backbone of large residual trees, 

have declined markedly (Hessburg and Agee 2003, Hessburg et al. 2005) (fig. 42). 

At the same time, the area occupied by invasive species, roads, intermediate-aged 

forest, and insect, disease, and fire susceptibility (as indicated by changes in forest 

structure, fuel loading, and crown fire potential) have increased. Habitat trends 

reported in recent wildlife habitat assessments reflect a widespread reduction in 

habitat values relative to historical conditions for wildlife associated with earlyseral, open forest, and postfire habitats (Gaines et al., in press; Suring et al. 2011; 

Wales et al. 2011; Wisdom et al. 2000). Old forest habitat conditions show less 

decline at a regional scale, but patterns are variable across sub-basins.

For example, Wisdom et al. (2000) found that habitat for species associated 

with low-elevation old forest, which includes single-story ponderosa pine forest and 

single- and multistory mixed-conifer forest, has declined in most of eastern Oregon 

and Washington (table 6). The habitat trend for species associated with old forest 

(i.e., forests with multistory stands and large old trees), which spans the elevation 

gradient from low to high, varies across the region from markedly declining in 

the northeastern Cascade Range, to neutral in the southeastern Cascades and Blue 

Mountains, to increasing in the Klamath province. The habitat trend for generalist 

forest mosaic species, which use a broad range of forest cover types and structural 

stages, has been neutral or positive. The habitat trend for young forest species varies 

from highly or moderately negative in the Klamath and Blue Mountain provinces, 

respectively, to positive to neutral in the Cascade Range province (Wisdom et al. 

2000).

Habitat assessments in support of national forest plan revision activities in 

eastern Washington and Oregon have produced results similar to those of Wisdom 

et al. (2000). In their assessment of wildlife habitat and population viability in 

national forests of eastern Washington (the Okanogan-Wenatchee and Colville 

National Forests), Gaines et al. (in press) found that the species whose viability 

had declined most relative to historical conditions were those species sensitive to 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 42—Comparison of an example watershed from the early (ca. 1900, historical) and late (1990s, current) 20th century. Note 

how spatial patterns of fuel loading, crown fire potential, and flame length closely track forest structural conditions: i.e., process 

followed pattern. Maps are of the Peavine Creek drainage, a dry forest subwatershed of Lower Grande Ronde subbasin in the Blue 

Mountains Province displaying historical and current structural classes (A and B), fuel loading (C and D), crown fire potential 

(E and F), and flame length during wildfire (G and H). Fuel loading classes are very low <22.5 Mg/ha; low = 22.5 to 44.9 Mg/ha; 

moderate = 45 to 56.1 Mg/ha; high = 56.2 to 67.3 Mg/ha; very high >67.3 Mg/ha. Crown fire potential classes were a relativized 

index. Flame length classes were very low <0.6 m; low = 0.7 to 1.2 m; moderate = 1.3 to 1.8 m; high = 1.9 to 2.4 m; very high = 

2.5 to 3.4 m; severe >3.4 m (Hessburg and Agee 2003, Hessburg et al. 2005). 
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human disturbances or grazing, and associated with shrub-steppe, early-seral, or 

postfire habitats (e.g., fox sparrow, white-headed woodpecker, western bluebird, 

and sage thrasher [Oreoscoptes montanus]). Species associated with older forest 

conditions (including northern goshawk, pileated woodpecker, and American 

marten) also experienced declines in viability relative to historical conditions, but 

those declines were not as substantial as experienced by the shrub-steppe, early 

seral, or postfire species.

In their assessment of wildlife habitat values in three national forests in northeastern Oregon (the Umatilla, Wallowa Whitman, and Malheur National Forests), 

Wales et al. (2011) found that focal species representative of old forest conditions 

(including goshawk and pileated woodpecker) had current habitat values that were 

generally consistent with historical conditions at a regional scale, while species 

associated with open, large tree forests and early-seral or postfire habitats (including Cassin’s finch [Carpodacus cassinii], white-headed woodpecker, western 

bluebird, fox sparrow, black-backed woodpecker [Picoides arcticus], and Lewis’s 

Table 6—Source forest-habitat trends (1800s to 1995) for families of focal wildlife species in 6th hydrologic 

unit code (HUC) subwatersheds of the interior Columbia River basin in eastern Oregon and Washington 

Percentage of 6th-code watersheds

Province Family name Decreasing Neutral Increasing Trend

Blue Mountains Low-elevation old forest 67 20 13 –

Broad-elevation old forest 47 17 36 0

Forest mosaic 7 15 78 +

Early-seral montane and lower montane forest 53 4 42 –

 Average 43.5 14.0 42.3 0

Northern Cascades Low-elevation old forest 69 24 7 –

Broad-elevation old forest 74 13 13 –

Forest mosaic 17 45 37 0

Early-seral montane and lower montane forest 30 8 63 +

 Average 47.5 22.5 30.0 0

Southern Cascades Low-elevation old forest 56 22 22 –

Broad-elevation old forest 37 15 47 0

Forest mosaic 0 20 80 +

Early-seral montane and lower montane forest 45 13 42 0

 Average 34.5 17.5 47.8 0

Upper Klamath Low-elevation old forest 33 19 48 0

Broad-elevation old forest 7 5 88 +

Forest mosaic 5 7 88 +

Early-seral montane and lower montane forest 98 0 2 –

 Average 35.75 7.75 56.50 0

Note: Trend was determined by >50 percent of subwatersheds decreasing (–) or increasing (+); otherwise, trend was neutral.

Source: Wisdom et al. (2000).
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

woodpecker) generally had experienced declines in habitat values relative to historical conditions. Species sensitive to human disturbances (including wolverine and 

American marten) also experienced declines in habitat values relative to historical 

conditions. Both Gaines et al. (in press) and Wales et al. (2011) noted that the area 

of postfire habitat in eastern Washington and Oregon has increased since 1980, but 

most of it is concentrated in a few watersheds that have experienced large-scale, 

high-intensity wildfire, producing patterns that did not contribute to population 

viability for postfire species at a regional scale as effectively as the patterns produced by historical mixed-severity fire regimes. 

Two broad factors contributing to reductions in wildlife population viability 

were highlighted in these assessments: (1) changes in amount and distribution of old 

forest, deciduous, early-seral, shrub-steppe, and postfire habitats, and (2) impacts 

of human activities associated with grazing, roads, and recreation. These habitat 

trends give a general sense of the regional and provincial status of those habitats, but 

there is much variability in the trends among subwatersheds within provinces. As 

with stand and landscape management, the variability in conditions is perhaps more 

important to understand and manage for than the average. Hence, managers need to 

assess the trends in their local subwatersheds for an accurate assessment of habitat 

trends and management needs. For example, the trend in broad-elevation old forest 

habitat was neutral in two of the four provinces; but within those neutral provinces 

old forest habitat decreased in 47 percent of the subwatersheds in the Blue Mountains and 37 percent of the subwatersheds in the southeastern Cascades (Wisdom 

et al. 2000). 

Human land uses have important effects on animal populations at several 

scales. At the broadest regional scale, residential, agricultural, and transportation 

network development has resulted in habitat loss and fragmentation throughout 

western North America (Theobald et al. 2011). In eastern Oregon and Washington, 

broad-scale habitat connectivity patterns for species associated with MMC forests 

are determined by major landform features and associated ecotonal boundaries, in 

combination with human development patterns (Singleton et al. 2002, WHCWG 

2010). Major natural barriers for species associated with MMC forest habitats in 

the Pacific Northwest include the shrub-steppe landscapes of central Washington 

and Oregon, and dramatic landforms like the Columbia Gorge, Lake Chelan, the 

Okanogan Valley (U.S.), and Hells Canyon (Singleton et al. 2002, WHCWG 2010). 

Major anthropogenic barriers include high-volume highways (e.g., Interstate 90, 

Interstate 84, portions of U.S. Highway 97, and Canada Highway 3), as well as areas 

of agricultural, residential, and industrial development. One area of dramatic recent 

rapid development has been in southern British Columbia, through the Okanogan 
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Valley and portions of the Highway 3 corridor between Osoyoos and Castelgar 

(Singleton et al. 2002, WHCWG 2010). These linkage patterns are particularly 

important for species associated with MMC forests in Washington because populations in Washington are often southern extensions of populations centered in 

Canada (Singleton et al. 2002, WHCWG 2010). 

At a finer scale, forest roads and trails and associated recreational activities can 

have substantial impacts on wildlife populations associated with MMC habitats 

(reviewed by Gaines et al. 2003). Common responses of animals to roads and trails 

include displacement and avoidance, which can contribute to disruption of nesting, 

breeding, or wintering areas and reduced population density (Benitez-Lopez et al. 

2010, Gaines et al. 2003). For example, Naylor et al. (2009) quantified elk behavioral 

responses to off-road recreational activities including ATVs, mountain biking, 

hiking, and horseback riding in the Blue Mountains. They found that feeding time 

decreased and travel time increased in response to these activities. Road access 

for firewood gatherers can also contribute to loss of large snags and logs in many 

areas (Hollenbeck et al. 2013). Ecological effects of domestic livestock grazing are 

reviewed in “Grazing” on page 99.

Altered disturbance regimes and historical land management practices have 

contributed to substantial changes in the amount and distribution of forest habitats 

relative to historical conditions, but management activities focused on restoration of 

historical habitat patterns and stand structure conditions can also have a variety of 

effects on wildlife populations. These effects can differ substantially across species (reviewed by Kennedy and Fontaine 2009, and Pilliod et al. 2006). At a stand 

scale, restoration treatments tend to favor those species associated with more open 

conditions and increased understory vegetation diversity, and have the potential to 

reduce abundance of species associated with closed canopy, old forest conditions 

(e.g., Converse et al. 2006, Gaines et al. 2010). However, responses can be quite 

variable depending on the intensity of the treatment, and although the abundance 

of individual species can change, restoration treatments generally do not cause 

substantial changes in species diversity (e.g., Gaines et al. 2010, Lyons et al. 2008, 

Russell et al. 2009).

Retention of large, old trees, snags, and logs can help maintain the old forest 

functions of many stands when smaller trees are removed for fuel reduction or forest restoration objectives. For example, Bull et al. (1995) found that a MMC stand 

in the Blue Mountains continued to function as old growth for pileated woodpecker 

and Vaux’s swift (Chaetura vauxi) when large trees and logs were retained after 

treatment to remove small trees killed by western spruce budworm. Most research 

Retention of large, old 

trees, snags, and logs 

can help maintain the 

old forest functions 

of many stands 

when smaller trees 

are removed for fuel 

reduction or forest 

restoration objectives.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

on the effects of forest restoration or fuel reduction treatments on wildlife have 

focused on responses soon after treatment (<5 years post-treatment; Kennedy and 

Fontaine 2009). Longer-term (>10 year post-treatment) effects of forest restoration 

treatments on animal populations have yet to be well documented. This will be a 

fertile area for future research as recently treated areas mature and provide opportunities for monitoring the effects of those restoration-oriented treatments.

Old forest habitats are of particular conservation concern because they provide 

a variety of ecological and social values (reviewed in Spies and Duncan 2009), and 

old forest characteristics take a long time to regenerate when they are lost as a consequence of high-intensity disturbance or intensive management. In the following 

section we present information on habitat dynamics and conservation of the NSO. 

We recognize that much of the area being addressed by this document is outside of 

the range of the NSO, but we present this information to highlight the lessons from 

spotted owl conservation that are also important for conservation of other old forest 

species associated with MMC forests across eastern Washington and Oregon.

The old growth forests of the east Cascades are diverse, dynamic, and shaped 

by the complex behavior of multiple disturbance factors including fire. The historical structure and function of these forests have been extensively altered by fire 

exclusion, logging, and other activities (Buchanan et al. 1995, Spies et al. 2006, 

USFWS 2011). The implications of these changes and the current and future conditions of east Cascades forests for NSO recovery are complex. Habitat conditions 

for spotted owls in this region are significantly different today than 150 years ago. 

Although much habitat has been degraded, particularly with the chronic loss of suitable structures for nesting and roosting sites (i.e., selective removal of large trees, 

removal of snags and damaged live trees) there has also been an increase in dense 

forest across portions of the landscape (Everett et al. 1997, Hessburg et al. 2005). 

These changes present multiple challenges for land managers. Where and how 

much of these dense stands should managers strive to retain? How is retention of 

dense forest reconciled with meeting restoration goals that necessarily consider the 

resiliency of a forest in light of impending disturbance factors and climate change?

The recent recovery plan for the NSO (USFWS 2011) stated that the recovery 

strategy requires action in the face of uncertainty. The plan cites Carey (2007) in 

advocating “active management for ecological values that will trade short-term 

negative effects for long-term gains. Collaborative management must be willing to 

accept short-term impacts and short-term risks to achieve long-term benefits and 

long-term risk reduction.” The recovery plan described the difficulties in defining 

conservation objectives for habitat of NSO in these drier forests of the east side:
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GENERAL TECHNICAL REPORT PNW-GTR-897

Changing climate conditions, dynamic ecological processes, and a variety 

of past and current management practices render broad management 

generalizations impractical. Recommendations for spotted owl recovery 

in this area also need to be considered alongside other land management 

goals—sometimes competing, sometimes complementary—such as fuels 

management and invasive species control. In some cases, failure to intervene 

or restore forest conditions may lead to dense stands heavy with fuels and 

in danger of stand-replacing fires and insect and disease outbreaks (USFWS 

2011: III-20).

In general, dynamic, disturbance-prone forests of the eastern Cascades, California Cascades, and Klamath Provinces could be actively managed in a way that 

reconciles the overlapping goals of spotted owl conservation, responding to climate 

change, and restoring dry forest ecological structure, composition and processes, 

including wildfire and other disturbances

As stewards of NSO habitat, land managers are endeavoring to provide the full 

complement of habitat requirements. Strong evidence exists suggesting that nesting 

and roosting habitat, the array of structures in trees that provide a platform, cover, 

or both, have been largely removed from many areas through decades of selective 

cutting and sanitation treatments (USFWS 2011). Managers are advised to pay 

special attention to this habitat management issue when assessing and planning 

projects, and to make special efforts to retain and restore these habitat elements to 

the landscape. However, less certainty exists regarding the relationship between 

owls and habitat used for foraging across the broader landscape. Evidence suggests 

that owls tend to forage in the moderate- to higher canopy-closure forests and by 

the same token tend to avoid open stands (reviewed by Courtney et al. 2004).

Northern spotted owl numbers may continue to decline as a consequence of 

competition with barred owls, but retention and recruitment of habitat continues to 

be important because reductions in habitat availability are likely to increase competition between the species and will limit opportunities for spotted owls to adapt 

to the presence of barred owls (Dugger et al. 2011, Forsman et al. 2011, Singleton 

2013). Risk and uncertainty are inescapable with management of these forests. 

Employing a landscape view of assessment and management can help us understand 

these risks and uncertainties more clearly. 

Spotted owls are different from other old forest species associated with MMC 

forest. For example, northern goshawks and pileated woodpeckers have a broader 

distribution throughout the Interior West and are associated with a broader range of 

forest conditions including drier, more open mixed-conifer stands than those used 

by NSOs, but there are some lessons from spotted owl management that are worth 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

considering for conservation of these other old forest species. In particular, loss of 

old forest structures to large-scale, high-intensity wildfire is a concern for all old 

forest species. Landscape conditions that provide for mixed-severity fire patterns 

and that are resilient to intermittent disturbances will be most likely to provide a 

shifting mosaic of old forest habitat conditions for all old forest species over time. 

Managing for patterns that continually bring stands into old forest conditions is also 

important because we cannot rely on existing old forest stands to remain in that 

condition over long time periods. This approach of maintaining a shifting mosaic of 

old forest conditions is likely to be an increasingly important concept for old forest 

wildlife conservation under future disturbance regimes that are anticipated under 

many climate change scenarios.

Conservation of unique forest structures (particularly big old trees) is important, but it will be most effective if it is done in the context of sustainable landscape 

patterns. Big old trees, both vertical and horizontal, living and dead, are important 

across all stages of stand development (Bull et al. 1997). Where big old trees are 

absent from a landscape, retaining the largest trees, even of undesirable species, 

may be appropriate for retaining and developing stand structure. Retaining legacy 

structures can also provide conditions that facilitate more rapid development of 

multistory canopy conditions in younger forests.

Another fundamental challenge is that overly aggressive stand sanitization can 

contribute to a loss of structural diversity. This is a key issue in balancing silvicultural and wildlife habitat objectives at the stand scale. For example, past forest 

management practices often focused on reducing pathogens like mistletoe and rootrot to enhance fiber production through vigorous tree growth. At moderate levels, 

these pathogens can enhance spatial and structural complexity within forest stands. 

Mistletoe can contribute to tree mortality, but it also provides important structures 

for forest wildlife, particularly in harvested or young stands devoid of snags where 

mistletoe can create large clumps that function much like cavities to provide nesting 

and roosting opportunities for a variety of bird and mammal species, including 

spotted owls and their prey (Parks et al. 1999, Sovern et al. 2011, Watson 2001) 

(fig. 43). Endemic levels of insects and disease can contribute to stand and spatial 

heterogeneity important to wildlife, but epidemic levels can be detrimental. We 

acknowledge that retention of these endemic insect and disease processes involves 

a delicate balance between tree growth and wildlife habitat objectives, and it entails 

a certain degree of risk.

Climate change has the potential to strongly influence wildlife populations and 

habitats (Dalton et al. 2013, Hixon et al. 2013). At the broadest level, changes in 

the area and location of major habitat types influence wildlife. The habitat types 
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GENERAL TECHNICAL REPORT PNW-GTR-897

that are projected to change in the near future may be of highest concern. Within 

Oregon and Washington, Rocky Mountain and Cascade subalpine systems are forecast to decline most rapidly (Rehfeldt et al. 2012). Several Forest Service-designated 

sensitive species are associated with subalpine habitats including wolverine, grizzly 

bear (Ursus arctos), lynx (Lynx canadensis), and American marten (Gaines et al. 

2000). The wolverine, for example, is thought to be restricted to places with late 

spring snow pack (Aubry et al. 2010). McKelvey et al. (2011) modeled change in 

the distribution of such areas in the Western United States under projected future 

climates. Based on a downscaled ensemble model, they projected that 67 percent of 

Figure 43—Fine-scale structural diversity associated with dwarf mistletoe clumps and other tree 

defects provide important habitat components for many wildlife species. This Douglas-fir tree is 

severely infested with dwarf mistletoe.

Peter Singleton
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

predicted spring snow cover will persist within the study area through 2030–2059, 

and 37 percent through 2070–2099. Areas with spring snow are currently relatively 

limited in eastern Oregon and Washington. 

Nearly all of these areas except the Eagle Cap Wilderness are projected to 

entirely lose spring snow by mid-century, which will likely substantially reduce viability of the wolverine populations in those areas (McKelvey et al. 2011). Substantial 

reductions in the Rocky Mountain montane conifer habitats that cover much of the 

Okanogan Highland and Blue Mountains are of concern for lynx and the old-forest 

specialists mentioned above (Aubry et al. 2000). There are many other wildlife 

species that are likely to be affected by phenological changes resulting from climate 

change. We are already observing earlier onset of spring and longer, dry summer 

periods that will increase drought stress (Hixon et al. 2011). These changes will 

have significant ramifications for the entire biological community (Rosenzweig at 

al. 2008, Walther et al. 2002). 

Maintaining broad-scale landscape patterns that allow species to move 

in response to changes in climatic and habitat conditions may be particularly 

important for conservation of sensitive species (Heller and Zavaleta 2009, Nuñez 

et al. 2013). Climate change also has the potential to alter connectivity for some 

species. Initial studies have estimated reductions in habitat connectivity under 

future climate change for wolverine (McKelvey et al. 2011) and American marten 

(Wasserman et al. 2012). However, we are not aware of studies that have estimated 

the combined effects of climate and land use change on connectivity in the Northwestern United States.

The effects of climate change are also manifest within the landscape and stand 

scales most familiar to forest managers. Many wildlife species require access to two 

or more habitat types in close proximity, such as use of grasslands and forest by elk. 

Over the past century, ecotones between habitat types have shifted within landscapes owing to changes in climate, livestock grazing, and fire exclusion. In many 

portions of eastern Oregon and Washington, conifer forests have encroached into 

grasslands and shrublands (e.g., Hessburg and Agee 2003; Hessburg et al. 2000b, 

2005). In the last decade, the frequency of severe fire in the lower forest ecotone has 

increased (Perry et al. 2011), sometimes leading to a retraction of the forest ecotone. 

Under future climate and land use, habitat mosaics across landscapes are likely to 

be even more dynamic. Within forest stands, structural complexity also varies with 

climate, land use, and disturbance. Fire exclusion can lead to increased density of 

stems and higher canopy closure; insect outbreaks can result in losses of live large 

trees and major increases in snags and coarse woody debris. In sum, interactions 

among climate, land use, and disturbance are expected to bring wide swings in 
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GENERAL TECHNICAL REPORT PNW-GTR-897

Sensitive Species of Moist Mixed-Conifer Forests

A variety of terrestrial wildlife species is associated with the moist mixed-conifer (MMC) forests 

and surrounding landscapes in the Pacific Northwest, including one endangered species (gray wolf 

[Canis lupus], recently delisted in part of its range), three federally listed threatened species (NSO, 

grizzly bear, and lynx), and three federal candidate species (Oregon spotted frog [Rana pretiosa], 

fisher [Martes pennanti], and wolverine). In addition, several other wildlife species of concern 

recognized by state or federal agencies inhabit these forests (table 7). Many of the species that are 

at risk in the region are associated with particular stand structure conditions, vegetation community types, and landscape configurations. For example, NSOs are found in MMC forests on the east 

slope of the Cascades from the Canadian border into northern California (USFWS 2011). They are 

associated with structurally diverse, large tree, moderate- to closed-canopy conditions generally 

found in older forests that do not have a recent history of fire, much of which has been altered by 

both logging and more recently large fires in the last 50 to 100 years. A small population of grizzly 

bears inhabits MMC forest in the Pacific Northwest. Distribution of this population is limited to a 

few areas along the Canadian border in the North Cascades and Kettle Mountain/Wedge areas of 

northeast Washington (Gaines et al. 2010, USFWS 1997). Grizzly bear habitat associations in the 

Cascades and northeast Washington include moist forests, particularly areas of those forests that 

are interspersed with moist meadows or avalanche chutes where food plants are abundant (Gaines 

et al. 2000). Oregon spotted frogs were once found near moving water through much of the Cascades in Oregon and Washington (Cushman and Pearl 2007, McAllister and Leonard 1997). More 

recently, populations have been documented in Washington’s southeast Cascades (near Trout Lake 

and Conboy in Klickitat County) and in Oregon’s south-central Cascades. The historical range 

of fishers encompasses mesic interior forests in the Oregon and Washington Cascades, northeast 

Washington, and Blue Mountains (Lewis and Stinson 1998). Fishers were extirpated from most of 

that range as a result of fur trapping. A small population is present in Oregon’s southern Cascades 

but at present they are largely absent from interior forests in Oregon and Washington. 

habitat composition within landscape, developmental stage distribution, and withinstand structure. These conditions will challenge forest managers to maintain the 

stand, landscape, and regional habitat components required by many native species. 

Altered snowmelt run-off regimes in the mixed-conifer forests will affect 

downstream fish-bearing reaches. Discharge patterns affect water depth; thus, 

earlier low flows downstream may reduce habitat availability for fish dependent on 

deeper, slower flowing habitats (Luce et al. 2013, Tague and Grant 2009). Cutthroat 

trout and bull trout are the most sensitive species likely to be present in mixedconifer zones. Bull trout occupy the coldest freshwater habitats of all salmon and 

trout species and these habitats are predicted to be severely affected by climate 

change in coming decades (Isaak et al. 2010, Rieman et al. 2007, Wenger et al. 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 7—Sensitive wildlife species found in interior mesic forests, including species broadly associated with 

interior moist forest and ecotones; many of these species are associated with specific forest structure or 

seral stages found within the interior mesic forest zone

Common name Scientific name Class Statusa Comments

Western toad Anaxyrus boreas Amphibian FCo

Rocky Mountain tailed frog Ascaphus montanus Amphibian FCo

Oregon slender salamander Batrachoseps wrighti Amphibian FCo Eastern Oregon 

Cascade Range

Larch mountain salamander Plethodon larselli Amphibian FCo Southeast Washington 

Cascade Range

Columbia spotted frog Rana luteiventris Amphibian SC

Northern leopard frog Rana pipiens Amphibian FCo

Oregon spotted frog Rana pretiosa Amphibian FC

Northern goshawk Accipiter gentilis Bird FCo

Upland sandpiper Bartramia longicauda Bird SE

Vaux’s swift Chaetura vauxi Bird SC

Olive-sided flycatcher Contopus cooperi Bird FCo

Black swift Cypseloides niger Bird FCo Associated with waterfalls

and wet cliffs

Pileated woodpecker Dryocopus pileatus Bird SC

Peregrine falcon Falco peregrinus Bird FCo

Harlequin duck Histrionicus histrionicus Bird FCo

Lewis’ woodpecker Melanerpes lewis Bird SC

Flammulated owl Otus flammeolus Bird SC Associated more with 

dry forest 

White-headed woodpecker Picoides albolarvatus Bird FCo Associated more with 

dry forest

Black-backed woodpecker Picoides arcticus Bird SC

Northern spotted owl Strix occidentalis Bird FT

Silver-bordered fritillary Boloria selene atrocostalis Insect SC

Manns mollusk-eating ground beetle Scaphinotus mannii Insect SC

Gray wolf Canis lupus Mammal FEb

Townsend’s big-eared bat Corynorhinus townsendii Mammal FCo

Spotted bat Euderma maculatum Mammal FCo

Wolverine Gulo gulo Mammal FC

Silver-haired bat Lasionycteris noctivagans Mammal FCo

Lynx Lynx canadensis Mammal FT

Fisher Martes pennanti Mammal FC Northeast Washington, 

east of Okanogan River

Long-eared myotis bat Myotis evotis Mammal FCo

Long-legged myotis bat Myotis volans Mammal FCo

Woodland caribou Rangifer tarandus caribou Mammal FE Selkirk Mountain population

in northeast Washington

Preble’s shrew Sorex preblei Mammal FCo

Grizzly bear Ursus arctos Mammal FT

Poplar Oregonian Cryptomastix populi Mollusk SC

Dalle’s sideband Monadenia fidelis minor Mollusk SC

Western pond turtle Actinemys marmorata Reptile SC

Sharptail snake Contia tenuis Reptile FCo Local in eastern slope 

of the Cascade Range

a

 Status codes are FE = federal endangered, FT = federal threatened, FC = federal candidate, FCo = federal species of concern, 

SE = state endangered, SC = state species of concern.

b Recently delisted east of U.S. Highway 97.

Data sources: Oregon or Washington federal status from http://www.fws.gov/oregonfwo/species/Lists/Documents/

OregonStateSpeciesList.pdf and http://www.fws.gov/wafwo/pdf/specieslist120613.pdf. Washington state status from 

http://wdfw.wa.gov/conservation/endangered/All/. Oregon state status from http://www.dfw.state.or.us/wildlife/diversity/

species/sensitive_species.asp.
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GENERAL TECHNICAL REPORT PNW-GTR-897

2011). Changing precipitation and fire regimes are expected to compound the 

effects of warming trends by shifting hydrologic patterns and those of sediment 

transport and solar radiation (Dunham et al. 2007, Isaak et al. 2010).

Bull trout life histories include migratory forms that spawn and rear in cold 

streams close to headwaters, then migrate downstream to larger rivers where they 

live as adults prior to spawning (“migratory”) or migrate to lakes following rearing 

(“adfluvial”). Fragmentation of cold water habitats by stream warming can increase 

physiological stress to bull trout and decrease interconnectivity of adequate spawning and rearing aggregations. In the “resident” life history form, bull trout remain 

in cold headwater streams for spawning, rearing, and as adults. Thus, they are 

subject to these physiological stressors at all life stages.

Cutthroat trout are also common to upland streams in mixed-conifer forests 

of the eastern Cascades. In small streams within mixed-conifer watersheds of the 

Wenatchee River sub-basin, cutthroat trout density and total biomass are limited 

by higher flows (fig. 36) (see footnote 1). Thus, changing flow regimes as a result of 

precipitation and snowmelt-timing shifts can potentially have consequences for the 

persistence of populations of this species.

Current Socioeconomic Context

When this science synthesis was initiated, the decision was made to focus on the 

biophysical science associated with managing MMC forests. However, management 

of these forests takes place within the broader socioeconomic context of eastern 

Oregon and Washington, which both influences and is influenced by forest management.4

 In addition, some concepts of resilience include interactions between 

social and ecological subsystems (see “The Concept of Resilience” on page 18). 

Thus, some important socioeconomic issues relevant to forest management in 

the region are briefly reviewed here, recognizing that the topics covered are not 

all-inclusive. We focus on issues most relevant to accomplishing forest restoration 

on eastside forests by creating a more enabling social and economic environment. 

Two such topics—collaboration and the social acceptability of forest restoration 

treatments—are addressed in chapter 6. The key issues of focus in this section are 

wood products infrastructure and business capacity to support forest restoration, 

opportunities for biomass utilization, and some of the tribal concerns associated 

with forest restoration in the region. Also highlighted are the potential impacts 

of restoration treatments on recreation. Germane management implications are 

included in each sub-section. It is important to note that the literature addressing 

4

 For purposes of this section, eastern Oregon and Washington refer to all of the counties 

that lie east of the Cascade crest in Oregon and Washington. 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

the socioeconomic context of forest management in eastern Oregon and Washington 

is rarely specific to the MMC forest type; is more extensive for eastern Oregon 

than for eastern Washington; is largely gray literature (as opposed to peer-reviewed 

literature); and consists mainly of assessment work rather than scholarly research.

The region is dominated by rural counties where natural resources have 

historically played an important role in contributing to local economies through 

agriculture, ranching, forestry, and more recently, recreation. Many of eastern 

Oregon’s counties exhibit high levels of poverty and unemployment however (Davis 

et al. 2010), and many eastern Washington counties have been characterized as 

having relatively low socioeconomic resilience (Daniels 2004). Social and economic 

assessments of interior Columbia River basin communities carried out as part of the 

Interior Columbia Basin Ecosystem Management Project (Harris et al. 2000, Reyna 

1998) found that small population size, geographic isolation, low economic diversity, heavy dependence on one or a few employment sectors, low level of money 

coming in from the outside, poorly developed infrastructure, and less active leadership all contribute to low community resilience in the region.5

 Conducting forest 

restoration can potentially increase community resilience by sustaining existing 

and creating new and future job opportunities, diversifying the local employment 

base, retaining existing jobs and stimulating new infrastructure development, and 

spurring innovations and investments to create new business and employment 

opportunities—all of which contribute to community resilience (Berkes and Ross 

2013, Davidson 2010, Magis 2010, Walker and Salt 2006).

The Forest Service 2012 Planning Rule provides direction to contribute to 

social and economic sustainability through forest management to help support 

vibrant communities and rural job opportunities. In addition to employment, other 

economic benefits resulting from fire hazard reduction through forest restoration 

may include reduced fire suppression costs over the longer term, increased 

production of wood products, higher state tax revenues, reduced unemployment 

payments, and lower expenditures on social services (State of Oregon 2012). Forest 

restoration to improve forest health can also benefit other ecosystem services 

associated with national forest lands, including clean water, fish and wildlife 

habitat, and recreation activities (State of Oregon 2012). Frameworks for identifying 

the ecosystem services from national forests that are important to stakeholders, 

and for evaluating the social and ecological tradeoffs between services that are 

associated with different forest management actions, have been developed by 

Asah et al. (2012), Kline (2004), Kline and Mazotta (2012), and Smith et al. (2011). 

5

 Community resilience is defined here as the ability of a community to successfully cope 

with, adapt to, and shape change and still retain its basic function and structure. 

The region is 

dominated by rural 

counties where natural 

resources have 

historically played 

an important role in 

contributing to local 

economies through 

agriculture, ranching, 

forestry, and more 

recently, recreation. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

Forest restoration to reduce hazardous fuels also reduces the risk of wildland fire 

to communities located in the wildland-urban interface.

Wood Processing Infrastructure and Business 

Capacity for Forest Restoration

Decreased timber harvesting on federal lands in Oregon and Washington (and 

elsewhere in the West) since the late 1980s, together with changing technology 

and markets, industry restructuring, and the recession of 2007–2009 have led 

to dramatic declines in the production of wood products and mill infrastructure 

throughout these states (Charnley et al. 2008, Keegan et al. 2006, OFRI 2012). In 

Oregon and Washington, most of the remaining mills are on the west side of the 

Cascades (Keegan et al. 2006, Nielsen-Pincus et al. 2012). The increase in severe, 

large-scale fires that has occurred during the 2000s points to the need for hazardous fuels reduction, in which treatments to remove trees of different sizes play an 

important role (Keegan et al. 2006). Such removals may include trees having commercial value, as well as trees with smaller diameters than what have traditionally 

been considered merchantable. Important questions are how to retain what remains 

of the wood processing infrastructure, whether existing mills can process trees 

of different size classes (Keegan et al. 2006), and how to develop a new and more 

diversified infrastructure. 

In eastern Oregon, the primary wood processing infrastructure that exists today 

represents about 20 percent of what it was in the 1980s (Swan et al. 2012). Associated milling capacity has also declined (OFRI 2012). In 2012, there were 45 major 

primary wood processing facilities and operations in eastern Oregon, including 11 

open and three closed sawmills, two open plywood plants, and a number of chipping facilities and operations, post and pole mills, species-specific specialty mills, 

firewood processors, and whole log shaving operations (Swan et al. 2012). Together, 

these wood processing facilities employed an estimated 1,730 people (at minimum). 

Although this diversified mill infrastructure provides opportunities for producing 

a range of products from logs of different sizes and types, existing mills are not 

operating at full capacity. Sawmills and chip mills currently operate at about 50 

percent of capacity, and whole log mills at 40 percent. Increasing the capacity of 

their operations could potentially increase employment at eastern Oregon’s wood 

processing facilities by 35 percent (Swan et al. 2012). Doing so would require an 

increased and sustained supply of logs and fiber of the appropriate sizes and species, favorable market conditions, adequate financing, and a reliable, experienced 

workforce (OFRI 2012, Swan et al. 2012). 

With regard to production from MMC forests to help meet supply needs, eastern Oregon mills that produce lumber graded for strength prefer interior Douglas-fir 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

and white fir, but also use Engelmann spruce, lodgepole pine, and subalpine fir (Swan 

et al. 2012). Mills that produce lumber graded for appearance prefer ponderosa pine 

but also use high-quality white fir. Pulp and paper mills that consume wood products 

from eastern Oregon, located mainly along the Columbia and Snake Rivers, prefer 

lodgepole pine and white fir, but accept other tree species. Size preferences typically 

range from 31 to 41 cm (12 to 16 in) diameter for large logs (though some mills take 

up to 56 cm [22 in] logs), and 10 to 15 cm (4 to 6 in) to 25 to 30 cm (10 to 12 in) for 

small logs (Swan et al. 2012). 

Ownership of eastern Oregon’s timberlands is 67 percent Forest Service and 

29.2 percent private (OFRI 2012). However, 75 percent of the current supply of wood 

products for industry in eastern Oregon comes from nonfederal lands, and 25 percent 

from federal lands (nearly all Forest Service) (Swan et al. 2012). Eastern Oregon 

sawmills obtain an average of 63 percent of their supply from nonfederal (almost 

all private) lands (Swan et al. 2012). 

Assessments have found that in eastern Oregon, private lands will not be able to 

support pre-economic recession (2007) harvest levels in a sustainable way, implying 

that increased wood supplies will need to come largely from federal lands (OFRI 

2012). Harvests from federal lands in eastern Oregon are currently estimated at 

7 percent of annual growth (OFRI 2012). 

The nature of the supply from Forest Service lands has also shifted significantly 

since the 1980s from predominantly sawlogs greater than 31 cm (12 in) in diameter, to 

mostly non-saw logs (biomass). Thus, to significantly increase forest restoration treatments in eastside forests, new investment in mill facilities designed to process smallerdiameter material will likely be needed, which in turn will hinge on public support 

and a reliable supply of raw material over a 10-year time horizon at a minimum (OFRI 

2012). The State of Oregon (2012) provided a number of recommendations for how to 

increase the scale of restoration on Forest Service lands in eastern Oregon.

There is also a need in eastern Oregon to recruit more people into the logging 

workforce and to increase access to capital to support investments in new equipment 

(OFRI 2012). One consequence of the loss of forest products industry infrastructure 

has been a loss of people having the skills and knowledge to work in eastern Oregon’s 

forestry sector (OFRI 2012). The business capacity to engage in forestry support work 

(e.g., activities in support of timber production, firefighting, and reforestation) has 

been growing in eastern Oregon over the past decade (Davis et al. 2010). Retaining 

and increasing the local infrastructure, workforce, equipment, and businesses needed 

to engage in forest management is critical for carrying out landscape-scale forest restoration to improve the ecological integrity and resilience of forest ecosystems (Kelly 

and Bliss 2009, State of Oregon 2012). 
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GENERAL TECHNICAL REPORT PNW-GTR-897

Another consequence of reduced forestry infrastructure has been that the average distance between mills is often greater than 161 km (100 mi) in eastern Oregon, 

increasing log haul distances and associated transportation costs (Swan et al. 2012). 

This leads to reduced competition for logs—driving down stumpage prices—and 

higher transportation costs to get logs to more distant mills, which together can 

result in uneconomical timber sales, making it more difficult and costly to engage in 

forest restoration and hazardous fuels reduction. Nielsen-Pincus et al. (2012) found 

that national forest ranger districts that are close to sawmills and biomass facilities 

treated more overall hectares for hazardous fuels reduction, and more hectares in 

the WUI, than those farther away, and that there was a threshold distance (hauling 

time) for this effect in Oregon and Washington of 40 minutes. A lack of local wood 

processing infrastructure constrains the management options available to forest 

managers and, in turn, affects managers’ capacity to address declining forest health 

and increasing fire risk (Eastin et al. 2009).

In Washington state, there was a steady decline in the number of wood processing facilities between 1991 and the 2000s, with several mills closing along the east 

side of the Cascades, and the remaining industry shifting from rural to urban areas 

to be nearer to major transportation corridors (WA DNR 2007). In 2010, there were 

14 mills in central and eastern Washington, half of them sawmills (Smith 2012). 

Three pulp mills, one veneer and plywood mill, and three roundwood chipping 

mills comprise the remainder of the infrastructure. Few new mills have replaced the 

mills that closed, though the remaining mills tend to be larger and more efficient 

(Smith 2012). The distance between mills is greater than 322 km (200 mi) in some 

parts of eastern Washington however, meaning high transportation costs for what 

are often low-value, small-diameter logs, and less competitive prices (WA DNR 

2007). 

The dominant log species consumed by eastern Washington mills in 2010 were 

Douglas-fir (38 percent), ponderosa pine (25 percent), true firs (18 percent), and 

lodgepole pine (9 percent) (Smith 2012). Of these logs, 48 percent came from private lands, 21 percent from tribal lands, 17 percent from state lands, and 11 percent 

from national forest lands. The dominant size classes harvested were 13 to 25 cm (5 

to 10 in) (40 percent) and 25 to 51 cm (10 to 20 in) (36 percent) (Smith 2012).

Studies have found that in order to achieve forest restoration goals in eastern 

Washington, new investments in wood processing infrastructure will be needed 

(WA DNR 2007). Again, having a stable and adequate supply of wood is critical 

for stimulating such investments. Increasing harvests from state and private lands 

to meet supply needs is unlikely to be sustainable however, implying an important 

role for federal land harvests. Other factors that would help would be government 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

incentives for investing in wood processing facilities, diversification of processing 

infrastructure (as has occurred in eastern Oregon), establishing markets for carbon 

and biodiversity, and reducing local regulatory constraints to mill construction and 

forest products manufacturing (WA DNR 2007). 

Ensuring a reliable supply of wood of all size classes from federal lands in 

eastern Oregon and Washington is critical for maintaining existing and establishing 

new wood processing infrastructure (Keegan et al. 2006). To stay in business, mills 

also need to remain competitive by investing in improvements such as increasing the efficiency of log conversion, producing higher value products and a more 

diverse product mix, or constructing drying kilns on site (Dramm 1999). Stewardship contracting, where appropriate, is one tool that can help in this regard because 

it allows the Forest Service to enter into contracts of up to 10 years in duration 

and to provide a reliable supply of wood. The Collaborative Forest Landscape 

Restoration Program is another mechanism that should encourage a more reliable 

supply of small-diameter wood to support industry investments in infrastructure 

in participating landscapes (which currently include four areas of eastern Oregon 

and Washington, plus one affiliate in Washington). This program aims not only to 

encourage national forests to commit to carrying out restoration projects by providing a source of funding for up to 10 years, but to incentivize restoration treatments 

on other ownerships within the same landscapes by leveraging funding from other 

sources (Schultz et al. 2012). Doing so may help increase the supply from other 

ownerships. The program also requires projects to make use of existing or proposed 

processing infrastructure to support jobs and local economies (Schultz et al. 2012).

Developing biomass utilization opportunities is also important for retaining and 

increasing the number of sawmills. Sawmills produce a large volume of residual 

material associated with log processing that can be used for many biomass utilization applications, as well as for producing pulp and paper and other wood products 

(Davis et al. 2010). Unless they can market these residuals, sawmills may not be 

able to operate economically (Swan et al. 2012). The next section addresses this 

topic.

Biomass Utilization

The development of woody biomass utilization opportunities has received much 

attention over the past decade because (1) biomass is a domestic source of renewable energy; (2) biomass utilization can help to partially offset the cost of needed 

hazardous fuels reduction treatments on public lands and contribute to economic 

development opportunities in forest communities (Aguilar and Garrett 2009, Morgan et al. 2011, Nechodom et al. 2008); and (3) biomass utilization reduces the need 

for onsite burning of piled material produced by fuels treatments, and associated 

Ensuring a reliable 

supply of wood of 

all size classes from 

federal lands in 

eastern Oregon and 

Washington is critical 

for maintaining existing 

and establishing new 

wood processing 

infrastructure.
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GENERAL TECHNICAL REPORT PNW-GTR-897

environmental effects (Daugherty and Fried 2007, Springsteen et al. 2011). To date, 

biomass utilization infrastructure remains underdeveloped in eastern Oregon and 

Washington. As of 2012, there was only one stand-alone biomass energy cogeneration plant in eastern Oregon, which was temporarily closed because it could not 

obtain a favorable power sales agreement (Swan et al. 2012). When market conditions are good, biomass from eastern Oregon may be transported to western Oregon 

or to mills along the Columbia and Snake Rivers for use, but markets are highly 

variable. There were no stand-alone biomass energy facilities in eastern Washington in 2010 (Smith 2012), posing a challenge for forest restoration there (WA 

DNR 2007). Davis et al. (2010) provide an overview of status and trends in woody 

biomass utilization, including challenges and opportunities, across many eastern 

Oregon counties.

A number of economic issues constrain the development of viable biomass 

utilization facilities. To attract investors, there must be an adequate and predictable 

supply of biomass, a concern in places where federal land is the main potential 

source of supply (Becker et al. 2011, Hjerpe et al. 2009). The supply problem could 

be addressed by diversifying sources of raw material, through the use of stewardship contracts, or by addressing internal institutional barriers to biomass utilization 

within the Forest Service (Becker et al. 2011, Hjerpe et al. 2009, Morgan et al. 

2011). Supporting remaining wood products industry infrastructure to prevent its 

further loss can also help provide opportunities for biomass removal and utilization. 

For a number of reasons, the presence of wood products industry infrastructure has 

been found to enhance the development or expansion of biomass utilization, which 

is difficult to develop as a stand-alone enterprise (Becker et al. 2011). 

The cost of harvesting and transporting biomass is another key constraint 

(Aguilar and Garrett 2009, Becker et al. 2009, Pan et al. 2008). Becker et al. (2009) 

found that the cost of transporting biomass from the harvest site to the market outlet 

is the single greatest cost associated with biomass utilization, and that decreasing 

the travel distance between markets and harvest sites is the only strategy that offsets this cost in a meaningful way. Strategies for addressing the cost issue include 

establishing a network of decentralized processing facilities of an appropriate size 

and type closer to the source where biomass is removed (Aguilar and Garrett 2009, 

Nielsen-Pincus et al. 2012); developing utilization options that focus on higher value 

products; bundling biomass removal with the removal of larger trees that produce 

higher value products (e.g., lumber) (Barbour et al. 2008); developing transportation subsidies, which Oregon has done (though these can be problematic) (Becker 

et al. 2011, Nicholls et al. 2008); and implementing financial incentives such as cost 

sharing and grant programs for facility development and equipment purchases, and 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

tax incentives for facility development and harvesting and transporting biomass 

(Sundstrom et al. 2012).

Because biomass produced as a byproduct of forest restoration tends to be of 

low value, strategies associated with national forest management are likely to focus 

on establishing smaller processing facilities closer to public lands (Becker et al. 

2011). Small and mid-sized facilities that focus on electricity generation, firewood, 

animal bedding, commercial heating, or combined heat and power systems are 

likely to be more feasible than large processing facilities because they tend to be 

less controversial and require a smaller supply of biomass to operate (making it 

easier to obtain in a reliable manner) (Becker et al. 2011).

Markets are another major constraint on increasing biomass utilization. Key to 

increasing biomass utilization east of the Cascades is stimulating market demand 

and opportunities. The abundance of hydropower in the Pacific Northwest limits 

market opportunities for biomass electricity (Stidham and Simon-Brown 2011). 

Although low natural gas prices may also threaten the viability of biomass energy 

projects (OFRI 2012), eastern Oregon has large areas that lack access to natural 

gas, and woody biomass is more economical for heating than propane or heating oil 

(Swan et al. 2012). 

The main constraints on developing stand-alone, industrial-scale biomass 

energy plants in eastern Oregon currently are low prices for electricity under power 

purchase agreements, and uncertain pricing in the California market, making 

construction of such plants unlikely in the near future (Swan et al. 2012). 

Although the supply of biomass for manufacturing value-added products is 

greater than market demand (Stidham and Simon-Brown 2011), promising opportunities for biomass utilization lie in developing a broader range of products and 

applications such as pellets, bricks, small-scale institutional thermal applications 

(such as space and water heating), onsite electricity generation, transportation fuels, 

and bio-char (Davis et al. 2010, OFRI 2012, Swan et al. 2012). More diversified and 

integrated biomass utilization projects have been developing in eastern Oregon in 

recent years (Davis et al. 2010), signaling progress that may enhance forest restoration efforts there. 

Tribal Concerns

Tribal concerns associated with the management of MMC forests on federal lands 

in eastern Oregon and Washington include protecting tribal lands from fire, insects, 

and disease; creating job opportunities for tribe members in forest restoration; 

management to address the potential impacts of climate change on forest resources 

that are important to tribes; and incorporating tribe members and their traditional 

ecological knowledge into forest restoration decisionmaking and implementation. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

The 2004 Tribal Forest Protection Act (TFPA) was passed to protect tribal 

lands, resources, and rights from fire, insects, disease, and other threats (ITC 2013). 

The Act allows tribes to propose fire mitigation and environmental restoration 

activities on Forest Service and Bureau of Land Management lands adjacent to or 

bordering tribal trust lands and resources. The agencies may enter into contracts or 

agreements with tribes for this purpose. Despite the potential that TFPA authorities offer for fulfilling federal trust responsibilities, enhancing forest restoration 

activities, and creating job opportunities for tribe members in fuels reduction and 

postfire rehabilitation, only a handful of projects have been implemented. Reasons 

for this lack are described in ITC 2013. Ways that federal forest managers in eastern 

Oregon and Washington can take greater advantage of the opportunities provided 

by the Act include strengthening partnerships with tribes through formal agreements, promoting the use of the TPFA authorities internally, and conducting training and outreach to increase understanding and utilization of the TPFA (ITC 2013). 

Regarding job opportunities, a survey of 31 of the 42 federally recognized 

tribes in Oregon, Washington, and Idaho found that tribes had a strong interest 

in obtaining jobs in fire management, such as work on wildland fire suppression 

crews and hazardous fuels reduction work (Rasmussen et al. 2007). A number of 

strategies for promoting tribal economic development through fire management can 

be found in the Tribal Wildfire Resource Guide (Intertribal Timber Council and 

Resource Innovations 2006). Obstacles that limit the capacity of tribes to engage in 

this work include the seasonality of the work, the training required for employees 

and contractors, the cost of investing in equipment, a lack of financial capital with 

which to start businesses, and supportive tribal leadership to help form partnerships 

with public agencies (Rasmussen et al. 2007). Different communication and operating styles and Forest Service bureaucratic processes can also create barriers (Charnley et al. 2007). To the extent that the Forest Service can assist tribes in addressing 

some of these obstacles, it can help build the capacity of tribal communities to 

engage in fire management and forest restoration activities.

The environmental impacts of climate change are expected to be disproportionately felt by American Indian and Alaska Native tribes relative to nonnative 

communities because of their unique rights, economies, and cultures that are linked 

to the natural environment (Lynn et al. 2011). In eastern Oregon and Washington, 

climate change impacts on forests that may affect tribes include the potential for 

increased frequency and intensity of wildland fire; increases in invasive species, 

insects, and disease; and shifts in the quantity, quality, and distribution of culturally 

important forest resources (plants, animals, fungi, water, and minerals) (Voggesser 

et al. 2013). As a result, climate impacts on forests may threaten tribal subsistence, 

The environmental 

impacts of climate 

change are expected to 

be disproportionately 

felt by American 

Indian and Alaska 

Native tribes relative to 

nonnative communities 

because of their unique 

rights, economies, 

and cultures that are 

linked to the natural 

environment.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

culture, and economies. The traditional ecological knowledge held by tribe members can play an important role in helping federal forest managers identify species 

having social, cultural, and economic importance to tribes in the MMC zone, and in 

helping to inform management strategies for these species in the context of climate 

change. Strong federal-tribal relationships around forest management may also help 

to mitigate climate change impacts on species important to tribes, and assist tribes 

in developing adaptation strategies (Voggesser et al. 2013). Resources and research 

to support federal forest management in a manner that is responsive to the climate 

change-related concerns of tribes in the Pacific Northwest can be found at http://

tribalclimate.uoregon.edu/.

The relationship that exists between federally recognized tribes and the 

United States means that federal agencies are required to consult with tribes when 

they engage in policy making or undertake actions that affect tribal interests and 

resources. Consultation processes also promote collaboration between tribes and 

federal agencies in protecting and managing tribal resources on and off reservation 

lands (Whyte 2013). Working toward effective consultation processes will help 

ensure that restoration activities on national forests east of the Cascades address 

tribal concerns. Traditional ecological knowledge may also make an important contribution to forest restoration on national forest lands and can be fostered through 

federal-tribal consultation and partnerships and by directly engaging traditional 

knowledge holders in planning and implementing restoration activities (Vinyeta 

and Lynn 2013). A number of models for doing this are reviewed in Charnley et 

al. (2007), Donoghue et al. (2010), Vinyeta and Lynn (2013), and Voggesser et al. 

(2013).

Recreation

Moist mixed-conifer forests have high recreation value. The status of and trends 

in recreation activities on national forests in eastern Oregon and Washington can 

be found in the National Visitor Use Monitoring survey reports for these forests 

(http://www.fs.fed.us/recreation/programs/nvum/). Assessment information about 

recreation activities, trends, and issues in eastern Oregon and Washington can 

also be found in the Statewide Comprehensive Outdoor Recreation Plan (SCORP) 

reports for these states (http://www.oregon.gov/oprd/PLANS/pages/scrop08_12.

aspx; http://www.rco.wa.gov/documents/rec_trends/SCORP_2008.pdf), and in Hall 

et al. (2009). National forest recreation in MMC forests is likely to be affected by 

forest restoration treatments, which could be a source of contention. Exactly how 

recreation values may be affected by restoration treatments is difficult to predict, 

however, in the absence of site-specific research. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

A number of studies have been carried out in the Intermountain West to 

evaluate the effects of prescribed fire treatments and crown fires on recreation 

visitation and associated economic benefits. These studies have found that crown 

fires generally have a negative effect on recreation visitation and economic values 

over time, although there may be an initial, short-term positive response by some 

types of visitors (Englin et al. 2001; Hesseln et al. 2003, 2004; Loomis et al. 

2001). Hikers, for example, may be drawn to see wildfire effects and wildflower 

blooms following a crown fire (Englin et al. 2001, Loomis et al. 2001). Longer 

term declines in recreation visitation may result from the negative aesthetic effects 

of the fire, reduced access for certain activities, or damage to recreation facilities 

and infrastructure (Kline 2004). Areas that have substantially recovered from a 

crown fire may experience a rebound in visitation, however (Englin et al. 2001). In 

contrast, a study from Oregon’s Mount Jefferson Wilderness found that the B&B 

Fires of 2003 did not dramatically affect recreation in the first few years following 

the fire (Brown et al. 2008).

Prescribed fires have been found to have either no effect or a positive effect 

on recreation visitation and associated economic benefits over time in some places 

(Hesseln et al. 2004, Loomis et al. 2001). These effects can vary by recreation activity (e.g., hiking versus mountain biking) (Loomis et al. 2001). Elsewhere, prescribed 

fires have been found to have a negative effect on recreation visitation by hikers and 

mountain bikers and associated economic values, with visitation decreasing as the 

percent of a burn visible from the trail increased (Hesseln et al. 2003). 

These findings have a number of management implications. Because crown 

fires can be detrimental to recreation visitation and values, fuels reduction treatments may be one way of mitigating the negative social and economic impacts of 

crown fires on recreation (Hesseln et al. 2004). In some places, mechanical treatments may be more effective at mitigating these impacts than prescribed fire, and 

have fewer overall social and economic costs, because prescribed fire may also 

have a negative impact on recreation visitation and values (Hesseln et al. 2003). 

If prescribed fire is used, minimizing the area of the prescribed burn visible from 

popular recreation trails may reduce its negative effects. It is important to note, 

however, that some wildfires, such as fires that take place in areas dominated by 

shrubs, may have positive effects on recreation by creating more open forest conditions (Kline 2004). The ways in which wildfire and fuels treatments affect recreation vary by recreation activity, geographic location, type of wildfire and fuels 

treatment, forest characteristics, and over time (Kline 2004). Thus, the best way 

forward for identifying how different types of recreation activities may be affected 

by restoration treatments, and the most appropriate approach to forest restoration in 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

places where recreation values are high, is likely to be through place-based research 

and collaborative processes (Hesseln et al. 2003, Kline 2004). 

This brief overview of socioeconomic issues associated with forest restoration 

in eastern Oregon and Washington is not intended to be all-inclusive. Important 

issues not addressed include community wildfire protection, the effects of restoration treatments on other ecosystem services provided by national forests, the 

challenge of forest restoration at the landscape scale across ownership boundaries, 

and institutional barriers to forest restoration within federal agencies. This overview aims to touch on some of the key socioeconomic issues managers may face in 

trying to restore MMC forests, and provides some guidance about how to address 

these issues so that managers can evaluate both ecological and socioeconomic 

considerations when making decisions about forest restoration. Remaining research 

gaps with regard to the socioeconomic dimensions of managing MMC forests make 

it difficult to develop a robust framework for evaluating the social and economic 

tradeoffs entailed in management decisionmaking.

Summary of Key Scientific Findings and Concepts

The previous sections synthesize scientific findings most relevant to forest managers. We encourage the reader to investigate more thoroughly any of the topics 

discussed using the extensive reference section (about 400 citations) provided. 

Our key scientific findings and concepts are as follows:

Landscapes

• Broad-scale (top-down), meso-scale (within landscape), and fine-scale 

(bottom-up) spatial controls (aka, drivers or forcing factors) combine to 

control ecosystem behavior and ecological outcomes. Examples of topdown drivers are broad-scale patterns of the regional climate, geology, land 

surface forms, and broad patterns of biota—lifeforms and land cover types. 

Meso-scale or within landscape spatial controls are natural and human 

disturbances, topography, patterns of structure, composition, fuelbeds, and 

patch size distributions. Examples of fine-scale drivers are patterns of local 

topography, microsite, soils, plant communities and plant life history and life 

cycle differences, patterns of micro-climate, and the like. Some patterns at each 

of the three scales are not likely to be stationary in time or space, while others 

(geology, topography, geomorphic processes) are relatively more stationary. 

Any given landscape today is on a trajectory to a future condition that will be a 

result of these combined forces.
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GENERAL TECHNICAL REPORT PNW-GTR-897

• Regional landscapes can be viewed as a multi-level hierarchy of mosaics 

for landscape planning and management purposes; patches exist within local 

landscapes, which provide the patchiness and variability of the regional landscape. Patchiness also exists within patches (clumped tree distributions and 

gaps of various sizes) and this forms the variability of the local landscape. 

• Steep, topographically driven precipitation and temperature gradients 

have a significant influence on the vegetation east of the Cascade Range 

divide; the most significant effect is the rain shadow created by the high 

divide. 

• Forest productivity and disturbance regimes are highly influenced by 

these gradients. Position on the landscape combined with local weather conditions (precipitation and temperature), surface lithologies (parent materials 

and the soils that are derived from them), and land surface forms contribute 

to a complex mosaic of patches supporting a diverse array of vegetation. On 

any given landscape, dry, moist, and wet mixed-conifer forests occur 

within a large ecological gradient. As a consequence it is difficult to neatly 

disentangle these forest types for management purposes. 

• Landscapes exhibit varying degrees of inertia. The degree of change over 

the 20th century in forest structure, tree species composition, and disturbance 

regimes has given landscapes an inertia (which can be thought of also as 

ecological momentum or resistance to change) that will be difficult to alter 

through restoration-based management. For example, field observations suggest that after recent wildfires, instead of regenerating to ponderosa pine or 

western larch, some areas now quickly regenerate to Douglas-fir and white, 

grand, or subalpine fir, or lodgepole pine, despite intentional efforts (which 

often fail unless done well) to reestablish ponderosa pine or larch. The presence of abundant seed from shade-tolerant tree species (e.g., firs) provides 

this inertia. Likewise, high contagion of surface and canopy fuels creates 

large homogeneous patches that reinforce the occurrence of a higher than 

normal number of large and very large fires, and higher than normal 

fire severity. 

• The historical range of variability (HRV) that created pre-EuroAmerican forest landscapes has been changing and returning to it is 

no longer feasible or practical in some places. The pattern and processes 

of forest ecosystems in a landscape are functions of the range of variability 

in disturbances, climate, and species movements that has occurred over a 

long period of time. The range of variability in these processes in the future 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

will determine how the current patterns and processes of ecosystems and 

species will develop. Managers can influence the future range of variability 

to achieve desired future ecosystem conditions for a landscape. The HRV 

can serve as a guide but not a target. 

• Depending upon the biogeoclimatic setting and physiographic region, 

historical and future ranges of conditions may be either strongly or 

weakly overlapping. Future climate projections suggest that large differences between the past and the future tend to be associated with the extreme 

ends of ecological gradients, and ecotones may be particularly sensitive 

areas. For example, at forest and shrubland ecotone margins, and at subalpine-alpine ecotones, digital global vegetation models suggest significant 

changes, where life forms and plant community composition may suddenly 

shift after disturbances. Within the MMC forest, which falls within midmontane and valley bottom environments, there may be only small differences in environments when comparing past and future range of variability, 

but the degree of difference will vary with topography and ecoregion.

Disturbances

• Significantly altered disturbance regimes exist as a result of 150 years of 

Euro-American land use, altering the manner in which systems behave.

In general, mixed-conifer forests are on a trajectory leading to further divergence from a resilient condition.

• Wildfires, along with insect, pathogen, and weather disturbances, historically did the bulk of the work to continuously restructure and recompose the historical landscape, providing sustainable patterns of terrestrial 

and aquatic habitats, and supporting processes. Several forest insects (e.g., 

bark beetles and defoliators) and pathogens (e.g., dwarf mistletoe and root 

diseases) are notable disturbances in this region today and they are imparting 

influences at uncharacteristically high levels.

• The disturbance ecology and resulting vegetation of the mixed-conifer 

type is influenced by the dominant disturbance regimes of the local 

landscape. Historical fire regimes in dry and MMC forests differed across a 

broad range of spatial and temporal scales in response to local and regional 

variation in climate and weather, topography, soils, and fuels. Where dry 

mixed-conifer forests are a dominant feature within a landscape, the MMC 

forest often is influenced by more frequent fire. The converse is also true. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

• Small and medium sized fires (<1000 ha in size [2,471 ac]) were most 

numerous, comprising 85 to 95 percent of the fires, but representing no more 

than 5 to 15 percent of the total area burned. Larger fires (>2000 ha in size 

[4,942 ac]) were least abundant, but accounted for the majority of area 

burned.

• Low-, mixed-, and high-severity fires all occurred in dry and MMC forest 

but the relative portion of these fires varied across ecoregions. Surface fire 

effects coming from low- and mixed-severity fires tended to dominate in dry 

forests, and local topography was especially influential during common events. 

Patches of high-severity fire resulted from rare or extreme weather and climatic 

events. Low-severity fires within MMC forest may have been more common in 

drier warmer ecoregions with less topographic relief. High-severity fires within 

MMC forests appear to be more common in cooler and wetter ecoregions and 

areas with stronger topographic relief. Low-severity fires occurred commonly 

in moist forests where they were intermixed with dry forests; high-severity fires 

in moist forests may have been more common where moist forests were intermixed with wet and subalpine forests. 

• We are in the early stages of anthropogenically induced climate warming 

in eastern Oregon and Washington, and we anticipate significant vegetation and disturbance impacts to dry and MMC forests during this century. Over the 21st century, climate change impacts will increase in magnitude 

and extent, transforming some forests. Impacts to terrestrial ecosystems will 

include increased fire frequency, severity, and burned area, increased susceptibility to insects and diseases, and increased presence of invasive plant and 

animal species. Climate change will likely reduce or eliminate some subalpine 

habitats and snow cover that are essential to the survival of some wildlife 

species.

Vegetation

• Fire exclusion, silvicultural practices, agriculture, livestock grazing, 

intensive road and rail development, and introductions of alien plant species have significantly influenced the structure, composition, and disturbance 

regimes of many forests. 

• Dry and MMC forests represent a broad range of potential vegetation 

types and include the grand fir, white fir, and Douglas-fir series. MMC forest 

falls within a gradient between the dry ponderosa pine and dry mixed-conifer 

forest and woodland types at the lowest end of the moisture gradient and subalpine and wet conifer forests at the upper end of the gradient. MMC forests are 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

often intermixed with dry mixed-conifer forests on the lower end and wet (e.g., 

western hemlock, western redcedar [Thuja plicata Donn ex D. Don], Pacific 

silver fir), or subalpine forests at the upper end of the gradient. The neighborhood a forest type lives in can influence the nature and extent of processes 

that are influential. We do not provide a precise definition of the mixed-conifer 

plant associations for different ecoregions or national forests. Agency ecologists 

are best suited to make the final decisions on MMC types occurring on each 

national forest. 

• A large number of successional pathways and old forest conditions 

historically existed in the MMC forests of eastern Oregon and Washington 

as a result of the environmental complexity and disturbances that shaped 

them. Some old forests were the result of repeated low-intensity fire that 

maintained multicohort single-stratum condition of fire-tolerant species, while 

others developed to complex, multiple-strata structures that occasionally 

experienced mixed- or high-severity disturbances. Managers have options to 

shape the trajectories of vegetation patches and landscapes along these different 

pathways. However, targeting a single developmental stage as a management 

objective does not fit with variability of the mixed-conifer forest. 

• Fire- and drought-tolerant trees of medium diameter (about 41 to 64 cm 

[16 to 24.9 in]) and large diameter (more than about 64 cm [25 in]) are the 

backbone of wildfire- and climate-tolerant landscapes, and are an essential 

component of wildlife habitat. The occurrence of older trees and older forests 

currently is far below the historical range of variability, despite their ecological 

importance. 

• Areas of ecologically diverse, early-seral grass, shrub, and seedling- or 

sapling-dominated forest patches are in short supply in some landscapes.

Historically, these areas would have been created and often maintained by 

mixed- and high-severity fires, complete with fire-killed snags and down logs. 

The largest fire-killed snags and down logs would have lasted a long time and 

provided needed plant and animal habitat. Grassland and shrubland patches 

were historically quite abundant on forested PVT settings, owing to variability 

in wildfire regimes and frequently reburned areas. It is likely, according to 

climate change projections, that grassland and shrubland conditions will be 

more common in forested PVT settings. 

• The assumption that plant association groups (e.g., moist and dry 

mixed conifer) can be used to infer historical disturbance regimes is 

only moderately true. Limited studies suggest considerable variability in 

Fire- and droughttolerant trees of 

medium and large 

diameter are the 

backbone of wildfireand climate-tolerant 

landscapes, and are 

an essential component of wildlife habitat. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

disturbance regimes within and between moist and dry mixed-conifer types. 

They both contain components of the mixed-severity regime, which is a highly 

variable disturbance regime. Managers need a variety of information sources 

(e.g., known history, landscape context) in addition to plant association types 

when assessing the historical and future range of variability for a landscape.

• In many areas of the mixed-conifer type, the density of large fire-tolerant 

trees has declined from historical levels largely because of past logging 

and recent high-severity fire. The density of mid-sized trees may have 

increased; most of these are shade-tolerant species that reduce resiliency 

of the MMC forest. 

Wildlife and Fish

• The diversity and juxtaposition of patch types of differing composition 

and structure that were produced by historical mixed-severity fire regimes 

provided a variety of habitat resources to resident wildlife. A key concept 

for understanding animal distribution and abundance in MMC forests is that 

animals need to acquire a variety of resources to meet their life-history needs, 

and most animals use a variety of different habitats and structural features to 

acquire those resources. The mosaic of conditions provided under historical 

mixed-severity fire regimes provided a rich variety of habitat features for native 

wildlife.

• Different stand development stages provide different habitat structures 

and resources for wildlife: Recently disturbed patches tend to support high 

plant productivity, and often exhibit a particularly high diversity of plant and 

animal species, including many specialist species.

Even-age young forest patches generally support less diverse and abundant 

animal communities than are found in other stand development stages, but can 

provide important ecological functions, depending on specific habitat conditions and landscape context.

Older forests with a diversity of tree ages and sizes (including large old 

trees) provide many unique ecological functions. Big old trees, living and dead, 

standing and down, provide unique and important habitat structures within 

old forest stands. The multilayer canopies found in older stands contribute to 

unique thermal characteristics within stands and provide structural complexity 

important many species.

• Natural disturbance processes play a key role in the development of 

stand structure conditions and landscape patterns that determine habitat 

values for animals. Endemic levels of disturbance and pathogens (including 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

dwarf mistletoe) can contribute to stand and landscape heterogeneity, while 

large-scale, high-intensity disturbances can reduce stand and landscape heterogeneity. Balancing the risk of long-term loss of stand structure and landscape 

heterogeneity with the retention of current ecological values often associated 

with the presence of forest pathogens and local high fuel loads is a fundamental 

challenge for land managers.

• Biological legacies (including big old trees, snags, and logs) provide important habitat structures across all stages of stand development. Within-stand 

structural diversity is generally much greater in stands with a variety of tree 

age and size classes, even if those stands are recently disturbed or dominated 

by younger trees. Big trees and logs are often a legacy of previous stand conditions that have been retained after some disturbance event, like fire or harvest. 

The variety of extremely valuable habitat structures provided by these large old 

trees include cavities, large branches, broken tops, brooms, and platforms. 

• Recent wildlife habitat assessments have reported a widespread reduction in habitat values relative to historical conditions for wildlife associated with early-seral, open forest, and postfire habitats. Old forest habitat 

conditions show less decline at a regional scale, but patterns are variable across 

sub-basins. Owing to the variation in habitat trends across the interior Pacific 

Northwest, managers need to assess the trends in their local subwatersheds for 

appropriate guidance on wildlife habitat management needs.

• Management activities focused on restoration of historical habitat patterns 

and stand structure conditions can have a variety of effects on wildlife 

populations. At a stand scale, restoration treatments tend to favor those species associated with more open conditions and increased understory vegetation 

diversity, and have the potential to reduce abundance of species associated with 

closed-canopy, old-forest conditions. However, responses can be quite variable 

depending on the intensity of the treatment, and although the abundance of 

individual species can change, restoration treatments have generally not been 

shown to cause substantial changes in species diversity.

• Loss of old-forest structures to large-scale, high-intensity wildfire is a concern for all old-forest species, including northern spotted owls. Landscape 

conditions that are resilient to intermittent disturbances will be most likely 

to provide a shifting mosaic of old forest habitat conditions for all old forest 

species over time. Managing for patterns that continually bring stands into 

old forest conditions is also important because we cannot rely on existing old 

forest stands to remain in that condition over long time periods. This approach 
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GENERAL TECHNICAL REPORT PNW-GTR-897

of maintaining a shifting mosaic of old forest conditions is likely to be an 

increasingly important concept for old-forest wildlife conservation under future 

disturbance regimes that are anticipated under many climate change scenarios. 

Conservation of unique forest structures (particularly big old trees) is important, but it will be most effective if it is done in the context of sustainable landscape patterns.

Management Applications in the Field

• Ecological restoration has become a principle objective that drives current 

management on national forest system lands in the Western United States. 

It is defined as “the process of assisting the recovery of an ecosystem that 

has been degraded, damaged, or destroyed. Ecological restoration focuses 

on re-establishing the composition, structure, pattern, and ecological 

processes necessary to facilitate terrestrial and aquatic ecosystem 

sustainability, resilience, and health under current and future conditions.” 

The scientific thinking on restoration has evolved as we learn more about 

land use change effects, climate change, paleoecology, and socioecological 

interactions (Hobbs et al. 2011). In using the term “restoration,” our intended 

meaning is that restoration involves restoring degraded ecosystems to a 

desired state considering historical and future ranges of conditions. Where the 

historical conditions strongly resemble the predicted future range of variability, 

they will be quite relevant. Where they do not, the focus will be on the future 

ranges. For example, the concept of socioecological resilience focuses on 

the adaptive capacity of species, ecosystems, and institutions rather than 

restoring or recovering a condition. In this report, we define restoration as the 

applied practice of renewing degraded and damaged landscapes, habitats and 

ecosystems with active human intervention. 

• Rates of environmental change vary across eastern Oregon and Washington, 

and as a consequence some ecosystems have attributes that may still be similar 

to their HRV. In other ecosystems, however, attributes and entire ecosystems 

are clearly out of their HRV. For purposes of understanding and prioritization, it is important to assess the degree of landscape departure from the HRV. 

However, there is obvious importance for considering the future range of variability (FRV) and how that will influence vegetation. It is important to consider 

the dynamics of ecosystems that are possible as a result of climate change, 

changing land uses, and evolving social values. Projections or scenarios of 

FRV recognize the important implications of climate change on forests (Fettig 

et al. 2013). 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Chapter 5—Management Considerations

In the midst of complicated social and political forces, forest managers make 

decisions that require the application of complex scientific concepts to case-specific 

project conditions. Decisions often must balance risks (e.g., elimination of fuels 

hazards vs. preservation of old-forest conditions) while acknowledging and allowing for uncertainties. Decisionmakers also must weigh tradeoffs associated with 

alternative courses of action to obtain multiple-use policy and land management 

objectives. We acknowledge this difficult task and the concurrent need to have and 

thoughtfully apply thoroughly the body of available scientific information.

It is not the role of the research community to direct management decisions, 

but it is appropriate to synthesize research and its core findings, and underscore 

key management implications of that research in specific management contexts. It 

is also the role of researchers to work alongside managers and seek to learn from 

their successes and failures. Here we provide considerations for management and 

emphasize that their application to local and regional landscapes requires the skill 

and knowledge of local practitioners to determine how best to apply them to each 

local situation they encounter, and its particular management history. Legacy 

effects matter and one size does not fit all. 

In the following section we synthesize the principle scientific findings that have 

been gleaned from the body of scientific literature (summarized in chapter 4) as it 

pertains to management of moist mixed-conifer (MMC) forests. These constitute 

the “take home” messages that are intended to assist land managers.

Key Concepts to Consider in Management of 

MMC Forests

• Resilience at regional scales is fostered by heterogeneity in patterns of 

local landscapes, but not just any heterogeneity will do. Heterogeneity that 

is useful to maintaining resilience is that which is supported by the inherent variability of the local climate, geology, and disturbance regimes of each 

subregional locale. The variability of the regional landscape mosaic should 

be represented in unique patterns of local landscapes. Management for resilience at broad scales can promote this variability. 

• Overlap in the historical range of variability (HRV) and future range 

of variability (FRV) may be useful to defining desired local landscape 

patterns (fig. 44). If landscapes reflect these overlapping envelopes of an 

eco-region, they are likely to be more resilient and conserve more future 

options for management. If all local landscapes look the same, the regional 

landscape will have been simplified. We make this suggestion because of 

high uncertainty about the use of the FRV alone. 

One of the roles of 

researchers is to work 

alongside managers 

and seek to learn from 

their successes and 

failures.

Resilience at regional 

scales is fostered 

by heterogeneity 

in patterns of local 

landscapes.
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GENERAL TECHNICAL REPORT PNW-GTR-897

• Managing for resilient landscapes that have patterns consistent with the 

range of variation under current and expected future disturbance regimes 

provides a conceptual starting point for capturing the habitat needs of 

native wildlife. Native animals evolved in the context of historical disturbance 

regimes and resultant landscape patterns. Landscape resilience is also important to animal populations because it represents the tendency of a post-disturbance landscape to return to conditions to which the native animal community 

is adapted. Landscapes that are not resilient may shift into novel environmental 

conditions that can contribute to substantial changes in the animal community 

and loss of or change in biodiversity.

• Some native wildlife species have been affected by threats not related to 

habitat amount and distribution, including ecological interactions with invasive species and sensitivity to effects of specific human activities (e.g., livestock 

grazing or residential, highway, or forest road development). Conservation of 

these species often requires specific strategies that address habitat in combination with the specific risks to which they are sensitive.

• Well-connected patterns of habitats across regional landscapes are important to sustaining diversity of native species. A regional goal is to maintain 

interconnected networks of habitats that link ecoregions and subregions that 

would normally provide suitable habitats. Understanding how patterns on the 

Past, Present, Future Conditions

Substantial overlap

Moderate overlap

No overlap

HRV

CC

FC

HRV

CC

FC

HRV CC FC

Need

Low

Moderate

High

Management

feasibility

Low

Moderate

High

Potential

effectiveness

High

High

Low

Figure 44—Conceptual illustration of the extent to which current ecosystem conditions (CC) in a 

place differ from the historical range of variability (HRV) in conditions and from projected future 

conditions (FC).
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

natural landscape (including vegetation communities and landforms) interact 

with human-created features (e.g., major highways and residential developments) to influence animal movement and population functions is also important for maintaining landscapes that can sustain populations of wide-ranging 

species over time.

• When restoring within-patch heterogeneity, consider varying the tree 

clump and gap size distribution among patches. If patches within local landscapes have the same structural characteristics, patch heterogeneity will have 

been simplified. Consider adapting methods like those developed by Larson and 

Churchill (2012) and Churchill et al. (2013) to the management of MMC forests. 

To do that, additional ecoregion-specific datasets will be helpful in fine-tuning 

innovative silvicultural and forest management strategies.

• Second-growth 60- to 100-year-old forests offer substantial opportunities 

for restorative management. Consider an emphasis on restoring patterns of 

successional stages that better match the variability of the inherent disturbance 

regimes. A large acreage of highly productive MMC forest, managed via regeneration and partial harvests during the 20th century, is in this general age class. 

Resulting forests are intermediate-aged and contribute to simplified landscape 

patterns. 

• Consider restructuring large areas of the dry and MMC forest on the 

landscape to return to more resilient forest conditions. After more than a 

century of forest and fire management, the current mixed-conifer landscape has 

developed more than a century’s worth of successional inertia (compositional 

and structural change) and fuel accumulation. Wildfires and insect outbreaks 

are resetting conditions on the landscape; spatial allocation is driven by ignitions, fire weather, and fuels; changes are occurring suddenly; and the window 

of treatment opportunity for restoration is growing shorter. Consider identifying patches in key geographic, topographic, and edaphic locations that because 

of soils, aspect, elevation, and site climate are not likely to sustain these dense, 

drought- and disturbance-intolerant conditions. Likewise consider reestablishing the inherent landscape heterogeneity, using topography as the underlying template. Where early-seral species would naturally dominate (ponderosa 

pine [Pinus ponderosa Lawson & C. Lawson], western larch [Larix occidentalis Nutt.], and western white pine [Pinus monticola Douglas ex D. Don]) and 

natural regeneration is improbable (i.e., grand fir [Abies grandis (Douglas ex 

D. Don) Lindl.], white fir [Abies concolor (Gord. & Glend.) Lindl. ex Hildebr.)], 

Second-growth 

60- to 100-year-old 

forests offer 

substantial 

opportunities 

for restorative 

management. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

and Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] will likely dominate 

for a long time), consider regenerating these areas, as is appropriate to the 

topo-edaphic conditions. 

• To the extent practicable, consider reestablishing the inherent resilience 

capacities of ecological systems. This can be done by restoring ecological 

processes as the foundation of ecosystem resilience. A keystone priority may be 

to reestablish the central role of the natural or inherent fire regime as the source 

of reinitiation, development, and maintenance of a heterogeneous landscape 

mosaic. Where feasible and socially acceptable, create management conditions 

that enable natural processes to do important work on the ground that is otherwise expensive and less effective to emulate with direct management. Doing 

this will be economically beneficial, contribute to fire and climate resiliency, 

and improve diversity of wildlife habitat conditions. Repeated treatments over 

time will be required to achieve such goals given the century’s worth of successional inertia and fuel accumulation that has occurred in many areas.

• Expect surprises and consider maintaining a broad range of management 

options. Expect rare events; they have always influenced the majority of 

the landscape. Twenty-first century climatic changes will result in conditions 

that differ from the pre-management era, and differ from those we are currently 

experiencing. Managers and scientists will work to constantly improve the 

accuracy of future projections, but it may remain prudent to expect the unexpected. There is much uncertainty in the complex interactions between a changing climate, environments, disturbance regimes, and the diversity of organisms 

and communities in our ecosystems. 

• Consider providing a full complement of vegetation cover types and successional stages within mixed-conifer landscapes. Patterns and variability 

of cover types and successional stages consistent with the inherent fire regimes 

may be desired. Managers can reduce the need for a more highly engineered 

and costly resilience (that is also more uncertain as to ecological and spatial 

outcomes) through managing to create or recreate a landscape pattern that 

would be formed by the patterns and variability of native disturbance regimes.

• Manage with entire landscapes, all ownerships, and all vegetation types in 

mind. Mixed-conifer and other forest types do not exist in isolation and are not 

confined to ownership boundaries. Disturbance regimes and habitat conditions 

of neighboring types are interconnected and interrelated, and are best addressed 

by working together with adjacent landowners.

Expect surprises and 

consider maintaining 

a broad range of 

management options. 

Expect rare events; 

they have always 

influenced the majority 

of the landscape.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

• Consider maintaining a backbone of large and old early-seral trees as a 

primary and persistent structure of all mixed-conifer forests. If they have 

been removed by timber harvest, regrow them. This can be a key to restoring 

climate and wildfire resilience and reestablishing many core wildlife habitat 

values. Consider favoring ponderosa pine in the dry mixed-conifer forests, 

and western larch, western white pine, sugar pine (Pinus lambertiana), and 

Douglas-fir in MMC, consistent with local conditions. 

• Consider maintaining a backbone of large standing dead and down trees, 

and live deformed trees (those with broken tops and limbs, cavities, and structures for nesting and denning sites) to provide structures for wildlife use. As a 

result of past timber harvest and “sanitation” treatments, these fine-scale structures are in short supply in most areas. Typically, it takes decades to centuries 

for a once healthy tree to develop the proper characteristics of such a “wildlife” 

tree, but techniques are available to create and accelerate their development. 

Information for both snag and down wood management in green and dead 

stands can be found in the Decayed Wood Advisor (DecAid) (http://www.fs.fed.

us/r6/nr/wildlife/decaid/). Manage these structures as needed (i.e., remove if 

necessary) in developed recreation areas, such as campgrounds and trailheads, 

where they could pose a threat to human safety. 

• Old-forest refugia located in suitable locations may be important to retain. 

Dense, multilayered mixed-conifer old forest patches are typically not sustainable in many landscapes of eastern Oregon and Washington unless they reside 

in environmental settings (e.g., valley bottoms and north-facing slopes) that 

enable them to persist (i.e., suitable topo-edaphic, climatic, and disturbance 

contexts) by escaping common disturbances. Likewise, focus restoration efforts 

on developing future old-forest patches in these areas, especially where old forest exists in short supply.

• Consider reducing the density and layering in the neighborhood surrounding old-forest refugia, and favoring fire-tolerant species to help reduce the 

risk of loss of multilayered old and otherwise structurally complex forest patches to high-severity fires. Loss of some existing complex structural 

patches is an inevitable but reasonable tradeoff for maintaining old forests in 

fire-prone environments.

• Restoring the natural variability of wildfire regimes may be a key to 

restoring the physical processes that create productive aquatic habitats in 

streams. Anadromous and cold water fish are fire-adapted species. The natural 

frequency, severity, and extent of historical fires governed the pulse of erosional 
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GENERAL TECHNICAL REPORT PNW-GTR-897

events that carried wood, rocks, and soil to streams. Native fish habitat can be 

greatly improved through restoration of the natural fire regime. 

• Consider encouraging the natural fire regime within the riparian zones 

of high-gradient (steep) stream reaches. With the exception of low-gradient 

(<5 percent slope) often fish-bearing valley bottom reaches, riparian ecosystems adjacent to high-gradient streams commonly exhibited the fire regime of 

the adjacent upslope environments. Low-gradient (flatter) reaches are routinely 

distinguished as flood plain depositional areas whose riparian vegetation is 

dominated by hardwood tree and shrub vegetation and hydrologic disturbances, 

whereas the riparian vegetation of higher gradient streams is remarkably similar to the upslope vegetation. 

• Consider focusing restoration on large, functional landscapes rather than 

on individual landscape attributes, goals, or risks, such as fuels reduction, 

timber production, or owl conservation. Although we acknowledge the need for 

short-term measures to protect key habitats, species, and resources that are currently at risk, management emphases with singular resource objectives generally marginalize other important values and eventually fail because they lack 

this larger focus. 

• Give adaptive management serious consideration. It simply formalizes learning from successes and failures. The new Forest Service Planning Rule offers 

yet another opportunity to implement adaptive management. We realize that 

many prior attempts to conduct adaptive management have failed, but it still 

represents a rich opportunity for learning, and it is how people learn, through 

structured trial and experience. Flexible management approaches employing 

evidence-based, scientifically credible methods promote learning. 

• Consider managing forests in the context of current and potential 

climate change. Rates of climate change in the past century and projected 

for the remainder of this century differ spatially across eastern Oregon and 

Washington. In some geographic settings, changes in climate in recent decades 

have altered fire regimes, increased insect infestations, and resulted in high 

levels of tree mortality. Such changes linked to climate are likely to expand 

to larger portions of the region in coming decades. Consider identifying rates 

of change in climate and ecological response over the past century and those 

projected for future decades and setting management goals and treatments 

accordingly.

Consider focusing 

restoration on large, 

functional landscapes 

rather than on 

individual landscape 

attributes, goals, or 

risks, such as fuels 

reduction, timber 

production, or owl 

conservation.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Example of Landscape Management: Okanogan-Wenatchee 

Landscape Evaluation Decision Support Tool

In eastern Washington, scientists at the Pacific Northwest Research Station 

Forestry Sciences Laboratory in Wenatchee and on the Okanogan-Wenatchee 

National Forest have developed and implemented a landscape evaluation and 

decision support tool (DST) that directly aids managers with implementing a 

comprehensive landscape restoration strategy. The landscape restoration strategy and the DST have been fully adopted on this national forest and are being 

implemented on all districts for projects that undertake restoration. 

We acknowledge that this particular evaluation and decision support tool 

represents only one example of how landscape management can be executed. 

In this instance the forest had access to extensive data sets and skill levels not 

common on national forests. This example is offered to illustrate what is possible when the necessary resources and expertise are available. 

The DST is an outgrowth of a long-standing joint research and management 

partnership, and a peer-reviewed, forestwide restoration strategy (OWNF 2012). 

Under the strategy, the objectives of landscape evaluations are to: 

• Transparently display how projects move landscapes toward resilience 

to drought, wildfire, and climate; 

• Define and spatially allocate desired ecological outcomes (e.g., adequate 

habitat networks for listed and focal wildlife species [Gaines et al., in 

press] and disturbance regimes consistent with major vegetation types); 

• Logically and transparently identify potential landscape treatment areas 

(PLTAs), treatment patches, and the associated rationale; and 

• Spatially allocate desired ecological outcomes from landscape prescriptions, and estimate outputs from implemented projects.

Landscape evaluations under the strategy assemble and examine information in five topic areas: (1) current patterns and departures of vegetation structure and composition from historical and climate change reference conditions; 

(2) spread potential for wildfires, insect outbreaks, and disease pandemics 

across stands and landscapes given local weather, existing fuel and host conditions; (3) damaging interactions among road, trail, and stream networks; (4) 

wildlife habitat abundance, distribution, and sustainability; and (5) minimum 

roads analysis (i.e., which of the existing system roads are essential and affordable, and which are not) (fig. 45). 

(continued on next page)
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GENERAL TECHNICAL REPORT PNW-GTR-897

Photo

interpretation

Derived

attributes

Current conditions for vegetation,

stand-level fire, wildlife, insects

Comparison with

reference conditions

Identify multiple PLTAs, 

develop a landscape 

diagnosis and prescription

Fragstats and

Netweaver

Terrestrial landscape priorities

Aquatic landscape priorities

Landscape fire

modeling

NetMap roads/aquatics

ecological evaluation

Line officer 

selects PLTA

Project decision,

implementation

Develop PLTA

prescription, game

treatment options in

EMDS, prepare

integrated purpose

and need

Minimum roads analysis

socioeconomic roads

evaluation

Determine project areas and

treatment prescriptions

Field work and 

NEPA documentation

Criterion

Decision Plus

Monitoring and adaptive management

informs project implementation, future

projects, and restoration strategy updates

+

Process

Data

Software

Product

Figure 45—Workflow diagram of the Okanogan-Wenatchee National Forest Decision Support Tool (DST). The DST 

was implemented in EMDS, the Ecosystem Management Decision Support software (Reynolds and Hessburg 2005, 

Reynolds et al. 2003) using the NetWeaver and Criterium DecisionPlus software utilities. FRAGSTATS (McGarigal 

et al. 2002) spatial pattern analysis software was used to characterize spatial patterns of vegetation composition and 

structure in current subwatersheds and for the historical range of variability and future range of variability reference 

conditions. FlamMap and Randig (Ager et al. 2007, Finney et al. 2007) were used to simulate probable landscape scale 

wildfires. PLTAs are potential landscape treatment areas that emerge from landscape evaluations.
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The restoration strategy is a living document, which is updated and 

expanded to include new relevant science and technology. Likewise, with 

each implemented project, new utilities are added to the decision support 

tool. Landscape evaluations in the DST examined current vegetation spatial 

pattern conditions and quantitatively compared them with both historical (past 

1900s-era climate, the HRV) and future, mid-21st century climate reference 

conditions (the FRV), which represent plausible ranges of pattern variability 

for these periods. Current vegetation conditions were established via interpretation of stereo pairs of aerial photos using standard aerial photogrammetry 

techniques. The samples for each of the reference conditions were developed 

using the same vegetation attributes and these same photogrammetry techniques. Evaluated areas were typically small groupings (two or more) of 

modern-era subwatersheds (12-digit HUCs). 

Once current vegetation conditions were interpreted and field verified, the 

most significant departures of local landscape pattern conditions from reconstructed early 20th century reference conditions (the HRV) were evaluated 

in the DST. These reconstructed conditions were obtained from the Interior 

Columbia Basin Ecosystem Management Project (ICBEMP) mid-scale assessment dataset (Hessburg et al. 1999a, 2000a). Since that project, these reconstructed conditions have been summarized for each of the major ecological 

subregions (Hessburg et al. 2000a) on the two national forests. After the initial 

departure analysis, departure from a second set of future warmer and drier 

climate change conditions (FRV) was evaluated. The FRV conditions were 

represented using historically reconstructed conditions of an ecological subregion whose climatic conditions best match those predicted under warming. 

This approach used what are often referred to as “climate change analogue 

conditions” and was intended to show the range of patterns that would emerge 

with climatic warming and the associated biotic conditions and disturbance 

regimes. The results of the two departure analyses were used together with 

equal weighting to determine the most significant changes in forest vegetation 

structure and composition in the evaluated subwatersheds (Hessburg et al. 

2013). Equal weighting was used when considering the HRV and FRV conditions to maximize management options in future landscapes because of the 

scientific uncertainty surrounding predicted climate change predictions.

Reference conditions were developed for each unique ecological subregion 

to reflect the range in patch sizes and successional pattern conditions that are

(continued on next page)
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GENERAL TECHNICAL REPORT PNW-GTR-897

(from page 155)

typical for the biota, climate, geology, and disturbance regimes of a physiographic region (Hessburg et al. 2000a), whether they occurred before the 

advent of management, or they occur at some time in the future. Results 

of departure analyses were reported by potential vegetation type (PVT) to 

provide managers with a mechanism for establishing on-the-ground treatments in response to departure analysis. Departure analysis results can inform 

development of landscape-level restoration prescriptions that are designed to 

specifically address the most significant departures. Resulting prescriptions 

can help restore landscape vegetation conditions that are better adapted to 

wildfires, native insects, pathogens, and predicted climatic warming. 

In addition to the vegetation departure analysis, departure analyses 

were implemented for habitats of regionally listed and focal wildlife species 

(Gaines et al., in press), and for patch scale fire behavior attributes under 

a 90th percentile wildfire burn scenario (Hessburg et al. 1999a). Departure 

analyses were also completed that reflect landscape changes in vulnerability 

to a variety of major insects and pathogens using models developed for the 

ICBEMP project (Hessburg et al. 1999a, 1999b, 2000a). 

A landscape-scale wildfire analysis was also completed and programmed 

into the DST, which characterizes the most probable wildfire flow across the 

large ecoregional landscape when typical wildfire season wind direction, 

wind intensity, terrain routing of wind and wildfire, and thousands of randomized ignitions are considered. The landscape-scale wildfire analysis provided 

concrete map depictions of the anticipated flow of large wildfires across the 

landscape. Managers can use these maps to determine where wildfire flow 

may be interrupted via strategically placed fuels treatments to reduce the 

likelihood of large events (Hessburg et al. 2013). Local landscape evaluations 

can also incorporate these insights into their landscape-level prescriptions. 

New in 2013–14, aquatic landscape evaluation utilities are being added 

to the DST. Under construction are the addition of a minimum roads analysis subroutine, stream crossing and culvert subroutines (currently handled 

external to the DST), and a module designed in NetMap (Benda et al. 2007) 

or similar software that identifies road segments that constrain stream channel migration and natural connection with the historical flood plain, separate 

existing channels from off-channel features, and contribute the most to instream sediment. For additional details about the entire landscape evaluation 

process, see Gaines et al. (in press) and Hessburg et al. (2013). 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Stand Management—Silvicultural Tools and 

Their Role in Landscape Management

Achieving landscape-level management objectives will require making explicit 

connections between patch- or stand-level and landscape-level assessments, 

especially among patch interactions within landscapes. We use the term “stand” 

to conform to the familiar nomenclature of silviculture. The term “patch” is a 

similar term used by some to describe a group of trees (O’Hara and Nagel 2013). 

The planning and operations conducted by land managers will achieve the broader 

objectives when making this kind of nested spatial relationship explicit in their 

entire planning process. Stand-level management is therefore the operational level 

to meet landscape objectives. Creating stand structures that meet these large-scale 

objectives will be a central concept to management of eastside mixed-conifer forest 

and riparian ecosystems. Silviculture represents the operational process and offers 

a matrix of options to achieve these broad-scale objectives.

Reducing stand density, altering species composition, and enhancing stand 

and landscape complexity, where appropriate, will be the central silvicultural 

objectives in many eastside landscapes based on our findings and conclusions. 

Stand densities are too high in most locations and ecological resilience is generally lacking owing to past management. For example, logging removed a disproportionate number of large early-seral dominant trees and favored simpler stand 

structures where dense stands of shade-tolerant trees homogenized both stands and 

landscapes. Land managers are advised to evaluate the fire risks of both current 

conditions and what might have developed under active fire when considering how 

to reconstruct forest structure. Most of the ponderosa pine, and the dry and MMC 

forested landscapes of eastern Oregon and Washington, had a relatively open stand 

structure under the influence of active fire (for more information, see “Wildfire” 

and table 5 in chapter 2). Nonetheless, stands had a particular horizontal and 

vertical complexity that was characterized by a dominant matrix of relatively open 

canopies with tall fire-tolerant trees, canopy gaps with patches of tree regeneration 

or shrubs, and dense patches or scattered individuals of shade-tolerant trees. The 

relative proportion of these fine-scale stand and landscape elements varied with 

environment and disturbance regimes. 

In dry ponderosa pine and dry mixed-conifer types, stands on southerly 

aspects were relatively open with a few dense patches of shade-tolerant Douglas-fir 

and grand fir. Tree regeneration and cohort development coincided with wildfires, 

but frequent fires killed the majority of the regenerating pines, such that relatively 

few survived from fire to fire, thereby yielding the appearance of many cohorts 

through time. In wetter areas, valley bottoms, and north aspects with longer fire 

Stand-level management is the operational 

level to meet landscape 

objectives. Creating 

stand structures that 

meet these large-scale 

objectives will be a 

central concept to 

management of eastside mixed-conifer 

forest and riparian 

ecosystems. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

return intervals, the MMC mosaic would have had more dense patches with shadetolerant understories or larger canopy gaps created by active or passive crown fire 

associated with mixed- or high-severity fire. 

Restoration goals that achieve both landscape and stand objectives can be met 

by directing landscape units toward the species composition and diversity in age 

class structure, and complexity in vertical and horizontal stand structure, that are 

resilient in the face of fire, insects, disease, and climate change. In many cases, 

promoting the kind of horizontal heterogeneity of stands that occurred prior to 

Euro-American settlement will greatly increase resiliency to large-scale disturbances such as insect outbreaks (Fettig et al. 2007, Franklin et al. 2013, Hessburg 

et al. 1994, O’Hara and Ramage 2013). For many landscapes, development of a 

multiscale mosaic of age and size structures of fire and drought-tolerant species 

will be the objectives. 

Another key objective, particularly in some stands where fire risk is acute, 

includes reducing fuels and associated potential for large-scale fires. This involves 

simplifying some stand structures to reduce ladder fuels or to modify understory 

vegetation and other fuels. Finally, some stand structures can be modified to restore 

old-forest single-stratum structures (e.g., O’Hara et al. 1996) where scattered 

overstory trees dominate and other vegetation is relatively scarce. This condition 

would have been common in many dry pine and dry mixed-conifer forests but also 

some MMC forests prior to settlement and management. These old-forest structures 

may be considered simple compared to contemporary stands where historical fire 

suppression has favored development of multiple strata, but these simple structures 

also exhibited a fine-scale heterogeneity of size, age, and occurrence, in clumps 

of varying size, and among gaps with varying size, which made these patches far 

more resilient to fire, insects, and drought. The result is that over the entire eastside 

mixed-conifer zone, and even in individual watersheds, some area (patches, stands, 

or small landscapes) may be directed on trajectories toward complex structures 

(e.g., a mosaic of open canopies and dense canopies characterized by multi-storied 

shade-tolerant tree species that are needed for some objectives such as northern 

spotted owl habitat) while the majority of others may be directed toward more open 

structures with a subtle but distinctive spatial, compositional, and age heterogeneity. 

Landscape-level planning will provide the guidance for these decisions.

Silviculture can encompass both passive and active approaches. A variety 

of treatment options are available to manage stands so that they develop toward 

desired structures. A central management objective is implementing silvicultural 

activities (including both mechanical treatments and prescribed burning) that 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

prepare areas for expected wildfire, to restore stand structures, or alter structures. 

Treatment options contain a wide range of methods including those that lie 

between traditional even-aged methods and uneven-aged methods (O’Hara 1998). 

Desired stand structures may be highly variable across different forest types and 

the treatments to direct stands toward these structures should also be variable. 

Implementing forest and riparian management strategies that promote the needed 

heterogeneity of mixed-conifer forests (dry, moist, and wet) across the landscape 

will require willingness to innovate on the part of land managers. There may be 

periods during stand development when the treated forest may not meet, or appear 

to meet, longer term objectives. 

Stand management will often involve social or ecological tradeoffs. Some 

restored stand structures may not be popular with some stakeholder interests when 

they result in dramatic reductions in trees or cover. Additionally, many stands 

may have reached a state where they are prone to wind damage and cannot be 

manipulated with partial harvest or light thinning treatments, in which case more 

intensive harvest may be needed to “reset” the ecological trajectory. In other cases, 

prescribed burning cannot be used without substantial alterations of existing fuels. 

In these situations, silvicultural treatments can facilitate subsequent prescribed 

burning treatments. The combination of extensive areas needing treatment, air 

quality constraints, and work-force requirements presents enormous challenges to 

land managers, especially at the landscape scale (North 2012, North et al. 2012). 

Managers are encouraged to view their work as a series of incremental steps 

intended to move systems in the direction of restoring resilience of mixed-conifer 

forests to fire and other disturbances. Restoration will require more steps in some 

places than others.

There are opportunities for silviculture to be more cost efficient by recognizing the potential for passive treatments to achieve objectives under certain 

circumstances. Passive silviculture relies on natural processes including wildfire 

and regeneration to achieve target stand structures. For example, mixtures of 

tree species with differential growth rates can result in complex, stratified stand 

structures even though the stands are even-aged. The rapid growth of western larch 

and lodgepole pine (Pinus contorta Douglas ex Loudon) in comparison to grand 

fir, evident in many mixed-conifer areas in eastern Oregon and Washington, is one 

example (e.g., see Cobb et al. 1993).

Another cost-saving strategy involves offsetting expenses of active treatments 

through commercial activities that help maintain local industries. Active components of silviculture include mechanical removal of low- and mid-story vegetation 

Managers are encouraged to view their work 

as a series of incremental steps intended 

to move systems in the 

direction of restoring 

resilience of mixedconifer forests to 

fire and other disturbances. Restoration 

will require more steps 

in some places than 

others.
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GENERAL TECHNICAL REPORT PNW-GTR-897

to restore a stand dominated by the largest early-seral trees. These restoration treatments will often involve treatments that result in removal of some commercially 

valuable trees. To meet the ecological objectives, the commercial volume could 

come from larger diameter, shade-tolerant species. Ideally, the byproduct of landscape restoration is wood fiber from ecologically undesirable components of stands 

that can help offset treatment costs, which can sometimes be quite high. 

Silvicultural treatments of stands will be more effective when directly tied to a 

landscape analysis and prescription, and tailored to resolve many concurrent issues. 

Both single- and multi-aged stand structures are naturally part of eastside forest 

landscapes. Single cohort structures often result from stand-replacement fires, 

which can be structurally mimicked by several types of silvicultural techniques, if 

a significant large dead wood component is provided. However, there is no direct 

substitute for fire and its effects (McIver et al. 2012, Stephens et al. 2012). Finescale multi-aged conditions, on the other hand, were much more common in dry 

ponderosa pine, dry mixed conifer, and MMC forests, especially where surface fire 

effects dominated, and fires were relatively frequent. Multi-aged stand management at a variety of scales offers a means to create complex structures and emulate 

the structural complexity found in forests subject to mixed-severity fire regimes. 

However, traditional uneven-aged management methods are generally inappropriate 

to achieve these ends. These tools focus on achieving certain diameter frequency 

distributions rather than meaningful structural characteristics such as numbers of 

canopy strata, crown coverage, or light penetration for regeneration (O’Hara 1996, 

1998; O’Hara and Valappil 1999). These tools also tend to encourage stand structures that are constant from one location to the next and over time. 

Instead, managers can focus on retaining meaningful structures that build 

on existing structural features that vary from site to site and where patchiness of 

cohorts within stands may vary from fine (groups of trees) to rather coarse (acres 

to parts of acres) grains. For example, some large and old ponderosa pine and 

other large young forest dominants would ideally be retained on sites where they 

are scarce, regardless of the effect on a diameter distribution curve. Simpler twoaged stands offer the opportunity to form structures that fit historical disturbance 

regimes, retain some cover at all times, and provide structural diversity within 

stands and across landscapes. The multi-aged approaches in eastside forests may 

therefore not resemble traditional uneven-aged silviculture (e.g., O’Hara and 

Gersonde 2004). Instead, guides with a high level of flexibility will be needed to 

encompass a wide range of stand structural features. Examples of flexible prescriptions and stand structures are available for ponderosa pine (O’Hara et al. 2003) and 

lodgepole pine (O’Hara and Kollenberg 2003).
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

In some MMC forests where native disturbance regimes previously created 

patches of high-severity fire and, in turn, patches of early-seral grass, shrubs, or forest, the wildlife habitat associated with early-seral conditions may be lacking. This 

may be due to a lack of stand-replacement disturbance or because recent timber 

harvest has consisted of partial removal treatments that consistently left some of the 

more dominant trees. In situations where early-seral structure is clearly underrepresented, treatments targeted at creating early-seral grass, shrub, seedling, sapling, 

and pole-sized tree patches within the forest may be needed, complete with large 

snags and down logs, as appropriate. Variable retention systems that leave residual 

trees after harvest (e.g., Beese et al. 2003, Mitchell and Beese 2002) are one way to 

develop these stand structures. 

Existing stands without desired variability in stand structure may be managed to enhance stand-level variation with variable-density thinning (VDT) and 

other similar methods. VDT is used to enhance variability in homogeneous stands 

by thinning to a range of densities within a single stand (Carey 2003, O’Hara et 

al. 2012). This general concept can be applied to any stand to any degree where 

increased variability is an objective (e.g., see Harrod et al. 1999). However, generalized VDT protocols do not exist because these protocols are usually not transferable 

from one stand to another, so prescriptions will be needed for individual stands. 

Systematically achieving variability in managed forest landscapes is a major 

change from past practices because traditional silviculture emphasized homogeneity rather than heterogeneity. The challenge will be finding ways to systematically 

integrate variability into stand management. Recent efforts are making meaningful 

progress toward development of operational marking rules and procedures for 

implementing VDT in a variety of vegetation types (O’Hara et al. 2012). Larson and 

Churchill (2012) cautioned that typical global pattern analysis ignores within-pattern variation that is often the key feature of forest restoration. They recommended 

maintaining mosaic structures within patches that often exist at quite small spatial 

scales (<0.4 ha [1 ac]) and developing marking guidelines that focus on creating or 

maintaining individuals, clumps, and openings (ICO) as key structural elements 

(Churchill et al. 2013, Larson and Churchill 2012) (fig. 46). This approach has 

been employed recently and demonstrates the innovation that is emerging in forest 

management to achieve these varied landscape objectives (Churchill et al. 2013, 

Franklin et al. 2013, Stine and Conway 2012). More extensive datasets are needed 

from additional physiographic regions and potential vegetation type settings to better understand the variability in within-patch clumpiness that can inform marking 

guidelines and silvicultural prescriptions throughout the mixed-conifer forest.

Systematically 

achieving variability 

in managed forest 

landscapes is a major 

change from past 

practices because 

traditional silviculture 

emphasized homogeneity rather than 

heterogeneity. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

In the case of the diverse mixed-conifer forests of eastern Oregon and Washington (dry, moist, wet) the ICO method identifies important components of heterogeneity at fine spatial scales that should be considered in any silviculture prescription. 

Knowledge about the landscape context, disturbance history, environment, and 

other management goals will need to inform how the ICO goals are set. For example, in MMC where grand-fir invasion has created large areas of dense canopies, a 

stand-level silvicultural prescription may be focused first on creating relatively open 

conditions by removal of most grand fir stems (subject to other management objectives) and second on the spatial patterning of individuals, clumps, and openings in 

the remaining early-seral species-dominated stand. These considerations may be 

sequenced or concurrent, depending upon the particular vegetation conditions, and 

other relevant contexts. 

Figure 46—Example of a 32-ha (80-ac) ponderosa pine and Douglas-fir treatment from the Okanogan-Wenatchee National Forest. 

The treatment was designed to restore a pattern of individual trees, clumps, and openings consistent with prefire exclusion conditions. The prescription included specific guidelines for retentions of clumps of different sizes, as well as openings (Churchill et 

al. 2013). Large openings were flagged out during layout and were often sinuous in shape. Smaller openings occurred as a result 

of leaving clumps. Large skips (0.2 to 1.2 ha [0.5 to 3 ac]) were included to protect a riparian buffer in the middle of the unit and 

other biological hotspots such as large Douglas-fir with dwarf mistletoe, concentrations of downed logs, and multistory patches. 

Note how the unit boundaries were used to create an additional “finger” skip that extends into the stand. A 2-ha (5-ac) square area 

is shown to indicate the approximate size of an area that should contain a skip or large clump to break up siting distances. For 

more details on this approach, see http://www.cfc.umt.edu/forestecology/files/ICO_Manager_Guide_V2.pdf.

Derek Churchill
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Offsite or nonlocal seed sources were commonly used to replant many plantations in previous decades. These stands frequently exhibit poor survival and 

growth. Individual trees that are clearly maladapted to a site can be removed, but 

the presence of these trees should not necessitate special operations to remove them. 

Often such trees are not producing either pollen or seed and their presence may be 

of limited ecological importance. 

Salvage treatments are an option to produce some timber from stands where 

trees have been killed by fire, insects, or pathogens. In addition to potentially 

providing wood resources to local communities, salvage treatments can mitigate 

future damages from wildfires, especially if salvage removes the smaller trees and 

associated fine fuels. However, there is typically little ecological justification for 

salvage of dead trees (Lindenmayer et al. 2008, Spies et al. 2012). Treatments to 

remove fire- or insect-killed trees are best focused on first achieving residual stand 

structural goals determined through landscape analysis including retention of snags 

and downed logs for wildlife habitat considerations (O’Hara and Ramage 2013). 

Additionally, salvage treatments can be a necessary safety measure in developed 

recreation areas, near communities, and along roads to reduce hazards.

Upper diameter limit restrictions on tree harvesting have been implemented to 

improve retention of larger trees on some public lands (e.g., OWNF 2012). Conservation of remaining large and old trees makes sense in many ecological settings 

where these structures are in short supply, especially where remaining old trees are 

fire-tolerant, shade-intolerant species. However, strict application of this restriction can prevent managers from having flexibility to achieve ecological objectives. 

For example, Abella and Covington (2006) found that in Southwestern ponderosa 

pine forests, upper diameter limits hindered abilities to achieve ecosystem goals 

and instead served primarily as an economic constraint. Likewise, in some forest 

patches, large and old trees may be more susceptible to supporting and sustaining 

bark beetle infestations (Fettig et al. 2007), so some discretion is needed. 

Similar constraints exist in eastside forests where these arbitrary limits on 

harvested tree diameters lead to an unsustainable abundance of large, shadetolerant trees that actually impede regeneration of shade-intolerant and firetolerant trees. This happens on relatively productive sites where shade-tolerant 

trees, established after the advent of fire exclusion, have grown to relatively large 

diameters that exceed these arbitrary limits. The presence of such trees may also 

prevent restoration of openings or a patchy heterogeneity in stand structure. Many 

of the post-harvest stands contain large (more than about 53 cm [21 in] diameter 

at breast height) young trees with species compositions and stand structures that 
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GENERAL TECHNICAL REPORT PNW-GTR-897

are not representative of the native forests that we might expect to be resilient to 

drought stress, beetle infestation, changing climate, and other ecosystem stressors. 

In those situations, active management that may include the harvest of some 

medium- and large-size trees may produce ecologically enhanced stand structure 

and species compositions. Management options in these young, productive stands 

should take into account historical stand structure and species composition, using a 

landscape-scale context to help ensure that project implementation fits into overall 

restoration and desired future conditions. That said, large and old trees, particularly 

of shade-intolerant and fire-tolerant species, are essential elements to include in 

any eastside landscape. However, strict age or size limits on tree harvest that are 

not sensitive to site conditions, disturbance history, and topo-edaphic settings can 

hinder some restoration efforts and may reduce resiliency. Rules of thumb provide 

helpful guidelines but departures from these may be allowed with well-reasoned 

explanations.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

The social agreement and institutional capacity for restoring moist mixed-conifer 

(MMC) forests is every bit as important as the scientific foundation for doing so. 

The ability to institute the kinds of management changes managers will consider is 

directly a function of the capacity of the entire affected community to form working partnerships and a common vision. Thus, this section focuses on (1) the social 

acceptability of different types of restoration treatments among the general public; 

(2) collaboration as a means for developing, broadening, and sustaining social 

agreement around specific restoration projects among local stakeholders; and (3) 

some ideas for how the Forest Service and its partners could approach restoration 

on national forests that would enhance the agency’s institutional capacity to implement the kinds of management strategies discussed in this synthesis document.

Social Acceptability of Restoration Treatments Among 

Members of the Public 

Public acceptance is a critical factor influencing whether or not an agency like the 

Forest Service can carry out its forest management goals (Shindler 2007). It is generally not enough for decisions about forest management to be scientifically sound 

and economically feasible; they must also be socially acceptable (Shindler 2007). 

Scientific evidence clearly attests to the need for forest restoration, as this science 

synthesis demonstrates, and most people living in the wildland-urban interface 

express a high level of support for reducing fuels on public lands that exhibit high 

fire risk (McCaffrey et al. 2013). Research from Oregon and Washington also finds 

that many members of the public recognize the need for restoration treatments on 

federal lands because of poor forest health and high fire risk (Abrams et al. 2005, 

Brunson and Shindler 2004, Shindler and Toman 2003). Nevertheless, there is often 

social disagreement about the methods used to accomplish these treatments, and the 

locations where they should be carried out. Furthermore, public acceptance of fuels 

reduction treatments can vary by both geography and social group (Raish et al. 

2007, Shindler 2007). For example, a study of nine different stakeholder groups in 

Oregon found that they were much more supportive of active management of lower 

elevation ponderosa pine (Pinus ponderosa Lawson & C. Lawson) forests than of 

upper elevation mixed-conifer forests, where the perceived need for treatments was 

controversial (Stidham and Simon-Brown 2011). This finding suggests that sciencebased planning—in which the ecological need for fuels reduction is demonstrated 

by a solid foundation of scientific evidence—is important for improving the social 

acceptability of restoration treatments in the mixed-conifer zone (Stidham and 

Simon-Brown 2011). 

Chapter 6—Social Agreement and Institutional 

Capacity for Restoring Moist Mixed-Conifer Forests 

The social agreement 

and institutional 

capacity for restoring 

moist mixed-conifer 

forests is every bit 

as important as the 

scientific foundation 

for doing so. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

Social acceptability of forest restoration activities is greatest when the perceived risk of wildfire is high, forest health is believed to be poor, and proposed 

treatments are perceived as being cost effective and successful at achieving desired 

outcomes (Bright et al. 2007, Brunson and Shindler 2004, Winter et al. 2002). There 

is less support for management actions that are perceived as being costly, producing long-duration smoke, posing a risk of escaped or catastrophic fire, or reducing 

the aesthetic qualities of the landscape (Brunson and Shindler 2004, Winter et al. 

2002). Moreover, when citizens believe that forest restoration and fuels treatments 

are likely to have positive outcomes—economic, ecological, or social—they are 

more likely to be supportive of them (Shindler 2007).

This science synthesis suggests that both mechanical thinning and the use of 

prescribed fire will be needed to restore the resilience of MMC forests. In general, 

there is social support for both types of treatments, though prescribed fire has 

been found to be less socially acceptable than mechanical thinning in some places 

(Abrams et al. 2005, Brunson and Shindler 2004). Regarding mechanical treatments, one survey of Oregon and Washington residents (Abrams et al. 2005) found 

that 88 percent of respondents supported the selective thinning of overstocked 

forests, and 50 percent supported selective thinning of healthy forests. There 

was virtually no support for clearcutting. Another study of public acceptance of 

mechanical fuels reduction treatments from Oregon and Utah (Toman et al. 2011) 

found a high level of support for mechanical thinning among survey respondents 

(83 percent), followed by mowing understory vegetation (68 percent).

The social acceptability of prescribed fire use appears to increase when there 

is confidence in those carrying out the treatments; when it is conducted in remote 

areas away from development; when it is implemented in a reasonably sized area 

and resources are present to assure its control; when people are knowledgeable 

about fire and fuels management and prescribed fire treatments; when people 

believe it will be effective in producing desired outcomes; when it is cost effective; 

when mitigation measures are taken to reduce negative air quality and aesthetic 

impacts; and when stakeholders are involved in planning and preparing the treatments (Bright et al. 2007, Brunson and Shindler 2004, Nelson et al. 2004, Ostergren 

et al. 2008, Shindler and Toman 2003, Toman et al. 2011, Winter et al. 2002). 

Ideological perspectives may also inform opinions about the use of fire as a restoration treatment. A study from Montana found that landowners who valued forests as 

working landscapes that produced economic value disapproved of wildland fire use 

and prescribed fire because they result in “wasted” timber resources (Cacciapaglia 

et al. 2012). These landowners also saw fire as a detrimental or unnatural force that 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

needed to be suppressed. They tended to view mechanical thinning in a positive 

light, however. In contrast, almost all of the landowners who valued land for its 

naturalness and ecological values supported wildland fire use (in wilderness) as 

well as prescribed burning, as appropriate, citing the regenerative properties of fire. 

Trust and communication are key components of social acceptability. Researchers have found that the greater the trust in an agency to implement fuels treatments, 

the more supportive people are of their use (Olsen et al. 2012, Toman et al. 2011, 

Winter et al. 2002). In addition, the more informed people are about fuels management practices, the more supportive they are (Brunson and Schindler 2004). Activities that build trust between agencies and the public and increase communication 

and knowledge about fuels treatments are important. Communication and outreach 

efforts that emphasize the benefits of mechanical thinning and prescribed fire 

treatments for improving forest health and reducing fire risk to local residents are 

more likely to increase public acceptance of these treatments (Ascher et al. 2013). 

Highlighting the amount of control forest managers have over prescribed fire may 

also help increase support for it. Creating pilot demonstration projects in the places 

and forest types where restoration activities would be located is another approach 

to increasing support for them (Stidham and Simon-Brown 2011). Finally, developing fuels reduction and restoration activities through collaborative processes that 

include stakeholders in planning, decisionmaking, and partnerships (discussed 

below) is an important approach for overcoming social disagreement and lack 

of trust (Becker et al. 2011, Hjerpe et al. 2009, Stidham and Simon-Brown 2011, 

Sundstrom et al. 2012).

Shindler (2007) identified five strategies that forest managers can pursue in 

order to increase public acceptance of forest management activities: (1) view public 

acceptance as a process that evolves through building understanding, exchanging 

and discussing ideas, and evaluating alternatives; (2) develop agency capacity to 

respond to public concerns; (3) recognize trust building as the goal of public communication and outreach; (4) be sensitive to the local social and community context 

in which fire management activities are to be carried out, and how these activities 

may affect communities and forest users; and (5) encourage stable leadership so 

that shared understanding of forest conditions and fire management practices can 

develop, and so that strong agency leadership is evident in agency interactions 

with the public. It is important to remember, however, that social acceptability is 

dynamic in nature, and can change as people learn more, or when external variables 

shift (Shindler 2007). Thus, it is important for managers to pay continual attention 

to public values associated with forest restoration.
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Collaboration

Decisionmaking processes play an important role in influencing public acceptance 

of fire and fuels management activities (Shindler 2007). One of the major constraints to increasing the rate and scale of forest restoration on national forest lands 

in eastern Oregon is the capacity to reach social agreement about how to achieve it 

(Economic Assessment Team 2012). The same is likely true in eastern Washington. 

The Forest Service has emphasized collaboration as a means for developing the 

social agreement needed among diverse stakeholder groups to carry out forest restoration projects, as demonstrated by recent investments in the Collaborative Forest 

Landscape Restoration Program and language in the 2012 Forest Service planning 

rule. Collaboration can be defined as “an approach to solving complex environmental problems in which a diverse group of autonomous stakeholders deliberates 

to build consensus and develop networks for translating consensus into results” 

(Margerum 2011: 6). Consensus can range from a simple majority to unanimous 

agreement regarding a decision, but usually means reaching a decision that everyone can live with. Collaboration in identifying approaches to forest restoration in 

MMC forests is particularly important because these forests have relatively high 

economic value in addition to high recreation value, and the methods needed to 

restore them may be complex and controversial.

There are many models for collaboration associated with forest and fire management on national forest lands (reviewed in Charnley et al. 2013); the best model 

will depend on local context and the nature of the issues. A number of communitybased collaborative groups have formed around eastside national forests to address 

the ecological and economic issues associated with forest restoration, and to help 

implement solutions. In eastern Oregon, these include Blue Mountains Forest 

Partners, Umatilla Forest Collaborative Group, Wallowa-Whitman Forest Collaborative, Harney County Restoration Collaborative, and Ochoco Forest Restoration 

Collaborative. In eastern Washington, they include the Tapash Sustainable Forest 

Collaborative and the Northeast Washington Forestry Coalition. 

Research has addressed what is needed for successful community-based 

collaborative processes. For example, McDermott et al. (2011) identified three sets 

of features that contribute to successful collaboration. The first factor is external 

sources of support. This includes the support and involvement of elected officials, 

agency leaders, and key decisionmakers; enabling laws and policies; and active 

community involvement. The second factor involves having access to sufficient 

resources to enable meaningful engagement of the many entities, such as funding, 

staffing, and information. The third factor involves the capacity to perform, which 

depends on effective leadership, trust, and social capital. 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Bartlett (2012) laid out a logical and promising pathway for collaboration based 

on the collaborative process used to reach stakeholder agreement about hazardous 

fuels reduction projects at Dinkey Creek, on the Sierra National Forest in California. Successful collaboration there was based on a process that included five main 

stages: assessment, organization, education, negotiation, and implementation (see 

Bartlett 2012 for a description of these stages). Her experiences from California 

provide some key insights about what promotes effective collaboration:

• Include a broad range of participants;

• Establish a common conceptual framework, purpose and need, and 

long-term desired condition;

• Include scientific experts who serve as technical resources during meetings;

• Move some intractable issues forward without complete consensus if 

necessary; 

• Include site visits to support decisionmaking and reach agreements; and

• Have an impartial mediator to promote trust and problem solving.

Other suggestions that seem to have a positive effect on collaboration include 

timely engagement, building trust, and developing patience with the process.

The organizational capacity of collaborative groups is critical for sustaining 

effective collaborative processes. Cheng and Sturtevant (2012) provide a framework for assessing the collaborative capacity of community-based collaboratives 

to engage in federal forest management. They identify six arenas of collaborative 

action: organizing, learning, deciding, acting, evaluating, and legitimizing. Within 

each of these arenas there are different kinds of capacities associated with individuals, the collaborative group itself, and other organizations that the group engages 

with. Their framework can be used to evaluate what capacities exist within local 

collaboratives, and what capacities could be enhanced, so that investments in building and sustaining these groups can be targeted. 

Davis et al. (2012) examined the organizational capacity of community-based 

collaborative groups in Oregon that are engaged in natural resource management 

issues on public as well as private lands. They found that many of these groups have 

limited financial capacity and insecure funding. They also have small numbers 

of staff who are expected to carry out a broad range of activities, and are heavily 

dependent on volunteers. Most accomplish their work through partnerships, often 

with federal agencies. They make a valuable contribution to local-level natural 

resource management and community economic well-being. Finding ways to 

successfully engage, support, and help build the capacity of local community-based 

collaboratives east of the Cascades in Oregon and Washington is an important 
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strategy for building social agreement around the management of MMC forests, and 

for implementing forest restoration activities there.

Management of public lands today is as much a social experiment as it is an 

ecological experiment, especially when viewed through the lens of social-ecological 

resilience. The public wants to be involved. The best efforts to engage them in this 

work are not only well advised but critical to the success of restoration programs. 

It will be prudent to engage expertise in the areas of public involvement, social 

science, and economics in the cadre of players who help guide these national forest 

planning and management efforts.

Institutional Capacity

Land managers operate within established policy, constraints, and limitations as 

well as in accordance with established practices and conventions. However, some of 

the potential changes in forest management evoked within this document represent 

a departure from “business as usual.” Land managers will decide how to proceed, 

and this will depend in large part on budget, policy, local circumstances, and, 

ultimately, the judgment of line officers. However, there are some ideas and observations from past work, both research and management, that suggest some prudent 

adjustments in management approach. 

Create Landscape Management Demonstration Areas

We suggest that the identified approach to project and forest planning described 

above dovetails quite seamlessly with the intentions and expectations of the 2012 

Forest Service planning rule (36 CFR Part 219) and has value for all forms of 

ownership. In that vein, perhaps the findings and conclusions contained herein can 

be implemented both formally within the planning rule context as well as informally for current project planning on public and private lands. On public lands, 

Forest Service staff (or other public land managers) can identify the appropriate 

landscapes, sometimes including mixed ownerships, and treat them as “landscape 

laboratories” or landscape demonstration areas. Although the geographic scope of 

these “learning” landscapes is yet to be fully defined, we are generally referring to 

large drainage basins on the order of tens to hundreds of thousands of hectares 

(1 ha = about 2.5 ac).

These large landscapes can provide the context in which we evaluate past, 

current, and potential future conditions and then develop project plans and desired 

future conditions for stands, watersheds, and the entire landscape (i.e., a nested 

hierarchical spatial organization of a landscape) accordingly. In this way, the project 

and forest planners can include the crucial perspective of broader spatial and 

Management of public 

lands today is as much 

a social experiment 

as it is an ecological 

experiment, especially 

when viewed through 

the lens of socialecological resilience.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

temporal scales as they consider what to do on any given project area. It is prudent 

to put local project evaluations within this context of a nested landscape that can 

effectively consider the broader scales where the full implications of ecosystem 

drivers (e.g., fire, insects, and disease) and the periodicity of their occurrences can 

be accurately assessed.

National Forest System (NSF) staff, in collaboration with Research and Development (R&D) staff, and a variety of potential partners and collaborators will likely 

work together to develop this approach. Information from a wide variety of sources 

(e.g., experimental forests and ranges situated in the landscapes, other research 

results, NFS legacy data) can be used to develop better management options for 

public land managers and private landowners. This will also enable implementation 

of ecosystem restoration activities across the landscape, as well as the Department 

of Agriculture’s guidance to consider “all lands” in our planning and management 

activities. Within these “landscape laboratories,” Forest Service R&D, universities, 

and other partners with relevant information will be able to contribute long-term 

data records. This approach is a significant administrative and scientific challenge 

but it represents an important learning opportunity. The Forest Service has already 

made some strides in developing this concept through the relatively new Collaborative Forest Landscape Restoration Program (CFLRP). The purpose of the CFLRP 

is to encourage the collaborative, science-based ecosystem restoration of priority 

forest landscapes. Twenty projects have been established across the United States 

since 2010 to implement this concept. Perhaps this effort can expand to encompass 

larger experimental areas and a more robust role for the assistance from the scientific community.

Incorporate the “All-Lands” Initiative

The Department of Agriculture’s 2010–2015 Strategic Plan contains a goal that 

strives to “ensure our national forests and private working lands are conserved, 

restored, and made more resilient to climate change, while enhancing our water 

resources.” There are many facets to this ambitious goal and one new initiative in 

support of this goal involves use of a collaborative, “all lands” approach to bring 

public and private owners together across landscapes and ecosystems.

An all-lands approach would move landscape-level assessment and planning 

beyond the limits of the MMC forest type to other forest types, other land designations, and other ownerships that are often intermingled on logical landscape-level 

planning units. Managers can strive to involve all owners and management agencies 

and include all lands, even wilderness, in this kind of landscape planning. Additionally, these all-lands assessment efforts may indicate the need to treat areas such 
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as wilderness-designated areas with controlled ignitions and burning to achieve 

landscape-level goals such as fuels reduction and achieving target future ranges of 

variation.

Revisit Current Management Constraints; Eastside Screens

 In August 1993, the Pacific Northwest Region regional forester issued a letter 

providing interim direction to eastside national forests on retaining old-growth 

attributes at the local scale and moving toward the historical range of variability 

(HRV) across the landscape. These became known as the “eastside screens.” A 

subsequent decision notice in May 1994 amended all eastside forest plans to include 

these standards. These provisions involved a three-stage process for screening 

projects to evaluate effects:

• Riparian Screen. Defers timber harvest in riparian areas.

• Ecosystem Screen. Compares the acres of old forest stages in a watershed 

with the HRV for that structural stage.

• Wildlife Screen. Maintains options for future wildlife habitat requirements 

for old growth-dependent species. 

Eastside screens for large trees (>21 in [about 53 cm] in diameter) were intended 

to be an 18-month interim measure to screen out projects that could potentially 

harvest significant amounts of old forest and of remnant medium- and large-size 

trees. Managers were advised to avoid removal of trees above a certain diameter 

limit for a variety of reasons. The eastside forest health assessment in eastern 

Oregon and Washington had shown that remnant large trees and old-forest patches 

had been heavily targeted for timber harvest, and were seriously depleted (Everett 

et al. 1994). Public concern for loss of large and old trees also became significant 

beginning in the late 1980s and has continued to the present. Forest managers had 

to rapidly “screen” timber sales and then exclude parcels from those sales that 

included these large trees. Tree diameter was also used as a rapid and conservative 

but crude surrogate for old growth to limit removal of larger and older trees—

because analyses had not been completed to characterize old forests and old trees— 

across the variety of forest types and productivities. 

The team that developed the large tree screen designed it to be replaced by 

more in-depth landscape evaluations that considered the key departures in forest structural and compositional patterns from HRV. In fact, in 1994 the regional 

forester stated that “projects need to be designed according to the principles of 

landscape ecology and conservation biology.” Nonetheless, these screens have 

been employed for 20 years now. We are not aware of how much variation in these 
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procedures has been exercised since the screens were instituted, but the screens are 

still being used. Restoration of patterns that support natural processes and terrestrial species habitat arrangements is better achieved through evaluations that lead 

to landscape prescriptions. We know of no research that has evaluated the effects of 

the screens since they were implemented. However, other research on the ecology 

and history of pine and mixed-conifer forest (Hessburg et al. 1999a, 2005; Merschel 

2012; Perry et al. 2004) indicates that many shade-tolerant trees more than 51 cm 

(20 in) in diameter were established after fire exclusion in the early 1900s. Consequently, restoration guided by size alone will not remove all of the individuals 

of species and ages of trees that are products of the altered disturbance regimes of 

these forests. 

Furthermore, a recent report on climate change impacts on Western forests 

indicates that increased fire frequency and severity, insect outbreaks, and drought 

stress will challenge managers with novel conditions that fall outside what was 

identified from the 500+ years prior to Euro-American settlement (Fettig et al. 

2013). To develop adaptation strategies, including ones that allow for new species 

composition and changes in forest structure across the landscape, managers will 

need more flexibility than is provided under one-size-fits-all rules for silviculture, 

such as those imparted by the eastside screens. Local variability coupled with 

an uncertain climate future requires an ability to adjust to site conditions and be 

nimble, as better and more complete information becomes available.

Rather than simple rules based only on stand structure, managers can be 

guided by multi-scale evaluations that include landscape and site-level criteria. 

Such approaches would consider and remedy the key departures in forest structural 

and compositional patterns relative to their HRV and future range of variability 

(FRV), the latter of which incorporates climate change. This integration of historical and potential future conditions is likely to conserve more desired components 

of ecosystems than would occur under the use of HRV or the FRV alone. The 

departure analyses using the HRV and the FRV are not meant as a recipe, but as 

guidance about the nature of pre-management-era patterns that supported native 

species habitats and disturbance regimes. With climate warming we use the FRV 

in the same way as HRV—as guidance about the nature of the patterns that may 

emerge as species distributions and disturbance regimes (e.g., ecological envelopes) 

shift as climate interacts with land use to create novel environmental conditions and 

behaviors. As we are seeing in eastern Washington ecoregions, these envelopes of 

HRV and FRV can actually overlap quite a bit, but are clearly being deformed by 

warmer and drier conditions.

Rather than simple 

rules based only 

on stand structure, 

managers can be 

guided by multi-scale 

evaluations that 

include landscape and 

site-level criteria. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

As managers reevaluate their planning approaches using the concepts and 

findings contained in this report, they might also consider phasing out these interim 

directions. As mentioned, these screens were a short-term solution to prevent 

harvesting of larger trees. The diameter limits were intended as a crude and conservative filter to avoid harvesting old trees, pending the development of more precise 

definitions and tools. These limits are arbitrary with respect to meeting any ecological objectives because they applied to all sites regardless of the number or species of 

large trees present, or the potential of these areas to grow large trees. The limits on 

removing any tree larger than about 53 cm (21 in) whatsoever, regardless of geographic context, or age, or species, or relative abundance, or other considerations 

(e.g., forest health) within a patch can inhibit regeneration in some stands, lack any 

real landscape objectives, and impede landscape-level management and restoration. 

The concepts presented in this report address the underlying ecological objectives of the eastside screens. As these concepts are explored and implemented 

by managers, the ecological goals intended by the eastside screens can be met. 

Some individual features (i.e., nesting, roosting, and resting sites for wildlife) 

may continue to merit short-term conservation measures. However, employing a 

landscape approach to assessment, planning, and execution of forest management 

will improve our ability to effectively restructure forests to a more resilient condition and cope with impending change. Moving landscapes toward these desired 

conditions will be expensive, thus some flexibility in treatment options is needed. 

Treatments designed based on the considerations herein are capable of generating 

some revenue that will offset a portion of the costs of achieving landscape-level 

objectives. Flexibility will also help managers address long-term socio-political 

and operational issues related to eastside screens. 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Active management of vegetation in moist mixed-conifer (MMC) forests in eastern 

Oregon and Washington has declined over the last two decades because of uncertainties about management. During this time, shade-tolerant and fire-intolerant trees 

have regenerated, grown, and densified forests in many locations. Consequently 

much of the landscape of ponderosa pine and dry and MMC forests of eastern 

Oregon and Washington is in a non-resilient condition. Some of the MMC landscape would benefit from active vegetation and fire management to restore or create 

vegetation conditions and landscape patterns that are better adapted to fire, drought, 

insects and disease, and climate change than conditions and patterns managed passively. Although managers have a scientific foundation and some amount of social 

license to conduct active restoration in pine and dry mixed-conifer types, there 

is far less consensus on what should be done in MMC types. This report offers 

scientific findings and management considerations to help managers take informed 

steps toward restoring resilience to MMC forests. 

Dry, moist, and wet mixed-conifer forests coexist in landscape mosaics that 

have been altered by settlement and land use activities. On balance, the array of 

changes over the last 100 to 150 years make these forests and landscapes subject 

to high-severity and sometimes large fires (with varying degrees of mixed- and 

low-severity components), insect outbreaks, and drought-related tree mortality that 

negatively affect many ecological and social values. During the presettlement era, 

the dry and MMC forest landscapes were sculpted by low-, mixed-, and highseverity wildfires (tables 8 through 13 in app. 3) that maintained relatively open 

canopies and understories. Landscapes were mosaics, dominated by a mix of tree 

species, sizes, and ages (tables 8 through 13 in app. 3). Some ecoregions exhibited 

more mixed- and high-severity fire than others. 

Environments and vegetation patterns are diverse and complex in the MMC 

forest (e.g., historical disturbance regimes differ within potential vegetation types 

as a result of topography and landscape context). We lack uniform vegetation classifications, maps, and disturbance regime information that can be applied at local 

landscape scales. This information is sorely needed. Despite these challenges, we 

were able to identify and develop a working definition of the MMC types (potential 

vegetation types, disturbance regimes, ecoregions) within the broader mixedconifer mosaic, where structure, composition, and processes have been significantly 

altered by Euro-American activities. 

In many respects the impacts of postsettlement activity on forests and implications to restoration are the same in MMC forests as those in the ponderosa pine 

and dry mixed-conifer forests. The disturbance regimes were similar in the dry 

and moist environments, but in the productive MMC forest environments the large 

Chapter 7—Conclusions

This report offers 

scientific findings 

and management 

considerations to 

help managers take 

informed steps toward 

restoring resilience to 

moist mixed-conifer 

forests. 
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GENERAL TECHNICAL REPORT PNW-GTR-897

increases in understory density were composed of shade-tolerant species like grand 

fir or Douglas-fir rather than ponderosa pine. We identify that in the wettest mixedconifer types, restoration of resilient vegetation patterns is much less needed or 

inappropriate given their low frequency disturbance regimes. 

Given the stated restoration goals of the Forest Service, we identify a set of 

objectives and actions at stand and landscape levels that would move forests and 

landscapes on a trajectory toward resilience in the face of fire, insects, disease, and 

climate change. These include creating diverse, fire-resilient vegetation types over 

a large portion of the MMC landscape, creating seral-stage diversity and patterns 

at stand and landscape scales, using topography as a guide, maintaining habitats 

for key wildlife species, including those that need landscapes with patches of dense 

mixed-conifer forests, and maintaining ecological and physical processes that favorably reconnect terrestrial and aquatic ecosystems and support habitat for fish. 

Stands (patches) and local landscapes, conjoined with regional landscape-scale 

perspectives, are needed to achieve restoration goals. Although we address all three 

scales in this report, we have emphasized local landscape perspectives because 

they are newer and the theory and practice is rapidly developing through research 

and innovative management. For those seeking more detail on the latest stand-level 

considerations for mixed-conifer forests, other resources exist (e.g., Franklin et 

al. 2013). The geographic scope and context of forest restoration dictates an “all 

lands” approach to address the challenges of the 21st century. Vegetation succession 

and disturbance dynamics emerging from wildfires, insect and disease outbreaks, 

exotic species invasions, and multiple ownerships and management directions—set 

against a backdrop of climate change—do not observe local forest patch boundaries, land lines, or administrative boundaries. More effective land management can 

be realized through action grounded in collaboration and a landscape perspective.

A list of management considerations is provided for planners and managers 

when managing for restoration and resilience at landscape scales (see app. 1). The 

list includes guidance on development and use of historical reference conditions 

(historical range variation is a useful guide), addressing climate change (using 

potential future range of variation in designing landscapes), and a workflow plan. 

Several eastside national forests and other forest landowners in this region now 

actively employ some principles of restoration management at a landscape scale. 

The example provided from the Okanogan-Wenatchee National Forest is one of 

a number of bottom-up initiatives that explore innovative approaches to forest 

management. Many of the concepts presented in this report may be known to land 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

managers, but they are not yet in common practice. Understandably, new innovations and scientific insights take time and often require experimentation to integrate 

into standard operations. 

It makes sense for both the management and research communities to work 

together to learn about restoration and collectively stop every few years and 

take stock of where we are and what we have learned in implementing these 

ideas. This is, in essence, the conceptual core of adaptive management, and 

we encourage such flexible management approaches that promote learning and 

sharing. It also makes sense to build stronger day-to-day ties between management 

and research to enhance the real-time flow of information, improve researcher 

insights about ongoing and newly emergent problems, and to improve management 

by experimentation and adaptation. Regional land management, with all of its 

uncertainties and risks, and the significant and growing public scrutiny, is an 

enterprise that could benefit from increased adaptive management and enhanced 

science-management collaboration.

Land management activities necessarily integrate many policy and societal 

considerations, while utilizing the best available science. Managers can rely on 

well-tested, dependable methods and approaches of our respective professions, but 

can also continually avail themselves of developing innovations and technologies 

to better enable decisions and implementation. That, we believe, is evident in the 

synthesis presented in this report. We have presented a synopsis of the best available science, old and new, combined with an array of management concepts and 

principles that have yet to become common practice. We have also assessed the 

best of both traditional scientific and management approaches with some recent 

innovations that substantially improve our ability to understand how complex forest 

ecosystems function and how management influences those processes. 

Finally, when viewed through the lens of socioecological resilience, creating 

ecologically resilient landscapes cannot occur without support and consideration of 

the institutions and socioeconomic components. Restoration and renewal of resiliency in eastside forest landscapes requires economic support, forest management 

infrastructure, and social license and partnerships between management agencies 

and various publics. Human activities over the last 150 years have reduced the 

resilience of mixed-conifer forests across millions of acres of federal lands. This 

problem, a long time building and currently widespread, will require a sustained, 

comprehensive, and collaborative approach to remedy. 

Restoration and 

renewal of resiliency 

in eastside forest 

landscapes requires 

economic support, 

forest management 

infrastructure, and 

social license and 

partnerships between 

management agencies 

and various publics. 
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Acknowledgments

In the preparation of this report, many more people contributed to the final product than simply the listed authors. Accordingly, we thank the following for their 

meaningful efforts: Becky Gravenmier for helping coordinate our efforts in so 

many ways; Keith Routman for considerable expertise in editing and formatting the 

document for final publication; Tom DeMeo, Rod Clausnitzer, Sabine MellmannBrown, Dave Powell, and Mike Simpson for their input into developing table 2 and 

suggestions for text related to potential vegetation types; Ayn Shlisky for reviewing 

portions of earlier drafts and preparing some graphics; the Umatilla National Forest 

staff, particularly Dave Powell, who hosted our August 2012 workshop and field 

tour and helped with arrangements for the December 2013 workshop in Pendleton; 

the peer reviewers; and many others who offered comments on earlier drafts.

Metric Equivalents

When you know: Multiply by: To get:

Inches (in) 2.54 Centimeters

Feet (ft) .305 Meters

Miles (mi) 1.609 Kilometers

Square miles (mi2) 2.59 Square kilometers

Acres (ac) .405 Hectares

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Appendix 1—List of Practical Considerations for 

Landscape Evaluation and Restoration Planning

This list of management considerations is intended to provide an example of the 

kinds of key steps that could be taken in achieving restoration and resilience goals. 

The list does not establish a rigid process nor required steps in project planning; 

rather, these are reminders of the types of planning actions that can enable managers to achieve a broad range of landscape restoration objectives. Their application 

to a specific project is at the discretion of the responsible official, depending on the 

purpose of the action. The six major elements of this example process are presented 

first, followed by a more detailed discussion of the kinds of activities that can 

contribute knowledge through this process:

• Local landscapes can be prioritized within ecoregions for restoration. Local landscapes might be individual or groups of subwatersheds or 

watersheds. Local landscape domains should represent land units that are 

useful to terrestrial and aquatic system evaluations. Broad-scale assessment 

methodology can be used to base prioritization on the degree of vegetation 

departure from historical and future climate change reference conditions 

(including exotic plant invasions); vulnerability to large-scale, high-severity 

fire, drought, insect, and pathogen-caused tree mortality events; and priorities for terrestrial and aquatic habitat restoration and regional linkages, 

especially as they relate to listed and focal species. Other criteria may also 

be important.

• Consider engaging in stakeholder processes early and as often as 

is practical.

• Characterization of the current vegetation conditions of high-priority 

local landscapes is recommended. Using a meso-scale assessment methodology, estimate and spatially allocate the departure of current conditions from historical and climate change reference conditions; landscape 

vulnerability to large-scale, high-severity fire, drought, insect, and pathogen-caused tree mortality events; noxious and nonnative plant and animal 

invasions; and priorities for listed and focal species (terrestrial and aquatic) 

habitat restoration and improved connectivity.

• For local landscapes, we recommend developing target frequency and 

patch size histograms (distributions) of desired vegetation conditions, 

including physiognomic types, cover types, structural classes, canopy cover 

classes, density and age classes, and other related conditions, considering 

the potential vegetation type, the topographic setting, local soils, historical 
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disturbance regimes and range of variability, expected climate change and 

future range of variability, special legacy wildlife concerns, and other ecological, operational, or socioeconomic factors as needed. 

• Consider developing a method to spatially allocate and distribute these 

patch size distributions to local landscapes. Fine tune target distributions 

based on landscape context and special legacy considerations.

• Consider developing Proposed Landscape Treatment Areas (PLTAs) 

in local landscapes based on ecological and socioeconomic criteria, 

including stakeholder input. 

The following more detailed steps may be considered for local landscape 

evaluations where appropriate to the purpose of the project or planning action: 

• Characterizing and mapping the current vegetation conditions of 

entire local landscapes; include all potential vegetation types (PVTs) 

is recommended. Motivating questions are: 

▪ What are the current patterns of physiognomic types, cover types, 

structural stages or successional classes, stand density, and basal 

area classes? 

▪ What is the density and distribution of large, old, fire-tolerant/intolerant 

trees, and the density and basal area of shade-tolerant trees? 

▪ What are current surface and canopy fuel conditions? 

▪ What is the vulnerability of the current vegetation to major insect 

and pathogen disturbances? 

▪ What is the vulnerability of the current vegetation and fuelbeds 

to wildfires?

• For each ecoregion, we suggest characterizing historical reference 

conditions (ca. 1880–1900) for all PVTs. Motivating questions are: 

▪ What were the historical patterns of physiognomic types, cover types, 

structural stages or successional classes, stand density, and basal area 

classes? 

▪ What was the historical pattern and distribution of large, old, firetolerant trees?

▪ What was the historical pattern and distribution of shade-tolerant trees? 

How did their basal area and density vary? How were these patterns 

distributed with respect to topography, PVTs, and dominant processes? 

▪ What is a set of guiding reference conditions (potential restoration and 

resilience targets) based on historical patterns of structure and composition? 
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▪ What is a desired set of class and landscape pattern metrics to 

characterize these reference conditions? 

Develop reference conditions that enable a direct comparison of the 

current conditions with the historical reference conditions.

• Consider comparing current vegetation with reference conditions 

(structure, composition, disturbance regimes). Motivating questions are: 

▪ Where within the local landscapes have disturbance regimes and 

vegetation structure and composition have been significantly altered 

by Euro-American activities? 

▪ How does this departure vary by topography, soils, and PVT setting, 

and by disturbance regime?

• To strengthen understanding of sustainable landscape-scale ecological 

condition, future climate change reference conditions (ca. 2010–2050) 

for all PVTs can be characterized for each ecoregion. Motivating questions are: 

▪ What do climate change models predict to be the most likely climate 

change scenarios for each ecoregion? Identify one or two most likely 

climate change scenarios for each ecoregion; use existing information 

from models or expert opinion.

▪ What are predicted future patterns of physiognomic types, cover 

types, structural stages or successional classes, stand density, and 

basal area classes? 

▪ What is a set of guiding reference conditions (potential restoration 

and resilience targets) based on future patterns of structure and 

composition? 

▪ What is a desired set of class and landscape pattern metrics to 

characterize these reference conditions? 

Develop reference conditions that enable a direct comparison of the current 

conditions with the future climate change reference conditions.

• Assessment of the risk of high-severity fire under current fuel conditions is suggested.

▪ Tools such as FlamMap, a fire behavior mapping and analysis program, 

are currently being used for this.

▪ Terrain-routed wind flow projections can be obtained from Wind Ninja, 

Wind Wizard, or similar simulation tools.

▪ To initialize wind speeds and directions, use meteorological data from 

nearby weather stations where available, or expert advice as needed.
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GENERAL TECHNICAL REPORT PNW-GTR-897

▪ Determine the mapped distribution of burn probability, probable flame 

length, fireline intensity, rate of spread, crown fire ignition, and spread 

potential.

▪ Note the hotspots on the landscape for high-probability flame length and 

fireline intensity.

▪ Note the corridors on the landscape that most strongly tend to spread fire.

• Assessment of the departures from historical and climate change reference 

conditions in patch-scale fire behavior attributes. Motivating questions are: 

▪ How have spatial patterns of surface and canopy fuels changed with 

respect to these references? 

▪ How will changes translate to changes in expected fire behavior? 

▪ What are the key changes by PVT setting? 

▪ How are changes in expected fire behavior spatially distributed?

• Evaluating the wildlife habitat conditions (distribution, abundance, and 

connectivity of different habitat types) and assessing current conditions. 

The following steps have been used for regional-scale wildlife habitat 

assessment (Suring et al. 2011), but can be adjusted to address planning 

at other scales:

▪ Identify species of conservation concern. 

▪ Describe habitats and other important factors (e.g., sensitivity to activities associated with roads or residential developments).

▪ Group species according to habitat associations and other threats.

• Select species for assessment. Appropriate assessment target species 

could include threatened, endangered, or sensitive species, or focal 

species selected based on their association with specific habitat 

conditions and particular threats associated with human activities.

• Develop assessment models for each focal species.

• Develop conservation strategies that address management of habitat 

and other risks.

• Design monitoring and adaptive management plans.

• A terrestrial landscape diagnosis of habitat retention and vegetation 

restoration needs can be developed by considering items above.

▪ Evaluation of the road network associated with the current landscape is 

recommended.

▪ Identify all roads crossing streams, culverts, and other fish passage barriers. 

▪ Identify road segments that confine stream channels, reduce access to 

off-channel features, and contribute the most sediment.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

▪ Identify portions of the road network that most reduce subsurface water 

flow and accelerate runoff.

▪ Identify the portions of the road network that are most essential for access.

• Evaluation of the stream network of the current landscape is recommended.

• Identify and map existing anadromous and cold water fish habitats, 

especially for listed or focal species.

▪ Identify and map habitats with inherent potential for these same species.

▪ Identify and map the cold water upwelling areas within the stream network 

and the extent of their influence on water temperature.

• Evaluation of the surface erosion and mass failure potential within the 

landscape is recommended.

▪ Identify anadromous and cold water fish habitats that are prone to erosion, 

especially those of regionally listed or focal species.

▪ Identify habitats with inherent potential for these same species that are 

especially prone to erosion effects.

• An aquatic landscape diagnosis of habitat restoration needs can be derived 

by considering items above.

• Terrestrial and aquatic landscape and road restoration needs can be 

diagnosed using considerations items above.

• Using integrated risk and vulnerability assessments and socioeconomic 

opportunity factors can be effective in spatially allocating treatment priorities and identifying proposed landscape treatment areas (PLTAs) (fig. 47). 

Spatial decision support tools can help users jointly consider the spatial allocation of treatment priorities across a multitude of factors. 

▪ Assess and map current land use and land designations and whatever 

constraints, challenges, or opportunities this suggests. 

▪ Develop and identify PLTAs that restore key concerns identified in analysis.

• Among the PLTAs, vary the emphasis among the concerns to provide a 

wide variety of management alternatives to consider.

• Array and compare the social and economic benefits and costs of each 

alternative.

• Identify transitioning issues: How do we transition from a tenuous current 

condition to a more desirable and resilient future? How do we provide 

specific attention to species at risk and the elements of the landscape that 

need conservation in the near term while transitioning to the future?
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GENERAL TECHNICAL REPORT PNW-GTR-897

Assess

current vegetation

Characterize historical vegetation

and disturbance regimes

Compare current vegetation 

with reference conditions

Roads-aquatic

network analysis

Minimum road

analysis

Adjacent lands

analysis

Socioeconomic

analysis

Expected climate effects 

for future range of 

variability scenarios

Integrated risk and

vulnerability assessment

Fire risk assessment

Evaluate wildlife habitat

Set landscape priorities Stakeholder process

Develop adaptive management Identify proposed and monitoring plan landscape treatment 

areas

Figure 47—Schematic diagram of a suggested landscape evaluation workflow.

• Develop a landscape diagnosis and prescription for the best subset of alternatives based on stakeholder inputs and the condition of the resources.

• Assess potential effects of proposed work on adjoining lands and possible 

effects of ongoing activities on adjacent lands. 

• Develop a plan for monitoring implementation and effectiveness of the 

proposed treatments. Monitoring programs take many different forms 

depending on specific objectives and available resources. Careful planning of 

a monitoring strategy is important to enable scientifically effective and reliable data collection and analysis for the intended purposes. The Forest Service 

planning rule provides detailed guidance for Forest Plan monitoring (36 CFR 

219.12) including both a broad and local-scale approach. This plan also includes 

the option for jointly developed (i.e., more than one forest) plans that will effectively address broader-scale needs. 

• Regularly assess new scientific findings and adjust plans accordingly. 

Disclaimer: As stated above, the preceding elements are provided for the consideration of managers in conducting landscape evaluations to achieve sustainable 

land management objectives. These specific elements are not meant to suggest strict 

requirements; rather they are examples of the kinds of considerations that enable 

managers to obtain the best available scientific information for project planning. 
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Appendix 2—Regional-Scale Fire Regimes Group 

Classification for Oregon and Washington1

Most Moist Mixed-Conifer (MMC) Fire Regimes Fall Within 

Types I and III a and b.

0 to 35 years, low severity—

Typical climax plant communities include ponderosa pine, eastside/dry Douglas-fir, 

pine-oak woodlands, Jeffrey pine on serpentine soils, oak woodlands, and very dry 

white fir. Large stand-replacing fire can occur under certain weather conditions, but 

are rare events (i.e., every 200+ years).

0 to 35 years, mixed and high severity—

Includes true grasslands (Columbia basin, Palouse, etc.) and savannahs with typical 

return intervals of less than 10 years; mesic sagebrush communities with typical 

return intervals of 25 to 35 years and occasionally up to 50 years, and mountain 

shrub communities (bitterbrush, snowberry, ninebark, ceanothus, Oregon chaparral, etc.) with typical return intervals of 10 to 25 years. Certain specific communities include mountain big sagebrush and low sagebrush-fescue communities. 

Grasslands and mountain shrub communities are not completely killed, but usually 

only top-killed and resprout.

35 to 100+ years, mixed severity—

This regime usually results in heterogeneous landscapes. Large, high-severity fires 

may occur but are usually rare events. Such high-severity fires may “reset” large 

areas (10,000 to 100,000 ac [4050 to 40 500 ha]) but subsequent mixed-severity fires 

are important for creating landscape heterogeneity. Within these landscapes a mix 

of stand ages and size classes are important characteristics; generally, the landscape 

is not dominated by one or two age classes. In southeastern Oregon, this regime 

also includes aspen, riparian communities, most meadows, and wetlands.

<50 years, mixed severity—

Typical potential plant communities include mixed conifer, very dry westside 

Douglas-fir, and dry grand fir. Lower severity fire tends to predominate in many 

events.

1 Evers, L. 2002. Fire regimes of Oregon and Washington. Unpublished report. Portland, 

OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 3 p.
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50 to 100 years, mixed severity—

Typical climax plant communities include well drained western hemlock; warm, 

mesic grand fir, particularly east of the Cascade crest; and eastside western redcedar. The relative amounts of lower and higher severity patches within a given event 

are intermediate between IIIa and IIIc.

100 to 200 years, mixed severity—

Typical potential plant communities include western hemlock, Pacific silver fir, and 

whitebark pine at or below 45° N latitude and cool, mesic grand fir and Douglas-fir. 

Higher-severity fire tends to dominate in many events.

35 to 100+ years, high severity—

Seral forest communities that arise from or are maintained by high-severity fires, 

such as lodgepole pine, aspen, western larch, and western white pine, often are 

important components in this fire regime. Dry sagebrush and mountain mahogany 

communities also fall within this fire regime. Natural ignitions within this regime 

that result in large fires may be relatively rare, particularly in the Cascades north of 

45° N latitude.

35 to 100+ years, high severity, juxtaposed—

Typified by what would normally be considered a long-interval regime that lies 

immediately above a shorter interval or lower severity fire regime. Most often the 

fire originates lower on the slope and burns uphill into regime IVa. In southeastern 

Oregon, this subregime includes Wyoming big sagebrush communities on deeper 

soils below 5,000 ft elevation. Forest examples include lodgepole pine immediately 

above ponderosa pine in the eastside Washington Cascades and aspen imbedded 

within dry grand fir in the Blue Mountains. This regime is often found in lower 

elevations or drier sites than is considered typical for regime IV.

100+ years, high severity, patchy arrangement—

Typical potential forest communities include subalpine fir and mountain hemlock 

parkland and whitebark pine north of 45° N latitude.

Other community types include mixed Wyoming big sagebrush and low 

sagebrush on low productivity sites such as scablands, stiff sagebrush, and true old 

growth juniper savannah (<10 percent canopy closure). Some forbs are present, such 

as Sandberg’s bluegrass, and the availability of many of these areas for burning 

depends on wet years that result in much greater grass production than is typical. 

Typical fire return interval in these communities is 100 to 150 years.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

100 to 200 years, high severity—

Typical forest plant communities include subalpine mixed conifer (spruce-fir), 

western larch, and western white pine. Important potential forest plant communities include mountain hemlock in the Cascades and Pacific silver fir north of 45° N 

latitude.

Other plant communities include the intergrade between Wyoming big sagebrush and greasewood, shadscale on non-alkali soils, spiny hopsage, and alpine 

grasslands and heath in southeastern Oregon.

> 200 years, high severity—

This fire regime occurs at the environmental extremes where natural ignitions are 

very rare or virtually nonexistent, or environmental conditions rarely result in large 

fires. Sites tend to be very cold, very hot, very wet, very dry, or some combination 

of these conditions.

Typical plant communities include black sagebrush, salt desert scrub, greasewood on dunes, true old-growth juniper with at least 10 percent canopy closure and 

mountain-mahogany in rocky areas, and alpine communities and subalpine heath in 

the Blue Mountains and Cascades. Most species tend to be small and low-growing. 

Bare ground is common.

200 to 400 years, high severity—

Forest plant communities are at least somewhat fire-adapted. Typical plant communities include Douglas-fir, noble fir, and mountain hemlock on drier sites in parts of 

western Washington.

400+ years, high severity—

Forest plant communities are weakly fire-adapted or not fire-adapted. Typical 

plant communities include Douglas-fir, Pacific silver fir, western hemlock, western 

redcedar, and mountain hemlock on moister sites in western Washington.

No fire—

This regime includes forest plant communities with no evidence of fire for 500 

years or more. Stands often have extremely deep duff layers on poorly developed 

soils. Typical plant communities include Sitka spruce and Pacific silver fir along the 

Oregon and Washington coast and very wet western redcedar sites.
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Appendix 3—Reconstructed Historical Vegetation 

Conditions Within Sampled Areas of the Blue 

Mountains Province

This appendix is provided to highlight vegetation conditions that existed early in 

the 20th century in the Blue Mountains. The data are sorted by potential vegetation 

type (PVT); this sorting gives the reader the capacity to contrast overstory and 

understory size class, canopy cover, cover type, and structural class conditions for 

the major potential vegetation types. These insights are a companion to the body of 

this synthesis and are meant to amplify our observations about disturbance regimes 

and the sorts of patterns resulting from them. The data are adapted from Hessburg 

et al. (1999b, 2000a) and are available upon request. We provide these data to 

help the reader develop a mental picture of how the Blue Mountains landscape 

looked and likely functioned before forest management was in full swing (fig. 48). 

The vegetation conditions do not reflect a pristine condition and instead reflect 

some influence of early livestock grazing, timber harvest, and wildfire exclusion. 

Nonetheless, they are the best data we have and are based on the earliest available 

black-and-white, stereo-aerial photography, which was usually taken in anticipation 

of major future harvest activities. We found the earliest aerial photography to be an 

extensive reconnaissance of mostly nonharvested forest reserves. From characterizations like these, it is possible to visualize the primary directions and magnitudes 

of changes that occurred to the present day as a consequence of the first century of 

forest management.

Key to abbreviations in the tables that follow:

Potential vegetation types (PVT):

PIPO = ponderosa pine

WD PSME/ABGR = warm/dry—Douglas-fir/grand fir

CM PSME/ABGR = cool/moist—Douglas-fir/grand fir

WD ABLA2/PIEN = warm/dry—subalpine fir/Engelmann spruce

CM ALBA2/PIEN = cool/moist—subalpine fir/Engelmann spruce

Cover types:

PIPO = ponderosa pine

PSME = interior Douglas-fir

LAOC = western larch

ABGR = grand fir or white fir

Other = forest cover types not in PIPO, PSME, LAOC, or ABGR

NF = herbland, shrubland, and nonforest/nonrange types
239

The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Figure 48—Subwatersheds sampled in the Blue Mountains ecological reporting unit during Interior Columbia Basin 

Ecosystem Management Project (ICBEMP) (Hann et al. 1997; Hessburg et al. 1999a, 2000c). The black outline delimits 

the sampled Blue Mountains area; the white lines delineate the reconstructed subwatersheds.
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GENERAL TECHNICAL REPORT PNW-GTR-897

Structure class:

si = stand initiation

seoc = stem exclusion, open canopy

secc = stem exclusion, closed canopy

ur = understory reinitiation

yfms = young forest, multistory

ofms = old forest, multistory

ofss = old forest, single story

wood = woodland structures (all woodland structural classes combined)

herb = herbland (all herbland structural classes combined)

shrub = shrubland (all shrubland structural classes combined)

other = nonforest/nonrange and other anthropomorphic types

Tree size (overstory “OS,” understory “US,” and “Size”):

SS = seedlings and saplings (< 5.0 in diameter at breast height [d.b.h.])

PT = pole-size trees (5.1 to 8.9 in d.b.h.)

SmT = small trees (9.0 to 15.9 in d.b.h.)

MedT = medium trees (16.0 to 25.0 in d.b.h.)

LgT = large trees (>25.0 in d.b.h.)

Single story (no US) = forested patches without a visible understory

Nonforest = herbland, shrubland, and nonforest/nonrange types

Canopy cover (CC):

10–100 = percentage forest canopy cover class: 10–30, 40–60, 70–100 

Single story (no US) = forested patches without a visible understory 

 (“US_CC” tables only)

Nonforest = herbland, shrubland, and nonforest/nonrange types

Table 8 shows a total sampled area of about 415 000 ha, or more than 1 million 

ac. In the Blue Mountains, about 4 percent of that area resided in the dry PIPO 

PVT, about 10 percent in the dry mixed conifer (WD Douglas-fir/grand fir), 46 

percent in the moist mixed conifer (CM Douglas-fir/grand fir) PVT, 4 percent in 

the dry spruce-fir PVT (WD subalpine fir/Engelmann spruce), and 8 percent in the 

moist and cool to cold spruce-fir PVT (CM subalpine fir/Engelmann spruce). The 

remainder of the area (28 percent) was occupied by early-seral forest conditions 

(grass, shrub, bare ground), woodlands, and other forested PVTs.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 8—Percentage of sampled area in the Blue Mountains 

ecological reporting unit (ERU) by potential vegetation type

Potential vegetation type Area PCT_ERU

Hectares Percent

Ponderosa pine 15 624.56 3.77

Warm/dry Douglas-fir/grand fir 40 208.19 9.70

Cool/moist Douglas-fir/grand fir 191 632.00 46.22

Warm/dry subalpine fir/Engelmann spruce 16 903.80 4.08

Cool/moist subalpine fir/Engelmann spruce 33 475.22 8.07

 Total 297 843.76 71.83

Table 9 examines the distribution of overstory tree size classes (OS) combined 

with canopy cover class (CC) for each of the five major PVTs. The canopy cover 

classes are 0 (nonforest), 10 to 30 percent, 40 to 60 percent, and 70 to 100 percent. 

Canopy cover was originally interpreted in decile classes but reclassified here for 

simplicity. The size classes are given in the key that precedes these tables. Note the 

amount of each PVT that was occupied by early-seral nonforest conditions. One 

quarter of the area in the PIPO PVT was not forested, but in grass, shrub, or bare 

ground condition at any one time. This was also true of about 10 to 20 percent of 

the area of the other PVTs. Also observe that there was a relatively small area in SS 

in any CC class in the PIPO PVT, but this area increased among the other PVTs. 

When considered along with the nonforest area by PVT, this gives some insight 

into the amount of stand-replacing disturbance (in grass, shrub, or forested patches 

that was going on at any time. Note also that regardless of PVT setting, most of the 

area in any OS size class falls within the lower canopy cover classes. Note as well 

that the area with MedT or LgT in the overstory consistently ranges from 40 to 60 

percent of the PVT area (PIPO = 42.7 percent, WD PSME/ABGR = 55.6 percent, 

CM PSME/ABGR = 59.75 percent, WD ABLA2/PIEN = 38.2 percent, and CM 

ABLA2/PIEN = 44.42 percent), and most of that area is in the lower CC classes. 

Finally, note that each PVT shows a considerable area in PT and SmT trees (PIPO 

= 31.5 percent, WD PSME/ABGR = 36.1 percent, CM PSME/ABGR = 31.1 percent, 

WD ABLA2/PIEN = 37.1 percent, and CM ABLA2/PIEN = 46.3 percent), suggesting that mixed- and high-severity fire occurrence has to be a part of the fire history 

story.
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GENERAL TECHNICAL REPORT PNW-GTR-897

Table 10 examines the distribution of understory tree size classes (US) 

combined with canopy cover class (CC) for each of the five major PVTs. It is a 

companion to the previous table and provides insights about the understories of the 

forested PVTs, when that is the focal point. The canopy cover classes are 0 (nonforest), 10 to 30 percent, 40 to 60 percent, and 70 to 90 percent; obviously 100 percent 

US CC cannot exist for it to remain a US rather than an OS layer. Canopy cover 

was originally interpreted in decile classes but reclassified here for simplicity. The 

size classes are given in the key that precedes these tables. Note that as in table 9, 

regardless of PVT most of the area showing any US size class or CC occurs in the 

lowest 10 to 30 percent CC class (PIPO = 46.9 percent, WD PSME/ABGR = 51.9 

percent, CM PSME/ABGR = 50.6 percent, WD ABLA2/PIEN = 38.5 percent, and 

CM ABLA2/PIEN = 49.1 percent). A much smaller sized area existed in any PVT 

in the 40 to 60 or 70 to 90 percent CC classes (PIPO = 7.6 percent, WD PSME/

ABGR = 18.6 percent, CM PSME/ABGR = 24.3 percent, WD ABLA2/PIEN = 

13.6 percent, and CM ABLA2/PIEN = 17.1 percent). Note also that in all PVTs, 

16 to 29 percent of the patch area shows no evidence of US trees of any size class. 

Taken together, these results suggest that, for each of the five PVTs, most patch area 

Table 9—Percentage of the sampled area in the Blue Mountains province by historical potential vegetation 

type, overstory size class, and canopy cover class combination

Potential vegetation type

Overstory size × CC PIPO WD PSME/ABGR CM PSME/ABGR WD ABLA2/PIEN CM ABLA2/PIEN

Percent

SS_10–30 0.09 0.51 0.17 0.22

SS_40–60 0.01 0.03 0.23 0.22

SS_70–100 0.07 0.10 5.43 1.43

PT_10–30 4.07 3.46 2.15 3.38 3.47

PT_40–60 0.15 0.59 0.82 2.50 2.56

PT_70–100 0.12 0.61 1.65 1.50 3.42

SmT_10–30 25.91 24.04 13.42 12.52 15.19

SmT_40–60 0.69 5.14 7.10 10.10 13.96

SmT_70–100 0.52 2.21 5.95 7.09 7.73

MedT_10–30 35.89 32.30 29.57 12.32 11.80

MedT_40–60 3.34 9.14 14.16 10.95 12.85

MedT_70–100 0.12 1.59 3.66 3.96 6.30

LgT_10–30 3.36 4.29 8.49 6.39 3.28

LgT_40–60 6.37 3.02 3.29 8.06

LgT_70–100 1.97 0.85 1.27 2.14

Nonforest 25.75 7.69 8.85 18.85 7.59

 Total 100.00 100.00 100.00 100.00 100.00

CC = canopy cover; PIPO = ponderosa pine; WD PSME/ABGR = warm/dry Douglas-fir/grand fir; CM PSME/ABGR = cool/moist Douglas-fir/grand fir; 

WD ABLA2/PIEN = warm/dry subalpine fir/Engelmann spruce; CM ALBA2/PIEN = cool/moist subalpine fir/Engelmann spruce; SS = seedlings and 

saplings; PT = pole-size trees; SmT = small trees; MedT = medium trees; LgT = large trees.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 10—Percentage of the sampled area in the Blue Mountains ecological reporting unit (ERU) by historical 

potential vegetation type, understory size class, and canopy cover class combination

Potential vegetation type

Understory

size × CC PIPO WD PSME/ABGR CM PSME/ABGR WD ABLA2/PIEN CM ABLA2/PIEN

Percent

SS_10–30 21.69 18.49 7.25 2.32 6.76

SS_40–60 2.35 6.53 1.55 2.01 2.45

SS_70–90 1.30 0.38 0.24 1.03

PT_10–30 23.45 24.61 26.22 24.94 25.15

PT_40–60 3.96 7.61 10.14 6.84 5.89

PT_70–90 1.20 0.49 1.30 1.56 1.52

SmT_10–30 1.73 8.56 15.47 11.14 17.09

SmT_40–60 0.04 2.14 8.44 2.62 5.50

SmT_70–90 0.47 0.98 0.18 0.69

MedT_10–30 0.21 1.62 0.06 0.09

MedT_40–60 0.05 1.26 0.12 

MedT_70–90 0.20

Without any 19.83 21.85 16.34 29.10 26.24

understory

Nonforest 25.75 7.69 8.85 18.85 7.59

 Total 100.00 100.00 100.00 100.00 100.00

CC = canopy cover; PIPO = ponderosa pine; WD PSME/ABGR = warm/dry Douglas-fir/grand fir; CM PSME/ABGR = cool/moist Douglas-fir/grand fir; 

WD ABLA2/PIEN = warm/dry subalpine fir/Engelmann spruce; CM ALBA2/PIEN = cool/moist subalpine fir/Engelmann spruce; SS = seedlings and 

saplings; PT = pole-size trees; SmT = small trees; MedT = medium trees; LgT = large trees.

did not have dense understories, suggesting a strong influence of fire, perhaps in 

overlapping reburns, and from adjacent drier PVTs (e.g., those surrounding the WD 

and CM ABLA2/PIEN PVTs) that typically displayed more frequent fire return (the 

PIPO and WD and CM PSME/ABGR PVTs). 

Table 11 examines the areal distribution of cover types (CT) for each of the 

five major PVTs. For an expanded description of the cover types see Hessburg et 

al. 1999a (table 7: 48–49). Note that the PIPO cover type existed in all PVTs. It was 

dominant in the PIPO (65.5 percent), WD PSME/ABGR (79.42 percent), and CM 

PSME/ABGR (44.08 percent) PVTs, and occurred in trace amounts in the ABLA2/

PIEN types. Surprisingly, more area in the PIPO CT occurred in the WD PSME/

ABGR than in the PIPO PVT. This was driven by the large area (about 26 percent) 

in patches in a nonforest physiognomy (grass and shrub cover) in the PIPO PVT. 

Looking across all PVTs, it appears that grass and shrub vegetation patches were 

integral to the forest patchwork; many patches occurred in all forested PVT settings 

that were otherwise capable of supporting the growth of forest cover. Undoubtedly, 

some of these patches were alternative stable states that experienced relatively 
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GENERAL TECHNICAL REPORT PNW-GTR-897

Table 11—Percentage of the sampled area in the Blue Mountains ecological reporting unit (ERU) by historical 

potential vegetation type and cover type

Potential vegetation type

Cover type PIPO WD PSME/ABGR CM PSME/ABGR WD ABLA2/PIEN CM ABLA2/PIEN

Percent

PIPO 65.48 79.42 44.08 1.48 0.45

PSME 0.80 4.17 15.26 10.09 4.98

LAOC 0.52 0.96 4.93 9.59 6.57

ABGR 0.06 1.45 22.67 17.82 26.07

Other forest 7.39 6.30 4.21 42.17 54.33

cover types

Nonforest 25.75 7.69 8.85 18.85 7.59

 Total 100.00 100.00 100.00 100.00 100.00

PIPO = ponderosa pine; WD PSME/ABGR = warm/dry Douglas-fir/grand fir; CM PSME/ABGR = cool/moist Douglas-fir/grand fir; 

WD ABLA2/PIEN = warm/dry subalpine fir/Engelmann spruce; CM ALBA2/PIEN = cool/moist subalpine fir/Engelmann spruce; 

PSME = Douglas-fir; LAOC = western larch; ABGR = grand fir.

frequent fires and experienced difficulty establishing a dominant cover of trees. 

In contrast with the PIPO and WD PSME/ABGR PVTs, CT conditions in the CM 

PSME/ABGR PVT are increasingly complex, with 47 percent of the patch area 

in PSME, LAOC, ABGR, and other forest cover types. Nearly one-quarter of the 

CM PSME/ABGR PVT area was dominated by the ABGR (ABCO) CT, second 

only to the PIPO CT. A similar area in the ABGR CT occurred in the WD and CM 

ABLA2/PIEN PVTs, but the greatest difference was that the other forest CTs dominated the latter PVTs. These observations coupled with those from the preceding 

three tables suggest that several findings are plausible: (1) surface fires associated 

with low- and mixed-severity fires likely dominated the fire regime in the PIPO 

and WD PSME/ABGR PVTs; however, replacement-severity fires also occurred 

and they provided a nontrivial contribution; (2) low-, mixed- and high-severity fires 

likely occurred in the CM PSME/ABGR PVT owing to variability in fire frequency 

and topo-edaphic conditions, and surface fire effects from low- and mixed-severity 

fires were likely on par with crown fire effects from mixed- and high-severity fires; 

and (3) crown fire effects from mixed- and high-severity fires likely dominated in 

the ABLA2/PIEN PVTs. 
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 12 layers together in one location the relations existing in three of the four 

previous tables, excluding table 10. We integrate them all in table 13. From table 

11 we saw that 65.5 percent of the PIPO PVT area supported the PIPO CT, and 26 

percent of the area was nonforested. Of that 65.5 percent, 86 percent (56.3 percent 

of the PVT area) existed in two classes: the SmT and MedT_10 to 30 percent CC 

classes. Two aspects are noteworthy: canopy cover is low, in many cases less than 

full potential site occupancy and size class is dominated by small- and mediumsized, not large, and very large trees. In the photointerpretation, large trees were 

in evidence in a great many patches. To be identified as an overstory layer, LgT 

CC had to meet or exceed 10 percent of the CC, the lowest CC class. Where LgT 

cover did not meet the 10 percent CC threshold, the LgT cover was considered a 

remnant of a former patch and its CC was pooled with the dominant overstory 

size class. If, as the literature suggests, surface fires primarily thin from below but 

contribute <20 percent overstory mortality, then surface fire dominated regimes 

continuously regenerate patches affected by them, and they manifest at any point 

in time as multicohort, multi-aged, multisized patches. Put alternatively, if fires are 

occurring every 5 to 15 years in the PIPO and WD PSME/ABGR PVTs and they 

conservatively kill on average just 5 percent of the CC at each instance of fire, it is 

difficult to imagine finding many patches of PIPO CT with a high canopy cover of 

mostly LgT, and with many trees older than about 350 years of age. That is what is 

shown here. Notice the strong similarities between the PIPO and WD PSME/ABGR 

PVTs—but there are differences as well. In both PVTS one can see the powerful 

influence of surface fires in maintaining low canopy cover conditions; however, in 

the WD PSME/ABGR PVT, the story is less tidy; nearly 28 percent of the area is 

comprised of patches with a broader array of size classes, intermediate and higher 

canopy cover classes, and a broader range of cover types. It is apparent that fire 

frequency and fire severity are more variable in the WD PSME/ABGR than the 

PIPO PVT. This pattern continues into the CM PSME/ABGR PVT, where there is 

greater evidence of CT, size, CC, and hence fire regime variability.
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GENERAL TECHNICAL REPORT PNW-GTR-897

Table 12—Percentage of the sampled area in the Blue Mountains ecological reporting unit (ERU) by historical 

potential vegetation type, cover type, size class, and canopy cover class

Potential vegetation type

Cover type PIPO WD PSME/ABGR CM PSME/ABGR WD ABLA2/PIEN CM ABLA2/PIEN

Percent

PIPO:

SS_10––30 0.46 0.16

SS_40–60 0.01

SS_70–100 0.04 0.02

PT_10–30 2.05 1.56 1.24 0.53

PT_40–60 0.06 0.42 0.34

PT_70–100 0.12 0.51 0.14 0.09

SmT_10–30 23.71 20.66 8.60 0.17 0.26

SmT_40–60 0.29 3.47 3.00 0.18 0.02

SmT_70–100 1.69 1.25

MedT_10–30 32.56 28.75 17.93 0.51 0.08

MedT_40–60 3.26 8.22 6.56

MedT_70–100 0.12 1.44 0.35

LgT_10–30 3.31 3.91 3.73 0.09

LgT_40–60 6.32 0.66

LgT_70–100 1.94 0.09

PSME:

SS_10–30 0.01 0.12

SS_40–60 0.02 0.23

SS_70–100 0.04

PT_10–30 0.16 0.46 0.32 0.06

PT_40–60 0.09 0.07 0.12 0.63

PT_70–100 0.10 0.06

SmT_10–30 0.32 0.90 1.55 1.65 0.36

SmT_40–60 0.04 0.72 1.48 1.55 1.21

SmT_70–100 0.11 1.14 1.24 0.25

MedT_10–30 0.06 1.06 4.74 1.94 2.06

MedT_40–60 0.07 0.62 1.82 1.38 0.52

MedT_70–100 0.15 0.66 0.25 0.04

LgT_10–30 0.05 0.04 2.69 0.96 0.41

LgT_40–60 0.05 0.51 0.16

LgT_70–100 0.06

LAOC:

SS_10–30

SS_40–60 0.01 0.07

SS_70–100 0.02 0.01 3.31 0.28

PT_10–30 0.03 0.11 0.12

PT_40–60 0.03 0.16 0.19

PT_70–100 0.04 0.27 0.26 0.16

SmT_10–30 0.16 0.55 1.38 1.41

SmT_40–60 0.11 0.24 0.11 1.29

SmT_70–100 0.52 0.08 0.47 0.11 0.36

MedT_10–30 0.47 1.72 0.86 1.54

MedT_40–60 0.01 0.59 2.70 0.59

MedT_70–100 0.24 0.05 0.10
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 12—Percentage of the sampled area in the Blue Mountains ecological reporting unit (ERU) by historical 

potential vegetation type, cover type, size class, and canopy cover class (continued)

Potential vegetation type

Cover PIPO WD PSME/ABGR CM PSME/ABGR WD ABLA2/PIEN CM ABLA2/PIEN

Percent

LgT_10–30 0.20 0.80 0.46

LgT_40–60 0.36

LgT_70–100

ABGR:

SS_10–30

SS_40–60

SS_70–100 0.08

PT_10–30 0.28 0.25 0.36

PT_40–60 0.02 0.14 0.69

PT_70–100 0.24 0.36 0.07

SmT_10–30 0.03 0.01 2.26 1.77 2.04

SmT_40–60 0.67 2.25 3.03 4.70

SmT_70–100 0.14 2.54 1.51 2.84

MedT_10–30 0.03 0.17 3.82 2.30 2.40

MedT_40–60 0.23 5.12 2.48 4.16

MedT_70–100 2.40 2.02 3.21

LgT_10–30 0.20 1.58 1.27 0.27

LgT_40–60 1.48 2.24 3.93

LgT_70–100 0.03 0.68 0.45 1.35

Other forest cover types:

SS_10–30 0.09 0.05 0.10

SS_40–60 0.15

SS_70–100 0.03 2.11 1.07

PT_10–30 1.86 1.42 0.21 2.61 2.93

PT_40–60 0.07 0.18 1.72 1.67

PT_70–100 0.06 0.90 0.87 3.05

SmT_10–30 1.85 2.31 0.46 7.56 11.12

SmT_40–60 0.36 0.16 0.12 5.23 6.74

SmT_70–100 0.18 0.55 4.23 4.28

MedT_10–30 3.23 1.86 1.36 6.72 5.72

MedT_40–60 0.06 0.07 4.40 7.58

MedT_70–100 0.01 1.65 2.95

LgT_10–30 0.13 0.28 3.27 2.15

LgT_40–60 0.89 4.14

LgT_70–100 0.02 0.82 0.79

Nonforest 25.75 7.69 8.85 18.85 7.59

 Grand total 100.00 100.00 100.00 100.00 100.00

CC = canopy cover; PIPO = ponderosa pine; WD PSME/ABGR = warm/dry Douglas-fir/grand fir; CM PSME/ABGR = cool/moist Douglas-fir/

grand fir; WD ABLA2/PIEN = warm/dry subalpine fir/Engelmann spruce; CM ALBA2/PIEN = cool/moist subalpine fir/Engelmann spruce; 

PSME = Douglas-fir; LAOC = western larch; ABGR = grand fir; SS = seedlings and saplings; PT = pole-size trees; SmT = small trees; 

MedT = medium trees; LgT = large trees.
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GENERAL TECHNICAL REPORT PNW-GTR-897

In table 13, we layer the information from all five of the preceding tables 

together using structural classes of O’Hara et al. (1996). Structural classes are 

used because they provide a sense of the relative abundance of components of each 

PVT landscape resulting from the combined influences of forest succession, stand 

dynamics, and disturbance processes. The structural classes take the continuum of 

conditions and bin them into key mileposts in succession and disturbance regimes. 

Toggling between tables 12 and 13 is useful for visualizing this point. In the PIPO 

PVT, we see that stem exclusion open canopy structures (seoc, 31.4 percent) dominated, occupying nearly one half of all PIPO cover (31.4/65.5). This was followed by 

stand initiation structure (si, 21.2 percent), grass and herb patches (herbland, 15.62 

percent), shrubland patches (9.8 percent) woodland patches where tree cover (PIPO 

and JUOC, western juniper) was <30 percent CC (woodland), followed by young 

multistory forest (yfms), and understory reinitiation (ur, 3.32 percent) structures. It 

is plausible that PIPO_si cover occurred in patches after severe fires or that PIPO 

forest was reinvading a much larger area of grass, shrub, and woodland patches 

under the influence of livestock grazing, fire suppression, and fire exclusion. At the 

time of the photointerpretation, only 2.5 percent of the total area showed any evidence of prior timber harvest, and most of this was light selection cutting. Conditions were similar to the PIPO PVT in the WD PSME/ABGR PVT; however, more 

closed canopy conditions are present and structural conditions are spread across a 

broader range of CTs. From table 11, we note that nearly 80 percent of the area in 

the WD PSME/ABGR PVT displayed the PIPO CT. This was distributed across all 

structural classes, but not evenly so; 59 percent was comprised on PIPO_si, PIPO_

seoc, and PIPO_yfms conditions, PIPO_ur contributed another 9 percent, and old 

single and multistory forests contributed another 10 percent. At the time of the 

photointerpretation, one third of the WD PSME/ABGR PVT area had experienced 

some noticeable selection cutting. We notice a much broader distribution of CT and 

structural class combinations when we observe the CM PSME/ABGR PVT. Here, 

33 and 23 percent of the area is comprised of yfms and seoc structures, respectively, 

across all cover types. At the time of the photointerpretation, 15 percent of this PVT 

area had experienced light selection cutting, and there was little evidence of regeneration harvesting. In both the WD and CM ABLA2/PIEN PVTs, there was trace 

evidence of selection and regeneration harvests. In most cases, regardless of PVT, 

the selection cutting dominated the observed logging in the early photos, it was 

obvious and recent, and the largest and oldest remnant large and very large trees 

were the target of opportunity.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Table 13—Percentage of the sampled area in the Blue Mountains ecological reporting unit (ERU) by historical 

potential vegetation type, cover type, and structural class

Potential vegetation type

Cover × structure PIPO WD PSME/ABGR CM PSME/ABGR WD ABLA2/PIEN CM ABLA2/PIEN

Percent

PIPO:

si 21.23 16.59 3.06 0.06

seoc 31.35 27.60 11.95 0.78 0.14

secc 0.04 2.48 1.56 0.18 0.23

ur 3.32 8.72 7.70 0.19 0.08

yfms 9.44 14.51 17.64 0.27

ofms 0.11 5.60 1.40

ofss 3.91 0.78

PSME:

si 0.49 0.68 1.11 0.11

seoc 0.29 2.09 2.63 2.72 1.32

secc 0.15 1.81 1.98 0.55

ur 0.44 0.54 3.19 1.68 1.57

yfms 0.07 0.85 6.15 2.32 1.44

ofms 0.03 0.28 0.27

ofss 0.02 0.53

LAOC:

si 0.02 0.45 3.85 1.07

seoc 0.13 0.14 0.11 0.27

secc 0.52 0.13 0.93 1.59 1.51

ur 0.53 1.54 2.94 2.67

yfms 0.15 1.40 0.41 1.05

ofms 0.46 0.68

ofss 0.01

ABGR:

si 0.11 0.23

seoc 0.06 0.18 7.20 4.22 4.07

secc 0.50 2.65 3.15 4.74

ur 0.31 3.98 3.82 5.78

yfms 0.23 6.11 3.58 5.89

ofms 0.20 0.59 0.56 1.28

ofss 0.03 2.03 2.48 4.08

Other forest cover types:

si 0.39 0.77 0.13 3.12 4.00

seoc 0.11 0.71 16.18 15.61

secc 0.25 1.14 8.23 7.97

ur 0.49 0.80 6.79 9.77

yfms 0.71 1.28 5.64 10.63

ofms 0.42 2.09

ofss 0.02 1.77 4.27

Woodland 7.00 3.99 0.14 0.01

Nonforest

Herbland 15.62 3.27 7.45 13.74 4.56

Shrubland 9.80 4.16 0.79 1.39 1.15

Nonforest/nonrange 0.34 0.27 0.61 3.73 1.89

 Total 100.00 100.00 100.00 100.00 100.00

PIPO = ponderosa pine; WD PSME/ABGR = warm/dry Douglas-fir/grand fir; CM PSME/ABGR = cool/moist Douglas-fir/grand fir; WD ABLA2/PIEN 

= warm/dry subalpine fir/Engelmann spruce; CM ALBA2/PIEN = cool/moist subalpine fir/Engelmann spruce; PSME = Douglas-fir; LAOC = western 

larch; ABGR = grand fir; si = stand initiation; seoc = stem exclusion, open canopy; secc = stem exclusion, closed canopy; ur = understory reinitiation; 

yfms = young forest, multistory; ofms = old forest, multistory; ofss = old forest, single story.
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GENERAL TECHNICAL REPORT PNW-GTR-897

Glossary

Adaptive management—A system of management practices based on clearly 

identified outcomes and monitoring to determine if management actions are meeting desired outcomes, and if not, to facilitate management changes that will best 

ensure that outcomes are met or reevaluated. Adaptive management stems from the 

recognition that knowledge about natural resource systems is sometimes uncertain 

(36 CFR 219.16; FSM 1905).

Composition—The biological elements within the different levels of biological 

organizations, from genes and species to communities and ecosystems (FSM 2020).

Connectivity (or habitat connectivity)—The degree to which intervening landscape characteristics impede or facilitate the movement of organisms or ecological 

processes between patches. The concept of connectivity implies that some feature 

or patch in the landscape is spatially related to other, similar features, and that 

intervening landscape characteristics influence the ecological relationship between 

those features. Although somewhat counterintuitively, it is important to note that 

a landscape can be highly fragmented or patchy, as is commonly the case in landscapes with mixed-severity fire regimes, and still be highly connected for a variety 

of ecological processes.

Disturbance—A force that causes significant change to the structure, composition, 

or function of an ecosystem through natural events such as earthquake, fire, flood, 

insect and disease outbreaks, weather, or wind; or by human activities such as the 

harvest of forest products. Many or most disturbances of interest are integral parts 

of and important to ecosystem function and health. 

Ecophysiological—Relating to the interrelationships between an organism’s 

function and its physical environment.

Ecosystem services—Benefits people obtain from ecosystems (FSM 2020), 

including:

1. Provisioning services such as clean air and fresh water, as well as 

energy, fuel, forage, fiber, and minerals;

2. Regulating services such as long-term storage of carbon; climate regulation; water filtration, purification, and storage; soil stabilization; flood 

control; and disease regulation;

3. Supporting services such as pollination, seed dispersal, soil formation, 

and nutrient cycling; 

4. Cultural services such as educational, aesthetic, spiritual and cultural 

heritage values, as well as recreational experiences and tourism opportunities.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Elasticity—The speed with which a system returns after disturbance.

ENSO—El Niño/Southern Oscillation, a band of anomalously warm ocean water 

temperatures that occasionally develops off the western coast of South America and 

can cause climatic changes across the Pacific Ocean. The extremes of this climate 

pattern’s oscillations cause extreme weather (such as floods and droughts) in many 

regions of the world.

Epicormic—Literally, “of a shoot or branch,” this term implies growing from a 

previously dormant bud on the trunk or a limb of a tree. 

Fire intensity—The amount of energy or heat release during fire.

Fire regime—The characteristics of fire in a given ecosystem, such as the 

frequency, severity, extent, and seasonality of fire.

Fire severity—The scale at which vegetation and a site are altered or disrupted by 

fire, from low to high severity. It is a combination of the degree of fire effects on 

vegetation (amount of fire caused vegetation mortality) and on soil properties.

Fragmentation—A term that has various meanings depending on the context of 

its use. Here we define it in two related ways (also see “connectivity”):

Landscape fragmentation—The breaking up of continuous habitats into 

patches, thereby generating habitat loss, isolation, and edge effects.

Wildlife habitat fragmentation—The set of mechanisms leading to the 

discontinuity in the spatial distribution of resources and conditions present in 

an area at a given scale that affects occupancy, reproduction, and survival in a 

particular species.

Frequency distribution—A depiction, often appearing in the form of a curve or 

graph, of the frequency with which possible values of a variable have occurred. In 

this report, we speak of the frequency of wildfire patches of various sizes.

Function—Ecological processes, such as energy flow; nutrient cycling and 

retention; soil development and retention; predation and herbivory; and natural 

disturbances such as wind, fire, and floods that sustain composition and structure 

(FSM 2020).

Future range of variation (FRV)—The natural fluctuation of pattern components 

of healthy ecosystems that may occur in the future, primarily affected by climate 

change, human infrastructure, and invasive species.

Heterogeneity—Any factor that induces variation in individual demographic rates.
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Hierarchy theory—Ecological hierarchy theory presupposes that nature is working at multiple scales and has different levels of organization which are part of a 

rate-structured, nested hierarchy. 

Historical range of variation (HRV)—The natural fluctuation in pattern of 

components of ecosystems over time.

Inertia—The resistance of a system to disturbance.

Integrity—An ecosystem has integrity if it retains its complexity, intact biotic and 

abiotic processes, capacity for self-organization, and sufficient diversity, within its 

structures and functions, to maintain the ecosystem’s self-organizing complexity 

through time.

Interdigitate—The interlocking of (in this case) different components of the 

landscape like the fingers of two clasped hands. This creates an intertwining or 

intermingling mosaic of different vegetation or habitat conditions.

Landscape—A large land area composed of interacting ecosystems that are 

repeated in terms of factors such as geology, soils, climate, and human impacts. 

Landscapes are often used for coarse grain analysis.

Landscape hierarchy—Landscapes are systems that can be divided or decomposed into a hierarchy of nested geographic (i.e., different sized) units. This organization provides a guide for defining the functional components of a system and 

defines ways components at different scales are related to one another. 

One common way this is conceptualized is the following organization: 

region = millions of hectares; landscapes = tens of thousands of hectares; 

watersheds = hundreds to thousands of hectares; stands (patches) = one to 

tens of hectares; gaps = 0.01 to 0.1 ha.

Mosaic—The contiguous spatial arrangement of elements within an area. For 

regions this is typically the upland vegetation patches, large urban areas, large bodies of water, and large areas of barren ground or rock. However, regional mosaics 

can also be land ownership, habitat patches, land use patches, or other elements. For 

landscapes, this is typically the spatial arrangement.

Multi-aged stands—Stands having two or more age classes and including stands 

resulting from variable-retention systems or other traditionally even-aged systems 

that leave residual or reserve trees.

Nested hierarchy—The name given to the hierarchical structure of groups within 

groups or branches from a trunk used to classify organisms.
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The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington

Orographic—The lift of an air mass when it is forced from a low elevation to a 

higher elevation as it is moves over rising terrain. As the air mass gains altitude, it 

cools, its relative humidity increases, and clouds and sometimes precipitation result.

Patch—An area of similar vegetation, in structure and composition. Patches may 

range in size from a portion of a hectare to thousands of hectares.

PDO—The Pacific Decadal Oscillation is often described as a long-lived El 

Niño-like pattern of Pacific climate variability. As seen with the better-known 

El Niño/Southern Oscillation (ENSO), extremes in the PDO pattern are marked 

by widespread variations in Pacific Basin and North American climate. 

Plant association—Plant associations are a finer level of classification in the 

potential vegetation hierarchy. They are defined in terms of a climax dominant 

overstory tree species and an understory herb or shrub species that is typical of the 

environmental conditions of a distinctive community of plants. 

Plant association group (PAG)—A group of potential vegetation types that have 

similar environmental conditions and are dominated by similar types of plants (e.g., 

the dry shrub PVG). They are often grouped by similar types of life forms.

Potential vegetation type (PVT)—A potential vegetation type is a kind of physical and biological environment that produces a kind of vegetation, such as the dry 

Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) type. Potential vegetation types 

are identified by indicator species of similar environmental conditions. For example, 

Douglas-fir indicates a cooler and moister environment than ponderosa pine (Pinus 

ponderosa Lawson & C. Lawson). Because of growth, mortality, and disturbance 

of the vegetation, many other kinds of vegetation will occur on this type through 

time. In many cases the indicator species will not be present, due to disturbance. 

Douglas-fir is simply an indicator, and name, for the kind of physical and biological 

environment stratification that is used for prediction of response.

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 (FSM Chapter 2020). Resilience can be further defined to 

mean the amount of disturbance that an ecosystem can withstand without changing functional states. In this context, while dominant floristics may vary, a forest 

remains a forest as exemplified by maintenance of certain characteristic biological 

composition and the ecological goods and services it produces. Resiliency is the 

inherent capacity of a landscape or ecosystem to maintain its basic structure, function, and organization in the face of disturbances, both common and rare.
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Restoration—The Forest Service defines restoration (National Forest System Land 

Management Planning, 36 CFR 219.19) as the process of assisting the recovery of 

an ecosystem that has been degraded, damaged, or destroyed. Ecological restoration focuses on reestablishing the composition, structure, pattern, and ecological 

processes necessary to facilitate terrestrial and aquatic ecosystem sustainability, 

resilience, and health under current and future conditions.

Stand—A descriptor of a land management unit consisting of a contiguous group 

of trees sufficiently uniform in age-class distribution, composition and structure, 

and growing on a site of sufficiently uniform quality, to be a distinguishable unit.

Structure—The organization and physical arrangement of biological elements such 

as snags and down woody debris, vertical and horizontal distribution of vegetation, 

stream habitat complexity, landscape pattern, and connectivity (FSM 2020).

Sustainability—Meeting needs of the present generation without compromising 

the ability of future generations to meet their needs. Sustainability is composed 

of desirable social, economic, and ecological conditions or trends interacting at 

varying spatial and temporal scales, embodying the principles of multiple use and 

sustained yield (FSM 1905). Conditions that support native species, ecosystem 

services, and ecological processes are sustainable when influences on them have 

not resulted in significant depletion or permanent damage. 

Topo-edaphic—Related to or caused by particular soil conditions, as of texture or 

drainage, rather than by physiographic or climatic factors within a defined region or 

area.

Variable density thinning—The method of thinning some sub-stand units to a 

different density than other sub-stand units.

Vegetation series (plant community)—An assembly of different species of plants 

growing together in a particular habitat; the floral component of an ecosystem. 

According to Powell et. al. (2007 page 12), a series is the highest level of a potential 

vegetation hierarchy and is defined by the dominant climax plant species. 

Vegetation type—A plant community with distinguishable characteristics.
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