UNITED STATES

DEPARTMENT OF

AGRICULTURE

FOREST SERVICE

PACIFIC NORTHWEST

REGION

APRIL 2011

CLIMATE CHANGE AND FOREST 

BIODIVERSITY:

A VULNERABILITY ASSESSMENT AND 

ACTION PLAN FOR NATIONAL FORESTS IN 

WESTERN WASHINGTON
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PESTICIDE PRECAUTIONARY STATEMENT 

This publication reports research involving pesticides. It does not contain recommendations for their use, 

nor does it imply that the uses discussed here have been registered. All uses of pesticides must be 

registered by appropriate State or Federal agencies, or both, before they can be recommended. 

CAUTION: Pesticides can be injurious to humans, domestic animals, desirable plants, and fish or other wildlife—if they 

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disposal of surplus pesticides and pesticide containers.

COVER PHOTO

Subalpine habitat, Norse Peak Wilderness, Mt. Baker-Snoqualmie National Forest, Robin Shoal, U.S. Forest Service.
CLIMATE CHANGE AND FOREST 

BIODIVERSITY:

A VULNERABILITY ASSESSMENT AND ACTION PLAN FOR 

NATIONAL FORESTS IN WESTERN WASHINGTON

APRIL 2011

Prepared by:

Carol Aubry, Warren Devine, Robin Shoal, Andrew Bower, Jeanne Miller, 

and Nicole Maggiulli

Authors

Carol Aubry is a geneticist, Robin Shoal is an ecologist, and Andrew Bower is a geneticist, U.S. 

Department of Agriculture, Forest Service, Olympic National Forest, 1835 Black Lake Blvd. SW, 

Suite A, Olympia, WA 98512. Warren Devine is a natural resources specialist, Jeanne Miller is a 

GIS specialist, and Nicole Maggiulli is a natural resources specialist, 1835 Black Lake Blvd. SW, 

Suite A, Olympia, WA 98512.

Climate Change and Forest Biodiversity in Western Washington i

TABLE OF CONTENTS

Executive Summary ......................................................................................................1

Introduction................................................................................................................................2

Our Goal .....................................................................................................................................2

Objectives ...................................................................................................................................2

Forests of Western Washington................................................................................................2

Forest Tree Species....................................................................................................................3

Forest Tree Vulnerability Assessment.....................................................................................4

Methods...............................................................................................................................................4

Group 1 Tree Species...........................................................................................................................5

Group 2 and Group 3 Tree Species......................................................................................................5

Non-Forested Habitats ..............................................................................................................6

Recommendations......................................................................................................................7

Top 10 Action Items...................................................................................................................8

Forest Trees .........................................................................................................................................8

Non-Forested Habitats.........................................................................................................................8

Introduction....................................................................................................................9

Assessing Climate Change Effects on Pacific Northwest Vegetation..................................10

Area of Study............................................................................................................................12

Goals, Assessment Targets, and Objectives...........................................................................17

Forest Tree Species............................................................................................................................17

Selected Vulnerable Non-Forested Habitats: Alpine and Subalpine Habitats, Dry Grasslands, 

and Wetlands ................................................................................................................................17

Objectives..........................................................................................................................................17

Part 1: Forest Tree Species ........................................................................................18

Tree Species of Western Washington.....................................................................................19

Introduction .......................................................................................................................................19

Grouping............................................................................................................................................19

Habitats..............................................................................................................................................19

Distribution........................................................................................................................................19

Distribution Maps.........................................................................................................................24

Interpreting Maps..........................................................................................................................24

Tree Species Profiles.........................................................................................................................25

Vulnerability Assessment of Western Washington Tree Species........................................26

Introduction .......................................................................................................................................26

Climate Change Vulnerability Assessment Systems.........................................................................26

Selecting a Vulnerability Assessment System..............................................................................26

The Forest Tree Genetic Risk Assessment System.......................................................................27

Results of Applying the Forest Tree Genetic Risk Assessment System to Group 1 Tree Species....29

Distribution...................................................................................................................................29

Reproductive Capacity..................................................................................................................34

Habitat Affinity.............................................................................................................................35

Adaptive Genetic Variation ..........................................................................................................38

Insects and Diseases .....................................................................................................................39

Ranking Based on Overall Score..................................................................................................42

Conclusions...................................................................................................................................44

Vulnerability of Group 2 and 3 Species.............................................................................................45

Group 2 Species............................................................................................................................46
ii Climate Change and Forest Biodiversity in Western Washington

Group 3 Species............................................................................................................................48

Tools and Management Options.............................................................................................50

Introduction .......................................................................................................................................50

Monitoring Climate Change Effects on Forest Trees........................................................................50

The Role of Monitoring................................................................................................................50

Climate Effects on Tree Phenology and Growth ..........................................................................50

Climate Effects on Seed and Pollen Vectors................................................................................51

Genetic Variation and Population Structure .................................................................................51

Resources for Monitoring Climate Change Effects on Trees.......................................................54

Summary.......................................................................................................................................57

Vegetation Management Options......................................................................................................58

Introduction...................................................................................................................................58

Disturbance...................................................................................................................................58

Assisted Migration and Projecting Future Changes in Tree Distribution.....................................59

New Management Opportunities..................................................................................................62

Gene Conservation.............................................................................................................................63

Introduction...................................................................................................................................63

Ex Situ Genetic Resources............................................................................................................63

Seed Orchards..........................................................................................................................63

Seed Storage ............................................................................................................................63

In Situ Genetic Resources.............................................................................................................65

White Pine Blister Rust Resistance Screening.........................................................................65

Western white pine ..................................................................................................................66

Whitebark pine.........................................................................................................................66

Evaluation of the Seedlot Selection Tool ..........................................................................................67

Part 2: Non-Forested Habitats Vulnerable to Climate Change ................................69

Introduction..............................................................................................................................70

Alpine and Subalpine Habitats...............................................................................................71

Vulnerability......................................................................................................................................71

Ecosystem Goods and Services.........................................................................................................74

Information Gaps...............................................................................................................................74

Native Dry Grassland Habitats..............................................................................................76

Vulnerability......................................................................................................................................78

Ecosystem Goods and Services.........................................................................................................79

Information Gaps...............................................................................................................................79

Wetlands ..................................................................................................................................80

Vulnerability......................................................................................................................................82

Ecosystem Goods and Services.........................................................................................................83

Information Gaps...............................................................................................................................83

Part 3: Recommendations ..........................................................................................85

Recommendations....................................................................................................................86

Action Items..............................................................................................................................86

Top 10 Priority Action Items..................................................................................................87

Acknowledgments......................................................................................................................109

References...................................................................................................................................110

Appendix A: Tree Species Distribution Maps........................................................................ A-1

Appendix B: Tree Species Profiles...........................................................................................B-1

Appendix C: Evaluation of the NatureServe Climate Change Vulnerability Index .......... C-1
Climate Change and Forest Biodiversity in Western Washington iii

Appendix D: Evaluation of the Climate Change Sensitivity Database ................................ D-1

Appendix E: Climate Data Analysis.........................................................................................E-1

List of Figures

Figure 1. Major public lands of western Washington.............................................................................11

Figure 2. Northwest Forest Plan land allocations for Olympic National Forest.....................................14

Figure 3. Northwest Forest Plan land allocations for Mt. Baker-Snoqualmie National Forest..............15

Figure 4. Northwest Forest Plan land allocations for Gifford Pinchot National Forest .........................16

Figure 5. Potential natural vegetation zones of the Olympic Peninsula, Washington (Henderson 

2009)..................................................................................................................................................21

Figure 6. Potential natural vegetation zones of northwestern Washington (Henderson 2009) ..............22

Figure 7. Potential natural vegetation zones of southwestern Washington (Henderson 2009) ..............23

Figure 8. Relationship between overall climate change vulnerability score and mean elevation of 

FIA plots on which each of the 15 Group 1 tree species occurred in western Washington...............44

Figure 9. Projected modal vegetation types on the Olympic Peninsula for the 2010–2020 time 

period compared to modeled historical vegetation types...................................................................60

Figure 10. Projected modal vegetation types on the Olympic Peninsula for the 2040–2060 time 

period compared to modeled historical vegetation types...................................................................61

Figure 11. Alpine and subalpine parkland potential natural vegetation zones of western 

Washington (Henderson 2009)..........................................................................................................72

Figure 12. Dry grassland habitats of western Washington .....................................................................77

Figure 13. Wetlands of western Washington, as mapped by the National Wetland Inventory (U.S. 

Fish and Wildlife Service).................................................................................................................81

List of Tables

Table 1. Allocation of Northwest Forest Plan land in Washington, Oregon, and northern California...12

Table 2. Native tree species of western Washington..............................................................................20

Table 3. Explanation of data sources used to create tree species distribution maps for western 

Washington........................................................................................................................................25

Table 4. Comparison of the NatureServe Climate Change Vulnerability Index (NSVI) and the 

Climate Change Sensitivity Database (CCSD) vulnerability assessments and their suitability for 

evaluating the tree species of western Washington ...........................................................................27

Table 5. Evaluation of the Forest Tree Genetic Risk Assessment System (GRAS) developed by 

Potter and Crane (2010) ....................................................................................................................28

Table 6. Risk factor and variable descriptions and scoring system for the Forest Tree GRAS; 

higher scores indicate greater vulnerability.......................................................................................30

Table 7. Risk factor based on species’ distribution in a climate change vulnerability assessment of 

15 major western Washington tree species; higher scores indicate greater vulnerability .................32

Table 8. Risk factor based on reproductive capacity in a climate change vulnerability assessment 

of 15 major western Washington tree species; higher scores indicate greater vulnerability .............33

Table 9. Risk factor based on habitat affinity in a climate change vulnerability assessment of 15 

major western Washington tree species; higher scores indicate greater vulnerability ......................36

Table 10. Risk factor based on variables affecting adaptive genetic variation in a climate change 

vulnerability assessment of 15 major western Washington tree species; higher scores indicate 

greater vulnerability...........................................................................................................................37

Table 11. Comparison of alternative evolutionary strategies.................................................................38

Table 12. Risk factor based on major insect and disease threats in a climate change vulnerability 

assessment of 15 major western Washington tree species; higher scores indicate greater 

vulnerability.......................................................................................................................................40

Table 13. Summary of risk factor scores, and overall scores, in a climate change vulnerability 

assessment of 15 major western Washington tree species; higher scores indicate greater 

vulnerability.......................................................................................................................................43
iv Climate Change and Forest Biodiversity in Western Washington

Table 14. Shade tolerance and drought tolerance of the Group 2 tree species.......................................46

Table 15. Reproductive characteristics of the Group 2 tree species ......................................................48

Table 16. Summary of possible climate change vulnerabilities of Group 3 species ..............................49

Table 17. Forest tree pollen and seed dispersal vectors..........................................................................52

Table 18. Information available on factors influencing species’ genetic vulnerability to climate 

change................................................................................................................................................53

Table 19. Options for assessing potential climate change effects on tree species of western 

Washington........................................................................................................................................55

Table 20. Seed orchards and clone banks in Washington and Oregon...................................................56

Table 21. Ex situ genetic resources in seed orchards on the Olympic National Forest ..........................64

Table 22. Ex situ genetic resources in seed orchards on the Mt. Baker-Snoqualmie National Forest....64

Table 23. Ex situ genetic resources in seed orchards on the Gifford Pinchot National Forest...............64

Table 24. Ex situ genetic resources in seed orchards managed by the Washington Department of 

Natural Resources..............................................................................................................................65

Table 25. Ex situ genetic resources in single-tree seedlots in storage at the Dorena Genetic 

Resources Center...............................................................................................................................66

Table 26. Western white pine blister rust screening in western Washington.........................................66

Table 27. Whitebark pine blister rust screening in western Washington ...............................................67

Table 28. Top 10 priority action items...................................................................................................88

Table 29. Action items for all western Washington national forests......................................................89

Table 30. Action items for Gifford Pinchot National Forest..................................................................95

Table 31. Action items for Mt. Baker-Snoqualmie National Forest.......................................................99

Table 32. Action items for Olympic National Forest ...........................................................................103
Climate Change and Forest Biodiversity in Western Washington 1

EXECUTIVE SUMMARY
2 Climate Change and Forest Biodiversity in Western Washington

INTRODUCTION

Climate change predictions for the Pacific Northwest 

include overall warming, increased winter 

precipitation, and decreased summer precipitation, 

resulting in warmer, wetter winters and warmer, drier 

summers (Mote and Salathe 2009). The extent and 

duration of the regional snowpack is projected to 

decrease, particularly at lower elevations (Elsner et al. 

2009, Mote 2003). Seasonal stream flow patterns are 

likely to shift to earlier spring peak flows and lower 

summer flows, especially for snowmelt-dominated 

watersheds (Barnett et al. 2005). There is a limited 

amount of information on climatic tolerance for many 

tree species and even less information on what 

complex interactions could result from ecosystemwide exposure to a changing environment.

OUR GOAL

The goals of this analysis are to conduct a climate 

change vulnerability assessment of forest tree species, 

assess the vulnerability of non-forested habitats to 

climate change, and propose practical management 

actions that will work under a variety of future climate 

scenarios and can be implemented by the national 

forests in western Washington in cooperation with 

other land managers.

OBJECTIVES

The specific objectives of this analysis are to:

1. Assess the potential impacts of predicted changes 

in climate on both forest trees and selected 

vulnerable habitats: alpine and subalpine habitats, 

dry grasslands, and wetlands.

2. Evaluate tools that have been developed to assess 

vulnerability and mitigate the expected stressors of 

a warming climate.

3. Recommend actions that will improve 

understanding of changes taking place among tree 

species and non-forested habitats, maintain and 

increase biodiversity and increase resilience, and 

prepare for an uncertain future.

4. Collaborate in the implementation of these actions 

with the two other predominant public land 

management agencies in western Washington: the 

National Park Service and the Washington State 

Department of Natural Resources.

FORESTS OF WESTERN 

WASHINGTON

The forests of western Washington, defined here as the 

portion of the state west of the Cascade Range crest, 

includes the Olympic, Mt. Baker-Snoqualmie, and 

Gifford Pinchot national forests comprising 3.7 million 

ac (1.5 million ha), and the Olympic, North Cascades, 

and Mount Rainier national parks, comprising 1.8 

million ac (0.7 million ha). An additional 1.6 million 

ac (0.6 million ha) of forest land is administered by the 

Washington State Department of Natural Resources. 

Nearly 3 million acres (1.6 million ha) are protected 

either as national parks or congressional designated 

wilderness areas on nation forests.

Vegetation management on western Washington’s 

National Forests is focused on thinning forest stands 

and restoring plant communities with an emphasis on 

fish and wildlife habitat. On these three forests, either 

pre-commercial or commercial tree thinning is 

conducted on a combined total of approximately 7,000 

ac (2,800 ha) each year, most often with the objective 

of improving wildlife habitat. Tree planting is 

HOW CAN THE THREE NATIONAL FORESTS 

IN WESTERN WASHINGTON CONSERVE 

BIODIVERSITY AND INCREASE RESILIENCY 

GIVEN THE PREDICTED CHANGES IN 

TEMPERATURE AND PRECIPITATION?
Climate Change and Forest Biodiversity in Western Washington 3

infrequent; a combined total of fewer than 300 ac (120 

ha) is reforested each year.

FOREST TREE SPECIES

We organized the tree species of western Washington 

into three groups (see table on next page). Group 1 

consists of 15 overstory tree species that are common 

in major portions of western Washington and are thus 

important components of the forest canopy and overall 

forest structure. These Group 1 species are a major 

focus of this report because changes in their 

distribution or health could affect forest structure and 

habitat at a broad scale. Group 2 includes trees that are 

not significant components of the forest canopy owing 

to small size or to limited occurrence in western 

Washington; these species may occur infrequently 

across broad areas or may be common within a limited 

habitat. Group 3 consists of trees that are rare in 

western Washington or are represented by disjunct 

populations. 

We created distribution maps for all tree species of 

western Washington to show documented occurrences 

using the latest available data (appendix A).

Drawing on information from a variety of published 

sources, we compiled profiles of the western 

Washington tree species (appendix B). These profiles 

emphasize biological and ecological characteristics 

that were deemed relevant to the trees’ potential 

adaptation to predicted changes in climate.
4 Climate Change and Forest Biodiversity in Western Washington

FOREST TREE VULNERABILITY 

ASSESSMENT

Methods

A vulnerability assessment is a systematic process of 

identifying and quantifying the areas of vulnerability 

within a system (Glick and Stein 2010), or in this case, 

forest tree species. Our objectives for vulnerability 

assessment were to: (1) select a method that is 

straightforward to apply, transparent, flexible, and 

provides for easy application of sensitivity analysis, 

and (2) rank the tree species of Group 1 (see table) 

according to their vulnerability to climate change 

impacts. 

After testing several methods, we choose the Forest 

Tree Genetic Risk Assessment System which rates 

each species according to intrinsic attributes and 

external threats that can influence the species’ 

vulnerability to climate change (Potter and Crane 

2010). We ranked tree species for a number of 

characteristics organized into five risk factors: 

distribution, reproductive capacity, habitat affinity, 

adaptive genetic variation, and threats from insects and 

disease. Each risk factor contained multiple variables 

quantifying each tree species’ vulnerability to climate 

change.

We calculated an overall climate change vulnerability 

score (0 to 100) for each species by averaging the five 

risk factors, which were weighted equally. A higher 

score indicates higher climate change vulnerability as 

measured by these risk factors.

NATIVE TREE SPECIES OF WESTERN 

WASHINGTON

Group 1: Widespread forest canopy species

Pacific silver fir

Grand fir

Subalpine fir

Noble fir

Bigleaf maple

Red alder

Alaska yellow-cedar

Engelmann spruce

Sitka spruce

Western white pine

Black cottonwood

Douglas-fir

Western redcedar

Western hemlock

Mountain hemlock

Group 2: Less-common or non-canopy species

Douglas maple

Pacific madrone

Paper birch

Pacific dogwood

Black hawthorn and Suksdorf’s hawthorn 

Cascara

Oregon ash

Western crab apple

Shore pine and lodgepole pine

Quaking aspen

Bitter cherry

Oregon white oak

Pacific willow

Scouler’s willow

Pacific yew

Group 3: Species rare in western Washington

Golden chinquapin

Rocky mountain juniper

Whitebark pine

Ponderosa pine
Climate Change and Forest Biodiversity in Western Washington 5

Group 1 Tree Species

Several trends were evident in the vulnerability scores:

• Trees fell into two general groups: species 

with scores above and below 50.

• All four of the true fir species, Pacific silver 

fir, subalpine fir, noble fir, and grand fir, were 

in the higher-risk group. 

• All species in the higher-risk group, except 

grand fir, had disjunct or geographically 

separated populations, a variable in the 

adaptive genetic variation risk factor. 

• There was a general trend in increasing 

vulnerability with increasing mean elevation 

of occurrence. 

• Douglas-fir, western hemlock, and western 

redcedar, predominant species in areas under 

active management, had low vulnerability 

scores.

• The three broadleaf tree species, red alder, 

black cottonwood, and bigleaf maple, also had 

low vulnerability scores 

The results of this vulnerability assessment suggest 

that high-elevation tree species are at risk under a 

changing climate and thus should be a focus of 

conservation and monitoring.

Group 2 and Group 3 Tree Species

Group 2 tree species were predominantly noncommercial, and, relative to Group 1 species, little 

biological information was available for many of 

them. Therefore, instead of a formal vulnerability 

assessment, we examined general habitat requirements 

and reproductive characteristics relevant to climate 

change vulnerability. Patterns that emerged included:

• Most species regenerate rapidly following 

stand-replacing disturbance, usually through 

both vegetative and sexual reproduction.

• Many of the species are insect-pollinated and 

thus vulnerable to climate-induced changes in 

insect behavior.

• Because many Group 2 species occur in 

canopy gaps, forest edges, or understories, 

they will likely be influenced by changes in 

the growth and reproduction of the dominant 

forest canopy species.

Group 3 tree species are known to be rare within 

western Washington, and, owing to their limited 

distribution, all of these species are already deemed 

vulnerable to the effects of climate change. The four 

Group 3 species are golden chinquapin (listed in the 

regional Interagency Special Status/Sensitive Species 

Program), Rocky Mountain juniper, whitebark pine, 

and ponderosa pine. Each of these species has unique 

habitat requirements and a distribution that could be 

influenced by climate change.

Results: Group 1 species (widespread forest 

canopy trees) of western Washington, ranked 

by overall climate change vulnerability score; 

higher scores indicate greater vulnerability

Tree species

Overall 

vulnerability score

Pacific silver fir 81

Subalpine fir 71

Engelmann spruce 66

Noble fir 61

Grand fir 54

Mountain hemlock 51

Alaska yellow-cedar 51

Western white pine 38

Douglas-fir 31

Bigleaf maple 29

Black cottonwood 28

Sitka spruce 26

Western redcedar 26

Western hemlock 22

Red alder 20
6 Climate Change and Forest Biodiversity in Western Washington

NON-FORESTED HABITATS

Non-forested habitats vulnerable to climate change 

were identified using the scientific literature and 

advice from regional experts. Vulnerable non-forested 

habitats in western Washington are:

• Alpine and subalpine ecosystems

• Dry grasslands (prairies, savannas, and oak 

woodlands) and balds

• Freshwater and coastal wetlands

For each non-forested habitat, we assessed the 

attributes that contributed to climate change, we 

identified the ecosystem goods and services provided, 

and we determined information needs.

Vulnerability was defined as the likelihood that a 

habitat type, either as a whole or in individual 

occurrences, might change in size and distribution, 

undergo significant changes in vegetative community 

composition, or disappear from the landscape in 

response to changes in climate. 

KEY VULNERABILITIES

For each habitat type, we identified key climate 

change vulnerabilities:

Alpine and subalpine ecosystems: Vegetation 

is vulnerable to changes in the duration and 

extent of the winter snowpack, which is 

influenced by summer temperatures (Mote 2003, 

Mote et al. 2005, Nolin and Daly 2006). 

Increased habitat fragmentation is anticipated 

under a warmer climate (Walther et al. 2005). 

Increases are expected in native and non-native 

insect and pathogen outbreaks and related 

disturbances (Dale et al. 2001).

Dry grasslands: Vulnerability is high owing to 

prior degradation resulting from human land use. 

Stress associated with changes in climate may 

favor non-native invasive species over native 

species.

Wetlands: Vulnerability is high as a result of 

past degradation and susceptibility to invasive 

species. Relative vulnerability of wetlands 

depends on water source (Winter 2000). Some 

wetlands may experience significantly greater 

seasonal extremes in water availability.

Wetland, Three Peaks Botanical Area, Olympic 

National Forest

Cheryl Bartlett, USFS

David Peter, USFS

Oak savanna, Joint Base Lewis-McChord, 

Washington
Climate Change and Forest Biodiversity in Western Washington 7

Alpine and subalpine ecosystems, dry grasslands, and 

wetlands are very different habitat types, but they have 

much in common: limited, patchy distributions; a high 

degree of fragmentation or isolation between 

occurrences; and very high biodiversity, including 

many species of plants and animals not adapted to 

other habitats. All three habitats also are especially 

susceptible to invasion by non-native plants, insects, 

and other animals. This combination of factors makes 

each of these habitats particularly vulnerable to 

disturbances resulting from climate change. 

Recommended actions for these habitats centered on 

the need for baseline data, improving maps and 

inventories, and prioritizing sites for conservation, 

restoration, and monitoring.

RECOMMENDATIONS

The recommendations developed during the course of 

this project fall into three categories:

1. Learn about and track changes in plant 

communities as the climate changes. Collect 

baseline data where needed. Monitor the impacts 

of a warming climate on the distribution and 

health of forest tree species and non-forested 

habitats. Look for triggers, such as an increase in 

the frequency of large-scale disturbance, which 

will indicate a need to change our management 

approach.

2. Maintain and increase biodiversity and 

increase resiliency. Focus on increasing stand 

diversity of native forest trees through thinning 

and planting. Initiate restoration activities in 

priority non-forested habitats. Increase disease 

resistance. Preserve genetic diversity, especially of 

isolated populations, and implement ex situ gene 

conservation where appropriate.

3. Prepare for the future. Given uncertainty about 

how climate changes will unfold, a number of 

future scenarios are possible. Select activities that 

will work under a variety of scenarios including a 

potential increase in disturbances such as fires, 

wind storms, and floods, which could be followed 

by greater spread of invasive plant species.

Subalpine habitat, Norse Peak Wilderness, Mt. 

Baker-Snoqualmie National Forest

Robin Shoal, USFS
8 Climate Change and Forest Biodiversity in Western Washington

Forest Trees

 Assess stand health and regeneration of subalpine 

fir, mountain hemlock, and Alaska yellow-cedar, 

the high-elevation tree species that were found to 

be most at risk based on the vulnerability 

assessment. This will establish baseline 

information that can be used to track changes over 

time and form the basis for a conservation and 

monitoring plan.

 Develop a pilot program to monitor vegetative and 

reproductive phenology in seed orchards. 

 Develop a pilot project to plant blister rust 

resistant western white pine in gaps or openings 

created in pre-commercially thinned stands and 

young-growth stands.

 Partner with other land managers in western 

Washington to create a virtual cooperative tree 

seed bank to facilitate reforestation after largescale disturbances such as fire or insect outbreaks.

 Maintain an inventory of high-quality seed for tree 

species that are likely to be needed over the next 

20 years. Place a priority on species that can be 

planted after disturbance. 

o Assess the viability of stored seed, discard nonviable seed, and make new and replacement 

collections as needed.

o Maintain the national forest conifer seed 

orchards which serve as a gene conservation 

area and is the Forest’s most efficient source of 

high quality tree seed.

Non-Forested Habitats

 For alpine and subalpine meadows:

o Map and inventory.

o Review historic aerial photography to identify 

potential trends in tree establishment in 

meadows and tree line change over time. 

o Select individual meadows for monitoring and 

initiate photo-point monitoring and/or periodic 

aerial photography of selected alpine meadows 

to track changes in tree establishment.

 For native dry grasslands, including Oregon white 

oak woodlands and savannas, and balds:

o Map and inventory existing occurrences.

o Use soil maps, aerial photos, and historical 

information to identify potential historical extent 

of these habitats on national forest lands.

 For wetlands:

o Initiate a systematic inventory program to locate 

and describe wetlands and assess their condition. 

o Use historic information and aerial photography 

to identify changes to individual wetlands over 

time.

o Initiate on-going photo-point monitoring of 

selected wetlands.

o Using wetland inventory results, select at-risk 

wetlands for conservation and restoration.

 Collect foundation seed and initiate seed increase 

as needed of native grassland and wetland plant 

species. Target both rare and “workhorse” species 

for ex situ gene conservation and restoration 

purposes.

 For all three habitat types, continue to inventory, 

prevent and treat non-native invasive plant 

species.

TOP 10 PRIORITY ACTION ITEMS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

“The results of this vulnerability assessment suggest that highelevation tree species are at risk under a changing climate and 

therefore should be a focus of conservation and monitoring; 

Douglas-fir, western hemlock, and western redcedar, 

predominant species in areas under active management, have a 

lower vulnerability to a changing climate.”
Climate Change and Forest Biodiversity in Western Washington 9

INTRODUCTION
10 Climate Change and Forest Biodiversity in Western Washington

ASSESSING CLIMATE CHANGE 

EFFECTS ON PACIFIC 

NORTHWEST VEGETATION

Anthropogenic climate change is a great challenge to 

sustainable management of forests and grasslands 

because the rate of climatic change will likely exceed 

some species’ capability to adapt, which in turn will 

alter plant communities and ecosystems. Climate 

change predictions for the Pacific Northwest include 

overall warming, increased winter precipitation, and 

decreased summer precipitation, resulting in warmer, 

wetter winters and warmer, drier summers (Mote and 

Salathe 2009). The extent and duration of the regional 

snowpack is projected to decrease, particularly at 

lower elevations (Elsner et al. 2009, Mote 2003). 

Seasonal stream flow patterns are likely to shift to 

earlier spring peak flows and lower summer flows, 

especially for snowmelt-dominated watersheds 

(Barnett et al. 2005). The effects of long-term climate 

changes on the composition and structure of western 

Washington’s plant communities are difficult to 

predict. There is a limited amount of information on 

climatic tolerance for many species and even less 

information on what complex interactions could result 

from ecosystem-wide exposure to a changing 

environment.

In 2008, a study was initiated to determine how best to 

adapt federal land management on the Olympic 

Peninsula, Washington, to enhance the resilience of 

federal lands to the effects of climate change 

(Halofsky et al., in press). The Olympic Climate 

Change Case Study—a partnership of the U.S. 

Department of Agriculture (USDA), Forest Service, 

Pacific Northwest Research Station and Olympic 

National Forest, with the U.S. Department of Interior 

(USDI), National Park Service, Olympic National 

Park—examined hydrological processes and 

management of vegetation, fish and wildlife habitat, 

and roads to determine strategies and actions for 

adaptation to climate change. The adaptation strategies 

for managing vegetation under climate change 

included gene conservation, disease resistance, 

increasing biodiversity through planting and thinning, 

and increasing preparedness for large disturbances 

including potential increases in invasive species.

The present effort is the next step in addressing 

vegetation management and climate change. The area 

of analysis has been expanded to western Washington

State (fig. 1), and the focus is on two central questions: 

(1) how will climate change affect forest biological 

diversity? and (2) what are the management 

implications of these potential impacts? Biodiversity is 

often viewed from a global perspective (Wilson 1988), 

but in this analysis, biodiversity is defined as “genetic 

variation within species, the variety of species in an 

area, and the variety of habitat types within a 

landscape” (Duffy and Lloyd 2010). As components of 

biodiversity, individual species, habitats, and 

ecosystems can be conservation targets for 

vulnerability assessments (Glick and Stein 2010). It is 

critical to address the effects of a changing climate at 

the level of individual plant species because individual 

species respond differently to climate, with potential 

shifts in distribution resulting in novel species 

associations (Lovejoy and Hannah 2005, Williams et 

al. 2007). Also of particular interest in this project are 

plant communities already known to be vulnerable to 

changes in climate, such as those at high elevations 

and those that are disturbance-dependent.

The target audience for this report is vegetation 

managers on the Mt. Baker-Snoqualmie, Olympic, and 

Gifford Pinchot National Forests. However, this report 

will also provide useful information for other land 

managers in the Pacific Northwest who manage, 

restore, and conserve forests and non-forested habitats 

under a changing climate. Land managers in other 

parts of the country will find that the methods used 

here can be applied to their plant communities using 

local information. Researchers will find signposts to 

the many questions yet to be answered concerning the 

impacts of climate change not only on forests and 

terrestrial habitats, but also on fundamental biological 

processes.
Climate Change and Forest Biodiversity in Western Washington 11
12 Climate Change and Forest Biodiversity in Western Washington

AREA OF STUDY

The area of study is the forests of western Washington; 

analysis was done on data collected on all forest lands 

regardless of ownership. Management options 

presented here are intended for National Forest System 

lands but also may be applied to other land 

management agencies. Recommendations developed 

in partnership with other agencies are identified.

National Forest System lands of western Washington 

have been managed under the Northwest Forest Plan 

(NWFP) since its adoption in 1994 (Moeur et al. 

2005). The NWFP was created with the vision of 

protecting forest habitat while simultaneously ensuring 

a sustainable supply of timber products. The plan was 

developed with a primary focus on late successional 

dependent species and aquatic habitat after a 

management impasse occurred when the northern 

spotted owl (Strix occidentalis caurina) was 

designated threatened under the Endangered Species 

Act. The 1994 Record of Decision amends the 

planning documents of lands administered by the 

USDA Forest Service and USDI Bureau of Land 

Management within the range of the northern spotted 

owl. The NWFP established a system of standards and 

guidelines to provide habitat management direction for 

these agencies.

Six allocation classes were designated within the land 

covered by the NWFP (table 1), each with standards 

and guidelines based on specific objectives. Of the 

24.5 million ac (9.9 million ha) included in the NWFP 

in Washington, Oregon, and northern California, 84 

percent of the land is allocated to one of six designated 

classes, with the remaining 16 percent designated as 

matrix land, where timber harvest and silvicultural 

activities may potentially be implemented (figs. 2, 3, 

and 4). The congressional reserves class includes 

national parks and monuments, wildernesses, and 

other areas where timber is not harvested. Similarly, 

administratively withdrawn areas are lands previously 

designated for non-timber uses, and include recreation 

and visual areas. On late successional reserves, the 

objective is to protect and enhance conditions of late 

successional habitat, while on riparian reserves, 

riparian-dependent resources are emphasized. The 

remaining land is in adaptive management areas, 

which are designated for testing new management 

approaches to achieve ecological and economic health. 

Timber harvest may potentially occur in this class and 

on matrix land; additionally, young forests in managed 

late successional reserves may be thinned.

In western Washington, defined here as the portion of 

the state west of the Cascade Range crest, the NWFP 

covers Olympic, Mt. Baker-Snoqualmie, and Gifford 

Pinchot National Forests, comprising 3.7 million ac 

(1.5 million ha); and Olympic, North Cascades, and 

Mount Rainier National Parks, comprising 1.8 million 

ac (0.7 million ha). Figures 2, 3, and 4 show the 

distribution of NWFP allocation classes within 

western Washington’s national forests; the national 

parks fall within the congressional reserves class. An 

additional 1.6 million ac (0.6 million ha) of forest land 

administered by the Washington State Department of 

Natural Resources (WADNR) is not included in the 

NWFP.

Vegetation management on western Washington’s 

national forests is focused on thinning forest stands 

and restoring plant communities with an emphasis on 

fish and wildlife habitat. On these three forests either 

pre-commercial or commercial tree thinning is 

conducted on close to 7,000 ac (2,800 ha) each year 

combined, most often with the objective of improving 

wildlife habitat. Tree planting is infrequent because 

thinning on these forests is not applied as a 

regeneration harvest; a combined total of fewer than 

300 ac (120 ha) per year are reforested by planting in 

western Washington’s three national forests. A small 

number of planting opportunities are created when 

Table 1. Allocation of Northwest Forest Plan land 

in Washington, Oregon, and northern 

California

Designation Allocation (%)

Congressional reserves 30

Administratively withdrawn areas 6

Late successional reserves 30

Managed late successional areas 1

Riparian reserves 11

Adaptive management areas 6

Matrix land 16
Climate Change and Forest Biodiversity in Western Washington 13

timber is harvested after windstorms on the Olympic 

Peninsula and after lightning-caused fires in the 

Cascade Range. Each year many miles of roads are 

decommissioned, which entails restoration activities 

such as restoring natural drainage, improving soil 

condition, seeding, and mulching to reduce soil 

erosion and noxious weeds and to facilitate the return 

of the native plant community.
14 Climate Change and Forest Biodiversity in Western Washington
Climate Change and Forest Biodiversity in Western Washington 15
16 Climate Change and Forest Biodiversity in Western Washington
Climate Change and Forest Biodiversity in Western Washington 17

GOALS, ASSESSMENT 

TARGETS, AND OBJECTIVES

The goal of this analysis is to conduct an 

assessment of the vulnerability of forest tree 

species and non-forested habitats to climate 

change.

Forest Tree Species

Forest trees are the first priority for analysis of the 

impacts of climate change on individual plant 

species. Trees provide stand structure and dictate 

the composition of plant communities in the 

forests of the Pacific Northwest. Many of these 

tree species also have high economic or cultural 

value. Because trees are long-lived and have long 

generational intervals, they may be slower to 

adapt and migrate and thus may be more at risk to 

changes in climate than forb or grass species. 

Grasses, forbs, and shrubs that are at risk because 

of habitat loss or other factors (though not 

specifically because of predicted changes in 

climate) are protected, monitored, and often 

restored under the Endangered Species Act and 

the Interagency Special Status/Sensitive Species

Program (ISSSSP) (USDA Forest Service 2010c). 

There is only one tree species evaluated in this 

project that is under any special protection: 

Chrysolepis chrysophylla, golden chinquapin, has 

sensitive species status for the Olympic and 

Gifford Pinchot National Forests.

Selected Vulnerable Non-Forested 

Habitats: Alpine and Subalpine 

Habitats, Dry Grasslands, and 

Wetlands

Certain non-forested habitats, and their associated 

species, are more vulnerable to climate change 

owing to geographic location (e.g., high elevation) 

or to expected climate-induced changes in 

hydrology. These vulnerable habitats warrant 

specific adaptation strategies in response to 

projected changes in climate. In this analysis, 

alpine and subalpine, dry grassland, and wetland 

habitats are evaluated.

Objectives

The specific objectives of this analysis are to:

• Assess the potential impacts of predicted 

changes in climate on both forest trees and 

selected vulnerable habitats: alpine and 

subalpine habitats, dry grasslands, and 

wetlands.

• Evaluate tools that have been developed to 

assess vulnerability and mitigate the expected 

stressors of a warming climate.

• Recommend actions that will improve 

understanding of changes taking place among 

tree species and non-forested habitats, 

maintain and increase biodiversity and 

increase resilience, and prepare for an 

uncertain future.

• Collaborate in the implementation of these 

actions with the two other predominant public 

land management agencies in western 

Washington: the National Park Service and the 

Washington Department of Natural Resources.

These objectives follow the guidelines for agency 

accountability in the USDA Forest Service National 

Roadmap for Responding to Climate Change (USDA 

Forest Service 2010d).
18 Climate Change and Forest Biodiversity in Western Washington

PART 1:

FOREST TREE SPECIES
Climate Change and Forest Biodiversity in Western Washington 19

TREE SPECIES OF WESTERN 

WASHINGTON

Introduction

In this report, we evaluate the climate change 

vulnerability of the 34 native tree species that occur on 

western Washington’s national forests, national parks, 

and lands managed by Washington Depart of Natural 

Resources. Here, trees are defined as woody perennials 

capable of producing a single stem with apical 

dominance and reaching at least 20 ft (6 m) in height. 

Of the 34 native tree species occurring in western 

Washington (table 2), 17 are coniferous and 17 are 

broadleaf species. The Abies and Pinus genera contain 

the greatest number of species, four each. All the 

western Washington conifers are evergreen, and all but 

two of the broadleaf trees (Pacific madrone and golden 

chinquapin) are deciduous.

Grouping

To facilitate analysis, we organized the tree species of 

western Washington into three groups (table 2). Group 

1 consists of 15 overstory tree species that are 

common in major portions of western Washington and 

are thus important components of the forest canopy 

and overall forest structure. This group includes 

species that are widespread across western 

Washington (e.g., western hemlock and western 

redcedar at low- to mid-elevations) and species that 

are common within more limited zones (e.g., subalpine 

fir and mountain hemlock in mid- to high-elevation 

habitat). These Group 1 species are a major focus of 

this report because changes in their distribution or 

health could affect forest structure and habitat at a 

broad scale. Group 2 includes trees that are not 

significant components of the forest canopy owing to 

small size (e.g., cascara, Scouler’s willow, and Pacific 

dogwood) or to limited occurrence in western 

Washington (e.g., quaking aspen, paper birch, and 

Oregon white oak). Within the latter category, trees 

may occur infrequently across broad areas or may be 

common within a limited habitat. 

The third species group consists of trees that are rare 

in western Washington or are represented by disjunct 

populations. The species in this group are golden 

chinquapin, whitebark pine, Rocky Mountain juniper, 

and ponderosa pine.

Habitats

Most of the forests of western Washington are 

dominated by large, long-lived conifers, while 

broadleaf trees are generally confined to the forest 

understory and edges, canopy gaps, disturbed areas, 

riparian zones, and very wet or dry sites. Many of the 

broadleaf species typically occur individually or in 

groves and are not major components of forest stands. 

Only a small number of the broadleaf trees, including 

red alder, bigleaf maple, black cottonwood, and 

Oregon white oak, are often significant components of 

a forest canopy.

Distribution

The diverse physiography of western Washington is 

associated with a wide variety of ecological niches and 

vegetation types. The major forest types can be 

described as potential natural vegetation zones 

(Henderson 2009): the climax vegetation types that 

would develop under the current climate in the 

absence disturbance (figs. 5, 6, and 7). Given projected 

changes in climate, future zones are likely to differ 

from those shown for current conditions.

Some of the most common conifers of western 

Washington—including western hemlock, western 

redcedar, and grand fir—have ranges restricted to the 

Pacific Northwest maritime zone, which includes the 

coastal strip from southeastern Alaska to northern 

California and the moist western slopes of the northern 

Rocky Mountains. The high-elevation conifers of 

western Washington—such as whitebark pine,

Engelmann spruce, and subalpine fir—are tolerant of 
20 Climate Change and Forest Biodiversity in Western Washington

Table 2. Native tree species of western Washington1

Scientific name Common name Symbol Group2 Division Type

Abies amabilis Pacific silver fir ABAM 1 Conifer Evergreen

Abies grandis Grand fir ABGR 1 Conifer Evergreen

Abies lasiocarpa Subalpine fir ABLA 1 Conifer Evergreen

Abies procera Noble fir ABPR 1 Conifer Evergreen

Acer macrophyllum Bigleaf maple ACMA3 1 Broadleaf Deciduous

Alnus rubra Red alder ALRU2 1 Broadleaf Deciduous

Cupressus nootkatensis Alaska yellow-cedar CUNO 1 Conifer Evergreen

Picea engelmannii Engelmann spruce PIEN 1 Conifer Evergreen

Picea sitchensis Sitka spruce PISI 1 Conifer Evergreen

Pinus monticola Western white pine PIMO3 1 Conifer Evergreen

Populus balsamifera ssp.

trichocarpa

Black cottonwood POBAT 1 Broadleaf Deciduous

Pseudotsuga menziesii Douglas-fir PSME 1 Conifer Evergreen

Thuja plicata Western redcedar THPL 1 Conifer Evergreen

Tsuga heterophylla Western hemlock TSHE 1 Conifer Evergreen

Tsuga mertensiana Mountain hemlock TSME 1 Conifer Evergreen

Acer glabrum var. douglasii Douglas maple ACGLD4 2 Broadleaf Deciduous

Arbutus menziesii Pacific madrone ARME 2 Broadleaf Evergreen

Betula papyrifera Paper birch BEPA 2 Broadleaf Deciduous

Cornus nuttallii Pacific dogwood CONU4 2 Broadleaf Deciduous

Crataegus douglasii and 

C. suksdorfii3 Black hawthorn and 

Suksdorf’s hawthorn 

CRDO2

CRSU16 2 Broadleaf Deciduous

Frangula purshiana Cascara FRPU7 2 Broadleaf Deciduous

Fraxinus latifolia Oregon ash FRLA 2 Broadleaf Deciduous

Malus fusca Western crab apple MAFU 2 Broadleaf Deciduous

Pinus contorta var. contorta 

and var. latifolia

Shore pine and 

lodgepole pine

PICOC

PICOL 2 Conifer Evergreen

Populus tremuloides Quaking aspen POTR5 2 Broadleaf Deciduous

Prunus emarginata Bitter cherry PREM 2 Broadleaf Deciduous

Quercus garryana Oregon white oak QUGA4 2 Broadleaf Deciduous

Salix lucida ssp. lasiandra Pacific willow SALUL 2 Broadleaf Deciduous

Salix scouleriana Scouler’s willow SASC 2 Broadleaf Deciduous

Taxus brevifolia Pacific yew TABR2 2 Conifer Evergreen

Chrysolepis chrysophylla Golden chinquapin CHCH7 3 Broadleaf Evergreen

Juniperus scopulorum Rocky mountain juniper JUSC2 3 Conifer Evergreen

Pinus albicaulis Whitebark pine PIAL 3 Conifer Evergreen

Pinus ponderosa Ponderosa pine PIPO 3 Conifer Evergreen

1 Nomenclature follows the U.S. Department of Agriculture Plants Database (USDA NRCS 2010); in cases where multiple common 

names exist, regionally favored names are used here.

2 Group 1 = overstory trees with widespread distribution in western Washington; Group 2 = trees that are not major overstory 

components owing to limited distribution or small size; Group 3 = trees that are rare in western Washington or that are represented 

only by disjunct populations.

3 Black hawthorn and Suksdorf’s hawthorn are described together because much of the available data on these species were 

published when they were known as varieties of the same species. For convenience, the two species are simply referred to as 

“black hawthorn” in the text.
Climate Change and Forest Biodiversity in Western Washington 21
22 Climate Change and Forest Biodiversity in Western Washington
Climate Change and Forest Biodiversity in Western Washington 23
24 Climate Change and Forest Biodiversity in Western Washington

low temperatures, and their ranges stretch northward 

into interior Canada and eastward across the U.S. 

Rocky Mountains. Other conifer species with broader 

ecological amplitudes—including Douglas-fir, 

ponderosa pine, and lodgepole pine—have expansive 

ranges that stretch from Canada, throughout the 

western United States, and into Mexico.

The broadleaf trees of western Washington include 

species found predominantly in the Pacific Northwest, 

such as red alder and bigleaf maple, as well as species 

covering substantial portions of North America, such 

as quaking aspen, paper birch, and Scouler’s willow.

Distribution maps

Distribution maps for tree species of western 

Washington were created with the intention of 

showing documented occurrences using the latest 

available data (appendix A). For most of these species, 

high-quality range maps are available elsewhere (e.g., 

Little 1971, 1976); however, at the scale of this 

assessment, such range maps lack the desired 

resolution. Alternatively, computer models have been 

used to predict changes in tree species’ habitat based 

on climate and other environmental variables (e.g., 

Crookston 2010, Hargrove and Hoffman 2005). While 

these model predictions are useful for many purposes, 

they are designed to produce maps predicting suitable 

habitat rather than current species distributions.

Map data were acquired from a variety of sources 

(table 3). The majority of the data shown on the maps 

in appendix A are from three Forest Service sources 

and from the National Park Service. The sources of 

Forest Service data are: Forest Inventory and Analysis 

(FIA) (USDA Forest Service 2010b), the Current 

Vegetation Survey (CVS) (USDA Forest Service 

2008), and the Forest Service Region 6 Ecology 

Program Core Dataset (USDA 2010a) (plot locations 

for each data source are shown on pages A-3 through 

A-6). Inventory data from WADNR were not in a 

format conducive to the mapping of individual species 

occurrences; thus, these data generally were not used 

for species maps. In some instances, however, data 

collected by WADNR were used when the FIA dataset 

failed to adequately represent known occurrences of a 

species on WADNR lands (e.g., golden chinquapin 

and noble fir).

While the combined data of the major inventories 

described the distributions of most species well, 

sampling protocols occasionally excluded certain 

species. For example, small trees such as black 

hawthorn and pacific willow were considered to be 

shrubs according to some tree inventory protocols. For 

such species, data from FIA, CVS, or Park Service 

inventories might be absent from one or more of the 

national parks or national forests. In other cases, 

known ranges of infrequently occurring species were 

poorly represented in inventories simply because they 

rarely occurred on the sample plots (e.g., Oregon white 

oak). For species underrepresented in the four major 

inventories, data were drawn from other sources 

including herbarium specimens collected from 

documented locations and species-specific surveys 

conducted by public agencies. These additional data 

sources were not added for species with ranges already 

fully represented by data from the four major 

inventories.

Interpreting maps

Data collection protocols differed among inventories; 

thus, several factors should be considered when 

interpreting maps. First, plot density varied by 

inventory; therefore, the density of points on a map 

does not necessarily correspond to the density at which 

a tree species occurs. For example, if the range of a 

species encompasses a national forest and an adjacent 

national park, the density of mapped points could be 

much greater in the national park than in the national 

forest. But this higher density of mapped occurrences 

may be a result of a higher density of sampling 

locations in the park and unrelated to an actual 

difference in the frequency of the species’ occurrence. 

Additionally, the density of mapped species 

occurrences is affected by sample plot size, which 

varied among inventories. An inventory that uses 

larger plots is likely to sample a given species more 

frequently on its plots compared to an inventory that 

uses smaller plots. Finally, the density of mapped 

species occurrences is a function of inventory design. 

An inventory of regularly spaced plots on a grid (e.g., 
Climate Change and Forest Biodiversity in Western Washington 25

FIA) is much less likely to sample a particular species 

than an inventory with an objective of locating and 

sampling that species (e.g, herbarium collections or 

species-specific Forest Service surveys). Owing to 

influences of such factors, mapped species occurrences 

should be interpreted as representing the extent of a 

species’ distribution rather than as representing its 

density within that distribution.

Tree Species Profiles

Drawing on information from a variety of published 

sources, we compiled profiles of the 34 western 

Washington tree species (appendix B). These profiles 

emphasize biological and ecological characteristics 

that were deemed relevant to the trees’ potential 

adaptation to predicted changes in climate. The 

amount of published information available for each 

species varied significantly. A substantial body of 

literature is available for commercially valuable 

species including Douglas-fir, western hemlock, and 

ponderosa pine. However, other species such as 

western crab apple, bitter cherry, and Scouler’s willow 

have not received much attention despite their 

ecological importance. As a result, the level of detail 

provided in these profiles varies by species.

The tree profiles presented in appendix B focus on the 

ecological characteristics, reproduction and growth, 

genetics, and threats and management considerations 

relevant to each species. The ecological description 

contains information on each species’ distribution, 

habitat, and ecological amplitude; this information 

may assist in predicting a species’ potential response 

to climate-induced changes in its habitat. Reproductive 

characteristics such as seed production, reproductive 

age, and seed dispersal distance affect the rate at 

which a species evolves and migrates. Threats and 

management considerations include disturbances such 

as insects, diseases, and wildfire, which may be 

exacerbated by a change in climate.

Table 3. Explanation of data sources used to create tree species distribution maps for western Washington

Dataset Source Coverage Inventory design

Data priority for 

maps

Forest Inventory and 

Analysis (FIA)

USDA Forest 

Service, Region 6

All public and private 

lands1 Regularly spaced plots

Always used2

Current Vegetation 

Survey (CVS)

USDA Forest 

Service, Region 6

National forests Regularly spaced 

plots

Always used2

USFS Region 6 

Ecology Program

USDA Forest 

Service, Region 6

National forests Plots located 

according to plant 

community type

Always used

National parks USDI National Park 

Service

Lands managed by 

the National Park 

Service

Irregularly spaced 

plots

Always used2

University of 

Washington 

Herbarium

Burke Museum, 

University of 

Washington

Public and private 

land in Washington

Species collections 

by many individuals 

with various 

objectives

Used when other 

data sources did not 

adequately 

represent known 

distribution

National forest 

surveys

USDA Forest 

Service, Region 6

National forests Surveys based on 

individual species of 

interest

Used in cases where 

surveys were 

conducted

Other WADNR; USDA 

Forest Service 

Pacific Northwest 

Research Station; 

Department of 

Defense

Various Surveys based on 

individual species of 

interest

Used when other 

data sources did not 

adequately 

represent known 

distribution

1 A small amount of random error was intentionally added to the FIA plot locations to protect the identity of landowners.

2 In a few cases, these datasets did not include species that, at the time of data collection, were considered shrubs rather than 

trees. Thus, inventory data for a given species might be absent from one or more of the national forests or national parks.
26 Climate Change and Forest Biodiversity in Western Washington

VULNERABILITY ASSESSMENT 

OF WESTERN WASHINGTON 

TREE SPECIES

Introduction

Each tree species has a unique set of factors that 

determines its vulnerability to climate change. Among 

the many such factors are inherent sensitivity to 

changes in temperature and precipitation patterns, 

genetic capacity to adapt to changing habitat, and seed 

dispersal sufficient for the species to follow 

geographic shifts in habitat.

A vulnerability assessment is a systematic process of 

identifying and quantifying the areas of vulnerability 

within a system (Glick and Stein 2010), or in this case, 

forest tree species. We chose to use vulnerability 

assessment models to address the following questions 

about the vulnerability of western Washington’s tree 

species to projected climate change:

• How vulnerable to climate change are the tree 

species of western Washington?

• How do we identify the underlying causes of a 

species’ vulnerability?

• Can vulnerability of tree species to climate 

change be quantified in a way that facilitates 

ranking to prioritize management response?

Our objectives for vulnerability assessment were to: 

(1) select a method that is straightforward to apply, 

transparent, flexible, and provides for easy application 

of sensitivity analysis; and (2) rank the tree species of 

Group 1 (table 2) according to their vulnerability to 

climate change impacts. Group 2 species were not 

subjected to formal vulnerability assessment ranking 

because most lacked sufficient data in the scientific 

literature. Group 3 species were not ranked because all 

are rare in western Washington and therefore 

considered vulnerable to climate change.

Climate Change Vulnerability 

Assessment Systems

Selecting a Vulnerability Assessment 

System

We first evaluated two publicly available climate 

change vulnerability assessment systems: the 

NatureServe Climate Change Vulnerability Index 

(NSVI) version 2.0 (NatureServe 2010a) and the 

Climate Change Sensitivity Database (CCSD), a part 

of the Pacific Northwest Climate Change Vulnerability 

Assessment (Lawler and Case 2010b). Both of these 

systems were developed recently (since 2009), and at 

this time there are few published reviews based on 

their application (Glick and Stein 2010, NatureServe 

2010a). In our evaluations, we applied these climate 

change vulnerability assessment systems to six 

western Washington tree species. We examined the 

results and critically evaluated the suitability of these 

systems for assessing the tree species of western 

Washington. In our evaluations, we considered each 

system’s ease of use, transparency, flexibility, and 

sensitivity. The full evaluations of the NSVI and 

CCSD systems appear in appendices C and D, and a 

general comparison of the two systems is shown in 

table 4.

Our evaluations revealed that neither the NSVI nor the 

CCSD met all of our requirements for assessing tree 

species’ vulnerability. The CCSD contained a 

relatively small, fixed set of variables and lacked the 

detail desired for our assessment. Although the NSVI 

contained many of the variables that we deemed 

important for assessing climate change vulnerability, it 

did not allow us to add new variables that we 

considered vital for assessing tree species of western 

Washington. Furthermore, the NSVI’s calculations and 

variable weightings were not clear. After concluding 

that the NSVI and CCSD were not well-suited to our 

objectives, we examined a third model, the Forest Tree 

Genetic Risk Assessment System (GRAS) (Potter and 

Crane 2010). We determined that the Forest Tree 

GRAS provided the best option for developing a 

vulnerability assessment system suited to our regional 

needs and data availability. It offered the flexibility to 

add and remove variables as needed, and its 
Climate Change and Forest Biodiversity in Western Washington 27

calculations were simple and transparent. Therefore, 

we selected the Forest Tree GRAS to assess climate 

change vulnerability of the 15 Group 1 tree species. 

The process of applying the Forest Tree GRAS, and 

the results, are described in detail in the following 

sections.

The Forest Tree Genetic Risk Assessment 

System

The Forest Tree GRAS rates each species according to 

intrinsic attributes and external threats that can 

influence the species’ vulnerability to climate change 

(Potter and Crane 2010). Intrinsic attributes include 

population structure, fecundity, and mechanism of 

seed dispersal; external threats include projected 

climate change and major insects and diseases. These 

attributes and threats are quantified using six risk 

factors, each of which produces a numeric score. The 

factor scores are then used to calculate an overall risk 

score for the species within a given region.

Completing the GRAS entails four steps (Potter and 

Crane 2010): 

• First, the user identifies the area and species of 

interest. 

• Second, the user selects the appropriate risk 

factors. 

Table 4. Comparison of the NatureServe Climate Change Vulnerability Index (NSVI) and the Climate Change 

Sensitivity Database (CCSD) vulnerability assessments and their suitability for evaluating the tree 

species of western Washington

Attribute

Model

NSVI CCSD Evaluation

Required data The model requires 

relatively detailed biological 

data that may not be 

available for some species

The model is based on 

general ecological traits and 

habitat requirements

Both systems allow flexibility for 

missing data; it is unclear 

whether the detailed data 

required by NSVI produces 

more accurate results

Ease of use Relatively easy to use; the 

spreadsheet model was 

accompanied by detailed 

instructions and ran with few 

glitches

Easy to use; the online model 

was simple and 

straightforward but provided 

minimal guidance for rating 

sensitivity factors

NSVI was far more complex but 

provided substantial 

documentation in the model and 

as a separate publication

Model 

transparency

Low transparency; it is 

unclear how rating factors 

are weighted and how 

scores are calculated

Calculation of the sensitivity 

index score is simple and 

clearly described

The high transparency of CCSD 

increases user confidence in 

the model output

Flexibility Up to 26 relatively specific 

factors may be rated; users 

may rate fewer factors 

based on availability of data; 

weighting of factors cannot 

be adjusted

Up to eight general factors 

may be rated; users may rate 

fewer based on availability of 

data; weighting of factors 

may be adjusted by users

Adjustable weighting of factors 

was advantageous for CCSD; 

both systems had some factors 

intended for animal species; 

only NSVI provided detailed 

guidance on applying the model 

to plant species

Output format A categorical vulnerability 

rating (6 categories) and a 

categorical score of 

confidence in rating (4 

categories)

A sensitivity index score (0 to 

100) and a confidence index 

score (0 to 100)

The scores calculated by NSVI 

reflect the precision of the input 

data, while those of CCSD 

suggest greater precision than 

was present in the data

Applicability to 

trees of western 

Washington

Scores are calculated from 

a large amount of detailed 

information, although a few 

of these factors are not 

applicable; other potentially 

important factors are not 

included

This simple index uses rating 

factors that are very general; 

guidance for rating is minimal 

and thus ratings are more 

susceptible to user bias

Neither model included all of the 

factors that we believe affect 

vulnerability of western 

Washington trees; NSVI is a 

useful starting point, as it 

requires users to compile and 

organize relevant data
28 Climate Change and Forest Biodiversity in Western Washington

• Third, for each species, the user collects 

relevant data that are used to calculate risk 

factor scores.

• Finally, the user weights factor scores, 

calculates final scores for each species, and 

then ranks the species based on the final 

scores.

The Forest Tree GRAS is presented in the form of a 

user-friendly guide to developing and scoring risk 

factors. The system provides flexibility in the choice 

of risk factors and variables within factors; however, 

using all factors requires gathering a significant 

amount of information that can be time-consuming. 

Our evaluation of the Forest Tree GRAS is 

summarized in table 5.

In applying the Forest Tree GRAS to the climate 

change vulnerability of the major tree species of 

western Washington (i.e., species Group 1), we 

incorporated variables into five risk factors: 

distribution, reproductive capacity, habitat affinity, 

adaptive genetic variation, and threats from insects and 

diseases. Table 6 summarizes these risk factors, the 

variables selected for each risk factor, and how each 

variable was rated. Most of the information used to 

rate these variables came from published literature and 

is included in the tree profiles in appendix B. 

Following the procedure in the GRAS user’s guide 

(Potter and Crane 2010), we used FIA inventory data 

to describe the distribution of the tree species within 

western Washington. We used some of the life history 

and genetic variation variables described by Potter and 

Crane (2010), although we also added additional 

variables that had greater regional relevance. 

Information on insect and disease threats was provided 

by an expert panel from the USDA Forest Service,

Pacific Northwest Region (Region 6) Forest Health 

Protection Program.

We initially planned to use the climate pressure factor 

as designed by Potter and Crane (2010), in our 

Table 5. Evaluation of the Forest Tree Genetic Risk Assessment System (GRAS) developed by Potter and Crane 

(2010)

Attribute Description Evaluation

Required data All risk factors and variables within risk 

factors are selected by the user; use of 

information on tree distribution and 

density requires knowledge of and ability 

to extract data from existing data sources 

such as the FIA database; assistance is 

available from the FIA program

Allows flexibility for missing data; all information must be 

compiled by the user, which can require significant time 

reviewing literature and performing calculations depending 

on the number of variables selected

Ease of use Very easy to use The instructions in the guide are clear and well-organized; 

the use of spreadsheets to summarize information and 

calculate indices makes this approach very accessible; the 

example of the assessment of trees in the sensitivity 

analysis is very useful

Model 

transparency

High transparency; all ratings appear in 

tables and score calculations are 

described

This high transparency increases user confidence in the 

model output; sensitivity analysis is easy and can be done 

quickly

Flexibility Any number of risk factors and variables 

within risk factors can be used, and 

factor and variable weighting is 

adjustable

The boundless choice of risk factors and adjustable 

weighting of factors is very advantageous but also requires 

knowledge of species biology, genetics, and climate 

prediction systems to make sound choices; expert advice 

is critical when the user lacks knowledge in a specific 

subject area, but interpreting and incorporating this 

information can be time-consuming

Output format Scores for each risk factor (0 to 100) and 

an overall vulnerability score and ranking 

for each species

The calculated scores reflect the precision of the input data 

and the weighting used

Applicability to 

trees of western 

Washington

All factors were chosen for their 

relevance to tree species of western 

Washington, assuring applicability 

Compiling and organizing relevant data and discussing 

candidate factors resulted in a greater understanding of the 

vulnerability of trees to climate changes 
Climate Change and Forest Biodiversity in Western Washington 29

application of the Forest Tree GRAS. This risk factor 

incorporates climate change pressure using modeled 

changes in suitable habitat for each tree species, which 

are based on projected changes in future climate. Maps 

showing predicted present and future habitat 

distribution were acquired for Group 1 tree species 

(Hargrove et al. 2010, Rehfeldt et al. 2006). Using 

these maps of present and future habitat distributions, 

we developed a system to combine the results of these 

two modeling approaches and to classify each species’ 

projected habitat distribution as increasing, decreasing, 

or not changing. However, during our peer review 

process, concerns were raised over the level of 

uncertainty associated with the workings of these 

models and the use of bioclimatic envelope models in 

species distribution predictions. After further 

consideration, we decided to drop this risk factor from 

the analysis. A detailed account of the development of 

the climate pressure risk factor and discussion of the 

issues associated with its use are given in appendix E.

Results of Applying the Forest Tree 

Genetic Risk Assessment System to 

Group 1 Tree Species

The following subsections include descriptions of each 

of the five risk factors used in the Forest Tree GRAS, 

key observations made during the assessment, and 

tables showing the risk factor variables and scores for 

the 15 Group 1 tree species. Within each table, tree 

species are ranked based on the score for that risk 

factor; higher scores indicate higher risk given 

projected changes in climate. Both raw scores and 

scaled scores are presented for each factor. The 

purpose of the scaled scores is to provide equal 

weighting to each of the five factors (i.e., scores 

ranging from 0 to 100) for calculation of an overall 

vulnerability score for each species. These overall 

vulnerability scores are presented at the end of this 

section.

Distribution

Approach

The distribution factor is derived from both qualitative 

and quantitative assessments of the distribution of each 

species in western Washington (table 7). The factor’s 

qualitative assessment variable, Distribution Within 

Western Washington, is based on visual examination 

of a species’ distribution map (appendix A). A 

vulnerability rating is assigned to this variable 

according to the overall extent of a species’ 

distribution, regardless of the point density. The 

variable is based on the general assumption that a 

broader distribution is at lower risk of climate change 

effects. The quantitative variable, Frequency of 

Occurrence, is the percentage of FIA plots on which a 

species occurs, regardless of how the occurrences are 

distributed across western Washington. The second 

quantitative variable, Portion of All Canopy Trees on 

Plots, is the average percentage of all canopy trees 

(defined here as trees coded by FIA as in the 

dominant, co-dominant, or open-grown crown classes) 

that a given species represents on the FIA plots on 

which it occurs. Canopy trees are generally the trees 

with the greatest vigor and reproductive capacity 

because they receive more sunlight and typically have 

larger crowns than trees in intermediate and 

suppressed crown classes. Thus, species occupying a 

greater portion of the forest canopy are assigned lower 

vulnerability scores.

Our distribution factor is based on two of the factors of 

Potter and Crane’s (2010) original risk assessment 

system: Population Structure and Rarity/Density. 

Distribution Within Western Washington is a 

surrogate for Potter and Crane’s (2010) variable 

quantifying the size of a species’ range within the area 

of interest (from their population structure factor), and 

our Frequency of Occurrence variable is calculated in 

the same manner as the corresponding variable in 

Potter and Crane’s (2010) rarity/density factor. Portion 

of All Canopy Trees on Plots is a modification of the 

density variable from Potter and Crane’s (2010) 

rarity/density factor.
30 Climate Change and Forest Biodiversity in Western Washington

Table 6. Risk factor and variable descriptions and scoring system for the Forest Tree GRAS; higher scores 

indicate greater vulnerability

Risk factor Variable Description Scoring system

Distribution Distribution within 

western Washington

Qualitative assessment, scored 

by examining distribution maps1 Wide = 0

Moderate = 25

Narrow = 50

Rare = 100

Frequency of 

occurrence 

Percentage of FIA plots with 

species present

Rank of each value as a 

percentage of the data set

Portion of canopy 

trees on plots

Mean portion of all canopy trees 

(dominant, co-dominant, and 

open grown crown classes) of a 

given species in all FIA plots with 

that species present

Rank of each value as a 

percentage of the data set

Reproductive 

capacity2 Dioecy Breeding system Monoecious = 0

Dioecious = 100

Sound seed Proportion of filled seeds in 

mature cones or fruits

High = 0

Medium = 50

Low = 100

Minimum seedbearing ageAge at which seed production 

begins under good growing 

conditions

< 10 years = 0

10 to 20 years = 50 

> 20 years = 100

Seed dispersal 

capacity

Distance within which most seed 

is dispersed

> 0.5 mile = 0

400 ft to 0.5 miles = 50

< 400 ft = 100

Habitat affinity Mean elevation Mean elevation (ft) of all 

occurrences on FIA plots

Rank of each value as a 

percentage of the data set

Successional stage2 Successional stage(s) in which 

the species commonly occurs

Early = 0

Early to late = 50

Late = 100

Habitat specificity2 Habitat specificity relative to all 

other western Washington tree 

species

Low = 0

Medium = 50

High = 100

Drought tolerance2 Drought tolerance relative to all 

other western Washington tree 

species

High = 0

Medium = 50

Low = 100

Adaptive 

genetic 

variation2

Pollen dispersal 

vector

Wind or insects Wind = 0

Insects = 100

Disjunct or 

geographically 

separated 

populations

Populations that are disjunct or 

geographically separated from 

the main portion of the species 

range

No disjunct or geographically 

separated populations = 0

One or more such populations = 

100

Elevation band width 

of seed zones3 Range in elevation within which movement of maladaption due to 

seed movement is minimized

no elevation bands = 0

≥ 1,500 ft = 33

1,000 to 1,500 ft = 67

≤ 1,000 ft = 100
Climate Change and Forest Biodiversity in Western Washington 31

Key observations

• All tree species are widely distributed across 

western Washington, with the exception of 

Engelmann spruce and noble fir, which have 

moderate distributions. This is a result of the 

area of analysis encompassing the western 

edge of Engelmann spruce’s range and the 

northern edge of noble fir’s range. Because the 

wide and moderate distribution categories 

were assigned scores of 0 and 25, respectively, 

Distribution Within Western Washington had 

little effect on species’ overall factor scores. If 

this analysis were applied to all western 

Washington tree species, rather than Group 1 

only, scores for this variable would have a 

wider range and therefore a greater influence 

on factor scores and rankings.

• Frequency of Occurrence was based on a 

ranking of Group 1 species; thus, potential 

scores for this variable ranged from 0 to 100. 

Percentage of plots on which individual 

species occurred ranged from less than 1 

percent (Engelmann spruce) to 70 percent 

(Douglas-fir).

• The variable, Portion of All Canopy Trees on 

Plots, provided an approximation of a species’ 

dominance and reproductive potential 

independent of the total number of plots on 

which that species occurred. Species with high 

risk scores (e.g., Engelmann spruce and 

western white pine) often occurred in small 

numbers and composed only a minor 

component of the forest canopy. The species 

with the lowest risk scores were those often 

occupying major portions of the forest canopy 

where they occurred: Douglas-fir, subalpine 

fir, Pacific silver fir, and red alder.

Table 6, continued

Risk factor Variable Description Scoring system

Major insect 

and disease 

threats4

Threat Insect or disease that impacts 

the health or survival of the 

species

Score for each threat is calculated as 

the product of the severity and 

immediacy scores

Severity A rating of the present impact of 

insect or disease threats 

Minor mortality, usually of alreadystressed trees = 1

Moderate mortality in association with 

other threats = 3

Moderate mortality of mature trees = 

5

Significant/complete mortality in 

related species = 6

Significant mortality of mature trees = 

8

Complete mortality of all mature trees 

= 10

Immediacy Threats weighted based on 

present or expected exacerbation 

by a changing climate

Potential to reach region of interest = 

1

Present in region = 2

Present in region and climate change 

appears to be a contributing factor in 

increases in distribution and impact = 

3 1 See distribution maps in appendix A. 2 Unless otherwise noted, all information is taken from published literature, which is summarized in the tree profiles in appendix B. 3 Randall and Berrang (2002).

4 Information provided by expert panel, U.S. Forest Service Pacific Northwest (Region 6) Forest Health Protection Program.
32 Climate Change and Forest Biodiversity in Western Washington
Climate Change and Forest Biodiversity in Western Washington 33
34 Climate Change and Forest Biodiversity in Western Washington

Engelmann spruce, western white pine, and black 

cottonwood had the highest distribution vulnerability 

scores of the assessed tree species. Conversely, 

western hemlock, Pacific silver fir, Douglas-fir, 

western redcedar, and red alder had the lowest scores. 

With two exceptions, Frequency of Occurrence and 

Portion of All Canopy Trees on Plots scores were not 

widely disparate. The exceptions were subalpine fir 

and western redcedar. Subalpine fir occurred on a 

relatively low number of plots owing to the limited 

extent of its habitat, but it occupied a major portion of 

the canopy where it occurred. Western redcedar 

occurred on a relatively large number of plots but, 

likely as a result of its shade tolerance and capacity to 

survive in sub-canopy positions, averaged less than 18 

percent of canopy trees on those plots.

Reproductive Capacity

Approach

The variables in this risk factor relate to regeneration 

and seed dispersal: Dioecy (breeding system), 

Percentage Sound Seed, Minimum Seed-Bearing Age, 

and Seed Dispersal Capacity (table 8). At greater risk 

are species with lower seed production, shorter seed 

dispersal distances, and more complex breeding 

systems. These scores are based on present seed 

biology and wind patterns, both of which may change 

over the next century as the climate changes and trees 

acclimate. Therefore, we must keep in mind that the 

information presented here is appropriate for the near 

future only and must be updated as new information 

becomes available.

As noted earlier, disturbances that create large 

openings are presently at low levels, and fewer than 

300 ac (120 ha) per year are reforested across the three 

national forests combined. Because many of the tree 

species need openings to reproduce, ranking species 

for reproductive capacity in this case represents the 

relative ability of species to migrate and regenerate if 

large disturbances become more frequent in the future 

under a changing climate (Littell et al. 2010).

Key observations

• All species in Group 1 are monoecious (both 

male and female reproduction on the same 

individual) except for black cottonwood, 

which is dioecious (male and female 

reproduction on different individuals); 

therefore, the Dioecy variable had little effect 

on factor scores and species rankings.

• Because seed of all species assessed is 

primarily wind-dispersed (secondary dispersal 

agents included animals and water), all species 

would have received the same score if a seed 

dispersal vector variable were included; 

therefore, this variable would have had no 

impact on species’ rankings. Although this 

attribute is important for evaluating 

reproductive capacity, we did not include it in 

our application of the index because there was 

no variation among species.

• We evaluated the use of interval between 

heavy seed crops (years) as a variable, but the 

within-species variation was too great to 

adequately classify species.

• Scores for Percentage Sound Seed were 

medium or high (50 or 100) for all species 

assessed.

• Minimum Seed-Bearing Age was classified 

into three groups: under 10 years, 10 to 20 

years, and over 20 years.

• For 11 of the 15 species, most seed falls 

within 400 ft (120 m) of the tree. Although 

long-distance dispersal has been recorded for 

some of these species, the viability of this seed 

is unknown and accounts for a small 

percentage of total seed production.

The four species of fir (Abies) ranked in the highestscoring group for this risk factor, with Pacific silver fir 

at the top. Also in this group were Alaska yellowcedar, Engelmann spruce, Douglas-fir, and western 

redcedar. Species with the lowest scores were western 

hemlock, black cottonwood, red alder, and bigleaf 

maple. Each of these four species had either a low 
Climate Change and Forest Biodiversity in Western Washington 35

value for Minimum Seed-Bearing Age or a great 

dispersal distance.

Habitat Affinity

Approach

The habitat affinity score was calculated from four 

variables selected to characterize species’ habitat, with 

specific attention to aspects of habitat expected to be 

influenced by projected climate change (table 9). 

Higher mean elevation increases vulnerability to 

climate change because the amount of potential habitat 

generally decreases with increasing elevation and 

because a warming climate could further reduce the 

extent of this habitat (Hamann and Wang 2006, 

Parmesan 2006). The successional stage variable was 

included because species adapted to late successional 

stages generally have greater within-population 

genetic diversity than species of early successional 

stages (Hamrick et al. 1992) and thus are assumed to 

be more vulnerable to loss of genetic diversity 

(Myking 2002, Potter and Crane 2010). The Habitat 

Specificity variable represents the specificity of a 

given species’ habitat requirements relative to all other 

western Washington tree species. Species with low 

habitat specificity were assigned low vulnerability 

scores because it was assumed that they were less 

vulnerable to climate-related changes in habitat.

Our habitat affinity factor was based on the habitat 

affinity factor of Potter and Crane’s (2010) risk 

assessment system, with the addition of the variable 

drought tolerance. Species with low drought tolerance 

were assigned higher vulnerability scores because 

seasonal drought is projected to increase. In addition to 

drought, there are numerous other potential stressors 

and disturbances (e.g., fire, windthrow, frost damage) 

that may be exacerbated by climate change. However, 

we chose to add only the drought tolerance variable in 

this analysis because projected increases in 

temperature, and associated increases in growingseason drought, are widely accepted, whereas there is 

less certainty of the degree to which climate change 

may exacerbate other stressors and disturbances 

(Littell et al. 2009b). Information on each species’ 

response to these other stressors is listed in appendix 

B.

Key observations

• Subalpine fir and mountain hemlock had the 

highest mean elevations, whereas red alder, 

Sitka spruce, and bigleaf maple had the lowest 

mean elevations. Mean elevation scores were 

based on a ranking of all Group 1 species and 

ranged from 0 to 100. 

• One species, the highly shade-tolerant Pacific 

silver fir, was classified as late successional. 

Ten species commonly occur in both early and 

late successional stages, and four species are 

predominantly found in early successional 

stages.

• Habitat specificity ranged from low to 

medium for Group 1 species. Because all of 

these species are major forest canopy 

components in western Washington, it was not 

surprising that none of them had a high level 

of habitat specificity.

• Drought tolerance was rated medium to low 

for all species in Group 1. Species with high 

drought tolerance, such as Oregon white oak 

and ponderosa pine, also occur in western 

Washington but to an insufficient extent to be 

included in Group 1.

The species receiving the highest vulnerability scores 

was Pacific silver fir (score of 100), followed by 

mountain hemlock (88), and subalpine fir (65). The 

high vulnerability score of Pacific silver fir resulted 

from its late successional stage, its low drought 

tolerance, and its moderate habitat specificity and 

mean elevation values. Western redcedar, grand fir, 

and Douglas-fir had the lowest habitat affinity 

vulnerability scores, owing in part to low habitat 

specificity and relatively low mean elevations.
36 Climate Change and Forest Biodiversity in Western Washington
Climate Change and Forest Biodiversity in Western Washington 37
38 Climate Change and Forest Biodiversity in Western Washington

Adaptive Genetic Variation

Approach

The adaptive genetic variation factor is based on 

elements that describe a tree species’ ability to adapt to 

a changing climate: genetic diversity, gene flow, and 

population structure (table 10). Genetic variation in 

adaptive traits is important because it provides the raw 

materials for populations to cope with climate change 

through evolution (Aitken et al. 2008). Forest trees 

generally have high levels of both within- and amongpopulation genetic diversity for quantitative traits 

related to adaptation. A wealth of information has been 

collected on this type of genetic variation in 

commercially important trees species through common 

garden experiments. This information has been critical 

in developing seed zones and elevation bands to guide 

seed movement (Randall and Berrang 2002). 

Rehfeldt (1994b) used the term specialist to describe 

species in which genetic variability is organized into 

numerous local populations, each of which is 

physiologically specialized for a particular range of 

environments. Conversely, the term generalist

describes species in which individuals, and therefore 

populations, are attuned to a broad range of 

environments. Because specialist species are closely 

adapted to their local environment and do not have the 

necessary adaptive genetic variation within 

populations to rapidly adapt to a changing climate, 

they are more susceptible to changes in climate. The 

general characteristics of these alternative evolutionary 

strategies are shown in table 11.

Genetic variation in traits related 

to local adaptation is critically 

important in assessing 

vulnerability to climate change. 

Seed zones that have been 

delineated for commercially 

important tree species are 

reflective of levels of genetic 

variation in adaptive traits; 

however, the number and size of 

these seed zones also are 

dependent on the distribution of 

the species. Therefore, in this risk factor, we used seed 

zone elevation band width as a surrogate for adaptive 

genetic variation (table 11). Species with one or no 

elevation band are considered generalists with wide 

climatic tolerances, whereas species with several 

narrow elevation bands are specialists, highly adapted 

to their local environment, with specific climatic 

requirements. For example, elevation bands within 

seed transfer zones for Douglas-fir, a specialist 

species, are 1000 ft (305 m), whereas for western 

white pine, a generalist species, there are no elevation 

restrictions on seed transfer (Randall and Berrang 

2002). Because specialist species are more vulnerable 

to changes in climate, species with narrow elevation 

bands were given a higher score. In several cases, the 

geographic scale of this assessment influenced a 

species’ score. For example, Sitka spruce has 

substantial population differentiation on a range-wide 

scale but not within its range in Western Washington 

(Mimura and Aitken 2007b).

Evolution and response to natural selection depends on 

a number of factors including genetic diversity within 

populations and gene flow from adjacent populations 

(Aitken et al. 2008). For example, gene flow into a 

population from adjacent populations growing at 

warmer temperatures, such as populations at lower 

elevations or farther south, can introduce genetic 

variation that is pre-adapted to a warmer climate. Gene 

flow occurs through movement of seed and pollen; 

however, neither of these vectors is easy to measure on 

a quantitative basis. We considered including seed 

dispersal vector as a variable in this assessment, but 

because all 15 Group 1 species had the same seedTable 11. Comparison of alternative evolutionary strategies.

Characteristic

Evolutionary strategy

Specialist Generalist

Factor controlling physical expression of 

adaptive traits

Genotype Environment

Mechanism for accommodating 

environmental heterogeneity

Genetic variation Phenotypic 

plasticity

Range of environments across which 

physiological processes function optimally

Small Large

Slope of gradients for adaptive traits Steep Flat

Source: Rehfeldt 1994b
Climate Change and Forest Biodiversity in Western Washington 39

dispersal vector, wind, this variable would not have 

affected the results and for that reason was not added. 

However, seed dispersal distance was included in the 

reproductive capacity risk factor. Another vector of 

gene flow, pollen, is usually dispersed by wind or 

insects. For insect-pollinated trees, pollen dispersal 

could be affected if climate change influences the 

seasonal pattern of insect activity and disrupts the 

synchrony between the insect and the time of 

flowering. Insect-pollinated trees were assigned a 

higher vulnerability score because of this required 

interaction with another organism.

Populations that are disjunct or geographically 

separated from other parts of a species’ distribution 

may evolve to be genetically distinct due to the lack of 

exchange of genetic material among populations. This 

may or may not be reflected in adaptive genetic 

variation, but regardless, this genetic uniqueness 

makes these populations high priorities for 

conservation. Additionally, gene flow into populations 

that are isolated or fragmented is often interrupted, 

which reduces opportunities for such populations to 

receive novel adaptive genetic variation. For these 

reasons, species with disjunct or geographically 

separated populations were assigned a higher 

vulnerability score.

Data for all variables in this risk factor were obtained 

from the scientific literature. Elevation band widths 

were obtained from the Washington Tree Seed 

Transfer Zones guidebook (Randall and Berrang 2002) 

for all species with the exception of mountain 

hemlock, subalpine fir, and bigleaf maple. Seed zones 

and elevation bands for these species have not been 

delineated, so information on adaptive genetic 

variation (Benowicz and El-Kassaby 1999; Benowicz 

et al. 2001b; Iddrisu and Aitken, n.d.; Warwell 2011) 

was used in combination with the elevational range of 

these species in Western Washington (appendix B) to 

estimate appropriate elevation bands. 

Key observations

• High-elevation species had the highest factor 

scores (i.e., Pacific silver fir, noble fir, 

Engelmann spruce, subalpine fir, Alaska 

yellow-cedar, and mountain hemlock). This 

primarily reflects the combination of 

populations that are closely adapted to the 

often harsh environments that they inhabit (the 

narrow seed zone elevation bands of specialist 

species) and the presence of disjunct 

populations isolated by topography. 

• Sitka spruce and western white pine, which 

are widespread species with no disjunct 

populations and broad environmental 

tolerances (i.e., generalist species), had the 

lowest scores in this factor.

• All of the species, with the exception of 

bigleaf maple, have wind-dispersed pollen; 

therefore, this item had a minimal effect on the 

factor scores. Because it is insect pollinated, 

bigleaf maple ranked in the middle with the 

same factor score as species that are windpollinated but have narrow seed zone 

elevation bands (e.g., Douglas-fir, grand fir, 

and red alder)

• The six species with disjunct populations 

ranked highest; within this species group, 

species with attributes of specialists ranked 

higher than those with attributes of generalists. 

The same ranking pattern occurred in the 

group of species without disjunct populations.

Insects and Diseases

Approach

This risk factor includes insects and diseases that 

presently affect the tree species under assessment or 

are expected to exacerbate the negative impacts of 

climate changes on tree survival, growth, or vigor 

(table 12). For each tree species, the most important 

insect and disease threats within the area of analysis 

were determined by entomologists and pathologists of 

USFS Forest Health Protection who rated each insect 

and disease according to the severity and immediacy 

of the threat.
40 Climate Change and Forest Biodiversity in Western Washington
Climate Change and Forest Biodiversity in Western Washington 41
42 Climate Change and Forest Biodiversity in Western Washington

We made one modification to Potter and Crane’s 

(2010) original format for this risk factor; we altered 

their threat immediacy rating scale to better represent 

threats in western Washington. We changed the 

definition of immediacy score 2, “approaching region 

of interest,” to “present in region,” and we changed the 

definition of immediacy score 3, “present in region,” 

to “present in region and climate change appears to 

contribute to increases in distribution and impact.” 

Although species-specific predictions for the future 

remain uncertain, these changes were made because 

there are indications that the current trend in climate 

warming has already exacerbated the effects of several 

insects and diseases on western Washington trees.

Key observations

The three tree species with the highest vulnerability 

rankings were true fir species (subalpine fir, grand fir, 

and Pacific silver fir). Each of these were affected by 

at least two important insect pests and two root 

diseases. The threat receiving the highest score for 

these three fir species was the non-native balsam 

wooly adelgid (Adelges piceae). Among all of the 

other tree species, the only threat receiving a similarly 

high score was white pine blister rust, affecting fourthranked western white pine. The species with the lowest 

scores were Alaska yellow-cedar, Sitka spruce, and 

western redcedar.

Ranking Based on Overall Score

The vulnerability score for each risk factor and the 

overall vulnerability score for each species are 

displayed in table 13. The overall vulnerability score 

was calculated by averaging the five risk factors, 

which were weighted equally. Higher overall scores 

indicate higher vulnerability to the effects of climate 

change as influenced by a species’ distribution, 

reproductive capacity, habitat affinity, adaptive genetic 

variation, and threats from insects and diseases. 

Among the 15 Group 1 tree species, overall 

vulnerability scores ranged from 20 to 81 (lowest and 

highest scores possible were 0 and 100, respectively). 

When species were ranked by score, the scores were 

distributed relatively evenly between the highest and 

lowest. There were only two gaps of 10 or more 

points: (1) Pacific silver fir had the highest score by 10 

points, and (2) there was a gap of 13 points between 

Alaska yellow-cedar and western white pine. The 

latter gap divided the tree species into two groups: 

species with scores above and below 50. Several 

trends were evident in the vulnerability scores shown 

in table 13:

• All four of the true fir species—Pacific silver 

fir, subalpine fir, noble fir, and grand fir—

were in the higher-risk group (i.e., the seven 

species with overall scores above 50). The 

four true fir species had the highest scores for 

the reproductive capacity factor (due in part to 

a low percentage of sound seed and a 

relatively high minimum seed bearing age) 

and usually had high scores for the adaptive 

genetic variation and insect and disease 

factors.

• The highest species scores within each of the 

five risk factors nearly always fell within the 

higher-risk species group. The most notable 

exception was the distribution factor score of 

83 for western white pine (overall score of 

38), which was a result of its low frequency of 

occurrence on FIA plots and the small portion 

of canopy trees that it represented on those 

plots.

• All species in the higher-risk group, except 

grand fir, had disjunct or geographically 

separated populations in the genetics factor. 

Grand fir’s overall vulnerability ranking was 

increased by its high score for the insects and 

diseases risk factor, which resulted from a 

relatively high number and severity of insect 

and disease threats.

• There was a general trend in increasing 

vulnerability with increasing mean elevation 

of FIA plot occurrences (fig. 8). With the 

exception of grand fir, all species with overall 

vulnerability scores over 50 had mean FIA 

plot elevations of more than 3,200 ft (975 m) 

(table 9). Conversely, the species with the 

lowest overall vulnerability scores (31 or 

lower) had mean FIA plot elevations of less 
Climate Change and Forest Biodiversity in Western Washington 43
44 Climate Change and Forest Biodiversity in Western Washington

than 1,700 ft (520 m). Because mean FIA plot 

elevation is part of the habitat affinity risk 

factor (table 9), it had an effect on species 

ranking but was not an overwhelming driver, 

as evidenced by the ranking of scores within 

the habitat affinity risk factor when species are 

ranked by overall vulnerability score in table 

13.

• The three broadleaf tree species all had low 

overall vulnerability scores: red alder (20), 

black cottonwood (28), and bigleaf maple 

(29). This was the result of generally low 

scores for all risk factors; for the broadleaf 

species, the only factor score greater than 50 

was the distribution factor for black 

cottonwood.

Conclusions

The results of this assessment can be used to prioritize 

vegetation management and conservation activities

according to the relative climate change vulnerability 

of tree species. However, given the nature of 

vulnerability indices, the most appropriate way to 

apply the results of this type of analysis is to consider 

the trends that present themselves 

rather than placing too much 

emphasis on the score of one species 

compared to another. Potential 

management responses are 

discussed in Part 3 of this report. 

The results of this vulnerability 

assessment suggest that highelevation tree species are at risk

under a changing climate and 

therefore should be a focus of 

conservation and monitoring. Alpine 

and subalpine plant communities 

also were selected as one of the 

three most vulnerable habitats in 

western Washington (see Part 2 of 

this report).

This vulnerability analysis provided 

an opportunity to gather information 

on the forest tree species, to map 

species distributions based on several sources of 

potential risk factors, and to select factors considered 

most important in determining vulnerability to climate 

change. Centralizing this information provided a 

framework for considering the relative importance of 

various life history traits. The calculation of an overall 

risk score provided insight on the combined impact of 

various risk factors that could not have been gained by

examining risk factors individually.

For the Pacific Northwest region, this type of 

vulnerability analysis is most effective when applied to 

a geographic area the size of western or eastern 

Washington State. This scope of analysis would be 

impractical, and broader trends would be lost, if it 

were applied to individual national forests. For 

example, if the analysis included only the Olympic 

National Forest, it would not account for the 

geographical separation between Olympic Peninsula 

and Cascade Range populations of mid- to highelevation tree species. Conversely, if the area of 

analysis were too large and ecologically diverse, a 

single set of risk factors would not be applicable to the 

entire area and would mask regional differences. In the 

case of Washington, combining eastern and western 

Figure 8. Relationship between overall climate change vulnerability 

score and mean elevation of FIA plots on which each of the 15 

Group 1 tree species occurred in western Washington
Climate Change and Forest Biodiversity in Western Washington 45

portions of the state in a single analysis would involve 

simultaneously evaluating the influences of 

substantially different disturbance regimes and 

climates.

Development of the individual risk factors helped 

identify the geographic and ecological patterns 

exhibiting unique challenges within the analysis area. 

For example, the Olympic Peninsula presents a 

challenge because populations of some tree species 

found at mid to high elevations (e.g., Alaska yellowcedar, Engelmann spruce, mountain hemlock, Pacific 

silver fir, and subalpine fir) are genetically isolated 

from the larger populations in the Cascade Range 

(appendix A). This pattern is identified by the variable 

“disjunct or geographically separated populations” 

within the genetic risk factor (table 11). It is evident 

that these species warrant special attention when 

planning conservation activities such as ex situ seed 

collections and monitoring.

The potential impact of climate change may be just 

one of a number of considerations when planning the 

restoration and conservation of a particular species. 

For example, a look beyond the overall ranking scores 

is needed for western white pine, Douglas-fir, and red 

alder. In the case of western white pine, the species 

received a medium overall index score of 38. This was 

due in part to a low risk rating for the adaptive genetic 

variation factor, as this species has seed zones with no 

elevation bands: seed can be moved up and down 

without risk of maladaption. This species also has 

large seed zones—although this was not part of the 

adaptive genetic variation factor—and a wide 

distribution (no disjunct of geographically separated 

populations). Yet, western white pine mortality has 

been very high due to the introduced pathogen 

Cronartium ribicola, which causes white pine blister 

rust (Kinloch 2003). The impacts of this disease and 

mountain pine beetle were reflected in the insects and 

disease factor; however, the score for this factor was 

only 58 because other species were affected by a 

greater number of threats with greater immediacy. 

Nonetheless, national forests will continue to screen 

western white pine trees to find rust-resistant families 

and to develop and maintain orchards for the 

production of rust-resistant seed (Sniezko 2005). This 

work is critical for the restoration of western white 

pine across the landscape.

Douglas-fir and red alder also had relatively low 

overall index scores (table 13). As discussed earlier 

(see adaptive genetic variation factor), these species 

are considered specialists and are highly adapted to 

their local environment. Because of narrow seed zone 

elevation band widths, both species were assigned the 

highest score for that variable (100); however, because 

their distributions are continuous (no disjunct of 

geographically separated populations), their factor 

scores were only 50, lower than the six species that 

also had disjunct or geographically separated 

populations. At the forest level, the high degree of 

local adaptation of Douglas-fir and red alder may be 

critical in the development of monitoring programs 

and in seed source selection. 

These examples illustrate the need to consider all 

aspects of vulnerability to a warming climate at the 

appropriate scale when designing projects at the local 

level.

Vulnerability of Group 2 and 3 

Species

Group 2 consists of trees that are not significant forest 

overstory components owing to their small size or to 

their limited extent in western Washington forests. 

Because many of these species are of limited 

commercial value, they have not been extensively 

researched. Little or no information was available for 

many of the risk factor variables used in the Forest 

Tree GRAS; thus, it was most efficient to exclude the 

Group 2 tree species from the formal vulnerability 

assessment that was applied to the Group 1 species. As 

noted earlier, the Group 3 species—golden 

chinquapin, Rocky Mountain juniper, whitebark pine, 

and ponderosa pine—were not included in the 

vulnerability assessment because they are already 

known to warrant special management attention in 

western Washington, which should include 
46 Climate Change and Forest Biodiversity in Western Washington

consideration of potential impacts of climate change. 

For example, whitebark pine is under threat not only 

from a warming climate but also from white pine 

blister rust and mountain pine beetle, and a regional 

strategy is in place to address these challenges (Aubry 

et al. 2008). Specific management recommendations 

for these two groups of tree species are given in Part 3 

of this report.

Group 2 Species

The species of Group 2 vary widely in habitat 

requirements and habitat specificity. The objective of 

this section is to make a general assessment of these 

species’ vulnerability to climate change by reviewing 

their habitat and reproductive characteristics. The 

attributes discussed were deemed relevant to species’ 

adaptation to climate-related habitat changes, 

including disturbances.

In table 14, the Group 2 tree species are organized 

according to their drought and shade tolerance. Among 

these trees, the ten species of low shade tolerance all 

occupy early seral stages; most depend upon forest 

canopy disturbance (e.g., fire, flood, or insect 

mortality) to become established. However, tolerance 

of extreme soil moisture conditions also allows some 

of these species to persist where most other trees 

cannot survive. Four trees within the low-shadetolerance group are highly drought-tolerant: Pacific 

madrone, Oregon white oak, and shore and lodgepole 

pine. Each of these four trees has a competitive 

advantage over other tree species on relatively harsh, 

dry sites, given the region’s typically droughty 

summers. However, this competitive advantage may 

not be relevant on sites that are currently marginal, 

where even these species may not survive under drier 

conditions. At the other extreme is Pacific willow, and, 

to a somewhat lesser extent, Oregon ash. These 

species tolerate seasonally flooded soils that most 

other tree species cannot survive. The remaining 

species of low shade tolerance—quaking aspen, bitter 

cherry, Scouler’s willow, and paper birch—are not as 

tolerant of drought or flooding and thus rely primarily 

on disturbance to become established.

The five species of medium shade tolerance are 

capable of surviving beneath a partial forest canopy, 

although their growth is faster under full sunlight. 

These species may establish at forest edges or where 

small gaps occur in the forest canopy following the 

death of one or more overstory trees. The species of 

medium shade tolerance also occur following largescale disturbances, although their growth is slower 

than that of the species in the low-shade-tolerance 

group. With the exception of western crab apple, these 

five species are of moderate drought tolerance and 

occur in a variety of forest types in western 

Washington. Western crab apple is most prevalent on 

wet sites where it is 

favored owing to its 

tolerance of seasonal 

flooding.

Within the Group 2 

species, only Pacific yew 

is classified as highly 

shade-tolerant. Pacific 

yew occurs on a wide 

range of sites, from full 

sunlight to the shade 

beneath a dense conifer 

overstory. This species is 

unique in that it is welladapted to growing and 

reproducing under 

Table 14. Shade tolerance and drought tolerance of Group 2 tree species

Drought 

tolerance

Shade tolerance

Low Medium High

Low Pacific willow

Oregon ash

Quaking aspen

Bitter cherry

Western crab apple

Medium Scouler’s willow

Paper birch

Cascara

Douglas maple

Pacific dogwood

Black hawthorn

Pacific yew

High Pacific madrone

Oregon white oak

Shore pine

Lodgepole pine
Climate Change and Forest Biodiversity in Western Washington 47

complete shade. In northern California, Pacific yew 

was found to become increasingly common in older 

conifer stands, where stand-replacing fires were rare 

(Scher and Jimerson 1989).

The Group 2 species can be divided into four groups 

based on seed type and dispersal mechanism (table 

15), although detailed information on attributes such 

as dispersal distance and level of seed production is 

unavailable for most of these species. Pacific willow, 

Scouler’s willow, and quaking aspen produce 

significant numbers of very small, light seeds bearing 

fine hairs; this seed is capable of traveling long 

distances via wind or water. Lodgepole pine, shore 

pine, and paper birch regenerate via small, winged 

seeds that typically fall within several hundred yards 

of the parent tree. This seed is usually dispersed by 

wind, although less frequently it also is dispersed by 

animals. In the case of lodgepole pine, individuals 

within some populations are serotinous, opening to 

release seeds only following the heat of a fire. Douglas 

maple and Oregon ash produce large, winged seed 

usually dispersed by wind. Because it is relatively 

heavy, the seed of these two species likely has a 

limited dispersal distance. The fourth species group is 

defined by the fact that it is typically dispersed by 

animal vectors. Seeds of these eight species often are 

cached or dropped within several hundred yards of the 

parent tree, but there is potential for the seed to be 

transported great distances. Of the Group 2 species, 

approximately half are predominantly insectpollinated; thus, their production of seed is strongly 

influenced on the presence of insect species during 

flowering.

All Group 2 tree species, with the exception of the two 

pines, are capable of reproducing both vegetatively 

and sexually. In many types of vegetative 

reproduction, a developed root system already exists, 

potentially facilitating rapid growth in the initial 

months and years following a disturbance. Forms of 

vegetative reproduction among various Group 2 

species include stump sprouts, root collar (i.e., the 

base of the stem) sprouts, root sprouts, and layering 

(i.e., sprouting of branches that have drooped and 

contacted the soil). Vegetative reproduction is clonal 

and thus does not create the variety of genotypes that 

are produced by sexual reproduction. For this reason, 

vegetative reproduction does not facilitate genetic 

adaptation to a changing environment.

In addition to the habitat and reproductive 

characteristics that influence potential response to 

projected climate change, some of the species in this 

group have other relevant management considerations. 

For example, a species’ distribution in western 

Washington, relative to its overall distribution, could 

affect management decisions. Species such as quaking 

aspen, paper birch, and Engelmann spruce are found 

infrequently in western Washington (appendix A), but 

this region represents only the western edge of their 

distributions (USDA NRCS 2010). Other tree species 

in this group are significantly affected by human 

activities. In the case of Oregon white oak, the species’ 

native distribution occurs primarily where the region’s 

population density is highest; therefore, it is heavily 

impacted by urban and agricultural land use decisions. 

Cascara, which has bark with medicinal properties, has 

been harvested extensively for this reason for more 

than a century. Although cascara is a commonly 

occurring species, preferential harvest of the largest 

trees has significantly altered size and age structures of 

some populations over time (NatureServe 2010b).

All Group 2 species are well-adapted to reproducing 

after disturbance, although Pacific yew typically 

reaches its greatest density in undisturbed conifer 

stands. Some of the Group 2 species grow best under 

regimes of frequent, stand-replacing disturbance, while 

others require only small canopy gaps in which to 

establish. However, most species in this group are 

scattered across western Washington as minor 

components of multiple forest types and therefore will

be influenced by changes that occur in those forests.
48 Climate Change and Forest Biodiversity in Western Washington

Group 3 Species

Each of the four Group 3 species exhibits specific 

attributes that may affect influence vulnerability to 

climate change; these are summarized in table 16.

Golden chinquapin occurs in two disjunct populations 

in Washington: in Mason County on the southeastern 

Olympic Peninsula and in Skamania County on the 

Gifford Pinchot National Forest (appendix A-11). 

These populations are the two northernmost 

occurrences of golden chinquapin; the species’ range 

is predominantly in Oregon and California. Because 

the range of golden chinquapin occurs primarily in 

warmer, drier climates, there is no evidence that it will 

suffer directly from the changes in climate that are 

projected for western Washington. However, the 

origin and genetics of the relatively small, disjunct 

populations occurring in Washington are unknown. 

Therefore, any indirect consequences of climate 

change affecting these populations, such as increased 

competitiveness of associated tree species, are of 

concern because of the potential loss of unique 

genotypes in these populations.

Rocky Mountain juniper occurs sporadically in the 

northern Puget Sound region and on the San Juan 

Islands near sea level and infrequently at elevations as 

high as 5,500 ft (1,670 m) in the northern Olympic 

Range (appendix A-17). Recent research of genetic, 

morphological, and ecological properties indicates that 

the Rocky Mountain juniper occurring in these 

locations is a unique species, known as seaside juniper 

(Juniperus maritima R. P. Adams) (Adams 2007, 

Adams et al. 2010). Regardless of whether seaside 

juniper is widely accepted as a separate species, the 

populations in western Washington remain genetically 

distinct from Rocky Mountain juniper in the Rocky 

Mountains. This fact, combined with its limited 

occurrence in western Washington, suggests that these 

populations may be vulnerable to climate-related 

changes in habitat.

Whitebark pine was the subject of a recent report that 

evaluated a wide range of threats to the species and 

reviewed potential effects of climate change (Aubry et 

al. 2008). The primary concern for whitebark pine is 

the fact that it occupies high-elevation habitat that, 

because of its limited and isolated occurrence, is 

Table 15. Reproductive characteristics of Group 2 tree species 

Species Pollination vector Seed type and dispersal

Primary seed 

dissemination vector

Pacific willow

Scouler’s willow

Quaking aspen

Insect

Insect

Wind

Abundant, very small seeds; may 

be dispersed miles (kilometers) 

Wind

Lodgepole pine

Shore pine

Paper birch

Wind

Wind

Wind

Abundant, small seeds; may be 

dispersed 100s of yards (meters)

Wind

Douglas maple

Oregon ash

Insect, wind

Wind

Large, heavy seeds; probably 

limited dispersal distance

Wind

Pacific madrone 

Western crab apple

Black hawthorn

Bitter cherry

Cascara

Pacific dogwood

Oregon white oak

Pacific yew

Insect

Insect

Insect

Insect

Insect

Insect

Wind

Wind

Seed type varies; may 

occasionally be dispersed miles 

(kilometers) depending on vector

Birds and small mammals
Climate Change and Forest Biodiversity in Western Washington 49

particularly susceptible to climate change. If the alpine 

and subalpine habitats currently occupied by 

whitebark pine become unsuitable, the amount of 

higher elevation habitat to which the species could 

migrate is very limited in extent. The Tree Climate 

Viability Maps (TCVM) (Rehfeldt et al. 2006, 2009) 

and Multivariate Spatio-Temporal Clustering (MSTC) 

(Hargrove and Hoffman 2005, Hargrove et al. 2010) 

models both show substantial decreases in whitebark 

pine habitat in the Cascade Range under projected 

climate change.

Ponderosa pine in western Washington is primarily 

restricted to one location: a 1,900-ac (775-ha) area on 

Joint Base Lewis-McChord, near the city of Tacoma 

(Foster 1997). Beyond scattered populations and 

individuals in the vicinity of Joint Base LewisMcChord, other ponderosa pine populations west of 

the Cascade crest occur only near the crest of the 

Cascade Range, and likely are the result of seed 

transported by animals from east of the crest (Peter 

2010). Ponderosa pine is adapted to warm, dry 

environments; therefore, like similarly adapted species 

(e.g., Pacific madrone, Oregon white oak, and Rocky 

Mountain juniper), projected changes in climate are 

themselves not likely to reduce the extent of suitable 

habitat in western Washington. On some sites, 

increased summer drought may even give these 

species a competitive advantage. Factors other than 

climate, however, may have significant influences on 

their habitat. In the case of ponderosa pine, the 

primary threat to the Joint Base Lewis-McChord 

population is encroachment of Douglas-fir, which has 

accelerated substantially since World War II (Foster 

1997). Prior to European settlement in the mid-1800s, 

frequent burning by Native Americans prevented 

Douglas-fir and other tree species from encroaching on 

these ponderosa pine forests. Without regular fire, 

Douglas-fir regenerates within these western 

Washington ponderosa pine stands, dramatically 

changing the composition and structure of the stands. 

Additionally, the invasive, nonnative understory 

species Scot’s broom (Cytisus scoparius) impedes 

regeneration of ponderosa pine by forming a shrub 

layer and thereby altering the seedbed environment. 

Since the mid-1990s, Joint Base Lewis-McChord has 

conducted ecological restoration activities, including 

Douglas-fir and Scot’s broom removal and prescribed 

burning, to return the ponderosa pine forests to a 

condition similar to that which existed prior to 

European settlement (Foster 1997).

Table 16. Summary of possible climate change vulnerabilities of Group 3 species

Species Possible vulnerabilities to climate change Other notes

Golden chinquapin Western WA populations are inherently vulnerable 

owing to the fact that they are disjunct and of 

relatively small size; genetic uniqueness of these 

populations is unknown; Olympic Peninsula 

population occurs on Forest Service, WADNR, and 

private land; therefore, management will require a 

coordinated effort

Golden chinquapin is adapted to 

warm, dry climates

Rocky Mountain juniper Although it occurs across a wide elevation range, 

western WA populations are small and disjunct; 

Rocky Mountain juniper in western WA is likely a 

different species than that which occurs inland 

Rocky Mountain juniper tolerates 

extreme environments including 

heat and drought

Whitebark pine Occupies high-elevation habitat that is projected to 

decrease under a warmer climate; limited potential 

for migration

Whitebark pine is also threatened 

by white pine blister rust, 

mountain pine beetle, and large 

high-severity fires

Ponderosa pine Restricted primarily to one disjunct population in 

western WA

Ponderosa pine is adapted to 

warm, dry climates; the primary 

western WA population is actively 

managed by Joint Base LewisMcChord
50 Climate Change and Forest Biodiversity in Western Washington

TOOLS AND MANAGEMENT 

OPTIONS

Introduction

This section describes potential actions that can be 

used to identify and respond to the effects of long-term 

climate change on forest trees of western Washington. 

We discuss four topics: (1) monitoring climate change 

effects, (2) vegetation management options, (3) gene 

conservation, and (4) the Seedlot Selection Tool. 

Monitoring of climate change effects produces 

quantitative information that provides a basis for 

deciding what responses may be necessary. Vegetation 

management options for western Washington’s 

national forests are discussed in the context of 

projected climate change effects. Both in situ and ex 

situ conservation of genetic resources are discussed in 

the third section. The recently developed Seedlot 

Selection Tool, designed to match seedlots to local 

climate, is reviewed in the final section.

Monitoring Climate Change Effects 

on Forest Trees

The Role of Monitoring

Monitoring enables us to quantify the influences of 

climate on forest trees; such information is needed to 

support decisions on mitigating potential climate 

impacts and to inform long-term management 

direction. Data from monitoring also can be used to 

validate model predictions and to test assumptions of 

preliminary adaptation strategies. Potential effects of 

climate change on trees include altered reproductive 

and vegetative phenology and growth, impacts on 

biotic seed and pollen vectors, and effects on genetic 

variation and population structure. In the following 

discussion, we address potential effects of climate 

change, as well as resources for monitoring.

Climate Effects on Tree Phenology and 

Growth

In plants, phenology is the annual cycle of 

development, as influenced by seasonal and annual 

variations in climate. Phenological variables include 

the timing of budbreak, flowering, leaf abscission, bud 

set, and the onset of cold hardiness. Although 

relationships between climate and phenological events 

occur at the plant community level, responses to 

climate vary among individual co-occurring species 

(Hoffmann et al. 2010, Miller-Rushing and Primack 

2008, Post et al. 2008).

The effects of climate change on different stages of the 

annual development cycle may vary. A warming 

climate could influence phenological sequences in a 

variety of ways, advancing or delaying all events 

together or advancing or delaying individual events 

while leaving others unchanged. In addition to 

seasonal timing, the annual duration of reproductive or 

vegetative events may increase, decrease, or remain 

unchanged (Post et al. 2008). Climate change will not 

alter the photoperiodic cues for bud set and height 

growth cessation but might affect phenological events 

that are triggered by accumulation of degree-days. It 

may also alter the synchrony of flowering among 

populations, affecting the potential for long-distance 

gene flow via pollen (Aitken et al. 2008).

Because many species of plants and animals have 

shown changes in phenology associated with climate 

patterns, phenology is very susceptible to the influence 

of climate change (Beaubien and Freeland 2000, 

Cayan et al. 2001, Morisette et al. 2008). Models of 

North American tree species predict that, during the 

21st century, climate change will advance vegetative 

phenological events by 5 to 9 days in the spring, 

depending on the climate model scenario (Morin et al. 

2009). Early spring warming leading to earlier 

budbreak exposes new plant growth to an increased 

risk of frost damage (Augspurger 2009, Inouye 2008). 

In Alaska, climate has been implicated in Alaska 

yellow-cedar decline, as warmer temperatures lead to 

earlier melting of the snowpack and dehardening of 

roots on sites where rooting depth is limited by a 

shallow water table. Without the insulating snowpack, 
Climate Change and Forest Biodiversity in Western Washington 51

tree roots have greater susceptibility to freezing 

damage (Schaberg et al. 2008).

Climate during the growing-season influences a tree’s 

radial growth. Environmental variables including 

temperature and water availability influence the 

amount of wood that is formed during the growing 

season (the year’s tree ring) as well as characteristics 

of the wood within that ring. Tree ring data from 

recent years can be compared to historical records to 

better understand the influence of climate on tree 

growth.

Climate Effects on Seed and Pollen 

Vectors

Most of the Group 1 species are wind-pollinated and 

have wind-dispersed seed, while most of the Group 2 

and 3 species are insect-pollinated and/or have animaldispersed seed (table 17). Species that are insectpollinated or have animal-dispersed seed are more 

susceptible to climate change impacts because their 

reproduction is dependent on interactions with animal 

species that also are subject to climate change 

influences (Hegland et al. 2009). Insect pollinators are 

predicted to be particularly susceptible to changing 

temperature regimes; if phenological responses to 

climate change in plants and insects are not parallel, 

this will result in mismatches between these mutalistic 

partners, potentially causing reductions in pollination 

(Hegland et al. 2009). For insect-pollinated tree 

species, reductions in seed production or seed viability 

are indicators that monitoring may be needed to assess 

pollination vectors.

Genetic Variation and Population 

Structure

It will be challenging to measure the effect of climate 

change on genetic diversity of trees owing to long 

generation times and the fact that adaptation is likely 

to lag behind environmental change (Aitken et al. 

2008, Lynch and Lande 1993, Savolainen et al. 2004). 

Genetic change in trees occurs very slowly; changes in 

genetic variation as a result of projected climate 

change are likely to be too slow to detect in the next 

100 years (Savolainen et al. 2004).

Tree species have repeatedly adapted to climate during 

their evolutionary history as a result of glaciations and 

subsequent warming patterns. For many species, this 

has led to steep genetic gradients across the landscape 

for some climate-related traits such as phenology (i.e., 

the timing of periodic events such as budburst, budset, 

and flowering) (Hamrick 2004, Savolainen et al. 

2004). For a locally adapted population, a change in 

environment toward less suitable conditions leads 

initially to reductions in reproductive capacity and/or 

survival as a result of maladaptation. Because almost 

all quantitative characters exhibit some genetic 

variation, prolonged directional change in environment 

will generally result in adaptive evolution; however, 

any substantial reduction in population size will reduce 

the opportunities for such adaptation (Lynch and 

Lande 1993).

Forest trees, and conifers in particular, exhibit many of 

the life-history traits associated with high levels of 

genetic variation in molecular markers, such as high 

fecundity, outcrossing, and wind pollination (Hamrick 

et al. 1979), and they generally have high levels of 

genetic variation for traits related to adaptation. 

Although genetic diversity of many commercially 

important conifer species has been well-studied (using 

both selectively neutral molecular markers and 

adaptive quantitative traits), for some tree species this 

information is either completely lacking or does not 

fully cover the species’ distribution. Measuring the 

long-term effects of climate change on genetic 

diversity will require baseline data on genetic variation 

both within populations (observed and expected 

heterozygosity [Ho and He]) and among populations 

(population differentiation [FST or GST]) for tree 

species for which these parameters are currently 

unknown.

Information on genetic variation is especially 

important for species with disjunct populations. For 

more than half of the tree species in Western 

Washington with disjunct or geographically separated 

populations, there is no genetic information available 
52 Climate Change and Forest Biodiversity in Western Washington

Table 17. Forest tree pollen and seed dispersal vectors

Species

Species 

group

Geographic 

distribution in 

western Washington Pollen vector

Seed dispersal 

vector

Alaska yellow-cedar 1 Wide/disjunct Wind Wind

Bigleaf maple 1 Wide Insects Wind

Black cottonwood 1 Wide Wind Wind

Douglas-fir 1 Wide Wind Wind

Engelmann spruce 1 Moderate/disjunct Wind Wind

Grand fir 1 Wide Wind Wind

Mountain hemlock 1 Wide/disjunct Wind Wind

Noble fir 1 Moderate/disjunct Wind Wind

Pacific silver fir 1 Wide/disjunct Wind Wind

Red alder 1 Wide Wind Wind

Sitka spruce 1 Wide Wind Wind

Subalpine fir 1 Wide/disjunct Wind Wind

Western hemlock 1 Wide Wind Wind

Western redcedar 1 Wide Wind Wind

Western white pine 1 Wide Wind Wind

Bitter cherry 2 Wide Insects Birds and mammals

Black hawthorn and 

Suksdorf’s hawthorn 2 Wide Insects Birds and mammals

Cascara 2 Wide Insects Birds

Douglas maple 2 Wide Insects Wind

Lodgepole pine and 

shore pine 2 Wide Wind Wind

Oregon ash 2 Wide Wind Wind

Oregon white oak 2 Moderate Wind Birds and mammals

Pacific dogwood 2 Wide Insects Birds and mammals

Pacific madrone 2 Narrow Insects Birds and mammals

Pacific willow 2 Moderate Insects Wind

Pacific yew 2 Wide Wind Birds and mammals

Paper birch 2 Narrow Wind Wind

Quaking aspen 2 Wide Wind Wind

Scouler’s willow 2 Wide Insects Wind

Western crab apple 2 Wide Insects Birds and mammals

Golden chinquapin 3 Rare/disjunct Wind Birds and mammals

Ponderosa pine 3 Rare/disjunct Wind Wind

Rocky mountain juniper 3 Rare/disjunct Wind Birds and mammals

Whitebark pine 3 Narrow/disjunct Wind Birds and mammals
Climate Change and Forest Biodiversity in Western Washington 53

Table 18. Information available on factors influencing tree species’ genetic vulnerability to climate change

Species

Species 

group

Disjunct or 

geographically 

separated 

population(s)

Genetic data 

available for disjunct 

or geographically 

separated 

population(s)

No genetic 

information 

available

Limited 

genetic 

information 

available

Range-wide 

genetic 

information 

available

Alaska yellow-cedar 1 X Yes X

Bigleaf maple 1 X

Black cottonwood 1 X

Douglas-fir 1 X

Engelmann spruce 1 X No X

Grand fir 1 X

Mountain hemlock 1 X No X

Noble fir 1 X No X

Pacific silver fir 1 X No X

Red alder 1 X

Sitka spruce 1 X

Subalpine fir 1 X No X

Western hemlock 1 X

Western redcedar 1 X

Western white pine 1 X

Bitter cherry 2 X

Black hawthorn and 

Suksdorf’s hawthorn 2 X

Cascara 2 X

Douglas maple 2 X

Lodgepole pine and 

shore pine

2 X

Oregon ash 2 X

Oregon white oak 2 X

Pacific dogwood 2 X

Pacific madrone 2 X

Pacific willow 2 X

Pacific yew 2 X

Paper birch 2 X

Quaking aspen 2 X

Scouler’s willow 2 X

Western crab apple 2 X

Golden chinquapin 3 X No X

Ponderosa pine 3 X Yes X

Rocky mountain juniper 3 X Yes X

Whitebark pine 3 X Yes X
54 Climate Change and Forest Biodiversity in Western Washington

to determine if these populations are genetically 

distinct from populations in the contiguous portion of 

the species’ range (table 18). Of the species with 

geographically separated populations, some species on 

the Olympic Peninsula have relatively large 

distributions there that remain separated from the 

Cascade Range distribution by a lack of suitable 

habitat (e.g., high-elevation sites) between the two 

areas. The large, disjunct Olympic Peninsula 

distributions of these species (e.g., Pacific silver fir, 

subalpine fir, and mountain hemlock) are likely better 

able to adapt to a changing climate than the much 

smaller disjunct populations of other species. 

However, even for these large disjunct distributions, it 

is important to know whether they are genetically 

distinct from the Cascade Range distributions in order 

to determine whether movement of seed between the 

two should be restricted because of genetic 

differences. The species with small disjunct

populations, such as noble fir in the Willapa Hills and 

Engelmann spruce and Rocky Mountain juniper on the 

Olympic Peninsula, may require active and intense 

conservation efforts for protection. An understanding 

of whether these disjunct populations differ genetically 

will be crucial in determining whether it will be 

suitable to move seed from other areas into these 

populations in efforts to increase population size. This 

is especially relevant in situations where the seed 

supply from within a disjunct population is limited.

In the topographically varied environment of western 

Washington, there is a high likelihood that refugia 

exist that could buffer changes in climate. 

Identification and conservation of such refugia are 

critical to maintain seed sources and natural 

biodiversity. Conservation efforts will be a priority for 

any population that is geographically isolated because 

it may represent a current or future refuge for a 

species. Conversely, if such a population is genetically 

distinct, then it may not be an appropriate refuge for a 

species because of its genetic distinctness. An 

understanding of the genetic similarities and 

differences between isolated populations and the 

contiguous portion of a species’ range will be critical 

in prioritizing limited conservation resources. 

Resources For Monitoring Climate 

Change Effects On Trees

Long-term monitoring of tree health and species 

distributions is essential to understanding how these 

factors are influenced by climate. Currently, the Forest 

Service and National Park Service have monitoring 

programs that collect forest vegetation data in western 

Washington. Data from these programs may provide 

some of the information necessary to understand the 

scope of potential climate change effects, but these 

existing programs do not address other anticipated 

biological impacts on trees. The most comprehensive 

monitoring program is the Forest Service Pacific 

Northwest Research Station’s Forest Inventory and 

Analysis (FIA) program, which collects data on all 

forests in the region, regardless of ownership (USDA 

Forest Service 2010b). Within the national parks of 

western Washington, the North Coast and Cascades 

Network uses a program specifically designed to 

monitor the effects of ecological change, using 

protocols similar to those of the FIA program 

(Woodward et al. 2009). The Monitoring on the 

Margins initiative of the USDA Forest Service Forest 

Health Monitoring program is an example of an effort 

designed to identify early effects of climate change on 

already-threatened tree species (Smith et al., n.d.). In 

the Pacific Northwest region, Monitoring on the 

Margins will focus on high-elevation, five-needle 

pines (including whitebark pine in western 

Washington) because these species are threatened by 

white pine blister rust as well as climate change, which 

is projected to have a greater impact on high-elevation 

species.

Owing to the variety of influences that climate has on 

forests, variables that may be affected range from the 

scale of population-level phenology to landscape-scale 

species distributions (table 19). Because relatively 

little is known about the effects of climate on many of 

the region’s tree species, the choice of which species 

to monitor, and thus where to allocate limited 

resources, is particularly important. The vulnerability 

assessment made with the Forest Tree GRAS was 

designed to provide information that may be useful in 

prioritizing tree species for monitoring.
Climate Change and Forest Biodiversity in Western Washington 55

Table 19. Options for assessing potential climate change effects on tree species of western Washington

Potential climate change effect

Effect Importance Examples How to assess effect

Genetic variation Genetic variation is associated with 

life-history traits related to a species’ 

capacity to adapt to environmental 

change; to understand change in 

genetic variation, baseline data are 

needed

Within-population 

variation

Among-population 

variation

Prioritize those species for 

which baseline genetic 

information does not exist; 

initiate programs to assess 

baseline genetic data

Vegetative 

phenology

Growing season length depends on 

growing-season temperature and soil 

moisture availability; duration of 

dormancy is affected by winter 

temperature

Budbreak date 

Bud set date

Monitoring in seed orchards 

or natural stands; WADNR, 

PNW, and R6 initiated pilot 

program of seed orchard 

monitoring; assessments 

also may be done by 

researchers

Reproductive 

phenology

In many species, synchrony of 

flowering, which influences 

pollination, is affected by 

temperature; insect-pollinated trees 

are dependent on the presence of 

insects which, in turn, is influenced by 

environmental conditions 

Flowering dates 

Fruit maturation

Monitoring in seed orchards 

or natural stands; 

assessments also may be 

done by researchers

Regeneration Regeneration allows colonization of 

new habitat and replacement of dead 

trees

Germination 

Seedling survival

Vegetative 

reproduction

Forest Service FIA and 

National Park Service 

NCCN currently monitor tree 

seedlings >15 cm (6 in.) tall; 

species-specific 

assessments will require 

work of researchers

Insect and disease 

damage and 

mortality

Some tree species in the Pacific 

Northwest have incurred widespread 

injury and mortality 

Mountain pine beetle

White pine blister 

rust

Balsam woolly 

adelgid

Requires region-wide 

surveys; FIA Phase 3, 

Forest Health and Protection 

monitoring, and WWETAC 

are involved in assessments

Long-term growth 

rate

Inter-annual climate variation affects 

tree growth and other tree ring 

properties; multi-year growth trends 

can predict mortality

Tree ring width

Ratio of earlywood to 

latewood within a 

ring

Researchers use 

dendrometers to measure 

annual diameter growth; tree 

core samples can be 

extracted to assess past 

growth

Species’ frequency 

of occurrence

A reduction in suitable habitat within 

a species’ range would lead to a 

decline in occurrences

Density (trees per ac 

[ha])

Requires region-wide 

surveys conducted at 

regular intervals; FIA 

inventory is the only current 

example

Species’ range A shift in a species’ range alters 

forest composition, structure, and 

wildlife habitat

Researchers predict 

that the range of 

some tree species 

will shift northward 

Requires region-wide 

surveys conducted at 

regular intervals; FIA 

inventory is the only current 

example 
56 Climate Change and Forest Biodiversity in Western Washington

Annual phenology can be monitored using a variety of 

techniques including repeated observation during the 

growing season, automated photography, and remote 

sensing. In 2009, the Pacific Northwest Research 

Station, Olympic National Forest, and WADNR 

collaborated on a pilot program to monitor tree 

phenology in seed orchards. Trees in seed orchards are 

well-suited to monitoring because they are usually of 

known parentage and are easily accessed by seed 

orchard personnel. Presently, Forest Service seed 

orchards throughout Washington and Oregon contain 

13 of the native tree species of western Washington 

(table 20). These seed orchards have significant 

potential for monitoring climate effects on phenology, 

because many orchards contain multiple individuals 

from 50 to 200 unrelated families. Furthermore, trees 

of the same species from multiple seed zones are 

located in orchards across a broad range of geographic 

and climatic zones. The seed orchard pilot monitoring 

program assesses timing of spring vegetative 

budbreak, a variable known to be associated with 

climate, although additional variables may be 

monitored in the future. Relationships between climate 

and tree phenology also are the subject of ongoing 

research conducted by the Forest Service Pacific 

Northwest Research Station (Gould et al. 2011, 

Harrington et al. 2010).

Relationships between climate and tree growth can be 

assessed by monitoring tree radial growth. Forest 

Service FIA data can be used to examine growth 

patterns at broad spatial and temporal scales (the 

remeasurement interval is 10 years in Washington), 

but assessment of relationships between inter-annual 

climate patterns and tree growth requires annual 

growth data. Such data are most often acquired by 

coring trees and then analyzing tree rings or by 

installing dendrometers on trees. Dendrometers 

provide precise measurements of a tree’s radial growth 

and can be used to assess intra-annual or inter-annual 

growth patterns. Measurements of annual growth are 

relatively resource-intensive; therefore, it is important 

to select trees that are representative of the populations 

of interest. For example, because populations at the 

extremes of a species’ habitat may be the most likely 

to experience climate change effects, sampling may 

need to include trees at the edges of the species’ range 

or at the extremes of its elevation range.

Landscape-level monitoring of 

species frequency and range is a 

substantial undertaking, and the 

best current assessment is FIA’s 

annual inventory, which covers 

both public and private lands. 

The FIA program monitors 

forest composition, regeneration, 

and a variety of forest health 

indicators. While this is the best 

dataset available for monitoring 

range-wide tree species 

distributions, it uses a relatively 

low sampling intensity and is 

designed to provide information 

at broad scale (e.g., western 

Washington). One permanent 

plot is established per 6,000 ac 

(2,400 ha), and 10 percent of 

plots are remeasured annually, 

resulting in a 10-year 

Table 20. Seed orchards and clone banks in Washington and Oregon

Species

Number of seed orchards 

or clone banks in 

Washington and Oregon Total acres

Black cottonwood 2 5

Douglas-fir 62 853

Engelmann spruce 2 16

Grand fir 1 1

Lodgepole pine 7 48

Noble fir 4 89

Pacific silver fir 3 32

Ponderosa pine 37 549

Quaking aspen 1 N/A

Sitka spruce 1 2

Western hemlock 1 5

Western redcedar 2 6

Western white pine 14 127

N/A = number of acres not recorded.
Climate Change and Forest Biodiversity in Western Washington 57

remeasurement interval. 

Long-term data from the FIA inventory will likely be 

an important component of monitoring climate change 

impacts on forest composition, but as specific impacts 

are identified, additional, targeted monitoring 

programs could be needed. For example, Alaska 

yellow-cedar, understood to be suffering from climaterelated decline, is the subject of intensive monitoring 

in Alaska (Hennon et al. 2008, Snyder and Lundquist 

2007).

The FIA annual inventory is not designed to provide 

information on tree reproduction with the precision 

necessary to monitor all climate change effects. 

Assessment of long-term climate effects on abundance 

of tree reproduction and on spatial trends in 

reproduction would require a significantly more 

intensive sampling scheme designed specifically for 

that objective.

The potential effect of insects and pathogens under a 

changing climate is recognized as a major threat to 

forests (Bentz et al. 2010, Littell et al. 2010). Research 

and relatively intensive monitoring are conducted by 

the Forest Service and other agencies to understand the 

impact of biological threats in combination with 

environmental stressors such as drought. Currently, 

tree mortality and damage on all Washington forest 

lands is monitored annually by aerial surveys 

conducted through a cooperative effort by the 

WADNR and the Forest Service Pacific Northwest 

Region (Region 6) Forest Health Protection program. 

Additionally, research on insects, pathogens, and their 

interactions with climate change is conducted by the 

Forest Service Pacific Northwest Research Station’s 

Western Wildland Environmental Threat Assessment 

Center based in Oregon. 

Summary

• Susceptibility to climate change impacts is 

increased for tree species dependent on biotic 

vectors for pollination or seed dispersal. 

Monitoring may be necessary to evaluate 

reproductive limitations resulting from these 

biotic vectors.

• To understand long-term effects of climate 

change on genetic diversity, baseline data are 

still needed for many tree species. Collection 

of this information should prioritize rare 

species and species with disjunct or 

geographically separated populations. 

• Seed orchards are well-suited for monitoring 

the influence of climate on phenological 

variables. Vegetative phenology of trees is 

known to be influenced by climate, but 

reproductive phenology is complex and the 

long-term effects of climate change are 

unknown.

• The Forest Service FIA annual inventory 

provides the most comprehensive landscapescale data on the distribution of tree species; 

however, data cannot be used to make 

inferences at a local level. Specialized surveys 

may be required to assess changes in

distribution of species that are of particular 

interest.

• The FIA inventory data on tree reproduction 

are not precise enough to assess effects of 

climate change; such an assessment would 

require a more intensive inventory design.

• Insects and pathogens are believed to be a 

substantial threat to regional forests, given 

predicted changes in climate. Currently the 

Forest Service and other agencies are 

monitoring these threats and studying their 

potential interactions with climate change.
58 Climate Change and Forest Biodiversity in Western Washington

Vegetation Management Options

Introduction

The two primary ways that vegetation management 

can increase tree species diversity and change species 

distribution are through planting and thinning. Most 

recommended methods for building resiliency in forest 

stands involve planting (Millar et al. 2007). Thinning 

can be used to change species composition, modify 

stand structure and age composition, and reduce stress 

through density control, increasing vigor of residual 

trees. However, all silvicultural treatments on regional 

national forests must be applied under the directives of 

the Northwest Forest Plan, under which the focus of 

vegetation management is terrestrial and aquatic 

habitat restoration and enhancement (Moeur et al. 

2005). Forest management under the Northwest Forest 

Plan varies with land allocation (figs. 2, 3, and 4) and 

has resulted in the planting and thinning programs 

described below.

Tree planting is done on a relatively small scale on the 

Mt. Baker-Snoqualmie, Olympic, and Gifford Pinchot 

National Forests: 50, 20 and 220 ac (20, 8, and 90 ha) 

per year, respectively. Trees are often planted during 

restoration projects such as road decommissioning and 

wildlife habitat improvement. Species planted are 

selected based on a number of site factors including 

elevation, aspect, slope, presence of insects and 

diseases, site preparation capabilities, tree species and 

plant associations in the surrounding stands, as well as 

relative shade tolerance of the planted species. Trees 

also are planted after disturbances such as wildfire and 

wind storms; however, these events are uncommon 

and affect a relatively small number of acres.

The thinning program impacts many more acres than 

planting; each year these three forests thin about 

1,000, 1,800, and 4,100 ac (405, 730, and 1,660 ha), 

respectively, with an emphasis on maintaining species 

diversity and increasing structural diversity. Even so, 

the area thinned annually is less than 1 percent of the 

total land base and has a relatively small impact on the 

forests of western Washington. 

Given the present size and scope of the thinning and 

planting programs, management options to change the 

structure and composition of forest stands on national 

forests in western Washington are limited.

Disturbance

One way to anticipate opportunities to change

vegetation is to prepare for major disturbances. 

Although recent wildfires on western Washington 

national forests have been small, large stand-replacing 

fires have occurred in western Washington at long 

intervals, from about 140 to more than 900 years 

depending on forest type (Agee 1993, Henderson et al. 

1989). Also, there is the potential that fire frequency 

may increase in parts of the region that may become 

much drier as the climate warms (e.g., the eastern half 

of the Olympic Peninsula) (Bachelet et al. 2001), but 

these changes are predicted to occur at least 40 years 

into the future and annual variation will remain 

important.

Disturbances may increase as weather patterns change 

in the future and result in increasing windstorms, 

insect and disease mortality, and landslides (see 

Halofsky et al., in press) for discussion of disturbances 

in the Pacific Northwest). Windstorms that occur on 

the western side of the Olympic Peninsula can be 

severe and result in considerable windfall, including 

partial or complete stand replacement (Dowling 2011). 

However, planting is used only after fallen trees are 

salvaged, and presently salvage operations are 

performed only after windthrow in Adaptive 

Management Areas. Although insects and diseases 

have not caused the level of tree mortality experienced 

east of the Cascade Mountains in Oregon and 

Washington, there are a number of insects and diseases 

that impact forest trees of western Washington (table 

12) and may pose greater threats in the future, 

especially on the drier eastern sides of the Olympic 

Peninsula and the Gifford Pinchot National Forest. 

Given the potential need for seedlings to reforest 

following major disturbances, it is important to 

evaluate the forests’ conifer seed inventory and 

replenish low seed stores for areas that are more likely 

to experience these types of large-scale disturbances. It 

is also important to evaluate the area over which seed 

is collected and combined into seedlots. In order to 
Climate Change and Forest Biodiversity in Western Washington 59

facilitate the creation of custom seedlots to match 

possible changes in seed movement guidelines in the 

future, it would be prudent to collect seed across 

smaller areas than the current seed zones. This would 

make it possible to add a percentage of seed from 

outside the seed zone if and when that becomes 

advisable. 

Assisted Migration and Projecting Future 

Changes in Tree Distribution

Even when planting programs are relatively small, 

discussions of climate change inevitably lead to debate 

over assisted migration: the intentional movement of 

species or populations outside of their natural range or 

beyond their recognized area of adaptation (Joly and 

Fuller 2009, Richardson et al. 2009). Although few are 

suggesting that tree species should be planted outside 

their present distribution at this time, there is much 

discussion of the pros and cons of relaxing seed 

movement guidelines and adding some seed from 

sources outside the established seed zone when 

making a seed lot for sowing (CCSP 2008). 

Well-supported changes in seed movement require 

confidence in predictions of future conditions and the 

range of adaptability of existing populations. Seed 

movement in anticipation of climate changes should be 

supported by experimental evidence and based on 

replicated planting trials. Although research is 

underway that will help evaluate alternative futures in 

plant distribution, this type of information is not yet 

available (O’Neill et al. 2008, St. Clair et al. 2010). 

Operational planting sites on National Forest System 

lands in western Washington are not tree plantations 

and do not provide the experimental design and 

homogenous environmental conditions needed for a 

comparison of the response of seedlings grown from 

different seed sources. Therefore, it is not possible to 

“try something” and evaluate the results.

We examined the output of the MC1 dynamic global 

vegetation model, which provides projections of future 

scenarios for broad vegetation types based on three 

general circulation models (GCMs) and two B1 and 

A2 carbon dioxide emissions scenarios (Bachelet et al. 

2001). Predictions are made for vegetation groups and 

do not include information on individual species. Also, 

projections reflect changes in climate habitat, and only 

indirectly indicate potential changes in the distribution 

of vegetation types. For the Olympic Peninsula, for 

example, two vegetation types are mapped for the 

recent past (1971–2000) and for the decade 2010–

2020: Subalpine Forest and Maritime Evergreen 

Needleleaf Forest (fig. 9). The latter encompasses 

most of the peninsula and does not reflect the many 

vegetation types that are used for forest management. 

For 2010-2020, the Subalpine Forest climate habitat is 

predicted to decrease at all GCMs and emission levels, 

but no changes are projected for Maritime Evergreen 

Needleleaf Forest. 

Projections for 2040–2060 vary among emission levels 

and GCMs (fig. 10). For five of the six scenarios, there 

is a considerable reduction in predicted Subalpine 

Forest climate habitat. Under CSIRO, A2, the 

northwest corner of the peninsula shifts to Temperate 

Warm Mixed Forest, a vegetation type that was not 

present in the 2010–2020 projections. Under both 

emission levels for Hadley, there is an increase in 

Temperate Evergreen Needleleaf Forest along the 

eastern and northeastern part of the peninsula. In both 

these cases, these areas are at low elevation and for the 

most part outside the forest boundary. These maps 

should be regarded only as trends and managers 

should not place too much importance on the 

boundaries of each vegetation type. However, based 

on the model projections, it is possible that in 30 to 50 

years the low-elevation forests of the Olympic 

National Forest could be drier, resulting in changes in 

vegetation and increases in fire frequency and extent. 

For a discussion of the results of MC1 on the Olympic 

Peninsula, see Halofsky et al., in press. Similar results 

were found for both the Mt. Baker-Snoqualmie and the 

Gifford Pinchot National Forests. Projections for 

2040–2060 showed an increase in Temperate 

Evergreen Needleleaf Forest and a decrease in 

Subalpine Forest on the both forests, but only for the 

Hadley GCM. More information on model application 

and projections is also given in appendix E.
60 Climate Change and Forest Biodiversity in Western Washington

Figure 9. Projected modal vegetation types on the Olympic Peninsula for the 2010–2020 time period compared 

to modeled historical vegetation types. Projections are from the MC1 model for three general circulation 

models (GCMs) (rows) and two IPCC SRES carbon dioxide emissions scenarios (columns). The 

Commonwealth Scientific and Industrial Research Organisation’s (CSIRO) GCM projects a relatively cool 

and wet Pacific Northwest, while the Model for Interdisciplinary Research on Climate (MIROC) projects a 

hot and wet Pacific Northwest, and the Hadley model projects a hot and dry Pacific Northwest. The B1 

emissions scenario is characterized by relatively low future emissions, and the A2 scenario is 

characterized by relatively high future emissions (Halofsky 2010). Data source: R. Neilson and the MAPSS 

Team, USDA Forest Service and Oregon State University, Corvallis, Oregon) (Map by J. Muehleck)
Climate Change and Forest Biodiversity in Western Washington 61

Figure 10. Projected modal vegetation types on the Olympic Peninsula for the 2040–2060 time period 

compared to modeled historical vegetation types. Projections are from the MC1 model for three 

general circulation models (GCMs) (rows) and two IPCC SRES carbon dioxide emissions scenarios 

(columns). The Commonwealth Scientific and Industrial Research Organisation’s (CSIRO) GCM 

projects a relatively cool and wet Pacific Northwest, while the Model for Interdisciplinary Research on 

Climate (MIROC) projects a hot and wet Pacific Northwest, and the Hadley model projects a hot and 

dry Pacific Northwest. The B1 emissions scenario is characterized by relatively low future emissions, 

while the A2 scenario is characterized by relatively high future emissions (Halofsky 2010). Data from 

R. Neilson and the MAPSS Team, USDA Forest Service and Oregon State University, Corvallis, 

Oregon) (Map by J. Muehleck)
62 Climate Change and Forest Biodiversity in Western Washington

The silviculturists and geneticists of these three 

national forests agree that seed movement outside 

present seed zones will be considered only when a 

shift in climate is shown to be having a negative 

impact on vegetation and when it becomes apparent 

that active intervention is needed to maintain healthy 

stands and provide wildlife and aquatic habitats. This 

might happen though reduced survival, vigor, and 

growth or changes in life history traits such as 

phenology or pollen and seed production. The 

movement of seed of native tree species from forests 

to the south or from lower elevations risks

implementing an approach that is not self-tending. (A 

self-tending action is one that won’t need to be 

changed later if our projections are incorrect.) Novel 

seed movements could produce trees that are not welladapted, and at maturity these trees could produce seed 

and pollen that could reduce the adaptability of trees in 

surrounding stands, a scenario that would be 

impossible to reverse. It could also upset ecological 

processes in unforeseen ways.

Another consideration regarding seed movement is 

that trees are most susceptible to unfavorable 

environmental conditions during the seedling and 

sapling stages; at maturity, trees can withstand much 

greater ranges in temperature and precipitation. Thus, 

we favor seed source selection for present conditions 

because this will increase the likelihood of early 

survival. To make informed decisions, it is imperative 

that we develop a system to assess climate-related 

changes in forest tree growth and survival. These 

triggers can then be used to implement new planting 

and thinning practices that meet changing climate 

patterns.

New Management Opportunities

One way to increase resiliency in forest stands is to 

create new opportunities to plant species that are 

presently under-represented due to insects, disease, or 

past harvest practices. Historically, western white pine 

was widespread throughout the forests of western 

Washington. Since the introduction of the exotic 

disease Cronartium ribicola, which causes white pine 

blister rust, the presence of western white pine has 

been dramatically reduced. High quality seed of rustresistant western white pine is produced at seed 

orchards on each national forest. The Olympic 

National Forest has initiated a pilot program to create 

artificial gaps or openings in young-growth stands to 

provide opportunities to plant rust-resistant western 

white pine seedlings. Planting may also be 

implemented in older young-growth stands in natural 

openings created by wind or in root rot pockets where 

competing vegetation is not a prohibitive problem. 

A genetic common garden study of western white pine 

indicated that a single seed zone for the Olympic 

Peninsula is sufficient to assure that seedlings are 

adapted to their environment (Campbell and Sugano 

1989). There is a high level of genetic variation in this 

species, but that variation is unrelated to geographic 

location or elevation within the peninsula. Therefore, 

the use of rust-resistant seed orchard seed produced 

from tested families selected throughout the peninsula 

poses no dilemmas over seed movement guidelines. 

The results of the vulnerability assessment presented 

in this report indicate that conifer species that occur 

more often at high elevations are most vulnerable to a 

changing climate (fig. 8). Model results clearly show a 

predicted reduction in subalpine forest type by year 

2040 (fig. 10). In the past, when trees were harvested 

at sites over 3,000 ft (910 m) elevation, noble fir and 

Pacific silver fir were commonly planted, and thus 

seed processing and seedling production techniques 

were perfected. For efficient production of high 

quality seed, orchards were established for both these 

species (see tables 21, 22, and 23 in the next section). 

However, there is no seed in inventory for the other atrisk high elevation species: subalpine fir, Engelmann 

spruce, mountain hemlock, and Alaska yellow-cedar. 

There may be a need to increase restoration of highelevation stands in the future. This will require a 

review of the state of knowledge of seed collection and 

storage as well as growing and planting requirements. 

It may also be prudent to collect seed of these species 

for long-term storage at the National Center for 

Genetic Resources Preservation, in Fort Collins, CO.

In summary,

• The primary silvicultural activity on national 

forests in western Washington is thinning for 
Climate Change and Forest Biodiversity in Western Washington 63

multiple goals including improvement in 

wildlife habitat, diversification of forest stand 

structure, and an increase in biodiversity.

• Planting opportunities are limited, and 

planting prescriptions are based on a number 

of factors, the potential for climate change 

being only one of them.

• We will continue to use locally adapted 

conifer seed sources for the limited number of 

acres planted until changes in weather, 

growth, and survival indicate that that relaxing 

seed movement guidelines is warranted.

• It is critical to investigate opportunities to 

increase stand resilience to climate change, 

such as the creation of gaps to plant 

underrepresented or absent species such as 

western white pine.

Gene Conservation

Introduction

Genetic diversity within and among populations is 

important for a number of reasons, and its 

conservation has become a priority for many species. 

Genetic diversity provides the raw material for 

adapting to changing environments; therefore, 

conservation of genetic diversity protects a 

population’s evolutionary potential, which may be 

especially important under climate change or 

increasing pressures from insects and diseases. Gene 

conservation refers to the tools used to protect and 

maintain genetic diversity. Gene conservation can be 

ex situ, meaning that resources are maintained “off 

site” or outside of a species’ native range (e.g., seed 

banks, seed orchards, off-site plantings); or in situ, 

meaning that resources are maintained “on site” or 

within the native range or source of the population 

(e.g., parks, preserves, and unmanaged lands).

Ex situ Genetic Resources

Seed Orchards

Tree seed orchards in western Washington provide an 

excellent resource for ex situ gene conservation for a 

limited number of species. This resource is shown by 

orchard and species for the three national forests in 

tables 21, 22, and 23. The WADNR also maintains 

forest tree seed orchards for needs on Washington 

state lands (table 24).

Seed Storage

Seed storage for the national forests in Western 

Washington is maintained at two facilities. Bulked 

reforestation seed lots, which include seed from 

multiple parent trees, are stored at the J. Herbert Stone 

nursery in Medford, Oregon. Of the Group 1 species, 

bulk seedlots are available for all species with the 

following exceptions:

• Olympic National Forest lacks grand fir, 

subalpine fir, Engelmann spruce, and 

mountain hemlock;

• Mt. Baker-Snoqualmie National Forest lacks 

Alaska yellow-cedar; and

• Gifford Pinchot National Forest lacks Sitka 

spruce (species not present on the forest).

Across all species on all forests, more than 1,000 lbs 

(450 kg) of seed are currently in storage. However, 

some of this seed is more than 25 years of age and of 

questionable viability. The seed should be tested and 

unusable seed removed from the inventory.

Select tree seedlots, which are seed from a single, 

source-identified tree usually with some desirable 

qualities, are maintained at the Dorena Genetic 

Resources Center in Cottage Grove, Oregon (table 25). 

As with the bulk seedlots, many of these select tree 

seedlots are old, and viability testing is needed to 

assess their condition.
64 Climate Change and Forest Biodiversity in Western Washington

Table 21. Ex situ genetic resources in seed orchards on the Gifford Pinchot National Forest

Orchard Name Species

Breeding 

zone Elevation (ft)

Orchard area 

(ac)

Families in 

orchard

Cispus Douglas-fir 202-03011 0-1,500 6 130

202-03012 1,500-2,500 10 222

202-03013 2,500-3,500 10 301

Planting Creek Douglas-fir 202-03021 0-1,500 5 50

202-03022 1,500-2,500 12 240

202-03023 2,500-3,500 12 270

White Salmon Douglas-fir 202-03031 0-1,500 5 56

202-03032 1,500-2,500 5 50

202-03042 1,500-2,500 5 50

French Butte Noble fir 022-03064 3,500-4,500 23 125

022-03065 >4,500 23 125

Coyote Western white pine 119-06020 All 23 356

TOTAL 139 1,975

Table 22. Ex situ genetic resources in seed orchards on the Mt. Baker-Snoqualmie National Forest

Orchard Name Species Breeding zone Elevation (ft)

Orchard 

area (ac)

Families in 

orchard

Darrington Pacific silver fir 011-05013 2,500-3,000 12 135

011-05014 >3,500 11 137

Douglas-fir 205-05012 1,000-2,000 10 200

205-05013 2,000-3,000 10 162

R.N. McCullough Noble fir 022-05022 <4,000 10 129

022-05023 >4,000 10 241

Western white pine 119-05010 All 6 100

119-17110 All 6 175

Douglas-fir 205-05022 1,700-2,800 14 388

205-05023 >2,800 10 179

TOTAL 99 2,055

Table 23. Ex situ genetic resources in seed orchards on the Olympic National Forest 

Orchard Name Species

Breeding 

zone Elevation (ft)

Orchard area 

(ac)

Families in 

orchard

Dennie Ahl Pacific silver fir West 1,500-3,000 4.5 45

Both >3,000 3 50

Dennie Ahl Douglas-fir West <1,500 6 200

West 1,500-3,000 16 179

East <1,500 5 50

East 1,500-3,000 7.5 180

East >3,000 4.5 50

Dennie Ahl Western white pine Both All 5 50

Dennie Ahl Sitka spruce 098-09011 All 2 47

Dennie Ahl Western hemlock 098-09011 >3,000 5 50

TOTAL 51.5 804
Climate Change and Forest Biodiversity in Western Washington 65

In situ Genetic Resources

There are extensive areas of protected habitat in 

western Washington that serve as reserves of in situ 

genetic resources. On public lands, more than 3 

million acres (1.6 million ha) are set aside in national 

parks (North Cascades, Mt. Rainier, and Olympic 

National Parks) and congressionally designated 

wilderness areas on national forests. Other protected 

areas include research natural areas and late 

successional reserves administered by the U.S. Forest 

Service, as well as state parks and WADNRadministered natural area preserves and natural 

resource conservation areas.

White Pine Blister Rust Resistance Screening

White pine blister rust, caused by the fungus 

Cronartium ribicola, is an exotic disease that was 

unintentionally introduced to western North America a 

century ago (Benedict 1981). It infects all five-needle 

pines and has had severe impacts on both western 

white pine and whitebark pine in Washington. 

Infection level varies considerably by stand and can 

range from less than 5 percent to nearly 75 percent of 

trees (Shoal and Aubry 2006). Natural levels of 

resistance to blister rust are relatively low. However, a 

program was initiated in the late 1950s to screen 

individual western white pine trees for resistance and 

to produce seed for production of rust-resistant 

seedlings for reforestation efforts in Oregon and 

Washington. Similar work on whitebark pine was 

started in the late 1990s. Genetic resistance to blister 

rust is the key to maintaining viable populations of 

whitebark pine in the presence of the pathogen, and 

planting blister rust-resistant whitebark pine is an 

integral element of the U.S. Forest Service Pacific 

Northwest Region whitebark pine restoration program 

(Aubry et al. 2008). There is no direct evidence that 

levels of blister rust infection will either increase or 

decrease with projected climate change; however, 

promoting resilience in forest ecosystems is key in 

adapting to climate change, and preserving and 

Table 24. Ex situ genetic resources in seed orchards managed by the Washington Department of Natural 

Resources

Species Orchard block Breeding zone

Elevation 

(ft)

Orchard 

area (ac)

Families in 

orchard

Douglas-fir Cascades North Cascades North 1,500-3,000 5.9 50

Cascades South Cascades South 1,500-3,000 7.8 50

Central DNR-Central <2,000 6.0 53

Coast DNR-Coast <2,000 6.0 51

Coastal North Coastal North <2,000 7.0 50

Forks Forks <2,000 7.0 50

Northwest Northwest <2,000 5.5 49

Puget Sound North Puget Sound North <1,500 5.3 50

Puget Sound South Puget Sound South <1,500 8.1 50

South Puget South Puget <2,000 3.3 51

Southwest Southwest <2,000 5.5 53

Noble fir Cascades Lewis <4,000 5.2 67

Ponderosa pine Colville Ponderosa Northeast 2,500-4,000 4.2 58

Ft. Lewis Ponderosa Puget Sound <1,000 7.6 50

Klickitat Ponderosa White Salmon 2,000-3,200 4.0 50

Western redcedar Puget Sound Cedar Puget Sound <2,000 1.0 50

Twin Harbors Cedar Twin Harbors <2,000 1.3 50

Western white pine Westside WWP W. Washington <5,000 0.5 158

TOTAL 91.2 1,188
66 Climate Change and Forest Biodiversity in Western Washington

enhancing biodiversity is a key to resilience. 

Identifying blister rust resistant individuals of both 

western white pine and whitebark pine, so that seed 

can be collected from them and used to grow seedlings 

for reforestation, will be one of the most effective 

ways of ensuring the presence of these species on the 

landscape. In addition, both these species do well after 

disturbance, so if climate change results in an increase 

in size and/or frequency of disturbance, this could 

increase opportunities to put these species back into 

the landscape.

Western white pine—On the three national forests in 

western Washington, there are 1,437 individual 

western white pine trees that have been selected in the 

field for potential blister rust resistance. Since 1971, 

1,300 of these families (individual parent trees) have 

been screened at the Dorena Genetic Resources Center 

(Table 26). Of the 1,300 families screened, 12 percent 

(159 families) have shown some resistance including 

high survival in screening, outstanding slow-rusting 

resistance mechanisms, or high survival in seed 

orchards. More than 90 percent of these families have 

seed in storage at Dorena, although many 

of these seed collections are 25 to 30 years 

old. Of these 159 resistant families, 153 

are represented in at least one seed orchard 

in the region.

Whitebark pine—Since 2005, whitebark 

pine seed from 119 individual trees has 

been collected in western Washington 

(table 27). About 40 percent of these lots 

have been sown to grow seedlings that 

were inoculated with blister rust in 2007. 

Early results show a large amount of 

variation in potential resistance. Increasing 

mortality from progression of the disease 

was evident during the summer of 2010, 2 

years after inoculation. Screening results 

and relative rankings will be updated as 

additional assessments are performed, but 

there are indications of higher relative 

resistance in families from the Cascades 

(Mt. Adams on the Gifford Pinchot 

National Forest, Mt. Rainier National 

Park, and Mt. Baker-Snoqualmie National 

Forest) and lower relative resistance in 

families from the Olympic Peninsula.

Table 25. Ex situ genetic resources in single-tree seedlots in 

storage at the Dorena Genetic Resources Center

National forest Species Seed lots (no.)

Gifford Pinchot Pacific silver fir 121

Grand fir 53

Subalpine fir 37

Noble fir 448

Western larch 96

Whitebark pine 14

Engelmann spruce 63

Western white pine 853

Ponderosa pine 184

Douglas-fir 1,335

Western redcedar 30

Western hemlock 69

Mountain hemlock 52

Mt. Baker-Snoqualmie Pacific silver fir 273

Noble fir 293

Whitebark pine 4

Western white pine 171

Douglas-fir 638

Western redcedar 242

Olympic Whitebark pine 16

Western white pine 99

Douglas-fir 88

TOTAL 5,179

Table 26. Western white pine blister rust screening in 

western Washington

National forest

Number of 

families 

screened

Number of 

families rated 

resistant

Gifford Pinchot 1,001 78

Mt. Baker-Snoqualmie 178 49

Olympic 121 32

Total 1,300 159
Climate Change and Forest Biodiversity in Western Washington 67

Evaluation of the Seedlot Selection 

Tool

The Seedlot Selection Tool (SST) 

(http://sst.forestry.oregonstate.edu/PNW/index.html) is 

an online GIS program designed to help forest

managers match seedlots with planting sites by using 

climate information. The SST incorporates either 

current climate or predicted future climates based on 

selected climate change scenarios. In addition to 

providing planting information, it is designed to be of 

use to anyone desiring maps of present or future 

climates, as defined by temperature and precipitation 

(OSU and USDA 2010). We evaluated the SST to 

assess the potential for its application in examining 

possible habitat suitability for tree seed under future 

climate change scenarios. 

The SST is being developed for the deployment of tree 

seed or seedlings of commercially valuable tree 

species. It predicts either: (1) locations with a climate 

suitable for planting a given seedlot, or (2) the 

appropriate seedlots to plant in a given location. It 

incorporates numerous user-selected inputs to provide 

broad flexibility and applicability across species and 

landscapes. It allows the user to select location, seed 

zone, species, climate data, seed transfer limits, future 

climate scenario models, and emission scenarios. 

Climate data can be based on a specific location 

(latitude and longitude) or based on an entire seed 

zone for a given elevation band. The boundaries of 

existing seed zones can be provided to the SST 

developers for inclusion in the program, which will 

then use these boundaries to calculate the average 

value of climate variables over the entire seed zone. 

The ultimate output of the program is maps of where 

climate is considered suitable for a given seedlot, 

based on climate variables and seed transfer limits 

selected by the user.

Because the SST uses climate data to match seedlots to 

planting sites, species-specific information such as 

genetic variation, adaptation, and habitat are not 

considered. Forest genetics research has shown that 

local adaptation in forest trees is strongly influenced 

by climate (St. Clair et al. 2005). The SST operates on 

the principle that adaptive genetic variation in trees—

which is difficult and time-consuming to measure and 

Table 27. Whitebark pine blister rust screening in western Washington

Location

Number of families 

from which seed 

was collected

Number of families 

in rust resistance 

screening

National forest

 Gifford Pinchot 14 12

 Mt. Baker-Snoqualmie 4 3

 Olympic 16 7

 All national forests 34 22

National park

 North Cascades 26 N/A

 Mt. Rainier 59 N/A

 All national parks 85 27

All locations 119 49

N/A = Information not available at the park level
68 Climate Change and Forest Biodiversity in Western Washington

map—is strongly correlated with climate, so mapping 

climate data across the landscape gives an indication 

of genetic variation across the landscape (Howe 2010). 

To produce accurate maps, however, it is necessary for 

the user to have some knowledge of which climate 

variables are important drivers of local adaptation and 

what the appropriate seed transfer limits are for a 

given species. The SST provides 20 different climate 

variables for the user to select, including variables 

related to temperature, precipitation, aridity, growing 

season length, and heat sum accumulation. However, 

when multiple variables are selected, habitat mapped 

as suitable is restricted to areas that fall within the 

transfer limits of all selected variables, so increasing 

the number of variables selected usually decreases the 

area mapped. If appropriate transfer limits are not 

known a priori, then the SST can use existing seed 

zones to define transfer limits based on the range in 

climatic values (transfer limit = maximum –

minimum) present within the boundaries of the seed 

zone. For example, for a specific location on the Mt. 

Baker-Snoqualmie National Forest (47.83897° N; 

121.57059° W; elevation 1,817 ft [554 m]), the annual 

precipitation is 99.0 in (2,514 mm). The range between 

the maximum and minimum values for the Douglas-fir 

seed zone 1,700 to 2,800-ft elevation band is 44.2 in 

(1,122 mm); therefore, any area where annual 

precipitation is between 54.8 in (1,392 mm) and 143.2 

in (3,636 mm) is considered suitable habitat.

The SST is still under development, and it may prove 

useful to land managers seeking guidance on 

movement of seed. However, the accuracy of the maps 

produced by the SST depends on the user’s knowledge 

of which climate variables are important and what 

transfer limits are appropriate for a given species. As 

with all models of potential climate change effects, 

there is inherent uncertainty as a result of uncertainty 

in projections and in species- and community-level 

responses. As stated on the SST website, 

Because of the uncertainty in climate change 

projections, the tool is really a planning and 

educational tool. It can be used to explore 

alternative future conditions, assess risk, and 

plan potential responses, but cannot tell the 

user exactly which seedlots will be 

optimally adapted to a particular planting 

site in the future. The tool allows the user to 

control many input parameters so the results 

are appropriate for the management 

practices, climate change assumptions, and 

risk tolerance of the user. 

(http://sst.forestry.oregonstate.edu/PNW/

index.html)
Climate Change and Forest Biodiversity in Western Washington 69

PART 2:

NON-FORESTED HABITATS

VULNERABLE TO CLIMATE CHANGE
70 Climate Change and Forest Biodiversity in Western Washington

INTRODUCTION

Climate is considered the dominant controlling factor 

for plant distribution (Woodward 1987). Those 

ecosystems or habitat types in western Washington 

that are the most sensitive to changes in temperature or 

hydroperiod (seasonal patterns of water availability) 

will have the greatest vulnerability to climate change. 

The term “vulnerability” is used here to denote the 

likelihood that a habitat type, either as a whole or in 

individual occurrences, might change in size and 

distribution, undergo significant changes in vegetative 

community composition, or disappear from the 

landscape in response to changes in climate. 

This section discusses the vulnerability to climate 

change of three primarily non-forested habitat types 

(ecosystems): alpine and subalpine habitats; dry 

grasslands (prairies, savannas, and oak woodlands); 

and freshwater and coastal wetlands. These three 

broad habitat types were selected based on a review of 

the current climate change literature and on a survey of 

natural resource scientists from major land 

management agencies— U.S. Forest Service, National 

Park Service (NPS), and the Washington Natural 

Heritage Program (WNHP) of the WADNR. These 

habitat types were identified in 2009 by Forest Service 

botanists and biologists as focal habitats for the draft 

terrestrial restoration strategy for the Forest Service 

Pacific Northwest Region (Region 6, Oregon and 

Washington). Interviews conducted in summer 2010 

with Forest Service botanists and biologists on the 

three western Washington national forests, with 

WNHP ecologists, and with NPS personnel further 

highlighted the concern that natural resource scientists 

and managers express about the potential vulnerability 

of these non-forested habitats to the effects of 

predicted future climate scenarios. 

Wetlands, dry grasslands, and alpine and subalpine 

ecosystems are three very different western 

Washington habitat types, but they have much in 

common: limited, patchy distributions; a high degree 

of fragmentation or isolation between occurrences; and 

very high biodiversity, including many species of 

plants and animals not adapted to other habitats. All 

three habitats also are especially susceptible to 

invasion by non-native plants, insects, and other 

animals. This combination of factors makes each of 

these habitats particularly vulnerable to disturbances 

resulting from climate change. 

In general, management recommendations for habitats 

vulnerable to climate change emphasize resiliency and 

adaptive capacity. They include reducing existing 

stressors, maintaining existing intact ecosystems, 

reducing habitat fragmentation, and improving habitat 

connectivity to facilitate adaptive migration of plants 

and animals. Additional recommendations include 

identifying and tracking key species or controlling 

factors, identifying and protecting potential refugia, 

protecting particular habitats and species at risk, and 

ensuring that the full range of genetic variability is 

maintained within species (Blate et al. 2009, Harris et 

al. 2006, Spies et al. 2010).
Climate Change and Forest Biodiversity in Western Washington 71

ALPINE AND SUBALPINE 

HABITATS

Alpine habitats occupy the highest vegetated 

elevations, above the open subalpine parkland and 

below the glaciers, permanent snowfields, talus slopes, 

rocky peaks, or other non-vegetated surfaces. Alpine 

vegetation, also called tundra, is adapted to a short 

growing season controlled by factors including 

temperature, extent and duration of the snowpack, and 

desiccation by wind and sun. Alpine plant species are 

typically slow-growing perennial forbs (wildflowers), 

grasses, sedges, lichens, and mosses (Grabherr et al. 

2010). 

Subalpine habitats occur between forest line (the 

highest extent of continuous closed-canopy forest) and 

tree line (the highest extent of individual upright trees) 

and thus occupy the transition zone between closed 

forest and treeless alpine tundra. In western 

Washington, forest line and tree line elevations vary, 

with the transition between forested and subalpine 

habitat generally taking place between 5,000 and 6,000 

ft (1,520 and 1,830 m) and alpine tundra beginning 

between 1,000 and 1,500 ft (300 and 460 m) above 

that. Above forest line, forest cover becomes 

discontinuous, with trees occurring in clumps of 

diminishing distribution and stature as elevation 

increases. Adult trees often have a shrubby krummholz 

or wind-shaped dwarf form. Tree species composition 

also may change as conditions become harsher and 

more exposed.

Of the three western Washington habitats considered 

here, alpine and subalpine are the most extensive, 

covering approximately 859,000 ac (348,000 ha) (fig. 

11). Nearly all of this habitat is located within the 

boundaries of national forests and national parks, and 

much of it is within the boundaries of congressionally 

designated wilderness areas.

The western Washington alpine and subalpine habitat 

represented in figure 11 is from the modeled potential 

natural vegetation zones (PNV) of Washington and 

Oregon (Henderson 2009). The zones represent the 

environmental capability of a land area in the absence 

of significant disturbance. The ice masses depicted on 

the map are from the U.S. Geological Survey National 

Hydrography Dataset (NHD) (USGS 2010). Using a 

geographic information system (ESRI ArcMap 9.3), 

we removed the portions of the PNV’s alpine and 

subalpine parkland zones overlain by NHD “ice 

masses” to calculate the total acreage for alpine and 

subalpine habitats. Of those approximately 859,000 ac 

(348,000 ha), 719,000 ac (291,000 ha) are classified as 

subalpine parkland, and 140,000 ac (56,700 ha) are 

classified as alpine.

An example of a subalpine habitat vulnerable to 

climate change is the whitebark pine community found 

in all three of western Washington’s national forests. 

On the Mt. Baker-Snoqualmie and Gifford Pinchot 

National Forests, whitebark pine populations occur 

primarily near the Cascade Crest, and to a greater 

extent east of the crest. On the Olympic National 

Forest, the Buckhorn Wilderness contains the only 

known population of whitebark pine on the forest, as 

well as the Buckhorn Research Natural Area (RNA), 

both of which provide areas for assessing current 

condition and monitoring climate change effects on 

high-elevation ecosystems.

Vulnerability

Alpine plants are considered highly vulnerable to 

impacts associated with a warming climate (Guisan 

and Theurillat 2000) and already serve as an “early 

warning” system for climate change effects (Grabherr 

et al. 2010). Summer temperatures and the duration 

and extent of winter snowpack are key controlling 

factors for plant establishment, distribution, and 

survival in high-elevation landscapes, although 

specific limiting factors vary locally and regionally 

(Millar et al. 2004, Peterson et al. 2002, Woodward et 

al. 1995). In western Washington, summer 

temperatures are predicted to increase during the 21st

century, and the extent and duration of snowpack is 

predicted to decrease (Mote 2003, Mote et al. 2005, 

Nolin and Daly 2006), resulting in seasonal shifts to 

earlier spring conditions and a longer growing season.
72 Climate Change and Forest Biodiversity in Western Washington
Climate Change and Forest Biodiversity in Western Washington 73

Because of the high degree of topographic relief and 

the wide range of local conditions in mountainous 

environments, alpine and subalpine biodiversity is 

high, and habitat types are discontinuous and 

fragmented across the landscape. High-elevation 

habitats are expected to experience increased habitat 

fragmentation and increased competition from lower 

elevation species as a result of climate change 

(Walther et al. 2005). Conditions are expected to 

change more rapidly than alpine plant species will be 

able to adapt (Grabherr 2003), and plant community 

composition is likely to change as different species 

respond differently to changing conditions. In the 

forest tree vulnerability assessment described earlier in 

this report, several high-elevation tree species ranked 

among the most vulnerable to climate change. Among 

those species, subalpine fir and mountain hemlock are 

associated with subalpine habitat. They are important 

components of the patchy habitat structure of 

subalpine environments, and are commonly dominant 

species below the subalpine zone. In the case of 

mountain hemlock, habitat affinity was the greatest 

contributor to its high overall vulnerability score; for 

subalpine fir, insects and disease was the most 

influential factor. These results demonstrate some of 

the potential differences among species in relative 

vulnerability to climate change.

A review of coarse-scale climate envelope modeling or 

tree climate viability maps for high-elevation tree 

species may lead to the conclusion that climate change 

will force upward migration, and ultimately these 

species will reach the uppermost extent of habitable 

space and will have nowhere to go. 

However, the high degree of fine-scale 

microhabitat variability in mountain 

ecosystems may provide some localized 

protection from climate change influences 

for species with slow migration rates, 

although the prevalence of this “refugia” 

effect is uncertain (Randin et al. 2009). 

Relatively mobile species, such as those 

with light, wind-dispersed seeds, may be 

able to migrate locally to more hospitable 

locations, shifting to cooler, moister 

microhabitats or to more northerly aspects 

(Millar et al. 2007). Subalpine meadow 

habitat may decrease—conifer 

advancement into subalpine meadows is a 

documented impact of climate change, 

with treeline advancing unevenly upward 

into meadow sites that become more 

favorable to tree establishment (Holtmeier 

and Broll 2005, Millar et al. 2004, 

Peterson et al. 2002, Rochefort and 

Peterson 1996, Woodward et al. 1995, 

Zolbrod and Peterson 1999). 

Reductions in snowpack extent and 

duration may result in loss of habitat and 

increased risk of desiccation and freezing 

Subalpine habitat, Norse Peak Wilderness, Mt. Baker-Snoqualmie 

National Forest

Robin Shoal, USFS
74 Climate Change and Forest Biodiversity in Western Washington

for frost-sensitive plant species adapted to wintering in 

the stable, near-freezing conditions found under snow 

(Grabherr et al. 2010). Alpine and subalpine wetlands 

and stream headwaters may experience more 

pronounced with earlier spring peak flows and 

increased summer drought altering habitat for both 

plants and animals. 

An additional threat associated with projected climate 

change is the potential for increased native and nonnative insect and pathogen outbreaks and related 

disturbances (Dale et al. 2001). For example, recent 

warming trends resulted in range expansion and 

population outbreaks of mountain pine beetle 

(Dendroctonus ponderosae), a native bark beetle, that 

have led to widespread mortality in high-elevation 

pines (Logan et al. 2003, Williams and Leibhold 2002) 

and led to a short-term risk of increased fire intensity. 

In western Washington, whitebark pine, western white 

pine, and lodgepole pine are all associated with highelevation forests, and whitebark pine and lodgepole 

pine are often found in subalpine habitats. Fire 

frequency is expected to increase with future climate 

warming (Littell et al. 2009a, Westerling et al. 2006), 

and may be exacerbated in subalpine habitats by 

increased tree mortality from mountain pine beetle 

(Littell et al. 2009b). In contrast to the other two 

habitat types considered in this section, alpine and 

subalpine habitats in western Washington are 

relatively pristine in that they are generally free of 

direct human impacts beyond the developed ski areas, 

trail systems, and popular camping destinations. While 

dry grassland and wetland habitats are included in the 

Priority Habitats and Species List maintained by the 

Washington Department of Fish and Wildlife 

(WDFW), alpine and subalpine habitats are not, 

primarily because they are not considered to be 

directly threatened by human activities (Azerrad 

2010). However, these highest of habitats are not 

without anthropogenic stressors, including recreation 

pressure, air pollution, fire suppression, grazing, and 

non-native pathogens, plants, and animals.

Ecosystem Goods and Services

Alpine and subalpine habitats support a high level of 

both plant and animal biodiversity, and also serve as 

summer habitats for many species of wildlife, 

including migratory birds. They are important 

recreation areas, valued for their scenic views, 

wildlife, seasonal wildflower displays, and physical 

challenges. Recreation pressure is increasing in these 

areas as human populations grow, and as advances in 

technology make backcountry recreation more 

accessible. Snowpack conditions will continue to vary 

annually, but a trend toward later snow accumulation 

in fall and earlier snowmelt in spring is likely to 

extend the recreation season, allowing earlier trail 

access in the spring and more snow-free territory in 

late summer. This may result in an increase in highelevation recreation, which may place additional 

stresses on alpine and subalpine ecosystems, including 

sanitation issues and an increased risk of introduction 

and spread of non-native invasive plant species, 

particularly near heavily used areas such as water 

sources. 

Information Gaps

Site-specific management requires site-specific

information, but alpine and subalpine habitats are not 

well-mapped, due in part to difficulties of scale. Figure 

11 shows the modeled alpine and subalpine parkland 

vegetation zones from the current Forest Service 

vegetation zone map. However, this map 

representation cannot provide information about the 

locations and extent of the widely varied small-scale 

ecosystems that occur within the larger alpine and 

subalpine environments as a result of local factors—

factors that include geology, soils, aspect, slope, 

concavity, position on a hillside, proximity to 

permanent or seasonal snowfields, proximity to other 

vegetation, local drainage patterns, and exposure to 

sun and wind. These localized habitats include dry 

meadows, wet meadows, wetlands, seasonal ponds, 

lichen-covered rocks and cliffs, talus slopes, 

krummholz, shrub thickets, tree islands, and other 

small ecosystems (Malanson et al. 2007). 
Climate Change and Forest Biodiversity in Western Washington 75

Current climate modeling is limited to resolutions too 

coarse to be useful in complex high-elevation 

topography, and also misses these important smallscale landscape and habitat variations (Bachelet 

2010a). While models can predict generalized trends, 

local responses to climate change will vary (Malanson 

et al. 2007). Direct monitoring of climate-sensitive 

factors will provide better information for assessing 

alpine and subalpine responses to climate change. For 

instance, the duration and extent of annual snowpack 

can be tracked using existing aerial imagery and 

remote sensing. Changes in tree density and 

establishment in subalpine meadows can also be 

tracked using aerial imagery. Valuable information 

already exists in the form of historic photographs, both 

aerial and from known locations on the ground such as 

established viewpoints and fire lookout towers. Local 

temperature and precipitation data are available from 

the existing system of weather stations maintained by 

various agencies, such as the Western Regional 

Climate Center (www.wrcc.dri.edu/index.html). 

Consistent observation of these data, combined with a 

review of historical data, would offer clues as to which 

elements of alpine and subalpine habitats might be 

most vulnerable to the effects of climate change. Gaps 

in the network of weather stations could be identified 

and filled to provide a more complete picture of 

patterns of climate change in alpine and subalpine 

habitats. 

Also lacking are inventories of existing non-native 

invasive plant (noxious weed) infestations in highelevation environments.
76 Climate Change and Forest Biodiversity in Western Washington

NATIVE DRY GRASSLAND 

HABITATS

In western Washington, native dry grassland habitats 

occur in the Puget Lowlands and Willamette Valley 

Ecoregions (Chappell et al. 2001), which span the 

north-to-south length of the Puget Trough from the 

border with British Columbia to the Oregon border 

(fig. 12). Dry grassland habitats include native 

prairies, Oregon white oak woodlands, conifer 

savannas, and balds and herbaceous bluffs (Chappell 

2006, Chappell et al. 2001). Native prairies are found 

on glacial outwash and other well-drained soils, and 

are defined by the presence of certain diagnostic 

grasses, forbs, and sedges (Washington Department of 

Fish and Wildlife 2008). Oregon white oak woodlands 

are characterized by an open canopy dominated by oak 

and scattered conifers with an understory of grasses, 

forbs, and some shrubs. Conifer savannas are 

grasslands that support sparsely scattered conifers—

Douglas-fir and lodgepole pine but also ponderosa 

pine in a small portion of Pierce County (Chappell and 

Crawford 1997). Herbaceous balds and bluffs are 

usually relatively small, and occur on very dry, sloping 

sites with thin soils (Chappell 2006); they are 

dominated by grasses, lichens, forbs, and low-growing 

shrubs. The elevations at which these habitats occur 

are generally low— from sea level for coastal 

grasslands and herbaceous bluffs, to at least 700 ft 

(215 m) (the highest site reported by Peter and Shebitz 

[2006]) for oak woodlands and conifer savannas. 

Balds may occur at somewhat higher elevations 

(Chappell 2006).

Most South Puget Sound dry grassland habitats are 

susceptible to encroachment and eventual dominance 

by conifers (Chappell and Crawford 1997). While soil 

conditions that limit the growth of conifers explain the 

presence and persistence of some of these habitats, 

historically many of these grassland habitats were 

actively maintained by Native American burning 

(Peter and Shebitz 2006, Shebitz et al. 2009). Prairie 

habitats also occur on San Juan National Historic Park 

and Ebey’s Landing National Historic Reserve on 

Whidbey Island (Rochefort et al., n.d.). It is likely that 

some of these island grasslands persist as a result of 

limiting soil conditions and the prevailing dry climate 

(Rochefort 2010). 

Dry grassland habitats are the least extensive of the 

three habitat types considered in this report. The 

WNHP map representation of current oak and 

grassland habitats in the Puget Trough Ecoregion 

encompasses about 41,500 ac (16,800 ha), much of 

which is degraded. It is possible to estimate the 

potential historical extent of dry grassland habitats by 

mapping the soil types associated with these habitats. 

Historically, native grassland habitat was considerably 

more extensive. In the southern Puget Sound area, 

urban development, forest invasion, agriculture, and 

conversion to other land uses have reduced grassland 

habitat to about 10 percent of its original (preEuropean settlement) extent (Chappell et al. 2001, 

Crawford and Hall 1997). The range of Oregon white 

oak may also serve as a surrogate for the potential 

historical range of grassland habitat in western 

Washington (Thilenius 1968).

On National Forest System lands in western 

Washington, prairie remnants occur on the Olympic 

and possibly the Gifford Pinchot National Forests. The 

Gifford Pinchot sites are suspected to have once 

supported grassland habitat based on the presence of 

scattered vegetation plots containing Oregon white 

oak. The occurrence and extent of native grassland, 

historical or current, on the Mt. Baker-Snoqualmie 

National Forest is unknown.

The prairie remnants on the Olympic National Forest 

are in the southeast corner of the forest, adjacent to 

other savanna habitat under private ownership, and 

have been well-documented (Peter and Shebitz 2006). 

The forest initiated a 32-ac (13-ha) prairie restoration 

project in 1995. The project site, which had become 

covered by young Douglas-fir forest, was thinned in 

2001 and burned in 2003, with the intent to continue 

prescribed burning on a 3- to 5-year interval (Peter and 

Shebitz 2006). No further restoration activity has 

occurred, although vegetation on the site is 

periodically monitored. The nearby Forest Service 

Dennie Ahl tree seed orchard, which has been mown 

for decades and includes portions maintained in an 

open state, contains remnant populations of prairie-
Climate Change and Forest Biodiversity in Western Washington 77
78 Climate Change and Forest Biodiversity in Western Washington

associated species such as tough-leaf iris (Iris tenax), 

beargrass (Xenophyllum tenax), the native grasses 

California oatgrass (Danthonia californica) and 

poverty oatgrass (Danthonia spicata), and other dry 

grassland plant species. Roemer’s fescue (Festuca 

idahoensis var. roemerii) is suspected on the orchard 

site, but must be confirmed. Several vegetation plots in 

the same watershed contain Oregon white oak. There 

are also known examples of bald habitat on the 

Olympic National Forest, including areas in the 

Hamma Hamma and Dungeness watersheds.

On the Gifford Pinchot National Forest, Weigle Hill 

Botanical Special Interest Area is an Oregon white oak 

grassland that is proposed for RNA designation in the 

forest's 1990 Land and Resource Management Plan. 

The Chelatchie Prairie, on National Forest System 

land adjacent to the Mt. St. Helens National Volcanic 

Monument Headquarters, is an example of a remnant 

of at-risk native grassland that provides an opportunity 

for restoration of native prairie vegetation, as well as 

opportunities for partnership and public education.

There is a high level of interest in preserving and 

restoring native dry grassland habitats in western 

Washington. The Department of Defense Joint Base 

Lewis-McChord, The Nature Conservancy, the 

WADNR Natural Heritage Program, and several other 

agencies and organizations are actively managing and 

restoring native prairies and oak woodlands in the 

South Puget Sound area, and have developed a 

successful ecological fire program with specialized 

skill in the application of fire as a restoration tool 

(McKinley 2010). Restoration activities have taken 

place at some of the National Park Service prairie sites 

in the San Juan Islands and at Ebey’s Landing 

National Historic Preserve on Whidbey Island, where 

the emphasis is to restore habitat for the federally 

threatened golden paintbrush (Castilleja levisecta). 

National Park Service is developing a protocol to 

monitor prairie vegetation (Rochefort et al., n.d.).

Vulnerability

In western Washington, dry 

grassland habitats have been 

drastically reduced by human land 

use including agriculture and 

development. With European 

settlement came the cessation of 

systematic burning by Native 

American peoples, and many former 

prairies are now covered by conifer 

forests that regenerated in the 

absence of fire. Many dry grassland 

remnants are heavily degraded. 

Crawford and Hall (1997) 

conservatively estimate a loss of 

over 91 percent of the pre-settlement 

areal extent of grassland habitat, 

with less than 3 percent of the 

original habitat still in good 

condition. Grassland habitats have been invaded by 

non-native species such as Scot’s broom (Cytisus 

scoparius), non-native blackberries (Rubus spp.), and a 

wide range of non-native grasses including the highly 

invasive pasture grass tall oatgrass (Arrhenatherum

elatius) (Chappell et al. 2001; Dunwiddie et al. 2006; 

Rochefort et al., n.d.). Dry grasslands in western 

Washington are part of a larger complex of dry 

grassland ecosystems of the Willamette Valley– Puget 

Trough– Georgia Basin ecoregion, and are ranked 

among the most endangered ecosystems in the United 

Oak savanna, Joint Base Lewis-McChord, Washington

David Peter, USFS
Climate Change and Forest Biodiversity in Western Washington 79

States (Noss et al. 1995). The warmer, drier summer 

conditions predicted for western Washington are likely 

to exacerbate existing stressors, particularly the 

presence and continued spread of invasive grasses and 

other plant species. Because intact native dry grassland 

habitats in western Washington have become so rare, 

and because many of their remnants are in poor 

condition, it may be difficult to separate recent climate 

effects from the dramatic changes that these habitats 

have undergone during the 20th century. Given 

predictions of warmer and drier summer conditions 

and increased fire frequency that will ultimately favor 

grasses over trees (Bachelet 2010b, Woodward et al. 

2004), projected climate changes, combined with 

ongoing restoration efforts, may benefit dry grassland 

ecosystems in western Washington. If that is the case, 

early identification and active conservation and 

management of these areas may set the groundwork 

for these habitats to thrive, adapt, and expand as 

conditions change.

Ecosystem Goods and Services

Western Washington native grasslands are of great 

cultural importance for many Native American tribes 

who actively managed these habitats to enhance 

grazing opportunities for deer and elk, for the 

production of food such as bulbs of the camas lily 

(Camassia quamash), and for plant materials such as 

beargrass (Shebitz et al. 2009). In addition to 

providing habitat for many plant and animal species 

not found in other western Washington ecosystems, 

ecological goods and services associated with native 

dry grassland habitats include erosion control, flood 

control, fire resilience, and recreation. Native 

grasslands also are highly efficient at sequestering and 

storing atmospheric carbon (Bachelet 2010b, Neely et 

al. 2009). They provide important seasonal habitat for 

migratory birds (Altman 2000), and are popular 

birdwatching and hunting destinations. 

Information Gaps

Other than the work of Peter and Shebitz (2006) and 

Shebitz et al. (2009), little is known about the 

historical extent of dry grassland habitat on National 

Forest System lands in western Washington. Data 

from vegetation inventories such as the Forest 

Service’s western Washington Area Ecology database 

and the Forest Inventory and Analysis (FIA) program 

provide clues to current vegetation; all occurrences of 

Oregon white oak are mapped in appendix A. 

However, both these vegetation databases were 

developed primarily to identify and track conditions in 

coniferous forest stands, and thus they do not well 

represent Oregon white oak stands, which are usually 

classified as non-forest land owing to their low 

densities. Additionally, most Oregon white oak 

woodlands and grasslands that were once maintained 

by anthropogenic fire were encroached upon by 

conifer forests before these inventories began. A 

review of historical data, including herbarium records, 

historical maps and photographs, and tribal history, 

would provide additional information about the 

historical extent and composition of dry grasslands on 

lands now managed by the Forest Service. Caplow and 

Miller (2004) performed a similar review to identify 

historical prairie sites in southwestern Washington.
80 Climate Change and Forest Biodiversity in Western Washington

WETLANDS

Wetlands occur in places on the landscape where 

groundwater, surface water, or precipitation collects 

and persists long enough for aquatic processes and 

water-dependent communities to develop. Wetlands, 

which are relatively shallow, are distinct from 

deepwater habitats such as lakes, rivers, and oceans, 

which are permanently flooded lands where surface 

water is deep enough to provide a fully aquatic 

environment in which “water, rather than air, is the 

principal medium within which the dominant 

organisms live” (Cowardin et al. 1979).

The term wetlands encompasses a broad range of 

environments. Wetlands may be associated with 

deepwater habitats, such as the fringe of emergent 

vegetation surrounding a lake or pond, or with riparian 

settings. They may be tiny or extensive, forested or 

non-forested, freshwater or marine. Some wetlands 

contain standing or flowing water year-round; some 

are tidal; some are seasonal; and some are ephemeral, 

noticeably wet only after heavy precipitation events.

Wetlands occur throughout western Washington, at all 

elevations. The wetlands distribution represented in 

figure 13 is from the National Wetland Inventory, 

created by the U.S. Fish and Wildlife Service 

(http://www.fws.gov/wetlands/data/). In this 

representation there are approximately 238,000 ac 

(96,360 ha) of estuarine and marine wetlands, and 

approximately 367,000 ac (148,600 ha) of varied 

freshwater wetlands and ponds. Lakes and rivers cover 

approximately 223,000 ac (90,300 ha).

Among the botanists and ecologists contacted during 

the research for this report (see list in 

Acknowledgments section), concern about wetland 

vulnerability to climate change was stratified by 

wetland class. All wetland types were considered 

vulnerable to climate change, but bogs, fens, wet 

meadows, isolated ponds, and wetlands associated 

with headwater streams and alpine ecosystems were of 

consistently greater concern than wetlands directly 

associated with rivers or lakes. This stratification of 

concern is reflected in the scientific literature on 

freshwater wetlands and climate change, as discussed 

below.

The Canadian Wetland Classification System (CWCS) 

identifies five classes of wetlands: bogs, fens, swamps, 

marshes, and shallow open water. All five wetland 

classes occur in western Washington. 

• Bogs and fens are both characterized by 

organic soils, primarily derived from mosses 

of the genus Sphagnum. Bogs have high water 

tables and acid-tolerant vegetation. While 

bogs may receive water from a variety of 

sources, there are no significant inflows or 

outflows. Fens, which also have organic soils, 

depend on groundwater for their primary 

water source. This sets fens apart from the 

other classes, which generally receive water 

inputs from surface water as well as ground 

water. 

• Swamps are forested wetlands, generally with 

mineral soils but often with some decomposed 

woody organic material in the substrate. 

Swamps are associated with streams or other 

water bodies, and usually have some water 

movement through them. While swamps are 

wooded, marshes are characterized by 

emergent herbaceous vegetation. 

• Marshes generally have mineral soils and may 

experience wide fluctuations in water levels. 

In the Canadian classification system, wet 

meadows are a type of marsh. 

WETLAND CLASSIFICATION

The wetland classification systems used by 

botanists and ecologists contacted for this project 

and by the literature cited in this section vary. The 

Canadian Wetland Classification System (CWCS) 

(National Wetlands Working Group 1997) was the 

most frequently used system among the 

specialists contacted. For consistency, the 

discussion below generally follows the CWCS 

classifications when specific wetland types are 

mentioned.
Climate Change and Forest Biodiversity in Western Washington 81
82 Climate Change and Forest Biodiversity in Western Washington

• Shallow open waters (ponds) are small bodies 

of standing or gently flowing water that 

represent a transitional stage between lakes

and marshes. They are usually connected to 

sources of groundwater and receive additional 

input from surface water and precipitation. 

Among the many examples of wetlands in western 

Washington are the mid-elevation headwater wetland 

and wet meadow complexes on the Olympic National 

Forest, which may be in relatively pristine condition 

and could serve as potential reference sites for 

monitoring long-term climate change effects. On the 

Mt. Baker-Snoqualmie National Forest, the wetlands 

associated with Lake Isabel are home to rare wetland 

plant species at the southern edges of their ranges.

Vulnerability 

Wetlands of all types have a long history of being 

directly and indirectly degraded by human activity. 

Existing stressors include pollution, logging, grazing, 

land conversion to agriculture or housing, 

unauthorized motorized recreation, and anthropogenic 

disruptions to hydrology on many scales, including 

water diversion, roads, ditches, irrigation, flood 

control structures, and trapping or removal of beavers.

Wetlands also are susceptible to invasion by 

aggressive non-native plants, such as knotweed species 

(Polygonum spp.), reed canary grass (Phalarus 

arundinaceae), and competitive native species such as 

rose spiraea (Spiraea douglasii).

The vulnerability of wetlands to climate change 

depends primarily on their water source (Winter 

2000), which may be precipitation, snowmelt, surface 

water (streams or runoff), ground water, or a 

combination of these sources. The size of the 

upgradient watershed is of great importance, as is the 

wetland’s position in the watershed. Potential impacts 

range from changes in plant community structure and 

composition to changes in ecological function, and the 

results range from wetland loss to enhancement 

(Burkett and Kusler 2000).

Increased winter precipitation, especially precipitation 

that falls as rain rather than snow, may cause more 

frequent winter flooding and full inundation. In the 

summer, reduced precipitation may reduce water 

availability, while increased summer temperatures 

may simultaneously speed evaporation from wetlands 

and from their water sources, resulting in more 

extreme summer drying (U.S. Congress, Office of 

Technology Assessment 1993). In western 

Washington, the overall trend toward warming, with 

drier summers and wetter winters, may therefore be 

expressed in many freshwater wetlands by more 

pronounced seasonal extremes in water levels, 

particularly in the wetland types with greater 

dependence on precipitation.

High-elevation alpine and subalpine wetlands are 

extremely vulnerable to climate change because their 

contributing ground and surface watersheds are very 

small. These wetlands have small catchment basins 

and depend almost entirely on snowmelt in the forms 

of localized groundwater, surface water, or direct 

input. Earlier snowmelt and drier summers may result 

in earlier spring inundation and more summer drying. 

Plants and animals dependent on these wetlands will 

need to be able to adapt their lifecycles to these shifts 

in timing, or migrate elsewhere. Migration 

Wetland, Three Peaks Botanical Area, Olympic 

National Forest

Cheryl Bartlett, USFS
Climate Change and Forest Biodiversity in Western Washington 83

opportunities may be extremely restricted in 

fragmented mountainous terrain, and even small 

degrees of warming may eliminate populations of 

“relic” species currently resident in alpine wetlands 

(Burkett and Kusler 2000).

Bogs and fens are peat-forming wetlands, and share a 

well-developed organic substrate layer (Zoltai and Vitt 

1995). By definition, fens depend primarily on 

groundwater, while bogs may have a mix of water 

sources. Stable groundwater, surface water, or 

precipitation inputs are crucial for maintaining the 

integrity of these organic soils (Rocchio and Crawford 

2009). Peatlands are very effective at carbon storage, 

but become emitters of both carbon dioxide and 

methane if they dry or drain (Burkett and Kusler 

2000).

Marshes and swamps differ from bogs and fens in that 

they have non-organic (mineral) substrates and 

generally greater water movement within and through 

them. Marshes and swamps may receive water from 

multiple sources. Marsh and swamp vegetation is 

adapted to a wide range of seasonal water level 

fluctuation (Zoltai and Vitt 1995). Because of this, 

marshes and swamps are considered less vulnerable to 

effects of climate change than fens or bogs. However, 

they are likely to experience greater seasonal extremes 

than they have historically, and may expand or 

contract in response, depending on their hydrologic 

setting (Burkett and Kusler 2000). 

Isolated wetlands that depend primarily on 

precipitation and runoff for their water source are 

highly vulnerable to climate change (Winter 2000). In 

western Washington this group includes vernal ponds, 

wooded kettles, some wet meadows, and other 

seasonally wet areas that occur in small depressions on 

the landscape. These habitats are often crucial in the 

reproductive lifecycles of frogs and other amphibians. 

Climate change may pose a serious challenge to the 

health and persistence of many amphibian species 

(Corn 2005). Early summer drying of these wetlands 

may expose amphibian eggs to desiccation, and higher 

water temperatures may reduce amphibian immunity 

to pathogens (Raffel et al. 2006). 

Wetlands associated with rivers and lakes in valley 

bottoms are likely to be relatively less exposed to 

effects of climate change, because they have larger 

catch basins and more sustained water input from both 

groundwater and surface water sources. However, 

wetlands located on terraces above the valley bottom 

may be more vulnerable if they are fed only by 

localized groundwater flow (Winter 2000). 

Finally, coastal and estuarine wetlands are highly 

vulnerable to sea level rise if they have no ability to 

migrate inland, or if the rate of sediment accretion lags 

behind the rate of sea level rise (Burkett and Kusler 

2000). Water quality in coastal and estuarine wetlands 

is expected to decline as a result of decreased summer 

stream flows and higher water temperatures (Poff et al. 

2002). Rising sea levels may inundate coastal 

wetlands, and introduce brackish water into freshwater 

tidal areas and near-shore wetlands (U.S. Congress, 

Office of Technology Assessment 1993).

Ecosystem Goods and Services

In addition to having high plant and animal 

biodiversity, wetlands perform valuable functions that 

can be grouped into three categories: functions that 

improve water quality such as filtration, removal of 

pollution and nutrients, and the slowing and settling of 

sediment; functions that affect the water regime in a 

watershed such as flood storage and storm surge 

protection; and functions that provide habitat for plants 

and animals (Sheldon et al. 2005). Wetlands also 

provide direct goods and services in western 

Washington in the form of food production (i.e., fish, 

shellfish, cranberries), and recreation (i.e., boating, 

hunting, bird watching).

Information Gaps

The National Wetland Inventory (NWI, depicted in 

fig. 13) is currently the best mapped inventory of 

wetlands in western Washington. NWI maps are 

strongest at identifying open-water wetlands 

associated with rivers and lakes, but omit many small, 
84 Climate Change and Forest Biodiversity in Western Washington

vegetated wetlands, including wet meadows, bogs, 

fens, some marshes, and most forested wetlands. Other 

than NWI, wetlands on public lands have not been 

consistently inventoried, mapped, or classified, 

although some information is generally recorded

informally when an individual wetland is encountered 

during other management activities. 

Identifying which wetlands are naturally more resilient 

to climate change and which are more vulnerable 

would help in prioritizing wetland habitats for 

monitoring, active conservation, and restoration.
Climate Change and Forest Biodiversity in Western Washington 85

PART 3: RECOMMENDATIONS
86 Climate Change and Forest Biodiversity in Western Washington

RECOMMENDATIONS

The recommendations developed during the course of 

this project fall into three categories:

1. Learn about and track changes in plant 

communities as the climate changes. Collect 

baseline data where needed. Monitor the 

impacts of a warming climate on the 

distribution and health of forest tree species 

and non-forested habitats. Look for triggers, 

such as an increase in the frequency of largescale disturbance, that will indicate a need to 

change our management approach.

2. Maintain and increase biodiversity and 

increase resiliency. Focus on increasing stand 

diversity of native forest trees through 

thinning and planting. Initiate restoration 

activities in priority non-forested habitats. 

Increase disease resistance. Preserve genetic 

diversity, especially of isolated populations, 

and implement ex situ gene conservation 

where appropriate.

3. Prepare for the future. Given uncertainty 

about how climate changes will unfold, a 

number of future scenarios are possible. Select 

activities that will work under a variety of 

scenarios including a potential increase in 

disturbances such as fires, wind storms, and 

floods, which could be followed by greater 

spread of invasive plant species.

Recommendations, and action items listed in tables 28 

through 32, are focused on present conditions with the 

assumption that existing policy and law will continue 

to guide land managers over the next few years.

ACTION ITEMS

Based on the findings of our analysis, we created 

action items for all western Washington national 

forests, as well as action items specific to each of the 

three national forests that were the focus of this 

project. Action items for forest trees and non-forested 

habitats are listed separately within each of the three 

recommendation categories.

Historically, management on the three western 

Washington national forests has emphasized tree

species, forest stands, and, more recently, riparian 

areas. As a result, little information exists about the 

location and condition of non-forested habitats on 

these national forests. Much of the work needed to 

understand the vulnerabilities and potential responses 

of these habitats to projected trends in climate change 

is the collection of baseline information about their 

location, historical extent, and current condition. 

Because of this, the action items for non-forested 

habitats are more general than the action items for 

forest tree species.

There are four recurring themes in the recommended 

action items for non-forested habitats:

• Locate, map, describe, and assess the 

condition of these habitat types;

• Select instances of these habitat types on 

which to focus monitoring and/or restoration 

efforts; 

• Identify and monitor potential vulnerabilities 

to or indicators of climate change; and

• Manage to maintain or restore resilience to 

climate change.

Action items for non-forested habitats are intended to 

contribute to management’s preparedness for adapting 

to climate change effects on these habitats. Many of

the action items can be accomplished through 

coordination or partnership with existing organizations 

or established programs. Some of these resources are 

listed following the action item tables. It is 

recommended that forests begin by using remote 

assessment—GIS, aerial photography, local 

knowledge, existing datasets, etc.—to develop 
Climate Change and Forest Biodiversity in Western Washington 87

preliminary priorities for more intensive inventories, 

field assessments, and restoration and adaptation 

planning. Priorities are likely to vary among forests, 

and may be based on habitat type, wildlife presence, or 

other forest-level considerations. 

TOP 10 PRIORITY ACTION ITEMS

As a focus for planning and accomplishment, the top 

10 action items (table 28) were selected based on the 

following criteria:

• Items reflect the results of vulnerability 

assessments of forest trees and non-forested 

habitats.

• Items benefit the three national forests in 

western Washington.

• Items can be accomplished in 5 years.

• Items reflect new efforts.

• Where possible, items combine activities 

under common goals or themes.

• Items provide opportunities for partnership 

with the National Park Service, WADNR, and 

other land managers.

WASHINGTON STATE’S CLIMATE CHANGE 

WORK

The Washington State Department of Ecology 

formed four topic advisory groups in 2010 to 

assist with development of the state’s climate 

change response strategy. The Natural 

Resources: Working Lands and Waters topic 

advisory group produced a set of 

recommendations for genetic preservation and 

development in adapting to climate change 

(NRWLW 2011). Several of the action items in 

this report are closely aligned with the 

recommendations of the topic advisory group; 

these action items are marked with an asterisk in 

the tables that follow.

 

 

 

GUIDE TO ACTION ITEM TABLES

Tables 28 through 32 list all of the action items created for the national forests of 

western Washington.

• Table 28 lists the top 10 priority action items that apply to all three of the 

national forests of western Washington.

• Table 29 is a comprehensive list of all the action items for the three national 

forests. Each item is labeled with the initials of the national forest(s) to which 

it applies.

• Tables 30 though 32 contain forest-specific lists of action items for the three 

national forests of western Washington.
88 Climate Change and Forest Biodiversity in Western Washington

Table 28. Top 10 Priority Action Items

Forest Trees

 1B Assess stand health and regeneration of subalpine fir, mountain hemlock, and Alaska yellowcedar, the high-elevation tree species that were found to be most at risk based on the 

vulnerability assessment. This will establish baseline information that can be used to track 

changes over time and form the basis for a conservation and monitoring plan.

 1D* Develop a pilot program to monitor vegetative and reproductive phenology in seed orchards. 

 2G* Develop a pilot project to plant blister rust resistant western white pine in gaps or openings 

created in pre-commercially thinned stands and young-growth stands. 

 3A* Partner with other land managers in western Washington to create a virtual cooperative tree 

seed bank to facilitate reforestation after large-scale disturbances such as fire or insect 

outbreaks. 

 3B* 

- 3F

Maintain an inventory of high-quality seed for tree species that are likely to be needed over the 

next 20 years. Place a priority on species that can be planted after disturbance. Assess the 

viability of stored seed, discard non-viable seed, and make new and replacement collections as 

needed. 

Non-Forested Habitats

 1G

1H

1I

For alpine and subalpine meadows:

• Map and inventory.

• Review historic aerial photography to identify potential trends in tree establishment in 

meadows and tree line change over time. 

• Select individual meadows for monitoring and initiate photo-point monitoring and/or 

periodic aerial photography of selected alpine meadows to track changes in tree 

establishment.

 1K

1L

For native dry grassland, Oregon white oak woodlands and savannas, and balds:

• Map and inventory existing occurrences.

• Use soil maps, aerial photos, and historical information to identify potential historical 

extent of these habitats on national forest lands.

 1O

1P

1R

For wetlands:

• Initiate a systematic inventory program to locate and describe wetlands and assess 

their condition. 

• Use historic information and aerial photography to identify changes to individual 

wetlands over time. 

• Initiate on-going photo-point monitoring of selected wetlands.

• Using wetland inventory results, select at-risk wetlands for conservation and restoration.

 1Q Collect foundation seed and initiate seed increase as needed of native grassland and wetland 

plant species. Target both rare and “workhorse” species for ex situ gene conservation and 

restoration purposes.

 3G

3I

For all three habitat types, continue to inventory, prevent, and treat non-native invasive plant 

species

Note: Item numbers correspond to the action items described in detail in the following tables. In some cases items were 

combined.

* Action item is aligned with a similar recommendation by the Washington Department of Ecology’s Natural Resources Topic 

Advisory Group adaptation strategy for genetic preservation and development.
Climate Change and Forest Biodiversity in Western Washington 89

Table 29. Action Items for All Western Washington National Forests

Forest Trees

No. Forest Action

1. Learn about and track changes in plant communities as the climate changes

1A GP 

MBS 

OLY

CONTINUE AND EXPAND THE SURVEY AND MAPPING PROGRAM FOR WHITEBARK PINE, WITH THE 

PARTICIPATION BY ALL LAND MANAGEMENT AGENCIES WITH WHITEBARK PINE HABITAT IN WASHINGTON 

STATE. This effort should include a refinement of the existing state-wide GIS layer of whitebark 

pine occurrences. Readily accessible data on whitebark pine’s present distribution is essential for 

monitoring and managing the species under climate change and pathogen threats.

1B GP 

MBS 

OLY

DEVELOP A CONSERVATION AND MONITORING PLAN FOR THE THREE HIGH ELEVATION TREE SPECIES THAT 

RANKED HIGHEST IN VULNERABILITY TO CLIMATE CHANGE BUT THAT HAVE NOT BEEN MANAGED IN THE PAST:

SUBALPINE FIR, MOUNTAIN HEMLOCK, AND ALASKA YELLOW-CEDAR.

1C GP 

MBS 

OLY

CATALOG INFORMATION ON ALL KNOWN OFF-SITE FOREST PLANTATIONS ON THE NATIONAL FORESTS, AND 

CREATE A GIS LAYER OF THESE PLANTATIONS. In the past, seed sources used for reforestation were 

sometimes not well matched to the seed zones in which the seedlings were planted. Some of 

these off-site plantations may now provide valuable information on response of trees to climatic 

stressors comparable to those predicted to occur under future climate change scenarios.

1D* OLY MONITOR VEGETATIVE AND REPRODUCTIVE PHENOLOGY IN SEED ORCHARDS. Timing of phenology is 

closely linked to climate, and collecting data on annual phenology and microclimate will allow us 

to determine if there are trends in how trees are responding to annual climate variation. A pilot 

program will be established in 2011 in the Dennie Ahl seed orchard to develop protocols for 

monitoring phenology in western white pine and Pacific silver fir in partnership with Dr. Constance 

Harrington of PNW Research Station and the WADNR. These two species were chosen because: 

1) Pacific silver fir had the highest overall vulnerability in our index, 2) these species are present 

in the orchard, and 3) Douglas-fir and western red cedar phenology monitoring has already been 

implemented at the WADNR Meridian Seed Orchard.

1E GP 

OLY

MEASURE POPULATION GENETICS OF GOLDEN CHINQUAPIN. Golden chinquapin is one of the four Group 

3 species (table 2) and is listed by the US Forest Service as a sensitive species in Washington; 

however, nothing is known about the genetics of this species (table 18). To develop a 

conservation plan for golden chinquapin in Washington, it is necessary to know how genetically 

similar these populations are to the core of the species’ range in California and Oregon. In 2010, 

leaf samples were collected for genetic analysis from the two golden chinquapin populations in 

Washington. Additional leaf samples will be collected from other parts of the species’ range to 

determine the genetic diversity and population structure of: 1) the north-south extent of the 

species’ distribution, and 2) the Washington populations. This project includes partnerships with 

the Washington Department of Natural Resources (WADNR) (chinquapin is present on WADNR 

land on the Olympic Peninsula) and USFS National Forest Genetic Electrophoresis Lab (NFGEL) 

where genetic analysis will be performed.

1F OLY ASSESS GENETIC VARIATION AND POPULATION STRUCTURE IN THREE SPECIES WITH SMALL, ISOLATED 

DISJUNCT POPULATIONS: ENGELMANN SPRUCE ON THE OLYMPIC PENINSULA AND NOBLE FIR AND PACIFIC 

SILVER FIR IN THE WILLAPA HILLS. These disjunct populations, as well as a range of populations from 

across the full distribution of the species, should be sampled for genetic analysis. These projects 

would include partnerships with the Olympic National Park, WADNR, and the USDA NFGEL, 

where genetic analysis would be performed. Assessing genetic variation and population structure 
90 Climate Change and Forest Biodiversity in Western Washington

Forest Trees

No. Forest Action

of species with disjunct populations is necessary to determine if these populations are genetically 

distinct from populations within the contiguous part of the species’ distribution. This information is 

important because these disjunct populations could end up as refugia under predicted climate 

change scenarios or, conversely, they might be more severely impacted because lack of gene 

flow would limit opportunities for immigration of more highly adapted genes from other 

populations. This lack of gene flow could limit their adaptive genetic variation. In either case, it will 

be critical to know whether these populations are genetically distinct as this would lead to 

restrictions on the movement of seed both into and out of them. 

2. Maintain and enhance biodiversity and increase resilience

2A GP 

MBS 

OLY

CONTINUE THE NATIONAL FORESTS’ THINNING PROGRAMS. These programs achieve: 1) promotion of 

greater biodiversity by increasing the proportion of less abundant conifer and hardwood tree 

species, 2) the development of understory vegetation, 3) enhancement of the habitat value 

provided by forest stands, and 4) increased stand resistance and resilience to disturbance and 

environmental stressors.

2B* GP 

MBS 

OLY

CONTINUE TO INCLUDE A VARIETY OF TREE SPECIES IN PLANTING PRESCRIPTIONS, WITH AN EMPHASIS ON 

UNDER-REPRESENTED TREE SPECIES.

2C OLY PRODUCE AN INTERAGENCY PLAN, INVOLVING THE FOREST SERVICE AND NATIONAL PARK SERVICE, TO MAP 

OCCURRENCES AND EVALUATE MANAGEMENT OPTIONS FOR ROCKY MOUNTAIN JUNIPER ON THE OLYMPIC 

PENINSULA. One product of this plan should be a GIS layer of all known occurrences of this 

species on the Peninsula. Recent genetic research indicates that the Olympic Peninsula and 

Puget Sound Region populations of Rocky Mountain juniper represent a unique species, seaside 

juniper (Juniperus maritima R. P. Adams) (Adams 2007, Adams et al. 2010). Management of this 

species should be re-evaluated in the context of this new information and the potential effects of 

climate change on the species’ habitat. Additional genetic analyses should be conducted, if 

determined necessary, to verify the classification of this species.

2D OLY DEVELOP A PARTNERSHIP BETWEEN THE FOREST SERVICE, WADNR, AND PRIVATE LANDOWNERS TO MAP,

CONSERVE, AND RESTORE GOLDEN CHINQUAPIN ON THE OLYMPIC PENINSULA. Golden chinquapin is the 

only Washington tree species currently listed by the Interagency Special Status / Sensitive 

Species Program (USDA 2010c). This effort should include the creation of a GIS layer 

documenting locations of golden chinquapin on the Olympic Peninsula. These disjunct Olympic 

Peninsula populations represent the northernmost occurrence of the species and may be 

genetically different from populations in the contiguous portion of the species’ range (see item 

1E). The Olympic Peninsula populations therefore have the potential to contain adaptive genetic 

variation not present elsewhere in the range of golden chinquapin.

2E OLY IN A COLLABORATIVE EFFORT BETWEEN OLYMPIC NATIONAL FOREST AND OLYMPIC NATIONAL PARK, MAP 

OCCURRENCES OF ENGELMANN SPRUCE ON THE OLYMPIC PENINSULA. Engelmann spruce occurs in at 

least one small, disjunct population on the Olympic Peninsula. This population is potentially 

important for the adaptive genetic variation that it may contain. This collaborative effort should 

include field verification of several other reported but unconfirmed occurrences of this species on 

the Olympic Peninsula (see map in appendix A).
Climate Change and Forest Biodiversity in Western Washington 91

Forest Trees

No. Forest Action

2F GP CONTINUE TO ACTIVELY MANAGE GOLDEN CHINQUAPIN SITES TO PROMOTE GROWTH AND SURVIVAL OF THE 

SPECIES. As with the Olympic Peninsula populations, these disjunct populations may differ 

genetically from those in the contiguous portion of the species’ range and therefore may contain 

unique adaptive genetic variation.

2G* OLY DEVELOP A PILOT PROJECT TO PLANT BLISTER RUST RESISTANT WESTERN WHITE PINE IN GAPS OR OPENINGS 

CREATED IN PRE-COMMERCIALLY THINNED STANDS AND YOUNG-GROWTH STANDS. Planting also could be 

implemented in older young-growth stands in natural openings created by wind and root rot 

pockets with low quantities of competing vegetation.

2H* OLY EXPAND GENE CONSERVATION COLLECTIONS. Seed from rare species and disjunct populations should 

be collected for long-term ex situ gene conservation. These efforts are already under way for 

whitebark pine, but to-date no collections have been made for other species. Seed should be 

collected and sent to the USDA ARS National Center for Germplasm Preservation in Ft. Collins, 

CO for western Washington populations of Rocky Mountain juniper, golden chinquapin, 

Engelmann spruce, noble fir (from the Willapa Hills), Pacific silver fir (from the Willapa Hills), and 

ponderosa pine. This project would include partnerships with Olympic National Park, WADNR, 

and Dept. of Defense Joint Base Lewis-McChord.

3. Prepare for the future

3A* GP 

MBS 

OLY

PARTNER WITH OTHER LAND MANAGERS IN WESTERN WASHINGTON TO CREATE A VIRTUAL COOPERATIVE 

TREE SEED BANK. This would increase the likelihood that appropriate seed will be available for 

reforestation after large-scale disturbances such as fire or insect outbreaks. Landowners can 

maintain their own seed inventories, but enter in cooperative agreements to share seed in the 

event of a major disturbance. As a first step, Forest Service personnel should form a partnership 

with silviculturists, geneticists, and seed managers from the WADNR and the National Park 

Service and others to develop an approach for sharing information and seed.

3B* GP 

MBS 

OLY

MAINTAIN AN INVENTORY OF HIGH-QUALITY SEED FOR TREE SPECIES THAT ARE LIKELY TO BE NEEDED OVER 

THE NEXT 20 YEARS. Place a priority on species that can be planted after disturbance. Accomplish 

this through the following steps:

• Assess the viability of seed stored at the Forest Service storage facility at JH Stone Nursery

• Retest viability as needed

• Discard non-viable seed

• Update Seed Procurement Plans to include new and replacement collections

3C OLY MAINTAIN THE DENNIE AHL SEED ORCHARD WHICH SERVES AS A GENE CONSERVATION AREA AND IS THE 

FOREST’S MOST EFFICIENT SOURCE OF HIGH QUALITY TREE SEED FOR DOUGLAS-FIR, PACIFIC SILVER FIR,

AND RUST RESISTANT WESTERN WHITE PINE.

3D GP MAINTAIN THE WHITE SALMON, PLANTING CREEK, COYOTE, CISPUS, AND FRENCH BUTTE SEED ORCHARDS 

WHICH SERVE AS GENE CONSERVATION AREAS AND ARE THE FOREST’S MOST EFFICIENT SOURCE OF HIGH 

QUALITY TREE SEED FOR DOUGLAS-FIR, NOBLE FIR AND RUST RESISTANT WESTERN WHITE PINE.

3E MBS MAINTAIN THE MCCULLOUGH SEED ORCHARD WHICH SERVES AS GENE CONSERVATION AREAS AND IS THE 

FOREST’S MOST EFFICIENT SOURCE OF HIGH QUALITY TREE SEED FOR DOUGLAS-FIR, NOBLE FIR AND RUST 

RESISTANT WESTERN WHITE PINE.
92 Climate Change and Forest Biodiversity in Western Washington

Forest Trees

No. Forest Action

3F GP 

MBS 

OLY

ASSESS SEED VIABILITY OF INDIVIDUAL SELECTED TREE LOTS IN STORAGE. The three national forests in 

western Washington have over 5,000 single tree seedlots from selected trees in storage at the 

Dorena Genetic Resources Center (table 25). Many of these seedlots have been in storage for 

one or more decades and their viability is unknown. Viability testing is expensive and time 

consuming so it is impractical to test every seed lot. Geneticists and silviculturists should jointly 

develop a prioritized list of seedlots for viability testing. Priority for testing should be based on 

several factors, including: 1) vulnerability rank of the species, 2) initial (or subsequent) viability 

test results, 3) age of seed, and 4) amount of seed available. Top priority should be given to 

highly vulnerable species, seedlots with low initial viability, older seed, and lots with a large 

amount of seed available. 

Non-Forested Habitats

No. Forest Action

1. Learn about and track changes in plant communities as the climate changes

Alpine and subalpine

1G GP 

MBS 

OLY

MAP AND INVENTORY ALPINE AND SUBALPINE MEADOWS. Select individual meadows for monitoring.

1H GP 

MBS 

OLY

REVIEW HISTORIC AERIAL PHOTOGRAPHY TO IDENTIFY POTENTIAL TRENDS IN TREE ESTABLISHMENT IN 

MEADOWS AND TREE LINE CHANGE OVER TIME. Initiate photo-point monitoring and/or periodic aerial 

photography of selected alpine meadows to track changes in tree establishment.

1I GP 

MBS 

OLY

IDENTIFY TARGET ALPINE AND SUBALPINE FORB, SHRUB, AND/OR TREES SPECIES BASED ON CRITERIA SUCH 

AS KEYSTONE FUNCTION, KNOWN VULNERABILITY, OR HABITAT INDICATOR STATUS, AND FORMALIZE A 

PROGRAM FOR MONITORING PHENOLOGY OF THESE SPECIES.

1J GP 

MBS 

OLY

IDENTIFY AND MONITOR KEY HIGH-ELEVATION WILDLIFE SPECIES (I.E., PIKA, OLYMPIC MARMOT, CLARK’S 

NUTCRACKER, POLLINATORS).

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

1K GP 

MBS 

OLY

MAP AND INVENTORY EXISTING OCCURRENCES OF NATIVE DRY GRASSLANDS, BALDS, AND OREGON WHITE 

OAK SAVANNAS AND WOODLANDS.

1L GP 

MBS 

OLY

USE SOIL MAPS, AERIAL PHOTOS, AND HISTORICAL INFORMATION TO IDENTIFY POTENTIAL HISTORICAL 

EXTENT OF THESE HABITATS ON NATIONAL FOREST LANDS.
Climate Change and Forest Biodiversity in Western Washington 93

Non-Forested Habitats

No. Forest Action

1M GP CONDUCT FIELD RECONNAISSANCE OF FIA AND ECOLOGY PLOTS CONTAINING OREGON WHITE OAK, AND 

IDENTIFY HABITAT TYPE ASSOCIATED WITH THESE OCCURRENCES. These sites are primarily in the 

southeast portion of the forest, with a single plot near Highway 12 farther north.

1N MBS MAP, INVENTORY, AND ASSESS CONDITION OF EXISTING OCCURRENCES OF BALDS. One example of this 

habitat is the Greenwater-George Creek Overlook. Because of the generally higher elevations of 

the Mt. Baker-Snoqualmie National Forest, it is unlikely that there is any significant quantity of 

native dry grassland or Oregon white oak woodland habitat. There are no known occurrences of 

Oregon white oak on this forest.

Wetlands

1O GP 

MBS 

OLY

INITIATE A SYSTEMATIC WETLAND INVENTORY PROGRAM TO LOCATE AND DESCRIBE WETLANDS AND ASSESS 

THEIR CONDITION.

1P GP 

MBS 

OLY

USE HISTORIC INFORMATION AND AERIAL PHOTOGRAPHY TO IDENTIFY CHANGES TO INDIVIDUAL WETLANDS 

OVER TIME.

1Q GP 

MBS 

OLY

USING WETLAND INVENTORY RESULTS, SELECT AT-RISK WETLANDS FOR CONSERVATION AND RESTORATION 

BASED ON CRITERIA SUCH AS WETLAND TYPE; ECOLOGICAL IMPORTANCE; DOWNSTREAM RESOURCES;

KNOWN OCCURRENCE OF RARE, SENSITIVE, OR SPECIAL STATUS SPECIES; RESTORATION NEEDS; AND OTHER 

FOREST-LEVEL CONSIDERATIONS.

1R GP 

MBS 

OLY

INITIATE ON-GOING PHOTO-POINT MONITORING OF SELECTED WETLANDS.

1S GP 

MBS 

OLY

MONITOR WATER LEVEL, WATER TEMPERATURE, AND AMPHIBIAN PRESENCE IN SELECTED WETLANDS.

2. Maintain and enhance biodiversity and increase resilience

Alpine and subalpine

2I GP 

MBS 

OLY

IDENTIFY RARE OR UNCOMMON PLANT SPECIES OR SPECIES ON THE EDGES OF THEIR CURRENT RANGES FOR 

EX SITU GENE CONSERVATION, SEED COLLECTION, AND PRESERVATION.

2J GP 

MBS 

OLY

CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT INFESTATIONS WITHIN AND ALONG ACCESS ROUTES TO 

ALPINE AND SUBALPINE HABITATS.
94 Climate Change and Forest Biodiversity in Western Washington

Non-Forested Habitats

No. Forest Action

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

2K GP 

MBS 

OLY

CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT INFESTATIONS IN THESE HABITAT TYPES, INCLUDING 

NON-NATIVE GRASSES.

2L GP 

MBS 

OLY

IF ANY DEGRADED GRASSLAND, OREGON WHITE OAK WOODLANDS, OR BALDS ARE LOCATED, PRIORITIZE THE 

SITES FOR RESTORATION/REHABILITATION AND INITIATE RESTORATION/REHABILITATION PLANS.

2M OLY CONTINUE RESTORATION AND MONITORING OF THE SKOKOMISH PRAIRIE/SAVANNAH SITE.

Wetlands

2N GP 

MBS 

OLY

IDENTIFY AND REMOVE OR MITIGATE ARTIFICIAL BARRIERS, SUCH AS ROADS, CULVERTS, AND TRAILS, THAT 

DISRUPT NATURAL WETLAND HYDROLOGY IN SELECTED WETLANDS.

2O GP 

MBS 

OLY

CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT SPECIES IN SELECTED WETLANDS.

2P GP 

MBS 

OLY

IMPLEMENT RESTORATION ACTIVITIES IN SELECTED WETLANDS WHERE NEEDED.

3. Prepare for the future

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

3G GP 

MBS 

OLY

CONTINUE SEED COLLECTION AND, IF NEEDED, SEED INCREASE OF NATIVE GRASSLAND PLANTS, INCLUDING 

GRASSES. Target both rare and “workhorse” species for gene conservation and restoration 

purposes.

3H OLY CONTINUE TO INVENTORY AND PROTECT AND, IF NEEDED, ENHANCE REMNANT POPULATIONS OF DRY 

GRASSLAND PLANT SPECIES IN THE DENNIE AHL SEED ORCHARD.

Wetlands

3I GP 

MBS 

OLY

CONTINUE SEED COLLECTION AND, IF NEEDED, SEED INCREASE OF NATIVE WETLAND PLANTS. Target both 

rare and “workhorse” species for gene conservation and restoration purposes.

* Action item is aligned with a similar recommendation by the Washington Department of Ecology’s Natural Resources Topic 

Advisory Group adaptation strategy for genetic preservation and development.
Climate Change and Forest Biodiversity in Western Washington 95

Table 30. Action Items for the Gifford Pinchot National Forest

Forest Trees

No. Action

1. Learn about and track changes in plant communities as the climate changes

1A CONTINUE AND EXPAND THE SURVEY AND MAPPING PROGRAM FOR WHITEBARK PINE, WITH THE PARTICIPATION BY ALL LAND 

MANAGEMENT AGENCIES WITH WHITEBARK PINE HABITAT IN WASHINGTON STATE. This effort should include a refinement 

of the existing state-wide GIS layer of whitebark pine occurrences. Readily accessible data on whitebark pine’s 

present distribution is essential for monitoring and managing the species under climate change and pathogen 

threats.

1B DEVELOP A CONSERVATION AND MONITORING PLAN FOR THE THREE HIGH ELEVATION TREE SPECIES THAT RANKED HIGHEST 

IN VULNERABILITY TO CLIMATE CHANGE BUT THAT HAVE NOT BEEN MANAGED IN THE PAST: SUBALPINE FIR, MOUNTAIN 

HEMLOCK, AND ALASKA YELLOW-CEDAR.

1C CATALOG INFORMATION ON ALL KNOWN OFF-SITE FOREST PLANTATIONS ON THE NATIONAL FORESTS, AND CREATE A GIS

LAYER OF THESE PLANTATIONS. In the past, seed sources used for reforestation were sometimes not well matched 

to the seed zones in which the seedlings were planted. Some of these off-site plantations may now provide 

valuable information on response of trees to climatic stressors comparable to those predicted to occur under 

future climate change scenarios.

1E MEASURE POPULATION GENETICS OF GOLDEN CHINQUAPIN. Golden chinquapin is one of the four Group 3 species 

(table 2) and is listed by the US Forest Service as a sensitive species in Washington; however, nothing is known 

about the genetics of this species (table 18). To develop a conservation plan for golden chinquapin in 

Washington, it is necessary to know how genetically similar these populations are to the core of the species’ 

range in California and Oregon. In 2010, leaf samples were collected for genetic analysis from the two golden 

chinquapin populations in Washington. Additional leaf samples will be collected from other parts of the species’ 

range to determine the genetic diversity and population structure of: 1) the north-south extent of the species’ 

distribution, and 2) the Washington populations. This project includes partnerships with the Washington 

Department of Natural Resources (WADNR) (chinquapin is present on WADNR land on the Olympic Peninsula) 

and USFS National Forest Genetic Electrophoresis Lab (NFGEL) where genetic analysis will be performed.

2. Maintain and enhance biodiversity and increase resilience

2A CONTINUE THE NATIONAL FORESTS’ THINNING PROGRAMS. These programs achieve: 1) promotion of greater 

biodiversity by increasing the proportion of less abundant conifer and hardwood tree species, 2) the 

development of understory vegetation, 3) enhancement of the habitat value provided by forest stands, and 4) 

increased stand resistance and resilience to disturbance and environmental stressors.

2B* CONTINUE TO INCLUDE A VARIETY OF TREE SPECIES IN PLANTING PRESCRIPTIONS, WITH AN EMPHASIS ON UNDERREPRESENTED TREE SPECIES.

2F CONTINUE TO ACTIVELY MANAGE GOLDEN CHINQUAPIN SITES TO PROMOTE GROWTH AND SURVIVAL OF THE SPECIES. As with 

the Olympic Peninsula populations, these disjunct populations may differ genetically from those in the 

contiguous portion of the species’ range and therefore may contain unique adaptive genetic variation.
96 Climate Change and Forest Biodiversity in Western Washington

Forest Trees

No. Action

3. Prepare for the future

3A* PARTNER WITH OTHER LAND MANAGERS IN WESTERN WASHINGTON TO CREATE A VIRTUAL COOPERATIVE TREE SEED BANK.

This would increase the likelihood that appropriate seed will be available for reforestation after large-scale 

disturbances such as fire or insect outbreaks. Landowners can maintain their own seed inventories, but enter in 

cooperative agreements to share seed in the event of a major disturbance. As a first step, Forest Service 

personnel should form a partnership with silviculturists, geneticists, and seed managers from the WADNR and 

the National Park Service and others to develop an approach for sharing information and seed.

3B* MAINTAIN AN INVENTORY OF HIGH-QUALITY SEED FOR TREE SPECIES THAT ARE LIKELY TO BE NEEDED OVER THE NEXT 20

YEARS. Place a priority on species that can be planted after disturbance. Accomplish this through the following 

steps:

• Assess the viability of seed stored at the Forest Service storage facility at JH Stone Nursery

• Retest viability as needed

• Discard non-viable seed

• Update Seed Procurement Plans to include new and replacement collections

3D MAINTAIN THE WHITE SALMON, PLANTING CREEK, COYOTE, CISPUS, AND FRENCH BUTTE SEED ORCHARDS WHICH SERVE 

AS GENE CONSERVATION AREAS AND ARE THE FOREST’S MOST EFFICIENT SOURCE OF HIGH QUALITY TREE SEED FOR 

DOUGLAS-FIR, NOBLE FIR AND RUST RESISTANT WESTERN WHITE PINE.

3F ASSESS SEED VIABILITY OF INDIVIDUAL SELECTED TREE LOTS IN STORAGE. The three national forests in western 

Washington have over 5000 single tree seedlots from selected trees in storage at the Dorena Genetic 

Resources Center (table 25). Many of these seedlots have been in storage for one or more decades and their 

viability is unknown. Viability testing is expensive and time consuming so it is impractical to test every seed lot. 

Geneticists and silviculturists should jointly develop a prioritized list of seedlots for viability testing. Priority for 

testing should be based on several factors, including: 1) vulnerability rank of the species, 2) initial (or 

subsequent) viability test results, 3) age of seed, and 4) amount of seed available. Top priority should be given 

to highly vulnerable species, seedlots with low initial viability, older seed, and lots with a large amount of seed 

available. 

Non-Forested Habitats

No. Action

1. Learn about and track changes in plant communities as the climate changes

Alpine and subalpine

1G MAP AND INVENTORY ALPINE AND SUBALPINE MEADOWS. Select individual meadows for monitoring.

1H REVIEW HISTORIC AERIAL PHOTOGRAPHY TO IDENTIFY POTENTIAL TRENDS IN TREE ESTABLISHMENT IN MEADOWS AND TREE 

LINE CHANGE OVER TIME. Initiate photo-point monitoring and/or periodic aerial photography of selected alpine 

meadows to track changes in tree establishment.
Climate Change and Forest Biodiversity in Western Washington 97

Non-Forested Habitats

No. Action

1I IDENTIFY TARGET ALPINE AND SUBALPINE FORB, SHRUB, AND/OR TREES SPECIES BASED ON CRITERIA SUCH AS KEYSTONE 

FUNCTION, KNOWN VULNERABILITY, OR HABITAT INDICATOR STATUS, AND FORMALIZE A PROGRAM FOR MONITORING 

PHENOLOGY OF THESE SPECIES.

1J IDENTIFY AND MONITOR KEY HIGH-ELEVATION WILDLIFE SPECIES (I.E., PIKA, OLYMPIC MARMOT, CLARK’S NUTCRACKER,

POLLINATORS).

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

1K MAP AND INVENTORY EXISTING OCCURRENCES OF NATIVE DRY GRASSLANDS, BALDS, AND OREGON WHITE OAK SAVANNAS 

AND WOODLANDS.

1L USE SOIL MAPS, AERIAL PHOTOS, AND HISTORICAL INFORMATION TO IDENTIFY POTENTIAL HISTORICAL EXTENT OF THESE 

HABITATS ON NATIONAL FOREST LANDS.

1M CONDUCT FIELD RECONNAISSANCE OF FIA AND ECOLOGY PLOTS CONTAINING OREGON WHITE OAK, AND IDENTIFY HABITAT

TYPE ASSOCIATED WITH THESE OCCURRENCES. These sites are primarily in the southeast portion of the forest, with a 

single plot near Highway 12 farther north.

Wetlands

1O INITIATE A SYSTEMATIC WETLAND INVENTORY PROGRAM TO LOCATE AND DESCRIBE WETLANDS AND ASSESS THEIR 

CONDITION.

1P USE HISTORIC INFORMATION AND AERIAL PHOTOGRAPHY TO IDENTIFY CHANGES TO INDIVIDUAL WETLANDS OVER TIME.

1Q USING WETLAND INVENTORY RESULTS, SELECT AT-RISK WETLANDS FOR CONSERVATION AND RESTORATION BASED ON 

CRITERIA SUCH AS WETLAND TYPE; ECOLOGICAL IMPORTANCE; DOWNSTREAM RESOURCES; KNOWN OCCURRENCE OF RARE,

SENSITIVE, OR SPECIAL STATUS SPECIES; RESTORATION NEEDS; AND OTHER FOREST-LEVEL CONSIDERATIONS.

1R INITIATE ON-GOING PHOTO-POINT MONITORING OF SELECTED WETLANDS.

1S MONITOR WATER LEVEL, WATER TEMPERATURE, AND AMPHIBIAN PRESENCE IN SELECTED WETLANDS.

2. Maintain and enhance biodiversity and increase resilience

Alpine and subalpine

2I IDENTIFY RARE OR UNCOMMON PLANT SPECIES OR SPECIES ON THE EDGES OF THEIR CURRENT RANGES FOR EX SITU GENE 

CONSERVATION, SEED COLLECTION, AND PRESERVATION.

2J CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT INFESTATIONS WITHIN AND ALONG ACCESS ROUTES TO ALPINE AND 

SUBALPINE HABITATS.
98 Climate Change and Forest Biodiversity in Western Washington

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

2K CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT INFESTATIONS IN THESE HABITAT TYPES, INCLUDING NON-NATIVE 

GRASSES.

2L IF ANY DEGRADED GRASSLAND, OREGON WHITE OAK WOODLANDS, OR BALDS ARE LOCATED, PRIORITIZE THE SITES FOR 

RESTORATION/REHABILITATION AND INITIATE RESTORATION/REHABILITATION PLANS.

Wetlands

2N IDENTIFY AND REMOVE OR MITIGATE ARTIFICIAL BARRIERS, SUCH AS ROADS, CULVERTS, AND TRAILS, THAT DISRUPT 

NATURAL WETLAND HYDROLOGY IN SELECTED WETLANDS.

2O CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT SPECIES IN SELECTED WETLANDS.

2P IMPLEMENT RESTORATION ACTIVITIES IN SELECTED WETLANDS WHERE NEEDED.

3. Prepare for the future

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

3G CONTINUE SEED COLLECTION AND, IF NEEDED, SEED INCREASE OF NATIVE GRASSLAND PLANTS, INCLUDING GRASSES.

Target both rare and “workhorse” species for gene conservation and restoration purposes.

Wetlands

3I CONTINUE SEED COLLECTION AND, IF NEEDED, SEED INCREASE OF NATIVE WETLAND PLANTS. Target both rare and 

“workhorse” species for gene conservation and restoration purposes.

* Action item is aligned with a similar recommendation by the Washington Department of Ecology’s Natural Resources Topic Advisory 

Group adaptation strategy for genetic preservation and development.
Climate Change and Forest Biodiversity in Western Washington 99

Table 31. Action Items for the Mt. Baker-Snoqualmie National Forest

Forest Trees

No. Action

1. Learn about and track changes in plant communities as the climate changes

1A CONTINUE AND EXPAND THE SURVEY AND MAPPING PROGRAM FOR WHITEBARK PINE, WITH THE PARTICIPATION BY ALL LAND 

MANAGEMENT AGENCIES WITH WHITEBARK PINE HABITAT IN WASHINGTON STATE. This effort should include a 

refinement of the existing state-wide GIS layer of whitebark pine occurrences. Readily accessible data on 

whitebark pine’s present distribution is essential for monitoring and managing the species under climate 

change and pathogen threats.

1B DEVELOP A CONSERVATION AND MONITORING PLAN FOR THE THREE HIGH ELEVATION TREE SPECIES THAT RANKED HIGHEST 

IN VULNERABILITY TO CLIMATE CHANGE BUT THAT HAVE NOT BEEN MANAGED IN THE PAST: SUBALPINE FIR, MOUNTAIN 

HEMLOCK, AND ALASKA YELLOW-CEDAR.

1C CATALOG INFORMATION ON ALL KNOWN OFF-SITE FOREST PLANTATIONS ON THE NATIONAL FORESTS, AND CREATE A GIS

LAYER OF THESE PLANTATIONS. In the past, seed sources used for reforestation were sometimes not well matched 

to the seed zones in which the seedlings were planted. Some of these off-site plantations may now provide 

valuable information on response of trees to climatic stressors comparable to those predicted to occur under 

future climate change scenarios.

2. Maintain and enhance biodiversity and increase resilience

2A CONTINUE THE NATIONAL FORESTS’ THINNING PROGRAMS. These programs achieve: 1) promotion of greater 

biodiversity by increasing the proportion of less abundant conifer and hardwood tree species, 2) the 

development of understory vegetation, 3) enhancement of the habitat value provided by forest stands, and 4) 

increased stand resistance and resilience to disturbance and environmental stressors.

2B* CONTINUE TO INCLUDE A VARIETY OF TREE SPECIES IN PLANTING PRESCRIPTIONS, WITH AN EMPHASIS ON UNDERREPRESENTED TREE SPECIES.

3. Prepare for the future

3A* PARTNER WITH OTHER LAND MANAGERS IN WESTERN WASHINGTON TO CREATE A VIRTUAL COOPERATIVE TREE SEED BANK.

This would increase the likelihood that appropriate seed will be available for reforestation after large-scale 

disturbances such as fire or insect outbreaks. Landowners can maintain their own seed inventories, but enter in 

cooperative agreements to share seed in the event of a major disturbance. As a first step, Forest Service 

personnel should form a partnership with silviculturists, geneticists, and seed managers from the WADNR and 

the National Park Service and others to develop an approach for sharing information and seed.

3B* MAINTAIN AN INVENTORY OF HIGH-QUALITY SEED FOR TREE SPECIES THAT ARE LIKELY TO BE NEEDED OVER THE NEXT 20

YEARS. Place a priority on species that can be planted after disturbance. Accomplish this through the following 

steps:

• Assess the viability of seed stored at the Forest Service storage facility at JH Stone Nursery

• Retest viability as needed

• Discard non-viable seed

• Update Seed Procurement Plans to include new and replacement collections
100 Climate Change and Forest Biodiversity in Western Washington

Forest Trees

No. Action

3E MAINTAIN THE MCCULLOUGH SEED ORCHARD WHICH SERVES AS GENE CONSERVATION AREAS AND IS THE FOREST’S MOST 

EFFICIENT SOURCE OF HIGH QUALITY TREE SEED FOR DOUGLAS-FIR, NOBLE FIR AND RUST RESISTANT WESTERN WHITE 

PINE.

3F ASSESS SEED VIABILITY OF INDIVIDUAL SELECTED TREE LOTS IN STORAGE. The three national forests in western 

Washington have over 5000 single tree seedlots from selected trees in storage at the Dorena Genetic 

Resources Center (table 25). Many of these seedlots have been in storage for one or more decades and their 

viability is unknown. Viability testing is expensive and time consuming so it is impractical to test every seed lot. 

Geneticists and silviculturists should jointly develop a prioritized list of seedlots for viability testing. Priority for 

testing should be based on several factors, including: 1) vulnerability rank of the species, 2) initial (or 

subsequent) viability test results, 3) age of seed, and 4) amount of seed available. Top priority should be given 

to highly vulnerable species, seedlots with low initial viability, older seed, and lots with a large amount of seed 

available. 

Non-Forested Habitats

No. Action

1. Learn about and track changes in plant communities as the climate changes

Alpine and subalpine

1G MAP AND INVENTORY ALPINE AND SUBALPINE MEADOWS. Select individual meadows for monitoring.

1H REVIEW HISTORIC AERIAL PHOTOGRAPHY TO IDENTIFY POTENTIAL TRENDS IN TREE ESTABLISHMENT IN MEADOWS AND TREE 

LINE CHANGE OVER TIME. Initiate photo-point monitoring and/or periodic aerial photography of selected alpine 

meadows to track changes in tree establishment.

1I IDENTIFY TARGET ALPINE AND SUBALPINE FORB, SHRUB, AND/OR TREES SPECIES BASED ON CRITERIA SUCH AS KEYSTONE 

FUNCTION, KNOWN VULNERABILITY, OR HABITAT INDICATOR STATUS, AND FORMALIZE A PROGRAM FOR MONITORING 

PHENOLOGY OF THESE SPECIES.

1J IDENTIFY AND MONITOR KEY HIGH-ELEVATION WILDLIFE SPECIES (I.E., PIKA, OLYMPIC MARMOT, CLARK’S NUTCRACKER,

POLLINATORS).

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

1K MAP AND INVENTORY EXISTING OCCURRENCES OF NATIVE DRY GRASSLANDS, BALDS, AND OREGON WHITE OAK SAVANNAS 

AND WOODLANDS.

1L USE SOIL MAPS, AERIAL PHOTOS, AND HISTORICAL INFORMATION TO IDENTIFY POTENTIAL HISTORICAL EXTENT OF THESE 

HABITATS ON NATIONAL FOREST LANDS.
Climate Change and Forest Biodiversity in Western Washington 101

Non-Forested Habitats

No. Action

1N MAP, INVENTORY, AND ASSESS CONDITION OF EXISTING OCCURRENCES OF BALDS. One example of this habitat is the 

Greenwater-George Creek Overlook. Because of the generally higher elevations of the Mt. Baker-Snoqualmie 

National Forest, it is unlikely that there is any significant quantity of native dry grassland or Oregon white oak 

woodland habitat. There are no known occurrences of Oregon white oak on this forest.

Wetlands

1O INITIATE A SYSTEMATIC WETLAND INVENTORY PROGRAM TO LOCATE AND DESCRIBE WETLANDS AND ASSESS THEIR 

CONDITION.

1P USE HISTORIC INFORMATION AND AERIAL PHOTOGRAPHY TO IDENTIFY CHANGES TO INDIVIDUAL WETLANDS OVER TIME.

1Q USING WETLAND INVENTORY RESULTS, SELECT AT-RISK WETLANDS FOR CONSERVATION AND RESTORATION BASED ON 

CRITERIA SUCH AS WETLAND TYPE; ECOLOGICAL IMPORTANCE; DOWNSTREAM RESOURCES; KNOWN OCCURRENCE OF 

RARE, SENSITIVE, OR SPECIAL STATUS SPECIES; RESTORATION NEEDS; AND OTHER FOREST-LEVEL CONSIDERATIONS.

1R INITIATE ON-GOING PHOTO-POINT MONITORING OF SELECTED WETLANDS.

1S MONITOR WATER LEVEL, WATER TEMPERATURE, AND AMPHIBIAN PRESENCE IN SELECTED WETLANDS.

2. Maintain and enhance biodiversity and increase resilience

Alpine and subalpine

2I IDENTIFY RARE OR UNCOMMON PLANT SPECIES OR SPECIES ON THE EDGES OF THEIR CURRENT RANGES FOR EX SITU GENE 

CONSERVATION, SEED COLLECTION, AND PRESERVATION.

2J CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT INFESTATIONS WITHIN AND ALONG ACCESS ROUTES TO ALPINE AND 

SUBALPINE HABITATS.

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

2K CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT INFESTATIONS IN THESE HABITAT TYPES, INCLUDING NON-NATIVE 

GRASSES.

2L IF ANY DEGRADED GRASSLAND, OREGON WHITE OAK WOODLANDS, OR BALDS ARE LOCATED, PRIORITIZE THE SITES FOR 

RESTORATION/REHABILITATION AND INITIATE RESTORATION/REHABILITATION PLANS.

Wetlands

2N IDENTIFY AND REMOVE OR MITIGATE ARTIFICIAL BARRIERS, SUCH AS ROADS, CULVERTS, AND TRAILS, THAT DISRUPT 

NATURAL WETLAND HYDROLOGY IN SELECTED WETLANDS.

2O CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT SPECIES IN SELECTED WETLANDS.

2P IMPLEMENT RESTORATION ACTIVITIES IN SELECTED WETLANDS WHERE NEEDED.
102 Climate Change and Forest Biodiversity in Western Washington

Non-Forested Habitats

No. Action

3. Prepare for the future

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

3G CONTINUE SEED COLLECTION AND, IF NEEDED, SEED INCREASE OF NATIVE GRASSLAND PLANTS, INCLUDING GRASSES.

Target both rare and “workhorse” species for gene conservation and restoration purposes.

Wetlands

3I CONTINUE SEED COLLECTION AND, IF NEEDED, SEED INCREASE OF NATIVE WETLAND PLANTS. Target both rare and 

“workhorse” species for gene conservation and restoration purposes.

* Action item is aligned with a similar recommendation by the Washington Department of Ecology’s Natural Resources Topic 

Advisory Group adaptation strategy for genetic preservation and development.
Climate Change and Forest Biodiversity in Western Washington 103

Table 32. Action Items for the Olympic National Forest

Forest Trees

No. Action

1. Learn about and track changes in plant communities as the climate changes

1A CONTINUE AND EXPAND THE SURVEY AND MAPPING PROGRAM FOR WHITEBARK PINE, WITH THE PARTICIPATION BY ALL LAND 

MANAGEMENT AGENCIES WITH WHITEBARK PINE HABITAT IN WASHINGTON STATE. This effort should include a 

refinement of the existing state-wide GIS layer of whitebark pine occurrences. Readily accessible data on 

whitebark pine’s present distribution is essential for monitoring and managing the species under climate 

change and pathogen threats.

1B DEVELOP A CONSERVATION AND MONITORING PLAN FOR THE THREE HIGH ELEVATION TREE SPECIES THAT RANKED HIGHEST 

IN VULNERABILITY TO CLIMATE CHANGE BUT THAT HAVE NOT BEEN MANAGED IN THE PAST: SUBALPINE FIR, MOUNTAIN 

HEMLOCK, AND ALASKA YELLOW-CEDAR.

1C CATALOG INFORMATION ON ALL KNOWN OFF-SITE FOREST PLANTATIONS ON THE NATIONAL FORESTS, AND CREATE A GIS

LAYER OF THESE PLANTATIONS. In the past, seed sources used for reforestation were sometimes not well matched 

to the seed zones in which the seedlings were planted. Some of these off-site plantations may now provide 

valuable information on response of trees to climatic stressors comparable to those predicted to occur under 

future climate change scenarios.

1D* MONITOR VEGETATIVE AND REPRODUCTIVE PHENOLOGY IN SEED ORCHARDS. Timing of phenology is closely linked to 

climate, and collecting data on annual phenology and microclimate will allow us to determine if there are trends 

in how trees are responding to annual climate variation. A pilot program will be established in 2011 in the 

Dennie Ahl seed orchard to develop protocols for monitoring phenology in western white pine and Pacific silver 

fir in partnership with Dr. Constance Harrington of PNW Research Station and the WADNR. These two species 

were chosen because: 1) Pacific silver fir had the highest overall vulnerability in our index, 2) these species are 

present in the orchard, and 3) Douglas-fir and western red cedar phenology monitoring has already been 

implemented at the WADNR Meridian Seed Orchard.

1E MEASURE POPULATION GENETICS OF GOLDEN CHINQUAPIN. Golden chinquapin is one of the four Group 3 species 

(table 2) and is listed by the US Forest Service as a sensitive species in Washington; however, nothing is 

known about the genetics of this species (table 18). To develop a conservation plan for golden chinquapin in 

Washington, it is necessary to know how genetically similar these populations are to the core of the species’ 

range in California and Oregon. In 2010, leaf samples were collected for genetic analysis from the two golden 

chinquapin populations in Washington. Additional leaf samples will be collected from other parts of the species’ 

range to determine the genetic diversity and population structure of: 1) the north-south extent of the species’ 

distribution, and 2) the Washington populations. This project includes partnerships with the Washington 

Department of Natural Resources (WADNR) (chinquapin is present on WADNR land on the Olympic Peninsula) 

and USFS National Forest Genetic Electrophoresis Lab (NFGEL) where genetic analysis will be performed.

1F ASSESS GENETIC VARIATION AND POPULATION STRUCTURE IN THREE SPECIES WITH SMALL, ISOLATED DISJUNCT 

POPULATIONS: ENGELMANN SPRUCE ON THE OLYMPIC PENINSULA AND NOBLE FIR AND PACIFIC SILVER FIR IN THE WILLAPA 

HILLS. These disjunct populations, as well as a range of populations from across the full distribution of the 

species, should be sampled for genetic analysis. These projects would include partnerships with the Olympic 

National Park, WADNR, and the USDA NFGEL, where genetic analysis would be performed. Assessing 

genetic variation and population structure of species with disjunct populations is necessary to determine if 

these populations are genetically distinct from populations within the contiguous part of the species’ 

distribution. This information is important because these disjunct populations could end up as refugia under 

predicted climate change scenarios or, conversely, they might be more severely impacted because lack of 

gene flow would limit opportunities for immigration of more highly adapted genes from other populations. This 
104 Climate Change and Forest Biodiversity in Western Washington

Forest Trees

No. Action

lack of gene flow could limit their adaptive genetic variation. In either case, it will be critical to know whether 

these populations are genetically distinct as this would lead to restrictions on the movement of seed both into 

and out of them. 

2. Maintain and enhance biodiversity and increase resilience

2A CONTINUE THE NATIONAL FORESTS’ THINNING PROGRAMS. These programs achieve: 1) promotion of greater 

biodiversity by increasing the proportion of less abundant conifer and hardwood tree species, 2) the 

development of understory vegetation, 3) enhancement of the habitat value provided by forest stands, and 4) 

increased stand resistance and resilience to disturbance and environmental stressors.

2B* CONTINUE TO INCLUDE A VARIETY OF TREE SPECIES IN PLANTING PRESCRIPTIONS, WITH AN EMPHASIS ON UNDERREPRESENTED TREE SPECIES.

2C PRODUCE AN INTERAGENCY PLAN, INVOLVING THE FOREST SERVICE AND NATIONAL PARK SERVICE, TO MAP 

OCCURRENCES AND EVALUATE MANAGEMENT OPTIONS FOR ROCKY MOUNTAIN JUNIPER ON THE OLYMPIC PENINSULA. One 

product of this plan should be a GIS layer of all known occurrences of this species on the Peninsula. Recent 

genetic research indicates that the Olympic Peninsula and Puget Sound Region populations of Rocky Mountain 

juniper represent a unique species, seaside juniper (Juniperus maritima R. P. Adams) (Adams 2007, Adams et 

al. 2010). Management of this species should be re-evaluated in the context of this new information and the 

potential effects of climate change on the species’ habitat. Additional genetic analyses should be conducted, if

determined necessary, to verify the classification of this species.

2D DEVELOP A PARTNERSHIP BETWEEN THE FOREST SERVICE, WADNR, AND PRIVATE LANDOWNERS TO MAP, CONSERVE,

AND RESTORE GOLDEN CHINQUAPIN ON THE OLYMPIC PENINSULA. Golden chinquapin is the only Washington tree 

species currently listed by the Interagency Special Status / Sensitive Species Program (USDA 2010c). This 

effort should include the creation of a GIS layer documenting locations of golden chinquapin on the Olympic 

Peninsula. These disjunct Olympic Peninsula populations represent the northernmost occurrence of the 

species and may be genetically different from populations in the contiguous portion of the species’ range (see 

item 1E). The Olympic Peninsula populations therefore have the potential to contain adaptive genetic variation 

not present elsewhere in the range of golden chinquapin.

2E IN A COLLABORATIVE EFFORT BETWEEN OLYMPIC NATIONAL FOREST AND OLYMPIC NATIONAL PARK, MAP OCCURRENCES 

OF ENGELMANN SPRUCE ON THE OLYMPIC PENINSULA. Engelmann spruce occurs in at least one small, disjunct 

population on the Olympic Peninsula. This population is potentially important for the adaptive genetic variation 

that it may contain. This collaborative effort should include field verification of several other reported but 

unconfirmed occurrences of this species on the Olympic Peninsula (see map in appendix A).

2G* DEVELOP A PILOT PROJECT TO PLANT BLISTER RUST RESISTANT WESTERN WHITE PINE IN GAPS OR OPENINGS CREATED IN 

PRE-COMMERCIALLY THINNED STANDS AND YOUNG-GROWTH STANDS. Planting also could be implemented in older 

young-growth stands in natural openings created by wind and root rot pockets with low quantities of competing 

vegetation.

2H* EXPAND GENE CONSERVATION COLLECTIONS. Seed from rare species and disjunct populations should be collected 

for long-term ex situ gene conservation. These efforts are already under way for whitebark pine, but to-date no 

collections have been made for other species. Seed should be collected and sent to the USDA ARS National 

Center for Germplasm Preservation in Ft. Collins, CO for western Washington populations of Rocky Mountain 

juniper, golden chinquapin, Engelmann spruce, noble fir (from the Willapa Hills), Pacific silver fir (from the 

Willapa Hills), and ponderosa pine. This project would include partnerships with Olympic National Park, 

WADNR, and Dept. of Defense Joint Base Lewis-McChord.
Climate Change and Forest Biodiversity in Western Washington 105

Forest Trees

No. Action

3. Prepare for the future

3A* PARTNER WITH OTHER LAND MANAGERS IN WESTERN WASHINGTON TO CREATE A VIRTUAL COOPERATIVE TREE SEED BANK.

This would increase the likelihood that appropriate seed will be available for reforestation after large-scale 

disturbances such as fire or insect outbreaks. Landowners can maintain their own seed inventories, but enter in 

cooperative agreements to share seed in the event of a major disturbance. As a first step, Forest Service 

personnel should form a partnership with silviculturists, geneticists, and seed managers from the WADNR and 

the National Park Service and others to develop an approach for sharing information and seed.

3B* MAINTAIN AN INVENTORY OF HIGH-QUALITY SEED FOR TREE SPECIES THAT ARE LIKELY TO BE NEEDED OVER THE NEXT 20

YEARS. Place a priority on species that can be planted after disturbance. Accomplish this through the following 

steps:

• Assess the viability of seed stored at the Forest Service storage facility at JH Stone Nursery

• Retest viability as needed

• Discard non-viable seed

• Update Seed Procurement Plans to include new and replacement collections

3C MAINTAIN THE DENNIE AHL SEED ORCHARD WHICH SERVES AS A GENE CONSERVATION AREA AND IS THE FOREST’S MOST 

EFFICIENT SOURCE OF HIGH QUALITY TREE SEED FOR DOUGLAS-FIR, PACIFIC SILVER FIR, AND RUST RESISTANT WESTERN 

WHITE PINE.

3F ASSESS SEED VIABILITY OF INDIVIDUAL SELECTED TREE LOTS IN STORAGE. The three national forests in western 

Washington have over 5000 single tree seedlots from selected trees in storage at the Dorena Genetic 

Resources Center (table 25). Many of these seedlots have been in storage for one or more decades and their 

viability is unknown. Viability testing is expensive and time consuming so it is impractical to test every seed lot. 

Geneticists and silviculturists should jointly develop a prioritized list of seedlots for viability testing. Priority for 

testing should be based on several factors, including: 1) vulnerability rank of the species, 2) initial (or 

subsequent) viability test results, 3) age of seed, and 4) amount of seed available. Top priority should be given 

to highly vulnerable species, seedlots with low initial viability, older seed, and lots with a large amount of seed 

available. 

Non-Forested Habitats

No. Action

1. Learn about and track changes in plant communities as the climate changes

Alpine and subalpine

1G MAP AND INVENTORY ALPINE AND SUBALPINE MEADOWS. Select individual meadows for monitoring.
106 Climate Change and Forest Biodiversity in Western Washington

Non-Forested Habitats

No. Action

1H REVIEW HISTORIC AERIAL PHOTOGRAPHY TO IDENTIFY POTENTIAL TRENDS IN TREE ESTABLISHMENT IN MEADOWS AND TREE 

LINE CHANGE OVER TIME. Initiate photo-point monitoring and/or periodic aerial photography of selected alpine 

meadows to track changes in tree establishment.

1I IDENTIFY TARGET ALPINE AND SUBALPINE FORB, SHRUB, AND/OR TREES SPECIES BASED ON CRITERIA SUCH AS KEYSTONE 

FUNCTION, KNOWN VULNERABILITY, OR HABITAT INDICATOR STATUS, AND FORMALIZE A PROGRAM FOR MONITORING 

PHENOLOGY OF THESE SPECIES.

1J IDENTIFY AND MONITOR KEY HIGH-ELEVATION WILDLIFE SPECIES (I.E., PIKA, OLYMPIC MARMOT, CLARK’S NUTCRACKER,

POLLINATORS).

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

1K MAP AND INVENTORY EXISTING OCCURRENCES OF NATIVE DRY GRASSLANDS, BALDS, AND OREGON WHITE OAK SAVANNAS 

AND WOODLANDS.

1L USE SOIL MAPS, AERIAL PHOTOS, AND HISTORICAL INFORMATION TO IDENTIFY POTENTIAL HISTORICAL EXTENT OF THESE 

HABITATS ON NATIONAL FOREST LANDS.

Wetlands

1O INITIATE A SYSTEMATIC WETLAND INVENTORY PROGRAM TO LOCATE AND DESCRIBE WETLANDS AND ASSESS THEIR 

CONDITION.

1P USE HISTORIC INFORMATION AND AERIAL PHOTOGRAPHY TO IDENTIFY CHANGES TO INDIVIDUAL WETLANDS OVER TIME.

1Q USING WETLAND INVENTORY RESULTS, SELECT AT-RISK WETLANDS FOR CONSERVATION AND RESTORATION BASED ON 

CRITERIA SUCH AS WETLAND TYPE; ECOLOGICAL IMPORTANCE; DOWNSTREAM RESOURCES; KNOWN OCCURRENCE OF 

RARE, SENSITIVE, OR SPECIAL STATUS SPECIES; RESTORATION NEEDS; AND OTHER FOREST-LEVEL CONSIDERATIONS.

1R INITIATE ON-GOING PHOTO-POINT MONITORING OF SELECTED WETLANDS.

1S MONITOR WATER LEVEL, WATER TEMPERATURE, AND AMPHIBIAN PRESENCE IN SELECTED WETLANDS.

2. Maintain and enhance biodiversity and increase resilience

Alpine and subalpine

2I IDENTIFY RARE OR UNCOMMON PLANT SPECIES OR SPECIES ON THE EDGES OF THEIR CURRENT RANGES FOR EX SITU GENE 

CONSERVATION, SEED COLLECTION, AND PRESERVATION.

2J CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT INFESTATIONS WITHIN AND ALONG ACCESS ROUTES TO ALPINE AND 

SUBALPINE HABITATS.

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

2K CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT INFESTATIONS IN THESE HABITAT TYPES, INCLUDING NON-NATIVE 

GRASSES.
Climate Change and Forest Biodiversity in Western Washington 107

Non-Forested Habitats

No. Action

2L IF ANY DEGRADED GRASSLAND, OREGON WHITE OAK WOODLANDS, OR BALDS ARE LOCATED, PRIORITIZE THE SITES FOR 

RESTORATION/REHABILITATION AND INITIATE RESTORATION/REHABILITATION PLANS.

2M CONTINUE RESTORATION AND MONITORING OF THE SKOKOMISH PRAIRIE/SAVANNAH SITE.

Wetlands

2N IDENTIFY AND REMOVE OR MITIGATE ARTIFICIAL BARRIERS, SUCH AS ROADS, CULVERTS, AND TRAILS, THAT DISRUPT 

NATURAL WETLAND HYDROLOGY IN SELECTED WETLANDS.

2O CONTINUE TO INVENTORY AND TREAT INVASIVE PLANT SPECIES IN SELECTED WETLANDS.

2P IMPLEMENT RESTORATION ACTIVITIES IN SELECTED WETLANDS WHERE NEEDED.

3. Prepare for the future

Dry grasslands (includes native prairies, balds, and Oregon white oak savannas and woodlands; for the Mt. BakerSnoqualmie National Forest, the dry grasslands action items apply to balds only)

3G CONTINUE SEED COLLECTION AND, IF NEEDED, SEED INCREASE OF NATIVE GRASSLAND PLANTS, INCLUDING GRASSES.

Target both rare and “workhorse” species for gene conservation and restoration purposes.

3H CONTINUE TO INVENTORY AND PROTECT AND, IF NEEDED, ENHANCE REMNANT POPULATIONS OF DRY GRASSLAND PLANT 

SPECIES IN THE DENNIE AHL SEED ORCHARD.

Wetlands

3I CONTINUE SEED COLLECTION AND, IF NEEDED, SEED INCREASE OF NATIVE WETLAND PLANTS. Target both rare and 

“workhorse” species for gene conservation and restoration purposes.

* Action item is aligned with a similar recommendation by the Washington Department of Ecology’s Natural Resources Topic 

Advisory Group adaptation strategy for genetic preservation and development.
108 Climate Change and Forest Biodiversity in Western Washington

RESOURCES FOR NON-FORESTED HABITATS

• Seed collection: Seeds of Success (www.nps.gov/plants/sos) and Rare Care 

(courses.washington.edu/rarecare) are established seed-collection programs and have 

been partners with the Forest Service for seed collection and gene conservation efforts.

• Aerial photography: The Forest Service’s Remote Sensing Application Center (RSAC) 

annually offers free special purpose aerial photography to R6 forests. 

• Phenology tracking: USA National Phenology Network (www.usanpn.org). The Forest 

Service is a member of this network.

• Ecological inventory and assessment: The Ecological Integrity Assessment (EIA) 

Framework may be a useful conceptual model for designing an efficient inventory 

program, and prioritizing locations for quantitative field assessments. This framework 

uses three levels of assessment—remote, rapid, and intensive. Remote assessment

requires the least investment of time and resources; intensive requires the most. See 

www1.dnr.wa.gov/nhp/refdesk/communities/eia.html for more information. The process 

fosters efficient identification of selected ecological units (e.g., wetlands) to prioritize for 

further study or management.

• Oregon white oak and dry grassland/prairie restoration: South Puget Sound 

Ecological Fire Program partners, including Joint Base Lewis-McChord, The Nature 

Conservancy, WA Department of Fish and Wildlife, and WA Department of Natural 

Resources, are experienced at oak woodland and prairie restoration and maintenance. 

South Puget Sound Prairie Landscape Working Group (www.southsoundprairies.org) is 

another good resource.
Climate Change and Forest Biodiversity in Western Washington 109

109

ACKNOWLEDGMENTS

The authors would like to thank Vicky Erickson, Tom 

DeMeo, and Kathy O’Halloran for providing financial 

and program support for this project.

We thank the following people for providing technical 

support and advice during the preparation of this 

report: Dominique Bachelet, Cheryl Bartlett, Kristen 

Chadwick, Rex Crawford, Chris Dowling, Gregory 

Filip, Jeffrey Foster, Joe Gates, Lise Grace, Andrew 

Gray, Jessica Halofsky, William Hargrove, Bruce 

Hostetler, Robin Lesher, Laura Potash Martin, Mike 

Messier, Jeff Muehleck, Marshall Murray, David 

Peter, Kevin Potter, Iral Ragenovich, Ann Risvold, Joe 

Rocchio, Regina Rochefort, Andrea Ruchty, Mark 

Senger, Linda Swartz, Karen Wells, and Beth Willhite.

We thank the following people for providing 

thoughtful reviews during preparation of this report: 

Dominique Bachelet, Cheryl Bartlett, Rex Crawford, 

Tom DeSpain, Vicky Erickson, Jeffrey Foster, Sharon 

Friedman, John Gross, Jessica Halofsky, Constance 

Harrington, Matt Horning, Glenn Howe, Laura Potash 

Martin, Kathy O’Halloran, Greg O’Neill, David 

Peterson, Susan Piper, Kevin Potter, Iral Ragenovich, 

Bryce Richardson, Ann Risvold, Joe Rocchio, Regina 

Rochefort, Brad St. Clair, Marcus Warwell, and Beth 

Willhite.

We thank Mary Carr of Forest Service Publishing Arts 

Staff for editorial support.
110 Climate Change and Forest Biodiversity in Western Washington

110

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Climate Change and Forest Biodiversity in Western Washington A-1

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APPENDIX A:

TREE SPECIES DISTRIBUTION MAPS
A-2 Climate Change and Forest Biodiversity in Western Washington

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Table A-1. List of distribution maps for tree species of western Washington. The species distribution maps 

are prefaced by four maps (pages A-3 through A-6) showing the locations of all plots surveyed in each 

of the four major data sources.

Map Page

Forest Inventory and Analysis plot locations A-3

Ecology Core Dataset plot locations A-3

Current Vegetation Survey (CVS) plot locations A-5

National Park Service plot locations A-6

Scientific name Common name Symbol

Abies amabilis Pacific silver fir ABAM A-7

Abies grandis Grand fir ABGR A-8

Abies lasiocarpa Subalpine fir ABLA A-9

Abies procera Noble fir ABPR A-10

Acer glabrum var. douglasii Douglas maple ACGLD4 A-11

Acer macrophyllum Bigleaf maple ACMA3 A-12

Alnus rubra Red alder ALRU2 A-13

Arbutus menziesii Pacific madrone ARME A-14

Betula papyrifera Paper birch BEPA A-15

Chrysolepis chrysophylla Golden chinquapin CHCH7 A-16

Cornus nuttallii Pacific dogwood CONU4 A-17

Crataegus douglasii and C. suksdorfii Black hawthorn and Suksdorf’s 

hawthorn 

CRDO2, CRSU16 A-18

Cupressus nootkatensis Alaska yellow-cedar CUNO A-19

Frangula purshiana Cascara FRPU7 A-20

Fraxinus latifolia Oregon ash FRLA A-21

Juniperus scopulorum Rocky mountain juniper JUSC2 A-22

Malus fusca Western crab apple MAFU A-23

Picea engelmannii Engelmann spruce PIEN A-24

Picea sitchensis Sitka spruce PISI A-25

Pinus albicaulis Whitebark pine PIAL A-26

Pinus contorta var. contorta and var. 

latifolia

Shore pine and lodgepole pine PICOC, PICOL A-27

Pinus monticola Western white pine PIMO3 A-28

Pinus ponderosa Ponderosa pine PIPO A-29

Populus balsamifera ssp. trichocarpa Black cottonwood POBAT A-30

Populus tremuloides Quaking aspen POTR5 A-31

Prunus emarginata Bitter cherry PREM A-32

Pseudotsuga menziesii Douglas-fir PSME A-33

Quercus garryana Oregon white oak QUGA4 A-34

Salix lucida var. lasiandra1 Pacific willow SALUL A-35

Salix scouleriana Scouler’s willow SASC A-36

Taxus brevifolia Pacific yew TABR2 A-37

Thuja plicata Western redcedar THPL A-38

Tsuga heterophylla Western hemlock TSHE A-39

Tsuga mertensiana Mountain hemlock TSME A-40

1 Individual occurrence data not available for this species; instead a general range map is shown.
Climate Change and Forest Biodiversity in Western Washington A-3

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A-4 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-5

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A-6 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-7

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A-8 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-9

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A-10 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-11

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A-12 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-13

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A-14 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-15

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A-16 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-17

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A-18 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-19

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A-20 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-21

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A-22 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-23

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A-24 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-25

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A-26 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-27

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A-28 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-29

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A-30 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-31

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A-32 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-33

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A-34 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-35

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A-36 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-37

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A-38 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington A-39

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A-40 Climate Change and Forest Biodiversity in Western Washington

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Climate Change and Forest Biodiversity in Western Washington B-1

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APPENDIX B:

TREE SPECIES PROFILES
B-2 Climate Change and Forest Biodiversity in Western Washington

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Table B-1. List of profiles for tree species of western Washington

Scientific name Common name Symbol Page

Abies amabilis Pacific silver fir ABAM B-4

Abies grandis Grand fir ABGR B-7

Abies lasiocarpa Subalpine fir ABLA B-10

Abies procera Noble fir ABPR B-13

Acer glabrum var. douglasii Douglas maple ACGLD4 B-16

Acer macrophyllum Bigleaf maple ACMA3 B-18

Alnus rubra Red alder ALRU2 B-21

Arbutus menziesii Pacific madrone ARME B-24

Betula papyrifera Paper birch BEPA B-27

Chrysolepis chrysophylla Golden chinquapin CHCH7 B-30

Cornus nuttallii Pacific dogwood CONU4 B-33

Crataegus douglasii and C. suksdorfii Black hawthorn and Suksdorf’s 

hawthorn 

CRDO2, CRSU16 B-35

Cupressus nootkatensis Alaska yellow-cedar CUNO B-37

Frangula purshiana Cascara FRPU7 B-40

Fraxinus latifolia Oregon ash FRLA B-42

Juniperus scopulorum Rocky mountain juniper JUSC2 B-44

Malus fusca Western crab apple MAFU B-46

Picea engelmannii Engelmann spruce PIEN B-48

Picea sitchensis Sitka spruce PISI B-51

Pinus albicaulis Whitebark pine PIAL B-54

Pinus contorta var. contorta Shore pine PICOC B-57

Pinus contorta var. latifolia Lodgepole pine PICOL B-60

Pinus monticola Western white pine PIMO3 B-63

Pinus ponderosa Ponderosa pine PIPO B-66

Populus balsamifera ssp. trichocarpa Black cottonwood POBAT B-69

Populus tremuloides Quaking aspen POTR5 B-72

Prunus emarginata Bitter cherry PREM B-75

Pseudotsuga menziesii Douglas-fir PSME B-77

Quercus garryana Oregon white oak QUGA4 B-80

Salix lucida var. lasiandra Pacific willow SALUL B-83

Salix scouleriana Scouler’s willow SASC B-85

Taxus brevifolia Pacific yew TABR2 B-87

Thuja plicata Western redcedar THPL B-90

Tsuga heterophylla Western hemlock TSHE B-93

Tsuga mertensiana Mountain hemlock TSME B-96
Climate Change and Forest Biodiversity in Western Washington B-3

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Table B-2. NatureServe conservation status ranking and geographic scale 

definitions. The conservation status ranking and geographic scale of the 

ranking are listed in each tree species’ profile (e.g., G5 indicates the 

species is secure at the global scale). Additional information on 

NatureServe rankings is available at: 

http://www.natureserve.org/explorer/ranking.htm

Variable Level Meaning

NatureServe ranking 1 Critically imperiled

2 Imperiled

3 Vulnerable

4 Apparently secure

5 Secure

Geographic scale G Global

N National

S State
B-4 Climate Change and Forest Biodiversity in Western Washington

4

Pacific silver fir (Abies amabilis)

Ecology

Description A medium-to-large, evergreen conifer typically reaching 150 to 200 ft (45 to 60 

m) in height; a narrow, symmetrical, conical crown; straight, horizontal 

branches; smooth, light-gray bark

Distribution From southeastern Alaska to around Crater Lake, Oregon, and infrequently in 

northwestern California; from 800 to 6,000 ft (240 to 1,830 m) elevation on the 

west side of the Cascade Range and from 3,300 to 6,000 ft (1000 to 1830 m) 

on the east side; occurs in the Olympics from sea level to 4,600 ft (1,400 m); 

also native to the Coast Range of southwestern Washington in the Willapa 

Hills, Doty Hills, and Black Hills, from 1,200 to 2,800 ft (370 to 850 m)

Successional stage Occurs in all seral stages; most prevalent in late seral and climax stands; 

Pacific silver fir may establish soon after disturbance, but growth is too slow to 

compete with associated conifers; its high degree of shade tolerance allows it 

to persist and become an important overstory component of mid- to late-seral 

stands, sometimes several hundred years after a disturbance

Associated forest cover Occurs most often with western hemlock, occurs with Douglas-fir on drier sites 

within its range; found to a lesser extent with a variety of other conifers 

including western redcedar, Alaska yellow-cedar, noble fir, and grand fir; 

sometimes occurs in pure stands

Habitat Sites Found most frequently on submontane to subalpine sites, but occasionally 

occurs to sea level in the Olympic Range

Soils Occurs on a wide range of soil types, from nutrient poor to nutrient rich

Moisture Requires an uninterrupted supply of water throughout the year; found 

predominantly on moderately moist to very moist sites; best growth occurs 

where moisture is highest, assuming the soil maintains aeration; range is 

limited by summer drought

Temperature Low tolerance of heat; may require protection on harsh sites; moderately frost 

tolerant; intolerant of frozen soil owing to its winter water requirement; benefits 

from heavy accumulations of snow that insulate the soil and its shallow roots

Shade tolerance Very shade tolerant; requires relatively little growing space for its crown; often 

overtopped by other species owing to its slower growth

Interspecific 

interactions

Animal damage May incur damage from browsing by elk or bark-stripping by black bear; 

animal damage increases susceptibility to pathogens; high incidence of insect 

damage to seeds and cones

Mycorrhizal 

fungi

Roots highly mycorrhizal, particularly at high elevations; Cenococcum 

graniforme frequently associated with Pacific silver fir

Reproduction and Growth

Mode of reproduction Reproduction is sexual; monoecious
Climate Change and Forest Biodiversity in Western Washington B-5

5

Reproductive phenology Reproductive cycle begins in May when reproductive primordia are initiated 

and is completed when seeds reach maturity in late summer of the following 

year; development enters dormancy beginning in October or November of the 

first year; development of pollen- and seed-cone buds resumes in early April 

of the second year, and pollination occurs by late May (about 7 weeks after 

the end of dormancy), although fertilization does not take place until July; 

seeds reach maturity in late August or September; the period from pollination 

to seed maturity is 90 to 120 days; phenology varies by geographic location, 

elevation, local climate conditions, and snowpack

Pollination Wind-pollinated

Seed Seed type Cones 3 to 4 in (8 to 10 cm) long and 1.5 to 2 in (3.5 to 5 cm) wide; seeds 0.4 

to 0.5 in (10 to 12 mm) long and 0.2 in (4 mm) wide; seeds have a single wing 

approximately the same length as the seed body; seeds often fall in pairs

Seed-bearing 

age

Cone production begins around age 20 to 30 years

Seed size/ 

weight

Averages 11,000 seeds per lb (24,250 seeds per kg); ranges from 7,800 to 

20,800 seeds per lb (17,200 to 45,860 seeds per kg ), heavier than those of

most associated conifers

Seed longevity/ 

survivability

Seed viability did not decline after 6 months for seeds stored at ambient 

temperatures; seed may be stored for 5 years or longer at 1 °F (-17 °C)

Seed crop and 

frequency

Trees have low cone-bearing capacity; generally a poor seed producer, 

produces a low percentage of sound seed, probably a result of frequent years 

of low pollen production or the long period of time between pollination and 

fertilization; good seed crops occur approximately every 3 years

Seed 

dissemination

Time of year Seed dissemination begins in mid-September, relatively early compared to 

associated species; timing of seedfall is not related to latitude or elevation; 

seedfall declines by late October, although some seed may continue to fall 

through April; typically, larger seeds with higher viability are shed first

Method and 

dispersal 

agents

Seeds dispersed by gravity and wind; cones disintegrate as they mature; 

seeds occasionally dispersed by animals including Douglas squirrel

Distance Seeds not carried far by wind because they are relatively heavy; one third of 

dropped seed falls beyond 125 ft (38 m) of a stand edge; less than 10 percent 

falls beyond 375 ft (114 m)

Germination requirements Germination averages 20 to 30 percent; lack of pollination and insect damage 

are main reasons for low viability; requires a minimum cold stratification period 

of 3 to 4 weeks; germination greatest in cool, moist locations; germination 

most likely on mineral soil, but also occurs on organic soil, rotten wood, and 

litter

Seedling survival Seedling mortality most often caused by germination on snow, adverse 

climatic conditions, or competing vegetation; seedlings are sturdy and 

resistant to being flattened by wet snow or litter after snow melt

Vegetative phenology At an elevation of 3,280 ft (1,000 m) on Vancouver Island, vegetative bud 

development began in early April; bud burst occurred in early June; shoot 

elongation continued until late July; about that time, vegetative buds initiated 
B-6 Climate Change and Forest Biodiversity in Western Washington

6

leaf primordia, which developed until entering dormancy in November; in 

British Columbia, budburst was delayed by 1 day for every 65-ft (20-m) 

increase in elevation

Genetics

Mating system Predominantly outcrossing with a moderately high outcrossing rate

Outcrossing % (tm) 0.875

Genetic diversity Average levels of genetic diversity

Heterozygosity (He) 0.10

Geographic differentiation Weak genetic differentiation based on molecular markers

Fst or Gst 0.05

Genetic analysis research results Relatedness among individuals drops to near zero within distances 20 to 60 

m; low levels of inbreeding depression in growth of 2 to 5 percent detected in 

natural stands 

Threats and Management Considerations

Insects and disease Moderate risk of insect damage; balsam woolly adelgid (Adelges piceae) is the 

most frequent cause of damage and mortality; Pacific silver fir is susceptible to 

root and butt rots including Heterobasidion annosum, Phellinus weiri, and 

Armillaria mellea, although these are generally less frequent at high 

elevations; high incidence of insect damage to seed and cones

Fragmentation In Washington, Pacific silver fir occupies a relatively large area in the Cascade 

and Olympic Ranges; it occurs to a somewhat lesser extent in the Coast 

Range

Fire Extremely fire-sensitive owing to its thin bark, shallow roots, and highly 

flammable foliage; given the humidity and precipitation where it typically 

occurs, surface fires are rare and of low intensity

Other damaging agents More susceptible to windthrow than associated species

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations An important species in watersheds and is prevalent in wilderness and 

multiple-use recreation areas; it is invading high-elevation meadows in some 

locations in the Olympics; nursery seedlings planted in harvested areas have 

performed poorly

References

Arno and Hammerly 2007, Bonner and Karrfalt 2008, Cope 1992, Crawford and Oliver 1990, Davidson and ElKassaby 1997, Edwards 2008, El-Kassaby et al. 2003, Klinka et al. 2000, Murray and Treat 1980, Owens and Molder 

1977a, Owens and Molder 1977b, Ritland and Travis 2004, USDA NRCS 2010
Climate Change and Forest Biodiversity in Western Washington B-7

7

Grand fir (Abies grandis)

Ecology

Description A medium-sized, evergreen conifer reaching a height of 150 to 200 ft (45 to 60 

m); a long, conical crown that is rounded at the top; mature trees tend to lose 

apical dominance; branches are straight and horizontal; thick, furrowed bark 

similar to that of Douglas-fir

Distribution Occurs in separate coastal and interior distributions in the Pacific Northwest; 

coastal distribution extends from southwestern British Columbia to northern 

California, from the coast to the Cascade Range; interior distribution extends 

from southern British Columbia to central Idaho and eastern Oregon; in 

western Washington, Grand fir occurs most often from below 1,500 ft (450 m) 

elevation; in the Cascade Range it occurs up to 6,000 ft (1,830 m) on moist 

sites

Successional stage A seral or climax species; on moist, lowland sites its growth rate is sufficient 

for it to achieve overstory status; on dry sites, it grows more slowly and does 

not become part of the canopy until the stand nears climax conditions; grand 

fir establishes well on the bare mineral soil of disturbed sites

Associated forest cover Typically occurs in mixed stands, often as a minor species; in western 

Washington, grand fir occurs most frequently with Douglas-fir, Sitka spruce, 

Pacific silver fir, western redcedar, western hemlock, bigleaf maple, red alder, 

and black cottonwood

Habitat Sites Occurs most often in lowlands within its western Washington range, frequently 

in valleys and on floodplains

Soils Found on a variety of soil types, but occurs most often on moderately to highly 

nutrient-rich soils

Moisture Tolerant of a greatly fluctuating water table; also tolerant of relatively dry soils 

at higher elevations, where it forms a deep taproot 

Temperature Low frost tolerance; moderate heat tolerance

Shade tolerance Moderately shade-tolerant, less so than western hemlock, western redcedar, 

and other true firs; it generally outgrows these species but is outgrown by 

shade-intolerant species in full sunlight; grand fir is more shade tolerant in dry 

climates than in wet climates 

Interspecific 

interactions

Animal damage Grand fir is ranked intermediate in browse preference

Mycorrhizal 

fungi

Abies grandis is ectomycorrhizal and endomycorrhizal 

Reproduction and Growth

Mode of reproduction Reproduction is sexual; monoecious

Reproductive phenology Flowers between late March and mid-May, although early spring temperatures 

cause substantial variation in timing; cones mature in August or September 

and begin to disintegrate and drop seed approximately 1 month later
B-8 Climate Change and Forest Biodiversity in Western Washington

8

Pollination Wind-pollinated

Seed Seed type Large, winged seeds; sometimes 200 or more seeds per cone

Seed-bearing 

age

Begins to produce seed around age 20

Seed size/ 

weight

Ranges from 11,900 to 28,700 seeds per lb (26,200 to 63,100 seeds per kg), 

with an average of 18,400 seeds per lb (40,500 seeds per kg)

Seed longevity/ 

survivability

Seeds remain viable only through the first spring; seed may be stored for 

more than 5 years at 5 °F (-15 °C)

Seed crop and 

frequency

Seed production in western Washington is intermediate; produces a low 

percentage of sound seed; good seed crops occur every 2 to 3 years

Seed 

dissemination

Time of year Seedfall begins about mid-September

Method and 

dispersal 

agents

Cones disintegrate at maturity and seeds are dispersed by wind and rodents

Distance Average dispersal distance is about 150 to 200 ft (46 to 61 m), but adequate 

seed for regeneration is dispersed up to 400 ft (120 m)

Germination requirements Germination is quite variable, averaging 50 percent or less; seeds stratify over 

winter under cool, moist conditions; germination is greatest on mineral soil or 

duff

Seedling survival Seedling mortality is highest during the first 2 years after germination, when 

an average of 40 percent of seedlings die; early mortality is usually a result of 

fungal infection or summer drought; on exposed or dry sites, seedlings form 

deep taproots, which reduces their susceptibility to drought 

Vegetative phenology Vegetative buds become mitotically active in mid-March; bud burst occurs 

about mid-May; shoot elongation occurs through the end of June

Genetics

Genetic diversity Average levels of genetic diversity

Heterozygosity (He) 0.10

Geographic differentiation Weak differentiation based on molecular markers

Fst or Gst 0.057

Patterns of variation Slower growth and higher frost resistance in inland (northern Idaho and 

eastern Oregon) populations; genetic differences exist among northern and 

southern provenances, but little difference within 

Genetic analysis research results Several provenance tests established in Europe show variation in growth, 

survival, and volume production among provenances, with lower elevation 

provenances usually performing best
Climate Change and Forest Biodiversity in Western Washington B-9

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Threats and Management Considerations

Insects and disease Grand fir is relatively high in its susceptibility to insect damage; the most 

damaging species are balsam wooly adelgid, western spruce budworm and 

Douglas-fir tussock moth; grand fir is at high risk of fungal damage, particularly 

from laminated root rot, Armillaria root disease, and Indian paint fungus; 

insects also feed on grand fir seeds, reducing viability by 10 to 25 percent

Harvest Marketed with western hemlock and other true firs

Fragmentation Distributed contiguously throughout western Washington

Fire At maturity, resistant to low- and moderate-severity fire; less resistant to fire 

damage than Douglas-fir but more resistant than Pacific silver fir; does not 

survive crown fire; susceptibility is greater on moist sites than on dry sites 

where roots are deeper and bark is thicker

Other damaging agents Moderate tolerance to damage from snow and wind

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations As a moderately shade-tolerant species, grand fir may be suited to multi-aged 

silvicultural systems; sometimes responds well to release; a valued species for 

pulpwood

References

Arno and Hammerly 2007, Bonner and Karrfalt 2008, Burton and Cumming 1995, Foiles et al. 1990, Franklin and 

Krueger 1968, Franklin and Ritchie 1970, Howard and Aleksoff 2000, Klinka et al. 2000, Konnert and Reutz 1997, 

Nielsen and Rasmussen 2009, Owens 1984, Owens and Blake 1985, USDA NRCS 2010
B-10 Climate Change and Forest Biodiversity in Western Washington

10

Subalpine fir (Abies lasiocarpa)

Ecology

Description A medium-sized, evergreen conifer reaching a height of approximately 100 ft 

(30 m); a narrow, dense crown that extends to the ground; stiff, often 

downward-angled branches; gray-brown bark forming irregular scales on older 

trees

Distribution From Yukon Territory, Canada, southward to New Mexico; a major component 

of high-elevation forests in the Olympic and Cascade ranges; typically occurs 

from about 4,000 to 6,500 ft elevation (1,200 to 2,000 m) in the Olympic and 

Cascade Ranges, although it is found as high as 8,000 ft (2,440 m) on 

sheltered slopes and as low as 2,000 ft (610 m) along cold stream bottoms

Successional stage Occurs in all stages of secondary succession and as a climax dominant or 

codominant species; occurs as a pioneer on disturbed and severe sites

Associated forest cover Occurs in pure and mixed-species stands; occurs frequently with mountain 

hemlock, whitebark pine, Pacific silver fir, Engelmann spruce, and lodgepole 

pine; occurs less frequently with western hemlock, western white pine, grand 

fir, noble fir, and Sitka spruce

Habitat Sites Found in cold, mid- to high-elevation forests, typically with very heavy 

snowpack and short growing seasons

Soils Grows on a wide range of soils, including shallow, coarse-textured, and 

nutrient-poor soils; grows in poorly aerated soils

Moisture Occurs on soils ranging from somewhat dry to wet; moderately tolerant of 

drought; tolerant of flooding and fluctuating water tables

Temperature Occupies sites where winters are cold and summers are cool; moderately 

tolerant of heat; tolerates frozen soil

Shade tolerance Shade tolerant; often grows as a seral species that is gradually replaced by 

trees such as Pacific silver fir, grand fir, and mountain hemlock; often grows in 

openings at high elevations

Interspecific 

interactions

Animal damage Insects, small birds, and rodents may consume seeds; occasionally browsed 

by ungulates

Mycorrhizal 

fungi

Subalpine fir is ectomycorrhizal

Reproduction and Growth

Mode of reproduction Reproduces sexually and vegetatively; monoecious; vegetative reproduction 

occurs through layering

Reproductive phenology Reproductive cycle spans two growing seasons; cones are initiated in the 

spring of the first year; buds differentiate in midsummer; conelets become 

apparent in early spring of the second year; in late spring or early summer, 8 

to 9 weeks after the end of dormancy, pollination occurs; cones open in midAugust to mid-October; seeds ripen from mid-September to late-October

Pollination Wind-pollinated
Climate Change and Forest Biodiversity in Western Washington B-11

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Seed Seed type Seeds are approximately 0.25 in (6 mm) long; seeds have a single, large, 

terminal wing

Seed-bearing 

age

Seed production begins about age 20, but production is low in dense forest 

conditions

Seed size/ 

weight

Averages 34,800 seeds per lb (76,700 seeds per kg)

Seed longevity/ 

survivability

Seed remains viable for 1 year under natural conditions; seed may be stored 

for longer than 5 years at 1 °F (-17 °C)

Seed crop and 

frequency

Heavy seed crops occur every 3 to 5 years; between heavy crops are light 

crops or crop failures; heavy crops may be predicted by good radial growth in 

the 2 years prior; produces a low percentage of sound seed

Seed 

dissemination

Time of year Seedfall occurs in October and November, occasionally into December

Method and 

dispersal 

agents

As cones disintegrate, seeds are dispersed by wind; occasionally squirrels 

disperse seed by caching cones

Distance Seeds usually fall within 260 ft (80 m) of the source tree, rarely more than 330 

ft (100 m)

Germination requirements Germination rates average approximately 31 to 38 percent; seeds require 

stratification under the moist, cold conditions of snow cover; germination 

occurs within the first few weeks after snow melt

Seedling survival Seedling survival is highest on mineral soil, but seedlings also survive on duff, 

litter, and rotting wood; early root growth is rapid, while shoot growth is very 

slow; seedling mortality results from drought, heat-girdling, competing 

vegetation, frost heaving, animal damage, and pathogens

Vegetative phenology Vegetative bud burst occurs about mid-May to mid-June; lateral shoot 

elongation is rapid for approximately 1 month and then slows and stops by the 

end of the second month; height and radial growth are very slow at high 

elevations

Genetics

Mating system Predominantly outcrossing with moderately high outcrossing rate

Outcrossing % (tm) 0.89

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.12

Geographic differentiation Weak differentiation based on molecular markers

Fst or Gst 0.03

Genetic analysis research results Seedlings from an elevation gradient of about 3,600 ft (1,100 m) showed 

strong clinal variation in timing of growth cessation, growth rate, and biomass 

partitioning related to elevation
B-12 Climate Change and Forest Biodiversity in Western Washington

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Threats and Management Considerations

Insects and disease Very susceptible to a variety of insects including western spruce budworm, 

western balsam bark beetle, balsam woolly adelgid; very susceptible to root, 

heart, and butt rots including laminated root rot and Indian paint fungus 

Harvest Harvest is limited by its accessibility

Fragmentation Prevalent in high-elevation forests in the Olympic and Cascade Range; 

isolated and inaccessible stands are often not significantly altered by humans

Fire very sensitive to fire; highly susceptible to crown fire owing to highly 

flammable foliage and dense stands; may be slow to re-establish after fire 

owing to absence of seed source and competing herbaceous vegetation

Other damaging agents Susceptible to windthrow where exposed by harvest; very tolerant of heavy 

snowpack

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Well-suited to mixed-species stands and multi-aged management; natural 

regeneration usually preferred; planting usually ineffective; very susceptible to 

Indian paint fungus in pure, natural stands

References

Alexander et al. 1990, Arno and Hammerly 2007, Ettl and Peterson 2001, Franklin and Krueger 1968, Franklin and 

Ritchie 1970, Green 2005, Klinka et al. 2000, Kranabetter et al. 2009, Owens and Blake 1985, Owens and Singh 

1982, Schmidt 1957, Shea 1987, 1990, Uchytil 1991a, USDA NRCS 2010, Woodward et al. 1994
Climate Change and Forest Biodiversity in Western Washington B-13

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Noble fir (Abies procera)

Ecology

Description A medium-to-large, evergreen conifer; the largest of the true firs, sometimes 

reaching a height of more than 230 ft (70 m); self-prunes lower limbs resulting 

in a short, round-topped crown at maturity; gray-brown bark, increasingly 

reddish and deeply furrowed with age

Distribution Occurs only in Washington and Oregon, in the Cascade Range and to a 

lesser extent in the Coast Range; in Washington, noble fir occurs primarily on 

the western slopes of the Cascades from Stevens Pass southward; scattered 

populations occur in the peaks of the Willapa Hills in southwestern 

Washington; noble fir is found primarily at elevations between 3,000 and 5,000 

ft (910 and 1520 m)

Successional stage A pioneer or early seral species that may be replaced over time by more 

tolerant species including Pacific silver fir and western hemlock

Associated forest cover Associated with a wide variety of conifers including Douglas-fir, Pacific silver 

fir, grand fir, subalpine fir, western hemlock, mountain hemlock, western white 

pine, lodgepole pine, whitebark pine, western redcedar, Engelmann spruce, 

Sitka spruce, and Alaska yellow-cedar

Habitat Sites Occurs on a range of topography from gentle to steep slopes; grows best on 

warm, moist sites with southerly aspects

Soils Optimal soils include shallow to deep loams; moisture is more often a limiting 

factor than nutrients

Moisture Relatively low drought tolerance compared to its associates

Temperature Typically occurs where mean January temperature ranges from 24 to 30 °F (-4 

to -1 °C) and mean July temperature ranges from 56 to 61 °F (13 to 16 °C); 

high frost tolerance

Shade tolerance Intermediate shade tolerance; the least shade-tolerant of all American true 

firs; cannot establish beneath a closed forest canopy

Interspecific 

interactions

Animal damage Seedling browse damage less than for Douglas-fir; occasional black bear 

damage

Mycorrhizal 

fungi

Known to be ectomycorrhizal

Reproduction and Growth

Mode of reproduction Reproduction is sexual; monoecious

Reproductive phenology Male and female budburst from May to early June; pollination from June to 

early July; cones ripen in mid- to late-September; phenological events vary by 

2 weeks or more depending on weather; spring and summer events are 

usually 1 to 2 days later for every 100 ft (30 m) increase in elevation

Pollination Wind-pollinated

Seed Seed type Cones 4 to 6 in (10 to 15 cm); winged seeds; wing slightly longer than body
B-14 Climate Change and Forest Biodiversity in Western Washington

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Seed-bearing 

age

Seed production begins at age 20 to 30; large crops begin to occur 

approximately 20 years later

Seed size/ 

weight

Averages 13,500 seeds per lb (29,750 seeds per kg); seeds 0.5 by 0.25 in (12 

by 6 mm)

Seed longevity/ 

survivability

Seed viable for one season under natural conditions; seed may be stored for 

10 years or longer at -4 °C

Seed crop and 

frequency

Good seed crops every 3 to 6 years; 10 or more cones per tree produced in 

42 percent of years; older trees may produce large crops; seed crops poor in 

high Cascades and near the eastern edge of its range

Seed 

dissemination

Time of year Seeds dispersal begins from late September to early October

Method and 

dispersal 

agents

Seeds dispersed by wind

Distance Most seedfall within one or two tree heights of the source tree, although 

potential dispersal distance is more than 2,000 ft (610 m)

Germination requirements Seed viability is generally low, averaging 10 percent in natural stands; viability 

closely related to magnitude of cone crop; cold stratification required; 

germination epigeal; germination in or on snowbank yields minimal survival;

germination highest on mineral soil or moist humus

Seedling survival Survival highest when germination occurs on a moist microsite; no dominant 

taproot; frosts and competing vegetation are major sources of mortality

Vegetative phenology Vegetative budburst from late May to early July

Genetics

Mating system Predominantly outcrossing with high outcrossing rate (from planted stands in 

Norway)

Outcrossing % (tm) 0.94

Genetic diversity Above average genetic diversity

Heterozygosity (He) 0.22

Geographic differentiation Weak differentiation based on molecular markers

Fst or Gst 0.05

Patterns of variation Weak geographic differentiation on needle and cone traits 

Threats and Management Considerations

Insects and disease Insects, including noble fir bark beetle (Pseudohylesinus nobilis), not regarded 

as a significant problem; a variety of fungal pathogens are found on noble fir, 

although none cause extensive damage

Harvest Boughs are prized for wreaths and decoration
Climate Change and Forest Biodiversity in Western Washington B-15

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Fragmentation Contiguous range in the Cascades; disjunct population in the Willapa Hills of 

southwestern Washington

Fire Low resistance to fire when young; low to moderate resistance at maturity; 

foliage moderately to highly flammable; an early pioneer following standdestroying fires

Other damaging agents Very windfirm; tolerant of heavy snow

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Initial height growth is slow; often occurs in mixed stands where its low 

amount of taper results in a disproportionately large contribution to stand 

volume 

References

Arno and Hammerly 2007, Bonner and Karrfalt 2008, Cope 1993a, Franklin 1990, Franklin and Krueger 1968, 

Franklin and Ritchie 1970, Nielsen and Rasmussen 2009, Owens and Blake 1985, Siegismund and Kjaer 1997,

USDA NRCS 2010, Xie and Ying 1994, Yeh and Hu 2005
B-16 Climate Change and Forest Biodiversity in Western Washington

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Douglas maple (Acer glabrum var. douglasii)

Ecology

Taxonomy and nomenclature Douglas maple is one of six varieties of Rocky Mountain maple (Acer glabrum)

Description A deciduous, broadleaf shrub or small tree growing 20 to 40 ft (6 to 12 m) in 

height; an irregular crown, often with multiple stems; smooth, reddish bark 

becoming rougher with age

Distribution From Alaska south to California and east to Montana and Idaho; common at 

moderate elevations east of the Cascade Range in Washington; less common 

west of Washington’s Cascades

Successional stage Found in early seral, shrub-dominated vegetation; occurs in deciduous 

pioneer forests but also present in late successional and climax floodplain 

communities

Associated forest cover An understory species in a variety of conifer forests; often associated with 

ponderosa pine forests; does not compete with conifers to the extent that vine 

maple does; grows above the shrub layer

Habitat Sites Low to middle elevations; moist and dry sites; floodplains, streambanks, and 

forest edges; dry, open, rocky areas, including avalanche tracks; occurs on 

drier, more exposed sites than vine maple

Soils Occurs on a wide variety of soils, from wetlands to rocky slopes; found on 

soils of many parent materials; reportedly an indicator of nitrogen-rich soils in 

British Columbia

Moisture Tolerates periodic flooding and moderately high water tables; moderately 

drought tolerant

Temperature Tolerant of heat and cold temperatures

Shade tolerance Moderately shade-tolerant

Interspecific 

interactions

Animal damage An important browse species for deer and elk

Mycorrhizal 

fungi

Known to be mycorrhizal

Reproduction and Growth

Mode of reproduction Sexual and vegetative reproduction; may be monoecious or dioecious; sprouts 

from root crown after stem damage or top-kill

Reproductive phenology Flowers from late April to late June, depending on elevation and latitude; fruit 

develops from June to August; fruit ripens from July to October

Pollination Insect- and wind-pollinated

Seed Seed type Paired, winged samaras; 0.8 to 1.2 in (20 to 30 m) long

Seed-bearing 

age

Seed production may begin as early as age 10
Climate Change and Forest Biodiversity in Western Washington B-17

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Seed size/ 

weight

Seeds are 0.16 to 0.2 in (4 to 5 mm) long; 7,820 to 20,300 cleaned seeds per 

lb (17,240 to 44,750 seeds per kg) with an average of 13,430 seeds per lb 

(29,610 seeds per kg)

Seed longevity/ 

survivability

Seeds sometimes remain dormant for one or two growing seasons before 

germination; seeds may remain viable in storage for up to 3 years

Seed crop and 

frequency

Large seed crops occur every 1 to 3 years

Seed 

dissemination

Time of year Seeds dispersed beginning in September; some seeds may not be dropped 

until February

Method and 

dispersal 

agents

Seeds are dispersed by wind, whirling sideways

Distance Not reported

Germination requirements Seeds require approximately 6 months of chilling before embryos break 

dormancy; germination occurs on mineral soil or shallow organic layers, often 

in partial shade

Seedling survival Partial shade facilitates seedling establishment; after establishment, early 

growth is rapid in sunlight

Vegetative phenology Bud swell in late March or April; budburst in early April to mid-May; leaf growth 

may continue through June; stem elongation begins in late April and may 

continue until late August

Threats and Management Considerations

Insects and disease Little information available; significant damage from insects or disease has not 

been reported; dull red leaf spots attributed to unknown pathogen; Eriophyid

mite colonies sometimes occur on the underside of leaves

Harvest Not a commercial species

Fragmentation Occurrence is sporadic west of the Cascade Range

Fire Top-killed by fire; readily sprouts from root crown; a pioneer species in burned 

areas

Other damaging agents Not reported

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Growth is stimulated when the forest overstory is thinned; rapidly sprouts after 

stem is cut

References

Anderson 2001a, Arno and Hammerly 2007, USDA NRCS 2010
B-18 Climate Change and Forest Biodiversity in Western Washington

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Bigleaf maple (Acer macrophyllum)

Ecology

Description A medium-sized, deciduous, broadleaf tree; the largest North American 

maple, reaching a height of more than 100 ft (30 m); a broad, outstretched 

crown with large leaves; light gray bark when young, becoming dark and 

ridged with age

Distribution Coastal Pacific Northwest from British Columbia south to near San Francisco 

Bay in California; occurs in Washington from the coast to the western slope of 

the Cascade Range; occurs below 1,500 ft (460 m) elevation on the Olympic 

Peninsula

Successional stage Often occurs at intermediate or late seral stages in conifer forests; seedlings 

and sprouts grow rapidly after gap creation or canopy disturbance; follows 

willow or red alder in riparian succession

Associated forest cover Frequently found with Douglas-fir, western redcedar, and western hemlock; 

occurs on moist sites with willow, black cottonwood, and red alder; occurs in 

the Olympic rain forest with old-growth Sitka spruce and western hemlock

Habitat Sites Often found where relatively open overstories occur, such as wet sites, and, to 

a lesser extent, dry sites; sites range from bottomlands to steep slopes; 

common on hardwood floodplain forests

Soils Occurs on a wide range of soil types; does not require high levels of nutrients; 

soils range from well-drained alluvium to steep talus slopes;

Moisture Very flood-tolerant; southern and interior distribution limited by moisture 

Temperature Northern distribution limited by cold temperatures; moderately tolerant of heat; 

found on hot, dry sites in the Oregon Cascades

Shade tolerance Intermediate in shade tolerance; seedlings establish in conifer stands but 

usually survive fewer than 15 years unless the canopy is disturbed; mature 

bigleaf maple is found in conifer stands, where trees originated in canopy 

openings

Interspecific 

interactions

Animal damage Seedlings are highly palatable to deer; high level of seed predation by a 

variety of small mammals and birds; buds and flowers also consumed

Mycorrhizal 

fungi

Known to be ectomycorrhizal

Reproduction and Growth

Mode of reproduction Sexual and vegetative reproduction; monoecious; primarily sexual 

reproduction on undisturbed sites; sprouts vigorously from stumps

Reproductive phenology Flowers from March to June depending on elevation and latitude; pollination 

approximately 2 to 4 weeks after bud burst; seeds become ripe in September 

or October

Pollination Insect-pollinated

Seed Seed type Fused double samaras; wings 1.4 to 2 in (3.5 to 5 cm) long; large triangular or 
Climate Change and Forest Biodiversity in Western Washington B-19

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oval seeds

Seed-bearing 

age

Seed production begins about age 10

Seed size/ 

weight

Seeds 0.2 to 0.5 in (4 to 12 mm) long and 0.2 to 0.4 in (4 to 9 mm) thick; 

averages 3,200 seeds per lb (7,050 seeds per kg); ranges from 2,400 to 3,600 

seeds per lb (5,200 to 7,900 seeds per kg); seed coat is 60 to 70 percent of 

seed weight

Seed longevity/ 

survivability

Seeds remain viable for only a few months under natural conditions; seeds 

have been stored for 1 year at 34 °F (1 °C)

Seed crop and 

frequency

Although production varies among individuals, overall production is generally 

high every year, particularly in open areas

Seed 

dissemination

Time of year Most seeds dispersed between October and January, some not dropped until 

March

Method and 

dispersal

agents

Primarily dispersed by wind; some seeds may be dispersed by small 

mammals and birds

Distance Not documented

Germination requirements Seeds germinate beginning in winter, from late January through April or May; 

low temperature threshold for germination; germination epigeal; germination 

best on mineral soil or moist organic materials; with predation excluded, 30 to 

40 percent of viable seed germinates under natural conditions 

Seedling survival Seedling mortality may result from competition, moisture stress, low light, and 

herbivory; understory seedlings are abundant in some Douglas-fir stands, 

although growth is very slow until overstory disturbance occurs; seedlings and 

sprouts have high growth potential, given sufficient sunlight 

Vegetative phenology Leaves appear in late March or April and are retained through October

Genetics

Mating system High outcrossing rate

Outcrossing % (tm) 0. 945

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.15

Geographic differentiation Weak differentiation based on molecular markers

Fst or Gst 0.05

Threats and Management Considerations

Insects and disease Overall risk of damage from insects and fungi is low, although over-mature or 

damaged trees are often infected by root rot (Armillaria spp.) and butt rot 

(Ganoderma applanatum and Oxyporus populinus)
B-20 Climate Change and Forest Biodiversity in Western Washington

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Harvest Harvested with Douglas-fir in mixed stands; one of a few commercial 

hardwood species in the Pacific Northwest; used for veneer, furniture, and 

specialty products

Fragmentation Widespread throughout its range in western Washington

Fire Well-adapted to fire owing to its ability to sprout and grow rapidly after top-kill; 

only severe fires damage the root crown

Other damaging agents Boles or limbs may suffer breakage under heavy snow or high winds

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations A serious competitor in Douglas-fir stands, particularly after harvesting; 

sprouts and seedling grow faster than conifers and fallen leaves smother 

conifer seedlings

References

Arno and Hammerly 2007, Bonner and Karrfalt 2008, Guries and Nordheim 1984, Hamann and Wang 2006, Iddrisu 

and Ritland 2004, Klinka et al. 2000, Minore and Zasada 1990, Uchytil 1989a, USDA NRCS 2010, Xie et al. 2002
Climate Change and Forest Biodiversity in Western Washington B-21

21

Red alder (Alnus rubra)

Ecology

Description A medium-sized, short-lived, deciduous, broadleaf tree, often reaching 100 ft 

(30 m) in height; a narrow, rounded crown; smooth, light gray bark, often 

mottled due to lichen colonization

Distribution From southeastern Alaska to southern California; rarely found east of the 

Cascade Range in the Pacific Northwest; several isolated populations in Idaho

Successional stage Pioneer; aggressively establishes following natural and human-caused 

disturbances; on disturbed sites, outgrows its primary natural competitor, 

Douglas-fir, for approximately 25 years before Douglas-fir achieves equal 

height; considered a climax species where it occurs in swamps

Associated forest cover Often found in pure or mixed stands within coniferous forests of Douglas-fir, 

western redcedar, western hemlock, grand fir, and Sitka spruce; mixed stands 

are relatively young and may contain other broadleafs and conifers; occurs in 

riparian communities, in pure stands or mixed with black cottonwood, bigleaf 

maple, and willow; occurs in swamps with western redcedar

Habitat Sites Occurs most often in riparian areas, moist bottomlands, and moist lower 

slopes; prevalent where soil drainage is poor; found on relatively moist upland 

sites where disturbance has occurred, rarely on dry, south-facing slopes; 

primarily occurs at elevations below 2,400 ft (750 m)

Soils Found on a wide range of soils, from well-drained to poorly drained; has 

relatively high nutrient requirements, although it fixes nitrogen through 

bacteria in root nodules

Moisture Infrequent on dry soils; low tolerance of drought; growth limited by moisture; 

tolerates wet sites, flooding, greatly fluctuating water tables

Temperature Infrequent on exposed, south-facing slopes; susceptible to frost damage; 

range limited by low temperatures

Shade tolerance Shade intolerant; will not survive if overtopped; must remain in upper canopy 

in mixed stands

Interspecific 

interactions

Animal damage Occasional browse damage

Mycorrhizal 

fungi and 

symbiotic 

bacteria

Roots are ectomycorrhizal, but with only a few fungal species; root nodules 

contain the nitrogen-fixing actinomycete Frankia spp.; annual increases in soil 

nitrogen in alder stands range from 40 to 300 lb per ac (45 to 355 kg per ha)

Reproduction and Growth

Mode of reproduction Sexual and occasionally vegetative; monoecious; young trees sprout when 

stem is damaged

Reproductive phenology Flowering begins as early as late February and lasts as late as May; fruits 

ripen from early August though October 
B-22 Climate Change and Forest Biodiversity in Western Washington

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Pollination Wind-pollinated

Seed Seed type Woody cones, 0.5 to 1 in (1.2 to 2.5 cm) long, containing 50 to 100 seeds; 

seeds are nutlike, small, flattened, and winged

Seed-bearing 

age

Seed production begins as early as age 3 or 4 when open-grown or age 6 to 8 

in a stand; seed production peaks about age 25

Seed size/ 

weight

Seeds are very light; 666,000 seeds per lb (1,465,000 seeds per kg)

Seed longevity/ 

survivability

High rate of mortality for buried seed, but importance of seedbank uncertain; 

seed may be stored for 10 to 20 years at temperatures of 10 °F (-12 °C) or 

lower

Seed crop and 

frequency

Moderate crops nearly every year; heavy crops every 3 to 5 years

Seed 

dissemination

Time of year Dispersal begins around late September; most seeds dropped in fall or winter

Method and 

dispersal 

agents

Seeds dispersed by wind and water

Distance Several hundred yards (m)

Germination requirements Germinates in spring; germination highest on moist mineral soil, such as a 

disturbed seedbed, in full sunlight; germinates on other organic materials if 

moisture and light are available; germination increased by stratification; 

germination epigeal; germination ranges from 59 to 84 percent

Seedling survival Shade tolerated for up to several years; full sunlight required for normal 

development; small seed makes germinants very susceptible to drought 

mortality

Vegetative phenology Strongly influenced by climate and thus exhibits significant annual variation; 

radial growth lasts from approximately mid-April through mid-September; 

height growth begins slightly later than radial growth and continues until 

conditions become unfavorable

Genetics

Mating system Moderately high outcrossing rate

Outcrossing % (tm) 0.85

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.11

Geographic differentiation Weak differentiation based on molecular markers

Fst or Gst 0.08

Genetic analysis research results Strong geographic variation has been found in seedlings for top weight, bud 

flush and leaf abscission. Growth traits were correlated with temperature 

amplitude and length of the growing season, while phonological traits were 
Climate Change and Forest Biodiversity in Western Washington B-23

23

related to spring thermal sums and fall frost dates. Provenances differ in 

physiological traits, but not families within provenances.

Threats and Management Considerations

Insects and disease Insects and disease are not a significant problem, especially in younger 

stands

Harvest Harvest has increased in recent decades, and the price of red alder timber is 

increasing; current supply does not meet demand and a long-term shortage is 

anticipated; harvested red alder comes primarily from southwestern British 

Columbia and western Washington and Oregon

Fragmentation Red alder is widespread throughout western Washington at lower elevations

Fire Red alder stands generally are not prone to fire, and may serve as natural fire 

breaks; red alder tolerates light surface fires

Other damaging agents Ice storms and unseasonable frosts may cause damage; windthrow is not a 

significant problem

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Owing in part to its nitrogen-fixing properties, red alder is grown on sites 

including mine spoils, eroded banks, and other restoration projects; also may 

be grown in mixture or rotation with Douglas-fir

References

Ager et al. 1993; Arno and Hammerly 2007; Bonner and Karrfalt 2008; Dang et al. 1994; Harrington 1990, 2006; 

Hibbs et al. 1995; Klinka et al. 2000; Owens and Blake 1985; Uchytil 1989b; USDA NRCS 2010; WDNR 2010; Xie 

2008; Xie et al. 2002
B-24 Climate Change and Forest Biodiversity in Western Washington

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Pacific Madrone (Arbutus menziesii)

Ecology

Description A small-to-medium, evergreen, broadleaf tree reaching a height of 50 to 80 ft 

(15 to 25 m); irregular, umbrella-shaped crown with thick, glossy leaves; stem 

crooked and often divided; recognizable, smooth, peeling, reddish-brown bark

Distribution From the eastern coast of Vancouver Island, British Columbia, to San Diego 

County, California; occurs in the coastal mountains and lowlands; occurs in 

Washington from sea level to mountain slopes at 3,000 ft (915 m) elevation

Successional stage An early successional to subclimax species; establishes after disturbance and 

is not found in the forest understory

Associated forest cover Occurs individually or in groves, rarely in large stands; often interspersed 

among conifers including Douglas-fir, lodgepole pine, and western hemlock; 

also occurs with Oregon white oak, red alder, and bigleaf maple; often found 

in stands characterized by diverse structure and composition

Habitat Sites Found on a variety of terrain, from level to steeply sloping; found in canyons 

and on bluffs; most often found on south- and west-facing aspects

Soils Typically found on soils with poor to very poor nutrient availability; soils are 

typically dry in summer and often rapidly draining

Moisture Highly drought-tolerant; frequently occurs on sites with growing-season 

drought; intolerant of flooding

Temperature Very intolerant of frost; high tolerance of hot, exposed sites; in the Pacific 

Northwest, Pacific madrone occurs where winter temperatures are mild and 

diurnal temperature fluctuation is limited

Shade tolerance Low to intermediate tolerance of shade; shade-tolerant as a seedling; shadeintolerant at maturity

Interspecific 

interactions

Animal damage Minor damage from deer browsing

Mycorrhizal 

fungi

Wide-spreading root system is mycorrhizal 

Reproduction and Growth

Mode of reproduction Sexual and vegetative reproduction; monoecious; sprouts prolifically from 

dormant buds near the root collar

Reproductive phenology Flowers in May and June; fruits mature in October

Pollination Pollinated by bees and possibly hummingbirds 

Seed Seed type Red five-celled berry 0.3 to 0.5 in (8 to 12 mm) in diameter; an average of 20 

seeds per berry

Seed-bearing 

age

Berries may be produced as early as age 3 to 5
Climate Change and Forest Biodiversity in Western Washington B-25

25

Seed size/ 

weight

Fresh berries average 630 to 1,130 per lb (1,390 to 2,490 per kg); seed 

averages 258,000 per lb (568,800 per kg); seed ranges from 197,000 to 

320,000 per lb (434,300 to 705,500 per kg) 

Seed longevity/ 

survivability

Long-term seed dormancy and viability in the soil, possibly decades; 

dormancy broken by cool temperatures and moisture

Seed crop and 

frequency

Abundant fruit in most years; for individual trees, crop is correlated with size of 

living crown

Seed 

dissemination

Time of year Fruits mature in October

Method and 

dispersal 

agents

Seeds dispersed by birds, deer, rodents, and gravity

Distance Potential for long dispersal distances; specific data not available

Germination requirements Strong embryo dormancy; requires cold stratification for germination; epigeal; 

germination rates are fair to high, although mortality occurs rapidly without 

moisture of mineral soil 

Seedling survival Seedling mortality is high, particularly in the first year; mortality is caused by 

drought, fungi, litterfall, and invertebrates; survival is best in partial shade on 

bare mineral soil; seedlings are generally not abundant; early height growth is 

slow

Vegetative phenology Leaf bud swell begins in late March; second-year leaves fall in June or July; 

bark exfoliates from June through September

Genetics

Mating system High outcrossing rate

Outcrossing % (tm) 0.97

Genetic diversity Average genetic diversity based on AFLP

Heterozygosity (He) 0.094

Geographic differentiation Moderate population differentiation

Fst or Gst 0.15

Threats and Management Considerations

Insects and disease Minor risk of insect damage; moderate risk of fungal damage; a major cause 

of dieback and death is madrone canker; a variety of other fungal diseases, 

including sudden oak death (Phytophthora ramorum) affect Pacific madrone

Harvest Not a major commercial species; used for firewood or specialty products

Fragmentation Not a known threat in western Washington

Fire Seedlings, sprouts, and mature trees are very susceptible to fire; top-killed 

trees sprout from the root collar or burl; fire favors establishment of Pacific 

madrone seedlings
B-26 Climate Change and Forest Biodiversity in Western Washington

26

Other damaging agents Invasive species such as Scotch broom (Cytisus scoparius) impede 

regeneration; windfirm

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

References

Arno and Hammerly 2007, Beland et al. 2005, Harrington and Kraft 2004, Klinka et al. 2000, McDonald and 

Tappeiner 1990, Reeves 2007, USDA NRCS 2010
Climate Change and Forest Biodiversity in Western Washington B-27

27

Paper birch (Betula papyrifera var. papyrifera)

Ecology

Taxonomy and nomenclature Of the three varieties of Betula papyrifera; Betula papyrifera var. papyrifera is 

the only variety in the western portion of the contiguous 48 states; west of the 

continental divide, this variety is sometimes known as Betula papyrifera var. 

commutata

Description A medium-sized, deciduous, broadleaf tree reaching 80 ft (24 m) in height; 

short-lived; ascending branches form an open crown; single or multiple 

slender stems with distinctive white, papery bark

Distribution Occurs throughout the northern half of the United States, including Alaska, 

and across Canada; occurs in Washington sporadically from the Puget Sound 

region northward, from low elevations near Puget Sound to the North Cascade 

Range

Successional stage An aggressive pioneer species that rapidly colonizes disturbed areas and 

openings; replaced by shade-tolerant species after one generation

Associated forest cover Following disturbance, paper birch may dominate or be present as a 

component of a mixed-species stand; in Washington, it is most often 

associated with red alder, bigleaf maple, Douglas-fir, grand fir, and cascara; 

sometimes occurs with western hemlock and western redcedar

Habitat Sites Found on both upland and alluvial sites; occurs on mountain slopes, rock 

slides, open woodlands, pastures, river valleys, as well as edges of swamps 

and other wetlands

Soils Found on a wide range of soil types, from nutrient-poor to nutrient-rich; occurs 

on coarse- to fine-textured soils, as well as bog and peat soils

Moisture Tolerates flooding and a strongly fluctuating water table; only moderately 

tolerant of drought; responds to drought by shedding leaves

Temperature Tolerant of growing-season frost; moderately tolerant of high air temperatures

Shade tolerance Intolerant of shade

Interspecific 

interactions

Animal damage A preferred browse species of deer; stems damaged by hares, porcupines, 

squirrels, and birds; birds and small mammals eat buds and seeds

Mycorrhizal 

fungi

Associated with ectomycorrhizae and arbuscular mycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction is sexual (monoecious) and vegetative; sprouts vigorously from 

stumps or root collar following harvest or top-kill by fire

Reproductive phenology Male catkins are partially formed in fall and are dormant during winter; male 

catkins expand prior to flowering, which begins in April; female catkins appear 

before leaves are fully expanded in spring; fruit ripens from early August until 

mid-September

Pollination Wind-pollinated
B-28 Climate Change and Forest Biodiversity in Western Washington

28

Seed Seed type Fruits are small, double-winged nutlets, 0.06 in (1.5 mm) long by 0.03 in (0.8 

mm) wide

Seed-bearing 

age

Seed production begins around age 15 years; optimum production occurs 

from ages 40 to 70 years

Seed size/ 

weight

Averages 1,380,000 cleaned seeds per lb (3,042,000 per kg)

Seed longevity/ 

survivability

A small percentage of seed may remain viable in the forest floor for several 

years, particularly if seeds fall during a very dry year; dormant seed in the 

forest floor may be important in years of poor seed crops; seed has been 

stored for up to 15 years at 18 °F (-8 °C), although colder storage 

temperatures may improve viability

Seed crop and 

frequency

A prolific seed producer; good seed crops occur every other year on average; 

some seed produced every year; good seed years vary by location; the 

following year’s seed crop can be predicted by observing male catkins in fall; 

seed crop estimates range from 1 to 294 million seeds per ac (2.5 to 728 

million seeds per ha) in light and heavy years, respectively, although seed 

crops vary substantially by stand density and location

Seed 

dissemination

Time of year Seeds ripen from early August until mid-September; dispersal begins soon 

after ripening; most seed is dispersed by the end of November

Method and 

dispersal 

agents

Seed is primarily disseminated by wind, occasionally by water

Distance Majority of seed falls 100 to 200 ft (30 to 61 m) from parent tree; seedfall 330 

ft (100 m) from a stand edge is 10 percent of that within the stand

Germination requirements Seed viability varies greatly by locality, parent tree, and year; seed viability 

highest during heavy crop years; germination best on disturbed mineral soil or 

on mineral-organic mixtures; stratification not necessary; small germinants 

sensitive to soil moisture and temperature; germination might be highest in 

shade where soil is moist and cool; higher seed viability and germinant 

survival in good seed years than in poor years; germination epigeal 

Seedling survival Dry soils and competing vegetation lead to early mortality; early growth best 

on humus seedbeds in partial or full sunlight; browse damage may 

significantly reduce the quantity and vigor of regeneration

Vegetative phenology Vegetative bud activity may begin in spring when nighttime temperatures are 

still below freezing; shoot elongation begins after pollination, which occurs in 

April; stem expansion is correlated with air temperature in spring

Genetics

Patterns of variation Populations differ significantly for germination, cold hardiness, and biomass 

allocation but not for gas exchange; population differences in germination and 

cold hardiness were related to winter temperature

Genetic analysis research results Interior British Columbia population was the most frost hardy and seed 

transfer from warmer to colder environments might result in frost damage
Climate Change and Forest Biodiversity in Western Washington B-29

29

Threats and Management Considerations

Insects and disease Insects and fungal pathogens are not a major concern in the Pacific 

Northwest; bronze birch borer (Agrilus anxius) is the most serious insect pest, 

attacking older and weakened trees; a number of defoliators attack paper 

birch but seldom damage healthy trees

Fire Fire usually kills or top-kills paper birch trees owing to their thin, flammable 

bark; fire kills seeds on the ground and immature seeds in catkins; quickly 

establishes after fire through sprouting and lightweight, abundant seed 

Other damaging agents Sensitive to air pollution

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations A commercial species in boreal regions, either in pure stands or mixed with 

conifers; requires full sunlight for successful regeneration

References

Arno and Hammerly 2007; Benowicz et al. 2000, 2001a; Bonner and Karrfalt 2008; Brinkman 1974; Klinka et al. 

2000; Safford et al. 1990; Uchytil 1991b; USDA NRCS 2010; WDNR 2010
B-30 Climate Change and Forest Biodiversity in Western Washington

30

Golden chinquapin (Chrysolepis chrysophylla)

Ecology

Taxonomy and nomenclature Golden chinquapin is known as giant chinquapin in the USDA Plants 

Database; there are two varieties of Chrysolepis chrysophylla: Chrysolepis 

chrysophylla var. chrysophylla is the tree form described here, and 

Chrysolepis chrysophylla var. minor is the shrub form; the latter occurs in 

California and Oregon

Description A small-to-medium, broadleaf, evergreen tree, occasionally reaching a height 

of 100 to 120 ft (30 to 35 m); stout, spreading branches; crown is conical 

where open-grown; narrow, leathery leaves; smooth, dark-gray bark when 

young, becoming furrowed and forming reddish-brown plates with age

Distribution From Mason County, Washington, to Monterey County, California; from the 

coast to the crest of the Cascade Range; several small populations in Mason 

County and an additional disjunct population in Skamania County are its only 

known occurrences in Washington; found from sea level to over 6,000 ft (1830 

m) elevation in the Oregon Cascades

Successional stage Generally an early successional species, although it may persist on sites 

where conifers do not form a dense overstory; sprouts after top-kill and is thus 

favored by fire

Associated forest cover A minor component of a wide variety of forest types throughout its range; often 

occupies subcanopy in conifer stands; occurs most frequently in open areas 

and beneath sparse canopies of conifers; pure stands are rare; in 

Washington, associated with Douglas-fir, western hemlock, ponderosa pine, 

and vine maple; on Gifford Pinchot National Forest occurs where overstory is 

dominated by Douglas-fir or ponderosa pine; on Olympic National Forest 

occurs under 50 to 60 percent Douglas-fir canopy cover

Habitat Sites Wide ecological amplitude; most competitive on infertile, droughty sites; on 

Gifford Pinchot National Forest occurs on convex, mid- to lower-slope sites

Soils Occurs on a wide range of soils; growth is best on deep soils; often found on 

nutrient-poor soils

Moisture Very tolerant of droughty sites

Temperature Occurs on some of the hottest sites of the western Cascade slopes, as well as 

near the crest of the Oregon Cascade Range

Shade tolerance Intolerant to moderately tolerant of shade; seedlings are shade-tolerant; grows 

rapidly when released from shade of competition

Interspecific 

interactions

Animal damage Some browse damage known to occur in California

Mycorrhizal 

fungi

Possible mycorrhizal relationship with Tricholoma magnivelare
Climate Change and Forest Biodiversity in Western Washington B-31

31

Reproduction and Growth

Mode of reproduction Sexual and vegetative reproduction; monoecious; sprouts from stumps and 

basal burls following top-kill

Reproductive phenology Varies widely across range; flowering occurs from April to June in Pacific 

Northwest; fruit ripens from August to October; reproductive cycle spans two 

growing seasons

Pollination Wind-pollinated; sometimes bee-pollinated

Seed Seed type Spiny, chestnut-like burs 0.6 to 1 in (15 to 25 mm) in diameter contain one to 

three hard-shelled nuts

Seed-bearing 

age

Stump sprouts may produce seed as early as age 6; trees of seed origin 

produce seed sometime before age 40

Seed size/ 

weight

Averages 960 seeds per lb (2,120 seeds per kg); ranges from 830 to 1,100 

seeds per lb (1,800 to 2,400 seeds per kg)

Seed longevity/ 

survivability

Seed may be stored for 5 years or longer in a controlled environment

Seed crop and 

frequency

Some seed produced every year; relatively heavy production every 2 to 5 

years; seed viability may be low; in its shrub form, golden chinquapin flowers 

infrequently

Seed 

dissemination

Time of year Seed dispersal peaks around late September and extends into early 

December

Method and 

dispersal 

agents

Seeds dispersed by gravity, squirrels, and several species of birds; burs may 

be transported by larger mammals

Distance Some long-distance dispersal occurs via animals

Germination requirements Germination relatively low; 14 to 53 percent viability reported; germination 

hypogeal, occurring after 16 to 24 days; stratification may not be required; 

germination observed beneath shallow litter layer in partial shade

Seedling survival Seedlings often grow in partial shade; relatively cool, moist conditions 

required; seedling densities are typically low

Threats and Management Considerations

Insects and disease Susceptible to heart-rot fungi (Phellinus igniarius); the filbertworm (Melissopus 

latiferreanus) damages seed, reducing viability

Harvest Not a commercial timber species

Fragmentation Small, disjunct populations occur in Washington’s Mason and Skamania 

Counties; these represent the northernmost extent of the species’ range

Fire Well-adapted to frequent fire; sprouts vigorously after light or intense fire; 

aboveground portion highly susceptible to top-kill after fire; where fire is 

frequent and conditions are dry, sprouting is the primary form of regeneration

Other damaging agents Trees suffer from competition of overtopping conifers, a major problem in the 
B-32 Climate Change and Forest Biodiversity in Western Washington

32

Gifford Pinchot National Forest; windstorms damage trees, particularly those 

with heart-rot

NatureServe conservation status 

ranking and other listings

G5 Secure—Common; widespread and abundant

S2 Imperiled—Imperiled in the jurisdiction because of rarity due to very 

restricted range, very few populations, steep declines, or other factors making 

it very vulnerable to extirpation from jurisdiction; only two small disjunct 

populations of golden chinquapin occur in western Washington

Golden chinquapin is designated a sensitive species under the USDA Region 

6 Interagency Special Status/Sensitive Species Program (ISSSSP)

Silvicultural considerations Historically most silvicultural efforts have been directed at suppressing golden 

chinquapin in conifer stands

Importance to wildlife Only known host of Herr’s hairstreak butterfly (Habrodais grunus herri), which 

has NatureServe conservation status ranking G4/G5/T2/T3, N2/N3, S1

References

Arno and Hammerly 2007, Bonner and Karrfalt 2008, McKee 1990, McMurray 1989, Ruchty 2008, Shoal 2009, USDA 

NRCS 2010
Climate Change and Forest Biodiversity in Western Washington B-33

33

Pacific dogwood (Cornus nuttallii)

Ecology

Description A small-to-medium, deciduous, broadleaf tree reaching a height of 30 to 50 ft 

(9 to 15 m); many spreading, horizontal branches; thin, light-gray bark

Distribution Coastal regions from southern British Columbia to southern California; occurs 

in the Pacific Northwest from the Cascade Range to the coast; disjunct 

population in northern Idaho; below 5,000 ft (1,520 m) elevation

Successional stage Found in early to late seral stages; does not follow a distinct successional 

pattern; appears within 3 years of disturbance; often present in hardwood and 

second-growth conifer stands in British Columbia

Associated forest cover Typically a subcanopy species in forests dominated by Douglas-fir, western 

hemlock, Pacific silver fir, grand fir, western redcedar, and bigleaf maple

Habitat Sites Often most prevalent in riparian areas and on gentle slopes in low-elevation 

conifer, hardwood, and mixed forests

Soils Moist, well-drained soils; tolerant of acidic, nutrient-poor soils; soil texture 

ranges from clay to sandy loam

Moisture Considered a mesic species but also very drought tolerant; high flood 

tolerance

Temperature Low frost tolerance; moderate heat tolerance; often occurs on exposed slopes

Shade tolerance Moderate shade tolerance; often present under partial canopies; maximum 

photosynthetic potential is reached in 33 percent of full sunlight

Interspecific 

interactions

Animal damage Browse damage is greatest on sprouts and seedlings established after 

disturbance

Mycorrhizal 

fungi

Other species of the genus Cornus are mycorrhizal

Reproduction and Growth

Mode of reproduction Reproduces sexually and vegetatively; monoecious; readily sprouts after 

disturbance

Reproductive phenology May flower twice per growing season; first flowering occurs from April to June; 

second flowering in late summer or fall may not produce fruit; fruit from first 

flowering ripens in September or October

Pollination Primarily insect-pollinated

Seed Seed type Tight cluster of 20 to 40 slightly flattened red drupe

Seed-bearing 

age

Minimum seed-bearing age is 10 to 15 years

Seed size/ 

weight

Averages 4,700 seeds per lb (10,360 seeds per kg); drupes are approximately 

0.4 to 0.6 in (10 to 15 mm) long

Seed longevity/ Based on minimal evidence, seed may be part of the soil seed bank; seed of 
B-34 Climate Change and Forest Biodiversity in Western Washington

34

survivability Cornus florida has been stored successfully for 7 years at 19 °F (-7 °C)

Seed crop and 

frequency

Reports are inconsistent; heavy seed crops may occur every 1 or 2 years

Seed 

dissemination

Time of year Fruit ripens in September or October

Method and 

dispersal 

agents

Not formally studied, although seed probably dispersed by birds and small 

mammals

Distance Unknown

Germination requirements Germination is relatively high; exposed mineral soil benefits germination

Seedling survival Reports conflict; some indicate greater reproduction in shade and some 

indicate greater reproduction in sunlight

Genetics

Genetic diversity Low genetic diversity based on microsatellites

Heterozygosity (He) 0.468

Geographic differentiation Very high population differentiation based on microsatellites

Fst or Gst 0.9

Threats and Management Considerations

Insects and disease Dogwood anthracnose, caused by the non-native fungus Discula destructiva, 

is the primary pathogen in the Pacific Northwest; spreads rapidly; causes leaf 

spot, trunk cankers, branch dieback, and sometimes death; fungal activity is 

greatest when conditions are moist during the growing season

Harvest Not a commercial timber species

Fragmentation Widespread in western Washington

Fire Sprouts from the root crown after fire

NatureServe Conservation Status 

Ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Frequently planted as an ornamental

References

Arno and Hammerly 2007, Bonner and Karrfalt 2008, Gucker 2005, Kier and Aitken [n.d.], Klinka et al. 2000, USDA 

NRCS 2010
Climate Change and Forest Biodiversity in Western Washington B-35

35

Black hawthorn and Suksdorf’s hawthorn (Crataegus douglasii and C. 

suksdorfii)

Ecology

Taxonomy and nomenclature Black hawthorn in Washington was formerly known as a single species 

(Crataegus douglasii) with two varieties: var. suksdorfii and var. douglasii; 

these varieties are now accepted as separate species, although inventories 

and some earlier publications treated these as a single species, called black 

hawthorn; here we refer to both species where information is available at that 

level

Description A deciduous, broadleaf shrub or small tree reaching 20 ft (6 m) in height; often 

found in thickets; stems crooked; broad, brambly crowns of thorny branches 

Distribution Crataegus douglasii occurs in the coastal Pacific Northwest from southeastern 

Alaska to northern California; inland distribution occurs from Alberta and 

Saskatchewan south to Utah and Colorado; occurs both west and east of the 

Cascade Range in Washington; disjunct populations occur as far east as 

Minnesota, Michigan and Ontario, Canada; Crataegus suksdorfii occurs 

mainly in coastal regions from Alaska to northern California; in Washington it 

is primarily west of the Cascade crest

Successional stage Occasionally an early seral species, but typically found in established forest 

stands

Associated forest cover Occur in a wide variety of forest types owing to their broad distribution; most 

often occur as understory species; occasionally found in pure stands

Habitat Sites Both species occur on a range of sites including open woodlands, riparian 

areas, and steep slopes; found in moist areas but also on relatively dry 

southern aspects; occurs at low- to mid-elevations

Soils Most often found on deep, moist soils

Moisture Achieve best growth on moist sites; found in wetlands and on drier upland 

sites

Temperature Unknown, although the range suggests a degree of cold tolerance

Shade tolerance Intermediate shade tolerance; best growth in full sunlight; typically occurs in 

understory

Interspecific 

interactions

Animal damage Leaves and twigs are browsed by deer

Mycorrhizal 

fungi

Genus Crataegus is mycorrhizal

Reproduction and Growth

Mode of reproduction Sexual and vegetative; both C. douglasii and C. suksdorfii exhibit polyploidy 

and are known to reproduce by apomixis; monoecious; sprouts from stumps 

and roots

Reproductive phenology Flower around May in Washington; fruits ripen around August

Pollination Insect-pollinated
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Seed Seed type Cluster of black, fleshy pomes, approximately 0.4 in (11 cm) in diameter; as 

many as five seeds per fruit

Seed-bearing 

age

Unknown

Seed size/ 

weight

22,600 cleaned seeds per lb (49,800 seeds per kg)

Seed longevity/ 

survivability

Unknown

Seed crop and 

frequency

Produce many viable seeds; one British Columbia study found that trees 

averaged 550 fruits

Seed 

dissemination

Time of year Beginning around August when fruits ripen and continuing into winter

Method and 

dispersal 

agents

Fruits are an important food source for wildlife; fruits are consumed by deer, 

small mammals, and birds during fall and winter

Distance Unknown

Germination requirements Cold stratification and acid scarification have been successfully used to break 

dormancy 

Seedling survival Little information available on natural regeneration; artificial regeneration 

difficult; seedling growth slow; seedlings develop long taproots

Genetics

Heterozygosity (He) 0.73 using chloroplast microsatellites

Geographic differentiation Strong population differentiation

Fst or Gst 0.22 using nuclear microsatellites

Threats and Management Considerations

Insects and disease Insects and diseases are not a major problem, reported diseases include 

fireblight, cedar-hawthorn rust, cedar-quince rust, leaf blight, fruit rot, and leaf 

spot

Harvest Not a commercial species

Fragmentation Widespread in western Washington

Fire Top-killed by low- or high-severity fire; sprouts from root crown and roots 

following top-kill

NatureServe conservation status 

ranking

G4 Apparently Secure—Uncommon but not rare; some cause for long-term 

concern due to declines or other factors

References

Arno and Hammerly 2007, Habeck 1991, Jacobs et al. 2009, Lo et al. 2009, USDA NRCS 2010
Climate Change and Forest Biodiversity in Western Washington B-37

37

Alaska yellow-cedar (Cupressus nootkatensis)

Ecology

Taxonomy and nomenclature Also known as Chamaecyparis nootkatensis, Xanthocyparis nootkatensis, and 

Callitropsis nootkatensis

Description A medium-sized, evergreen conifer, sometimes reaching a height of more 

than 130 ft (40 m); a slightly twisted stem with a drooping leader; forms a 

pyramidal crown at maturity; sparse branches and drooping scale-leaved 

foliage; thin, purplish bark becoming shaggy and gray at maturity

Distribution In coastal mountain ranges from south-central Alaska to northern California; in 

Washington’s Olympic and Cascade Ranges; less common south of Mount 

Rainier; usually at elevations between 2,000 and 7,500 ft (600 to 2,300 m), but 

occasionally to near sea level in the Olympics

Successional stage Present in all successional stages; a pioneer species on subalpine, colluvial, 

and wetland sites; found in climax stands owing in part to its longevity (>700 

years)

Associated forest cover Often occurs individually or in small groups in conifer stands including 

mountain hemlock, Pacific silver fir, subalpine fir, western hemlock, noble fir, 

whitebark pine, and western white pine; occasionally found in pure stands

Habitat Sites Maritime climates, from low elevation to treeline; sometimes found at high 

elevations where its associates cannot survive; often found on harsh sites, 

such as thin soils or wet soils where other species grow poorly

Soils Thin organic or rocky soils; talus; soils low in nutrients; wet, poorly drained 

soils; best growth is on deep, well-drained soils but it cannot compete with its 

faster-growing associates on such sites

Moisture Moderately drought tolerant; high tolerance of flooding and saturated soils

Temperature Occurs where snow insulates the soil during winter

Shade tolerance Shade-tolerant; similar to Pacific silver fir in its shade tolerance; 

photosynthetic saturation reached at 60 percent of full sunlight

Interspecific 

interactions

Animal damage Browse damage is uncommon

Mycorrhizal 

fungi

Mycorrhizal with vesicular arbuscular species

Reproduction and Growth

Mode of reproduction Reproduces sexually and vegetatively; monoecious; vegetative reproduction 

through layering

Reproductive phenology Reproductive cycle spans three growing seasons in the northern portion of its 

range, two growing seasons in the southern portion; for the 3-year cycle, 

cones are initiated in year 1, pollination occurs in year 2, and cones mature in 

year 3; for the 2-year cycle, cones mature in the second year; flowers from 

April to June, 1 week after breaking dormancy; flowers earlier with decreasing 

elevation and latitude; cones reach maturity in September or October
B-38 Climate Change and Forest Biodiversity in Western Washington

38

Pollination Wind-pollinated

Seed Seed type Globe-shaped cones 0.3 to 0.5 in (8 to 12 mm) in diameter with four to six 

scales; 2 to 4 winged seeds per scale; a British Columbia study found an 

average of 7.2 seeds per cone

Seed size/ 

weight

Seeds 0.08 to 0.20 in (2 to 5 mm) long; 108,000 seeds per lb (240,000 seeds 

per kg)

Seed longevity/ 

survivability

Seeds may be stored at 32 °F (0 °C) for 3 to 5 years

Seed crop and 

frequency

Heavy seed crops occur irregularly, at intervals of 4 or more years; produces a 

low percentage of sound seed; seed viability is both low and extremely 

variable

Seed 

dissemination

Time of year Seed dispersal begins in October and continues through spring; seeds shed 

during dry periods

Method and 

dispersal 

agents

Wind-dispersed

Distance Dispersal distance is likely less than 400 ft (120 m)

Germination requirements Germination percentage is low; germination epigeal; germination best on 

mineral soil and well-decomposed organic matter; germination significantly 

increased by cold stratification after warm stratification

Seedling survival Seedlings relatively shade-tolerant; regeneration primarily vegetative on open 

sites and in closed-canopy forests south of Mount Rainier

Genetics

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.15

Geographic differentiation Moderate population differentiation

Fst or Gst 0.14

Genetic analysis research results Seedlings from higher elevations generally had higher cold hardiness than 

seedlings from lower elevations

Threats and Management Considerations

Insects and disease Insects and diseases are not a serious problem; wood is resistant to most 

fungal damage

Harvest A valuable timber species; harvested in the northern portion of its range

Fragmentation Distribution is sparse south of Mount Rainier and in parts of the Olympic 

Range

Fire Fire is infrequent in its cool, wet habitat; susceptible to fire damage owing to 

thin bark 
Climate Change and Forest Biodiversity in Western Washington B-39

39

Other damaging agents Dieback has been occurring in southeastern Alaska for more than a century; 

cause may be a climate-related decrease in snowpack depth leading to root 

frost damage

NatureServe conservation status 

ranking

G4 Apparently Secure—Uncommon but not rare; some cause for long-term 

concern due to declines or other factors

Silvicultural considerations Vegetative reproduction of seedling stock is preferred method of regeneration 

owing to poor seed crops and germination

References

Arno and Hammerly 2007, Berube et al. 2003, Griffith 1992a, Harrington 2010, Harris 1990a, Hawkins et al. 1994, 

Klinka et al. 2000, Ritland et al. 2001, USDA NRCS 2010
B-40 Climate Change and Forest Biodiversity in Western Washington

40

Cascara (Frangula purshiana)

Ecology

Taxonomy and nomenclature Also known as Rhamnus purshiana

Description A deciduous, broadleaf, tall shrub or small tree, sometimes reaching 30 to 40 

ft (9 to 12 m) in height; a broad, bushy crown composed of ascending 

branches; broad-leaved and deciduous; thin, grayish brown bark

Distribution Southern British Columbia to northern California; primarily west of the 

Cascade Range but also occurs east to Idaho and western Montana

Successional stage Occurs as an understory species in early to mid-seral stages of conifer or 

hardwood forests; sometimes occurs in late seral stages on wet sites

Associated forest cover An understory species in a wide range of forest types in the coastal and 

interior Pacific Northwest; associates include Douglas-fir, western hemlock, 

western redcedar, Sitka spruce, red alder, Pacific silver fir, Pacific madrone, 

and Oregon white oak

Habitat Sites Moist, fertile coastal sites; lower mountain slopes; moist bottomlands; canyons 

east of the Cascade crest

Soils Prefers soils of moderate to high fertility, particularly nitrogen-rich soils

Moisture Tolerant of wet soils, flooding, and a highly fluctuating water table; tolerant of 

dry soils

Temperature Low frost tolerance; tolerant of heat

Shade tolerance Very shade-tolerant when young; moderately shade-tolerant at maturity

Interspecific 

interactions

Animal damage Browsed by deer in winter despite low palatability; fruits consumed by a 

variety of bird species; bears may break branches to reach fruit

Mycorrhizal 

fungi

Unpublished reports of mycorrhizal associates

Reproduction and Growth

Mode of reproduction Reproduces sexually and vegetatively through layering and sprouting; 

monoecious; vegetative reproduction less common

Reproductive phenology In Idaho, flowers from late May to early June, with fruit growth beginning in 

June; fruit mature by September; in California, flowers from April to July, with 

fruit maturing from July through September

Pollination Insect pollination has been observed in some locations

Seed Seed type Purplish-black drupe about 0.3 in (8 mm) in diameter; drupe contains 

approximately three seeds

Seed-bearing 

age

Unknown

Seed size/ 

weight

Seed comprises approximate 20 percent of fruit by weight; cleaned averages 

12,300 seeds per lb (27,100 seeds per kg) with a range of 5,000 to 19,000 
Climate Change and Forest Biodiversity in Western Washington B-41

41

seeds per lb (11,000 to 41,850 seeds per kg)

Seed longevity/ 

survivability

Unknown

Seed crop and 

frequency

A prolific seed producer, although seed production is lower when growing in 

an understory position

Seed 

dissemination

Time of year Fruits mature by September

Method and 

dispersal 

agents

Birds are the primary dispersal agent

Distance Unknown

Germination requirements Germination is relatively low; cold stratification required; germination 

increased by exposed mineral soil; germination greater in sunlight than in the 

understory

Vegetative phenology In Idaho, budswell occurred in late April, leafout occurred in May, and stem 

growth occurred from early May through July

Threats and Management Considerations

Insects and disease Low risk of serious damage

Harvest Some populations have been heavily harvested or extirpated for the medicinal 

value of cascara’s bark; larger trees were preferentially harvested

Fragmentation Widespread in western Washington, although its current distribution is likely 

influenced by historical harvesting practices

Fire Usually top-killed by fire; sprouts from root crown

NatureServe conservation status 

ranking

G4/G5: G4 Apparently Secure—Uncommon but not rare; some cause for longterm concern due to declines or other factors/G5 Secure—Common; 

widespread and abundant; range indicates some uncertainty about the exact 

status; concerns over rather intensive exploitation in considerable portions of 

the species’ range

Silvicultural considerations Usually regarded as a weed species in conifer plantations

References

Arno and Hammerly 2007, Habeck 1992b, USDA NRCS 2010
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42

Oregon Ash (Fraxinus latifolia)

Ecology

Description A medium-sized, deciduous, broadleaf tree typically reaching 60 to 80 ft (18 to 

24 m) in height; a narrow crown in dense stands and a broad, spreading 

crown where open-grown; opposite branchlets; self prunes rapidly; dark graybrown bark has deep, patterned fissures

Distribution From western Washington south through western Oregon to central California; 

in Washington, occurs from the Puget Sound region south, in lowland valleys 

west of the Cascade Range but not in the Olympic Range

Successional stage A pioneer and early seral species that regenerates after floods, windstorms, 

fire, or other disturbances create open habitat; replaced by more shadetolerant species such as bigleaf maple and conifers 

Associated forest cover Occurs with red alder, bigleaf maple, black cottonwood, Oregon white oak, 

and willows (Salix spp.); occasionally occurs in small, pure stands in western 

Washington

Habitat Sites Found in lowlands and river valleys, most often in riparian habitats; occurs 

frequently in bottomlands, swamps, wet meadows and swales

Soils May occur on a wide range of soils, but most often found on deep, rich alluvial 

soils including those that are poorly drained or seasonally flooded

Moisture Tolerant of flooding and seasonally saturated soils; occurs in Oregon and 

California where annual precipitation is as low as 20 in (510 mm)

Temperature Temperatures are generally mild within its range; tolerates temperatures to -8 

°F (-22 °C)

Shade tolerance Shade tolerance is low to intermediate

Interspecific 

interactions

Animal damage Browsed by deer and elk; seeds consumed by birds and squirrels

Mycorrhizal 

fungi

Other species in the same genus are associated with arbuscular mycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction is sexual (dioecious) and vegetative; stumps sprout vigorously 

Reproductive phenology Flowers appear at the same time as leaves in April or May

Pollination Wind-pollinated

Seed Seed type Oblong to elliptical, single, winged samaras, 1 to 2 in (2.5 to 5 cm) long, 

including the wing; ripens in August or September, turning light brown 

Seed-bearing 

age

Seed production begins around age 30 years

Seed size/ 

weight

Approximately 10,000 to 14,000 cleaned seeds per lb (22,000 to 31,000 per 

kg)
Climate Change and Forest Biodiversity in Western Washington B-43

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Seed longevity/ 

survivability

Unknown; reported to have persistent viability

Seed crop and 

frequency

An abundant annual seed producer where open-grown; produces heavy seed 

crops at 3- to 5-year intervals in forest stands

Seed 

dissemination

Time of year Seed dispersed in September and October

Method and 

dispersal 

agents

Winged samaras are dispersed by wind and are eaten by birds and squirrels

Distance Unknown

Germination requirements Cool, moist stratification required; germination medium to high; germination 

highest on moist or wet soils with significant organic matter; germination 

epigeal

Seedling survival Seedlings tolerant of drought; seedling growth rapid on rich soils; seedlings 

moderately shade-tolerant

Vegetative phenology Leaves appear in April or May

Threats and Management Considerations

Insects and disease A variety of insects and fungal pathogens have been reported on Oregon ash, 

although the extent and severity of resulting damage is not well-documented; 

the heart rot Perenniporia fraxinophilus is found in older trees; small weevils 

(Thysanocnemis spp.) may damage seed crops throughout the range of 

Oregon ash

Fire Typically occurs on wet sites where fire is less common; sprouts vigorously 

after trees are top-killed by fire 

Other damaging agents Very wind-firm

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Often planted as an ornamental

References

Arno and Hammerly 2007, Owston 1990, USDA NRCS 2010, Wallander 2008
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Rocky Mountain juniper (Juniperus scopulorum)

Ecology

Taxonomy and nomenclature Based on a recent genetic analysis, Adams (2007, 2010) identified the 

Juniperus scopulorum populations in the Puget Sound region and Olympic 

Range as a separate species, Juniperus maritima, found only in this area; 

because the descriptions presented here follow nomenclature of the USDA 

Plants Database, we treat J. scopulorum and J. maritima as a single species

Description An evergreen, coniferous shrub or small tree, occasionally reaching a height 

of 35 ft (10 m) or more; scale-like leaves and a ragged, bushy crown; a 

tapered stem with long branches; thin, reddish brown or grayish, fibrous bark

Distribution Throughout the mountains and foothills of interior British Columbia southward 

to Arizona and New Mexico; occurs from sea level to 9,000 ft (2,740 m); 

occurs on Vancouver Island and other Puget Sound islands and on the 

surrounding mainland

Successional stage Typically part of long-term seral or near-climax communities

Associated forest cover Often in isolated clumps or with Pacific madrone, Oregon white oak, red alder, 

western white pine, whitebark pine, trembling aspen, or Douglas-fir

Habitat Sites Wide ecological amplitude; occurs on a variety of sites and landforms 

including rocky bluffs and southern exposures, ravines, and valleys; in 

western Washington, Rocky Mountain juniper occurs close to the shore of 

Puget Sound on rocky sites characterized by granite and sand; in eastern 

Washington, it occurs on dry, rocky, mountainous sites

Soils Although it occurs on a wide range of soil types, it is often found on shallow, 

poorly developed, stony, alkaline soils; in the Puget Sound region it occurs on 

droughty soils derived from granite

Moisture Tolerant of extremely dry sites

Temperature Tolerant of growing-season frost; tolerant of heat

Shade tolerance Tolerates shade when young; shade-intolerant at maturity

Interspecific 

interactions

Animal damage Although palatability is poor, damage occurs when other sources of browse 

are limited; animals use trees as “rubbing posts”

Mycorrhizal 

fungi

No mycorrhizal associates have been reported for this species

Reproduction and Growth

Mode of reproduction Reproduction is sexual; dioecious; may be cultivated from cuttings

Reproductive phenology Pistillate flowers appear in late summer; pollination occurs the following April; 

seed cones reach maturity by November or December of the second year 

after pollination and remain on the tree until approximately 24 months postpollination; among Puget Sound populations of Rocky Mountain juniper, this 

period is only 14 to 16 months

Pollination Wind-pollinated
Climate Change and Forest Biodiversity in Western Washington B-45

45

Seed Seed type Globose to reniform berries 0.2 to 0.3 in (4 to 8 mm) in diameter; berries 

contain one to three seeds

Seed-bearing 

age

Seed production begins as early as age 10 to 20; peak seed production 

occurs between ages 50 and 200

Seed size/ 

weight

Averages 27,100 seeds per lb (59,700 seeds per kg); ranges from 18,000 to 

42,000 seeds per lb (39,700 to 92,600 seeds per kg)

Seed longevity/ 

survivability

Seeds may remain dormant for several years or longer

Seed crop and 

frequency

Prolific seed producer; seed crops every year; heavy crops every 2 to 5 years; 

production greatest for open-grown trees

Seed 

dissemination

Time of year Berries mature and fall from the tree in spring

Method and 

dispersal 

agents

Seeds are dispersed primarily by birds and less frequently by mammals; some 

seeds dispersed by gravity and surface runoff

Distance Dispersal is primarily by birds and is therefore influenced by their daily and 

migratory movements

Germination requirements Germination averages 22 to 45 percent; germination epigeal; seeds have both 

a seed-coat and a chemical dormancy; germination does not occur until 14 to 

16 months after seeds reach maturity

Seedling survival Seedling distribution is usually sparse; survival requires moisture often found 

in rock crevices or pockets; partial shade may assist establishment

Threats and Management Considerations

Insects and disease Insects and fungal pathogens not a serious problem; blight caused by 

Cercospora sequoiae is the most serious disease

Harvest Not a commercial timber species

Fragmentation Puget Sound populations are small and scattered; because populations 

apparently originate from seed dispersed by birds, Rocky Mountain juniper 

has a scattered distribution

Fire Vulnerable to damage from fire; seedlings, saplings, and small trees easily 

killed; larger trees survive surface fires

Other damaging agents Very resistant to windthrow

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Difficult to grow from seed owing to prolonged dormancy; may be propagated 

from cuttings; often planted for restoration and reclamation purposes, 

windbreaks, and as an ornamental

References

Adams 2007, Adams et al. 2010, Arno and Hammerly 2007, Klinka et al. 2000, Noble 1990, Scher 2002, USDA 

NRCS 2010
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46

Western crab apple (Malus fusca)

Ecology

Taxonomy and nomenclature Also known as Pyrus fusca and Malus diversifolia

Description A small, scraggly, deciduous, broadleaf tree, sometimes reaching 40 ft (12 m) 

in height; spreading branches with a rounded crown

Distribution Coastal Pacific Northwest from Alaska to northern California; elevations from 

sea level to 1,000 ft (300 m); occurs throughout western Washington but only 

as a minor component of vegetation communities 

Successional stage An early seral species

Associated forest cover Occurs with a variety of species; commonly found on sites also occupied by 

red alder, bigleaf maple, cascara, Oregon ash (Fraxinus latifolia), and Sitka 

willow (Salix sitchensis)

Habitat Sites Moist woods, swamps, edges of rivers, streams, estuaries, and lakes; 

brackish-water marshes; sites affected by ocean spray

Soils Moist soils; sandy to clayey in texture; prefers nutrient-rich wetland soils

Moisture Tolerant of prolonged soil saturation; intolerant of drought

Temperature Intolerant of extremely cold temperatures

Shade tolerance Moderately shade tolerant; best growth occurs in full sunlight

Interspecific 

interactions

Animal damage Attracts wildlife, providing food and cover; wildlife damage not reported

Mycorrhizal 

fungi

Other species in the genus Malus are associated with arbuscular mycorrhizae

Reproduction and Growth

Mode of reproduction Reproduces sexually and vegetatively; monoecious

Reproductive phenology Flowers in late spring, around May

Pollination Insect-pollinated

Seed Seed type Egg-shaped, yellow-green to red pomes about 0.4 to 0.6 in (10 to 15 mm) in 

diameter, formed in dense clusters

Seed-bearing 

age

Unknown

Seed size/ 

weight

24,500 cleaned seeds per lb (54,000 seeds per kg)

Seed longevity/ 

survivability

Unknown

Seed crop and 

frequency

Abundant seed producer
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Seed 

dissemination

Time of year Fruit ripens in October to November and is disseminated through the winter

Method and 

dispersal 

agents

Fruits consumed by birds, deer, elk, and bears

Distance Dependent upon animal vectors

Germination requirements Usually germinates in late winter; requires cold stratification

Genetics

Genetic diversity Above-average genetic diversity

Heterozygosity (He) 0.27

Threats and Management Considerations

Insects and disease Unknown

Harvest Not a commercial species

Fragmentation Widespread in western Washington

Fire Unknown

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Planted for restoration and wildlife purposes; tolerates wet and saline soils 

better than many associated species

References

Arno and Hammerly 2007, Dickson et al. 1991, Lyons 1999, USDA NRCS 2010
B-48 Climate Change and Forest Biodiversity in Western Washington

48

Engelmann spruce (Picea engelmannii)

Ecology

Description A large, evergreen conifer sometimes reaching 130 ft (40 m) in height; a 

narrow, conical crown that extends to the ground; dense limbs with hanging 

branchlets; thin, purplish or reddish bark with flaking scales

Distribution From British Columbia and Alberta south to Arizona and New Mexico, 

including all states from the Pacific Coast to the Rocky Mountains; occurs in 

Washington along the crest and eastern slope of the Cascade Range and in 

eastern parts of the state; most commonly found at elevations from 4,000 to 

6,000 ft (1,220 to 1,830 m); small populations occur in the northeastern 

Olympic Range

Successional stage A long-lived seral species found at all successional stages; sometimes occurs 

as a climax species

Associated forest cover Common associates at high elevations are subalpine fir, Pacific silver fir, 

mountain hemlock, and whitebark pine; common associates at low to midelevations are western white pine, Douglas-fir, grand fir, and lodgepole pine; 

sometimes occurs in pure stands

Habitat Sites Occurs on moist and cool sites, at all aspects at higher elevations and at 

northern and eastern aspects at lower elevations within its range

Soils Occurs on a variety of soils formed in residuum, glacial and lacustrine 

deposits, and volcanic materials; water availability is more important than soil 

physical properties

Moisture Tolerant of wet soils; shallow root system; low drought tolerance; requires a 

relatively large amount of soil water; transpiration rate is much higher than that 

of subalpine fir or lodgepole pine

Temperature High tolerance of growing-season frost; relatively intolerant of heat

Shade tolerance Moderately shade-tolerant; less shade-tolerant than its true fir (Abies) 

associates or mountain hemlock

Interspecific 

interactions

Animal damage Occasionally browsed; not a preferred species

Mycorrhizal 

fungi

Associated with both ectomycorrhizae and arbuscular mycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction is sexual and vegetative; monoecious, with ovulate cones in the 

upper crown and staminate cones in the lower crown; vegetative reproduction 

occurs through layering

Reproductive phenology Strobili formed in late April to early May; pollination occurs from late May at 

lower elevations to early July at higher elevations; cones mature in one 

season, ripening from August to early September

Pollination Wind-pollinated
Climate Change and Forest Biodiversity in Western Washington B-49

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Seed Seed type Cones 1 to 1.25 in (2.5 to 6.3 cm) long; small, winged seeds

Seed-bearing 

age

May begin seed production by age 15 to 40; production peaks between ages 

150 and 250

Seed size/ 

weight

135,000 seeds per lb (297,000 seeds per kg)

Seed longevity/ 

survivability

Seed viability is persistent

Seed crop and 

frequency

A moderate to good seed producer; large inter-annual and geographic 

variations in crop size; large seed crops occur every 2 to 5 years; some seed 

produced nearly every year

Seed 

dissemination

Time of year Most seedfall occurs during September and October; some seed continues to 

fall through winter

Method and 

dispersal 

agents

Seed primarily dispersed by wind

Distance Seed typically dispersed to 300 ft (90 m) or to 600 ft (180 m) when heavy seed 

crops occur

Germination requirements Seed viability relatively high compared to associated species; seeds 

germinate after snowmelt when seedbeds are moist and air temperature 

warms above 45 °F (7 °C); seeds germinate on many types of mineral and 

organic substrates; germination occurs at all light intensities although 40 to 60 

percent of full sunlight is optimal at high elevations

Seedling survival Seedlings germinating on exposed mineral soil or humus seedbeds are most 

likely to become established; seedlings are very vulnerable to drought and 

heat girdling in their first year owing in part to slow initial root penetration and 

heat sensitivity; drought mortality often remains significant through the first 5 

years

Genetics

Mating system High outcrossing rate

Outcrossing % (tm) 0.93

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.16

Geographic differentiation Weak differentiation based on molecular markers

Fst or Gst 0.02

Patterns of variation Engelmann spruce is considered intermediate with regard to adaptive 

strategy; both individuals and populations are suited to a broad range of 

environments, but populations still show habitat specificity
B-50 Climate Change and Forest Biodiversity in Western Washington

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Genetic analysis research results Intermountain west populations are differentiated for seedling characters with 

clines related to elevation and latitude; however, the clines are gentle, 

indicating low levels of genetic differentiation

Threats and Management Considerations

Insects and disease Moderately susceptible to damage from insects and disease; vulnerable to 

insects including spruce beetle (Dendroctonus rufipennis), western spruce 

budworm, white pine weevil, and the ragged sprucegall adelgid; susceptible to 

rots including Schweinitzii butt rot, tomentosus root rot, and red ring rot

Harvest A commercial timber species with wood qualities yielding quality pulp; a minor 

timber species in Washington

Fragmentation Widespread in the Cascade Range of Washington; small, disjunct populations 

in the northeastern Olympic Range

Fire Very susceptible to damage from surface and crown fires

Other damaging agents Relatively susceptible to windthrow

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Planting of nursery stock preferred over direct seedling for regeneration

References

Alexander and Shepperd 1990; Arno and Hammerly 2007; Klinka et al. 2000; Rajora and Dancik 2000; Rehfeldt 

1994a; Shea 1987, 1990; Uchytil 1991c; USDA NRCS 2010
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51

Sitka spruce (Picea sitchensis)

Ecology

Description A very large, evergreen conifer; the largest spruce species in the world, 

reaching 300 ft (90 m) in height on some sites; a wide, dense crown with 

hanging branchlets; thin, reddish-brown bark with large, loose scales

Distribution Occupies a narrow coastal zone from south-central Alaska to northern 

California; in Washington, this zone also includes the shores of Puget Sound, 

the lower portions of major rivers, and the broad coastal plain on the west side 

of the Olympic Peninsula; elevations from sea level to 2,000 ft (600 m)

Successional stage Both a pioneer and a climax species; a pioneer following disturbances on 

coastal sites; its presence is maintained in these forests owing to its longevity, 

its size, and its ability to regenerate in gaps

Associated forest cover Occurs with western hemlock and western redcedar, also with bigleaf maple, 

red alder, and black cottonwood; less frequently found in pure stands

Habitat Sites Moist, well-drained coastal sites with a heavy maritime influence; riparian 

zones; does not grow well in swampy areas; high tolerance of ocean spray 

and brackish water compared to associated species

Soils Deep, well-aerated soils; often found on alluvial soils of medium to coarse 

texture; best growth occurs on soils high in calcium, magnesium, and 

phosphorus

Moisture Restricted to a zone of high annual precipitation, fog, and cool, moist 

summers; drought-intolerant; requires abundant moisture year-round

Temperature Low heat and frost tolerances; occurs in a mild, maritime climate

Shade tolerance Shade-tolerant; less shade-tolerant than hemlock but more shade-tolerant 

than Douglas-fir

Interspecific 

interactions

Animal damage Incurs less animal damage than associated species; beaver dam flooding may 

cause mortality

Mycorrhizal 

fungi

Ectomycorrhizal inoculation increased seedling growth

Reproduction and Growth

Mode of reproduction Sexual and vegetative reproduction; monoecious; vegetative reproduction 

occurs through layering

Reproductive phenology Reproductive cycle spans two growing seasons; reproductive buds appear in 

early summer of first year; pollination occurs around May of the second year, 

7 to 8 weeks after dormancy is broken; timing depends on temperature; fruit 

ripens around August

Pollination Wind-pollinated

Seed Seed type Cones 2.5 to 4 in (6 to 10 cm) long contain small, winged seeds; a British 

Columbia study found an average of 7.2 seeds per cone; only 29 percent were 

viable
B-52 Climate Change and Forest Biodiversity in Western Washington

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Seed-bearing 

age

Seed production begins between ages 20 and 40

Seed size/ 

weight

210,000 seeds per lb (463,000 seeds per kg)

Seed longevity/ 

survivability

Seed viability was maintained in a trial in which cones were stored for 5 

months

Seed crop and 

frequency

Good seed crops occur every 3 to 5 years; growing-season moisture may 

affect seed crop in subsequent year

Seed 

dissemination

Time of year Seed dispersal begins around October and continues through spring; majority 

of seed released within first 6 weeks

Method and 

dispersal 

agents

Wind-dispersed

Distance Wind carries seed 100 ft (30 m) to 0.5 mi (0.8 km) depending on topography 

and other factors

Germination requirements Germination occurs on mineral and organic soils and on rotting logs; 

germination greatest in sunlight resulting from canopy gaps or disturbances 

such as windstorms

Seedling survival Survival greatest in open areas, on mineral soil seedbeds where soil drainage 

is adequate; survival often greater on rotting logs than on the forest floor

Genetics

Mating system High outcrossing rate

Outcrossing % (tm) 0.98

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.165

Geographic differentiation Weak differentiation based on molecular markers

Fst or Gst 0.08

Patterns of variation Strong patterns of differentiation for height, growth period, bud set, and cold 

injury (QST = 0.80), but not for growth rate and budburst (QST = 0.29)

Genetic analysis research results Southern populations (California) have higher growth and frost damage than 

northern (British Columbia) populations; clinal patterns related to climate, 

especially temperature variables; families within a single watershed in Alaska 

differed significantly in growth and phenology traits, genetic gradients were 

related to elevation, slope and aspect

Threats and Management Considerations

Insects and disease Highly susceptible to insect damage when young, particularly white pine 

weevil (Pissodes strobe) and spruce beetle (Dendroctonus rufipennis); low 

susceptibility to fungal pathogens
Climate Change and Forest Biodiversity in Western Washington B-53

53

Harvest Historically heavily logged, particularly during World Wars I and II

Fragmentation Widespread within its habitat

Fire Fires are infrequent in its hypermaritime habitat; stem is damaged by low- or 

high-intensity surface fires

Other damaging agents Windthrow

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Planted in the northwestern United States and in British Columbia

References

Arno and Hammerly 2007; Campbell et al. 1989; Chaisurisri and El-Kassaby 1994; Chaisurisri et al. 1994; Gapare 

and Aitken 2005; Gapare et al. 2005; Griffith 1992b; Harris 1990b; Klinka et al. 2000; Mimura and Aitken 2007a, 

2007b; USDA NRCS 2010; Yeh and El-Kassaby 1980
B-54 Climate Change and Forest Biodiversity in Western Washington

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Whitebark pine (Pinus albicaulis)

Ecology

Description A small or medium-sized evergreen conifer reaching 80 ft (25 m) or more in 

height on some sites; slow-growing and long-lived; often multi-stemmed; long 

branches form an irregular, upswept crown; occurs as a low shrub or 

krummholz form near timberline; grayish-brown, scaly bark

Distribution Two longitudinally oriented distributions; the coastal distribution reaches from 

the Coast Ranges of British Columbia through the Cascade Range and the 

Sierra Nevada; the interior distribution occupies the Rocky Mountains of 

British Columbia and Alberta southward through Idaho and Wyoming; in 

Washington, whitebark pine occurs in the Cascade and northeastern Olympic 

Ranges, primarily at elevations above 5,250 ft (1,600 m)

Successional stage A pioneer species at all elevations within its range; an early seral species at its 

lower elevations; a climax species around timberline; in the upper timberline 

zone it may be the sole climax species

Associated forest cover Occurs with subalpine fir, Engelmann spruce, lodgepole pine, mountain 

hemlock, and western white pine; pure whitebark pine stands occur at its 

highest elevations and on dry sites

Habitat Sites Exposed ridgetops and dry, rocky sites

Soils Found on a variety of soils types, although soils are generally rocky and poorly 

developed

Moisture Tolerates cool, droughty summer conditions; majority of precipitation occurs 

as snow; heavy snowpack is common

Temperature Tolerant of severe winter conditions; highly tolerant of frost; moderately 

tolerant of heat, although seedling may suffer heat damage

Shade tolerance Low to intermediate shade tolerance; less shade-tolerant than subalpine fir, 

Engelmann spruce, and mountain hemlock; more shade-tolerant than 

lodgepole pine but similar tolerance to western white pine

Interspecific 

interactions

Animal damage High level of predation by species that disperse seed including Clark’s 

nutcracker, pine squirrel (Tamiasciurus spp.), chipmunk (Tamias spp.), and 

deer mice (Peromyscus spp.)

Mycorrhizal 

fungi

Associated with endomycorrhizae and ectomycorrhizae including 

Cenococcum graniforme

Reproduction and Growth

Mode of reproduction Reproduces sexually and vegetatively; monoecious; vegetative reproduction is 

through layering, usually in its krummholz growth form

Reproductive phenology Reproductive cycles spans two growing seasons; pollination occurs from May 

to August of the first year depending on elevation, latitude, and temperature; 

fertilization occurs 13 months after pollination and female cones ripen in 

August or September of the second year

Pollination Wind-pollinated
Climate Change and Forest Biodiversity in Western Washington B-55

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Seed Seed type Egg-shaped cones 2 to 3.5 in (5 to 9 cm) long with large, wingless seeds

Seed-bearing 

age

Seed production begins about age 20 to 30 years; full production reached at 

age 60 to 100 years

Seed size/ 

weight

2,200 to 4,500 seeds per lb (4,850 to 9,900 seeds per kg)

Seed longevity/ 

survivability

Apparently the only North American pine (Pinus) with a seed bank; seed has 

been stored successfully at sub-freezing temperatures for 8 years

Seed crop and 

frequency

Individual trees produce large seed crops every 3 to 5 years; some seed 

produced every year at the stand level

Seed 

dissemination

Time of year Seeds are dispersed by Clark’s nutcracker when they ripen in the fall

Method and 

dispersal 

agents

Clark’s nutcracker is the primary dispersal agent; nutcrackers break open 

indehiscent cones using their beaks and then bury the seeds in shallow 

caches

Distance Many seeds cached within 1,640 ft (500 m) of source tree; emigrant 

nutcrackers cache seeds within 1.2 mi (2 km) of source trees; resident 

nutcrackers transport seeds an average of 6 mi (9.8 km) from source tree; 

some seeds have been transported as far as 18 mi (29 km)

Germination requirements Seed must complete embryonic development, which often occurs after it is 

cached by Clark’s nutcracker; stratification and seedcoat weathering required 

for germination; moist seedbed required; germination rate often low owing to 

these factors; germination epigeal

Seedling survival Seedlings consumed by many animals including pocket gophers, elk, Clark’s 

nutcracker and other bird species, and chipmunks; heat damage to unshaded 

seedlings may cause mortality

Vegetative phenology Most growth occurs in mid-summer; growth rate is generally slow, and very 

slow on cold sites

Genetics

Mating system Predominantly outcrossing but with moderate level of inbreeding present in 

some areas

Outcrossing % (tm) 0.73-0.88

Genetic diversity Genetic diversity average in Cascades; Olympic populations have somewhat 

lower diversity

Heterozygosity (He) 0.19 in Cascades, He = 0.16 in Olympics

Geographic differentiation Weak differentiation based on molecular markers but strong differentiation 

based on quantitative traits

Fst or Gst 0.04

Patterns of variation QST = 0.36-0.47 for cold adaptation traits, 0.07-0.14 for growth traits
B-56 Climate Change and Forest Biodiversity in Western Washington

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Genetic analysis research results Significant population variation found in most traits; cold adaptation traits 

correlated with winter temperature while growth traits correlated with growing 

season length; predominantly outcrossing but some individuals highly 

inbreeding, although inbreeding depression detected only in biomass; 

northern and interior populations have highest cold hardiness in fall but lowest 

in spring and vice versa in the south

Threats and Management Considerations

Insects and disease White pine blister rust, caused by Cronartium ribicola, is the most damaging 

pathogen; white pine blister rust increases susceptibility to mountain pine 

beetle, the most damaging insect; whitebark pine is affected to a much lesser 

extent by a number of other insects and fungal pathogens

Harvest Rarely harvested

Fragmentation Populations scattered owing to discontinuous distribution of habitat in highelevation terrain

Fire Fire benefits whitebark pine by reducing competition and creating new habitat 

in which it may establish; whitebark pine is more resistant to fire than its laterseral associates

Other damaging agents Potential damaging agents include landslides and dwarf mistletoe

NatureServe conservation status 

ranking

G3/G4: G3 Vulnerable—At moderate risk of extinction or elimination due to a 

restricted range, relatively few populations, recent and widespread declines, or 

other factors/G4 Apparently Secure—Uncommon but not rare; some cause for 

long-term concern due to declines or other factors; range indicates some 

uncertainty about the exact status; populations of whitebark pine are affected 

by white pine blister rust, mountain pine beetle, and succession resulting from 

decades of fire suppression

Silvicultural considerations Fire suppression has reduced regeneration of whitebark pine and increased 

the prevalence of shade-tolerant associates that overtop and shade whitebark 

pine; whitebark pine habitat is relatively inaccessible

References

Arno and Hammerly 2007; Arno and Hoff 1990; Aubry et al. 2008; Bonner and Karrfalt 2008; Bower and Aitken 2006, 

2007, 2008; Bower et al., n.d.; Bruederle et al. 1998; Howard 2002; Jorgensen and Hamrick 1997; Klinka et al. 2000; 

Krakowski et al. 2003; Lorenz et al. 2008; Lorenz and Sullivan 2009; Rehfeldt 2004; Richardson et al. 2002a, 2002b, 

2010; Rogers et al. 1999; Shoal and Aubry 2004; Shoal and Aubry 2006; USDA NRCS 2010; Ward et al. 2006; 

Warwell et al. 2006
Climate Change and Forest Biodiversity in Western Washington B-57

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Shore pine (Pinus contorta var. contorta)

Ecology

Taxonomy and nomenclature Two of the four varieties of lodgepole pine (Pinus contorta) are native to 

western Washington; Pinus contorta var. contorta (shore pine) grows in the 

coastal region, and Pinus contorta var. latifolia (lodgepole pine) is typically 

found on interior mountains; these two varieties overlap and intergrade from 

the Puget Sound region northward

Description A small, evergreen conifer reaching 20 to 50 ft (6 to 15 m) in height; stunted, 

frequently irregular crown with many branches often occurring to the ground; 

twisted stem with thick, grooved bark

Distribution Along the Pacific Coast from southeastern Alaska to northern California; 

usually occurs at elevations lower than 2,000 ft (600 m)

Successional stage An early seral species where it is replaced by Douglas-fir or other species; a 

climax species on many extreme sites where other species cannot grow

Associated forest cover Extensive pure stands in the northern part of its range; a component of mixed 

stands in the southern part of its range including Washington; forms thickets 

or groves in mixed stands with a number of species including Douglas-fir, 

western redcedar, Sitka spruce, western hemlock, and Oregon white oak

Habitat Sites Occurs in a maritime climate throughout its range; bogs and lowlands; poorly 

drained sites; poor-quality, disturbed sites; coastal dunes and seaside bluffs

Soils Poorly drained, deep organic soils; swamps; sandy or rocky coastal soils; 

glacial gravel; bedrock; hardpan; disturbed soils; frequent on very nutrientpoor sites

Moisture Tolerates very dry to very wet, seasonally flooded sites

Temperature Tolerant of heat; frost-tolerant

Shade tolerance Intolerant of shade

Interspecific 

interactions

Animal damage Seeds may be consumed by rodents

Mycorrhizal 

fungi

Associated with ectomycorrhizae and arbuscular mycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction is sexual; monoecious

Reproductive phenology Reproductive cycle lasts approximately 26 months; male and female strobili 

initiated in late summer; pollination occurs in May or June of the following 

growing season; fertilization occurs around June of the third year and seed 

development is completed by late summer

Pollination Wind-pollinated

Seed Seed type Cones 1.5 to 2 in (4 to 5 cm) long; small, winged seeds; cones usually 

nonserotinous
B-58 Climate Change and Forest Biodiversity in Western Washington

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Seed-bearing 

age

Seed production usually begins by 10 years of age

Seed size/ 

weight

135,000 seeds per lb (298,000 seeds per kg)

Seed longevity/ 

survivability

Cones are persistent, remaining on trees for years open or closed; seeds 

have remained viable for 17 years at sub-freezing temperatures

Seed crop and 

frequency

A prolific seed producer; large seed crops produced at 1- to 3-year intervals; 

some seed produced every year; seedfall in Oregon was measured at 14,000 

to 500,000 seeds per ac (35,000 to 1,2000,000 seeds per ha)

Seed 

dissemination

Time of year Seed from nonserotinous cones usually dispersed in late summer and fall and 

to a lesser extent in winter

Method and 

dispersal 

agents

Seed primarily dispersed by wind; intense sunlight or fire opens serotinous 

cones; some seed dispersed by Douglas squirrels (Tamiasciurus douglasi), 

other rodents, or birds

Distance Seeds are usually dispersed less than 200 ft (60 m), although strong winds 

may carry them much farther

Germination requirements Germination greatest in full sunlight on bare mineral soil or disturbed duff 

layer, assuming sufficient moisture; germination epigeal; stratification usually 

not necessary; germination rates high under favorable conditions

Seedling survival Germinants very sensitive to dry conditions during first few weeks; seedlings 

shallow-rooted in first year and prone to drought mortality; young seedlings 

are prone to frost-heaving; seedlings are poor competitors relative to other 

herbaceous and woody vegetation

Vegetative phenology Buds containing all the structures of the new shoots are formed throughout the 

previous growing season; these buds then begin to elongate around May; 

trees in coastal or mild climates often exhibit polycyclic shoot growth, with 

multiple periods of elongation during the growing season

Genetics

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.148

Geographic differentiation Weak genetic differentiation based on molecular markers

Fst or Gst 0.054

Patterns of variation Strong differentiation among varieties and populations within varieties based 

on morphometric traits

Genetic analysis research results Cone serotiny is absent or infrequent in this subspecies. Levels of gene flow 

among coastal populations are lower and therefore differentiation is high than 

var. latifolia. This variety likely persisted in multiple coastal refugia during 

glaciation
Climate Change and Forest Biodiversity in Western Washington B-59

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Threats and Management Considerations

Insects and disease Susceptible to insect and fungal damage; damaging agents include mountain 

pine beetle (Dendroctonus ponderosae), blister rust, gall rusts, stem rots, and 

stem cankers

Harvest Shore pine is small and forms many branches, making it a poor species for 

timber production

Fragmentation Widespread throughout its range

Fire Low resistance to damage from fire; regenerates well following fire, but fire is 

infrequent in its maritime habitat

Other damaging agents Dwarf mistletoe (Arceuthobium spp.) causes damage on a local scale

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Survives in saline coastal environments; used to stabilize soil and sand dunes

References

Anderson 2003; Arno and Hammerly 2007; Bonner and Karrfalt 2008; Cope 1993b; Despain 2001; Fazekas and Yeh 

2006; Godbout et al. 2008; Klinka et al. 2000; Kurz et al. 2008; Lotan and Critchfield 1990; Owens 2006; Perry 1978;

Perry and Dancik 1986; Rehfeldt et al. 2001; Rehfeldt et al. 1999; Rweyongeza et al. 2007; USDA NRCS 2010; Van 

Den Berg and Lanner 1971; Wagg et al. 2008; Wheeler and Guries 1982a, 1982b; Yang and Yeh 1993; Yeh et al. 

1985; Yeh and Layton 1979; Ying 1991; Ying and Liang 1994
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Lodgepole pine (Pinus contorta var. latifolia)

Ecology

Taxonomy and nomenclature Two of the four varieties of lodgepole pine (Pinus contorta) are native to 

western Washington; Pinus contorta var. contorta (shore pine) grows in the 

coastal region, and Pinus contorta var. latifolia (lodgepole pine) is typically 

found on interior mountains; these two varieties overlap and intergrade from 

the Puget Sound region northward

Description A small-to-medium, short-lived, evergreen conifer reaching 45 to 150 ft (13 to 

45 m) in height, depending on the site; a straight, slender stem and a narrow, 

thin crown; self prunes lower branches; thin, gray-brown, scaly bark 

Distribution One of the most widely distributed conifers in western North America; from 

southeastern Alaska to northwestern Mexico; from the Pacific Coast eastward 

to South Dakota; in Washington, most common on the eastern slope of the 

Cascade Range, although also present on the western slope; found at 

elevations from 1,500 to 11,500 ft (450 to 3,500 m) throughout its range

Successional stage An aggressive pioneer species frequently regenerating in single-aged stands 

after fire; replaced in less than 100 years by other conifer species on 

productive sites; a subclimax species on sites with periodic stand-replacing 

fire; a climax species on harsh sites where other conifers grow poorly or not at 

all

Associated forest cover Often found in pure stands, but also occurs in mixed stands with a wide 

variety of other conifers including Douglas-fir, grand fir, western white pine, 

ponderosa pine, mountain hemlock, Engelmann spruce, subalpine fir, and 

Pacific silver fir

Habitat Sites Occurs in western Washington at mid- to high elevations; tolerant of nearly all 

sites but most prevalent on sites where periodic stand-replacing fire occurs or 

where extreme conditions limit establishment of other species; occurs on 

rocky soils and steep slopes and ridges 

Soils Grows on nearly all soil types within its range; tolerates extreme conditions 

where other tree species cannot survive; often found on poorly developed, 

shallow, and nutrient-poor soils

Moisture Tolerates very dry to very wet, seasonally flooded sites

Temperature Tolerant of heat; frost-tolerant

Shade tolerance Intolerant of shade

Interspecific 

interactions

Animal damage Not a preferred browse species; damaged by porcupines feeding on bark

Mycorrhizal 

fungi

Associated with ectomycorrhizae and arbuscular mycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction is sexual; monoecious
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Reproductive phenology Reproductive cycle lasts approximately 26 months; male and female strobili 

initiated in late summer; pollination occurs in May or June of the following 

growing season; fertilization occurs around June of the third year and seed 

development is completed by late summer

Pollination Wind-pollinated

Seed Seed type Cones 1.5 to 2 in (4 to 5 cm) long; small, winged seeds; cone serotiny is a 

function of disturbance type; percentage of serotinous cones is greatest where 

stand-replacing fire is most frequent 

Seed-bearing 

age

Seed production usually begins between 5 and 15 years of age

Seed size/ 

weight

83,000 seeds per lb (183,000 seeds per kg)

Seed longevity/ 

survivability

Cones are persistent, remaining on trees for many years open or closed; 

seeds in closed cones in the tree canopy may remain viable for 80 years; 

seeds have remained viable for 20 years in storage at sub-freezing 

temperatures

Seed crop and 

frequency

A prolific seed producer; large seed crops produced at 1- to 3-year intervals; 

some seed produced every year; annual seed production in a nonserotinous 

stand was greater than 600,000 seeds per ac (1,500,000 seeds per ha)

Seed 

dissemination

Time of year Seed from nonserotinous cones usually dispersed in late summer and fall and 

to a lesser extent in winter

Method and 

dispersal 

agents

Seed primarily dispersed by wind; intense sunlight or fire opens serotinous 

cones; some seed dispersed by Douglas squirrels (Tamiasciurus douglasi), 

other rodents, or birds

Distance Seeds are usually dispersed less than 200 ft (60 m), although strong winds 

may carry seeds much further

Germination requirements Germination greatest in full sunlight on bare mineral soil or disturbed duff 

layer, assuming sufficient moisture; germination epigeal; stratification usually 

not necessary; germination rates high under favorable conditions; laboratory 

germination was 65 to 90 percent

Seedling survival Germinants very sensitive to dry conditions during first few weeks; seedlings 

shallow-rooted in first year and prone to drought mortality; young seedlings 

are prone to frost-heaving; seedlings are poor competitors relative to other 

herbaceous and woody vegetation

Vegetative phenology Buds containing all the structures of the new shoots are formed throughout the 

previous growing season; these buds then begin to elongate around May; 

trees in coastal or mild climates often exhibit polycyclic shoot growth, with 

multiple periods of elongation during the growing season

Genetics

Mating system Predominantly outcrossing with high outcrossing rate

Outcrossing % (tm) 0.95
B-62 Climate Change and Forest Biodiversity in Western Washington

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Genetic diversity Average genetic diversity

Heterozygosity (He) 0.156

Geographic differentiation Weak genetic differentiation based on molecular markers

Fst or Gst 0.036

Patterns of variation Strong differentiation among varieties and populations within varieties based 

on morphometric traits

Genetic analysis research results There is a relationship between geographic and genetic distance for this 

variety; recent interpretations of genetic and paleobotanical evidence seems 

to indicate a single glacial refugium south of the ice sheet and subsequent 

northward migration

Threats and Management Considerations

Insects and disease Suffers extensive damage from insects and fungi, particularly mountain pine 

beetle(Dendroctonus ponderosae); also damaged by pine engraver, northern 

lodgepole pine needleminer, blister rust, gall rusts, stem rots, and stem 

cankers

Harvest An important commercial species in the Pacific Northwest, especially in British 

Columbia

Fragmentation Widespread throughout its range in western Washington

Fire Low resistance to damage from fire; regenerates rapidly following fire

Other damaging agents Dwarf mistletoe (Arceuthobium spp.) causes damage

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Natural regeneration following fire is sometimes too dense, and growth 

subsequently stagnates

References

Anderson 2003; Arno and Hammerly 2007; Bonner and Karrfalt 2008; Cope 1993b; Despain 2001; Fazekas and Yeh 

2006; Godbout et al. 2008; Klinka et al. 2000; Kurz et al. 2008; Lotan and Critchfield 1990; Owens 2006; Perry 1978;

Perry and Dancik 1986; Rehfeldt et al. 2001; Rehfeldt et al. 1999; Rweyongeza et al. 2007; USDA NRCS 2010; Van 

Den Berg and Lanner 1971; Wagg et al. 2008; Wheeler and Guries 1982a, 1982b; Yang and Yeh 1993; Yeh et al. 

1985; Yeh and Layton 1979; Ying 1991; Ying and Liang 1994
Climate Change and Forest Biodiversity in Western Washington B-63

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Western white pine (Pinus monticola)

Ecology

Description A medium-to-large, evergreen conifer, occasionally surpassing 200 ft (60 m) in 

height, but usually less than 120 ft (37 m) tall; crown is sparse with branches 

in distinct whorls; smooth grayish bark forming rectangular plates by maturity

Distribution Coastal and interior distributions in the Pacific Northwest; coastal distribution 

extends from southwestern British Columbia to Tulare County, California; 

interior distribution extends from southeastern British Columbia to northern 

Idaho; in Washington, occurs from the coast to the Cascade Range and in the 

eastern part of the state; occurs in the Olympic Range from sea level to 1,800 

ft (550 m) elevation; occurs in the Cascade Range at elevations below 3,000 ft 

(900 m)

Successional stage Establishes after major disturbances including stand-replacing fires; may 

persist through all stages of secondary succession

Associated forest cover Associated with numerous species including Pacific silver fir, grand fir, 

subalpine fir, noble fir, western hemlock, western redcedar, whitebark pine, 

and Engelmann spruce

Habitat Sites Most often occurs on moist sites on mountain slopes

Soils Occurs on a wide range of soil parent materials and textures; most abundant 

on poor sites where it is a strong competitor

Moisture Tolerant of wet soils and periodic flooding; tolerant of heavy snowpack; low 

drought tolerance

Temperature Moderate to high frost tolerance; relatively tolerant of heat

Shade tolerance Intermediate in shade tolerance relative to associated species

Interspecific 

interactions

Animal damage Low palatability as browse; seeds consumed by squirrels and mice

Mycorrhizal 

fungi

Associated with ectomycorrhizae and arbuscular mycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction sexual; monoecious

Reproductive phenology Reproductive cycle lasts approximately 26 months; 15 months from pollination 

to seed maturity; pollen-cone buds differentiate around August; seed-cone 

buds differentiate around April of the year 2; flowering occurs around June, 8 

weeks after dormancy is broken; fertilization occurs in year 3, approximately 

12 months after pollination; seeds mature within 3 months of fertilization 

Pollination Wind-pollinated

Seed Seed type Cones 6 to 11 in (15 to 28 cm) long, containing single-winged seeds

Seed-bearing 

age

Production of seed cones begins around age 10 to 15 years, and pollen cones 

are produced a few years later;
B-64 Climate Change and Forest Biodiversity in Western Washington

64

Seed size/ 

weight

Seed weight ranges from 14,000 to 32,000 seeds per lb (30,900 to 70,500 

seeds per kg) and averages 27,000 seeds per lb (59,000 seeds per kg)

Seed longevity/ 

survivability

Seed viability 40 percent after one winter, 25 percent after the second winter, 

and less than 1 percent after 3 and 4 years; stored under sub-freezing 

conditions, seed remains viable for at least 20 years

Seed crop and 

frequency

Heavy crops every 3 to 4 years; some cones produced nearly every year

Seed 

dissemination

Time of year Seeds mature from mid-August to September depending on site and summer 

temperatures

Method and 

dispersal 

agents

Seeds dispersed by wind, and to a lesser extent, by squirrels, mice, and birds

Distance Most seeds fall within 390 ft (120 m) of source tree; some seeds travel more 

than 2,600 ft (800 m)

Germination requirements Requires a stratification period of 30 to 120 days under cold, moist conditions; 

dormancy likely controlled by seed coat, seed membrane, and embryo 

physiology; mineral soil increases germination; germination often occurs while 

surface soils are wet following snowmelt; strong genetic component to 

germination rate, with high family heritability; germination epigeal

Seedling survival High mortality during first growing season owing to fungal pathogens, drought, 

heat, insects, birds, and rodents; on harsh sites, partial shade increases 

establishment; once established, growth best in full sunlight

Vegetative phenology Height and radial growth begins in May or June depending on latitude, 

elevation, and aspect; shoot buds formed during previous spring and summer

Genetics

Mating system Predominantly outcrossing with high outcrossing rate

Outcrossing % (tm) 0.98

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.147

Geographic differentiation Moderate genetic differentiation based on molecular markers

Fst or Gst 0.124

Patterns of variation Population variation in quantitative traits within the northern and southern 

regions is weak or non-existent; western white pine is considered a 

“generalist” species with broad climate and environmental tolerances
Climate Change and Forest Biodiversity in Western Washington B-65

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Genetic analysis research results Research has indicated two wide-ranging “populations” of western white pine; 

a broad “northern” population (Rocky Mountains, northern Cascades, and 

northern coastal areas) that have generally high growth potential and low cold 

hardiness, and a “southern” population in the Sierra Nevada with low growth 

potential and high cold hardiness; populations in the central and southern 

Cascades are arranged along a steep latitudinal gradient that connects the 

northern and southern population

Threats and Management Considerations

Insects and disease Moderately susceptible to insect damage, primarily from mountain pine beetle 

and pine engraver; highly susceptible to fungal pathogens, of which the nonnative white pine blister rust is the most devastating; seedlings with increased 

resistance to white pine blister rust have been planted since 1970

Harvest A valuable timber species prized for the quality of its wood; heavily logged 

since the late 1800s 

Fragmentation In its coastal distribution, western white pine often occurs scattered throughout 

forests dominated by other species

Fire A fire-dependent species, its extent decreased by fire suppression; high level 

of natural regeneration following stand-replacing fire; young trees often killed 

by fire; mature trees moderately resistant to fire damage

Other damaging agents Pole blight led to extensive damage during the 1900s, caused in part by 

extreme weather conditions; pole blight is not currently a major cause of 

mortality

NatureServe conservation status 

ranking

G4/G5: G4 Apparently Secure—Uncommon but not rare; some cause for longterm concern due to declines or other factors/ G5 Secure—Common; 

widespread and abundant; range indicates some uncertainty about the exact 

status; populations of western white pine are affected by white pine blister rust 

and several species of bark beetles

Silvicultural considerations West of the Cascade Range, the lack of stand-replacing disturbance is leading 

to a decline of western white pine; the prevalence of western white pine was 

greatly diminished during the 1900s by heavy logging, extensive wildfires, 

fungal diseases, and bark beetles

References

Arno and Hammerly 2007, Bishaw et al. 2003, Bonner and Karrfalt 2008, El-Kassaby et al. 1993, El-Kassaby et al. 

1987, Graham 1990, Griffith 1992c, Kim et al. 2003, Kinloch et al. 1999, Klinka et al. 2000, Mehes et al. 2009, Owens 

2004, Rehfeldt et al. 1984, Richardson et al. 2009, Steinhoff et al. 1983, USDA NRCS 2010
B-66 Climate Change and Forest Biodiversity in Western Washington

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Ponderosa pine (Pinus ponderosa)

Ecology

Taxonomy and nomenclature The variety of ponderosa pine occurring in Washington is Pinus ponderosa

var. ponderosa; the other recognized variety is interior ponderosa pine (Pinus 

ponderosa var. scopulorum)

Description A medium-to-large, evergreen conifer, often reaching 130 ft (40 m) in height; 

an open, conical crown with long branches bearing tufts of long needles; bark 

composed of large, scaly, orange-brown plates

Distribution Occurs in the Pacific Northwest from southern British Columbia through 

California; other varieties of the species occur throughout the western United 

States; occurs in Washington from 330 to 4,950 ft (100 to 1510 m), primarily 

east of the Cascade crest; occurs to a limited extent in south Puget Sound 

lowlands and on Mount Rainier; stands on the Olympic Peninsula were 

planted; although not formally described, ponderosa pine west of the Cascade 

Range in the Pacific Northwest, and throughout nearly all of California, is also 

known as Pinus ponderosa var. benthamiana

Successional stage An early seral species on higher-elevation or relatively moist sites, replaced by 

more shade-tolerant species; a climax species on harsh sites where other tree 

species cannot establish; on intermediate sites, ponderosa pine depends on 

recurring fire to maintain its dominance

Associated forest cover Occurs in pure and mixed stands; succeeds to Douglas-fir, true firs, and 

lodgepole pine on moist sites; in climax stands, may occur with Rocky 

Mountain juniper, quaking aspen, lodgepole pine, or Oregon white oak; pure

climax stands consist of a mosaic of small, even-aged groups

Habitat Sites Occurrence heavily influenced by its regeneration after fire, its fire tolerance at 

maturity, and its tolerance of sites too dry for other trees

Soils Occurs on a wide range of soil types; where moisture limits the presence of 

trees, its occurrence depends on soil moisture availability; in Washington, 

coarse-textured, sandy soils are more likely sites than clayey soils because 

grass and shrubs dominate the latter sites

Moisture High tolerance of seasonal drought and very dry sites; tolerant of flooding

Temperature Highly tolerant of heat; moderately tolerant of frost

Shade tolerance Intolerant of shade; often regenerates in even-aged groups or stands after fire

Interspecific 

interactions

Animal damage Seeds consumed by small mammals and birds; a high proportion of seeds 

may be consumed in years of small crops; seedlings browsed by deer; 

seedlings may be damaged by rabbits or gophers

Mycorrhizal 

fungi

Ectomycorrhizal fungi have been reported on ponderosa pine

Reproduction and Growth

Mode of reproduction Reproduction is sexual; monoecious

Reproductive phenology Reproductive cycle spans three growing seasons; reproductive buds initiated 
Climate Change and Forest Biodiversity in Western Washington B-67

67

in year 1; pollination occurs between April and June of year 2; seeds ripen in 

late August or September of year 3

Pollination Wind-pollinated

Seed Seed type Cones 3 to 6 in (8 to 15 cm) long; average number of seeds per cone varies 

by region, with 31 in Arizona and 70 in California

Seed-bearing 

age

Cone production begins as early as age 7 years; seed production reaches its 

maximum level around age 60 years

Seed size/ 

weight

Cleaned seeds vary from 6,900 to 23,000 seeds per lb (15,200 to 50,700 

seeds per kg) and average 12,000 seeds per lb (26,500 seeds per kg)

Seed longevity/ 

survivability

Seed stored at sub-freezing temperatures remained viable for 17 years

Seed crop and 

frequency

Heavy cone crops produced every 4 to 5 years in the Pacific Northwest; in a 

heavy seed year 345,000 seeds per ac (850,000 seeds per ha) may be 

dropped

Seed 

dissemination

Time of year Cones open in August or September and most seed is dropped by November

Method and 

dispersal 

agents

Seeds dispersed by wind and, to a lesser extent, animals including Clark’s 

nutcracker

Distance Most seed falls within 100 ft (30 m) of the source tree; a small amount of seed 

falls beyond 400 ft (120 m) of the source

Germination requirements Greatest regeneration results from a heavy seed crop, exposed mineral soil, 

and favorable growing-season weather; germination reduced by moisture 

stress; insects such as the ponderosa pine cone beetle (Conophthorus

ponderosae) and the pine seed chalcid (Megastigmus albifrons) may destroy 

seed before germination; germination epigeal

Seedling survival Survival reduced by moisture stress and competing vegetation; frost and high 

soil temperatures may cause mortality; seedlings may be destroyed by 

gophers or rabbits; seedlings can survive very dry conditions by reducing 

transpiration rates and vigorously extending root systems, including the 

taproot

Vegetative phenology With increasing elevation, height growth begins later in the year and growingseason length is shorter; growth rate during the growing season does not 

change with elevation; radial growth begins about one month before height 

growth

Genetics

Mating system Predominantly outcrossing with high outcrossing rate

Outcrossing % (tm) 0.95

Genetic diversity Above-average genetic variation

Heterozygosity (He) 0.23

Geographic differentiation Weak genetic differentiation based on molecular markers
B-68 Climate Change and Forest Biodiversity in Western Washington

68

Fst or Gst 0.75

Patterns of variation Strong population differentiation based on quantitative traits; ponderosa pine 

is considered intermediate with regard to adaptive strategy; both individuals 

and populations are suited to a broad range of environments, but populations 

still show habitat specificity

Genetic analysis research results Inland Northwest populations differed for seedling growth and shoot 

elongation traits; differences followed relatively steep clines in elevation and 

gentle clines in latitude and longitude

Threats and Management Considerations

Insects and disease Moderately susceptible to damage from insects and fungal pathogens; 

mountain pine beetles (Dendroctonus spp.), including (D. brevicomis), are the 

most damaging insects; beetles are a vector for blue stain fungus; pine 

engraver beetles (Ips spp.) also cause extensive damage; ponderosa pine is 

susceptible to numerous fungal pathogens, including western gall rust 

(Endocronartium harknessii) and root and butt rots

Harvest Ponderosa pine is planted and harvested east of the Cascade crest

Fragmentation Widespread east of the Cascade crest; isolated populations occur on Mount 

Rainier and in the southeastern part of the Puget Sound region

Fire Ponderosa pine evolved under a regime of frequent fire that favored it over 

other species such as Douglas-fir and true firs that are less tolerant of fire; 

ponderosa pine seedlings are killed by fire, but large trees survive surface 

fires owing to thick bark and self-pruning of low branches; severe fires may kill 

trees via crown scorch

Other damaging agents Dwarf mistletoes (Arceuthobium spp.) cause a significant amount of damage; 

heavy, wet snow may damage young trees; high ozone levels may cause 

foliar damage

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations The structure of most ponderosa pine stands has been dramatically changed 

by fire suppression over the past century; formerly open, park-like stands now 

contain numerous small trees of ponderosa pine and other species; harvest of 

large trees has contributed to younger, denser stands; dense stands are less 

vigorous and more prone to disease and crown fire

References

Agee 1993; Arno and Hammerly 2007; Bonner and Karrfalt 2008; Carey et al. 1997; DeLucia et al. 1994; Gooding 

1998; Habeck 1992a; Klinka et al. 2000; Mitton et al. 1981; Niebling and Conkle 1990; Oliver and Ryker 1990; Owens 

and Blake 1985; Rehfeldt 1991; Rotach 1997; Rygiewicz et al. 1997; Sorensen 1994a, 1994b; USDA NRCS 2010
Climate Change and Forest Biodiversity in Western Washington B-69

69

Black cottonwood (Populus balsamifera ssp. trichocarpa)

Ecology

Taxonomy and nomenclature Also known as Populus trichocarpa; one of two subspecies of Populus 

balsamifera

Description A large, deciduous, broadleaf tree reaching heights of 160 to 200 ft (50 to 60 

m); crown is broad and spreading when open-grown, but narrow in a closed 

canopy; few low branches; deeply furrowed, gray bark

Distribution From Alaska’s Kenai Peninsula to Baja, California; from the Pacific Coast east 

to Montana, Wyoming, and Utah; occurs from sea level to 5,000 ft (1,500 m)

elevation in the Pacific Northwest; found at lower elevations throughout 

western Washington and on moist sites in eastern Washington

Successional stage A fast-growing pioneer and early seral species found on disturbed sites

Associated forest cover Often found on alluvial sites with willows (Salix spp.), red alder, Sitka spruce, 

and bigleaf maple; may form pure stands as a pioneer but associates with 

conifers and other hardwoods in subsequent seral stages; found with 

Douglas-fir, western hemlock, western redcedar, grand fir, black hawthorn, 

cherry (Prunus spp.), and Oregon ash; east of the Cascade Range, 

associated with western white pine, ponderosa pine, Douglas-fir, quaking 

aspen, and Douglas maple

Habitat Sites Most prevalent on low-elevation, alluvial sites and in disturbed areas in 

western Washington; occurs in valleys and canyon bottoms, riparian zones, 

and other moist sites in central and eastern Washington

Soils Most often occurs on the deep alluvial silts and sands of floodplains, but also 

found on upland sites where moisture is sufficient; occurs on soils of moderate 

to high fertility; best growth occurs on well-drained soils

Moisture Tolerant of flooding and sediment deposition; tolerant of a fluctuating water 

table; intolerant of drought; intolerant of brackish water

Temperature Moderate frost tolerance; moderately tolerant of heat

Shade tolerance Very intolerant of shade

Interspecific 

interactions

Animal damage Voles, mice, and rabbits may damage seedlings; occasional browse damage 

from ungulates

Mycorrhizal 

fungi

Recently established or flooded trees may be associated with arbuscular 

mycorrhizae, although black cottonwood is more typically associated with 

ectomycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction is sexual and vegetative; typically dioecious; regenerates 

vegetatively from stump sprouts, from fragments of branches, and 

occasionally from root sprouts

Reproductive phenology Flowers between early March and late May; prior to flowering, the next year’s

inflorescences begin to develop at leaf nodes
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Pollination Wind-pollinated

Seed Seed type Catkins 3 to 8 in (8 to 20 cm) long contain capsules with 30 to 50 seeds in 

each; seeds have long, white hairs

Seed-bearing 

age

Seed production begins by age 10

Seed size/ 

weight

95,000 to 190,000 seeds per oz (3,300 to 6,700 seeds per g)

Seed longevity/ 

survivability

Initial viability high; under natural conditions, seed remains viable for less than 

1 month; remains viable for at least 1 year in storage; storage temperatures 

should be between -11 and 23 °F (-24 and -5 °C)

Seed crop and 

frequency

Abundant seed crop produced every year

Seed 

dissemination

Time of year By late May to late June

Method and 

dispersal 

agents

Seed is dispersed by wind and water

Distance Seed may be transported miles (kilometers) by wind or water

Germination requirements Best seedbed is exposed mineral soil or new alluvium; seedbed moisture is 

vital to establishment; germination epigeal

Seedling survival Major causes of mortality and damage are overtopping vegetation, insufficient 

moisture during the first month after germination, late or early frosts, and 

damage from rodents

Vegetative phenology Leaf growth initiated after spring flowering; shoot elongation and leaf growth 

continues through the growing season

Genetics

Genetic diversity Low genetic diversity

Heterozygosity (He) 0.06

Geographic differentiation Weak genetic differentiation

Fst or Gst 0.063

Patterns of variation Morphological traits exhibit abundant genetic diversity

Genetic analysis research results Seedling common garden studies showed significant variation among 

populations for numerous traits such as survival, growth, leaf morphology, 

crown morphology, phenology, and rust incidence; differences were related to 

moisture conditions (mesic vs. xeric) and temperature (upper vs. lower canyon 

positions)

Threats and Management Considerations

Insects and disease Low susceptibility to insect damage and fungal pathogens; a variety of fungal 
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diseases including leaf rust (Melampsora spp.) have been observed in 

plantations

Harvest Not a major timber species in natural stands; hybrids established in 

plantations 

Fire Highly susceptible to damage and top-kill from fire; sprouts following top-kill; 

establishes from seed after fire

Other damaging agents Ice storms and heavy snowfall may cause significant damage; top damage 

from wind is common

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Clones of hybrid Populus grown for pulp, veneer, and lumber production; 

planted as a windbreak; often planted from cuttings

References

Arno and Hammerly 2007; Bergha et al. 2003; Boes and Strauss 1994; Bonner and Karrfalt 2008; DeBell 1990; 

Dunlap et al. 1994, 1995; Dunlap and Stettler 1996; Gornall and Guy 2007; Klinka et al. 2000; Steinberg 2001; Taylor 

and Boss 1975; USDA NRCS 2010; Weber and Stettler 1981
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Quaking aspen (Populus tremuloides)

Ecology

Description A small- to medium-sized, deciduous, broadleaf tree reaching 50 to 60 ft (15 

to 18 m) in height; a narrow, domed crown with slender, bent limbs; smooth, 

thin, whitish bark

Distribution Widest distribution of any native tree species in North America, from western 

Alaska across Canada to the Atlantic coast; occurs in the northern hardwood 

forests of the United States and throughout the Rocky Mountains south to 

Mexico, at increasing elevations at lower latitudes; less prevalent in the Pacific 

Northwest and California; in Washington, occurs in scattered locations west of 

the Cascade, as low as sea level in the Puget Sound region; much more 

common in Washington east of the Cascade crest

Successional stage An aggressive pioneer species; maintains dominance where wildfire regularly 

occurs; a fire climax species in some locations; in the absence of fire, 

succeeds to shade-tolerant conifers

Associated forest cover Associated with numerous species throughout its range; also occurs in pure 

stands and groves; east of the Cascade crest in Washington, quaking aspen 

occurs with scattered ponderosa pine and Douglas-fir

Habitat Sites Found on a variety of sites, where soil moisture is not limiting; east of 

Washington’s Cascades, occurs in moist meadows, canyons, avalanche 

chutes, and riparian zones

Soils Found on numerous soil types; requires sufficient drainage and soil moisture, 

typically with a water table between 2 and 8 ft (0.6 and 2.5 m) below the 

surface

Moisture Occurrence is limited to sites with adequate drainage; does not tolerate longterm flooding; low tolerance of drought; drought stress lowers resistance to 

insects and disease

Temperature High frost tolerance; moderately tolerant of high temperatures

Shade tolerance Very intolerant of shade

Interspecific 

interactions

Animal damage Occasional browse damage and girdling by ungulates and small mammals

Mycorrhizal 

fungi

Roots are ectomycorrhizal

Reproduction and Growth

Mode of reproduction Sexual and vegetative reproduction; primarily dioecious; commonly 

regenerates by sprouting from its vigorous, spreading root system; this 

sprouting results in large colonies of genetically identical stems

Reproductive phenology Flowers in April or May; fruiting catkins reach maturity in May or June, 4 to 6 

weeks after flowering; timing of flowering is influenced by air temperature

Pollination Wind-pollinated
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Seed Seed type Catkins approximately 4 in (10 cm) long; catkins contain several dozen 

capsules, each containing approximately 10 seeds; seeds surrounded by tufts 

of silky hairs

Seed-bearing 

age

Flowers at age 2 to 3 years; large seed crops begin between ages 10 to 20 

years; seed production reaches a maximum at 50 years of age

Seed size/ 

weight

Cleaned seeds average 156,000 to 250,000 seeds per oz (5,500 to 8,000 

seeds per g)

Seed longevity/ 

survivability

Under favorable conditions, seeds remain viable for 2 to 4 weeks after 

reaching maturity; storage tests have produced varied results, but seed should 

be stored between -11 and 23 °F (-24 and -5 °C)

Seed crop and 

frequency

Heavy seed crops every 4 to 5 years; light seed crops in other years

Seed 

dissemination

Time of year Seeds dispersed beginning a few days after they ripen in May or June; 

dispersal continues for 3 to 5 weeks

Method and 

dispersal 

agents

Seeds dispersed by wind and water

Distance Seeds carried by wind for distances of 1,600 ft (500 m) to several miles 

(kilometers) 

Germination requirements Seeds germinate within days of dispersal; germination requires a watersaturated substrate; bare mineral soil is best seedbed; seeds may germinate 

underwater or in the dark; seed viability 80 to 95 percent; germination epigeal

Seedling survival Seedling mortality is high; survival reduced by insufficient moisture, high soil 

temperatures, the brief period of seed viability, and fungal pathogens; natural 

thinning of dense, young stands is rapid, whether stems are of seed or sprout 

origin

Vegetative phenology Leaf growth initiated after spring flowering; shoot elongation and leaf growth 

continues through the growing season

Genetics

Genetic diversity Above-average genetic diversity

Heterozygosity (He) 0.32

Geographic differentiation Weak genetic differentiation based on molecular markers

Fst or Gst 0.03

Patterns of variation Strong population differentiation in phenotypic traits

Genetic analysis research results Substantial phenotypic variation has been found in both field and common 

garden studies; populations throughout the range in the western United States 

varied in leaf size and shape, a trail that was strongly correlated with latitude; 

while high levels of genetic diversity have been observed in quaking aspen, it 

also commonly grows as large clonal stands, some of which are thought to be 

tens of thousands of years old and potentially the largest living organisms on 
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74

earth, covering dozens of hectares

Threats and Management Considerations

Insects and disease Low susceptibility to insect damage; although many defoliating insects attack 

quaking aspen, damage is usually not serious; quaking aspen is moderately 

susceptible to damage from a wide variety of fungal pathogens including butt 

and root rots, cankers, shoot and leaf blight, leaf spot, and leaf rust

Harvest A fast-growing species capable of producing timber under even-aged 

silvicultural systems in the inland West; not an important timber species in 

Washington

Fragmentation Populations are scattered and infrequent in western Washington

Fire Highly susceptible to fire damage; fires kill trees or damage them to an extent 

that fungal pathogens can exacerbate the injury; fires may kill or damage 

shallow roots; quaking aspen regenerates vigorously following stand-replacing 

fire

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations The combination of fire suppression and grazing has reduced the extent of 

aspen in the western United States

References

Arno and Hammerly 2007, Barnes 1975, Bonner and Karrfalt 2008, De Woody et al. 2009, Howard 1996, Jelinski and 

Cheliak 1992, Kanaga et al. 2008, Klinka et al. 2000, Namroud et al. 2005, Ostry and Anderson 2009, Perala 1990, 

Rehfeldt et al. 2009, St. Clair et al. 2009, USDA NRCS 2010, Yeh et al. 1995
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Bitter cherry (Prunus emarginata)

Ecology

Taxonomy and nomenclature There are two recognized varieties of bitter cherry: Prunus emarginata var. 

mollis, the variety described here, is a small tree occurring west of the 

Cascade crest, and Prunus emarginata var. emarginata is a shrub found east 

of the Cascade crest

Description A small, short-lived, deciduous, broadleaf tree reaching 50 ft (15 m) or more in 

height; spreading and ascending branches; smooth, reddish-brown bark

Distribution From British Columbia to southern California; in Washington, widespread west 

of the Cascade Range from sea level to 3,000 ft (900 m) elevation; found most 

often in ponderosa pine ecosystems east of the Cascades

Successional stage An early seral species; declines in frequency as the canopy closes; scattered 

in young hardwood and conifer forests

Associated forest cover A minor component of numerous early seral cover types; colonizes open 

areas; in eastern Washington, associates include Douglas maple, Scouler’s 

willow, and chokecherry; may occur in dense, pure stands

Habitat Sites Typically occurs on moist, low- to mid-elevation sites; often found near water; 

requires at least partial shade on dry, exposed slopes

Soils Occurs on loamy, sandy, and gravelly soils; often found on nutrient-poor and 

acidic soils

Moisture Most often occurs on moist soils; tolerant of flooding and a fluctuating water 

table; infrequent on dry sites

Temperature Moderately tolerant of heat; frost damage typically not a problem

Shade tolerance Tolerant of partial shade; grows best in full sunlight

Interspecific 

interactions

Animal damage Commonly browsed by deer and elk

Mycorrhizal 

fungi

Other species in the genus Prunus are associated with arbuscular 

mycorrhizae and ectomycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction is sexual and vegetative; monoecious; vegetative reproduction 

by root collar and root sprouts

Reproductive phenology Flowers between April and June; fruit ripens from July through September

Pollination Insect-pollinated

Seed Seed type Red drupe-like ovoid fruit 0.25 to 0.55 in (6 to 14 mm) in diameter containing 

one seed; seed surrounded by a stony endocarp

Seed-bearing 

age

Unknown; other North American Prunus species flower by age 4 and bear fruit 

by age 10

Seed size/ Ranges from 4,120 to 8,790 cleaned seeds per lb (9,060 to 19,340 seeds per 
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76

weight kg); averages 7,020 seeds per lb (15,440 seeds per kg); 1 pound seed 

extracted from 4 pounds fruit

Seed longevity/ 

survivability

Seeds remain viable in soil and duff for many years

Seed crop and 

frequency

Prolific producer of seed

Seed 

dissemination

Time of year August through September

Method and 

dispersal 

agents

Birds, bears, and small mammals

Distance Unknown; dependent on movement of birds and mammals

Germination requirements Undergoes embryo dormancy; after-ripening period necessary for 

germination; requires exposure to moisture and oxygen during after-ripening; 

cold stratification for 90 to 160 days increases germination

Seedling survival Regeneration abundant where adequate sunlight and exposed mineral soil 

occur

Threats and Management Considerations

Insects and disease Numerous insects and fungal pathogens are associated with the genus 

Prunus; susceptible to stem- and root-rot fungi 

Harvest Not a commercial timber species

Fragmentation Widespread throughout its range in Washington

Fire Top-killed by fire; sprouts vigorously after top-kill; high-severity fire favors 

bitter cherry over associated species

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Propagated from seed and cuttings; planted for land reclamation and slope 

stabilization

References

Arno and Hammerly 2007, Esser 1995, Klinka et al. 2000, USDA NRCS 2010
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Douglas-fir (Pseudotsuga menziesii)

Ecology

Taxonomy and nomenclature There are two varieties of Douglas-fir: Pseudotsuga menziesii var. menziesii, 

the variety described here, occurs along the Pacific Coast, and Pseudotsuga

menziesii var. glauca occurs predominantly in the Rocky Mountains

Description A large, evergreen conifer reaching heights over 250 ft (75 m), with a dense 

conical to columnar crown of long branches; lower branches are self-pruned 

except for open-grown trees; deeply furrowed, reddish brown bark

Distribution From west-central British Columbia to central California; var. menziesii occurs 

from the coast through the Cascade Range, from sea level to around 5,000 ft 

(1,520 m) elevation in Washington; var. glauca occurs from central British 

Columbia throughout the Rocky Mountains and into central Mexico

Successional stage A long-lived species occurring in all stages of secondary succession; west of 

the Cascade crest it typically regenerates in nearly pure stands following 

large-scale, stand-replacing disturbances including wildfire, logging, and 

windthrow; a pioneer, but owing to its longevity, it often remains a major 

component of such stands for well over 300 years; also a major or minor 

component of old-growth stands; east of the Cascade crest, Douglas-fir is 

often a late-successional species

Associated forest cover The most dominant tree species in the region; in western Washington, 

Douglas-fir typically regenerates after disturbance as a pure stand or as the 

dominant species; associates include western hemlock, western redcedar, 

Pacific silver fir, Sitka spruce, grand fir, red alder, bigleaf maple, and shore 

pine; east of the Cascade crest, common associates are ponderosa pine, 

grand fir, lodgepole pine, and western larch (Larix occidentalis)

Habitat Sites Competes well on a wide range of sites, at all slopes, aspects, and on most 

soils

Soils Shallow to deep soils derived from a broad range of parent materials; texture 

ranges from clay to sand; fertility ranges from low to very high

Moisture Intolerant of flooding and shallow water tables; tolerant of very dry soils

Temperature Low frost tolerance; intolerant of temperatures below 14 °F (-10 °C) for more 

than 1 week; moderate heat tolerance

Shade tolerance Intermediate shade tolerance; shade tolerance decreases with age

Interspecific 

interactions

Animal damage New growth of young trees is highly palatable and often browsed by deer and 

elk; small mammals, birds, and insects destroy seeds; impact is greatest in 

years of low seed production

Mycorrhizal 

fungi

Associated with arbuscular mycorrhizae and ectomycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction is sexual; monoecious
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Reproductive phenology The reproductive cycle last approximately 17 months; reproductive primordia 

develop throughout the growing season prior to the cone crop; flowering and 

pollination occur between March and May of the following year, 7 to 8 weeks 

after dormancy is broken; cones ripen between mid-August and midSeptember; phenology strongly influenced by elevation and latitude; pollen 

shedding is delayed by 1 day for each 77-ft (23-m) increase in elevation

Pollination Wind-pollinated

Seed Seed type Cones 2 to 4 in (5 to 10 cm) long, primarily in the upper crown; cones usually 

contain 26 to 50 seeds; seeds have a large, single wing

Seed-bearing 

age

Cones may be produced by age 10 years or younger; significant seed 

production does not begin until age 20 to 30 years

Seed size/ 

weight

Seed weight is highly variable but averages 39,300 cleaned seeds per lb 

(86,600 seeds per kg)

Seed longevity/ 

survivability

Under natural conditions, seed remains viable for 1 or occasionally 2 years; 

seed has been successfully stored at 0 °F (-18 °C) for 27 years

Seed crop and 

frequency

Seed production is irregular; heavy crops occur every 5 to 7 years, and crop 

failures occur at the same frequency; in heavy crop years, most of the seed is 

produced by only about 25 percent of trees

Seed 

dissemination

Time of year Seedfall begins in August or September; the majority of seeds are often 

dropped by the end of October, but some seedfall continues throughout winter

Method and 

dispersal 

agents

Seeds are primarily dispersed by wind; small amounts of seed are dispersed 

by small mammals and birds including Clark’s nutcracker

Distance Most seed falls within 330 ft (100 m) of the source tree; a small portion of seed 

may be dispersed as far as 0.6 to 1.2 mi (1 to 2 km) 

Germination requirements Germination occurs between March and May, depending on climate; seed 

viability typically only 40 to 50 percent, sometimes less; germination best on 

moist mineral soil

Seedling survival Seedling survival highest on bare mineral soil or mineral soil with light litter 

layer; excessive heat and drying results in mortality; first-year growth limited 

by moisture availability; onset of dormancy occurs in mid-summer of first year; 

first-year survival increased by shade; growth in subsequent years greater 

under full sunlight

Vegetative phenology Budburst occurs from May to early June; vegetative shoots elongate for 

approximately 6 weeks; most shoot growth occurs as part of this initial flush, 

although young trees also exhibit lammas growth if sufficient soil water is 

available; diameter growth begins in April and continues through October, 

given adequate moisture; diameter growth ceases in mid-summer on droughty 

sites; lateral bud primordia enlarge in June and July

Genetics

Mating system Predominantly outcrossing with high outcrossing rate
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Outcrossing % (tm) 0.925

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.17

Geographic differentiation Weak population differentiation based on molecular markers but strong for 

quantitative traits

Fst or Gst 0.043

Patterns of variation QST = 0.62, 0.34, 0.51 for fall cold injury, growth, and phenology traits, 

respectively; Douglas-fir is considered a specialist species, with fairly narrow 

climatic tolerances within populations

Genetic analysis research results Probably the most studied Pacific Northwest conifer; substantial genetic 

variation has been found in many traits including spring and fall cold 

hardiness, drought hardiness, growth, phenology, and wood quality

Threats and Management Considerations

Insects and disease Susceptible to numerous insects and fungal pathogens; significant damage 

results from shoestring root rot (Armillaria mellea), laminated root rot (Phillinus 

weirii), and red ring rot (Phillinus pini); Douglas-fir beetle is the most damaging 

insect

Harvest The most important timber species in the region and one of the most important 

timber species in the world

Fragmentation Old-growth forests are fragmented and infrequent; younger forests, both 

natural and planted, are ubiquitous

Fire At maturity, more resistant to surface fire than many of its associates; older 

trees have thick bark and few low branches; historically, the moist Douglas-fir 

forests of western Washington burned in large, stand-replacing wildfires at 

intervals of approximately 300 to 500 years

Other damaging agents High winds may cause significant windthrow when soils are wet; heavy snow 

and ice may cause top breakage

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations By far the most frequently planted species in the region; regenerated in singleage silvicultural systems, rarely in multi-age systems

References

Aagaard et al. 1998, Aitken and Adams 1996, Anekonda et al. 2002, Arno and Hammerly 2007, Balduman et al. 

1999, Bonner and Karrfalt 2008; El-Kassaby and Ritland 1996, El-Kassaby et al. 1981, Hawkins 2007, Hawkins and 

Stoehr 2009, Hermann and Lavender 1990, Hoffmann and Geburek 1995, Klinka et al. 2000, Krakowski and Stoehr 

2009, Krutovsky et al. 2009, Li and Adams 1989, Shaw and Allard 1982, Silen 1963, St. Clair 2006, St. Clair et al. 

2005, Uchytil 1991d, USDA NRCS 2010, Viard et al. 2001
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Oregon white oak (Quercus garryana)

Ecology

Taxonomy and nomenclature Known regionally as Quercus garryana, this is actually Quercus garryana var. 

garryana, one of three varieties of Quercus garryana; var. fruticosa (also 

known as var. breweri) and var. semota are shrub varieties occurring in 

California and Oregon

Description A small-to-medium, deciduous, broadleaf tree reaching 80 ft (25 m) in height; 

long, crooked, ascending limbs form a spreading crown, except in dense 

stands where crowns are narrow; gray to grayish-brown, furrowed, scaly bark

Distribution From Vancouver Island, British Columbia, to southern California; in 

Washington, occurs in the lowlands surrounding Puget Sound and south to 

the Columbia River; follows the Columbia River Gorge, and to a lesser extent, 

occurs in the foothills east of the Cascade Range; occurs from sea level to 

3,800 ft (1,160 m) elevation in Washington

Successional stage A pioneer species; a climax species where fire occurs frequently and on very 

dry sites where other trees cannot survive

Associated forest cover Occasionally occurs as the sole tree species in oak woodlands and savannas; 

more frequently occurs with conifers and other hardwoods; often present as a 

mid-story species beneath Douglas-fir, although it cannot survive in that 

condition due to shade intolerance; also occurs with Oregon ash (Fraxinus 

latifolia), bigleaf maple, lodgepole pine, and grand fir

Habitat Sites Found on sites where other trees have historically been excluded by fire and 

on harsh sites where other species cannot survive or compete; occurs on a 

wide range of sites from seasonally flooded riparian zones to dry rock 

outcrops; in the Puget Sound region, typically occurs on plains and terraces of 

glacial origin

Soils Soil texture ranges from heavy clay to sandy glacial outwash; soil fertility 

ranges from poor to rich

Moisture High drought tolerance; tolerates flooding and a fluctuating water table

Temperature High tolerance of heat; frost damage is infrequent

Shade tolerance Shade-intolerant to moderately shade-tolerant; shade tolerance decreases 

with age; regenerates beneath a partial canopy but cannot survive at maturity 

if overtopped

Interspecific 

interactions

Animal damage Seedlings browsed by deer and elk; seedling roots may be damaged by 

rodents

Mycorrhizal 

fungi

Associated with numerous species of mycorrhizae

Reproduction and Growth

Mode of reproduction Reproduces sexually and vegetatively; monoecious; vegetative reproduction 

typically occurs through root crown sprouts; sprouts prolifically after stem 

damage, harvest, or fire
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Reproductive phenology Reproductive primordia initiated in June, approximately 11 months before 

pollination; pollination occurs between April and June; flowering lasts 

approximately 1 week; acorns reach maturity from late August to September, 

4 to 5 months after pollination

Pollination Wind-pollinated

Seed Seed type Acorn usually 0.75 to 1.25 in (2 to 3 cm) in length with a shallow cup

Seed-bearing 

age

Seed production begins between 20 and 40 years of age; production 

continues beyond age 180 years

Seed size/ 

weight

Approximately 90 acorns per lb (200 per kg)

Seed longevity/ 

survivability

Under natural conditions, acorns do not remain viable longer than the growing 

season after they are formed; acorns may be stored at near-freezing 

temperatures for two years, although they frequently germinate during storage

Seed crop and 

frequency

In western Washington, crop size varies substantially by year, although some 

acorns are produced every year; heavy crops occur every 2 to 4 years; there 

is synchrony in crop size within a region (e.g., the Puget Sound region), but 

synchrony among regions occurs only in years of very high or very low 

production; production (dry weight) has been measured at 500 to 1,550 

pounds per ac (560 to 1,740 kg per ha)

Seed 

dissemination

Time of year Most acorns are dispersed from late August through September

Method and 

dispersal 

agents

Gravity, small mammals, and birds, including Steller’s Jays

Distance Squirrels and birds were observed transporting acorns from 30 ft (8 m) to 

1,300 ft (400 m) from the source before burying, dropping, or consuming them

Germination requirements Acorns begin to germinate in fall, when conditions are sufficiently warm and 

moist; germination hypogeal; acorn viability high; acorn moisture content must 

remain above 30 percent to maintain viability; predation is high as acorns are 

eaten by animals or damaged by insect larvae

Seedling survival After germination, seedlings form a vigorous taproot; taproot enables survival 

on dry sites and where vegetative competition is severe; top dieback is 

common but seedlings frequently sprout from the root crown following dieback

Vegetative phenology Leaves expand around the time of flowering; radial growth also is initiated at 

this time and continues through July; shoot elongation occurs primarily during 

May and June; leaf and flower primordia occupy the same overwintered bud

Genetics

Mating system Predominantly outcrossing with high outcrossing rate

Outcrossing % (tm) 0.962

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.17
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Geographic differentiation Strong population differentiation based on chloroplast microsatellites but weak 

differentiation based on nuclear microsatellites; relatively weak population 

differentiation for seedling traits

Fst or Gst 0.86 for chloroplast and 0.05 for nuclear microsatellites

Patterns of variation QST = 0.1 for growth and phenology, 0.3 for cold hardiness

Genetic analysis research results High pollen flow among populations likely the reason for the low population 

differentiation in nuclear microsatellites; significant genetic clines exist for 

height, germinant emergence date, and cold hardiness. Height and germinant 

emergence were strongly correlated with environmental variables associated 

with summer aridity, while cold hardiness was strongly correlated with 

temperature differential and mean warmest month temperature

Threats and Management Considerations

Insects and disease Host to numerous insects and fungal pathogens, although none are serious 

threats to survival; as a member of the white oak group, it is not susceptible to 

sudden oak death (Phytophthera ramorum)

Harvest Not a major timber species; sometimes used for firewood; recognized as an 

important wildlife species on public lands

Fragmentation Current range in Washington may have been influenced by Native Americans’ 

transportation of acorns; since European settlement, distribution in western 

Washington has been heavily fragmented by agriculture, development, and 

expansion of conifer forests; most existing oak woodlands established after 

European settlement

Fire Oregon white oak has evolved to tolerate fire; competing tree species are less 

tolerant of fire; seedlings and saplings may be top-killed by surface fire; larger 

trees have thick bark and are resistant to fire damage, particularly that of 

surface fires burning herbaceous fuels; Oregon white oak may sometimes 

recover from a growing-season crown fire

Other damaging agents Invasive understory species such as Scotch broom (Cytisus scoparius) 

suppress oak regeneration; most Oregon white oak woodlands and savannas 

in western Washington have been invaded by conifers; in these invaded 

stands, oak trees become shaded and eventually die, although individual oak 

trees may survive for decades; this mortality can be prevented by removing 

invading conifers

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Some state-listed, threatened herbaceous species occur in the vicinity of 

Oregon white oak trees, but they are not dependent on the trees; some 

Oregon white oak plant associations are listed as imperiled or critically 

imperiled according to NatureServe (G2 or G1)

References

Agee 1993; Arno and Hammerly 2007; Devine et al. 2010; Gucker 2007; Hubert and Aitken, n.d.; Klinka et al. 2000; 

Marsico et al. 2009; Peter and Harrington 2002, 2009; Ritland et al. 2005; Stein 1990; USDA NRCS 2010
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Pacific willow (Salix lucida ssp. lasiandra)

Ecology

Taxonomy and nomenclature One of three subspecies of Salix lucida

Description A deciduous, broadleaf, tall shrub or small tree reaching 50 ft (15 m) in height; 

stout, crooked limbs form a tall, shaggy crown; bark gray to black

Distribution From interior Alaska south along the Pacific Coast to southern California; also 

occurs through the Rocky Mountains to New Mexico; in Washington, most 

prevalent west of the Cascade Range

Successional stage A pioneering early seral species; rapidly colonizes disturbed sites, typically 

fresh alluvium; persists as a result of repeated flooding

Associated forest cover Black cottonwood, red alder, other willows (Salix spp.), Oregon ash, bigleaf 

maple

Habitat Sites Along streams and rivers; in wetlands; low to middle elevations

Soils Typically occurs on alluvial deposits; soils may be of any texture, but are most 

often coarse-textured 

Moisture Very tolerant of flooding and a fluctuating water table; occurs primarily near 

water

Temperature Unknown

Shade tolerance Shade-intolerant; will not regenerate in the shade of tall grasses

Interspecific 

interactions

Animal damage Browsed by deer and elk; consumed by beaver in winter

Mycorrhizal 

fungi

Species of the genus Salix are associated with both arbuscular mycorrhizae 

and ectomycorrhizae 

Reproduction and Growth

Mode of reproduction Reproduction is sexual and vegetative; dioecious; sexual reproduction more 

common; vegetative reproduction usually occurs through pieces of broken 

stem or branches; no root sprouting

Reproductive phenology Flowers appear in the spring at the same time as the leaves; in Idaho, flowers 

from April to May, and fruit ripens and is dispersed from June to August

Pollination Other Salix species are known to be pollinated by wind, insects, or both

Seed Seed type Fruits are capsules containing numerous, very small seeds with hairs

Seed-bearing 

age

Unknown; other willows produce seed by age 10 years

Seed size/ 

weight

11,500,000 cleaned seeds per lb (25,300,000 seeds per kg)
B-84 Climate Change and Forest Biodiversity in Western Washington

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Seed longevity/ 

survivability

Unknown; for other Salix spp. germination declines rapidly after 10 days; seed 

of Salix spp. has been successfully stored for 36 months at 14 °F (-10 °C) and 

for 44 months at -4 °F (-20 °C)

Seed crop and 

frequency

A prolific seed producer

Seed 

dissemination

Time of year Spring through early summer

Method and 

dispersal 

agents

Seeds dispersed by wind and water

Distance Unknown; other willows disperse seeds very long distances (i.e., several miles 

(kilometers))

Germination requirements Moist seedbed and sunlight required for germination; seeds landing on a moist 

seedbed germinate within 12 to 24 hours of dispersal; no seed dormancy; 

seeds begin photosynthesis as soon as they are moistened; germination rate 

is positively correlated with the amount of light seeds receive

Threats and Management Considerations

Insects and disease Unknown; associated willow species are attacked by insects and fungal 

diseases although the extent of damage is not quantified

Harvest Not a commercial timber species

Fragmentation Widespread within its range and habitat

Fire Fires infrequent in moist habitats where Pacific willow is often found; colonizes 

burned sites rapidly via prolific seed production; potential for sprouting 

following top-kill is unknown

Other damaging agents May be heavily browsed; occurs on sites prone to disturbance by flooding

NatureServe Conservation Status 

Ranking

G5T5 Secure—Common; widespread and abundant

Silvicultural considerations Well-suited for use in streambank stabilization

References

Arno and Hammerly 2007, Bonner and Karrfalt 2008, Lyons 1999, Uchytil 1989c, USDA NRCS 2010
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Scouler’s willow (Salix scouleriana)

Ecology

Description A deciduous, broadleaf, tall shrub or small tree reaching 40 ft (12 m) in height; 

often multi-stemmed; sprawling, twisted, stout limbs form a rounded crown; 

smooth to flaky bark

Distribution From interior Alaska east to Manitoba and south through the western United 

States into Mexico; occurs at higher elevations (up to 10,000 ft; 3,050 m) with 

decreasing latitude; occurs in eastern and western Washington on upland 

sites and riparian areas

Successional stage A persistent, early to mid-seral species; rapidly colonizes disturbed sites, 

including burned areas; sometimes persists into late seral stages east of the 

Cascade Range

Associated forest cover Occurs in many different vegetation types but is rarely a dominant species; 

found in disturbed areas and gaps; semi-arid ponderosa pine-Douglas-fir 

forests

Habitat Sites Found on a wide range of sites, from moist floodplain sites and gravel bars to 

dry uplands east of the Cascade Range; most often found on upland sites and 

in transitional upland-riparian zones; capable of growing on drier sites than 

most other willow species; found on drier, low-elevation sites in the Pacific 

Northwest; common on depositional land forms including colluvial soils and 

glacial deposits

Soils Shallow to deep soils of a wide variety of parent materials; moderately welldrained to well-drained soils 

Moisture Tolerant of a wide range of moisture conditions; often occurs on moist but 

well-drained sites as well as dry, shallow soils

Temperature Occurs in a mild, maritime climate in the Pacific Northwest but also tolerates 

greater temperature extremes in the Rocky Mountains 

Shade tolerance Slight tolerance of shade; may persist beneath a thin canopy

Interspecific 

interactions

Animal damage A preferred browse species, but very tolerant of browse damage

Mycorrhizal 

fungi

Species of the genus Salix are associated with both arbuscular mycorrhizae 

and ectomycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction is sexual and vegetative; dioecious; sprouts vigorously from the 

root crown beneath the soil surface

Reproductive phenology Flowering occurs between April and June; catkins appear before leaves; fruit 

ripens and is dispersed from May to July

Pollination Insects are important pollinators

Seed Seed type Catkins bear capsules 0.2 to 0.3 in (5 to 8 mm) long that contain numerous, 

tiny seeds with hairs
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Seed-bearing 

age

Likely begins to produce by age 10 years

Seed size/ 

weight

6,500,000 seeds per lb (14,300,000 seeds per kg)

Seed longevity/ 

survivability

Seeds do not undergo dormancy; seeds remain viable for only a few days 

unless exposed to moisture; seed of Salix spp. has been successfully stored 

for 36 months at 14 °F (-10 °C) and for 44 months at -4 °F (-20 °C)

Seed crop and 

frequency

Abundant seed crop

Seed 

dissemination

Time of year Late spring

Method and 

dispersal 

agents

Wind and water

Distance Seeds may be carried several miles (kilometers) by wind

Germination requirements Seeds are short-lived and germinate within 12 to 24 hours of dispersal; moist 

mineral soil and sunlight required for germination; seed viability very high 

under laboratory conditions

Seedling survival Survival is high where seedlings establish following a stand-replacing fire

Vegetative phenology Buds develop in April and leaves appear in April or May; stem elongates from 

May through July; leaves are dropped between July and November, 

depending on moisture availability

Threats and Management Considerations

Insects and disease Unknown; associated willow species are attacked by insects and fungal 

diseases although the extent of damage is not quantified

Harvest Not a commercial timber species

Fragmentation Widespread in Washington

Fire Favored by fire owing to vigorous sprouting and rapid colonization of burned 

sites; moderately susceptible to fire damage; sprouts from belowground buds 

near the root crown following top-kill or damage; sprouts grow vigorously and 

increase overall crown size

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Competes vigorously with conifer seedlings

References

Anderson 2001b, Arno and Hammerly 2007, Bonner and Karrfalt 2008, Royle and Ostry 1995, USDA NRCS 2010
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Pacific yew (Taxus brevifolia)

Ecology

Description A long-lived, coniferous, evergreen, tall shrub or small tree rarely reaching 60 

ft (18 m) in height; an often contorted, malformed stem; long branches form an 

irregular crown; thin, purplish, scaly bark

Distribution Along the Pacific Coast from southeastern Alaska to central California; an 

inland distribution occurs from southeastern British Columbia into northern 

Idaho and adjacent states; occurs throughout western Washington, from the 

coast to the Cascade Range, although it is rare in the Coast Range south of 

the Olympic Peninsula; occurs at low to moderate elevations in the Cascade 

Range

Successional stage Present in all stages of secondary succession, but uncommon in young 

stands; typically increases in cover with stand age; present in many climax 

communities and most prevalent in old-growth forests

Associated forest cover Most often occurs beneath canopies of western hemlock, Douglas-fir, western 

redcedar, and Pacific silver fir; also found beneath Sitka spruce, ponderosa 

pine, and grand fir; sometimes occurs in moist microsites beneath Oregon 

white oak and Oregon ash

Habitat Sites Capable of growing on a wide range of sites; typically found in cool, moist, 

shaded locations in lowlands and mountains; also occurs on warm, dry, sites

Soils Occurs most often on deep, moist, well-drained soils; soil fertility ranges from 

poor to very high

Moisture Tolerant of flooding; moderately tolerant of drought; more abundant on moist 

sites

Temperature Moderately frost tolerant; moderately tolerant of heat

Shade tolerance The most shade-tolerant tree in the Pacific Northwest; may require shade on 

hot, dry sites; may establish and grow in deep shade but also can survive after 

canopy removal

Interspecific 

interactions

Animal damage A preferred browse species of ungulates; may suffer damage from rabbits; 

may be heavily browsed in open areas, although delayed germination may 

reduce exposure to browsing

Mycorrhizal 

fungi

Associated with arbuscular mycorrhizae; some observations of 

ectomycorrhizal associations in old-growth forests

Reproduction and Growth

Mode of reproduction Reproduction is sexual and vegetative; dioecious; vegetative reproduction is 

through layering and stump sprouts

Reproductive phenology In Washington, flowering occurs in June and fruit ripens between August and 

October; fruit is dropped around October

Pollination Wind-pollinated

Seed Seed type Ovoid-oblong seed approximately 0.3 in (8 mm) long; seed is partially 
B-88 Climate Change and Forest Biodiversity in Western Washington

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encased in a fleshy, cup-shaped aril; the seed has a bony inner seedcoat and 

a membranous outer seedcoat

Seed-bearing 

age

Unknown; English yew (Taxus baccata) begins to bear seed at age 80

Seed size/ 

weight

Cleaned seeds average 15,000 seeds per lb (33,100 seeds per kg)

Seed longevity/ 

survivability

Some seeds germinate the first year and some germinate the second year; it 

is possible that a potion of seeds remain in the soil for many years before 

germinating; seed can likely be stored for many years at -4 to 0 °F (-20 to -18 

°C)

Seed crop and 

frequency

A prolific seeder; frequency of heavy crops is unknown

Seed 

dissemination

Time of year Seeds ripen and are dispersed from August to October

Method and 

dispersal 

agents

Seed falls to the ground or is taken from the tree by birds and rodents; rodents 

and some birds cache seed

Distance Some seed transported long distances by birds

Germination requirements Seed germinates slowly over a period of at least 2 years; stratification 

required; germination epigeal; germination typically occurs in heavy organic 

matter

Seedling survival Seedling establishment generally greater in the understory than in openings

Genetics

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.145

Geographic differentiation Weak population differentiation based on molecular markers

Fst or Gst 0.096

Genetic analysis research results Populations and individuals within populations differ significantly in taxane 

content

Threats and Management Considerations

Insects and disease Insects and fungal pathogens are not a major concern

Harvest Once harvested to produce the medication Taxol, which is now created 

synthetically or harvested from other Taxus spp. that are planted for that 

purpose

Fragmentation Widespread, although sometimes infrequent throughout its range in 

Washington; rare in forests with a history of logging or recent fire

Fire Very susceptible to fire; killed by light surface fires; most prevalent in stands 

with long fire-free intervals
Climate Change and Forest Biodiversity in Western Washington B-89

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NatureServe conservation status 

ranking

G4/G5: G4 Apparently Secure—Uncommon but not rare; some cause for longterm concern due to declines or other factors/ G5 Secure—Common; 

widespread and abundant; range indicates some uncertainty about the exact 

status; concerns are slow growth, the fact that it does not reproduce rapidly, 

its somewhat narrow ecological range, and loss of habitat as a result of 

logging activity

Silvicultural considerations Pacific yew typically becomes most prevalent after centuries of stand 

development; it grows and reproduces slowly in the understory; Pacific yew 

released through complete overstory removal apparently undergoes stress but 

often adapts to the new conditions

References

Arno and Hammerly 2007, Bolsinger and Jaramillo 1990, Bonner and Karrfalt 2008; Busing et al. 1995, Daoust 1992, 

Doede et al. 1993, DiFazio et al. 1997, El-Kassaby and Yanchuk 1994, Griffiths et al. 1995, Klinka et al. 2000, Scher 

and Jimerson 1989, Tirmenstein 1990, USDA NRCS 2010, Wheeler et al. 1995
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Western redcedar (Thuja plicata)

Ecology

Description A long-lived, medium-to-large, evergreen conifer occasionally reaching 200 ft 

(60 m) in height; a pointed, conical crown of drooping branches; hanging 

sprays of scale leaves; thin, reddish, fibrous bark; a frequently tapered, fluted 

base

Distribution Occupies coastal and interior ranges; coastal range extends from 

southeastern Alaska to northern California, including western Washington 

from the coast to the Cascade Range; less frequent on eastern slopes of the 

Cascades; interior range reaches from southeastern British Columbia into 

northern Idaho and includes northeastern Washington; common below 4,100 

ft (1,250 m) in Washington

Successional stage Occurs in all stages of succession; often considered a climax species because 

of its shade tolerance

Associated forest cover Typically in mixed-species stands, often with Douglas-fir and western 

hemlock; also occurs with Sitka spruce, red alder, and black cottonwood

Habitat Sites Found on most low- and mid-elevation sites in western Washington, from 

forested swamps to shallow, rocky soils on slopes

Soils Occurs on a wide variety of soils and parent materials; soils range from very 

nutrient-poor to very nutrient-rich

Moisture Tolerant of wet soils and seasonal flooding; moderate drought tolerance

Temperature Low frost tolerance; moderately tolerant of heat; requires protection on hot, 

dry sites

Shade tolerance Very shade tolerant; nearly as tolerant as Pacific silver fir and western 

hemlock

Interspecific 

interactions

Animal damage Preferred browse species for deer and elk; seedlings and saplings heavily 

browsed; bears occasionally strip bark to feed from sapwood

Mycorrhizal 

fungi

Associated with arbuscular mycorrhizae; seedlings responsive to mycorrhizal 

inoculation

Reproduction and Growth

Mode of reproduction Reproduces sexually and vegetatively; monoecious; vegetative reproduction 

occurs through layering, from fallen limbs, or from the branches of fallen trees; 

vegetative reproduction is most common in moist, closed-canopy stands; 

reproduction from seed is most common after disturbance

Reproductive phenology Reproductive cycle lasts approximately 16 months, beginning in early June of 

year 1 with the initiation of cone primordia; 6 to 7 weeks after breaking 

dormancy in year 2, pollination occurs over a period of 1 to 2 weeks from midFebruary (mild climates) to early April (higher elevations); fertilization occurs 

around late May; west of the Cascades, redcedar cones mature approximately 

5 months after pollination

Pollination Wind-pollinated
Climate Change and Forest Biodiversity in Western Washington B-91

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Seed Seed type Ellipsoid cones 0.4 to 0.6 in (10 to 14 mm) long; 8 to 14 seeds per cone; 

winged seeds

Seed-bearing 

age

Seed production usually begins between ages 15 and 25 years; peak 

production occurs after age 70 to 80 years

Seed size/ 

weight

Averages 414,000 seeds per lb (912,700 seeds per kg) ranges from 203,000 

to 592,000 seeds per lb (448,000 to 1,305,000 seeds per kg); seeds 0.16 to 

0.30 in (4 to 7.5 mm) in diameter including wings

Seed longevity/ 

survivability

High initial viability; under natural conditions viability declines rapidly; viability 

remains high for 7 to 20 years stored at -4 °F (-20 °C)

Seed crop and 

frequency

Relatively high capacity for regeneration; ranges from 100,000 to 1,000,000 

seeds per ac (247,000 to 2,470,000 per ha); seed crops usually every other 

year for individual trees; heavy seed crops every 3 to 4 years

Seed 

dissemination

Time of year Begins in September, peaks in October and November, and continues through 

February or March; warm, dry conditions may lead to earlier seedfall

Method & 

dispersal 

agents

Seeds dispersed by wind; seeds have small wings; birds eat seeds but not a 

confirmed vector

Distance Adequate dispersal to 330 ft (100 m); seeds rarely found beyond 400 ft (122 

m) from source

Germination requirements Germinates well without stratification in fall, winter, or spring; germination 

minimal after first year; shaded mineral soil best for germination; mortality high 

during germination period and thereafter

Seedling survival Seedling survival generally low; seedlings in exposed areas less tolerant of 

high soil temperatures, drought, and frost than associated species; high 

resistance to flooding; a preferred browse species

Vegetative phenology Shoot elongation begins as early as mid-March, peaks in May, and ends 

between August and November; radial growth occurs from May to September

Genetics

Mating system Outcrossing with widely varying but often substantial inbreeding

Outcrossing % (tm) 0.72 (range 0.173–1.257)

Genetic diversity Very low genetic diversity

Heterozygosity (He) 0.039

Geographic differentiation Weak population differentiation

Fst or Gst 0.033

Patterns of variation Generally low levels of population differentiation in quantitative traits have led 

to western redcedar being considered a “generalist” species with relatively 

wide climatic and environmental tolerances
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Genetic analysis research results Early isozyme studies found zero genetic diversity in seed from trees in 

Oregon and Washington; families with lower terpene content are more 

palatable to deer; interior populations (northern Idaho area) differ significantly 

in some growth and cold hardiness traits, but the clines are gentle and 

populations need to be >600 m apart in elevation or >2o in latitude to be 

genetically differentiated

Threats and Management Considerations

Insects and disease Insect damage infrequently a problem; often damaged by a variety of fungal 

pathogens; trunk decay more common than in associated species; Phellinus 

weirii most common rot fungus

Harvest A valuable timber species harvested from second-growth stands and 

occasionally from old-growth stands

Fragmentation Occurs in mixed-species forests throughout its range in Washington

Fire More susceptible to fire damage than associated species; thin bark, low 

branches, flammable foliage; large trees less susceptible to fire; in western 

Washington, fire-return interval is long (50 to 350 years) in most stands 

containing western redcedar

Other damaging agents Susceptible to windthrow on wet sites

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Increasingly planted although browse damage to planted seedlings is a 

concern; research is ongoing to develop browse-resistant trees; often 

relegated to sub-canopy positions by faster-growing conifers in mixed-species 

stands

References

Arno and Hammerly 2007; El-Kassaby et al. 1994; Glaubitz et al. 2000; Harrington 2010; Klinka et al. 2000; Minore 

1983, 1990; O'Connell et al. 2001, 2004, 2008; Tesky 1992a; USDA NRCS 2010; Yeh 1988
Climate Change and Forest Biodiversity in Western Washington B-93

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Western hemlock (Tsuga heterophylla)

Ecology

Description A medium-to-large evergreen conifer, occasionally reaching 200 ft (60 m) in 

height; a slender stem and a dense, narrow crown with a drooping leader; 

thin, reddish-brown bark becoming furrowed with age

Distribution Coastal and inland ranges; coastal range extends from Alaska’s Kenai 

Peninsula to central California; inland range extends through southeastern 

British Columbia into northern Idaho, northeastern Washington, and 

northwestern Montana; occurs from Washington’s coast to the eastern slopes 

of the Cascade Range; less frequent east of the Cascade crest; occurs to an 

elevation of 3,500 ft (1,070 m) in western Washington and to 5,000 ft (1,500 

m) in eastern Washington

Successional stage A climax species; present in all stages of secondary succession; frequent in 

old-growth stands

Associated forest cover Occurs in pure and mixed-species stands; in western Washington, most 

frequently occurs with Douglas-fir, Pacific silver fir, Sitka spruce, and western 

redcedar

Habitat Sites Grows best in mild, humid climates with growing-season fog and precipitation 

Soils Tolerates soils of very low fertility including acidic, organic soils; tolerates soils 

of most textures, although growth rate is reduced on compacted or clayey 

soils

Moisture Low drought tolerance; intolerant of very shallow water tables; prefers welldrained soils

Temperature Low heat tolerance; intolerant of frozen soil; shallow-rooted and requires 

snowpack to insulate soil

Shade tolerance Very shade-tolerant; shade tolerance similar to Pacific silver fir and western 

redcedar

Interspecific 

interactions

Animal damage Sometimes browsed by deer and elk, though not a preferred species; small 

stems may be clipped by rodents

Mycorrhizal 

fungi

Associated with arbuscular mycorrhizae and ectomycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction is sexual and vegetative; monoecious; vegetative reproduction 

occurs through layering; seedlings may sprout from the root crown

Reproductive phenology Pollen and seed cones differentiate in June and July, respectively, of the year 

prior to pollination; pollination occurs from mid to late April in Oregon and from 

late May to June in Alaska; seed cones mature 120 to 160 days after 

pollination, although time of maturation is variable within a tree

Pollination Wind-pollinated
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Seed Seed type Cones 0.75 to 1.25 in (19 to 32 mm) long containing 30 to 40 seeds with large 

wings

Seed-bearing 

age

Regular cone production begins around age 25 to 30 years

Seed size/ 

weight

Weight ranges from 189,000 to 508,000 seeds per lb (417,000 to 1,120,000 

seeds per kg), with an average of 260,000 seeds per lb (573,000 seeds per 

kg)

Seed longevity/ 

survivability

Seeds viable only during the first growing season after seedfall; seed can be 

stored at 0 °F (-18 °C) for 5 years or longer

Seed crop and 

frequency

Mature trees produce abundant seed; some cones produced every year; 

heavy crops every 3 to 4 years; a 100-year-old stand produced 8,000,000 

seeds per ac (19,800,000 seeds per ha) in good seed years

Seed 

dissemination

Time of year Cone scales open and seeds drop in late October; most seeds shed in fall; 

cone scales open and close in response to atmospheric moisture

Method and 

dispersal 

agents

Seed dispersed by wind

Distance In open stands, most seeds fall within 2,000 ft (600 m) of the parent tree, 

although some travel as far as 3,800 ft (1,150 m); distances are much less in 

dense stands

Germination requirements Cold stratification increases germination; following stratification, germination 

rate increased by warmer temperatures; seeds germinate on mineral soil and 

a wide range of organic substrates, given sufficient moisture; decaying logs 

and rotten wood are favorable seedbeds; germination epigeal

Seedling survival Mortality results when organic seedbeds become dry in direct sunlight; 

seedling survival is highest on mineral soil and other materials that provide 

adequate moisture; early growth is slow

Vegetative phenology Vegetative phenology varies substantially by latitude; buds begin to swell in 

late March and burst around May; shoots elongate rapidly until early July; 

shoot elongation then slows and ends around August

Genetics

Mating system Predominantly outcrossing with high outcrossing rate

Outcrossing % (tm) 0.93

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.12
Climate Change and Forest Biodiversity in Western Washington B-95

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Genetic analysis research results Differences in 5-year height among four populations in Washington and 

Oregon were significant, but variation among families within sites was not; in 

5-year old seedlings, fall and spring cold hardiness and date of budburst 

increased and height growth decreased with latitude; significant variation was 

found in seed weight, number of cotyledons, and seedling growth rate, growth 

rate was related to soil and air temperature; seedlings in southern latitudes, 

middle elevations, and coastal provenances grew fastest, although a strong 

north-south cline exists in coastal provenances

Threats and Management Considerations

Insects and disease Although many different insects attack western hemlock, damage is not a 

serious concern in coastal populations; fungal pathogens are more often a 

problem; common pathogens include Indian paint fungus, annosus root and 

butt rot, red ring rot, laminated root rot, Armillaria root disease, Schweinitzii 

butt rot, Douglas-fir needlecast, and black stain root disease; dwarf mistletoe 

(Arceuthobium campylopodum) is a common parasite

Harvest An important commercial species harvested for timber and pulp

Fragmentation While old-growth stands are fragmented, younger stands containing western 

hemlock are common throughout its range in western Washington

Fire Very susceptible to fire damage owing to thin bark, shallow roots, low 

branches, and highly flammable foliage; fire-return interval is low (150 to 400 

or more years) in the moist maritime stands where western hemlock is 

prevalent

Other damaging agents Low resistance to windthrow

NatureServe Conservation Status 

Ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations An extremely productive species; more productive than Douglas-fir on some 

sites; can be regenerated under many different silvicultural systems; responds 

well to release from suppression

References

Arno and Hammerly 2007; Bonner and Karrfalt 2008; El-Kassaby et al. 2003; Foster and Lester 1983; Hannerz et al. 

1999; Klinka et al. 2000; Kuser and Ching 1980, 1981; Owens and Molder 1984; Packee 1990; Tesky 1992b; USDA 

NRCS 2010; Wellman et al. 2003, 2004
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Mountain hemlock (Tsuga mertensiana)

Ecology

Description A small-to-medium, evergreen conifer reaching 75 to 150 ft (23 to 45 m) in 

height depending on the site; a narrow conical crown of drooping and 

spreading branches; dark, thick bark becomes deeply furrowed and plated 

with age

Distribution Along the Pacific Coast from the Kenai Peninsula of Alaska to central 

California, increasing in elevation southward; occurs in Washington in the 

Olympic Range and on the western slopes and relatively moist, upper eastern 

slopes of the Cascade Range; reported at elevations of 4,200 to 5,600 ft 

(1,300 to 1,700 m) in Washington’s North Cascades

Successional stage Occurs in all stages of succession; a long-lived climax species in most of its 

habitat

Associated forest cover Occurs in mixed stands, less often in pure stands; near treeline occurs as 

scattered individuals or in clumps; occurs in mixed stands with Pacific silver 

fir, subalpine fir, and Alaska yellow-cedar; occurs less frequently with 

whitebark pine, Engelmann spruce, western white pine, lodgepole pine, 

western hemlock, western redcedar, and Douglas-fir

Habitat Sites Present in the highest forested zones; occurs on most landforms, but often in 

mixed stands on sheltered slopes, in draws, and on north-facing slopes

Soils Present on a wide range of soil types; fertility ranges from very poor to 

moderate; tolerant of organic soils, very acidic soils, and low nutrient 

availability

Moisture Low drought tolerance; usually found on moist soils; tolerates soils ranging 

from slightly dry to very moist; mean annual precipitation in its range is 107 in 

(272 cm), mostly as snow

Temperature Low tolerance of heat; moderate to high frost tolerance; low tolerance of 

frozen soil; requires snowpack to insulate soil in winter

Shade tolerance Shade-tolerant; exceeded in shade tolerance only by Pacific silver fir, western 

hemlock, and Alaska yellow-cedar

Interspecific 

interactions

Animal damage Not reported

Mycorrhizal 

fungi

Associated with arbuscular mycorrhizae with ectomycorrhizae

Reproduction and Growth

Mode of reproduction Reproduction is predominantly sexual; monoecious; occasionally reproduces 

vegetatively through layering
Climate Change and Forest Biodiversity in Western Washington B-97

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Reproductive phenology Reproductive cycle spans two growing seasons; pollen and seed cone 

differentiate in late July of year 1; cones develop until dormancy in October; 

ovules initiated after winter dormancy; post-dormancy development is strongly 

affected by temperature; flowering occurs in June or July, approximately 12 

weeks after the end of dormancy, depending on elevation; seed cones 

receptive for 1 to 2 weeks; fertilization occurs around early August; seeds 

mature around mid-September; seedfall begins between late September and 

November, 90 to 120 days after pollination

Pollination Wind-pollinated; pollen released on warm, dry days

Seed Seed type Cones are 0.75 to 3.5 in (2 to 9 cm) long; bear winged seeds

Seed-bearing 

age

Seed production begins around age 20 years; mature trees (175 to 250 years) 

produce moderate to heavy cone crops

Seed size/ 

weight

Averages 114,000 seeds per lb (251,300 seeds per kg); ranges from 102,000 

to 207,000 seeds per lb (225,000 to 456,000 seeds per kg)

Seed longevity/ 

survivability

Unknown under natural conditions; seed is stored at 0 °F (-18 °C), although 

success of long-term storage is likely variable and influenced by genetics

Seed crop and 

frequency

Large seed crops occur about every 3 years; seed crops may be very low in 

other years; very heavy seedfall estimated at 87,000 to 1,677,000 seeds per 

ac (215,000 to 4,144,000 seeds per ha); warm summer in the previous year 

yields heaviest crops

Seed 

dissemination

Time of year Majority of seedfall occurs when cones initially open between late September 

and November; warm, dry weather causes earlier seed release; wet, cool 

weather may delay release

Method and 

dispersal 

agents

Seed predominantly wind-dispersed; occasionally consumed by birds

Distance Seed dispersed to approximately 500 ft (150 m) from source tree

Germination requirements Moist organic soil, mineral soil, and snow are suitable substrates; cold 

stratification may increase germination; germination epigeal; germination 

ranges from 47 to 75 percent

Seedling survival Young seedling growth best in partial shade; early growth slow; seedlings 

have relatively low drought tolerance; slow to regenerate in disturbed areas

Vegetative phenology Late snowpack shortens the growing season; growth positively related to 

summer temperature, length of growing season, and depth of snowpack

Genetics

Genetic diversity Average genetic diversity

Heterozygosity (He) 0.087

Geographic differentiation Weak genetic differentiation based on molecular markers

Fst or Gst 0.077
B-98 Climate Change and Forest Biodiversity in Western Washington

98

Patterns of variation Moderate population differentiation based on quantitative traits

Genetic analysis research results Populations and families within populations in southern coastal British 

Columbia differed in height growth, fall cold hardiness, gas exchange, and 

biomass allocation, but most of the genetic variation was within populations 

(77 to 87 percent); populations from higher latitudes or elevations had higher 

growth rates and the variation was related to climate coldness 

Threats and Management Considerations

Insects and disease Susceptibility to insect and fungal damage generally low; prone to damage by 

Phellinus weiri; moderately susceptible to dwarf mistletoe

Harvest Occasionally harvested in mixed stands; high-elevation stands have very 

limited access

Fragmentation More susceptible to fragmentation as a result of climate change than as a 

result of direct human impacts (owing to high elevation sites); upward 

migration could lead to fragmentation

Fire More susceptible to fire damage than its associates, owing to retention of low 

branches, flammable foliage, and occurrence in dense clusters; wildfire return 

interval is typically very long

Other damaging agents Susceptible to windthrow owing to shallow root system

NatureServe conservation status 

ranking

G5 Secure—Common; widespread and abundant

Silvicultural considerations Natural regeneration is slow after disturbance; early growth is slow; planting 

often ineffective at high elevations

References

Ally and Ritland 2007, Ally et al. 2000, Arno and Hammerly 2007, Benowicz and El-Kassaby 1999, Benowicz et al. 

2001b, Bonner and Karrfalt 2008; Franklin and Krueger 1968, Klinka et al. 2000, Means 1990, Owens and Molder 

1984, Tesky 1992c, USDA NRCS 2010, Woodward et al. 1994
Climate Change and Forest Biodiversity in Western Washington C-1

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APPENDIX C:

EVALUATION OF THE NATURESERVE 

CLIMATE CHANGE VULNERABILITY INDEX
C-2 Climate Change and Forest Biodiversity in Western Washington

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BACKGROUND

The NatureServe Climate Change Vulnerability Index 

(NSVI) is a management tool designed to identify the 

vulnerability of plant and animal species to climate 

change (NatureServe 2010a). The NSVI also organizes 

user-collected information in a format that enables the 

user to identify underlying causes of vulnerability 

across multiple species.

From user-collected information on exposure and 

sensitivity to climate change, the NSVI calculates a 

score for each species’ vulnerability within a specified 

geographic area. Exposure is defined as the magnitude 

of the predicted changes in temperature and 

precipitation across the species’ range within the 

assessment area. Sensitivity relates to characteristics 

that increase a species’ ability to adapt to significant 

changes in temperature and precipitation. 

Vulnerability scores consist of six categories ranging 

from extremely vulnerable to not vulnerable.

The NSVI vulnerability score for a single species is 

based on three categories of factors: 

1. The combination of exposure and sensitivity to 

climate conditions projected for the year 2050. A 

species’ sensitivity to climate change is calculated 

from up to 17 parameters including predicted 

sensitivity to temperature and precipitation changes, 

physical habitat specificity, dispersal ability, and 

interspecific interactions. Exposure to climate change 

is based on year-2050 temperature and precipitation 

predictions acquired online, calculated from provided 

GIS data, or derived from other climate models. The 

NSVI integrates sensitivity and exposure: the 

sensitivity of a species to climate change intensifies as 

its level of exposure increases. 

2. Indirect exposure to this projected climate 

change. Indirect exposure to climate change includes 

exposure to rising sea level and a species’ distribution 

relative to natural or anthropogenic barriers that 

potentially interfere with migration. 

3. The species’ documented response to climate 

change. Documented response to climate change is 

applied to species for which a documented or modeled 

response to climate variation already exists.

First released in 2009, the NSVI is a Microsoft Excel 

spreadsheet model that requires no computer modeling 

experience. However, basic familiarity with the 

ecological characteristics of the subject species 

facilitates collection of the required input data. 

Intended for use by management programs working 

with numerous species, the NSVI is most applicable to 

areas ranging from the size of a national park or 

wildlife refuge to the average size of a western U.S. 

state. The NSVI works independently of and 

complements the existing NatureServe conservation 

status ranking system (NatureServe 2010b). A detailed 

guide to applying of the NSVI is provided on the 

NatureServe website (NatureServe 2010a).
Climate Change and Forest Biodiversity in Western Washington C-3

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APPLYING THE NATURESERVE 

VULNERABILITY INDEX TO TREE 

SPECIES ON THE OLYMPIC 

PENINSULA

We tested the NSVI (release 2.0) as a potential tool for 

assessing the vulnerability of tree species in western 

Washington. Ideally, such a tool would assist 

managers in prioritizing species according to 

vulnerability and would reveal fundamental causes of 

vulnerability. Possible advantages of using the NSVI 

for this purpose are: (1) it is a relatively well-known 

index produced by a nationally recognized 

organization, (2) it provides a standardized approach 

that can be applied to both plants and animals in any 

ecosystem, and (3) it is readily available and relatively 

easy to use.

To evaluate the applicability of the NSVI to trees of 

western Washington, we tested the index on six tree 

species on the Olympic Peninsula: whitebark pine, 

golden chinquapin, Pacific yew, western white pine, 

Oregon white oak, and quaking aspen (table C-1). 

These six species vary in their distribution, life history, 

vulnerability to insects and disease, and represent a 

range of management challenges.

In the process of applying the NSVI, we collected 

information from several sources. For predicted local 

climate change exposure in the year 2050, we used 

temperature forecasts developed by the Climate 

Impacts Group at University of Washington (Littell at 

al. 2009c) and the Hamon AET:PET moisture metric 

predictions from data provided by NatureServe 

(Hamon 1961, NatureServe 2010a). We obtained 

historical climate data, which are used to determine 

species’ sensitivity to changes in temperature and 

precipitation, from the online Climate Wizard tool 

(Girvetz at al. 2009), one of the NSVI’s recommended 

sources for climate data. For each tree species, we 

gathered additional required information on sensitivity 

to climate change from a number of sources including 

Silvics of North America (Burns and Honkala 1990), 

the Fire Effects Information System (Fischer 2010), 

journal publications, and Forest Service reports. In 

cases where published information was not available, 

we consulted Forest Service personnel with knowledge 

of the species. An example of the completed 

worksheet for Oregon white oak is given in fig. C-1.

Table C-1. Six tree species from the Olympic Peninsula selected for evaluation with the NatureServe 

Climate Change Vulnerability Index

Species Group

NatureServe conservation 

status1

NatureServe 

vulnerability index 

score

Washington state 

rank

Global 

rank

Chrysolepis chrysophylla 

Golden chinquapin

Evergreen, 

broadleaf S2 G5 Highly vulnerable

Pinus albicaulis 

Whitebark pine

Evergreen 

conifer SNR G3/G4 Moderately vulnerable

Pinus monticola 

Western white pine

Evergreen 

conifer SNR G4/G5 Moderately vulnerable

Populus tremuloides 

Quaking aspen

Deciduous, 

broadleaf SNR G5 Not vulnerable, presumed stable

Quercus garryana 

Oregon white oak

Deciduous, 

broadleaf SNR G5 Not vulnerable, presumed stable

Taxus brevifolia 

Pacific yew

Evergreen 

conifer SNR G4/G5 Not vulnerable, presumed stable

1 S2 Imperiled

 SNR Not ranked at the state level

 G5 Secure

 G3/G4 Vulnerable/Apparently Secure Range indicates some uncertainty about the exact status.

 G4/G5 Apparently Secure/Secure Range indicates some uncertainty about the exact status.
C-4 Climate Change and Forest Biodiversity in Western Washington

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Figure C-1. NatureServe Climate Change Vulnerability Index (release 2.0) 

calculator, using Oregon white oak as an example. Species data are entered 

in sections A, B, C, and D, and the Index score appears in the final section
Climate Change and Forest Biodiversity in Western Washington C-5

5

Vulnerability Index Scores

Table C-2 summarizes the input data, and, in the final 

two columns, the output of the NSVI. Each column 

represents an exposure or sensitivity factor with a 

rating (e.g., greatly increased, somewhat decreased) 

that indicates how that factor is expected to affect the 

species’ overall vulnerability to climate change. We 

assigned these ratings based on the information 

collected for each species and the model’s published 

guidelines that define the rating categories for each 

factor.

When applying the NSVI:

• Exposure to local climate change (predicted 

changes in temperature and Hamon AET:PET) 

was based on climate predictions made at the 

scale of the full assessment area (i.e., the 

Olympic Peninsula), rather than at the scale of 

individual species’ ranges, because the full 

assessment area provided the most meaningful 

downscaled estimates (Halofsky 2010). 

Therefore, exposure ratings are the same for 

all six species.

• Most of the factors describing indirect 

exposure to climate change were rated neutral 

and did not affect the index scores.

• Factors describing sensitivity to climate 

change often received ratings that spanned 

multiple levels (e.g., neutral to somewhat 

increase) owing to a lack of specific data in 

the scientific literature. Rating specificity was 

lowest for the least-studied species.

In the following sections, we discuss the scores 

calculated for each species, with special attention to 

the factors that had the greatest impact on each 

species’ vulnerability score. 

Whitebark Pine

Whitebark pine is a slow-growing species adapted to 

survival in high mountains; it often occurs in climax 

communities around timberline (Arno and Hammerly 

2007). Across its range it is threatened by one or more 

of the following: white pine blister rust, mountain pine 

beetle, fire (too much or too little) and climate change 

(Aubry et al. 2008). The NSVI scored whitebark pine 

as highly vulnerable to climate change. Of the 17 

vulnerability and sensitivity factors, 1 factor greatly 

increased the species’ vulnerability score, 4 factors 

increased its vulnerability score, and 3 factors 

somewhat increased its vulnerability score (table C-2).

The NSVI elevated whitebark pine’s vulnerability 

score from moderately vulnerable to highly vulnerable

based on the species’ indirect exposure to climate 

change, specifically its distribution relative to natural 

topographic or geographic barriers. On the Olympic 

Peninsula, whitebark pine occurs only on peaks in the 

northeastern rainshadow (appendix B), and predicted 

increases in temperature by 2050 could substantially 

reduce its habitat there. The barrier to a potential shift 

in its range lies in the fact that the Olympic whitebark 

pine already occurs at the highest elevations in its 

range, and it therefore cannot track an upward-moving 

climate envelope. 

Whitebark pine’s modeled response to climate change 

also increased its overall vulnerability score. 

Multivariate spatio-temporal clustering (MSTC) 

models (Hargrove and Hoffman 2005, Hargrove et al. 

2010) and tree climate viability maps (TCVM) 

(Rehfeldt et al. 2006, 2009) indicate that whitebark 

pine’s habitat range is likely to be reduced under 

predicted climate scenarios. While the species cannot 

shift to higher elevations in the Olympic Range, shifts 

in habitat may occur within its current range, from 

south-facing slopes where it is presently most 

common, to cooler, north-facing slopes (Millar at al. 

2004).

The NSVI increased whitebark pine’s vulnerability 

score as a result of its historical thermal niche. This 

factor is based on mean seasonal temperature variation 

during the past 50 years; it is calculated as the 
C-6 Climate Change and Forest Biodiversity in Western Washington

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difference between the highest annual mean monthly 

maximum temperature and the lowest annual mean 

monthly minimum temperature. This value is used as 

an indication of a species’ broad-scale tolerance of 

temperature variation. For the range of whitebark pine 

in the Olympics, we estimated seasonal temperature 

variation to be 45 °F (25 °C). This relatively small 

value contributed to an increase in the overall 

vulnerability score of whitebark pine, according to the 

rating levels for the historical thermal niche factor. 

However, the rating for this factor is based on the 

range of annual temperature variation across the 

continental United States. The coastal Pacific 

Northwest has the least annual variation in 

temperature, comparable to that of southern Florida. 

Therefore, all species in this region receive a rating 

that increases vulnerability.

Whitebark pine’s vulnerability score also was 

increased by its historical hydrological niche. Unlike 

historical thermal niche, which is calculated from 

mean seasonal variation, historical hydrological niche 

is calculated from the spatial variation in mean annual 

precipitation within a species’ range in the 

management area. The lowest 50-year mean annual 

precipitation value in the species’ range is subtracted 

from the highest 50-year value. Whitebark pine’s 

vulnerability score was increased as a result of a 

difference in annual precipitation between 4 and 10 in 

(10 and 25 cm) within its range on the Olympic 

Peninsula.

Whitebark pine’s near-complete dependence on a 

single species for propagule dispersal also increased its 

vulnerability score. Seed of whitebark pine is 

dispersed primarily by Clark’s nutcracker (Nucifraga 

columbiana) (Lorenz at al. 2008); thus, changes in the 

distribution or density of Clark’s nutcracker would 

have a substantial impact on dispersal of whitebark 

pine seed.

The somewhat low genetic variation of whitebark pine 

in the Olympic Range (Bower et al., n.d.) further 

increased its vulnerability score. The NSVI associates 

low genetic variation with increased vulnerability to 

climate change based on the assumption that low 

genetic variation reduces a species’ ability to evolve in 

response to environmental changes. Genetic variation 

of whitebark pine both within and among populations 

of the Olympic Peninsula is lower than in the rest of 

the range of the species, possibly due to lower gene

flow resulting from the geographic isolation of these 

populations.

Anticipated change in disturbance regime also 

increased whitebark pine’s NSVI score, albeit to a 

lesser extent than the aforementioned factors. 

Examples of disturbance regimes include periodic 

fires, floods, severe winds, pathogen outbreaks, and 

similar events. Given the predicted stress of climate 

change, whitebark pine is expected to become more 

susceptible to damage from white pine blister rust. 

White pine blister rust is caused by Cronartium 

ribicola, an injurious, non-native fungi already present 

on whitebark pine throughout its limited range in the 

Olympics.

Golden Chinquapin

Golden chinquapin is an medium-sized, evergreen, 

broadleaf tree occurring to a very limited extent on the 

Olympic Peninsula (Arno and Hammerly 2007) 

(appendix B). The NSVI assigned golden chinquapin a 

score of moderately vulnerable. Four factors had the 

greatest influence on this vulnerability score: historical 

thermal and hydrological niches, limited dispersal 

ability, and low genetic variation. 

Historical thermal niche increased the vulnerability 

score of golden chinquapin as a result of relatively low 

historical seasonal variation of temperature within its 

limited range on the Olympic Peninsula. Because 

historical hydrological niche is calculated from spatial 

variation in mean annual precipitation, and because 

golden chinquapin occurs only in a very small area on 

the Olympic Peninsula, the small amount of 

precipitation variation within that area increased its 

vulnerability score.

It appears that golden chinquapin on the Olympic 

Peninsula frequently reproduces via vegetative shoots, 

and its dispersal ability is therefore very limited. 

Limited dispersal ability increased golden 
Climate Change and Forest Biodiversity in Western Washington C-7

7

chinquapin’s NSVI score because it lacks the capacity 

to migrate and follow a shifting climate envelope. The 

fourth major factor that contributed to the moderately 

vulnerable score for golden chinquapin was low 

genetic variation. Because the Olympic Peninsula 

population of golden chinquapin is a disjunct 

population and frequently reproduces vegetatively, it 

might have arisen from a single individual or a small 

number of individuals. Therefore, we made the 

assumption that genetic variation in this population 

was relatively low, although quantitative data do not 

exist at this time.

Pacific Yew

Pacific yew is a small coniferous tree adapted to shady 

conditions in the understory of conifer forests; it is 

most prevalent in the older forests of the coastal 

Pacific Northwest Arno and Hammerly 2007. The 

NSVI scored Pacific yew not vulnerable to climate 

change. Given that most factors were neutral or 

unknown, only one factor, historical thermal niche, 

clearly increased Pacific yew’s vulnerability score. 

Physiological thermal niche, which quantifies a 

species’ tendency to occupy relatively cool microsites, 

had a neutral to somewhat increasing effect on its 

vulnerability score. Although Pacific yew tolerates a 

wide temperature range, it is sensitive to excessive 

heat and sometimes requires the protection of larger 

trees. Alternatively, historical hydrological niche 

somewhat decreased Pacific yew’s vulnerability score; 

this rating resulted from the wide variation in mean 

annual precipitation across Pacific yew’s range on the 

Olympic Peninsula.

Pacific yew’s disturbance regime specificity and 

interspecific dependence factors had a neutral to 

somewhat increasing effect on its vulnerability score. 

Owing to the combination of its susceptibility to fire 

damage and its increased prevalence in latesuccessional forests, greater fire frequency (which is 

one outcome predicted by some climate models) could 

adversely affect Pacific yew on the Olympic 

Peninsula. Pacific yew also could be affected by the 

loss of habitat provided by late-successional trees if 

disturbances associated with climate change, including 

insects and pathogens, caused mortality among the 

late-successional trees.

Modeled response to climate change had a somewhat 

increasing effect on Pacific yew’s vulnerability score, 

based on MSTC and TCVM models which predicted 

moderately small decreases in Olympic Peninsula 

habitat (Hargrove and Hoffman 2005, Hargrove et al. 

2010, Rehfeldt et al. 2006, 2009).

Western White Pine

Scattered through low- and middle-elevation forests, 

western white pine is a large tree that regenerates best 

following major disturbances Arno and Hammerly 

2007. The NSVI scored western white pine not 

vulnerable to climate change. As in the case of Pacific 

yew, because most exposure and sensitivity factors 

were neutral or unknown, only historical thermal niche 

and modeled response to climate change had 

increasing effects on its vulnerability score.

Western white pine’s disturbance regime specificity 

had a neutral to somewhat decreasing effect on its 

vulnerability score, because stand-replacing 

disturbances conducive to western white pine 

regeneration are projected to occur with greater 

frequency as a result of climate change in some 

climate change models. A major source of disturbance, 

and the greatest threat to western white pine in 

Washington, is white pine blister rust. However, it is 

unclear how projected climate changes will influence 

the effects of this pathogen in low- and middleelevations forests. Given that western white pine 

already has experienced high levels of mortality as a 

result of white pine blister rust, planting rust-resistant 

seedlings is crucial to its survival. This management 

imperative is not considered by the NSVI, nor does its 

rating of not vulnerable account for the differing 

effects of multiple disturbance regimes.

Oregon White Oak

Oregon white oak is a stout, deciduous tree, capable of 

surviving on a wide range of sites; it is found most 

frequently in lowland areas that were historically 

burned by Native Americans (appendix A). The NSVI 
C-8 Climate Change and Forest Biodiversity in Western Washington

8

scored Oregon white oak not vulnerable to climate 

change. Beyond historical thermal niche, genetic 

variation was the only factor that increased Oregon 

white oak’s vulnerability score.

Oregon white oak’s level of genetic variation 

somewhat increased its vulnerability score based on 

the fact that the species’ genetic variation was rated 

low compared to related taxa (Ritland at al. 2005). 

Oregon white oak’s genetic variation is approximately 

half that of other white oak (Quercus subgenus 

Leucobalanus) species. Within the state of 

Washington, genetic differences among Oregon white 

oak populations are not significant (Taylor and Boss 

1975). 

Ratings for many of Oregon white oak’s sensitivity 

and vulnerability factors were neutral or included the 

neutral rating. In the NSVI, a neutral rating affects the 

vulnerability score differently than a rating of 

unknown. While a rating of unknown indicates a lack 

of information and does not affect a species’ 

vulnerability score, a neutral rating is often based on 

specific information indicating that the species’ level 

of sensitivity or exposure has no anticipated impact on 

its vulnerability score. For example, the neutral impact 

of Oregon white oak’s dispersal ability on its overall 

vulnerability score was based on evidence that 

dispersal of acorns by Steller's jays (Cyanocitta 

stelleri) and small mammals often exceeds a distance 

of 328 ft (100 m) but rarely exceeds 3,280 ft (1,000 

m); the NSVI assigns this dispersal range a rating of 

neutral.

Quaking Aspen

Quaking aspen is a small- to medium-sized deciduous 

tree that often regenerates by sprouting; it occurs in 

widely scattered groves in western Washington Arno 

and Hammerly 2007 (appendix B). The NSVI scored 

quaking aspen moderately vulnerable to climate 

change. Factors increasing its vulnerability score 

included historical thermal niche, historical 

hydrological niche, and dispersal ability. As with 

golden chinquapin, historical hydrological niche 

increased its vulnerability score solely owing to the 

species’ limited range on the Olympic Peninsula.

The clumped distribution and the limited extent of 

individual quaking aspen populations on the Olympic 

Peninsula suggest that they are reproducing primarily 

through vegetative mechanisms. This limited 

propagule dispersal ability had an increasing to greatly 

increasing effect on quaking aspen’s vulnerability 

score. Quaking aspen’s vegetative reproduction also 

influenced its genetic variation factor, which 

somewhat increased the vulnerability score.
Climate Change and Forest Biodiversity in Western Washington C-9

9

THE NATURESERVE 

VULNERABILITY INDEX AS AN 

ASSESSMENT TOOL FOR TREES 

OF WESTERN WASHINGTON

Availability and Quality of Data

The validity of the NSVI score depends on the 

availability of information on a wide range of 

exposure and sensitivity and vulnerability factors. For 

less-studied species, much of this information remains 

unknown. The creators of the NSVI recognized this 

issue and designed the index so that it would function 

with a partial dataset. A vulnerability score is obtained 

with a minimum of 10 of the 17 sensitivity factors and 

three of the four indirect climate change exposure 

factors. All four exposure factors describing 

documented or modeled climate change response are 

optional. However, a vulnerability score that is based 

on the minimum number of factors is likely less 

reliable than one that is based on a well-studied 

species for which all factors are rated. This is further 

complicated by the fact that it is unclear how the 

model weights the various factors. If some factors are 

weighted more heavily, it may be appropriate for the 

user to devote more time to accurately rating those 

factors.

In addition to the overall vulnerability score for each 

species, the model includes a measure of confidence in 

the score (table C-2). This confidence level ranges 

from low to very high and is based, in part, on the 

specificity of the user-provided information. The 

NSVI allows the user to select up to three ratings for a 

single factor (e.g., increased – somewhat increased –

neutral) to accommodate uncertainty in the data or to 

account for variation in sensitivity or vulnerability 

within the species’ range. Confidence generally 

increases when fewer ratings are selected within each 

factor (i.e., greater specificity) and when the selected 

ratings are relatively consistent among factors. In the 

case of whitebark pine, the model returned a 

confidence level of very high for its score of highly 

vulnerable. This high degree of confidence resulted 

from the fact that a relatively large number of factors 

had specific ratings of somewhat increased 

vulnerability, increased vulnerability, or greatly 

increased vulnerability.

Climate Sensitivity Calculations

The NSVI predicts sensitivity of each species to 

temperature and precipitation changes based on 

historical climate exposure and other species 

information. However, several aspects of the 

sensitivity rating system are difficult to interpret and 

not well-suited to the climate of western Washington.

The NSVI’s approach to calculating sensitivity to 

climate at multiple scales is not intuitive. Historical 

thermal niche is based on seasonal temperature 

variation, while historical hydrological niche is based 

on spatial precipitation variation. Conversely, 

physiological thermal niche is based on spatial 

temperature patterns (i.e., a species’ preference for 

cool microsites), while physiological hydrological 

niche is based, in part, on the extent to which seasonal 

precipitation patterns affect habitat. Historical thermal 

and hydrological niches are defined quantitatively, but 

sensitivity to seasonal precipitation patterns, which 

may be more susceptible to climate change and more 

relevant in the Pacific Northwest, is assessed 

qualitatively as physiological hydrological niche.

Historical thermal and hydrological niches have 

substantial influences on a species’ vulnerability score, 

as the NSVI equates the breadth of a species’ thermal 

and hydrological niches with its ability to adapt to 

changes in temperature and precipitation. However, 

the vulnerability rating system for all geographic 

regions is based on a single set of predefined 

temperature and precipitation levels. These predefined 

levels have questionable value in locations where 

temperature or precipitation differs significantly from 

those of a typical temperate ecosystem. For example, a 

species’ historical hydrological niche is rated as 

increasing its overall vulnerability score if the 

variation in mean annual precipitation across its range 
C-10 Climate Change and Forest Biodiversity in Western Washington

10
Climate Change and Forest Biodiversity in Western Washington C-11

11

in the management area is between 4 and 10 in (10 and 

25 cm). This relatively narrow range is probably not 

appropriate on the Olympic Peninsula, where mean 

annual precipitation can vary dramatically over short 

distances. Alternatively, some species such as golden 

chinquapin occupy a very limited range on the 

Olympic Peninsula and, because precipitation varies 

little within their range, receive an increased 

sensitivity rating. This is rating approach is based on 

the assumption that climate limits a species’ range, 

rather than competition from other species or other 

types of barriers. For golden chinquapin and Oregon 

white oak, for example, competition from conifers 

may be the most important factor limiting their ranges 

on the Olympic Peninsula.

Effects of Disturbance

The NSVI includes disturbance effects to the extent 

that a species may be dependent on a specific 

disturbance regime that could be affected by climate 

change. Examples of this are regular occurrences of 

wildfire or flooding. The NSVI does not, however, 

address the potential initiation of new types of 

disturbance, including introductions of non-native 

insects and diseases. Furthermore, native insects and 

diseases are likely to expand their range in response to 

climate change, significantly affecting areas where 

they did not exist historically. One dramatic example 

of this is the northward expansion of mountain pine 

beetle’s (Dendroctonus ponderosae) range (Logan and 

Powell 2001). These new disturbance regimes may 

occur cyclically once they are initiated, but they are 

not necessarily part of current or historical disturbance 

cycles and thus are not addressed by the NSVI 

disturbance specificity factor.

Genetics

Genetic vulnerability to climate change is addressed 

by only one factor, genetic variation relative to similar 

taxa, which is measured by selecting one of four 

qualitative levels ranging from very low to high. The 

NSVI guidelines state that genetic variation should be 

measured over a substantial portion of a species’ 

range. However, the genetic variation factor does not 

assess whether the population in the management area 

is contiguous with the broader range of the species. 

For whitebark pine, golden chinquapin, and quaking 

aspen, the genetic variation of the disjunct populations 

on the Olympic Peninsula and their ability to adapt is 

affected by the lack of opportunity for gene flow with 

populations beyond the management area. For forest 

trees it would also improve the index to include a 

factor reflecting the patterns of genetic variation across 

the landscape. These patterns vary widely among the 

tree species of the Olympic Peninsula (Randall and 

Berrang 2002) and will affect each species’ ability to 

adapt to future changes in climate.

Age-Dependent Sensitivities

A problematic aspect of the NSVI is its handling of 

species with temperature or precipitation sensitivities 

that change with age. This was a recurrent issue for us 

when assigning sensitivity and vulnerability ratings to 

tree species. For example, some drought-tolerant tree 

species, such as Oregon white oak, require moist soils 

to germinate and survive as seedlings. Because 

summer precipitation levels are projected to decline in 

predicted climate change scenarios, this requirement 

increases the sensitivity rating for Oregon white oak’s 

physiological hydrological niche. However, Oregon 

white oak’s drought tolerance at maturity favors its 

competitive ability in forest stands where it occurs 

among tree species that are less drought-tolerant, thus 

decreasing its sensitivity rating. Although this apparent 

discrepancy in sensitivity is understood by managers, 

the NSVI is not designed to include this level of detail. 

In this situation, the best compromise is for the user to 

select multiple sensitivity ratings. However, such 

compromises reduce the NSVI’s confidence score and 

also likely reduce the user’s confidence in the NSVI.
C-12 Climate Change and Forest Biodiversity in Western Washington

12

Practical Applications for the Index

The NSVI score for each species indicates its overall 

level of vulnerability; however, management actions to 

alleviate vulnerabilities to climate change must be 

based on specific types of vulnerabilities, such as 

shifting climate envelopes and altered disturbance 

regimes. The NSVI results summary table (table C-2) 

is useful in that respect, as it shows patterns in 

sensitivity and vulnerability factors across multiple 

species. For example, the two species with increased 

vulnerability associated with dispersal ability, golden 

chinquapin and quaking aspen, are the only two 

species that are reproducing primarily through 

vegetative mechanisms. Also evident in the table is a 

pattern indicating that low genetic variation within five 

of the six modeled species contributes to their 

vulnerability. Grouping species by vulnerability 

factors would likely be most useful to managers if a 

large number of species were modeled. For example, if 

all tree species within a forest were modeled, the

resulting groupings would assist in understanding 

potential changes in composition of each forest cover 

type.

The process of compiling and critically evaluating 

species-level data on exposure, sensitivity, and 

documented response to climate change may, for some 

applications, be a more important product of the Index 

than the vulnerability score itself. To understand the 

potential effects of a changing climate on biodiversity, 

this information must be collected regardless of 

whether it is used in the NSVI or interpreted through a 

different approach. However, the NSVI provides a 

template for a logical method of organizing this 

information, facilitating comparisons of sensitivity and 

vulnerability factors within species and across multiple 

species. To further improve its applicability, a user 

could simplify the NSVI’s rating system and 

customize the results table based on the species and 

management area of interest, incorporating only the 

sensitivity and vulnerability factors deemed relevant or 

adding factors not included in the original NSVI. This 

approach would bypass the calculation of an overall 

vulnerability score for each species, but it would 

enable the user to interpret the species data directly 

from a table similar to table C-2.

Conclusions

In its present form, the NSVI has limited utility for 

assessing the vulnerability of plant species on 

Washington’s national forests.

• The NSVI is designed to work with a wide 

range of plant and animal species; as a result, 

the sensitivity and vulnerability factors on 

which it is based are too general and, in some 

instances, not directly applicable to plant 

species of Washington’s national forests.

• The NSVI is useful in that it provides a 

template for collecting the wide range of 

information that is needed to understand each 

species’ vulnerabilities to projected changes in 

climate. We found that this template should be 

viewed as a starting point, as it would have to 

be modified to become a more effective tool 

for our management area. 

• Ranking of species by vulnerability score must 

be followed by addressing the types of 

management actions that might be necessary 

to mitigate the potential effects of climate 

change. It would be useful to use vulnerability 

data to identify common themes in 

vulnerability that could then be managed more 

efficiently.
Climate Change and Forest Biodiversity in Western Washington D-1

1

APPENDIX D:

EVALUATION OF THE CLIMATE CHANGE 

SENSITIVITY DATABASE
D-2 Climate Change and Forest Biodiversity in Western Washington

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BACKGROUND

The Climate Change Sensitivity Database (CCSD) is 

part of the Pacific Northwest Climate Change 

Vulnerability Assessment, a project designed to 

evaluate the relative climate change vulnerability of 

the species and ecological systems of the Pacific 

Northwest. The Pacific Northwest Climate Change 

Vulnerability Assessment is a collaborative effort of 

the University of Washington and numerous other 

agencies (Lawler and Case 2010a). It includes the 

CCSD, which is designed to evaluate the climate 

change sensitivity of individual species, and spatially 

explicit computer models that include downscaled 

climate projections, simulations of vegetation change, 

and assessments of climate change effects on habitat 

and distribution of focal wildlife species.

The CCSD is a web-based model for predicting the 

sensitivity of animal and plant species to climate 

change. The model user rates a species’ sensitivity 

using eight biological and ecological variables, each of 

which is assigned a value between 0 and 7 (fig. D-1). 

Based on these ratings, the CCSD calculates a climatechange sensitivity index score between 0 and 100. The 

variables include a species’ dispersal capability, its 

physiological ability to cope with changes in climate, 

and several ecological factors related to its habitat 

requirements. Unlike the NatureServe Climate Change 

Vulnerability Index (NSVI), the CCSD does not 

incorporate historical climate data or future climate 

projections. The CCSD allows the user to customize 

the weighting of each variable in the index score 

calculation, assigning greater influence to the variables 

that are deemed most important. In addition to rating 

sensitivity for each variable, users also must rate their 

level of confidence in their sensitivity rating, on a 

scale of 1 to 5 (1 being low confidence, 5 being high). 

This produces two scores for each species: an overall 

sensitivity score and a confidence score.

The CCSD is available online for public use; after 

creating a profile, users may then begin rating the 

sensitivity of animal or plant species of their choice or 

view the results of other users’ species evaluations. 

The model includes a section in which the user may 

justify each rating by adding relevant text and listing 

references. All entered data are stored and visible to 

other users on the model’s website. The model 

interface is straightforward, and the equations used to 

calculate index scores are shown on the website.
Climate Change and Forest Biodiversity in Western Washington D-3

3

Figure D-1. Editing the dispersal distance and dispersal barriers variables in the CCSD
D-4 Climate Change and Forest Biodiversity in Western Washington

4

APPLYING THE CLIMATE 

CHANGE SENSITIVITY 

DATABASE TO TREE SPECIES 

OF THE OLYMPIC PENINSULA

We applied the CCSD to the six tree species to which 

we also applied the NSVI: whitebark pine, golden 

chinquapin, Pacific yew, western white pine, Oregon 

white oak, and quaking aspen. As with the NSVI, we 

limited the scope of the evaluation to Washington’s 

Olympic Peninsula. The species information required 

to run the CCSD was acquired from Silvics of North 

America (Burns and Honkala 1990) and the Fire 

Effects Information System (Fischer 2010). The goals 

of this evaluation were: (1) assess the CCSD’s 

applicability to tree species representing a range of 

management challenges, and (2) compare both the 

process of applying the model and the model’s results 

to the NSVI.

Sensitivity ratings for each variable, as well as the 

model’s calculated sensitivity and confidence index 

scores, are shown in table D-1. Equal weighting was 

assigned to each variable (the model’s default setting) 

for the purpose of this evaluation. One species, 

whitebark pine, had a relatively high sensitivity index 

score of 80. Scores for all other species fell within a 

narrow range: from 42 to 46. Confidence scores also 

fell within a narrow range of 67 to 77. 

In the following sections, we discuss each of the eight 

variables used to calculate the index scores and 

describe the ratings for each species. 

Table D-1. Summary of the Climate Change Sensitivity Database, including user-assigned ratings for eight 

variables and sensitivity and confidence index scores for six selected tree species on the Olympic 

Peninsula

Species

Sensitivity ratings, by variable

Index

results

Dispersal distance1

Dispersal barriers2

Disturbance regimes3

Generalist/specialist4

Physiology5

Life history6

Habitat7Subjective ranking8Sensitivity index 

scoreConfidence index

Pinus albicaulis 

Whitebark pine 7 7 2 6 6 5 7 6 80 75

Chrysolepis chrysophylla 

Golden chinquapin 7 6 5 2 2 4 0 1 42 73

Populus tremuloides 

Quaking aspen 7 5 5 3 4 1 0 2 45 68

Taxus brevifolia 

Pacific yew 7 4 0 5 4 5 0 4 44 68

Pinus monticola 

Western white pine 7 5 6 3 3 2 0 2 46 67

Quercus garryana 

Oregon white oak 7 6 6 2 2 5 0 1 45 77

1 1 = less than 1 km/yr ; 7 = greater than 100 km/yr

2 0 = no barriers; 7 = many barriers

3 0 = not associated with any disturbance regime; 7 = highly dependent on one or more disturbance regimes

4 1 = generalist; 7 = specialist

5 1 = low sensitivity; 7 = high sensitivity 6 1 = r-selected species; 7 = K-selected species 7 0 = does not occupy sensitive habitats; 7 = occupies a sensitive habitat

8 0 = not sensitive; 7 = extremely sensitive
Climate Change and Forest Biodiversity in Western Washington D-5

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Dispersal Distance

The dispersal distance variable quantifies “the 

maximum distance a species can move within one year 

to establish territory.” A sensitivity rating of 7 is 

associated with a distance of less than 1 km per year, 

and, at the other end of the scale, a rating of 1 is 

associated with a distance of greater than 100 km per 

year. The tree species in this evaluation require 

multiple years to reach reproductive maturity, and 

after reaching maturity, most disperse seed distances 

of less than 1 km. Averaging their seed dispersal 

distance over the number of years until reproductive 

maturity is reached, the mean annual dispersal distance 

is clearly less than 1 km, and thus we assigned a rating 

of 7 to every species.

Dispersal Barriers

Dispersal barriers are defined as landscape elements 

that would prevent a species from migrating in 

response to a changing climate. The rating scale ranges 

from 0 (no barriers) to 7 (many barriers). Although the 

CCSD lists 11 examples of barriers (e.g., roads, 

clearcuts, dams) that may be selected by the user, these 

do not influence the rating. The model user must 

decide what barriers exist, how severe the barriers are, 

and how to quantify them on a scale of 0 to 7.

For the six tree species evaluated, applicable dispersal 

barriers included topography, land use (e.g., 

urbanization, agriculture), and vegetation. All the 

selected tree species, with the exception of Pacific 

yew, are most prevalent in pioneer or early seral 

stands. Mature conifer forests may hinder or prohibit 

migration of these species, and thus we assigned 

relatively high ratings of 5 or greater for the dispersal 

barrier variable. By contrast, Pacific yew, assigned a 

rating of 4, is most prevalent in mature conifer stands, 

although it can also regenerate post-disturbance. For 

whitebark pine, we assigned a rating of 7 owing to the 

fact that the species occurs only at high elevations in 

the Olympic Range and thus topography prevents 

migration to higher elevations under a warmer climate.

Disturbance Regimes

The disturbance regime variable is rated according to

the dependence of the species on the nature of one or 

more specific disturbance regimes. The rating scale 

includes values of 0 (not associated with any 

disturbance regime) to 7 (highly dependent on one or 

more disturbance regimes). We assigned ratings 

ranging from 0 to 6 for the 6 tree species. For Pacific 

yew, a species that becomes more prevalent with 

increasing stand age and is most common in oldgrowth stands, we assigned a rating of “N/A” (a value 

of 0) because the species does not depend on the 

nature of a specific type of disturbance. We assigned 

western white pine and Oregon white oak ratings of 6. 

Both species thrive under disturbance: western white 

pine regenerates best following stand-replacing fire, 

while Oregon white oak is very tolerant of fire and 

depends on periodic fire to eliminate competition from 

other tree species.

Generalist/Specialist

For the generalist/specialist variable, the model user 

rates a species on a scale of 1 (generalist) to 7 

(specialist) based on its ecological niche. The model 

user also may select, from a list, specific factors such 

as “seed dispersal dependency” and “pollinator 

dependency” that describe the nature of a species’ 

specialist niche. However, selection of these factors 

does not affect the species’ score.

We assigned relatively low values (i.e., 2 or 3) to the 

early seral, low- to mid-elevation species because they 

are capable of establishing and surviving on a 

relatively wide range of sites following disturbance. 

Alternatively, we assigned Pacific yew a 

generalist/specialist rating of 5 owing to the fact that it 

is found primarily in the understory of mature conifer 

forests. We assigned whitebark pine a rating of 6 

based on its relatively narrow ecological niche on the 

Olympic Peninsula.
D-6 Climate Change and Forest Biodiversity in Western Washington

6

Physiology

For the physiology variable, species are rated based on 

their physiological sensitivity to environmental 

changes that are likely to occur under projected 

climate change, such as temperature, precipitation, pH, 

and carbon dioxide concentration. The rating scale 

ranges from 1 (low sensitivity) to 7 (high sensitivity). 

We assigned Oregon white oak and golden chinquapin 

ratings of 2 because both of these species can survive 

on hot, droughty sites, and the Olympic Peninsula 

populations are at or near the northern ends of their 

range. These species are likely to be least sensitive to 

increased summer temperature or drought. We 

assigned Pacific yew, western white pine, and quaking 

aspen physiological sensitivity ratings of 4, 3, and 4, 

respectively; as with Oregon white oak and golden 

chinquapin, these species’ ranges encompass regions 

that are hotter and drier than the Olympic Peninsula. 

Owing to the fact that it occupies only cold, highelevation habitat that is likely to shrink if air 

temperatures increase, we assigned whitebark pine a 

sensitivity rating of 6.

Life History

The life history variable represents the continuum 

between r-selected species (a rating of 1) and Kselected species (a rating of 7). Not all trees are easily 

classified on this scale; for example Pacific yew is a 

long-lived, slow-growing, shade-tolerant species, 

which are traits of a K-selection strategy; however, it 

also is a prolific producer of relatively small seed, 

indicating an r-selection strategy. We assigned Pacific 

yew a rating of 5. Whitebark pine is a long-lived, 

slow-growing species that produces relatively large 

seed, and thus, we assigned it a rating of 5 despite the 

fact that it is considered a pioneer or early seral 

species on many sites. Because Oregon white oak is 

long-lived, slow-growing, produces large seed, we also 

assigned it a rating of 5. Alternatively, we assigned 

quaking aspen a rating of 1 because it is a short-lived 

pioneer species and a prolific producer very small 

seed.

Habitat

The habitat variable assigns a rating based on whether 

the species depends on one of six listed sensitive 

habitats. Sensitive habitats include coastal marshes and 

estuaries, perennial streams, shallow pools, seasonal 

wetlands, ecotones, alpine/subalpine habitat, and an 

“other” category for sensitive habitats not on this list. 

Unlike the other variables, which are rated on a scale 

ranging from 0 to 7, habitat is assigned a score of 

either 0 or 7 based on whether the species occupies 

any of the sensitive habitats (7) or not (0). Whitebark 

pine occurs in subalpine habitat, which is one of the 

listed sensitive habitat types; therefore, we assigned it 

a rating of 7. The other species were not dependent on 

sensitive habitat types, and we assigned them each a 

rating of 0.

Subjective Ranking

The final variable in the model, called subjective 

ranking, is based on the user’s answer to the question, 

“In your opinion, how would you rank the overall 

sensitivity of this species to climate change?” In 

response to this question the user selects a value from 

0 (not sensitive) to 7 (extremely sensitive). This 

variable allows the model user to consider all 

ecological factors influencing climate change 

sensitivity, including factors that may not be 

quantified by the other variables.

We assigned whitebark pine a rating of 6 for its

subjective ranking, owing to the limited and 

potentially decreasing extent of its habitat. We 

assigned Pacific yew a rating of 4, owing to the fact 

that it is primarily found in the understory and thus is 

somewhat dependent on the presence of mature conifer 

forests; shifts in the distributions of overstory conifers, 

or other canopy disturbances associated with climate 

change, could affect the habitat of Pacific yew. We 

assigned the four remaining species ratings of 1 or 2 

owing to the fact that they are relatively tolerant of 

warmer conditions and of disturbance.
Climate Change and Forest Biodiversity in Western Washington D-7

7

THE CLIMATE CHANGE 

SENSITIVITY DATABASE AS AN 

ASSESSMENT TOOL FOR TREE 

SPECIES OF WESTERN 

WASHINGTON

The CCSD is a flexible index that produces scores 

based on general information about a species. The 

generality of the CCSD makes it applicable to both 

animals and plants, although it might be better-suited 

to rating the sensitivity of animals. For example, 

dispersal distance ratings appear to be calibrated for 

animal species, rather than for plants. Likewise, the 

ecological concept of r- and K-selection is more 

applicable to differentiating the reproductive strategies 

animal species than it is to differentiating that of tree 

species.

With the exception of the dispersal distance and 

habitat variables, the scale on which the CCSD’s 

sensitivity variables are rated is qualitative rather than 

quantitative. The model user assigns a value from 0 to 

7, based on the user’s assessment of a species’ 

sensitivity. These values are presented as a continuum, 

rather than as a series of defined classes. As a result, it 

is unlikely that two equally knowledgeable users 

would assign the same values to the full set of 

sensitivity variables for a given species. Thus, ratings 

among multiple species are likely to be more 

consistent, and more comparable, if they are made by 

the same individual or by the same team. Similarly, it 

may not be appropriate to compare confidence ratings 

beyond the species assessed by a single individual or 

team.

The CCSD’s simplified approach to assessing a 

species’ sensitivity made it challenging to rate the 

physiology variable for tree species. The physiology 

variable is defined as “...a species’ physiological 

ability to tolerate changes in temperature, 

precipitation, salinity, pH, and CO2...” (Lawler and 

Case 2010b). However, this does not account for the 

fact that if several of these variables change, their 

effects may be both positive and negative. For 

example, increased temperature may have a negative 

effect on a tree species’ survival and growth, while 

simultaneous increases in precipitation and CO2 may 

have positive effects on the species’ growth. 

Therefore, we interpreted the physiology variable as 

the species’ ability to tolerate changes in the single 

environmental variable most likely to impede survival 

and growth. Conversely, the simplified approach of the 

CCSD bypassed one problem of the more detailed 

NSVI: the difficulty of rating age-dependent 

sensitivities exhibited by many tree species was not 

encountered when using the CCSD model.

The CCSD’s disturbance regime variable also was 

difficult to interpret. The variable was defined as the 

dependence of a species on the nature of one or more 

specific disturbance regimes that may be affected by 

climate change. However, this definition refers only to 

the level of dependence on a disturbance regime rather 

than the frequency or intensity of the disturbance or 

the degree to which climate change is expected to 

affect that disturbance. Thus, a species strongly 

dependent on frequent disturbance may be assigned 

the same rating as a species strongly dependent on a 

very long interval between disturbances.

As result of its broad scope and simplicity of use, the 

strength of the CCSD is its capacity to make general 

evaluations of climate change sensitivity across a wide 

range of species and life forms. While the model 

identified sensitivity differences among the six tree 

species, the categories did not specify individual 

factors such as genetic variation or temperature and 

drought sensitivities. Some of the eight variables in the 

model, such as physiology and generalist/specialist, 

require the user to assign a single rating based on 

multiple factors. Using the generalist/specialist 

variable as an example, these factors include seed 

dispersal dependency, pollinator dependency, and 

phenological dependency. Given our objective of 

evaluating the climate change sensitivity of a relatively 

small number of tree species on the Olympic 

Peninsula, a more practical approach for managers 

would be to compare the individual factors

contributing to each variable’s rating. Based on the 
D-8 Climate Change and Forest Biodiversity in Western Washington

8

same data, this approach would result in a more 

mechanistic evaluation of sensitivity.

Conclusions

Our application of the CCSD to six tree species of the 

Olympic Peninsula revealed several key features of the 

index:

• The CCSD is simple and easy to use, 

assuming basic ecological information is 

available for each species. It does not require 

historical climate data, although a basic 

knowledge of projected future climate is 

required.

• The CCSD index is based primarily on broad 

ecological concepts (e.g., generalist/specialist, 

r/K selection) rather than on information on 

specific traits.

• Owing to the lack of quantitative guidelines in 

the rating process, the results of the CCSD are 

dependent on the user’s interpretation of the 

rating scales. While scores are comparable 

within and among species assessed by the 

same user or team, ratings from different 

model users may not be comparable.
Climate Change and Forest Biodiversity in Western Washington E-1

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APPENDIX E:

CLIMATE DATA ANALYSIS
E-2 Climate Change and Forest Biodiversity in Western Washington

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INTRODUCTION

In an earlier draft of the vulnerability assessment for 

forest tree species in Group 1 (Part 1), we developed a 

sixth risk factor, climate pressure, to quantify the 

relative risk of climate change to tree species in our 

analysis. This risk factor was based on the one 

described by Potter and Crane (2010). A number of 

reviewers enumerated the challenges in applying the 

models on which this risk factor is based. Upon further 

consideration we decided to drop this factor from the 

vulnerability assessment. Here we present both the 

process we used to develop the climate pressure factor 

and the characteristics of the models that made the 

results too uncertain to include in the analysis.

METHODS

Climate Pressure Factor

As designed by Potter and Crane (2010), this factor 

identifies the relative risk to each forest tree species 

due to the potential change in distribution or climate 

habitat as climate conditions change. Here we use the 

term climate habitat to indicate areas that are expected 

to be suitable in the future based on the climate of the 

current species distribution. Species distribution 

models (SDM) are used to map these potential range 

shifts. 

A number of studies have analyzed impacts of 

projected climate change on forest type (Bachelet et al. 

2001) and the distribution of individual tree species 

(Hamann and Wang 2006, Littell et al. 2009, Coops 

and Waring, in press, McKinney et al. 2007, Shafer et 

al. 2001, Thompson et al. 1998, Zolbred and Peterson 

1999). However, some of these studies included only a 

small number of species or predicted changes in 

growth rather than in potential range extent. We 

selected two SDMs that analyzed most of the tree 

species in Group 1. Both these climate envelope 

models (CEM; also called statistical species 

distribution models) predict changes in climate habitat 

or in climatic conditions that presently are required by 

the species. It is easy to lapse into considering that 

these projections are predictions of species’ future 

distributions (for example, “This species will 

disappear by 2100.”), but this type of conclusion is 

beyond the power and scope of the models. The two 

SDMs selected were:

1. Tree Climate Viability Maps (TCVM) (Rehfeldt et 

al. 2006, Rehfeldt et al. 2009). For each species, 

current and predicted future distributions (years 2030, 

2060, and 2090) are mapped using climate projections 

from one of three global climate models (GCM) 

(CGCM3 from the Canadian Climate Center, 

GFDLCM21 from Geophysical Fluid Dynamics 

Laboratory, or HADCM3 from the Hadley Center) and 

anthropogenic emission levels A1B (intermediate), A2 

(hot and dry), and B1 (cooler and wetter) (fig. E-1). 

See Mote et al. (2008) for background information on 

GCMs and emission levels. On each map, the 

predicted range is displayed as two probability classes: 

0.5 to 0.75 and 0.75 to 1.00 (Crookston et al. 2010). 

To facilitate our analysis, we combined probability 

classes equal to or greater than 0.5 and produced maps 

simply showing presence (≥0.5) and absence (<0.5). 

TCVMs are available for all Group 1 tree species in 

this assessment except black cottonwood.

2. Multivariate Spatio-Temporal Clustering 

(MSTC) (Hargrove and Hoffman 2005, Hoffman et al. 

2005). For each species, current and future species 

distribution for 2050 and 2100 were mapped, using 

one of two GCMs (one from the Hadley Center or 

from NCAR, PCM) and anthropogenic emission levels 

A1 (warmer) and B1 (fig. E-2). Maps are available for 

all Group 1 species in this assessment.
Climate Change and Forest Biodiversity in Western Washington E-3

3

Douglas-fir

 

 MSTC Current MSTC 2050, Hadley A1

Figure E-1. Climate habitat projection for Douglas-fir, current and for the year 2050, based on the Multivariate 

Spatio-Temporal Clustering (MSTC) model (Hargrove et al. 2010, Hoffman et al. 2005), 

http://www.geobabble.org/~hnw/global/treeranges/climate_change/index.html. Blue line represents 

present distribution based on Little (1971); red solid color indicates projected species distribution.

Douglas-fir

 TCVM Current TCVM 2060, Hadley A2

Figure E-2. Climate habitat projection for Douglas-fir, current and the year 2060, based on the Tree Climate 

Viability Map (TCVM) model (Rehfeldt et al. 2006, Rehfeldt et al. 2009), 

http://forest.moscowfsl.wsu.edu/climate/species/index.php. The projected range is displayed as two 

probability classes: 0.5 to 0.75 (both shades of green) and 0.75 to 1.00 (red) (Crookston et al. 2010). The 

blue line represents present distribution based on Little (1971).
E-4 Climate Change and Forest Biodiversity in Western Washington

4

Both these SDMs use CEM to predict future suitable 

habitat based on climate variables. There are 

limitations to the usefulness of CEMs, and some have 

expressed concerns about their application (Davis et 

al. 1998, Pearson and Dawson 2003, Robinson et al. 

2008). For example, spatial data produced by these 

models should only be interpreted in a very broad 

sense. In this case, we planned to use the SDMs to 

gauge vulnerability, not to pinpoint habitat changes on 

any particular site. But such concerns did influence our 

development of the scoring system for this risk factor. 

One scoring approach that we examined was ranking 

species based on the change in cover between current 

and predicted future distributions. The percentage 

change in cover has been used in at least one SDM 

(Thompson et al. 1998). But after considering the 

assumptions and uncertainties of these models, we did 

not feel that extracting numeric values representing 

distribution was appropriate. Furthermore, an overall 

change in percentage cover could mask spatial 

heterogeneity including increases in certain areas and 

decreases in others. For these reasons, we took a more 

conservative approach and decided to visually assess 

the change in distribution and then assign categorical 

values based on increases or decreases.

Selection of climate habitat 

projections

The combination of emission levels, target future year, 

and GCMs produced a large number of maps for each

species. To determine if the analysis could be 

simplified, we compared the maps for both TCVM and 

MSCT across GCMs and anthropogenic emission 

levels for Douglas-fir and subalpine fir (figs. E-3 and 

E-4). We found that changes in anthropogenic 

emission levels resulted in small changes in climate 

habitat projections but not in the overall trend. The 

higher emission levels produced the greatest relative 

change and provided the most extreme outcome; 

therefore, we choose these for our analysis: A2 for 

TCMV and A1 for MSTC. It would have been ideal to 

have the same emission scenario for both SDMs, but 

that the two research groups did not use the same 

scenarios.

We compared the TCMV model results for 2030 and 

2060. As with emission levels, different target years 

produced slight differences in species distribution, but 

these differences do not change the scoring results. 

Uncertainty can only increase with time to the target 

year, so TCMV 2090 and MSTC 2100 were not 

considered. Because it was desirable to use as close a 

target year as possible for the two SDM approaches, 

we selected 2060 for TCMV and 2050 for MSTC.

Comparison of the results using different GCMs 

revealed only slight changes in predicted suitable 

habitat. Therefore we limited our analysis to the 

Hadley GCM projections because they were used in 

both SDMs.

In some cases, the models were poor predictors of 

current distribution, consistently producing a more 

extensive range than observed. For example, the 

current range of noble fir was projected to extend into 

the northern Cascades and onto the Olympic Peninsula 

beyond its present distribution, as outlined in blue on 

fig. E-5. This issue has been recognized (Rehfeldt et 

al. 2006) and will be the subject of refinements in the 

future (Hargrove, pers. comm.). For this assessment, 

scores were based on comparisons only in areas where 

the species was known to occur.
Climate Change and Forest Biodiversity in Western Washington E-5

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E-6 Climate Change and Forest Biodiversity in Western Washington

6
Climate Change and Forest Biodiversity in Western Washington E-7

7

SCORING AND RESULTS

We visually scored the projected change in tree 

species climate habitat in western Washington by 

comparing current to future maps for the Hadley GCM 

under two species distribution models, TCVM (A2, 

year 2060) and MSTC (A1, year 2050) (table E-1). 

Projections often differed between the Olympic 

Peninsula and the Cascade Range and Puget Sound 

Area. For this reason we scored the two areas 

separately. For each species, model (MSTV or 

TCMV), and area combination, the projected change 

was scored as follows:

• No change in projected habitat (NC)

• Small decrease in projected habitat, no 

reduction in projected species range (–)

• Medium decrease in projected habitat, no 

reduction in projected species range (– –)

• Large decrease in projected habitat and a 

reduction in projected species range (– – –).

Figure E-5. Current and future predicted distribution (red color) of noble fir in western Washington based on 

two species distribution models (MSTC1 and TCVM2

) for the Hadley General Climate Model and A1 and A2 

emission levels, respectively. Blue line on MSTC maps represents present distribution based on Little 

(1971). 

1 URL for MSTC species distribution maps: 

http://www.geobabble.org/~hnw/global/treeranges/climate_change/index.html

2 URL for TCVM species distribution maps: http://forest.moscowfsl.wsu.edu/climate/species/index.php
E-8 Climate Change and Forest Biodiversity in Western Washington

8

Suitable climate habitat decreased for most species 

when considering their range across western 

Washington, but the magnitude of the decrease varied. 

A number of species showed no change at all. 

Predictions also varied by SDM. Although both 

modeling approaches predicted no change in suitable 

habitat for more species on the Olympic Peninsula 

than for the rest of western Washington, under TCMV 

more species were predicted to have a either a 

decrease in habitat or a complete loss of habitat in a 

portion of the range. The overall score used in the 

index was based on the area (Olympic Peninsula 

compared to Cascade Range and Puget Sound) with 

the greatest decrease in suitable habitat.

The species with the greatest predicted decreases in 

suitable habitat were noble fir, Alaska yellow-cedar, 

western hemlock, and mountain hemlock. The species 

with the least decrease in habitat were Douglas-fir, 

three fir species (Pacific silver fir, grand fir, and 

subalpine fir), bigleaf maple, and black cottonwood.

DISCUSSION

As stated earlier, we decided to eliminate the climate 

pressure risk factor from the vulnerability assessment 

based on peer review and an in-depth evaluation of the 

components and assumptions of the analysis. The 

challenges, limitations, and levels of uncertainty in the 

application of the two SDMs in the vulnerability 

assessment are outlined below. These elements 

produced a wide range of possible future scenarios, 

resulting in a level of uncertainty that was not 

compatible with our approach to the vulnerability 

assessment.

Climate envelope models are one type of model used 

to predict potential distribution of vegetation (See 

Halofsky et al. 2011 for summary). The climate habitat 

of individual species is projected based on statistical 

models with basic climate information as input 

(Robinson 2008). Limitations of CEMs include:

• Projections are based on current relationship 

between species in their realized niche and 

climate and cannot account for the 

opportunities brought about by future novel 

climate.

• These models do not account for competition, 

dispersal, local adaptation, or phenotypic 

plasticity, and they assume that the primary 

determinant of a species distribution is 

climate. Biotic interactions as new species 

assemblages develop may bring opportunities 

as well as challenges for species survival.

• CEMs cannot account for potential future 

changes in disturbance regimes, which are 

powerful drivers of current species distribution 

and can punctuate the trajectory between 

today and 2060.

• CEMs cannot account for the fact that plants 

respond to climate change individually 

(adaptation, acclimation dependent on genetic 

diversity) and that composition of vegetation 

assemblages will change as the climate 

changes as it has in the past (Leopold et al. 

1982).

Of the more than 20 general circulation models 

(GCM) available for the climate information used in 

SDMs, only a few were used in the MSTC and TCVM 

models. We did not find much variation in the climate 

habitat projections across GCMs, but if the full range 

of models had been used, greater variation in predicted 

future change would be expected (Bachelet 2010a).

Climate input data from western Washington that was 

used in the CEM is another source of uncertainty. The 

maps for each tree species appear definitive, but 

confidence in the results must be based on the 

evaluation of number of aspects of climate and 

geography, which would be very difficult to quantify. 

At a recent workshop, Dominique Bachelet, 

Conservation Biology Institute, listed uncertainty 

criteria as a series of questions:

• How many meteorological stations are close 

to your site and have been used to create the 

climate information used by SDMs? How long 

are the records from the meteorological 
Climate Change and Forest Biodiversity in Western Washington E-9

9

Table E-1. Climate change vulnerability assessment for 15 major western Washington tree species, based on 

two species distribution models, MSTC and TCMV, projecting changes in each species’ suitable habitat in 

the years 2050 and 2060, respectively

MSTV Model 

(2050 projection)

TCMV Model 

(2060 projection) Score

Species

Olympic 

Peninsula

Cascades 

and Puget 

Sound

Olympic 

Peninsula

Cascades 

and Puget 

Sound

Overall change in 

western Washington 

(both models)

Scaled 

index2

Abies procera 

Noble fir

no data1 (− −) no data (− − −) (− − −) 100

Cupressus 

nootkatensis 

Alaska yellowcedar

(− −) (− −) (− − −) (− − −) (− − −) 100

Tsuga heterophylla 

Western hemlock

NC (− −) (− − −) (− −) (− − −) 100

Tsuga mertensiana 

Mountain hemlock

(− −) (− −) (− − −) (− − −) (− − −) 100

Alnus rubra 

Red alder

NC (−) (− −) (− −) (− −) 50

Picea engelmannii 

Engelmann 

spruce

NC (− −) NC (− −) (− −) 50

Picea sitchensis 

Sitka spruce

NC NC (− − −) (− − −) (− −) 50

Pinus monticola 

Western white 

pine

(−) (− −) (−) (− −) (− −) 50

Thuja plicata 

Western redcedar

NC (− −) (−) (− −) (− −) 50

Abies amabilis 

Pacific silver fir

NC (−) (−) NC (−) 0

Abies grandis 

Grand fir

(−) (−) NC (−) (−) 0

Abies lasiocarpa 

Subalpine fir

(−) (−) (−) (−) (−) 0

Acer macrophyllum 

Bigleaf maple

NC (−) NC (−) (−) 0

Populus balsamifera

ssp. trichocarpa 

Black cottonwood

NC (−) no data no data (−) 0

Pseudotsuga 

menziesii 

Douglas-fir

NC (−) NC (− −) (−) 0

1 NC indicates no change in projected habitat; (–) indicates a small decrease in projected habitat, no reduction in predicted species 

range; (– –) indicates a medium decrease in projected habitat, no reduction in projected species range; (– – –) indicates a large 

decrease in projected habitat and a reduction in projected species range.

 
E-10 Climate Change and Forest Biodiversity in Western Washington

10

stations near your site and how much infilling 

has occurred in the meteorological station 

records used to create the SDM climate 

inputs?

• How complex is the terrain at your site? 

Complex topography generates a local 

decoupling of local climate that will not be 

affected by changes in regional climate as 

simulated by coarse-scale GCMs.

• How far from a relief feature (mountain range 

- shadow or deep valley - inversion) is your 

site?

• How far away is your site from a water body? 

Proximity to the coast will affect local climate 

processes. Fog conditions may change for 

example and allow for greater moisture than 

projected by GCMs.

• How much is your site affected by humans? 

o How far is your site from urban areas? 

(urban heat island effect from the 

greater Seattle area)

o Are there management impacts on 

vegetation structure or changes to 

stand composition due to harvest 

practices?

• How stable is the climate at your site? The 

Pacific Northwest has large seasonal 

variability with warm dry summers and cool 

wet winters and local species are already 

adapted to wide seasonal swings in 

temperatures and moisture levels. 

o How much change will affect 

organisms already adapted to such 

swings in weather patterns?

o What are the thresholds or tipping 

points that may affect survival? 

Many of these questions are meant to be addressed at 

the stand level; we would need to understand these 

complex processes across national forests to begin to 

understand the climate variability and the usefulness of 

the model results.

There also were challenges in applying the projections 

of the two different SDMs used in the risk factor. In 

order to create one score for each species, we 

combined the results of the two models. This was 

problematic because the changes in projected climate 

habitat varied by model or by model and area (i.e., 

Olympic Peninsula compared to Cascades and Puget 

Sound) for a number of species. This trend has been 

found in other studies (Hijmans and Graham 2006, 

Pearson 2006).

To summarize the challenges of the use of SDMs in 

the vulnerability assessment:

• The level of uncertainty for species envelope 

model results is high.

• Model uncertainty can come from a number of 

different sources, which are difficult to 

quantify but essential to evaluate SDM results. 

• This uncertainty is inconsistent with the 

variables in the other risk factors of the 

vulnerability assessment, most of which are 

not open to interpretation because they are 

based on known life history traits and current 

distribution.

• Projected future climate habitat maps varied 

by model (MSTV compared to TCMV; table 

E-1).

• Projected future climate habitat maps varied 

by area within the region (Olympic Peninsula 

compared to Cascade Range and Puget Sound; 

table E-1).

• Combining results across models and areas to 

produce a score for each species masks these 

differences.

• Absence of a climate pressure factor in the 

vulnerability assessment does not preclude the 

use of model projections in vegetation 

management.

• Models will continue to improve; this is an 

additional reason to evaluate their usefulness 

outside of vulnerability assessment.
Climate Change and Forest Biodiversity in Western Washington E-11

11

• There is a need for using an ensemble of 

climate projections (particularly regional 

climate models that give better local 

information) and multiple model approaches 

to test various hypotheses about species 

adaptability (beyond the scope of a simple 

assessment).

1
2

United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

April 2011

CLIMATE 

CHANGE AND 

FOREST 

BIODIVERSITY:

A VULNERABILITY 

ASSESSMENT AND 

ACTION PLAN FOR 

NATIONAL FORESTS 

IN WESTERN 

WASHINGTON