Effects of Climatic Variability and Change on Forest Resources: A

Scale-based Framework for Analysis

David L. PetersonUSDA Forest Service, PNW StationUW College of Forest Resources

UW Climate Impacts Group

Temperature varies over time

Forest vegetation varies over time

PDO affects tree growth Subalpine fir in the Cascade and Olympic Mountains

From Peterson et al. (2002)

1920 1930 1940 1950 1960 1970 1980 1990

Low elevation forest

Summer precipitationSummer temperaturePDSIPDO

Summer soil moisture

YEAR

PC

Va

lue

3

2

1

0

-1

-2

WINTSMTH

PC3HIGHS

PC3MIDS

PC3LOWS

PC2STEPS

PDO affects growth of semi-arid tree species

Ponderosa pine in the Cascade Range

Data from G. Ettl

1900 1920 1940 1960 1980 2000

Subalpine conifer regeneration

warm, cool,dry wet

Limiting factors in forest ecosystems

High-elevation forests• Duration of growing season at treeline• Summer soil moisture at lower and drier locations

Low-elevation forests• Summer soil moisture

Semi-arid forests• Summer soil moisture

How does climatic variability affect wildfire?

Years with fire area > 80,000 hectares

National Forest data, 1916-2002

Warm-phase PDO Cool-phase PDO

Idaho 14 7

Oregon 14 5

Washington 10 2

TOTAL 38 (73%) 14 (27%)

Climatology affects wildfire in the Pacific Northwest

Extreme wildfire years are forced at least in part by antecedent drought and summer blocking in the 500 hPa height field.

From Gedalof et al. (2004)

M ay

Septem ber

August

July

June

Climatic change effects

From McKenzie et al. (2004)

Temperature (oC)

Pre

cipit

ati

on

(%

)

Fire areaOregon1916-2002

Stress Interactions, Disturbance

Increased fire risk• Higher fire frequency• Higher fire intensity, esp. eastside where fuel hazard is high

Increased insect outbreaks, esp. eastside• Postfire stress• Low vigor stands with high stem density

Forest Carbon Budgets

Storage (quantity) vs. uptake (rate)

Young forest Storage Uptake Mg/ha

Mg/ha/yr

50-100 5-10

Old forest 400-1000+ + 1.0?

(600?)

  Local (small watershed)

Subregional (large watershed, national forest)

Regional

Paleoecology Low Moderate Low

Growth and productivity

High Moderate Moderate, depends on ecosystem

Carbon Moderate Low Low

Regeneration Moderate Low Low

Genetics Low Low Low

Disturbance ecology

High Moderate Moderate, mostly for fire

Scale-based framework: knowledge base

Management authority

Federal• Forest Service• Bureau of Land Management

State• WA Department of Natural Resources• OR Department of Forestry

Private• Industrial forest• Nonindustrial forest

Response capacity

FederalCarbon management (storage, LCA)Altered planting strategiesFire mitigation

StateCarbon management (storage)

PrivateIndustrial forest -- Genotype management -- Carbon management (storage, LCA)Nonindustrial forest -- None; default carbon storage?

THANK YOU!

David L. Petersonpeterson@fs.fed.us

206.732.7812http://www.fs.fed.us/pnw/fera