Ecosystem Function and Health Program

Problem Area:• Quantify and predict ecosystem responses to

environmental stressors (e.g. climate change).

• Develop statistical models to help managers make informed and defensible predictions.

Haiganoush K PreislerStatistical Scientist

PSW Research Station𝑑𝑁 (𝑡 )= {𝛽 (𝑢) 𝑁 (𝑡 )−𝜀𝑁

(𝑡 )+𝐴 (𝑡 )−𝛿𝑁(𝑡 ) }+𝑑𝑉

Understanding the influence of climate on1. mountain pine beetle outbreaks in:

• Lodgepole pine forests• Whitebark pine forests

2. wildland fire occurrence and size.

How does climate influence beetle outbreaks?

Outbreaks

Beetle pressure

Remaining live trees

Drought stress

Adaptive seasonality

Winter mortalityProbability of an outbreak

Outbreak severity

USFS aerial detection surveys

A mechanistic statistical model

Y = 1 if Stress on tree > Tree toleranceY = 0 otherwise

Stress = number of attacking beetles ~ g1(birth rate) + g2(btp) + g3(live trees)

S = f1( temp, drought) + f2(btp) + f3 (live trees)

T = f4 (drought) f ( ) ~ smooth functions to be

estimated from data

Winter Mortality Adaptive Seasonality

Drought Stress

Study location (LPP study)

Washington

Oregon

Contribution of beetle pressure vs. weather

weather important during initiation, collapse

beetle pressure most important

Influence of Climate on Wildland Fire Occurrence and Size

Climate Variable – Fire Weather Index (FWI)

Other Variables – Distance to road; Forest vs Ag land

Predicted Probability of a large fire per 10km2

11

Westerling et al 2011 Climatic Change

Westerling et al 2011 Climatic Change