Effects of a Warmer Climate on
Stress Complexes in Forests of
Western North America
Don McKenzie, David L. Peterson, Jeremy Littell
USDA Forest Service, Pacific Northwest Research Station
AND
University of Washington
1.0
Model 1: the environmental “niche space”
0.6
0.4
TSME
PIAL
PICO
Lots of interesting science
where the slopes are steep
0.2
0.0
Probability of occurrence
0.8
A small change yields
a big shift in dominance
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20
40
60
80
Mean winter precipitation
100
|
120
McKenzie et al. 2003
Model 2:
The Disease
Spiral
From Manion (1991)
A pathological model is applicable
to forest ecosystems
Warmer climate
Soil moisture stress (+)
Growth and vigor (-)
Drought and warmer temperatures affect
conifer forests in western North America
Pinyon-juniper (Southwest)
Mixed conifer (California)
Ponderosa pine – mixed conifer
(interior West)
Lodgepole pine (interior West)
Pinyon-juniper (American Southwest)
Extended warm period, insects, pines
die, junipers survive, fuels accumulate,
large fires. But this has probably
happened before?
PINYON mortality associated with Pinyon Ips beetles (Ips confusus).
Jemez Mts., March 2004
Dying Pinus edulis
Jemez Mts., October 2002
“Pinyon-juniper, hold the pinyon!”
Jemez Mts., May 2004
Mixed conifer
(Sierra Nevada,
southern California)
Ozone pollution
Fire exclusion Æ high stand densities
Extended warm period Æ insects
Ponderosa pine, Jeffrey pine, white fir die
Fuels accumulate Æ severe fires
Exotic plants increase where fires do occur.
Ponderosa pine – mixed conifer
Fire exclusion Æ high stand densities,
extended warm period, insects, pines die,
fuels accumulate, sets up for large fires.
Lodgepole pine
Extended warm period, insects, pines die,
fuels accumulate, sets up for large fires.
Much of this area is being salvage logged.
Spruce forest (S. Alaska)
Extended warm period, insects,
spruce die, fuels accumulate, large
fires, species conversion?
Yellow cedar (SE Alaska)
Extended warm period, insects,
yellow cedar stressed or die.
Stand replacing fire +
global warming
Black spruce
Ecosystem change
Paper birch
Stand replacing insect
kill + global warming
White spruce
High altitudes
Whitebark pine
Exotic pathogen
Bristlecone pine
Insects (new)
Subalpine forests
Increased growth,
increased
regeneration,
krummholz Æ upright
What are desired future conditions
in a changing climate?
From McKenzie et al. (2004), Conservation Biology 18:890-902
Rapid climatic change will send ecosystems
across disturbance thresholds
For example
Drastic increase in
fire severity
Doubling of insect
reproductive cycles
Mountain pine beetle
Pandora moth
Climatic change doubles fire area in Oregon
Precipitation (%)
from
1916-2002
average
Temperature (oC)
From McKenzie et al. (2004), Conservation Biology 18:890-902
Adapting to a Warmer Climate –
Some Recommendations
Use nursery stock tolerant to low soil moisture, high
temperature
Use a variety of genotypes in nursery stock
Consider planting mixed-species stands
Retain woody debris on site to moderate temperature
Probably no historical or current analogue
to optimal conditions for forest
resilience Æ use adaptive management.
Thanks!
Discussion?
Don McKenzie
donaldmckenzie@fs.fed.us
206.732.7824
http://www.fs.fed.us/pnw/fera