Synthesis activities of the
Western Mountain Initiative
• Don McKenzie
• Nate Stephenson
• Dave Peterson
• Jill Baron
• Craig Allen
• Dan Fagre
and the younger cohort
• Lindsey Christensen
– Postdoctoral reearch associate, Colorado State
University
• Jeff Hicke
– Faculty, University of Idaho
• Jeremy Littell
– Postdoctoral reearch associate, University of
Washington
• Phil van Mantgem
– Ecologist, USGS Sierra Nevada
WMI Project Organization
Products and
Management Implications
Cross-site Interpretations
Discharge, Water Quality, Aquatic response
Snow, Treeline, Productivity, Fire,
Forest Dieback
Books, Specialized and Synthetic Papers,
Datasets, Models, Website, Graduate
degrees, Presentations to managers and
scientific meetings
Remote Sensing
Statistical Analyses
Modeling Synthesis
Workshops
Regional Synthesis
Fire-climate Relationships, Forest Dynamics,
Climate Variability, Snow and Glaciers
Northern Rockies
Pacific NW
we are here
Site Specific Studies
Monitoring
Paleostudies
Modeling
Sierra
Nevada
Disturbance
Vegetation dynamics
Hydrologic processes
Central Rockies
Southern Rockies
WMI synthesis
(West-wide)
Fire-climate interactions
Wildfire & regional air quality
Fire-BGC simulations (2)
Insect outbreak dynamics
Disturbance interactions &
Paleofire-climate workshops
Disturbance
Vegetation dynamics
Hydrologic processes
Climate & growth in Douglas-fir
Treeline dynamics workshop
Demography, productivity, mortality
RhesSys simulations (2)
Broad-scale NPP
RhesSys simulations (2)
Regional glacier mapping
(2) = cross-site interpretations
Hypotheses (sneak preview)
• Increasing moisture limits on productivity will alter
(tree) species composition by
–
–
–
–
locally favoring more xeric species.
exacerbating episodes of vegetation dieback.
altering mortality and turnover rates.
Underlying ecological mechanism = large-scale shift to a
negative water balance.
• Disturbance will be the principal agent of ecosystem
change
– late 20th-century trends such as increasing insect mortality
or fire area burned may be replaced by more abrupt
changes.
– underlying mechanisms here are complex, operate at
multiple scales, and may be constrained by physical limits.
Themes
• Empirical studies
of climate, growth,
& productivity
• Disturbance will be
the principal agent
of ecosystem
change
• Watershed modeling
of vegetation &
hydrology
Climate dimensions of the sample transect
The magnitude of the correlation between seasonal
hydrological variables and tree-growth depends on the position
of the plot along a gradient of surplus water in the
environment.
Themes
• Empirical studies of
climate, growth, &
productivity
• Disturbance will be
the principal agent
of ecosystem
change
• Watershed modeling
of vegetation &
hydrology
Projected increases in area burned -- Montana (McKenzie et al. 2004)
Northern Ecosystems
Eco-provinces with similar climate correlations
• More annual precip →
less area burned.
• Higher summer and
growing-season
temperature → more
area burned.
• Current climate is
important.
• Previous years’ climate
has less influence.
Littell et al. (2006)
Arid/Semi-arid Ecosystem Pattern
•
Four ecoprovinces with
semi-arid vegetation
types
•
Very strong, positive
lagged relationships
with PPT / PDSI, esp.
winter
•
Weaker - Summer / GS
PPT or PDSI
Littell et al. (2006)
Climate-limited or fuel-limited?
• Different fuel types respond
differently to climate.
• Two mechanisms: drying of
fuels and production of fuels.
• Drying happens seasonally,
whereas production affects
fire on scales from years to
decades.
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
But threshold behavior is complex
For example
If insect population cycles
are not synchronized with
seasons, outbreaks are not
likely.
Mountain pine beetle
Pinus contorta (lodgepole pine)
Hicke et al., J. Geophys. Res.-Biogeosciences, 2006
Hicke et al., J. Geophys. Res.-Biogeosciences, 2006
Increasing T leads to…
2. Initial
increase in
adaptive
seasonality at
highest
elevations
1. Decrease
in adaptive
seasonality at
lowest
elevations
∆T = 5°
Hicke et al., J. Geophys. Res.-Biogeosciences, 2006
MPB outbreaks in high-elevation whitebark pine
Railroad Ridge, ID Today
Photo by J. Logan
July 2005, Railroad Ridge, ID
Quickbird Satellite Imagery
Themes
• Empirical studies of
climate, growth, &
productivity
• Disturbance will be the
principal agent of
ecosystem change
• Watershed modeling
of vegetation &
hydrology
Climate time series
GIS
Inputs
DEM
Initial states
Meteorological
Processes
Canopy
Processes
Soils
Veg
Hydrologic
Processes
Drain
LAI
Baseline runs
Sensitivities
Cross-site comparisons
Future climate experiments
Cross-site comparisons
West-wide patterns,
gradients, and interpretations
Daily streamflow
Norm alized Streamflow
(mm per day)
•
•
•
•
•
•
90
80
70
60
50
40
30
20
10
0
10
11
12
1
Modeled
2
3
4
Month
5
6
7
8
Observed
9
Stehekin River
Lake McDonald
RhesSys watersheds
Merced River
undecided
Snake River
Transpiration: sensitivity to snowpack at middle elevations
400
600
1200-1800 m
800
1000
1200
1850-2150 m
1000
Merced
River
800
Energy limited
Transpiration (mm)
Water limited
600
400
200
0
2200-2550 m
2600-3900 m
1000
800
600
Energy limited
Water limited
400
200
0
400
600
800
1000
1200
Peak snow depth (mm)
Christensen et al. in prep
Hypotheses (WMI synthesis)
• Increasing moisture limits on productivity will
alter (tree) species composition by
–
–
–
–
locally favoring more xeric species.
exacerbating episodes of vegetation dieback.
altering mortality and turnover rates.
Underlying ecological mechanism = large-scale shift to a
negative water balance.
• Disturbance will be the principal agent of ecosystem
change
– late 20th-century trends such as increasing insect mortality
or fire area burned may be replaced by more abrupt
changes.
– underlying mechanisms here are complex, operate at
multiple scales, and may be constrained by physical limits.
Changing relationship over time between precipitation and growth
Precipitation coefficient
Long-term trend (due to gradual warming)
0
Energy-limited?
High variability, sensitive
to e.g., excessive snowpack
Decoupling
Water-limited?
Time
Very sensitive to
e.g., drought
Recoupling
Jemez Mts., May 2004
Hypotheses (WMI synthesis)
• Increasing moisture limits on productivity will alter
(tree) species composition by
–
–
–
–
locally favoring more xeric species.
exacerbating episodes of vegetation dieback.
altering mortality and turnover rates.
Underlying ecological mechanism = large-scale shift to a
negative water balance.
• Disturbance will be the principal agent of
ecosystem change
– late 20th-century trends such as increasing insect mortality
or fire area burned may be replaced by more abrupt
changes.
– underlying mechanisms here are complex, operate at
multiple scales, and may be constrained by physical limits.
Fire
Disturbance
synergy
Climate
Vegetation
Disturbance drives
ecosystem changes
25-100 yr
Climatic
change
100-500 yr
Habitat changes
Broad-scale homogeneity
Truncated succession
Loss of forest cover
Loss of refugia
Fire-adapted species
New fire regimes
More frequent fire
More extreme events
Greater area burned
Species responses
Fire-sensitive species
Annuals & weedy species
Specialists with restricted ranges
Biggest challenge: integrating across scales
Scale mismatch between
drivers and responses
Multiple stochastic elements
with no equilibrium
Neilson, Lenihan, Bachelet, et al.
Stands
?
Landscapes
?
Continents
Thanks!