Interactive Effects of Air
Pollution and Climate Change
on Forests
Andrzej Bytnerowicz
US Forest Service, Pacific Southwest Research Station,
Riverside Fire Laboratory
Air pollution is an integral part of
climate change
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Many of traditional air pollutants and
greenhouse gases not only have
common sources, but may also interact
in the atmosphere causing a variety of
environmental impacts on local,
regional and global scales.
Problem - tropospheric ozone
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Although peak concentrations of ozone have
been drastically reduced, background O3
concentrations have been continuously
increasing since the 1880s
It is predicted that by 2050 about 50% of
global forests may be affected by potentially
phytotoxic ozone concentrations of >60 ppb
(Fowler et al, 1999)
CASTNET - Annual Mean O3 Concentrations (ppb) for 2002
Southern California ozone 2005 seasonal
average
Biomass burning can significantly increase
ambient O3 concentrations
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Ozone is produced by reactions of volatile
organic compounds (VOCs) and nitrogen
oxides (NOx), e.g., from wildland fires.
Resulting O3 concentrations depend on
distance from the fire, fuel N content,
temperature, solar radiation, wind
conditions, contribution of VOCs and NOx
from other sources, and many other factors.
Examples of contribution of biomass
burning to elevated O3 concentrations
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Elevated ambient O3 concentrations occur
down wind from biomass fires (S. Atlantic savanna fires in Brazil; SE Asia – forest fires
in Indonesia; Canada – local forest fires)
Contribution of biomass burning to the
global tropospheric O3 concentrations is
~10% (Trentman et al., 2003)
McNally fire caused increases of ambient O3 and
PM2.5 levels in Sierra Nevada, summer 2002
“Wildland Fires and Air Pollution”
Elsevier Series “Developments in
Environmental Science”, in press
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Editors: Andrzej Bytnerowicz, Michael
Arbaugh, Christian Andersen and Al Riebau
Section I - General Information and Emissions
Section II - Ambient Air Quality, Visibility and
Human Health – Regional Perspectives
Section III - Ecological Impacts of Forest Fires
and Air Pollution
Section IV - Management Issues
Section V - Concluding Section
Problem - nitrogen deposition
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Elevated concentrations of reactive nitrogenous
compounds (Nr) lead to the above-normal levels
of N deposition in forests and other ecosystems.
Chronic deposition of N may lead to N saturation
in forests and other ecosystems manifested in
many different ways (growth changes, species
composition shifts, increased emission of N2O and
NO, deteriorated water quality, etc.)
Alpine biota in a warmer, CO2- rich
World (Christian Körner, Institute of
Botany, University of Basel, Switzerland)
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Warming will directly affect trees, and thus
the high altitude tree limit
Warming will affect low structure vegetation
largely via snow cover duration
Elevated CO2 does not lead to higher
productivity in alpine vegetation
Nitrogen deposition, at rates close to the
current values, induces major transformation
of alpine vegetation
Scientific knowledge gaps
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While wet N deposition is well characterized,
contribution of dry N deposition (gaseous
NH3 and HNO3 & particulate matter) is
poorly understood
This is especially important for arid and
semi-arid ecosystems where up to 90% of N
may be deposited in a dry form (e.g.,
California and the Mediterranean area).
Interactive effects of air pollution and
climate change on ecosystems
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Generally, climate change can alter the effects of air
pollution, and vice versa, air pollution may modify
responses of ecosystems to specific climate change impacts.
Examples:
(1) impacts of O3 on plants can be modified by rising
temperatures (increased length of physiological activity &
extended effective O3 exposure)
(2) climate change effects on ecosystem vitality, soil
processes or species composition can be altered by
increased N or heavy metal deposition
Extreme events happen and
should be studied carefully!
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Catastrophic fires in southern California in 2003
and 2007 (a consequence of overstocking
caused by very effective fire prevention
program, long-lasting drought, chronic air
pollution exposures and bark beetle infestation)
Catastrophic wind-throw in the Slovak Tatra
Mountains in November 2004 (result of chronic
high N + S deposition, elevated O3
concentrations and climatic variability in Norway
spruce monocultures)
What research can be done?
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Experiments at different scales (branch,
seedling, mature tree) needed to better
understand mechanisms of the effects of single
factors or simple interactions
Long-term, large scale experiments such as the
FACE studies or gradient air pollution studies
(Wisconsin, San Bernardino Mountains) which
are essential for better understanding of
complex interactions between air pollution and
climate change
Experimental Approach: The Aspen FACE User Facility
Control
CO2+O3
O3
CO2
CO2
CO2+O3
Control
CO2+O3
O3
CO2
Full Factorial, 3 reps:
C, +CO2, +O3, +CO2+O3
CO2: 360 and 537 ppm
The Aspen FACE experiment
is examining the impacts of
interacting elevated
atmospheric CO2 and O3 on O3
northern forest ecosystem
structure and function.
O3: 38 and 51 ppb
Growing season (daytime)
fumigation from bud break
to leaf drop (1998-present)
Control
Impacts of Elevated CO2 and O3 on Volume Growth from
5 Aspen Clones in the Aspen FACE Experiment
16
25
Clone 216
Clone 42E
20
12
15
8
Stem volume index (dm3)
10
4
5
0
8
0
16
Clone 259
6
12
4
8
2
4
0
35
Clone 271
30
25
20
15
10
5
0
1997 1998 1999 2000 2001 2002 2003
Clone 8L
0
1997 1998 1999 2000 2001 2002 2003
Year
Control
+CO2
+O3
+CO2+O3
Year
From: Karnosky et al. 2005. Plant Cell Environ. 28:965-981.
IUFRO conference “Adaptation of Forests
and Forest Management to Climate
Change with Emphasis on Forest Health”
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Umea, Sweden August 25-28, 2008
Session “Integrated effects of climate
change, air pollution, pests and
pathogens on forest health – current
status and projections for future”
Effects of concurrent elevated CO2 and O3 on
leaf gas exchange characteristics
Nancy Grulke, Elena Paoletti, Bob Heath, Angela Nunn
USDA Forest Service, Riverside, CA
IPP CNR, Florence, Italy
Botany Department, UC Riverside, CA
Dept. of Ecology, Technical University of Munich, Freising, Germany
DUKE FACE site, loblolly pine
Holm oak at CO2 springs
CASIROZ site, European beech
Designed a new gas exchange system that concurrently measures H2O, O3, & CO2 flux
21X Data Logger
O2 TANK
TANKED AIR
Tair
O3 GENERATOR
EXHAUST
Tleaf
PAR
Vent, small
MFC
HUMIDIFIER
REF O3 MON
MFR
REF H20 & CO2 IRGA
3-25 sccm
FRIDGE
MFC
HOC leaf flux
6400 Licor
~320 sccm
Vent, small
SAMP O3 MON
MFR
SAMP H20 & CO2 IRGA
120 sccm
HC leaf flux
HC system:
H2O, CO2 flux
EXHAUST
(6400 Licor)
(Grulke, Paoletti, Heath 2006 Env Poll 146:640)
•Two innovations:
–Low flow (120 sscm), fast response (20 s) O3 monitor
–Cooled air prior to cuvette (reduces inaccuracies in gs
measurements inherent in in-cuvette peltier cooling systems
Examination of stomatal behavior with
concurrent O3 exposure:
(1) Does O3 exposure modify foliar
water use efficiency under ambient
and elevated CO2?
(2) Does O3 reduce stomatal
responsiveness to dynamic light
conditions under ambient or
elevated CO2?
Two species/ecosystems:
-Holm oak in natural CO2 springs +
moderately high O3 generated and
transported from Pisa, Italy
-Loblolly pine at the Duke FACE
site, elevated CO2 + short term
elevated O3
Conclusions
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Elevated O3 reduced water use efficiency under both ambient
and 1.5x CO2 due changes in both net photosynthesis and
stomatal conductance
Both elevated CO2 and O3 decreased stomatal responsiveness
to abrupt changes in light level
Current modeling efforts use steady state response curves to
parameterize, which overestimate C sequestration in natural
field conditions
Current modeling efforts use low to moderate levels of O3
exposure: global background O3 levels are very close to
exceeding moderate levels used. By 2020, we will exceed
current modeling predictive capabilities…
Potential impacts of climate change on
bird populations and habitats in
southern California
Principal Investigators:
Jenny Rechel, Ph.D
Shyh Chen, Ph.D
Forest Fire Laboratory
Riverside, CA
Background
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Study area: the San Jacinto Mountains,
San Bernardino National Forest
A ‘mountain island’ habitat
Elevation gradients (915 m to 2,652m)
Over 10 years of bird surveys and
associated vegetation data on 84 perm.
plots
Questions related to Climate
Change:
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What are the effects of climate change on
species ranges?
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Which species will most likely be affected
negatively or positively due to climate changes?
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Following climate change, there will be
elevational shifts in vegetation and what will the
consequences be for birds, especially those
relegated to the remnant patches of conifer
forests?
Thank you!!!