Good Ozone Depletion
1970’s Researchers discover “hole” in Stratospheric ozone which blocks UV rays
1980’s CFC’s identified as cause of thinning
1989 Montreal Protocol world wide treaty banning use of CFC’s
It takes decades for CFC’s to dissipate, but the thinning has slowed
Free-Air CO2 Enrichment Experiments (FACE)
Open-air control of atmosphere conditions
Fairly large scale
Longer term than previous chamber experiments
Major investment of research money
Large teams of researchers
1 treatment per ring4 treatments x 3 blocks = 12 rings
ElevatedCO2
ElevatedO3
ElevatedCO2 + O3
AmbientControl
ppm CO2:ppb O3:
36032
56032
36056
56056
Experimental Design
CO2 and Ozone Effects on Trees
CO2 effects:+ photosynthesis+ growth+ water use efficiency– wood density
O3 effects:– photosynthesis– growth– wax cuticle of leaves+ leaf senescence
Large starch grains
Normal aspen chloroplast
Intact thylakoid membranes
Ozone damaged chloroplast
Disintegration of thylakoid membrane
Membrane degradation material
Small starch grains
Cell-level Ozone Damage
0
2000
4000
6000
8000
Aspen Aspen-Birch
Aspen-Maple
Cu
mu
lati
ve
Ne
t P
rim
ary
Pro
du
cti
vit
yg
m-2
Stems & Branches
Fine Roots Coarse Roots
Foliage
Co
ntr
ol
CO
2
O3
CO
2 +
O3
Co
ntr
ol
CO
2
O3
CO
2 +
O3
Co
ntr
ol
CO
2
O3
CO
2 +
O3
a
c aa
a a
b b
b
aa
ab
CO2 and O3 Effects on Tree Growth
• Tree growth increases under elevated CO2 and
decreases under O3 in Aspen (not Birch)
• Carbon sequestration under elevated CO2 is
overestimated in models which do not consider
O3 impacts
• O3 damage to protective coating of leaves
(cuticular wax) reduces resistance to insects
(e.g., leaf miner)
• CO2 reduces the damaging effects of O3, but O3
counteracts growth stimulation by CO2
Research Findings I
• Cycling of C and N increases under elevated
CO2, but effects differ among FACE sites
• O3 counteracts most CO2-induced
enhancements in ecosystem processes (soil
respiration, N availability…)
• Elevated CO2 delays normal autumn leaf
senescence, predisposing some trees to winter
dieback
• Aspen and birch insects and diseases increase
under elevated CO2 and O3
– Cascading responses, trophic interactions
Research Findings II
Ozone affects plant & human health
“sunburns” lungs breathing difficulties
during exercise permanent lung damage
after repeated exposure
Photosynthesis Leaf size Leaf longevity Fine root biomass
Trophosphericozone &
Nitrogen cycle
Increased production of N pollutants
SMOGSMOG
Global change interactions
• Increase production of greenhouse gases: nitric & nitrous oxide
• Eutrophication: ground water, streams, lakes, ocean
• Dead Zone (50 areas worldwide, including the Gulf of Mexico)
Hypoxic zone in the Gulf of Mexico is the
size of NJ.
Consequences of doubling Nitrogen fixation
How can you reduce bad ozone
•Choose a cleaner commute — car pool, use public transportation, bike or walk when possible. •Combine errands to reduce "cold starts" of your car and avoid extended idling.•Be sure your tires are properly inflated.•Keep car, boat and other engines properly tuned, and avoid engines that smoke. •Follow gasoline refueling instructions for efficient vapor recovery. Be careful not to spill fuel and always tighten your gas cap securely