Transcript Review of the Angiosperms

Earth’s carbon balance
The Basic Principle
2
CO2 is a “greenhouse” gas – it absorbs infra-red radiation as heat
There are other greenhouse gasses, such as CH4 and
NO2 but CO2 is the major one
How is CO2 measured?
Infra red gas analyzers
NOAA monitoring
System on Mauna Loa
System for measuring
leaf photosynthesis
CO2 absorbs infra red radiation
A test gas sample is compared with a reference gas
World network
NOAA Stations
Mauna Loa
US Somoa
South Pole
Mauna Loa CO2
International
Geophysical
Year
Trend and annual cycle
Northern hemisphere effect
March-May maximum
South pole out of phase
Global growth rate in atmospheric CO2
Influence of
economic
downturns
can be seen
Changes in mean annual global temperature
Sea level rise
Potential effects of sea level rise
Estimates of sea
level rise range
between 20 and
110 cm by 2100
Why climate change effects on oceans may pose a serious threat
Hurricane George hits Key West
http://news.bbc.co.uk/hi/english/sci/tech/newsid_679000/679959.stm
‘In what is being
described as "a
groundbreaking move for
local government",
politicians in the Florida
Keys have recognised that
climate change is likely to
threaten their reefs and
beaches with severe
damage.’
Why climate change effects on sea level poses a serious threat:
Small increases in mean sea level may have large effects during
storm conditions, e.g., Florida, Maldives, Bangladesh
Possible changes in ocean currents, e.g., the Gulf Stream and its
effects on Northern Europe – dramatic not incremental
Melting of the West Antarctic ice sheet not included in calculating
current estimates of sea level increase (potential ~5m rise).
Two Biological Questions
1. Could the earth’s biological systems
accumulate sufficient CO2 to balance `
emissions?
2. What effects may global change have on
the earth’s biological systems?
Summary of the earth’s current carbon balance
All figures are in billions
of tonnes of carbon, Gt C
1 tonne = 1,000 kilo grams
Anthropogenic release
+6.3
Net uptake by terrestrial vegetation
-0.7
Net uptake by the oceans
-2.3
Gain by the atmosphere
+3.3
1. Could the earth’s biological systems accumulate
sufficient CO2 to balance emissions?
Net uptake by terrestrial vegetation would have to be increased
four-fold to off-set the current rate of increase in
atmospheric C
Could any impact be made as part of a multiple solution
approach?
A more detailed look at the global carbon cycle, 1990s
Deforestation contributed between a third an a half
of the net gain in the atmosphere. If deforestation
were halted then the target for CO2 capture would
be less
There is four times as much carbon in the soils and
detritus of terrestrial ecosystems as there is in their
vegetation
There is approximately five times as much carbon
in accessible reserves as there is in the atmosphere
Carbonate in rocks contains the most C by far of
any compartment
Net primary production is the difference between
the amount of carbon gained by growth of plants
minus that lost by respiration and decomposition
Global carbon amounts & net primary production in different biomes
First
Second
tC/ha/yr
Some definitions …
Biome: all organisms, as well as the physical
environment, in a particular area. Biomes
are usually characterized by their plant life.
E.g., Tundra, tropical rainforest.
Biomass: the weight of living material.
SINKS: places where a material, or energy,
accumulates
SOURCES: places that produce or supply a material
or energy
Tropical forests have the highest biome net primary
production and the second highest total biomass.
They are strong SINKS for carbon – but if disturbed
so that their soil C is respired they can be strong
SOURCES
Although temperate forests have the second highest net
primary production they have a small global area and
so a low total biome C
Note that croplands have a low net primary
production. This is because crops usually do not cover
the ground for much of the year
Growth of young forests to absorb CO2
“Kyoto Forests”
To balance the net gain of 6 Gt of carbon by the
atmosphere through planting young forests, and,
assuming an increase in production of 5 t ha-1 over the
vegetation replaced, e.g., replacing a crop,
requires over 109 hectares of young forest, ~14 times
the size of Washington State.
Balancing the CO2 input from the US alone would
require an area ~3 times Washington State ( ~1.2 times
the size of California)
2. What effects may global change have on
the earth’s biological systems?
A. Direct effect of elevated CO2
B. Multiple effects of elevated CO2 , elevated
temperature, and changed nutrient inputs
C. Possible changes on the distribution range of
biomes and crops
A. Direct effect of elevated CO2
Net primary productivity is likely to rise but …
Enhancement declines as
the period of CO2
enrichment is extended
CO2 enrichment
experiments
Naturally CO2
enriched sites
Acclimation:
a
change in physiology
that enables a plant to
maintain a particular
pattern or rate of
growth, e.g., reduction
in stomatal density
FACE: Free Air Carbon Dioxide Enrichment
CO2 is released into the air
to achieve an elevated
concentration
Panama
Brookhaven National Lab
Experiments are being
conducted with a range of
crop and vegetation types
Catherine Potvin
B. Multiple effects of elevated CO2 , elevated
temperature, and changed nutrient inputs
Gain in uptake of carbon may be offset by an
enhanced respiration, especially microbial
respiration associated with decomposition in
the soil and organic litter
Anthropogenic nitrogen from automobile
exhausts and agriculture may cause an increase
in productivity
C. Possible changes on the distribution range of
biomes and crops
Use of global climate change models to
predict climate change, along with known
present day environmental conditions of
different biomes, leads to prediction of
major areas of change in vegetation types
and that the geographic range of crops will
change
Sitka
spruce:
expansion
as coastal
region
becomes
wetter
Sitka spruce
Simulated changes in species distributions
Douglas fir
Douglas fir:
some
contraction
and
expansion
No change
Contract Expand
Sitka spruce
Western red cedar
Western hemlock
Incense cedar
Lodgepole pine
Ponderosa pine
Simulated changes in species distributions
Engleman spruce
Douglas fir
No change
Contract Expand
Information about potential tree species change in the western US can be found at:
http://greenwood.cr.usgs.gov/pub/circulars/c1153/c1153_4.htm
1. Substantial changes in tree species distribution are
predicted.
2. The changes are individualistic – not the same for
all species.
3. Similar types and sizes of change have taken place
since the end of the last glaciation
4. Predictions of expansion DO NOT TAKE
ACCOUNT of trees dispersal requirements
5. Changes in tree distribution since the last
glaciation occurred over ~ 10 thousand years.
Conclusions
A “business as usual” approach to CO2
emissions will lead to a major increase in
atmospheric concentrations, doubling by
the end of the next century is quite
possible
Such a change is bound to have major
effects on the earth’s biological and
geophysical systems
Sections you need to have read
7.13 35.10 38.4
http://www.umac.org/climate/Papers/pg56-64.html
Courses that deal with this topic
There are many courses and seminars that cover
particular aspects of climate change. Two to consider are:
ESC 202 Global Changes and Forest Biology
ATM S 211 Climate and Climate Change