Transcript slides

Plants and Carbon
• Photosynthesis:
6CO2 + 6H2O + solar radiation
→
C6H12O6 + 6O2
sugars
• Respiration:
C6H12O6 + 6O2
sugars
→ 6CO2 + 6H2O + chemical energy
• Biomass:
GPP – Ra = NPP
GPP = gross primary production
NPP = net primary production
Ra = respiration
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Carbon
Air
Water
CO2
Limestone
Reduced sequestration:
Global forest biomass
reduction when
deforested (land use)
 Land Use
 Fossil fuel
utilization
Fossil
Fuels
Net addition of
Carbon in the
cycle from fossil
fuels
Land
Landfills only
partially
compensate
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Biomass Wastes
– in landfills
Soil Storage of Carbon–
COMPLEX CARBON
COMPOUNDS OR ORGANIC
MATTER
Decomposition Plant Tissues– COMPLEX
CARBON COMPOUNDS CONVERTED
TO CARBON GASES AND ORGANIC
MATTER
>100 years
10 – >100
years
Carbon Pools
and the Flux
Rates of
Carbon
Atmosphere –
CARBON
GASES
10 – >100 years
Plant Growth and
Biomass – FORM
COMPLEX
CARBON
COMPOUNDS
Seconds to
Minutes
Millions of years –
CARBON IN
BIOMASS TO OIL,
NATURAL GAS,
COAL
Wood Products – COMPLEX CARBON
COMPOUNDS STORED IN HUMAN
CONSTRUCTS
Minutes to
Days
FOSSIL
FUELS
50 -100 years
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Table 6.1. Estimates of the carbon pools in various global reservoirs.
(modified from Siegenthaler and Sarmiento 1993, Schimel et al. 1995, Sundquist 1993)
Global Pools of Carbon Amount of Carbon
(or Reservoirs)
(billion metric tons)
Atmospheric
Oceanic
Vegetation
Soils
Percentage of Total
(%)*
750
1.8
39,000
93.4
550
1.1
1,500
3.7
100.0
Recoverable Fossil Fuel
Geological Substrate
(marine sediments,
sedimentary rocks)
> 4,000
-
> 65,000,000
-
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Carbon in
the
World’s
Forests
and Soils
Forest C
Soil C
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Early
Soil Scientists!
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Soil Profile and Horizons
O
A
E
O
A
E
B
B
C
C
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Carbon in Soils
Deciduous
Forest Soil
Coniferous
Forest Soil
Tropical
Forest Soil
150 Mg C
320 Mg C
65 Mg C
Young Riparian
Forest Soil
30 Mg C
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Biosphere 2 in Arizona
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Biosphere 2
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• Tropical forest soils are generally acidic
– Native soil is alkaline, so add OM to soil
• Decomp of OM creates
organic & carbonic acids in soil
decreasing pH of soil
• However too much OM, so microbes
continue decomp, releasing CO2 and
using O2
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Problems
• CO2 increases to 2000 ppm but
levels off around 800-1500 ppm
• O2 decreases from 21% to 15%
and continued decreasing
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CO2 was absorbed by the artificial rock formations and concrete
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Carbon components of forest materials:
-simple sugars
-starch
-cellulose
-lignin
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Sugar
C6H12O6
Paper =
Cellulose
(remove lignins
and sugars)
C6H12O6 + C6H2O6 + C6H12O6 Cellulose
http://babylon.u-3mrs.fr:10085/~www-pol/cell.html
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CELLULOSE
Polymers from cellulose:
plastics, motion picture film, clear lacquer coating, rayon (fabrics)
http://www.psrc.usm.edu/macrog/proposal/dreyfus/outco
me/plascot/cellace.htm
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Chemical
composition of
jeans is same as
what the
MICROBES EAT
DURING
COMPOSTING
Jeans = equivalent
to paper, bags,
cardboard (some
lignin still left)
http://www.us.levi.com/spr03a/levi/home/l_home.jsp
Apply
sulfuric
acid –
what
happens
to jeans?
c
H2SO4
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LIGNIN
Six-carbon ring
structure (benzene)
– same structure as
pesticide
Makes plants woody
Very resistant to
decay
Complex enzymes
needed to break
down
http://www.eng.rpi.edu/dept/chem-eng/BiotechEnviron/FUNDAMNT/lignin.htm
Removed from wood
to make paper,
what is left after
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composting
What is composting doing to
plant materials?
What is the product left at the
end of composting?
What is its chemical
composition?
What is eaten up by microbes
in composting?
What is the chemical
similarity of
COMPOSTING to forest
materials that decompose?
http://www.gardenaction.co.uk/images/compost_bin_very_simple_mine.jpg
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Forests and recycling - today
- recycle paper
- construction wood – re-use untransformed
- wood wastes from making products
or from forest activities -- burn to
make steam and energy or
composted by mixing with animal
wastes
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Stored Carbon
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LIFE-CYCLE for FORESTS: United States
FORESTS
82% Forest Products:
paper, building materials, packing
materials, furniture, clothing
~18%
Fuelwood
16%
4) Burned
57%
27%
1) Landfill
In US, 38% of fiber in
paper is recycled fibers
2) Composting 3) Recycling
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Factors Increase C
sequestration:
• Land fills (-/+)
Carbon Cycle –managed to
• Wood Products
increase/decrease storage
• Afforestation
(plant more trees)
• Decrease C loss in
agricultural soils and in
forests when not cut trees
Factors Reduce C
sequestration:
• Land-use changes
(Deforestation)
• Combust Fossil fuels
• Forest fires
http://www.marietta.edu/~biol/102/ecosystem.html#CarbonCycle10
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Total US
Energy
Sources
Is this
GOOD? EU
mandating
25-30%
Renewables
only
partitioning
of energy
sources
SOURCE
Petroleum
Coal
Natural Gas
Nuclear
Renewables
Hydroelectric
Biomass
Geothermal
Solar
Wind
PERCENTAGE
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23 Little wood
8 used to
produce
7 energy?
50
43
5
1
<0.5
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Technological breakthroughs facilitating
development of new biomass energy
systems
• New C neutral
chemical
transformation
processes for biomass
conversion to
methanol
• Developments in
hydrogen fuel cells
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DIVERSITY OF NON-TRADITIONAL
PRODUCTS POSSIBLE FROM WOOD
TODAY
Transportation
Biofuels
Pharmaceutical
Precursors
Bio-oils
Chemicals
Methanol
Electricity using
Hydrogen Fuel Cells and
Chemical Industry
Precursors
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Case 6.2.
Carbon Sequestration in a Boreal
Forest in Iceland: Effects of Foreign
and Exotic Species
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Estimated forest cover
1100 years ago (25%)
Current forest cover (1%)
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In a grazed birch forest, all
leaves from lowest brances
get grazed, otherwise
abundant basal sprouts (imp
for regen.) are grazed away
and most of /all seedlings are
grazed. Trunks get damaged
by abration by sheep horns
and from scratching.
Sheep wool
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Forest floor
1875
Iceland has:
1477
Native forest: Mountain Birch is the
single forest forming tree species
Soils: mostly uniform aeolian
andisols w/ ash layers (good for
dating), or entisols (fresh glacial till
or eroded soils)
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What to plant?
• Exotic or native species?
• Native species for conservation?
• Species to maximize carbon sequestration?
• What are the constraints and opportunities?
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Betula
pubescens
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Larix sibirica
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Pinus contorta
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Results
• Exotic species sequester more carbon
• But exotic species may alter disturbance
regimes and ecosystem processes
• Exotic species alter the biodiversity of
understory communities
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