Global Climate Change and Soil Carbon Dynamics

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Global Climate Change and Soil Carbon Dynamics

• R. Lal
• Carbon Management and Sequestration Center
• The Ohio State University
• Columbus, Ohio 43210

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Several trace gases (CO2, CH4, N2O) in the
atmosphere have the same effect as does the glass
in the greenhouse, and are thus called
greenhouse gases.
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Greenhouse effect

• It is a biogeographical process that has been
  essential to the evolution of life on earth.
• The greenhouse effect has raised the average
  temperature at the surface from -18C to 15C
  (33C ) above what it would otherwise have been.
• The greenhouse effect has allowed liquid water to
  remain stable, and provided the fundamental
  substrate for biological activity as we know it.

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Global warming

• It is the acceleration of the greenhouse effect
  leading to increase in global temperature at a
  rate gt0.1ºC/decade such that ecosystems cannot
  adjust to the rapid change.

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Greenhouse effect and the biosphere

• For each 1C increase in global temperature, the
  vegetational zones may move poleward by 200 to
  300 km.

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Rate of increase of GHGs that have the same
effect in the atmosphere as does the glass in a
greenhouse
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Climate Change

• ?T over 20th century....0.60.2C
• Rate of ?T since 1950..0.17C/decade
• Sea level rise over 20th century...0.1-0.2m
• Change in precipitation0.5-1/decade
• Extreme events in Northern Hemisphere.. 2-4
• in frequency of heavy precipitation

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Projected climate change with 2 x CO2
Temperature.. 2-4C (1.6 C by
2050) Precipitation.. 18.5 mm/d (10) Sea
level. 15-75 cm TRF area
75 Semi-desert area -20 Desert area.
-60 Prentice and Fung (1990) Cheddadi
et al. (2001)
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Contemporary Carbon Budget
Source 1980s 1990s
-------------Pg C/yr--------- -------------Pg C/yr---------
Sources Fossil fuel burning Land use change/soil cultivation Sinks Atmosphere Ocean Land/soil Unknown terrestrial sink 5.4 1.7 3.3 1.9 0.2 1.9 6.3 1.6 3.2 1.7 1.4 2-4
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How much C is in soil?

• (i) Soil organic C 1550 billion tonnes (Pg)
• Soil inorganic C 750 Pg
• Total 2300 Pg
• (ii) Atmosphere 720 Pg
• (iii) Biota 560 Pg
• (iv) Ocean 38,000 Pg
• SOC pool 40 - 100 Mg/ha

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Mean residence time of C in different pools

• The average atom of C spends about
• 5 yrs in the atmosphere,
• 10 yrs in vegetation (including trees),
• 35 yrs in soil, and
• 100 yrs in the sea.
• Residence time pool / flux
• The residence time is longer in soils of high
  latitude.

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Soil to Vegetation C Density (adapted from Dixon
et al., 1994)
Latitude Soil CVegetation C
High Mid Low 8.7 7.5 1.9 0.7 1.0 0.2
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Historical Change in World Forests Since 1850 and
the Net C Flux (Houghton, 1995).
Biome Area (Mha) Area (Mha) Net release (Pg)
Biome 1850 1980 Net release (Pg)
Boreal Temperate Tropical Total 1172 1583 2675 5430 1167 1492 2167 4827 4 27 52 83
Mostly biomass C
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Soil Degradation and Soil Organic Carbon (SOC)
Pool

• Soil degradation depletes SOC pool by
• Reducing biomass C input into soil,
• Disruption in elemental cycling,
• Decline in soil resilience, and
• Emission of greenhouse gases into the atmosphere.

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What is the fate of C in runoff?
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Soil erosion and C emission

• World.. 1.1 Pg C/y
• USA. 15 Tg C/y
• Brazil.. 60 Tg C/y

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The magnitude of soil C loss

• 30-40 Mg/ha

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Anthropogenic emissions (1850-2000)

• 1. Fossil fuel 270 30 Pg
• 2. Land use change 136 55 Pg
• Soil 78 12

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Carbon Cycling in Terrestrial Ecosystems (adapted
from Zak et al., 2000)
CO2
Plant productivity
Leaf and root litter Production, mortality and
chemistry
Soil NH4 availability
Substrate availability
Microbial biomass Growth, maintenance and
mortality
Soil C pool
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C Sequestration
Capturing and securely storing atmospheric C in a
long-lived pool by (i) Biotic, and (ii) Abiotic
processes
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Recommended agricultural practices and soil carbon
Lal et al., 1998
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Sustainability of a land use system
CNPP
Sl

n
(? Ci)
i1
Sl Sustainability index of a land use
system CNPP C output as net primary
productivity Ci C input from all factors of
production
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Hidden C costs of tillage methods
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Hidden C cost of fertilizers
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Hidden C cost of irrigation
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Hidden C cost of pesticides
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Nutrient requirements for soil carbon
sequestration

• Adoption of improved agricultural practices and
  recommended rates of fertilizers and irrigation
  etc. are adequate for achieving the desired rates
  of soil C sequestration provided that crop
  residues and cattle manure are returned to the
  soil.

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Nutrients and residue required to sequester 100
kg of soil carbon

• N.. 8.33 kg
• P.. 2.0 kg
• S.. 1.43 kg
• C.. 1000 kg (10 efficiency, 2500 kg of residue)

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Nutrients contained in crop residues

• 1 Mg of cereal residues contain
• N.. 12-15 kg
• P.. 1-4 kg
• S . 1-2 kg
• With humification efficiency of 10 to 15, these
  nutrients are enough for converting C in residue
  into humus.

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Land use in Brazil
FAO (1999)
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Fossil fuel emissions in Brazil
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Soil C sequestration by conversion to a no-till
system in southern Brazil (Lal, 2002)
Soil type/ecosystem Increase in SOC content Duration (y) Reference
Semi-deciduous sub-tropical forest Rhodic Ferralsol Acrisol Oxisol Acrisol Rhodic Ferralsol 0.84 to 1.10 Increase C to 10-cm depth 1.3 Mg/ha/y 0.8 to 1.0 Mg/ha/y 38 to 51 Mg/ha of CO2 60 reduction of SOC in plow till and 43 in no-till in 0-5 cm depth 10 11 9 22 12 13 Riezebos Loerts, 1998 DeMaria et al., 1999 Bayer et al., 2000 Sa et al., 2002 Bayer et al., 2001 Freixo et al., 2002
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Potential of soil carbon sequestration in Brazil
(Lal, 2002)
Strategy Potential of C sequestration (Tg C/y)
A. Soil restoration 1. Erosion control 2. Desertification control on 70 Mha _at_ 0.1 Mg C/ha/y B. Improved management 3. Conservation tillage on 40 Mha _at_ 0.5 Mg C/ha/y 4. Grazing land management on 185 Mha _at_ 0.1 Mg C/ha/y 5. Management of permanent crops on 12 Mha _at_ 0.1 Mg C/ha/y C. SIC sequestration on 70 Mha _at_ 0.05 Mg C/ha/y Total 60 7 20 18 1 4 110
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Agricultural soils and mitigation of GHE

• 1 bbl of diesel 220 L
• 1 L of diesel 0.73 Kg C
• ? 1 ton of C 1370 L of diesel 6.2 bbl of
  diesel
• C sequestration potential of ag soils in Brazil
  600 to 700 million barrels of diesel/y.

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Global potential of SOC sequestration
1-2 Pg C/yr (6-12 billion barrels of diesel/yr)
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The Kyoto-Bonn Accord

• The Kyoto Protocol as revised in Bonn on 23 July
  2001 added two new items
• 1. Countries are allowed to subtract from their
  industrial C emissions certain increases in
  carbon sequestered in sinks such as forests and
  soils.
• 2. A second key provision involves the ability to
  trade emission allowances, which can reduce
  abatement costs by between 50 and 75.

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The bio-carbon fund

• 100 million fund launched by the World Bank.
• The Prototype C fund.
• Etc.

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Role of soil and biomass C in global C
management. Source The Global Energy Technology
Strategy, Battelle, Washington, D.C., 1998
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Collaboration between U.S. and Brazil

• There is a strong need to develop regional
  programs on soil carbon sequestration.
• There are numerous topics of mutual interest.
• Opportunities for conducting cooperative research
  programs are numerous.

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Some topics of mutual interest

1. Assess soil C sequestration potential of
   different biomes in Americas for major land uses.
2. Quantify ancillary benefits.
3. Develop mechanisms for scientific exchange.