Global warming is causing soils to release carbon into the atmosphere, exacerbating climate change. Soil organic carbon (SOC) is an important carbon pool that is sensitive to climate factors like temperature and precipitation. As temperatures rise due to global warming, it increases microbial decomposition of SOC, releasing more carbon dioxide. However, implementing strategies to sequester carbon in soils, like cover cropping, adding amendments, and reducing tillage, could help mitigate climate change by storing carbon long-term in SOC pools. Careful management of SOC is vital for protecting this important carbon sink and regulating greenhouse gas levels.

1. Effect of Global Warming on Soil Organic Carbon
Presented by,
Ms. Amruta D. Raut
Ph.D Scholar, Reg. no. Ph.D 018/20
Course Teacher and Guide
Dr. B.D. Bhakare
Head of SSAC
Department of Soil Science & Agril. Chemistry, MPKV, Rahuri

2. Outline of Presentation
Introduction
Global Warming
Soil organic carbon –
Climate change effect on SOC
Case study
SOC Sequestration- Strategies of carbon sequestration
Conclusions
• Factors affecting the response of SOC to Global
warming
• Why response of soil carbon to global warming
important??
• Measuring soil responsesto global warming.

3.  Climate change, land degradation and biodiversity loss,
soils have become one of the most vulnerable resources in
the world.
 Soils are a major carbon reservoir containing more carbon
than the atmosphere and terrestrial vegetation combined.
 Soil organic carbon (SOC) is dynamic, however, and
anthropogenic impacts on soil can turn it into either a net
sink or a net source of GHGs.
 Enormous scientific progress has been achieved in
understanding and explaining SOC dynamics.
 Protection and monitoring of SOC stocks.
Introduction

4. Definition
Global warming is the ongoing rise of the average temperature of
the Earth's climate system.
OR
A gradual increase in the overall temperature of the earth's atmosphere generally
attributed to the greenhouse effect caused by increased levels of carbon dioxide, CFCs,
and other pollutants.
 It is a major aspect of climate change which, in addition to rising global surface
temperatures,
 also includes its effects, such as changes in precipitation.
 prehistoric periods of global warming
Global Warming

5.  “Human influence on climate has been the dominant
cause of observed warming since the mid-20th century".
 The largest human influence has been the emission
of greenhouse gases, with over 90% of the impact
from carbon dioxide and methane. Fossil fuel burning is
the principal source of these gases,
with agricultural emissions and deforestation also
playing significant roles.
 Currently, surface temperatures are rising by about
0.2 °C (0.36 °F) per decade.
Intergovernmental Panel on Climate
Change (IPCC)

6. GHG emissions from Agriculture
Forestry 17.4 %
Industry 19.4%
Residential and commercial
buildings 7.9%
Transport 13.1%
Energy supply
25.9%
Waste and wastewater
2.8%
Agriculture 13.5 %
 Total global anthropogenic emission of
GHGs.
Global – 10-13%
India – 17%
 50% - CH4 emission
 70% - N2O
 CO2 flux is approximately in balance (large
annual exchanges between atmosphere and
agril. Land).
 Globally, agricultural CH4 and N2O
emissions have increased by nearly 17%.

7. Different sectors contributing to GHGs emission
(percent)
Note :
(HFC= hydroflurocarbon; PFC=
polyflurocarbon; SF6= sulfurhexafluride)
(Source : Kyoto Protocol)
Contribution of different sectors in India
(Sources of GHG emissions in India)
Water
Vapour
36-76%
CO2 9-26%
Methane 4-9%
N2O 5%
Ozone 3-7%
HFCs 2.2%
PFCs 2.2
SF6 2.2%
Energy
Land use
changes
Agriculture
Industrial
processes Wastes
Energy – 61%
Land use changes - 1%
Agriculture – 28%
Industrial processes -8%
Waste – 2%
Source – India’s initial national
communication on climate change. 2004

8. FUTURE TEMPERATURE
PROJECTION
Temperature is projected to
increase by
1.5 to 5.8 o
C by 2100
Temperature is projected to increase by 1.5 to 5.8 o
C by 2100
Future Temperature Projection

9. NITROUS
OXIDE
From IPCC
Green House Gases on the rise
Carbon Dioxide Methane

10.  All availed amenities by industrialized societies are
based on fossil fuel derived energy.
Thus, the modern civilization term “The
Carbon Civilization” or the C-Era (Rattan Lal,2007)
 The modern civilization is dependent on C-based
energy sources.
 It is literally hooked on carbon, and in need of a
big-time rehabilitation.
Soil Organic Carbon

11. Soil : A source and sink for carbon based GHGs
• Soil can be double edge sword.
• Soil emits GHGs atmosphere
thermal radiation Greenhouse effect global
warming
• GHGs – CO2 and CH4 . N2O
• The potential climate signal of these gases differs depending on their relative
greenhouse efficiency, i.e. their global warming potential (GWP). CO2 is
considered to have a GWP of 1, followed by CH4 with a 100-year GWP of
28 and N2O with the highest 100-year GWP of 265 (IPCC, 2014).

12. World soil constitute 3rd largest global C pool
Pool Amount(Pg )
Ocean 38,100
Soil (1 m depth)
SOC(soil organic carbon) 1550
SIC(soil inorganic
carbon)
950
Vegetation 610
Atmosphere 760
Fossil fuels 4130
% of global C pool (Source: Hillel et al., 2011)
Major C sink. (Source: Lal et al., 2008)

13. Soil organic carbon forms part of the natural carbon cycle
Additional
Human inputs

14. SOC : A Component of SOM
 SOM Stabilization of soil structure,
Retention and release of plant nutrients and
Maintenance of water-holding capacity.
SOM is used to describe the organic constituents in soil in various stages of
decomposition such as tissues from dead plants and animals, materials less than 2 mm
in size, and soil organisms.
 Soil Organic Carbon: A key indicator of soil health, Lal et al., 2013

15. SOM divided into different pools –
based on the time needed for full decomposition and the derived residence time of
the products in the soil (turnover time) as follows (Gougoulias et al., 2014)
 Active pools - turnover in months or few years;
 Passive pools - turnover in up to thousands of years.

16. SOC Pool is divided into different pools
Based on function of its physical and chemical stability (FAO and ITPS,
2015; O’Rourke et al., 2015)
1. Fast pool (labile or active pool)
2. Intermediate pool
3. Slow pool (refractory or stable pool)

17.  Major building block for life of all organisms in Earth.
 Basic input for crop production, important from agricultural
point of view.
Some beneficial role of SOC in soil:
 Physical
 Chemical
 Biological
Why is carbon important ?

18. C
Carbon is a
“keystone”
N P
K C
a
M
g
S
Z
n
Mn
C
l
B
o
Building of agriculture

19. Climate Change Effects on SOC  Temperature
 Precipitation
Fig. Spatial extrapolation of the temperature vulnerability of soil C stocks
(Crowther et al., 2016)
Quantifying global soil carbon losses in response to warming

20. Effects of increased CO2 concentration in the Atmosphere
 Anthropogenic increases in atmospheric CO2 may drive
increased net primary productivity (NPP), which provides the
primary input of carbon to soil, as long as nutrient and water
limitations do not occur.
 Such increased NPP is expected to stimulate plant growth,
have a negative feedback on atmospheric CO2 through increased
inputs of SOC (Van Groenigen et al., 2014; Amundson et al.,
2015).

21. Soil Organic C Dynamics
Relative
C
content
(g
C
m
-2
)
P >
D
P >
D
P <
D
P = net primary production D =
decomposition
(Janzen et al., 1998)
loss
sequestration
Original
accumulation
Conversion to
cultivated
agriculture
Adoption of
conservation
practices
Time
prairie
agroecosystem

22. Managing soil organic matter as the key to soil, air, and waterquality.
(Source: Lal et al., 2007)

23. A. Oxidation of C (as Carbon-di-oxide)
B. Agricultural practices causing reduction of SOC in
soils
Losses of Carbon from the Soil
Removal of C from fields

24. Why is the response of soil carbon to global
warming important ?
 The size of the pool of SOC is large compared to gross and net
annual fluxes of carbon to and from the terrestrial biosphere.
 Small changes in the SOC pool could have dramatic impacts on
the concentration of CO2 in theatmosphere.
 Increased release of terrestrial C under warming would lead to a
positive feedback, resulting in increased global warming.

25.  The balance of carbon inputs to , and outputs from ,
the soil
 Increasing decomposition rate under global warming
 Global and regional trends in changes in NPP and SOC loss
 Overall impact – transient versus equilibrium
effects
Factors affecting the response of SOC to
Global warming

26.  The level of SOC in a particular soil is determined by many factors including
climatic factors (e.g., temperature and moisture regimes) and edaphic factors
(e.g., soil parent material, clay content, cation exchange capacity; Dawson and
Smith et al., 2007).
 The rate of carbon input to the soil is also related to the productivity of the
vegetation growing on that soil , measured by NPP. NPP varies with climate,
land cover, species composition, and soil type (Falge et al.,2002).
 The balance of inputs to & outputs from the soil

27.  Increasing decomposition rate under global
warming
 Increased temperatures accelerate rates of microbial
decomposition.
 Increase CO2 emission by soil respiration.
 Results a positive feedback to global warming.

28. Assumed temperature dependencies of SOC decomposition
(Parton et al., 1987)

29.  Global and regional trends in changes in
NPP and SOC loss
 The overall response of soil carbon to global warming will
depend on increased carbon input to the soil due to increased
plant productivity and increasing the rate of decomposition at
warmer temperature.

30.  Overall impact – transient versus
equilibrium effects
 An equilibrium response of SOC to global warming is the net
difference between two equilibrium states of ecosystem,
regardless of the length of time required to reach the new
equilibrium after climate change.
 transient response of SOC to climate change is expected to be
regulated but the equilibrium response dominated by change in
NPP (Davidsons and Jenssens et al., 2006) and other related to
soil capacity to retain SOC (Rasmunssen et al., 2006).

31.  Some studies suggest that recalcitrant C is not sensitive to
temperature variation (Giardina and Ryan et al., 2000).
 Recalcitrant and labile pools have a similar temperature
sensitivity (Fang et al., 2005).
 The temperature dependence of SOC decomposition is the result of a
number of processes that effectively contributes to the rate of
mineralization (Agren and Wetterstedt et al., 2007).
Temperature sensitivity of SOC pools

32. Schematic diagram of temperature sensitivities derived from various
methods and their affecting factors.
(Source : Smith et al.,2007)

33. Potential changes in organic C stocks in major pools in a simulated upland soil
and a permafrost soil in response to global warming by 2100, and not
accounting for the interactive effects of elevated [CO2], atmospheric N
deposition and changes in precipitation.
modified from Davidson and Janssens et al., 2006
Organic C pools and
temperature – sensitive
ecosystem
Organic C
stock (Gt C)
Turnover
time ( years)
Potential loss by
2100 (Gt C)
References
Upland soil (litter layer) 200 6 30 Jones et al., (2005)
Upland soil (1 m depth)
Labile pool 20 6 3 Jones et al., (2005)
Slow pool 700 18 40 Jones et al., (2005)
Recalcitrant pool 100 1000 0.1 Jones et al., (2005)
Permafrost (3 m depth) 400 4 100 Gruber et al.,
(2004)

34. Effect of elevated CO2 on SOC and SOCpools
 Increase in CO2 concentration by 40% since
the industrial revolution (280 ppm in 1750
to 395.94 ppm in September 14, 2015)
 Under elevated CO2 concentrations C3
plants respond with increased rates of
photosynthesis, increased productivity and
increased biomass (Ainsworth and Long et
al., 2005), especially under N inputs) and
increased water availability (Housman et al.,
2006).
Singh et al., 2011

35. Sensitive/vulnerable regions and soils
 High latitude regions are thought to be particularly vulnerable
 High latitudes are projected to experience some of the greatest
warming (Mitchell et al ., 2004).
 This is particularly true of permafrost soils in the taiga and tundra
that hold around 500 Pg C, and could lose this carbon rapidly under
warming ( Zimov et al ., 2006).

36. MEASURING SOIL RESPONSES TO GLOBAL WARMING
A. Soil respiration measurement in the laboratory
B. Soil respiration measurement in the field
1. Static absorption
2. Dynamic (or steady-state) chambers
3. Enrichment(or non-steady-state) methods

37. A. Soil respiration measurement in the laboratory
 It involves the measurement of CO2 released from or oxygen uptake
by known quantities of soil sample or undisturbed soil cores incubated
under controlled conditions.
 Procedure for this measurement is that known quantity of soil sample
and alkaline absorbent held by an open container are enclosed in a
container and soil respiration rate was obtained by the amount of CO2
trapped in the alkali during a given period.

38. 1. Static absorption
 This method uses alkali solution (KOH or NaOH) contained in a dish
and placed within an isolating chamber for several hours to day in
period.
 The CO2 efflux is a function of gain in CO2 trapped in the absorbent,
the exposing time, and the area underneath the chamber
A. Soil respiration measurement in the field

39. 2. Dynamic (or steady-state) chambers
Where, Sr is the efflux of CO2 from the soil,
∆c is the difference in CO2 mass fraction in the incoming and outgoing air streams,
f is the gas flow rate through the chamber, and
A is the surface area covered by the chamber (Nakayama,et al., 1990).
Sr =∆c(f/A)

40. 3. Enrichment (or non-steady-state)
methods
The soil efflux(Sr) can be measured by:
Sr=(∆c/∆t)(V/A)
where ∆c is the CO2 concentration increment in the chamber in the time
interval ∆t,
V is the volume of air within the chamber, and
A is the soil surface area covered by the chamber.

41. Reduce GHG emissions – Holding carbon is the need of
the day
Keeps Carbon out of the Atmosphere!
Holding carbon in the soil!

42. Soil organic carbon sequestration is the process by which carbon is
fixed from the atmosphere via plants or organic residues and stored in the soil.
When dealing with CO2, SOC sequestration involves three stages:
1) the removal of CO2 from the atmosphere via plant photosynthesis;
2) the transfer of carbon from CO2 to plant biomass; and
3) the transfer of carbon from plant biomass to the soil where it is
stored in the form of SOC in the most labile pool.

43. Sequestering
carbon
Creating negative
carbon emission
Mulching
Cover
cropping
Soil
amendments
*Biochar
*Manure
Creating positive
carbon budget
Biofertilizer
Chemical
fertilizer
Strategies of soil carbon sequestration
(Lal et al., 2004)

44.  Carbon content in soil is about twice as large as that of in the
atmosphere and about three times that in the vegetation.
 Global warming causes large amounts of carbon in terrestrial soils
to be lost to atmosphere , making them a greater carbon source than
sink.
 Strategies of soil carbon sequestration will help to mitigate
Climate change (Global warming) itself.
Conclusions

45. Soil is meant to be covered
Manage soil carbon - make the world a better place.

46. Soil is meant to be covered.
Manage soil carbon - make the world a better
place.
Thank you for your attention!
We need stronger footprints on / for soils!