Soil Inorganic Carbon and climate change in drylands? An emerging issue?
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Transcript of Soil Inorganic Carbon and climate change in drylands? An emerging issue?
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Chevallier T, Cournac L, Bernoux M, Cardinael R, Cozzi T, Girardin C, Chenu C
Soil Inorganic Carbon and climate change in drylands?
An emerging issue?
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Soil Organic CarbonUnlocking the potential of mitigating and adapting to a changing climate
Theme 3. 3. Managing SOC in dryland soils
About 30 % of the Soil Organic Carbon are stored in dryland soils
In drylands
SOC
SIC
1583 Gt
946 Gt
68
32
916 Gt de SIC
431 Gt de SOC
Soil inorganic carbon ?
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SOC
SIC
SIC kg m-2
8-64 kg m-2
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Monger et al. 15, Geology
• SIC interacts with CO2 driven by biotic activities
• SOC and SIC evolution are likely link, (time scale ?)
CaCO3 + H2O + CO2
SIC are• CaCO3
• HCO3-
• H2CO3
• CO2
• Solid, in solution, gaz
Solid-solution-gaz equilibirum = f(pH, H20, pCO2, Ca2+, HCO3-)
Is SIC pool important to consider in
SOC studies in calcacerous soils ?
CaCO3 + 2H+ Ca2+ + CO2 + H2O
Ca2+ + 2 HCO3-
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• Analyzing Soil Carbon , SOC and SIC and bulk densityContents and Stocks of SOC
Inorganic soil carbon, a methodological issue
• Dynamics of C contents and stocks Impact of climate change or land uses on SOC, SIC evolution…Does the CO2 measured come only from SOC decomposition ?
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CO2 CO2
Stevendon and Verburg, 06, Bertrand et al. 07, Rovira and Vallejo 08, Inglima et al. 09, Ramnarine et al. 12, Tamir et al. 11, 12, Ahmad et al. 14, Chevallier et al. 16…
d13C of SIC about +2 à -11 ‰
d13C of SOC about -25 à -27 ‰ (C3 plants)
d13C of soil in between
d13C-CO2 = f d13CSIC + (1-f) d13CSOC
Carbon Isotopic measurements
d13Csoil = f d13CSIC + (1-f) d13CSOC
If no isotopic fractionations between
• SOC and CO2 (biological activities)
• CaCO3, HCO3-, CO2
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Red reddish brown Cambisol
36% clay, 50% silt,14% sand, ; pH 8,9
22.1 g SOC kg-1 with 44.2 g SIC kg-1
20
40
30
50
4 incubation temperatures (°C) 28 days
Experimental settings
δ13CSOC = - 20.3 ± 4.4 ‰ δ13CSIC = - 4.1 ± 0.4 ‰
δ13Csoil = - 8.4 ± 0.4 ‰
Does temperature incubation
impact SOC and SIC dynamics ?
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Mee
rman
s et a
l. 20
12
0-10
10-30
70-100
160-180Inter rowTree row
0 25 50 750
20
40
60
80
100
120
140
160
180
C content (g C kg-1 soil) -30 -25 -20 -15 -10 -5 0
d13C (‰)
20-10 gSOC kg-1
65 gSIC kg-1
Incubation at 20°C, 28 days
SIC
SOC in Tree rowSOC inter rowIs depth impact SOC and SIC
dynamic in a same way ?
Is there a correlation between
SOC and SIC dynamic ?
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Results
10 20 30 40 50 60
-25
-20
-15
-10
-5
0
Temperature (°C)
d13 C
(‰
)
CO2 from soil (0-7 days)CO2 from soil (7-28 days)
SIC
SOC
-30 -25 -20 -15 -10 -5 00
20
40
60
80
100
120
140
160
180
d13C (‰)
Dept
h (c
m)
SIC
SOC in Tree rowSOC inter rowCO2 from soil
SIC and SOC contribute both to emitted CO2
d13CCO2 values higher with temperatures and depth
d13CCO2 between of d13CSIC and d13CSOC
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Results
10 20 30 40 50 60
-25
-20
-15
-10
-5
0
Temperature (°C)
d13 C
(‰
)
CO2 from soil (0-7 days)CO2 from soil (7-28 days)
SIC
SOC
-30 -25 -20 -15 -10 -5 00
20406080
100120140160180
d13C (‰)
Dep
th (
cm)
SIC
SOC in Tree rowSOC inter rowCO2 from soil
f = 0.20 – 0.24
f = 0.64
f = 0.2 – 0.1
f = 0.7- 0.3
d13C-CO2 = f d13CSIC + (1-f) d13CSOC
SIC and SOC contributions to emitted CO2
Higher contribution of SIC to CO2 emissions with
temperatures and depth
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Resultsd1
3 C (
‰)
CO2 from soil (0-7 days)CO2 from soil (7-28 days)
SIC
SOC
SIC
SOC in Tree rowSOC inter rowCO2 from soil
10 20 30 40 50 60
-25
-20
-15
-10
-5
0
-30 -25 -20 -15 -10 -5 00
20
40
60
80
100
120
140
160
180
d13C (‰)
Dep
th (
cm)
Temperature (°C)
BUT If there is isotopic fractionation
between SIC and derived CO2 from SIC
d13C-CO2 = f d13CSIC + (1-f) d13CSOC
SIC and SOC contributions to emitted CO2
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Resultsd1
3 C (
‰)
CO2 from soil (0-7 days)CO2 from soil (7-28 days)
SIC
SOC
SIC
SOC in Tree rowSOC inter rowCO2 from soil
10 20 30 40 50 60
-25
-20
-15
-10
-5
0
CO2 from SOC with isotopic fractionation
CO2 from SIC with isotopic fractionation-30 -25 -20 -15 -10 -5 0
0
20
40
60
80
100
120
140
160
180
d13C (‰)
Dep
th (
cm)
Temperature (°C)
BUT If there is isotopic fractionation
between SIC and derived CO2 from SIC
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Resultsd1
3 C (
‰)
CO2 from soil (0-7 days)CO2 from soil (7-28 days)
SIC
SOC
SIC
SOC in Tree rowSOC inter rowCO2 from soil
10 20 30 40 50 60
-25
-20
-15
-10
-5
0
CO2 from SOC with isotopic fractionation
CO2 from SIC with isotopic fractionation-30 -25 -20 -15 -10 -5 0
0
20
40
60
80
100
120
140
160
180
d13C (‰)
Dep
th (
cm)
Temperature (°C)
If there is isotopic fractionation
between SIC and derived CO2 from SIC,
SIC seems to contribute more than
100% to emitted CO2 !
Isotopic fractionation between SIC
and derived CO2 from SIC ?
How much and at what step ?
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Results
L 0-10 cm
10-30 cm
70-100 cm
160-180 cm
0
100
200
300
400
500
600C-CO2 from SIC
C-CO2 from SOC
Tree row
f = 0.20
f = 0.64
20 30 40 500
200
400
600
800
1000
1200C-CO2 from SOC
C-CO2 from SIC
Incubation temperature (°C)
C-CO2 emissions (µg g-1 soil)
Calculated amounts of CO2 derived from SIC
and SOC are both stimulated by temperature
As amounts of CO2 emitted from SOC,
amounts of CO2 emitted from SIC in depth are low.
Amount of C-CO2 from SIC = f CO2d13C-CO2 = f d13CSIC + (1-f) d13CSOC
C-CO2 emissions (µg g-1 soil)
0-10 cm
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Results
0
100
200
300
400
500
600
C-CO
2 em
issio
ns (µ
g g-
1 so
il)
L 0-10 cm
10-30 cm
70-100 cm
160-180 cm
0
100
200
300
400
500
600C-CO2 from SIC
C-CO2 from SOC
Inter rowTree row
f = 0.20
f = 0.64f = 0.24
20 30 40 500
200
400
600
800
1000
1200C-CO2 from SOC
C-CO2 from SIC
Incubation temperature (°C)
C-CO2 emissions (µg g-1 soil)
Calculated amounts of CO2 derived from SIC
and SOC are both stimulated by temperature
Amounts of CO2 emitted from SOC and SIC
are higher under Tree row than under Inter row.
Amount of C-CO2 from SIC = f CO2d13C-CO2 = f d13CSIC + (1-f) d13CSOC
C-CO2 emissions (µg g-1 soil)
0-10 cm 0-10 cm
19 gSOC kg-1 soil 11 gSOC kg-1 soil
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Discussion 1. The main source of emitted CO2 is SOC decomposition
Total C-CO2 emissions µgC-CO2 g-1 soil
d13CCO2 (‰)
0 100 200 300 400 500 600 700 800
-25
-20
-15
-10
-5
0
40-50°C
Tunisian samplesFrench samples
0 100 200 300 400 500 600 700
-25
-20
-15
-10
-5
0
0-7 days7-28 days
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Discussion
0 100 200 300 400 500 600 700 8000
100
200
300
400
500
f(x) = 0.1613967885811 x + 16.2905295692514R² = 0.924319397139957
C-CO2 from SIC, µgC-CO2 g-1 soil
C-CO2 from SOC, µgC-CO2 g-1 soil
40°C
50°C
1. The main source of emitted CO2 is SOC decomposition
2. CO2 derived from SIC and SOC are correlated
Total C-CO2 emissions µgC-CO2 g-1 soil
d13CCO2 (‰)
0 100 200 300 400 500 600 700 800
-25
-20
-15
-10
-5
0
40-50°C
Tunisian samplesFrench samples
0 100 200 300 400 500 600 700
-25
-20
-15
-10
-5
0
0-7 days7-28 days
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Discussion
SIC SOC
d13CSIC d13CSOC
Total CO2 emissions
Isotopic exchanges
1. The main source of emitted CO2 is SOC decomposition
2. CO2 derived from SIC and SOC are correlated
CO2 from SIC depends on SOC decomposition ?
Isotopic exchanges, CO2 from SIC could also comes
from SOC ?
C-CO2 from SOC, µgC-CO2 g-1 soil
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Discussion
SIC SOC
d13CSIC d13CSOC
Total CO2 emissions
Isotopic exchanges
1. The main source of emitted CO2 is SOC decomposition
2. CO2 derived from SIC and SOC are correlated
CO2 from SIC depends on SOC decomposition ?
Isotopic exchanges, CO2 from SIC came from SOC ?
d13CCO2 (‰)
C-CO2 from SOC, µgC-CO2 g-1 soil
At higher temperatures something
different happen, CO2 from SIC are
stimulated ?
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CO2 derived from SIC and SOC are correlated
except at high temperatures.
Climate issueCO2 derived from SIC and SOC
are both stimulated by temperature
CO2 and 13CO2 measurements -Isotopic fractionation, isotopic exchanges, alkali traps,
time of incubation.
Other factors to measure (O2, Ca2+)
• SIC is not an inert C pool
• SIC contribute to CO2 emissions
Soil Inorganic Carbon and climate change in drylands?An emerging issue?
SIC is dynamic in short term incubations
Methodological issue
SIC and SOC dynamics with water content, irrigation ?
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Soil Inorganic Carbon and climate change in drylands?
An emerging issue?
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