Soil Inorganic Carbon and climate change in drylands? An emerging issue?
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This presentation was presented during the 1 Parallel session on Theme 3.3, Managing SOC in: Dryland soils, of the Global Symposium on Soil Organic Carbon that took place in Rome 21-23 March 2017. The presentation was made by Ms. Tiphaine Chevallier, from IRD – USA, in FAO Hq, Rome
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Soil Inorganic Carbon and climate change in drylands? An emerging issue?
- 1. 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?
- 2. Soil Organic Carbon Unlocking 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 ?
- 3. SOC SIC SIC kg m-2 8-64 kg m-2
- 5. 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 -
- 6. • Analyzing Soil Carbon , SOC and SIC and bulk density Contents 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 ?
- 7. 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
- 8. 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 ?
- 9. Meermansetal.2012 0-10 10-30 70-100 160-180Inter row Tree row 0 20 40 60 80 100 120 140 160 180 0 25 50 75 C content (g C kg-1 soil) -30 -20 -10 0 d13C (‰) 20-10 gSOC kg-1 65 gSIC kg-1 Incubation at 20°C, 28 days SIC SOC in Tree row SOC inter rowIs depth impact SOC and SIC dynamic in a same way ? Is there a correlation between SOC and SIC dynamic ?
- 10. Results -25 -20 -15 -10 -5 0 10 20 30 40 50 60 Temperature (°C) d13C(‰) CO2 from soil (0-7 days) CO2 from soil (7-28 days) SIC SOC 0 20 40 60 80 100 120 140 160 180 -30 -25 -20 -15 -10 -5 0 Depth(cm) d13C (‰) SIC SOC in Tree row SOC inter row CO2 from soil SIC and SOC contribute both to emitted CO2 d13CCO2 values higher with temperatures and depth d13CCO2 between of d13CSIC and d13CSOC
- 11. Results -25 -20 -15 -10 -5 0 10 20 30 40 50 60 Temperature (°C) d13C(‰) CO2 from soil (0-7 days) CO2 from soil (7-28 days) SIC SOC 0 20 40 60 80 100 120 140 160 180 -30 -25 -20 -15 -10 -5 0 Depth(cm) d13C (‰) SIC SOC in Tree row SOC inter row CO2 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
- 12. Resultsd13C(‰) CO2 from soil (0-7 days) CO2 from soil (7-28 days) SIC SOC SIC SOC in Tree row SOC inter row CO2 from soil -25 -20 -15 -10 -5 0 10 20 30 40 50 60 0 20 40 60 80 100 120 140 160 180 -30 -25 -20 -15 -10 -5 0 d13C (‰) Depth(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
- 13. Resultsd13C(‰) CO2 from soil (0-7 days) CO2 from soil (7-28 days) SIC SOC SIC SOC in Tree row SOC inter row CO2 from soil -25 -20 -15 -10 -5 0 10 20 30 40 50 60 CO2 from SOC with isotopic fractionation CO2 from SIC with isotopic fractionation 0 20 40 60 80 100 120 140 160 180 -30 -25 -20 -15 -10 -5 0 d13C (‰) Depth(cm) Temperature (°C) BUT If there is isotopic fractionation between SIC and derived CO2 from SIC
- 14. Resultsd13C(‰) CO2 from soil (0-7 days) CO2 from soil (7-28 days) SIC SOC SIC SOC in Tree row SOC inter row CO2 from soil -25 -20 -15 -10 -5 0 10 20 30 40 50 60 CO2 from SOC with isotopic fractionation CO2 from SIC with isotopic fractionation 0 20 40 60 80 100 120 140 160 180 -30 -25 -20 -15 -10 -5 0 d13C (‰) Depth(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 ?
- 15. Results 0 100 200 300 400 500 600 L 0-10 cm 10-30 cm 70-100 cm 160-180 cm C-CO2 from SIC C-CO2 from SOC Tree row f = 0.20 f = 0.64 0 200 400 600 800 1000 1200 20 30 40 50 Incubation temperature (°C) C-CO2 from SOC C-CO2 from SIC 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 CO2 d13C-CO2 = f d13CSIC + (1-f) d13CSOC C-CO2 emissions (µg g-1 soil) 0-10 cm
- 16. Results 0 100 200 300 400 500 600 C-CO2emissions(µgg-1soil) 0 100 200 300 400 500 600 L 0-10 cm 10-30 cm 70-100 cm 160-180 cm C-CO2 from SIC C-CO2 from SOC Inter rowTree row f = 0.20 f = 0.64 f = 0.24 0 200 400 600 800 1000 1200 20 30 40 50 Incubation temperature (°C) C-CO2 from SOC C-CO2 from SIC 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 CO2 d13C-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
- 17. Discussion 1. The main source of emitted CO2 is SOC decomposition Total C-CO2 emissions µgC-CO2 g-1 soil d13CCO2 (‰) -25 -20 -15 -10 -5 0 0 100 200 300 400 500 600 700 800 40-50°C Tunisian samples French samples -25 -20 -15 -10 -5 0 0 100 200 300 400 500 600 700 0-7 days 7-28 days
- 18. Discussion CO2SIC = 0,16 CO2SOC + 16,3 R² = 0,9 0 100 200 300 400 500 0 200 400 600 800 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 (‰) -25 -20 -15 -10 -5 0 0 100 200 300 400 500 600 700 800 40-50°C Tunisian samples French samples -25 -20 -15 -10 -5 0 0 100 200 300 400 500 600 700 0-7 days 7-28 days
- 19. 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
- 20. 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 ?
- 21. CO2 derived from SIC and SOC are correlated except at high temperatures. Climate issue CO2 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 ?
- 22. Soil Inorganic Carbon and climate change in drylands? An emerging issue? Thank you for listening
Editor's Notes
- Why is it important to talk about soil iorganic carbon in a symposium on organic carbon ? 2/3 de SOC 1/3 de SIC globalement. La majeure partie des SIC sont dans les drylands
- Spatial distribution of SIC was strongly linked to the underlying geology.
- Where there are high SIC contents there are not so much SOC. Souvent le SOC décroit avec la profondeur alors que pour les SIC c’est le contraire (Chine, Wang et al. 10,Sc. Total Envi ou Tamir et al. 12)
- The increase in CO2 concentration due to microbial respiration is considered the main factor responsible for the dissolution of carbonates and istopic exchanges of C with soil carbonates.
- Infra red spectrometry… mais on va se concentrer sur la partie dynamic!
- δ13C des SIC dans la biblio: -10,9 et +1,9 pour Bertrand et al. 07 -8,7 (lime) pour Ahmad et al. 14 -4 Chevallier et al. 16 -2 à -4 Cozzi 0.33 +/- 0.84‰ Inglima et al. 09 -0,9 pour Stevenson and verburg 06 -7,1 pour Tamir et al. 12 Dans Tamir et al. 11 Lithogenic carbonate, which is generally derived from marine limestone, has δ13C = 0‰ (West et al., 1988), and secondary carbonate has δ13C = −10 to −12.5‰ (Salomons and Mook, 1976; Magaritz and Amiel, 1980). pour Nordt et al. 98 les SIC parents sont de l’ordre de +1 et les pedogénétic de -2 à -4. -1,7 à -0,8 Nordt et al. 98 -11 à -11,5 pour Rovira and Vallejo 08 -6.8 à -1.1 pour Ranmarine et al. 12 plus vers -1.1 en profondeur (δ13C augmente avec la profondeur) L’inverse pour Tamir et al. 12, evolution du δ13CSIC avec la profondeur de -10.5 à -13.6‰ Active Carbonates (subject to precipitation/dissolution/recrystallization…) have a δ13C poorer in 13C than total carbonates ( -7 vs -11). Cette difference se mesure jusqu’à des profondeurs importantes, de plus de 2 mètres (impact de la MO à ces profondeur, via HCO3- leaching ?) See Tamir et al. 12
- Avec la profondeur augmentation de l’ordre de + 10‰ du δ13C Avec la temperature augmentation δ13C de l’ordre de + 8‰ à 7 jours mais de +3‰ à 28 jours d’incubation
- Contribution des SIC aux émissions de CO2 de 10 à 70 %. Valeurs restinclières pour 28 jours
- Discussion pour les contributions des SIC différentes entre tree row et inter row : peut-être que cela peut venir aussi d’une différence de δ13C-SOC entre les deux parcelles, + de POM dont le δ13C peut de différentes valeurs que la SOM totale ? (Ranmarine et al. 12)
- The more the CO2 was emitted, the more the CO2 was depleted in 13C, the SOC is the principal pool of CO2 emissions. Except at high temperatures.
- The more the CO2 was emitted, the more the CO2 was depleted in 13C, the SOC is the principal pool of CO2 emissions. Except at high temperatures.
- The more the CO2 was emitted, the more the CO2 was depleted in 13C, the SOC is the principal pool of CO2 emissions. Except at high temperatures.
- The more the CO2 was emitted, the more the CO2 was depleted in 13C, the SOC is the principal pool of CO2 emissions. Except at high temperatures.
- Conclusion The increase in CO2 concentration due to microbial respiration is considered the main factor responsible for the dissolution of carbonates and istopic exchanges of C with soil carbonates. Method alkali traps favor dissolution of carbonates ? Not sure…debate in literature, first resulats too variable to conclude. SIC is not an homogenous pool, d13CSIC and reactivity (Tamir et al. 12, Bertrand et al. 07)