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Biogeochemical feebacks to climate change:
insights into soil moisture controls on soil
heterotrophic respiration
Claire C...
Intro: Soil moisture affects soil C dynamics
• Major driver but much less studied than temperature
• Responsible of consid...
Present challenges : Improve C & N dynamics models
3
Same rate
modifiers for
all pools
e.g. Daisy (Hansen et al. 1991)
sam...
1- Moisture effects strongly depends on soil
characteristics
Soil respiration-moisture functions: empirical models
• Soil respiration-moisture meta-analysis
[Clay]
100 to 1000 g kg-1
...
2- Mechanistic approaches to describe the
effect of soil moisture on heterotrophic
respiration: accounting for soil small ...
Moisture effects on soil microbial activity
Moyano et al. 2013, SBB
Dryconditions
Saturatedconditions
Soil particle Pore w...
Mechanistic prediction of soil OM decomposition
with moisture
• Soil characteristics :
 Soil particles and pores
architec...
A mechanistic model accounting for architecture
• MOSAIC II (Monga et al. 2007, Ngom et al. 2012)
Ψ= -
20cm
Voids modeling...
3- Interactions between cropping practices,
soil moisture and soil respiration
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
5 10 15 20 25 30 35 40 45
Experiment duration (years )
(a)
RelativeSOCstockdifferen...
CO2CO2
water
Corg
Corg
C storage under no tillage
• Processes of additional C storage:
• Consequences, feedbacks on CO2 em...
Conclusion
• Magnitude, timing, sign of climate–carbon cycle feedback
will depend on the response of soil carbon to climat...
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Chenu c 20150707_1700_upmc_jussieu_-_room_101

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Chenu c 20150707_1700_upmc_jussieu_-_room_101

  1. 1. Biogeochemical feebacks to climate change: insights into soil moisture controls on soil heterotrophic respiration Claire Chenu1,4, F. Moyano1P. Garnier2,4, I. Virto3 1- Bioemco laboratory, AgroParisTech, CNRS, INRA, UPMC, Grignon, France 2- EGC laboratory, INRA-AgroParisTech, Grignon, France 3- Universidad de Navarra, Pampeluna, Espana 4- present address: Ecosys AgroParisTech INRA, Grignon, France chenu@grignon.inra.fr MEPSOM project Carbosoil
  2. 2. Intro: Soil moisture affects soil C dynamics • Major driver but much less studied than temperature • Responsible of considerable uncertainty in predicting global soil C changes (Falloon et al. 2011) – e.g. ≠ moisture functions => 4% ≠ in global soil C stocks in 2100 Water Organic Matter Productivity Microbial Growth and Activity Soil Structure / Composition Nutrient supply Decomposition and synthesis Substrate supply (energy + nutrients) Organic matter accumulation Pore size distribution Aggregate formation Habitat Plant available water Excudates and litter input Diffusion, oxygen availability EPS effect on water retention Moyano et al. 2013, SBB • Forecasted: – ≠ steady state moisture conditions – ≠ wetting – drying events
  3. 3. Present challenges : Improve C & N dynamics models 3 Same rate modifiers for all pools e.g. Daisy (Hansen et al. 1991) same rate modifiers for all soils Empirical moisture rate modifiers based on limited data kθ = RFθ x k
  4. 4. 1- Moisture effects strongly depends on soil characteristics
  5. 5. Soil respiration-moisture functions: empirical models • Soil respiration-moisture meta-analysis [Clay] 100 to 1000 g kg-1 [OC] 5 to 50 mg g-1 soil BD 0.6 to 1.6 g cm-3 Relativesoilrespiration => New statistical functions (Moyano et al. 2012, Biogeosciences) Application to 106 soils from England and Wales & comparison with current functions
  6. 6. 2- Mechanistic approaches to describe the effect of soil moisture on heterotrophic respiration: accounting for soil small scale heterogeneity
  7. 7. Moisture effects on soil microbial activity Moyano et al. 2013, SBB Dryconditions Saturatedconditions Soil particle Pore waterSubstrateMicrobial cell A B C Gas transport Solute transport
  8. 8. Mechanistic prediction of soil OM decomposition with moisture • Soil characteristics :  Soil particles and pores architecture  Spatial distribution of soil organic matter and µorganisms 100 µm ©W.Otten,Symbios • Mechanistic models ? – Long & Or 2009, Gharasoo et al. 2012, Resat et al. 2012 • Models with explicit description of soil structure at relevant scales: computer assisted X-ray microtomography – MOSAIC (bacteria) (Monga et al. 2007) – µFUN (fungi) (Falconer et al. 2007, Pajor et al. 2012) – LBios (bacteria) (Vogel et al. 2015) To be accounted for: • Processes:  Need of water for activity, ≠ physiological requirements;  Growth & movement patterns of µorganisms  Diffusion of gases (O2) and solutes (substrates, enzymes)
  9. 9. A mechanistic model accounting for architecture • MOSAIC II (Monga et al. 2007, Ngom et al. 2012) Ψ= - 20cm Voids modeling with Delaunay spheres CT pore space images Spatially structured model: nodes connected Diffusion between nodes Voids filling with water (Laplace) Monga et al. 2014, Biogeosciences Mineralisation kinetics
  10. 10. 3- Interactions between cropping practices, soil moisture and soil respiration
  11. 11. -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 5 10 15 20 25 30 35 40 45 Experiment duration (years ) (a) RelativeSOCstockdifference betweenNTandITplots -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 5 10 15 20 25 30 35 40 45 Experiment duration (years ) (a) RelativeSOCstockdifference betweenNTandITplots -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 5 10 15 20 25 30 35 40 45 (b) RelativeSOCstockdifference betweenNTandITplots -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 5 10 15 20 25 30 35 40 45 (b) RelativeSOCstockdifference betweenNTandITplots Time (years) SoilCstocks(NT-FIT/FIT) C storage in soil under no-tillage • Highly variable effects – Meta-analyses : Angers & Eriksen Hamel, 2008, Luo et al. 2010, Virto et al. 2012 11 Virto et al. 2012, Biogeochemistry Soil C stocks (0-30cm) in no tillage (NT) compared to full inversion tillage (FIT) • Additional soil C storage : depends on climate (moisture) ? -0,4 -0,2 0 0,2 0,4 0,6 0,8 300 400 500 600 700 800 900 stockSOC(NT-FIT/FIT) Mean Annual Precipita on (mm) Blanco Moure et al. 2013 Spain Dimassi et al. 2014, France Dimassi et al. 2014
  12. 12. CO2CO2 water Corg Corg C storage under no tillage • Processes of additional C storage: • Consequences, feedbacks on CO2 emissions: – When implementing no tillage : ↗C storage= f(climate) – When irrigating no tillage systems: ↗CO2 emissions NminNorg Nmin Norg • SOC accumulation in mulch • Better SOC protection in aggregates • Moister and colder conditions • Rapid litter decomposition under moist conditions – Coppens et al. 2007, Kochsiek et al. 2009, Iqbal 2013, Helgason et al. 2015…
  13. 13. Conclusion • Magnitude, timing, sign of climate–carbon cycle feedback will depend on the response of soil carbon to climate • Moisture is a major control of soil C stocks and mineralization • Needs: understand, account for, – Soil characteristics : constituents and structure, up-scaling mechanistic models to compartment based models; – Moisture regime : wetting-drying events, extreme events – Interactions with land use and agricultural practices Thank you for your attention

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