How much carbon can soils hold? | 9am PT, Tues Ap 21, 2026

[Grigory Bronevetsky]

Modeling Talks

How much carbon can soils hold? Katerina Georgiou, Oregon State University Tues, April 21, 2026 | 9am PT Youtube Stream Hi all, The presentation will be via Meet and all questions will be addressed there. If you cannot attend live, the event will be recorded and can be found afterward at https://sites.google.com/modelingtalks.org/entry/how-much-carbon-can-soils-hold More information on previous and future talks: https://sites.google.com/modelingtalks.org/entry/home Abstract: Managing soils to increase organic carbon presents a potential opportunity to mitigate and adapt to global change challenges, while providing numerous co-benefits and ecosystem services. However, soils differ widely in their potential for carbon gains and losses, and advancing knowledge of biophysical limits to carbon accumulation may aid in informing priority regions for management. There is thus increasing interest in assessing whether soils exhibit a maximum capacity for storing organic carbon (i.e., carbon saturation), especially as mineral-associated organic carbon given its presumed greater persistence and the finite nature of reactive minerals in soils. In this seminar, I will summarize my ongoing work on the limits, controls, and vulnerability of mineral-associated organic carbon, and review its representation in ecosystem- to global-scale soil carbon models.  Bio: Katerina Georgiou is an Assistant Professor in Biological & Ecological Engineering at Oregon State University. Her research focuses on understanding and modeling how soil carbon cycling will respond to changes in climate and management, with particular interest in how pore-scale processes modulate emergent ecosystem-scale behavior. Prior to joining OSU, Katerina was a Lawrence Fellow and Staff Scientist at Lawrence Livermore National Lab. She received a Ph.D. in Chemical & Biomolecular Engineering from UC Berkeley, working with the Climate & Ecosystem Sciences Division at Lawrence Berkeley Lab, and was a USDA NIFA Postdoctoral Fellow in Earth System Science at Stanford University.

[Grigory Bronevetsky]

FYI, this talk has been rescheduled to May 19. Thank you!

-Greg Bronevetsky

[Grigory Bronevetsky]

Modeling Talks

How much carbon can soils hold? Katerina Georgiou, Oregon State University

Tues, May 19, 2026 | 9am PT

Youtube Stream Hi all, The presentation will be via Meet and all questions will be addressed there. If you cannot attend live, the event will be recorded and can be found afterward at https://sites.google.com/modelingtalks.org/entry/how-much-carbon-can-soils-hold More information on previous and future talks: https://sites.google.com/modelingtalks.org/entry/home Abstract: Managing soils to increase organic carbon presents a potential opportunity to mitigate and adapt to global change challenges, while providing numerous co-benefits and ecosystem services. However, soils differ widely in their potential for carbon gains and losses, and advancing knowledge of biophysical limits to carbon accumulation may aid in informing priority regions for management. There is thus increasing interest in assessing whether soils exhibit a maximum capacity for storing organic carbon (i.e., carbon saturation), especially as mineral-associated organic carbon given its presumed greater persistence and the finite nature of reactive minerals in soils. In this seminar, I will summarize my ongoing work on the limits, controls, and vulnerability of mineral-associated organic carbon, and review its representation in ecosystem- to global-scale soil carbon models.  Bio: Katerina Georgiou is an Assistant Professor in Biological & Ecological Engineering at Oregon State University. Her research focuses on understanding and modeling how soil carbon cycling will respond to changes in climate and management, with particular interest in how pore-scale processes modulate emergent ecosystem-scale behavior. Prior to joining OSU, Katerina was a Lawrence Fellow and Staff Scientist at Lawrence Livermore National Lab. She received a Ph.D. in Chemical & Biomolecular Engineering from UC Berkeley, working with the Climate & Ecosystem Sciences Division at Lawrence Berkeley Lab, and was a USDA NIFA Postdoctoral Fellow in Earth System Science at Stanford University.

[Grigory Bronevetsky]

Video Recording: https://youtube.com/live/zPNyru_z91s

Slides: https://drive.google.com/file/d/1qX5m65845Zq5_iLUt6zuCIGNpKIysMxZ/view?usp=sharing

Summary:

• Focus: global-scale assessment of soils

  • Soils 

    • Store 2500 GTons of C in top 2m

    • CO2 emissions 60GTons/year

  • Trees absorb 750 GTons/year

  • Small changes to soil/plant dynamics have huge impact on global climate

    • Geochemistry

    • Microorganisms

  • Soil carbon dynamics:

    • Deposited by plants from above

    • Captured on minerals or bodies of microbes, or emitted

  • However, dynamics of soils are highly uncertain due to complex dynamics and limited data availability

• Research landscape:

  • Microbial controls on decomposition

  • Geochemical controls

  • Representation of soils in Earth System Models

  • Goal: inform policy and management

  • Combines: lab&field experiments, data analysis and modeling

  • Scales from microns to the globe

• Global soil dynamics

  • 110GTons lost due to anthropogenic land use

  • Significant interest in storing it back

  • Major improvements to agricultural productivity and stability due to increasing soil carbon 

  • Are the limits on carbon storage effectiveness, how does this inform policy?

• Intervention dynamics:

  • Increase biomass inputs into soils

  • Decrease vectors of C leakage from soils

    • Promote storage in soils

    • Protect soils from leakage drivers (e.g. wind erosion)

  • Key carbon pools:

    • POC: Particulate organic (larger sized carbon fragments) (~25% of global soil carbon)

    • MAOC: Mineral associated organic carbon (smaller particles attached to minerals) (~45% of global soil carbon)

      • Hard for microbes to digest

      • Good for long-term carbon storage

      • Finite mineral surface area means that this pool can saturate

• MAOC capacity

  • As C inputs rise, 

    • MAOC should saturate but stay stable

      • MOCmax: maximum C capacity of MAOC in a given soil’s texture and mineralogy

        • Sandy soils (bigger mineral particles): less surface area, so lower MOCmax

        • Clay soils (smaller mineral particles): more surface area, so higher MOCmax

        • Can intervene to add biochar or clay content to increase MOCmax

      • Rate of C input depends on above ground ecology and climate

    • POC should rise indefinitely but more vulnerable to release

  • Interventions can affect these dynamics

    • Tillage causes C release, avoiding it can increase carbon storage

    • Addition of biochar can increase MOCmax

  • MOCmax is hard to estimate

    • Maximum observed C capacity in the field is a lower bound on the true value

    • Collect data on SOC vs MAOC to see where it plateaus

    • Challenge: the relationship is controlled by many other factors

      • Real data shows a significant variability in MAOC for the same soil clay/silt content and SOC

      • Part of of the noise is soils where MAOC has not been reached

      • The maximum of these measurements for a given soil clay/silt content should be MOCmax

      • Estimating the max metric requires a lot of data

      • 1100 global observations of MAOC vs SOC

      • Need to estimate reasons for why MAOC is not saturated and how its varies due to management and depth

        • Saturation is higher in un-managed land (grasslands/forests)

        • Also higher in forests (~50%) than grasslands (45%), which are higher than cropland (~25%)

        • Lower saturation in deeper 

• Geospatial analysis of MAOC shows significant regional patterns to

  • MAOC vs POC

  • MOCmax

• MAOC and POC in process-based models

  • MOCmax is a major parameter in most soil models

  • In the past this parameter was constrained by lab experiments, which significantly underestimate it because they are done in 

    • sterile soils (no fungi and bacteria) and 

    • homogeneous mineral types

  • Mis-estimated MOCmax points to incorrect carbon storage priorities (need to prioritize soils further away from saturation)

  • Analysis of 103 soil profiles shows that more carbon was accrued in soils that were further away from saturation

  • In addition to physical constraints, there are also economic and political considerations

• How will soils respond to warming?

  • Network of warming experiments across the world (limited due to cost)

  • Climate gradient analysis: similar soils at different temperatures (space for time substitution may have limitations for making inferences about dynamics)

  • ~9k WoSIS profiles

    • Estimate proportional decline in soil C for every 10deg C of temp increase

    • Low clay: high temp sensitivity

    • High clay: low temp sensitivity

    • POC has a much higher temp sensitivity than MAOC 

  • Soil models must capture this sensitivity

    • Models are pretty good at estimating total soil C

    • Estimates of different pools are much more variable

    • Models have too much carbon in fast-cycling pools and too little in slow cycling pools, which causes Earth System models to cycle carbon too fast

    • Unclear how much of the uncertainty comes from poor estimates of how much C comes into soils from aboveground