Managing soils to increase organic carbon storage 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 award lecture, I will summarize my ongoing work on the controls and limits of mineral-associated organic carbon and its representation in process-based soil carbon models. First, I will provide an overview of the concept of soil carbon saturation at both micro- and macro-scales, address common misconceptions, and present a quantification of the maximum observed capacity of mineral-associated organic carbon globally. Next, I will show that organo-mineral associations can moderate the vulnerability of a soil to lose carbon under climate or land-use change. Finally, I will review the landscape of current ecosystem- to global-scale soil carbon models and highlight next steps for improving their structure and parameterizations in this context.

How to cite: Georgiou, K.: Limits, controls, and vulnerability of mineral-associated soil organic carbon, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14372, https://doi.org/10.5194/egusphere-egu25-14372, 2025.

About 30% of our soils are degraded, mostly due to unsustainable land use. These soils took centuries or millennia to form. Are they lost for generations, or can they be regenerated quickly? And how can these options cope with climate change?

The first part of the talk explains how long-term agricultural use degrades soils and how their properties can recover through management changes. It will discuss options for quickly regenerating such soils for agriculture and the challenges involved. History offers valuable insights: indigenous peoples in the tropics and early agricultural societies improved soils using biochar and organic residues with remarkable results. However, today these methods carry risks, such as yield reductions in temperate zones or the spread of antibiotic resistance from intensive organic fertilisation. The second part of the talk explores, therefore, the balance between opportunities and risks in sustainable soil use, concluding with recent findings on how subsoils might help resolve this conflict.

How to cite: Amelung, W.: Ways out of the global soil crisis: opportunities and risks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3696, https://doi.org/10.5194/egusphere-egu25-3696, 2025.