Posted by Design Studio
26 September 2025
Challenge 2: Soil Carbon
https://www.nature.com/articles/s43247-025-02681-8
Revisiting the Stability of Mineral-Associated Organic Matter (MAOM)
Traditionally, mineral-associated organic matter (MAOM) has been viewed as a large (~60%) and persistent component of soil organic matter, with turnover times spanning centuries to millennia. However, growing evidence suggests that MAOM is a heterogeneous mixture, with a substantial fraction cycling on much shorter timescales, from minutes to years.
MAOM Is Not a Single Pool
Rather than a uniform, inert reservoir, MAOM encompasses multiple sub-pools with varying chemical properties, binding strengths, and turnover rates. Its dynamics are governed by interactions between organic compounds and mineral surfaces, as well as by external destabilizing forces such as microbial activity, land use, and climate change.
Fast-Cycling MAOM: An Overlooked but Active Pool
The fast-cycling fraction of MAOM is bioavailable, exchangeable, and contributes actively to carbon (C) and nitrogen (N) fluxes. Although smaller in size, this fraction is highly responsive to environmental and management changes.
Implications for Soil Management and Modeling
Recognizing the dynamic nature of MAOM challenges long-standing assumptions in soil biogeochemistry and Earth system models. Incorporating fast-cycling MAOM into models could improve predictions of soil C and N dynamics under shifting climate and land-use regimes.
Advancing Measurement and Conceptual Frameworks
Current methodologies often fall short in isolating and quantifying fast-cycling MAOM. New approaches are needed to characterize its size, behavior, and ecological role. Doing so will not only improve mechanistic understanding but also inform targeted land management strategies that balance C sequestration with nutrient provisioning.
Conceptual figure illustrating the controls on MAOM chemical heterogeneity and three known drivers of MAOM destabilization.
