Bridging 20Â years of soil organic matter frameworks: Empirical support, model representation, and next steps

This shift in understanding has been driven, in part, by influential conceptual frameworks which put forth hypotheses about SOM dynamics. Here, we summarize several focal conceptual frameworks and derive from them six controls related to SOM formation, (de)stabilization, and loss.

These include: (a) physical inaccessibility; (b) organo-mineral and -metal stabilization; (c) biodegradability of plant inputs; (d) abiotic environmental factors; (e) biochemical reactivity and diversity; and (f) microbial physiology and morphology. We then review the empirical evidence for these controls, their model representation, and outstanding knowledge gaps. We find relatively strong empirical support and model representation of abiotic environmental factors but disparities between data and models for biochemical reactivity and diversity, organo-mineral and -metal stabilization, and biodegradability of plant inputs, particularly with respect to SOM destabilization for the latter two controls.