Soil organic carbon under lockdown: Fresh plant litter as the nucleus for persistent carbon (original) (raw)
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Particulate organic matter as a functional soil component for persistent soil organic carbon
Nature Communications, 2021
The largest terrestrial organic carbon pool, carbon in soils, is regulated by an intricate connection between plant carbon inputs, microbial activity, and the soil matrix. This is manifested by how microorganisms, the key players in transforming plant-derived carbon into soil organic carbon, are controlled by the physical arrangement of organic and inorganic soil particles. Here we conduct an incubation of isotopically labelled litter to study effects of soil structure on the fate of litter-derived organic matter. While microbial activity and fungal growth is enhanced in the coarser-textured soil, we show that occlusion of organic matter into aggregates and formation of organo-mineral associations occur concurrently on fresh litter surfaces regardless of soil structure. These two mechanisms—the two most prominent processes contributing to the persistence of organic matter—occur directly at plant–soil interfaces, where surfaces of litter constitute a nucleus in the build-up of soil c...
Calcium promotes persistent soil organic matter by altering microbial transformation of plant litter
Calcium (Ca) can increase soil organic carbon (SOC) persistence by mediating physico-chemical interactions between organic compounds and minerals. Yet, Ca is also crucial for microbial adhesion, potentially affecting colonization of plant and mineral surfaces. The relative importance of Ca as a mediator of microbe-mineral-organic matter interactions and resulting SOC transformation has hereto been overlooked. We incubated 44Ca labeled soils with 13C15N labeled leaf litter to study the effects of Ca on microbial transformation of plant litter and formation of mineral associated organic matter. Ca additions promoted hyphae-forming bacteria, which often specialize in colonizing surfaces, increased incorporation of plant litter into microbial biomass by 20% and carbon use efficiency by 40%, and reduced cumulative CO2 emission by 5%, while promoting associations between minerals and microbial byproducts of plant litter. These findings expand the role of Ca in SOC persistence from solely ...
Nature communications, 2017
Climatic, atmospheric, and land-use changes all have the potential to alter soil microbial activity, mediated by changes in plant inputs. Many microbial models of soil organic carbon (SOC) decomposition have been proposed recently to advance prediction of climate and carbon (C) feedbacks. Most of these models, however, exhibit unrealistic oscillatory behavior and SOC insensitivity to long-term changes in C inputs. Here we diagnose the source of these problems in four archetypal models and propose a density-dependent formulation of microbial turnover, motivated by community-level interactions, that limits population sizes and reduces oscillations. We compare model predictions to 24 long-term C-input field manipulations and identify key benchmarks. The proposed formulation reproduces soil C responses to long-term C-input changes and implies greater SOC storage associated with CO2-fertilization-driven increases in C inputs over the coming century compared to recent microbial models. Th...