Formation of mineral‐associated organic matter in temperate soils is primarily controlled by mineral type and modified by land use and management intensity

Abstract

Formation of mineral‐associated organic matter (MAOM) supports the accumulation and stabilization of carbon (C) in soil, and thus, is a key factor in the global C cycle. Little is known about the interplay of mineral type, land use and management intensity in MAOM formation, especially on subdecadal time scales. We exposed mineral containers with goethite or illite, the most abundant iron oxide and phyllosilicate clay in temperate soils, for 5 years in topsoils of 150 forest and 150 grassland sites in three regions across Germany. Results show that irrespective of land use and management intensity, more C accumulated on goethite than illite (on average 0.23 ± 0.10 and 0.06 ± 0.03 mg m−2 mineral surface respectively). Carbon accumulation across regions was consistently higher in coniferous forests than in deciduous forests and grasslands. Structural equation models further showed that thinning and harvesting reduced MAOM formation in forests. Formation of MAOM in grasslands was not affected by grazing. Fertilization had opposite effects on MAOM formation, with the positive effect being mediated by enhanced plant productivity and the negative effect by reduced plant species richness. This highlights the caveat of applying fertilizers as a strategy to increase soil C stocks in temperate grasslands. Overall, we demonstrate that the rate and amount of MAOM formation in soil is primarily driven by mineral type, and can be modulated by land use and management intensity even on subdecadal time scales. Our results suggest that temperate soils dominated by oxides have a higher capacity to accumulate and store C than those dominated by phyllosilicate clays, even under circumneutral pH conditions. Therefore, adopting land use and management practices that increase C inputs into oxide‐rich soils that are under their capacity to store C may offer great potential to enhance near‐term soil C sequestration.

Carbon Fate, Iron Dissolution, and Molecular Characterization of Dissolved Organic Matter in Thawed Yedoma Permafrost under Varying Redox Conditions

“…These findings confirm the low pedogenetic development of the parent material (i.e., loess-deposits) . These properties did not support an extensive surface area for physicochemical protection (i.e., organo-mineral association, coprecipitation, and occlusion inside stable soil aggregates of organic matter) from degradation which is better provided by Al- and Fe-oxyhydroxides than by phyllosilicates. , Such mechanisms are the primary drivers for C stabilization in developed soils. − …”

“…17 These properties did not support an extensive surface area for physicochemical protection (i.e., organo-mineral association, coprecipitation, and occlusion inside stable soil aggregates of organic matter) from degradation which is better provided by Al-and Feoxyhydroxides than by phyllosilicates. 36,78 Such mechanisms are the primary drivers for C stabilization in developed soils. 79−88 Sowers et al, 22 using microfocused synchrotron-based XRF, showed a correlation between Fe and C in the sample investigated in this research, suggesting colocalization and potential interaction.…”

Effect of Grasslands Fertilisation on Soil Organic Matter Quality and Nutrients Status

“…As a result, the soil becomes more susceptible to various forms of degradation, including acidification, wind and water erosion, low water retention, and pedocompaction. Bramble et al (2024), Karabcová et al (2015), and Pospíšilová et al (2011) discussed the opposite effect of fertiliser on SOM, where fertiliser positively increases plant production but reduces species diversity in grassland. Simiraly to us, they demonstrated that SOM accumulation in temperate grasslands is affected by management practices and fertilisation.…”

Tannins and Climate Change: Are Tannins Able To Stabilize Carbon in the Soil?

“…Organic C in the soil is derived mainly from plant and animal residues, which enter the soil and pass through soil microorganisms before transformation into SOC . Soil microorganisms have a dual role in controlling SOC: catabolic, as they decompose organic compounds, and anabolic, as they stabilize C formation and thus more stable SOC. , The size of SOC has undergone dynamic changes driven by climatic (temperature and moisture) and soil (pH, texture, and minerals) conditions, soil fauna, and complex plant–soil–microbial interactions . Especially in forested ecosystems, plant symbionts and mycorrhizal fungi (MF), fueled by plant C allocation of recent photosynthates, may significantly contribute to the soil organic matter (SOM) decomposition and mining for N from soil .…”