Association of Organic Carbon With Reactive Iron Oxides Driven by Soil pH at the Global Scale

Ye, Chenglong; Huang, Wenjuan; Hall, Steven J.; Hu, Shuijin

doi:10.1029/2021gb007128

Cited by 47 publications

(15 citation statements)

References 55 publications

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“…Despite soil pH decreased in lower SOM sites, significant increases in net positive charge of Fe oxides or dissolution of Fe(III) were unlikely to occur since all soil pH were above 5.5 (Ye et al, 2022). Thus, the decreased pH might not promote the accumulation of OM-Fe in this study.…”

Section: Oxygen Availability Mediates the Quality Of Dom By Promoting...mentioning

confidence: 71%

“…In contrast to our expectations, the content of OM‐Fe significantly increased with the decreases in the contents of SOM and MAOM (Figure 1). Previous research has attributed OM‐Fe accumulation to the decrease in soil pH (Ye et al, 2022), or changes in Fe valence and mineralogical characteristic (Duan et al, 2020). Here, both the regression and random forest analyses evidenced the dominant role of Fe valence in promoting the formation of OM‐Fe (Figure S10).…”

Section: Discussionmentioning

confidence: 99%

“…Here, both the regression and random forest analyses evidenced the dominant role of Fe valence in promoting the formation of OM‐Fe (Figure S10). Despite soil pH decreased in lower SOM sites, significant increases in net positive charge of Fe oxides or dissolution of Fe(III) were unlikely to occur since all soil pH were above 5.5 (Ye et al, 2022). Thus, the decreased pH might not promote the accumulation of OM‐Fe in this study.…”

Section: Discussionmentioning

confidence: 99%

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Oxygen availability regulates the quality of soil dissolved organic matter by mediating microbial metabolism and iron oxidation

Chen

et al. 2022

Global Change Biology

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Dissolved organic matter (DOM) plays a vital role in biogeochemical processes and in determining the responses of soil organic matter (SOM) to global change. Although the quantity of soil DOM has been inventoried across diverse spatio-temporal scales, the underlying mechanisms accounting for variability in DOM dynamics remain unclear especially in upland ecosystems. Here, a gradient of SOM storage across 12 croplands in northeast China was used to understand links between DOM dynamics, microbial metabolism, and abiotic conditions. We assessed the composition, biodegradability, and key biodegradable components of DOM. In addition, SOM and mineral-associated organic matter (MAOM) composition, soil enzyme activities, oxygen availability, soil texture, and iron (Fe), Fe-bound organic matter, and nutrient concentrations were quantified to clarify the drivers of DOM quality (composition and biodegradability). The proportion of biodegradable DOM increased exponentially with decreasing initial DOM concentration due to larger fractions of depolymerized DOM that was rich in small-molecular phenols and proteinaceous components.Unexpectedly, the composition of DOM was decoupled from that of SOM or MAOM, but significantly related to enzymatic properties. These results indicate that microbial metabolism exhibited a dominant role in DOM generation. As DOM concentration declined, increased soil oxygen availability regulated DOM composition and enhanced its biodegradability mainly through mediating microbial metabolism and Fe oxidation.The oxygen-induced oxidation of Fe(II) to Fe(III) removed complex DOM compounds with large molecular weight. Moreover, increased oxygen availability stimulated oxidase-catalyzed depolymerization of aromatic substances, and promoted production of protein-like DOM components due to lower enzymatic C/N acquisition ratio.As global changes in temperature and moisture will have large impacts on soil oxygen availability, the role of oxygen in regulating DOM dynamics highlights the importance of integrating soil oxygen supply with microbial metabolism and Fe redox status to improve model predictions of soil carbon under climate change.

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Section: Oxygen Availability Mediates the Quality Of Dom By Promoting...mentioning

confidence: 71%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Oxygen availability regulates the quality of soil dissolved organic matter by mediating microbial metabolism and iron oxidation

Chen

et al. 2022

Global Change Biology

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“…Projected increases in soil acidification associated with nitrogen fertilization (Tian & Niu, 2015) and acid deposition (Guo et al, 2010), may also impact the redox cycling of Fe and preservation of OC. Ye et al (2022) found that pH is likely the key predictor of OC-Fe R abundance in terrestrial soils, suggesting any future decreases in soil pH may increase OC-Fe R .…”

Section: How Will the Oc-fer Sink Change Due To Anthropogenic Climate...mentioning

confidence: 96%

Organic Carbon Burial With Reactive Iron Across Global Environments

Longman

Faust

Bryce

et al. 2022

Global Biogeochemical Cycles

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Preservation of organic carbon (OC) in marine and terrestrial deposits is enhanced by bonding with reactive iron (FeR). Association of OC with FeR (OC‐FeR) provides physical protection and hinders microbiological degradation. Roughly 20% of all OC stored in unconsolidated marine sediments and 40% of all OC present in Quaternary terrestrial deposits is preserved as OC‐FeR, but this value varies from 10% to 80% across global depositional environments. Here, we provide a new assessment of global OC‐FeR burial rates in both marine and terrestrial environments, using published estimates of OC associated with FeR, carbon burial, and probabilistic modeling. We estimate the marine OC‐FeR sink between 31 and 70 Mt C yr−1 (average 52 Mt C yr−1), and the terrestrial OC‐FeR sink at between 146 and 917 Mt C yr−1 (average 446 Mt C yr−1). In marine environments, continental shelves (average 17 Mt C yr−1) and deltaic/estuarine environments (average 11 Mg C yr−1) are the primary settings of OC‐FeR burial. On land, croplands (279 Mt C yr−1) and grasslands (121 Mt C yr−1) dominate the OC‐FeR burial budget. Changes in the Earth system through geological time impact the OC‐FeR pools, particularly in marine settings. For example, periods of intense explosive volcanism may lead to increased net OC‐FeR burial in marine sediments. Our work highlights the importance of OC‐FeR in marine carbon burial and demonstrates how OC‐FeR burial rates may be an order of magnitude greater in terrestrial environments, but here OC‐FeR stocks are most sensitive to the anthropogenic impacts of climatic change.

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“…Under reduction conditions, iron exists as dissolved Fe 2+ and has a strong mobility, while the protection of organic matter can promote the stability of iron complexes; under oxidation conditions, iron can exist as Fe 3+ and is easily formed to insoluble iron (hydr-)oxides, which would decrease iron migration and transformation in sediments (Melton et al, 2014;Jiang et al, 2019). The pH can affect the redox status, microbial activity and soil adsorption capacity, regulating the transformation and availability of iron in wetland soils (Johnston et al, 2014;Ye et al, 2022). Soil organic matter dynamics is closely related to the biogeochemical cycles of iron, and the reduction rate of Fe(III) will be greatly improved in tidal flat sediments rich in organic matter (Santos-Echeandia et al, 2010;Lalonde et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Spatial distribution of soil iron across different plant communities along a hydrological gradient in the Yellow River Estuary wetland

Sun

Qin

et al. 2022

Front. Ecol. Evol.

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Iron is an important element and its biogeochemical processes are vital to the matter and energy cycles of wetland ecosystems. Hydrology greatly controls characteristics of soil property and plant community in wetlands, which can regulate the behavior of iron and its oxides. However, it remains unclear how the spatial distribution of iron and its forms in estuarine wetlands responses to hydrological conditions. Five typical plant communities along a naturally hydrological gradient in the Yellow River Estuary wetland, including Phragmites australis in freshwater marsh (FPA), Phragmites australis in salt marsh (SPA), Tamarix chinensis in salt marsh (TC), Suaeda salsa in salt marsh (SS) and Spartina alterniflora in salt marsh (SA), as sites to collect soil samples. The total iron (FeT) and three iron oxides (complexed iron, Fep; amorphous iron, Feo; free iron, Fed) in samples were determined to clarify the spatial distribution of iron and explore its impact factors. The mean contents of FeT, Fep, Feo and Fed were 28079.4, 152.0, 617.2 and 8285.3 mg⋅kg–1 of soil at 0–40 cm depth in the different sites, respectively. The means were significantly different across communities along the hydrological gradient, with the higher values for SA on the upper intertidal zone and for SPA on the lower intertidal zone, respectively. Iron and its forms were positively correlated with the total organic carbon (TOC), dissolved organic carbon (DOC), total nitrogen (TN) and clay, and negatively correlated with electrical conductivity (EC). The indexes of iron oxides (Fep/Fed, Feo/Fed and Fed/FeT) were also different across communities, with a higher value for SA, which were positively correlated with soil water content (WC) and TOC. The results indicate that a variety of plant community and soil property derived from the difference of hydrology might result in a spatial heterogeneity of iron in estuarine wetlands.

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Association of Organic Carbon With Reactive Iron Oxides Driven by Soil pH at the Global Scale

Cited by 47 publications

References 55 publications

Oxygen availability regulates the quality of soil dissolved organic matter by mediating microbial metabolism and iron oxidation

Oxygen availability regulates the quality of soil dissolved organic matter by mediating microbial metabolism and iron oxidation

Organic Carbon Burial With Reactive Iron Across Global Environments

Spatial distribution of soil iron across different plant communities along a hydrological gradient in the Yellow River Estuary wetland

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