Redox Fluctuations Control the Coupled Cycling of Iron and Carbon in Tropical Forest Soils

Environmental Science & Technology, Год журнала: 2018, Номер 52(24), С. 14129 - 14139

Опубликована: Ноя. 19, 2018

Oscillating redox conditions are a common feature of humid tropical forest soils, driven by an ample supply and dynamics reductants, high moisture, microbial oxygen consumption, finely textured clays that limit diffusion. However, the net result variable soil regimes on iron (Fe) mineral associated carbon (C) forms fluxes is poorly understood in soils. Using 44-day incubation experiment with soils from Puerto Rico, we examined patterns Fe C transformations under four regimes: static anoxic, “flux 4-day” (4d oxic, 4d anoxic), 8-day” (8d anoxic) oxic. Prolonged anoxia promoted reductive dissolution Fe-oxides, led to increase soluble Fe(II) amorphous oxide pools. Preferential less-crystalline pool was evident immediately following shift bulk status (oxic coincided increased dissolved organic C, presumably due acidification or direct release matter (OM) dissolving Fe(III) phases. The average nominal oxidation state water-soluble lowest persistent anoxic conditions, suggesting more reduced compounds were metabolically unavailable for consumption reducing conditions. Anoxic had H/C values (and similar lignin-like compounds) whereas oxic higher O/C values, akin tannin- cellulose-like components. Cumulative respiration derived native highest These results show how minerals Fe–OM interactions highly sensitive effects. Shifting availability rapidly impacted exchanges between mineral-sorbed aqueous pools, implying periodicity low-redox events may control fate wet

Язык: Английский

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Physical soil architectural traits are functionally linked to carbon decomposition and bacterial diversity

Scientific Reports, Год журнала: 2016, Номер 6(1)

Опубликована: Сен. 12, 2016

Aggregates play a key role in protecting soil organic carbon (SOC) from microbial decomposition. The objectives of this study were to investigate the influence pore geometry on decomposition rate and bacterial diversity both macro- (250-2000 μm) micro-aggregates (53-250 using field samples. Four sites contrasting land use Alfisols (i.e. native pasture, crop/pasture rotation, woodland) investigated. 3D Pore macro-aggregates examined by X-ray computed tomography (μCT). occluded particulate (oPOC) aggregates was measured size density fractionation methods. Micro-aggregates had 54% less μCT observed porosity but 64% more oPOC compared with macro-aggregates. In addition, connectivity lower than Despite micro-aggregates, constant (Ksoc) similar aggregate ranges. Structural equation modelling showed strong positive relationship concentration aggregates. We these findings propose conceptual model that illustrates dynamic links between substrate, diversity, suggests structural explanation for differences across sizes.

Язык: Английский

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Widespread global peatland establishment and persistence over the last 130,000 y

Proceedings of the National Academy of Sciences, Год журнала: 2019, Номер 116(11), С. 4822 - 4827

Опубликована: Фев. 25, 2019

Glacial−interglacial variations in CO 2 and methane polar ice cores have been attributed, part, to changes global wetland extent, but the distribution before Last Glacial Maximum (LGM, 21 ka 18 ka) remains virtually unknown. We present a study of peatland extent carbon (C) stocks through last glacial cycle (130 present) using newly compiled database 1,063 detailed stratigraphic records peat deposits buried by mineral sediments, as well model. Quantitative agreement between modeling observations shows extensive accumulation LGM northern latitudes (>40°N), particularly during warmer periods including interglacial 116 ka, MIS 5e) interstadial (57 29 3). During cooling advance permafrost formation, burial peatlands glaciers sediments decreased active thickness, modeled C 70 90% from times. Tropical show little temporal variation throughout period. While increased peats was correlated with periods, tropical predominately driven sea level regional hydrology. Peat represents mechanism for long-term terrestrial storage Earth system. These results that accumulate significant times, indicating their potential sequestration warming Anthropocene.

Язык: Английский

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Redox controls on arsenic enrichment and release from aquifer sediments in central Yangtze River Basin

Geochimica et Cosmochimica Acta, Год журнала: 2017, Номер 204, С. 104 - 119

Опубликована: Янв. 30, 2017

Язык: Английский

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Linking 3D Soil Structure and Plant-Microbe-Soil Carbon Transfer in the Rhizosphere

Frontiers in Environmental Science, Год журнала: 2018, Номер 6

Опубликована: Фев. 9, 2018

Plant roots are major transmitters of atmospheric carbon into soil. The rhizosphere, the soil volume around living influenced by root activities, represents hotspots for organic inputs, microbial activity, and turnover. Rhizosphere processes remain poorly understood observation key mechanisms transfer protection in intact rhizosphere microenvironments challenging. We deciphered fate photosynthesis-derived (OC) wheat combining stable isotope labeling at field scale with high-resolution 3D-imaging. used nano-scale secondary ion mass spectrometry focus beam-scanning electron microscopy to generate insights nanometer scale. In immature roots, circulated through apoplastic pathway, via cell walls, from stele cortex. was transferred substantial communuties, mainly represented bacteria surrounding peripheral cells. Iron oxides formed bridges between bigger mineral particles, such as quartz, surrounded microaggregates close surface. Some were also intimately associated fungal hyphae Based on these results, we propose a conceptual model depicting biogeochemical interfaces forefront growing roots. observed complex interplays vectors (roots, fungi, bacteria), transferring plant-derived OC root-free stabilizing agents (iron oxides, microorganism products), potentially protecting within rhizosphere.

Язык: Английский

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