Clay Minerals as the Key to the Sequestration of Carbon in Soils

Churchman, G. Jock; Singh, Mandeep; Schapel, Amanda; Sarkar, Binoy; Bolan, Nanthi

doi:10.1007/s42860-020-00071-z

Cited by 62 publications

(23 citation statements)

References 80 publications

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“…Allophane is an Al-rich nanocrystalline aluminosilicate, formula (1–2)SiO 2 ·Al 2 O 3 ·(2–3)·H 2 O, that comprises hollow spherules ~ 3.5 to 5 nm in diameter. It has a very high specific surface area (up to ~ 1200 m 2 g −1 ) 6 – 8 , enabling allophanic soils derived from tephra (volcanic ash), including Andisols, to adsorb much SOM (including via strong Al-SOM bonding) and to help stablize SOC 9 , 10 . The similar but Fe-rich nanocrystalline ferrihydrite, formula Fe 5 HO 8 ∙4H 2 O, is also common in Andisols but typically in considerably smaller quantities than allophane unless on basaltic parent tephras 2 , 9 .…”

Section: Introductionmentioning

confidence: 99%

Characterizing porous microaggregates and soil organic matter sequestered in allophanic paleosols on Holocene tephras using synchrotron-based X-ray microscopy and spectroscopy

Huang

Lowe

Churchman

et al. 2021

Sci Rep

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Allophanic tephra-derived soils can sequester sizable quantities of soil organic matter (SOM). However, no studies have visualized the fine internal porous structure of allophanic soil microaggregates, nor studied the carbon structure preserved in such soils or paleosols. We used synchrotron radiation-based transmission X-ray microscopy (TXM) to perform 3D-tomography of the internal porous structure of dominantly allophanic soil microaggregates, and carbon near-edge X-ray absorption fine-structure (C NEXAFS) spectroscopy to characterize SOM in ≤ 12,000-year-old tephra-derived allophane-rich (with minor ferrihydrite) paleosols. The TXM tomography showed a vast network of internal, tortuous nano-pores within an allophanic microaggregate comprising nanoaggregates. SOM in the allophanic paleosols at four sites was dominated by carboxylic/carbonyl functional groups with subordinate quinonic, aromatic, and aliphatic groups. All samples exhibited similar compositions despite differences between the sites. That the SOM does not comprise specific types of functional groups through time implies that the functional groups are relict. The SOM originated at the land/soil surface: ongoing tephra deposition (intermittently or abruptly) then caused the land-surface to rise so that the once-surface horizons were buried more deeply and hence became increasingly isolated from inputs by the surficial/modern organic cycle. The presence of quinonic carbon, from biological processes but vulnerable to oxygen and light, indicates the exceptional protection of SOM and bio-signals in allophanic paleosols, attributable both to the porous allophane (with ferrihydrite) aggregates that occlude the relict SOM from degradation, and to rapid burial by successive tephra-fallout, as well as strong Al-organic chemical bonding. TXM and C NEXAFS spectroscopy help to unravel the fine structure of soils and SOM and are of great potential for soil science studies.

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Section: Introductionmentioning

confidence: 99%

Characterizing porous microaggregates and soil organic matter sequestered in allophanic paleosols on Holocene tephras using synchrotron-based X-ray microscopy and spectroscopy

Huang

Lowe

Churchman

et al. 2021

Sci Rep

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“…Transfer by DOC decreased substantially after year 10, from 5.9 g C m -2 y -1 in the 10 th year to 0.09 g C m -2 y -1 at the 26 th year due to a reduction in CWD decomposition. The DOC incorporated into soils can be absorbed or aggregated and therefore maintained in soils for a longer time [55,56]. These simulation results provide context for suggesting the magnitude of the transfers of C from CWD into the soil.…”

Section: Plos Onementioning

confidence: 78%

Coarse Woody Debris Decomposition Assessment Tool: Model validation and application

et al. 2021

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Coarse woody debris (CWD) is a significant component of the forest biomass pool; hence a model is warranted to predict CWD decomposition and its role in forest carbon (C) and nutrient cycling under varying management and climatic conditions. A process-based model, CWDDAT (Coarse Woody Debris Decomposition Assessment Tool) was calibrated and validated using data from the FACE (Free Air Carbon Dioxide Enrichment) Wood Decomposition Experiment utilizing pine (Pinus taeda), aspen (Populous tremuloides) and birch (Betula papyrifera) on nine Experimental Forests (EF) covering a range of climate, hydrology, and soil conditions across the continental USA. The model predictions were evaluated against measured FACE log mass loss over 6 years. Four widely applied metrics of model performance demonstrated that the CWDDAT model can accurately predict CWD decomposition. The R2 (squared Pearson’s correlation coefficient) between the simulation and measurement was 0.80 for the model calibration and 0.82 for the model validation (P<0.01). The predicted mean mass loss from all logs was 5.4% lower than the measured mass loss and 1.4% lower than the calculated loss. The model was also used to assess the decomposition of mixed pine-hardwood CWD produced by Hurricane Hugo in 1989 on the Santee Experimental Forest in South Carolina, USA. The simulation reflected rapid CWD decomposition of the forest in this subtropical setting. The predicted dissolved organic carbon (DOC) derived from the CWD decomposition and incorporated into the mineral soil averaged 1.01 g C m-2 y-1 over the 30 years. The main agents for CWD mass loss were fungi (72.0%) and termites (24.5%), the remainder was attributed to a mix of other wood decomposers. These findings demonstrate the applicability of CWDDAT for large-scale assessments of CWD dynamics, and fine-scale considerations regarding the fate of CWD carbon.

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“…The test site had a clay content of 18%. This clay content promotes long-term carbon sequestration by stabilization of SOC against decomposition [88]. SOC sequestration rates of 1.44-2.27 Mg ha −1 yr −1 for the top 30 cm soil layer have been reported for two Salix varieties during a 6-year study period in the UK [81].…”

Section: Discussionmentioning

confidence: 94%

Soil Carbon Modelling in Salix Biomass Plantations: Variety Determines Carbon Sequestration and Climate Impacts

Kalita

Potter

Weih

et al. 2021

Forests

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Short-rotation coppice (SRC) Salix plantations have the potential to provide fast-growing biomass feedstock with significant soil and climate mitigation benefits. Salix varieties exhibit significant variation in their physiological traits, growth patterns and soil ecology—but the effects of these variations have rarely been studied from a systems perspective. This study analyses the influence of variety on soil organic carbon (SOC) dynamics and climate impacts from Salix cultivation for heat production for a Swedish site with specific conditions. Soil carbon modelling was combined with a life cycle assessment (LCA) approach to quantify SOC sequestration and climate impacts over a 50-year period. The analysis used data from a Swedish field trial of six Salix varieties grown under fertilized and unfertilized treatments on Vertic Cambisols during 2001–2018. The Salix systems were compared with a reference case where heat is produced from natural gas and green fallow was the land use alternative. Climate impacts were determined using time-dependent LCA methodology—on a land-use (per hectare) and delivered energy unit (per MJheat) basis. All Salix varieties and treatments increased SOC, but the magnitude depended on the variety. Fertilization led to lower carbon sequestration than the equivalent unfertilized case. There was no clear relationship between biomass yield and SOC increase. In comparison with reference cases, all Salix varieties had significant potential for climate change mitigation. From a land-use perspective, high yield was the most important determining factor, followed by SOC sequestration, therefore high-yielding fertilized varieties such as ‘Tordis’, ‘Tora’ and ‘Björn’ performed best. On an energy-delivered basis, SOC sequestration potential was the determining factor for the climate change mitigation effect, with unfertilized ‘Jorr’ and ‘Loden’ outperforming the other varieties. These results show that Salix variety has a strong influence on SOC sequestration potential, biomass yield, growth pattern, response to fertilization and, ultimately, climate impact.

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Clay Minerals as the Key to the Sequestration of Carbon in Soils

Cited by 62 publications

References 80 publications

Characterizing porous microaggregates and soil organic matter sequestered in allophanic paleosols on Holocene tephras using synchrotron-based X-ray microscopy and spectroscopy

Characterizing porous microaggregates and soil organic matter sequestered in allophanic paleosols on Holocene tephras using synchrotron-based X-ray microscopy and spectroscopy

Coarse Woody Debris Decomposition Assessment Tool: Model validation and application

Soil Carbon Modelling in Salix Biomass Plantations: Variety Determines Carbon Sequestration and Climate Impacts

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