Evidence of aggregate hierarchy at micro- to submicron scales in an allophanic Andisol

Asano, Masaharu; Wagai, Rota

doi:10.1016/j.geoderma.2013.10.005

Cited by 148 publications

(121 citation statements)

References 65 publications

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“…Asano and Wagai (2014) demonstrated strong evidence for aggregate hierarchy in Andosols A horizons with Al-humus complexes likely contributing as a binding agent to form both micro-and macro-aggregates. Gijsman and Sanz (1998) investigated the physical protection of macro-aggregates in Andisols and found elevated CO 2 mineralization after crushing of macro-aggregates.…”

Section: Organic Carbon Accumulation In Andosolsmentioning

confidence: 95%

Nature, properties and function of aluminum–humus complexes in volcanic soils

2016

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Andosols (or Andisols) possess several distinctive properties that are rarely found in other groups of soils. These properties are largely due to the dominance of short-range-ordered minerals (allophane, imogolite and ferrihydrite) and/or metal-humus complexes (Al/Fe-humus complexes) in their colloidal fraction. While several papers have extensively reviewed the nature and properties of short-range-ordered minerals, there is no comprehensive review of the genesis, characteristics and management implications of Al-humus complexes, the dominant form of active Al in non-allophanic Andosols. In this review, we survey the chemical characteristics of Al-humus complexes and discuss the pedogenic environment favoring their formation in non-allophanic Andosols. The role of Al-humus complexes in carbon cycling and soil organic carbon accumulation is emphasized as an important mechanism controlling organic dynamics in Andosols. While non-allophanic Andosols share many common properties with allophanic Andosols, they display several distinct characteristics associated with Al-humus complexes, such as strong acidity and high exchangeable Al content that impair agricultural productivity due to Al phytotoxicity. Thus, we focus on the role of Al-humus complexes in regulating aqueous Al 3+ solubility and release/retention kinetics, Al phytotoxicity, phosphorus dynamics, and suppression of soil-borne diseases. Knowledge of these soil properties as related to Al-humus complexes is necessary to develop effective soil management practices to assure sustainable agricultural productivity in non-allophanic Andosols. Finally, future research needs are identified concerning the role of Al-humus complexes in regulating soil biogeochemical processes.

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Section: Organic Carbon Accumulation In Andosolsmentioning

confidence: 95%

Nature, properties and function of aluminum–humus complexes in volcanic soils

2016

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“…These microorganisms excrete extracellular polysaccharide/polymeric substances that adhere to soil particles, which binds them together, creating a shell around the decomposing SOC nucleus and eventually occluding the SOC residue within (Chenu and Cosentino 2011). When driven by biology, soil structure is typically arranged into a spatial hierarchy, with distinct physical classes of aggregates that are often classified as macroaggregates ([ 250 lm) or microaggregates (\ 250 lm; Asano and Wagai 2014;Elliott 1986;Oades 1984;Six et al 2000Six et al , 2004Tisdall 1996;Tisdall and Oades 1982). These aggregate classes have different properties (size, structural stability, porosity, hydrophilicity), which confer different stabilities to the SOC occluded within (Chenu and Cosentino 2011;Dexter 1988;Kleber et al 2007;Sutton et al 2005;von Lützow et al 2006;Zheng et al 2016).…”

Section: Physical Separationmentioning

confidence: 99%

Calcium-mediated stabilisation of soil organic carbon

2017

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Soils play an essential role in the global cycling of carbon and understanding the stabilisation mechanisms behind the preservation of soil organic carbon (SOC) pools is of globally recognised significance. Until recently, research into SOC stabilisation has predominantly focused on acidic soil environments and the interactions between SOC and aluminium (Al) or iron (Fe). The interactions between SOC and calcium (Ca) have typically received less attention, with fewer studies conducted in alkaline soils. Although it has widely been established that exchangeable Ca (Ca Exch ) positively correlates with SOC concentration and its resistance to oxidation, the exact mechanisms behind this relationship remain largely unidentified. This synthesis paper critically assesses available evidence on the potential role of Ca in the stabilisation of SOC and identifies research topics that warrant further investigation. Contrary to the common view of the chemistry of base cations in soils, chemical modelling indicates that Ca 2? can readily exchange its hydration shell and create inner sphere complexes with organic functional groups. This review therefore argues that both inner-and outer-sphere bridging by Ca 2? can play an active role in the stabilisation of SOC. Calcium carbonate (CaCO 3 ) can influence occluded SOC stability through its role in the stabilisation of aggregates; however, it could also play an unaccounted role in the direct sorption and inclusion of SOC. Finally, this review highlights the importance of pH as a potential predictor of SOC stabilisation mechanisms mediated by Al-or Fe-to Ca, and their respective effects on SOC dynamics.

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“…In general, the respiration was correlated with phos- minerals, (allophane like-materials, Garrido and Matus, 2012;Neculman et al, 2012), Recently, it has been recognized that SOM can be micro-encapsulated inside of highly and this is an important mechanism of C stabilization (Asano and Wagai, 2014;Chevallier et al, 2010). This contrasts with the lower stabilization capacity in kaolinitic, 1:1 clay mineral soil.…”

Section: Carbon Stabilizationmentioning

confidence: 99%

Soil microorganisms and enzyme activity at different levels of organic matter stability

Merino

Godoy

Matus

2016

J. Soil Sci. Plant Nutr.

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Soil biological activity has important implications for soil carbon (C) sequestration. However, very little is known about the environmental factors, particularly the effect of soil mineralogy on availability of C for soil microorganisms. In this study, we have investigated the influences of soil type (clay mineralogy) on C mineralization and its effects on biological activity at different levels of soil organic matter stability. Two soils an allophanic, derived from recent volcanic ash and a kaolinitic, resulting from metamorphic parent materials were physically fractioned in to light (LF, coarse sand 250-2000 µm), intermediate (IF, fine sand53-250 µm) and mineral (MF, silt and clay < 53 µm) fractions. Several biological and biochemical analyses at Ah horizons of mineral soil and physical fractions were conducted: soil respiration, enzymatic activities, carbohydrates and microbial biomass, amongst others soil variables. The results indicated that the bulk soil and physical fractions had a significant impact on cumulative C mineralized after 30 days of incubation and soil enzyme activities. More than 76% of total C-CO 2 variation was explained by stepwise multiple regression analysis including factors such as soil enzymes (β-glucosidase, dehydrogenase and phosphatase) and inorganic P. Soil ATP extraction was a good indicator of microbial activity, because of a positive and significant correlation among ATP and i) C-CO 2 and ii) metabolic quotient (soil respiration rate divided by microbial biomass). We also found an inverse and significant relationship between Al pyrophosphate (Al bound to SOM) and the C-CO 2 in volcanic soil, whereas the same correlation did not occur in kaolinitic soil. Our results confirmed a greater stabilization capacityof MF in allophanic than in kaolinitic soils due to the amorphous minerals clay materials.

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Evidence of aggregate hierarchy at micro- to submicron scales in an allophanic Andisol

Cited by 148 publications

References 65 publications

Nature, properties and function of aluminum–humus complexes in volcanic soils

Nature, properties and function of aluminum–humus complexes in volcanic soils

Calcium-mediated stabilisation of soil organic carbon

Soil microorganisms and enzyme activity at different levels of organic matter stability

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