The Rock-Eval® signature of soil organic carbon in arenosols of the Senegalese groundnut basin. How do agricultural practices matter?

Malou, Oscar Pascal; Sebag, David; Moulin, Patricia; Chevallier, Tiphaine; Badiane-Ndour, Ndèye Yacine; Thiam, Abou; Chapuis‐Lardy, Lydie

doi:10.1016/j.agee.2020.107030

Cited by 19 publications

(15 citation statements)

References 57 publications

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“…4c,e), emphasizing the relatively low contribution of resistant pool compared to the most labile pools. Similar results have been obtained when advanced decomposition of OM affects both thermally labile and resistant pools, as in Arenosols for example (Malou et al 2020;Romanens et al, 2019). In the context of the present study, the decomposition of thermally resistant pools can be explained by an earlier phase of pedogenesis and this peculiarity of the trend supports the hypothesis that these soils located along the trend are paleosols.…”

Section: Correlation Of Soil Unitssupporting

confidence: 90%

“…Finally, as shown in previous studies (Malou et al 2020;Thoumazeau et al, 2020), a Delta I-index can be calculated: it refers to the difference between the I-index value of each sample and the I-index value calculated with the "humic trend" equation (in bold in Fig. 3b), calculated starting from study area sample data, at the R-index value of each sample.…”

Section: Soil Analysesmentioning

confidence: 99%

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Reconsidering the compound effect of geomorphology, vegetation, and climate change on paleopedogenesis in sensitive environments (Northern Apennines, Italy)

Masseroli

Villa

Mariani

et al. 2021

CATENA

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Complex sequences of paleosols are often formed by the interaction between pedogenesis and geomorphological evolution. Their study, particularly in mountain areas, is useful to reconstruct past environmental conditions as well as climate shifts, and to gather information on the morphodynamical processes affecting the landscape through time. Since the combined role that all different factors can play in the soil formation and evolution through time and space influences the formation and evolution of those complex paleosol sequences, a multidisciplinary study was conducted at the NW slope of Mt. Cusna (Northern Apennines, Italy). This work aims to reconstruct and to evaluate how the interactions between the geomorphological context, the Holocene climate variations, and the modification of the vegetation cover and composition influence the soil development of this area. A combination of routine soil analyses (i.e., grain-size distributions, total organic carbon, total nitrogen, pH, and Fe/Al extractions), soil micromorphology and the Rock-Eval ® pyrolysis allowed to characterize and to correlate the different soil units constituting a toposequence of six soil profiles. The presence of different pedological units that can be correlated along the slope underlines the occurrence of separate events of pedogenesis, spatio-temporally linked to recognizable stability phases at slope scale. These phases of biostasy, characterized by vegetation cover and soil development, alternate to phases of rhexistasy, characterized mainly by slope instability (i.e., aggradation/degradation). In detail, in the Mt. Cusna toposequence three different soil units, linked to three different stability phases, have been identified: the earliest stability phase, characterized by the presence of well-developed Luvisols, *Revision, Unmarked Click here to download Revision, Unmarked: Manuscript_Masseroli_etal_rev.docx the subsequent stability phase typified by less expressed Luvisols, and the ongoing stability phase with Leptosols. This latter pedogenetic phase, in some cases, is superimposed to the previous one, so affecting the exhumed paleosols. In this light, the Mt. Cusna toposequence characterization allowed to enlighten the complexity of soil polygenesis in higher detail than the previous studies, not only reconstructing the past environmental conditions but also inferring the succession of phases of slope stability and phases characterized by erosion and deposition processes.

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Section: Correlation Of Soil Unitssupporting

confidence: 90%

Section: Soil Analysesmentioning

confidence: 99%

Reconsidering the compound effect of geomorphology, vegetation, and climate change on paleopedogenesis in sensitive environments (Northern Apennines, Italy)

Masseroli

Villa

Mariani

et al. 2021

CATENA

View full text Add to dashboard Cite

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“…Based on our data, we can hypothesise that active decomposition and mineralisation processes were operant at the CaCO 3 -free site; which meant that OM composition was dominated either by relatively fresh plant material that had not yet fully entered the decomposition continuum or highly decomposed residues from active decomposition and mineralisation processes. This would result in a thermal signature with a relatively increased presence of thermally labile compounds (high I index ), but also thermally stable compounds representing advanced decomposition residues (A5; Malou et al 2020 ). This proposition is also consistent with the observation that the bulk SOC contents were lower and the δ 13 C values were higher at the CaCO 3 -free site.…”

Section: Discussionmentioning

confidence: 99%

“…The S2 thermogram was split into 5 separate components (A1:A5) at fixed temperature bounds and then used to calculate the I and R Index scores according to Eqs. 1 and 2 (Malou et al 2020 ; Sebag et al 2016 ). The I and R Index scores from our samples were then compared to the negative linear trend (“humic” trend) from geochemically- (Matteodo et al 2018 ) and pedoclimatically-diverse datasets (Sebag et al 2016 ).…”

Section: Methodsmentioning

confidence: 99%

“…The I and R Index scores from our samples were then compared to the negative linear trend (''humic'' trend) from geochemically- (Matteodo et al 2018) and pedoclimatically-diverse datasets (Sebag et al 2016). This trend in thermal stability is commonly ascribed to changes in OM quality upon decomposition in soils (Malou et al 2020;Thoumazeau et al 2020).…”

Section: Soil Organic Carbon Analysis (D 13 C Values and Rock-evalò)mentioning

confidence: 99%

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Evidence linking calcium to increased organo-mineral association in soils

et al. 2021

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Geochemical indicators are emerging as important predictors of soil organic carbon (SOC) dynamics, but evidence concerning the role of calcium (Ca) is scarce. This study investigates the role of Ca prevalence in SOC accumulation by comparing otherwise similar sites with (CaCO3-bearing) or without carbonates (CaCO3-free). We measured the SOC content and indicators of organic matter quality (C stable isotope composition, expressed as δ13C values, and thermal stability) in bulk soil samples. We then used sequential sonication and density fractionation (DF) to separate two occluded pools from free and mineral-associated SOC. The SOC content, mass, and δ13C values were determined in all the fractions. X-ray photoelectron spectroscopy was used to investigate the surface chemistry of selected fractions. Our hypothesis was that occlusion would be more prevalent at the CaCO3-bearing site due to the influence of Ca on aggregation, inhibiting oxidative transformation, and preserving lower δ13C values. Bulk SOC content was twice as high in the CaCO3-bearing profiles, which also had lower bulk δ13C values, and more occluded SOC. Yet, contrary to our hypothesis, occlusion only accounted for a small proportion of total SOC (< 10%). Instead, it was the heavy fraction (HF), containing mineral-associated organic C, which accounted for the majority of total SOC and for the lower bulk δ13C values. Overall, an increased Ca prevalence was associated with a near-doubling of mineral-associated SOC content. Future investigations should now aim to isolate Ca-mediated complexation processes that increase organo-mineral association and preserve organic matter with lower δ13C values.

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The Rock‐Eval Method

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The Rock-Eval® signature of soil organic carbon in arenosols of the Senegalese groundnut basin. How do agricultural practices matter?

Cited by 19 publications

References 57 publications

Reconsidering the compound effect of geomorphology, vegetation, and climate change on paleopedogenesis in sensitive environments (Northern Apennines, Italy)

Reconsidering the compound effect of geomorphology, vegetation, and climate change on paleopedogenesis in sensitive environments (Northern Apennines, Italy)

Evidence linking calcium to increased organo-mineral association in soils

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