Legacy of human-induced C erosion and burial on soil–atmosphere C exchange

Oost, Kristof Van; Verstraeten, Gert; Doetterl, Sebastian; Notebaert, Bastiaan; Wiaux, François; Broothaerts, Nils; Six, Johan

doi:10.1073/pnas.1211162109

Cited by 139 publications

(125 citation statements)

References 36 publications

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“…In soils, only glucosamine (GluN), galactosamine (GalN), and muramic acid are found in quantifiable concentrations. AS provide a generally readily available energy source for microorganisms and are easy to decompose compared to more recalcitrant organic matter such as lignin or lipids (Amelung et al, 2001(Amelung et al, , 2008von Luetzow et al, 2006;Roberts et al, 2007;Schmidt et al, 2011). AS turnover is, therefore, fast compared to other stabilized SOC fractions.…”

Section: Introductionmentioning

confidence: 99%

“…For details on the gathered fractions see the original study and the concepts of Six et al (1998Six et al ( , 2002. In short, the scheme consists of a series of chemical and physical fractionation techniques applied to isolate functional SOC fractions, differentiated by stabilization mechanisms (chemical, biochemical and physical) which can also be associated with different (potential) turnover times (see also von Luetzow et al, 2006). Background information to the key soil and geomorphological properties as well as the abundance and composition of identified SOC fractions as described by Doetterl et al (2012) and Z. for the investigated soils can be found in Table 1.…”

Section: Soc Fractionationmentioning

confidence: 99%

“…Distinguishing the role of a single mechanism for stabilizing C is, hence, a difficult task and a matter of ongoing debate and research (Berhe et al, 2012). For example, some authors argue that the biochemical recalcitrance of organic molecules does not exist per se and has always to be seen in an environmental context (Kleber, 2010), while others argue that "recalcitrant SOM [soil organic matter] can be defined by intrinsic molecular properties, but these properties may be fairly irrelevant under specific environmental conditions" (von Luetzow and Koegel-Knabner, 2010).…”

Section: Introductionmentioning

confidence: 99%

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Soil redistribution and weathering controlling the fate of geochemical and physical carbon stabilization mechanisms in soils of an eroding landscape

et al. 2015

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Abstract. The role of eroding landscapes in organic carbon stabilization operating as C sinks or sources has been frequently discussed, but the underlying mechanisms are not fully understood. Our analysis aims to clarify the effects of soil redistribution on physical and biogeochemical soil organic carbon (SOC) stabilization mechanisms along a hillslope transect. The observed mineralogical differences seem partly responsible for the effectiveness of geochemical and physical SOC stabilization mechanisms as the mineral environment along the transect is highly variable and dynamic. The abundance of primary and secondary minerals and the weathering status of the investigated soils differ drastically along this transect. Extractable iron and aluminum components are generally abundant in aggregates, but show no strong correlation to SOC, indicating their importance for aggregate stability but not for SOC retention. We further show that pyrophosphate extractable soil components, especially manganese, play a role in stabilizing SOC within non-aggregated mineral fractions. The abundance of microbial residues and measured 14 C ages for aggregated and nonaggregated SOC fractions demonstrate the importance of the combined effect of geochemical and physical protection to stabilize SOC after burial at the depositional site. Mineral alteration and the breakdown of aggregates limit the protection of C by minerals and within aggregates temporally. The 14 C ages of buried soil indicate that C in aggregated fractions seems to be preserved more efficiently while C in nonaggregated fractions is released, allowing a re-sequestration of younger C with this fraction. Old 14 C ages and at the same time high contents of microbial residues in aggregates suggest either that microorganisms feed on old carbon to build up microbial biomass or that these environments consisting of considerable amounts of old C are proper habitats for microorganisms and preserve their residues. Due to continuous soil weathering and, hence, weakening of protection mechanisms, a potential C sink through soil burial is finally temporally limited.

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Section: Introductionmentioning

confidence: 99%

Section: Soc Fractionationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Soil redistribution and weathering controlling the fate of geochemical and physical carbon stabilization mechanisms in soils of an eroding landscape

et al. 2015

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“…Although colluvial soils may therefore store more C than non-eroding soils, the rate at which the buried SOC cycles remains poorly quantified: on the one hand, 137 Cs and C inventory measurements showed that a substantial part of the deposited C in the colluvial soils of first-order catchments is effectively protected on the timescale of 50 yr ; on the other hand, studies covering millennial timescales showed that colluvial sediments on the Belgian loess belt that were deposited several centuries to millennia ago are typically depleted in SOC relative to the source areas (e.g. Vancampenhout et al, 2008;Van Oost et al, 2012), indicating that the deposited C in colluvial soils is at least partially mineralised on the timescale of several centuries.…”

Section: Z Wang Et Al: the Fate Of Buried Organic Carbon In Colluvimentioning

confidence: 99%

“…Colluvial soils therefore may be interpreted as chronostratigraphy in which young deposits are found at shallow depth and sediment age increases with depth (Van Oost et al, 2012). The efficiency of C burial can then be regarded as the fraction of deposited C that is preserved in the buried sediments.…”

Section: Burial Efficiencymentioning

confidence: 99%

The fate of buried organic carbon in colluvial soils: a long-term perspective

et al. 2014

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Abstract. Colluvial soils are enriched in soil organic carbon (SOC) in comparison to the soils of upslope areas due to the deposition and progressive burial of SOC. This burial of SOC has important implications for the global carbon cycle, but the long-term dynamics of buried SOC remain poorly constrained. We addressed this issue by determining the SOC burial efficiency (i.e. the fraction of originally deposited SOC that is preserved in colluvial deposits) of buried SOC as well as the SOC stability in colluvial soils. We quantified the turnover rate of deposited SOC by establishing sediment and SOC burial chronologies. The SOC stability was derived from soil incubation experiments and the δ 13 C values of SOC. The C burial efficiency was found to decrease with time, reaching a constant ratio of approximately 17 % by about 1000-1500 yr post-burial. This decrease is attributed to the increasing recalcitrance of the remaining buried SOC with time and a less favourable environment for SOC decomposition with increasing depth. Buried SOC in colluvial profiles was found to be more stable and degraded in comparison to SOC sampled at the same depth at a stable reference location. This is due to the preferential mineralisation of the labile fraction of the deposited SOC. Our study shows that SOC responds to burial over a centennial timescale; however, more insight into the factors controlling this response is required to fully understand how this timescale may vary, depending on specific conditions such as climate and depositional environment.

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Predicting the long‐term fate of buried organic carbon in colluvial soils

Wang

Oost

Govers

2015

Global Biogeochemical Cycles

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A significant part of the soil organic carbon (SOC) that is eroded in uplands is deposited and buried in colluvial settings. Understanding the fate of this deposited soil organic carbon is of key importance for the understanding of the role of (accelerated) erosion in the global C cycle: the residence time of the deposited carbon will determine if, and for how long, accelerated erosion due to human disturbance will induce sequestration of SOC from the atmosphere to the soil. Experimental studies may provide useful information, but, given the time scale under consideration, the response of the colluvial SOC can only be simulated using numerical models which need careful calibration using field data. In this study, we present a depth explicit SOC model including soil profile evolution due to sedimentation to simulate the long-term C dynamics in colluvial soils. The SOC profile predicted by our model is in good agreement with field observations. The C burial efficiency (the ratio of current C content of the buried sediments to the original C content at the time of sedimentation) of deposited sediments exponentially decreases with time and gradually reaches an equilibrium value. This equilibrium C burial efficiency is positively correlated with the sedimentation rate. The sedimentation rate is crucial for the long-term dynamics of the deposited SOC as it controls the time that buried sediments spend at a given soil depth, thereby determining its temporal evolution of C input and decomposition rate during the burial process: C input and decomposition rate vary with depth due to the vertical variation of root distribution and soil environmental factors such as (but not limited to) humidity, temperature, and aeration. The model demonstrates that, for the profiles studied, it takes circa 300 years for the buried SOC to lose half of its C load. It would also take centuries for the SOC accumulated in colluvial soils over the past decades due to soil redistribution under mechanized agriculture to be released to the atmosphere after the application of soil conservation measures such as conservation tillage.

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Legacy of human-induced C erosion and burial on soil–atmosphere C exchange

Cited by 139 publications

References 36 publications

Soil redistribution and weathering controlling the fate of geochemical and physical carbon stabilization mechanisms in soils of an eroding landscape

Soil redistribution and weathering controlling the fate of geochemical and physical carbon stabilization mechanisms in soils of an eroding landscape

The fate of buried organic carbon in colluvial soils: a long-term perspective

Predicting the long‐term fate of buried organic carbon in colluvial soils

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