Factors controlling soil organic carbon persistence along an eroding hillslope on the loess belt

Wiaux, François; Vanclooster, Marnik; Cornélis, Jean-Thomas; Oost, Kristof Van

doi:10.1016/j.soilbio.2014.05.032

Cited by 26 publications

(23 citation statements)

References 47 publications

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“…Previous work (i.e. Wiaux et al, 2014b), has shown that soil surface CO 2 respiration is highly variable along this hillslope, with 30 % more respiration at the downslope and 50 % more at the backslope, relative to the uneroded summit position. Why some controlling factors have been identified, the role of soil physical controls and of the significance of subsoil OC contributions remain unknown.…”

Section: F Wiaux Et Al: Vertical Partitioning and Controlling Factomentioning

confidence: 68%

“…gas diffusion barriers) may also exert an important control on soil microbial activity and soil CO 2 fluxes (e.g. Wiaux et al, 2014b;Ball, 2013;Maier et al, 2011). Furthermore, there is empirical evidence suggesting that physical protection (i.e.…”

Section: F Wiaux Et Al: Vertical Partitioning and Controlling Factomentioning

confidence: 99%

“…We also obtained observations of surface CO 2 fluxes by means of a portable infrared gas analyzer with an automated closed dynamic chamber (LI-8100A system, LI-COR, United States), following Davidson et al (2002). The sampling design of these surface chamber CO 2 fluxes measurements on the same study site has been described in Wiaux et al (2014b).…”

Section: Monitoring Of Soil Co 2 Water and Temperaturementioning

confidence: 99%

“…Here, we focus on the temporal dynamics of the measured variables, as well as the shape of the vertical distribution along the soil profile. The relationship between these variables was previously analyzed in Wiaux et al (2014b) and this is not further discussed here. It should be noted that the comparison of the profile distribution at different dates or of temporal dynamics at different depths is done in a qualitative manner.…”

Section: Spatio-temporal Analysis Of Measured Soil Variablesmentioning

confidence: 99%

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Vertical partitioning and controlling factors of gradient-based soil carbon dioxide fluxes in two contrasted soil profiles along a loamy hillslope

2015

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Abstract. In this study we aim to elucidate the role of physical conditions and gas transfer mechanism along soil profiles in the decomposition and storage of soil organic carbon (OC) in subsoil layers. We use a qualitative approach showing the temporal evolution and the vertical profile description of CO 2 fluxes and abiotic variables. We assessed soil CO 2 fluxes throughout two contrasted soil profiles (i.e. summit and footslope positions) along a hillslope in the central loess belt of Belgium. We measured the time series of soil temperature, soil moisture and CO 2 concentration at different depths in the soil profiles for two periods of 6 months. We then calculated the CO 2 flux at different depths using Fick's diffusion law and horizon specific diffusivity coefficients. The calculated fluxes allowed assessing the contribution of different soil layers to surface CO 2 fluxes. We constrained the soil gas diffusivity coefficients using direct observations of soil surface CO 2 fluxes from chamber-based measurements and obtained a good prediction power of soil surface CO 2 fluxes with an R 2 of 92 %.We observed that the temporal evolution of soil CO 2 emissions at the summit position is mainly controlled by temperature. In contrast, at the footslope, we found that long periods of CO 2 accumulation in the subsoil alternates with short peaks of important CO 2 release. This was related to the high water filled pore space that limits the transfer of CO 2 along the soil profile at this slope position. Furthermore, the results show that approximately 90 to 95 % of the surface CO 2 fluxes originate from the first 10 cm of the soil profile at the footslope. This indicates that soil OC in this depositional context can be stabilized at depth, i.e. below 10 cm. This study highlights the need to consider soil physical properties and their dynamics when assessing and modeling soil CO 2 emissions. Finally, changes in the physical environment of depositional soils (e.g. longer dry periods) may affect the long-term stability of the large stock of easily decomposable OC that is currently stored in these environments.

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Section: F Wiaux Et Al: Vertical Partitioning and Controlling Factomentioning

confidence: 68%

Section: F Wiaux Et Al: Vertical Partitioning and Controlling Factomentioning

confidence: 99%

Section: Monitoring Of Soil Co 2 Water and Temperaturementioning

confidence: 99%

Section: Spatio-temporal Analysis Of Measured Soil Variablesmentioning

confidence: 99%

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Vertical partitioning and controlling factors of gradient-based soil carbon dioxide fluxes in two contrasted soil profiles along a loamy hillslope

2015

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“…SOC at the depositional site is often regarded as more stable with longer turnover times, depending on microbial activity, environmental conditions (Wang et al, 2013), and biogeochemical characteristics of the transported C fractions. However, areas (or landscapes) with a fast burial can lead to the accumulation (storage) of labile SOC, which is still vulnerable to decomposition if the conditions at the site of burial change (Wiaux et al, 2014b). Thus, there is an ongoing discussion about depositional sites of highly dynamic landscapes as C sink or source.…”

Section: Introductionmentioning

confidence: 99%

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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Influence of soil–water content on CO₂ efflux within the elevation transect heavily impacted by erosion

et al. 2018

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This study focused on the effects of organic carbon contents and soil hydraulic conditions on CO2 efflux. Samples were collected at 5 positions (summit, shoulder, backslope, footslope, and toeslope) of the elevation transect affected by erosion and the parent material (loess). Initially, air‐dried soil samples were placed on top of a clay tank, and the samples were wetted by capillary rise to soil saturation, and soil CO2 efflux was measured. Numerical inversions of the measured cumulative capillary rise and evaporation data using the HYDRUS‐1D program were applied to simulate the water regime in the columns and estimate the soil hydraulic parameters. In all cases, the net CO2 efflux (NCER) rapidly increased at the beginning of the wetting. NCER decreased with increasing soil–water content (summit, shoulder, backslope, and loess) or remained relatively stable (footslope and toeslope). The average soil–water content values at the maximal values of NCER (maxNCER) for the summit, shoulder, and footslope were similar. Lower average soil–water contents at maxNCER were simulated for the backslope, toeslope, and loess, which were attributed to the high contents of loess substrate in topsoil samples. The maxNCER measured on topsoils were closely related to the organic carbon contents (R = 0.94) and the maxNCER obtained on all samples correlated with the parameters αRES (R = 0.856) and nRES (R = −0.876) of the soil–water retention curves and saturated hydraulic conductivity (R = 0.856).

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Factors controlling soil organic carbon persistence along an eroding hillslope on the loess belt

Cited by 26 publications

References 47 publications

Vertical partitioning and controlling factors of gradient-based soil carbon dioxide fluxes in two contrasted soil profiles along a loamy hillslope

Vertical partitioning and controlling factors of gradient-based soil carbon dioxide fluxes in two contrasted soil profiles along a loamy hillslope

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

Influence of soil–water content on CO₂ efflux within the elevation transect heavily impacted by erosion

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Factors controlling soil organic carbon persistence along an eroding hillslope on the loess belt

Cited by 26 publications

References 47 publications

Vertical partitioning and controlling factors of gradient-based soil carbon dioxide fluxes in two contrasted soil profiles along a loamy hillslope

Vertical partitioning and controlling factors of gradient-based soil carbon dioxide fluxes in two contrasted soil profiles along a loamy hillslope

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

Influence of soil–water content on CO2 efflux within the elevation transect heavily impacted by erosion

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Influence of soil–water content on CO₂ efflux within the elevation transect heavily impacted by erosion