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  • Chenu, Claire  (53)
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  • 1
    Language: English
    In: Soil Biology and Biochemistry, February 2011, Vol.43(2), pp.280-286
    Description: Microbial communities exist and are active in a complex 3-D physical framework which can cause a variety of micro-environments to develop that are more or less suitable for microbial growth, activity and survival. If there is a significant microbial biogeography at the pore scale in soil, then the relationship between microbial diversity and ecosystem function is likely to be affected by micro-environmental variations at the pore scale. In this laboratory study we show that there is a significant pore-scale microbial biogeography by labelling microbial communities in different pore size classes of undisturbed soil cores with C-labelled fructose (a soluble, labile substrate). This was achieved by adding the substrate solution to the samples at different matric potentials (−100 kPa, −3.15 kPa and −1 kPa; placing the substrate in pores with maximum diameter of 0.97, 9.7 and 97 μm, respectively) and incubating the samples for two weeks. The mineralisation of soil organic carbon and fructose was measured as CO and C–CO , respectively, in the jar headspace throughout the incubation. At the end of incubation we analysed the total microbial community structure using PLFA. The structure of microbial communities in different pore size classes was measured by PLFA stable isotope probing. Total PLFA profiles suggested that there was little effect of the incubation conditions on microbial community structure. However, labelled PLFA profiles showed that microbial community structure differed significantly among pore size classes, the differences being due primarily to variations in the abundance of mono-unsaturated lipids (Gram-biomarkers) and of the fungal biomarker (C18:2(9,12)). This is the first evidence for a significant microbial biogeography at the pore scale in undisturbed soil cores. ► Non-random variation in microbial community structure at pore scale. ► Gram-bacterial and fungal abundance change at pore scale. ► Different regions of the soil pore system can be targetted using combination of C-labelled substrate and moisture release curve.
    Keywords: Stable Isotope Probing ; Undisturbed Cores ; Matric Potential ; Plfa ; Pore Scale ; Biogeography ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 2
    Language: English
    In: Soil Biology and Biochemistry, 29 October 2010, Vol.2011(43), pp.280-286
    Keywords: Environmental Sciences ; Agriculture ; Environmental Sciences ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Source: Hyper Article en Ligne (CCSd)
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  • 3
    In: Global Change Biology, January 2010, Vol.16(1), pp.416-426
    Description: It is estimated that in excess of 50% of the soil carbon stock is found in the subsoil (below 20–30 cm). Despite this very few studies have paid attention to the subsoil. Although surface and subsurface horizons differ in pedological, environmental and physicochemical features, which are all likely to affect the mechanisms and biological actors involved, models of carbon dynamics tend to assume that the underlying processes are identical in all horizons, but with lower gross fluxes in the subsurface. The aim of this study was to test this assumption by analysing factors governing organic matter decomposition in topsoil (from depths of 5–10 cm) and subsoil (from depths of 80–100 cm). To this end, we established incubations that lasted 51 days, in which factors that were thought to control organic matter mineralization were altered: oxygen concentration, soil structure and the energetic and nutritional status. At the end of the incubation period, the microbial biomass was measured and the community level physiological profiles established. The mineralization per unit organic carbon proved to be as important in the subsoil as it was in surface samples, in spite of lower carbon contents and different catabolic profiles. Differences in the treatment effects indicated that the controls on C dynamics were different in topsoil and subsoil: disrupting the structure of the subsoil caused a 75% increase in mineralization while the surface samples remained unaffected. On the other hand, a significant priming affect was found in the topsoil but not in the subsoil samples. Spatial heterogeneity in carbon content, respiration and microbial communities was greater in subsoil than in topsoil at the field scale. These data suggest greater attention should be paid to the subsoil if global C dynamics is to be fully understood.
    Keywords: C ; C Dynamics ; Microbial Community Structure ; Stable Isotopes ; Subsoil
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 4
    Language: English
    In: Global Change Biology, 01 January 2010, Vol.16, pp.416-426
    Description: It is estimated that in excess of 50% of the soil carbon stock is found in the subsoil (below 20–30 cm). Despite this very few studies have paid attention to the subsoil. Although surface and subsurface horizons differ in pedological, environmental...
    Keywords: Life Sciences ; Ecology, Environment ; Meteorology & Climatology ; Environmental Sciences ; Biology
    ISSN: 1354-1013
    E-ISSN: 1365-2486
    Source: Hyper Article en Ligne (CCSd)
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  • 5
    Language: English
    In: Soil Biology and Biochemistry, November 2014, Vol.78, pp.189-194
    Description: Modelling carbon mineralisation in natural soils is a major topic in soil and climate research. Current models need to be improved to include soil structure as an influencing factor to better predict C fluxes between pedosphere and atmosphere and to estimate carbon sequestration potentials. Geometry-based mechanistic modelling approaches have recently been developed to systematically study the effect of soil structure on carbon decomposition. Such models require spatially explicit input parameters describing the architecture of the pore space and the heterogeneous distribution of microbes and organic matter as decomposable substrate. The latter is very difficult to determine , resulting in increased uncertainty in the models. To obtain more realistic input data, we have developed a novel approach to locate soil organic matter (SOM) in undisturbed aggregates of soil using a combination of synchrotron-based X-ray microtomography and osmium as a staining agent for SOM. Here, we present the first results using 5 mm sized soil aggregate samples with contrasting C-contents in which we obtained maps of organic matter distributions in relation to the pore networks at the aggregate scale.
    Keywords: Soil Organic Matter ; Soil Structure ; Carbon Sequestration ; Synchrotron Microtomography ; Staining ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 6
    Language: English
    In: Biology and Fertility of Soils, 2013, Vol.49(7), pp.939-948
    Description: Soil organisms are of fundamental importance for many soil functions, such as organic matter decomposition, nutrient cycling and energy flow. Most research suggests that soil microbial communities are functionally redundant, meaning that there is little relationship between microbial diversity and soil functions. However, the activity of biological communities is known to be affected by their physical environment. Here, the effects of changes in microbial diversity and soil structure on organic C (OC) mineralisation were investigated. Sterile soil samples that had been subjected to different physical perturbations were inoculated with microbial communities with different levels of diversity. The samples were incubated for a period of 127 days and the mineralisation of native and added ( 13 C-labelled substrates, fructose and vanillin) OC was measured. It was hypothesised that the magnitude of the effect of changes in soil structure on OC mineralisation would increase as diversity decreased. The diversity treatment had a small but significant effect on the mineralisation of SOC and of the added substrates. The soil structure treatment had a significant effect only on the mineralisation of the added substrate C. There was no interaction between diversity and soil structure treatments, indicating that the relationship between diversity and OC decomposition was not dependent on the soil physical environment.
    Keywords: Soil microbial diversity ; Soil structure ; Soil organic carbon mineralisation ; Carbon dynamics
    ISSN: 0178-2762
    E-ISSN: 1432-0789
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  • 7
    In: FEMS Microbiology Ecology, 2013, Vol. 86(1), pp.26-35
    Description: Little is known about the factors that regulate C mineralisation at the soil pore scale or how these factors vary throughout the pore network. This study sought to understand how the decomposition of organic carbon varies within the soil pore network and to determine the relative importance of local environmental properties relative to biological properties as controlling factors. This was achieved by sterilising samples of soil and reinoculating them with axenic bacterial suspensions using the matric potential to target different locations in the pore network. Carbon mineralisation curves were described with two-compartment first-order models to distinguish CO 2 derived from the labile organic carbon released during sterilisation from CO 2 derived from organic C unaffected by sterilisation. The data indicated that the size of the labile pool of organic C, possibly of microbial origin, varied as a function of location in the pore network but that the organic carbon unaffected by sterilisation did not. The mineralisation rate of the labile C varied with the bacterial type inoculated, but the mineralisation rate of the organic C unaffected by sterilisation was insensitive to bacterial type. Taken together, the results suggest that microbial metabolism is a less significant regulator of soil organic carbon decomposition than are microbial habitat properties.
    Keywords: Pore Network ; C Mineralisation ; Microbial Habitat ; Matric Potential ; Sterilisation ; Inoculation
    ISSN: 01686496
    E-ISSN: 1574-6941
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  • 8
    Language: English
    In: Sci Rep, 2018, Vol.8(1), pp.4057-4057
    Description: A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
    Keywords: Biology;
    ISSN: 2045-2322
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  • 9
    Language: English
    In: Biogeochemistry, 09 September 2011, Vol.106, pp.5-21
    Description: he soil microbial biomass (SMB) is known to participate in key soil processes such as the decomposition of soil organic matter (SOM). However, its contribution to the isotopic composition of the SOM is not clear yet. Shifts in the 13C and 15N natural abundances of the SMB and SOM fractions...
    Keywords: Environmental Sciences ; Environmental Sciences ; Biology ; Geology ; Chemistry
    ISSN: 0168-2563
    E-ISSN: 1573-515X
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  • 10
    Language: English
    In: Sci Rep, 2017, Vol.7(1), pp.4280-4280
    Description: An underlying assumption of most soil carbon (C) dynamics models is that soil microbial communities are functionally similar; in other words, that microbial activity under given conditions is not dependent on the composition or diversity of the communities. Although a number of studies have indicated that microbial communities are not intrinsically functionally similar, most soil C dynamics models can adequately describe C dynamics without explicitly describing microbial functioning. Here, we provide a mechanistic basis for reconciling this apparent discrepancy. In a reciprocal transplant experiment, we show that the environmental context (soil and pore-network properties) of microbial communities can constrain the activity of functionally different communities to such an extent that their activities are indistinguishable. The data also suggest that when microbial activity is less constrained, the intrinsic functional differences among communities can be expressed. We conclude that soil C dynamics may depend on microbial community structure or diversity in environments where their activity is less constrained, such as the rhizosphere or the litter layer, but not in oligotrophic environments such as the mineral layers of soil.
    Keywords: Biology;
    ISSN: 2045-2322
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