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  • 1
    Electronic Resource
    Electronic Resource
    Isotope and molecular evidence for direct input of maize leaf wax n-alkanes into crop soils
    Amsterdam : Elsevier
    Organic Geochemistry 22 (1994), S. 349-351 
    Details
    ISSN: 0146-6380
    Keywords: Zea mays ; ^1^3C of leaf wax and soils ; leaf waxes ; n-alkanes ; soil hydrocarbons
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0146-6380(94)90181-3
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  • 2
    Electronic Resource
    Electronic Resource
    Carbon cycling and sequestration opportunities in temperate grasslands (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 20 (2004), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Temperate grasslands account for c. 20% of the land area in Europe. Carbon accumulation in grassland ecosystems occurs mostly below ground and changes in soil organic carbon stocks may result from land use changes (e.g. conversion of arable land to grassland) and grassland management. Grasslands also contribute to the biosphere–atmosphere exchange of non-CO2 radiatively active trace gases, with fluxes intimately linked to management practices. In this article, we discuss the current knowledge on carbon cycling and carbon sequestration opportunities in temperate grasslands. First, from a simple two-parameter exponential model fitted to literature data, we assess soil organic carbon fluxes resulting from land use change (e.g. between arable and grassland) and from grassland management. Second, we discuss carbon fluxes within the context of farming systems, including crop–grass rotations and farm manure applications. Third, using a grassland ecosystem model (PaSim), we provide estimates of the greenhouse gas balance, in CO2 equivalents, of pastures for a range of stocking rates and of N fertilizer applications. Finally, we consider carbon sequestration opportunities for France resulting from the restoration of grasslands and from the de-intensification of intensive livestock breeding systems. We emphasize major uncertainties concerning the magnitude and non-linearity of soil carbon stock changes in agricultural grasslands as well as the emissions of N2O from soil and of CH4 from grazing livestock.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.2004.tb00362.x
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  • 3
    Electronic Resource
    Electronic Resource
    Isolation and analysis of the non-hydrolysable fraction of a forest soil and an arable soil (Lacadée, southwest France) (2003)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 54 (2003), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Recent studies have pointed to the occurrence in soil organic matter of an insoluble macromolecular fraction, resistant to drastic alkali and acid hydrolysis. This non-hydrolysable fraction may contribute to the stable carbon pool in the soil and thus be important for the global carbon budget. We have developed a method to isolate such chemically resistant components, whilst ensuring complete elimination of the hydrolysable constituents of the organic matter but avoiding the formation of insoluble compounds via Maillard-type condensation reactions. Maize leaves, material especially susceptible to artefact formation, were used for this optimization. Several of the treatments that we tested, including the Klason lignin protocol, proved unsuitable. The most suitable protocol, by progressive hydrolysis with trifluoroacetic and hydrochloric acid, revealed a non-hydrolysable fraction in maize leaves accounting for about 5% by weight of the leaves and corresponding chiefly to lignin and condensed tannins. The protocol was applied to a forest soil and to the soil from an adjacent plot cleared 35 years ago and since cropped continuously with maize. The abundance, chemical composition and sources of the non-hydrolysable fraction of these two soils were determined by a combination of spectroscopy, pyrolysis and electron microscopy. This fraction accounted for about 6% of the total organic carbon of both soils; it contains aliphatic moieties, black carbon, melanoidins and, we think, condensed tannins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2003.00520.x
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamics of soil organic matter associated with particle-size fractions of water-stable aggregates (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 51 (2000), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Stable macroaggregates (〉 200 μm) of cultivated soils are reported in the literature to be richer in organic carbon, and in young organic carbon in particular, than microaggregates (〈 200 μm). However, the nature of this additional carbon is not yet known. To determine it, we compared the composition of organic matter in stable macroaggregates with that in unstable ones. Macroaggregates 2–3 mm in diameter were separated from two silty cultivated soils from the Paris basin. They were slaked, and the primary particle composition of the resulting fractions was analysed. We used the natural abundance of 13C to quantify the amount of young carbon, derived from a maize crop, in the various size fractions.The stable macroaggregates were richer in total C and in young C (younger than 6 and 23 years respectively in the two soils studied) than the unstable ones. This young C comprised 50% particulate organic matter, 20% associated with silt and 30% with clay particles. We propose a schematic composition of aggregates in these soils in which stable aggregates are formed by the binding of microaggregates by additional young organic matter, predominantly plant debris. Young organic matter is preferentially incorporated and is responsible for aggregation, though it is eventually redistributed among aggregate classes through the destruction and re-formation of the aggregates. We have developed a model to simulate this redistribution. The model shows that stable macroaggregates have a life of a few years, but that microaggregates may exist for decades. We suggest that the stabilization and de-stabilization of macroaggregates in soils is linked to the incorporation and biodegradation of plant debris.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.2000.00353.x
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  • 5
    Electronic Resource
    Electronic Resource
    The significance of organic separates to carbon dynamics and its modelling in some cultivated soils (1996)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 47 (1996), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Soil organic matter (SOM) dynamics are usually described by compartmental models. We have sought SOM separates that might be related to SOM dynamic compartments. The turnover of C in various separates from long–term field experiments with maize was measured using the natural 13C labelling technique. The Rothamsted carbon model gave a good prediction of the observed C turnover. Primary particle–size fractions coarser than 50 μm had short lives, and could be associated with the plant structural compartment of models. Water–extractable components are enriched in young C but cannot be associated with labile compartments. None of the chemical separates obtained by acid hydrolysis, wet oxidation, thermic oxidation, pyrolysis or alkaline extraction, were enriched either in young or old C. The results showed neither a sequential relation between fulvic acids and humic acids nor a resistance of nonhydrolysable material. The range of lifetimes of soil C seems to be determined more by physical position and protection than by the chemical nature of SOM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1996.tb01848.x
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  • 6
    Electronic Resource
    Electronic Resource
    Fate of particulate organic matter in soil aggregates during cultivation (1996)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 47 (1996), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Particulate organic matter (POM) is a labile fraction of soil organic matter which is thought to be physically protected from biodegradation when within soil aggregates. We have developed a fractionation method to separate POM located outside stable soil macroaggregates (〉 200 μm) and microaggregates (50–200 μm) from that within them, and applied it to a cultivation sequence of humic loamy soils. The natural abundance of 13C was used to determine the amounts of POM derived from forest and that derived from crop in the free and occluded fractions. In the forest soil the free and occluded POM fractions had the same composition, morphology and isotopic signature. On cultivation the amounts of POM decreased sharply. The loss of C in the POM from forest was mainly from POM outside the aggregates. The POM occluded within microaggregates was found to turnover slowly. This may be due either to its recalcitrant chemical nature or to its physical protection within microaggregates
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1996.tb01849.x
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  • 7
    Electronic Resource
    Electronic Resource
    Medium-term transformations of organic N in a cultivated soil (1995)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 46 (1995), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: We followed in situ the evolution of nitrogen recently incorporated into a soil under maize culture for 4 years. Each year, a different pair of plots treated by removal or return of maize crop residues received a single pulse of 15N-labelled fertilizer. Unlabelled fertilizer was otherwise supplied. In parallel, plots supplied with unlabelled fertilizer received a single pulse of 15N-labelled maize crop residues.Varying weather affected total and fertilizer-derived N in the crop and residual inorganic N in the topsoil, but it did not affect fertilizer-N immobilization and remineralization. There was no consistent effect of crop residue return on total soil N, immobilization of fertilizer N, or the decay kinetics of recently immobilized N.Recently incorporated organic N from crop residues and microbial immobilization of inorganic N displayed similar mid-term decay kinetics. Crop residue N and immobilized N enter a labile compartment with an average residence time of a few months. A proportion, estimated at 28%, enters a more stable compartment from which the mineralization was imperceptible in 4 years. Particle-size fractions 〉50 um, which receive most of the crop residue N, retained it for only a short time. The mid-term stabilization of N was mainly in soil fractions 〈50 um.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1995.tb01346.x
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  • 8
    Electronic Resource
    Electronic Resource
    Total and young organic matter distributions in aggregates of silty cultivated soils (1995)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 46 (1995), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The distribution of organic matter in soil aggregates was investigated by fractionating aggregates and measuring carbon contents. The distribution of recently incorporated organic carbon was analyzed using 13C natural abundance. The soils of the experiment, which previously only had C3 vegetation, were cropped to maize, aC4 plant, for 6 or 23 years.Aggregate size distributions were determined for silty soils with different organic matter contents. Slaking-resistant macroaggregates were enriched in C as compared to dry-sieved macroaggregates or to microaggregates, and the C content increased with the size of aggregates. The δ13C value was used to calculate the amount of C3-derived and C4-derived organic carbon in the fractions. The larger carbon contents in stable macroaggregates were due to young C4-derived organic carbon (〈6 or 23 years), and we concluded that young organic matter was responsible for macroaggregate stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1995.tb01341.x
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  • 9
    Electronic Resource
    Electronic Resource
    Present dynamics of the savanna-forest boundary in the Congolese Mayombe: a pedological, botanical and isotopic (13C and 14C) study (1996)
    Springer
    Oecologia 106 (1996), S. 516-524 
    Details
    ISSN: 1432-1939
    Keywords: Congo ; Forest-savanna dynamics ; 13C natural abundance ; Forest encroachment ; Pioneer trees
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isolated savannas enclosed by forest are especially abundant in the eastern part of the Congolese Mayombe. They are about 3000 years old, and were more extensive some centuries ago. The boundary between forest and savanna is very abrupt, as a consequence of the numerous savanna fires lit by hunters. Floristic composition and vegetation structure data, organic carbon ratios, Δ14C and δ13C measurements presented here show that forest is spreading over savanna at the present time and suggest that the rate of forest encroachment is is currently between 14 and 75 m per century, and more probably about 20–50 m per century. As most savannas are less than 1 km across, such rates mean, assuming there are no changes in environmental conditions, that enclosed savannas could completely disappear in the Mayombe in about 1000–2000 years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329710
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  • 10
    Electronic Resource
    Electronic Resource
    The dynamics of carbon in particle-size fractions of soil in a forest-cultivation sequence (1998)
    Springer
    Plant and soil 201 (1998), S. 49-57 
    Details
    ISSN: 1573-5036
    Keywords: carbon-13 ; maize ; modelling ; physical protection ; stablecarbon isotope
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cultivation of forest and grassland soils induces heavy changes in soil organic matter (SOM) dynamics. To better predict the effect of cultivation, there is a need to describe which organic pools are affected and to which extent. We used a chronosequence of thick humic forest soils converted to maize cultivation for 40 yr in southwest France. The dynamics of soil carbon was investigated through particle-size fractionation and the use of 13C allowed to distinguish forest-derived organic matter and new crop-derived organic matter. This partitioning of soil carbon by size on one hand and by age on the other provided a precise description of carbon turnover. The level towards which tend the organic pools under cultivation showed that the decay rates of soil carbon were one order of magnitude higher under cultivation than under forest. SOM can thus be considered as deprotected under cultivation. All size fractions appeared to be deprotected to the same extent. A progressive transfer of silt-sized C to clay-sized C was nevertheless suspected and attributed to the decreasing stability of fine silt-sized microaggregates with cultivation. SOM furthermore contained some very stable C present as silt-sized and possibly clay-sized particles. The turnover times of maize-derived organic matter was the same as that observed in similar soils cultivated for centuries. This indicated that the new conditions induced by cultivation were reached in the very first years after forest clearing and that the high initial SOM content and high mineralization rate of initial organic matter did not affect the dynamics of newly incorporated carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004337314970
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