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首页> 外文期刊>Plant and Soil >Effect of C3-C4 vegetation change on delta 13C and delta 15N values of soil organic matter fractions separated by thermal stability.
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Effect of C3-C4 vegetation change on delta 13C and delta 15N values of soil organic matter fractions separated by thermal stability.

机译：C3-C4植被变化对通过热稳定性分离的土壤有机质组分的δ13C和δ15N值的影响。

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Carbon isotopic composition of soils subjected to C3-C4 vegetation change can be used to estimate C turnover in bulk soil and in soil organic matter (SOM) pools with fast and intermediate turnover rates. We hypothesized that the biological availability of SOM pools is inversely proportional to their thermal stability, so that thermogravimetry can be used to separate SOM pools with contrasting turnover rates. Soil samples from a field plot cultivated for 10.5 years with the perennial C4 plant Miscanthus x gigantheus were analysed by thermogravimetry coupled with differential scanning calorimetry (DSC). Three SOM fractions were distinguished according to the differential weight losses and exothermic or endothermic reactions measured by DSC. The delta 13C and delta 15N values of these three fractions obtained by gradual soil heating were measured by IRMS. The weight losses up to 190 degrees C mainly reflected water evaporation because no significant C and N losses were detected and delta 13C and delta 15N values of the residual SOM remained unchanged. The delta 13C values (-16.4 per mil) of SOM fraction decomposed between 190 and 390 degrees C (containing 79% of total soil C) were slightly closer to that of the Miscanthus plant tissues ( delta 13C=-11.8 per mil) compared to the delta 13C values (-16.8 per mil) of SOM fraction decomposed above 390 degrees C containing the residual 21% of SOM. Thus, the C turnover in the thermally labile fraction was faster than that in thermally stable fractions, but the differences were not very strong. Therefore, in this first study combining TG-DSC with isotopic analysis, we conclude that the thermal stability of SOM was not very strongly related to biological availability of SOM fractions. In contrast to delta 13C, the delta 15N values strongly differed between SOM fractions, suggesting that N turnover in the soil was different from C turnover. More detailed fractionation of SOM by thermal analysis with subsequent isotopic analysis may improve the resolution for delta 13C..
机译：经历C3-C4植被变化的土壤的碳同位素组成可用于估算散装土壤和土壤有机质（SOM）库中具有快速和中等转化率的碳转化。我们假设SOM池的生物利用度与其热稳定性成反比，因此可以使用热重分析法以不同的周转率分离SOM池。通过热重分析和差示扫描量热法（DSC）分析了使用多年生C4植物Miscanthus x gigantheus种植了10.5年的田地的土壤样品。根据差示重量损失和DSC测量的放热或吸热反应，将三个SOM馏分区分开。通过IRMS测量通过逐步土壤加热获得的这三个馏分的δ13C和δ15N值。高达190摄氏度的重量损失主要反映了水的蒸发，因为未检测到明显的C和N损失，并且残留SOM的delta 13C和delta 15N值保持不变。在190到390摄氏度之间分解的SOM分数的13C值（-16.4 / mil）（占总土壤C的79％）比芒草植物组织的δ13C值（Delta 13C = -11.8 / mil）略接近SOM分数的13C值（-16.8 / mil）在390摄氏度以上分解，包含21％的SOM。因此，热不稳定馏分中的C转化率快于热稳定馏分中的C转化率，但差异不是很大。因此，在这项将TG-DSC与同位素分析相结合的第一项研究中，我们得出的结论是SOM的热稳定性与SOM馏分的生物利用度不是很强相关。与增量13C相比，增量15N值在SOM分数之间有很大差异，这表明土壤中的氮转化与碳转化不同。通过热分析和随后的同位素分析对SOM进行更详细的分馏，可以提高δ13C的分离度。

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