Thermal oxidation does not fractionate soil organic carbon with differing biological stabilities
Thermal oxidation does not fractionate soil organic carbon with differing biological stabilities
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DOI：
10.1002/jpln.201600172
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发表时间：
2017-02
影响因子：
2.5
通讯作者：
Marcus Schiedung;A. Don;Patrick Wordell-Dietrich;V. Alcántara;P. Kuner;G. Guggenberger
中科院分区：
文献类型：
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作者：
Marcus Schiedung;A. Don;Patrick Wordell-Dietrich;V. Alcántara;P. Kuner;G. Guggenberger
热分析技术已被用于区分具有不同热稳定性的土壤有机碳库。一些研究表明热稳定性和生物稳定性之间存在相关性，而另一些研究则报告了不一致的关系。尽管这些有争议的发现和没有标准化的方法，最近发表的一些研究使用热分析技术来确定矿物土壤中有机碳的生物稳定性和质量。本研究结合演化气体分析和同位素比质谱分析，研究了200°C至400°C温度水平下的热氧化是否能够识别矿物土壤中具有不同生物稳定性的有机碳池。土壤样本来自三个地点，这些地点在以前的农业农田（仅c3植物）种植后种植芒草（c4植物）超过17年。由于13C含量的自然变化，可以区分出年轻和不稳定的芒豆源有机碳与稳定和年老的c3植物源有机碳。在350℃以下，随温度升高，芒草源有机碳的比例显著增加，表明随着温度升高，活性有机碳和幼嫩有机碳的氧化增加。利用密度分数对土壤样品热氧化有机碳进行验证，发现热氧化模式不能反映有机碳的生物稳定性。芒草幼龄有机碳中明显富集了生物活性颗粒有机碳（来自密度分馏的轻组分）。然而，热氧化模式显示，这些生物不稳定组分的优先氧化不是在低温下，而是在高温下。生物稳定的矿物相关密度分数（重分数）则相反。基于不同土壤类型，土壤有机碳在200 ~ 400℃之间的热稳定性不适合作为有机碳生物稳定性的指标，因此热氧化法不能区分不同生物稳定性的有机碳库。
Thermal analysis techniques have been used to differentiate soil organic carbon (SOC) pools with differing thermal stability. A correlation between thermal and biological stability has been indicated in some studies, while others reported inconsistent relationships. Despite these controversial findings and no standardized method, several recently published studies used thermal analysis techniques to determine the biological stability and quality of SOC in mineral soils. This study examined whether thermal oxidation at temperature levels between 200°C and 400°C, combined with evolving gas analysis and isotope ratio mass spectrometry, is capable of identifying SOC pools with differing biological stability in mineral soils. Soil samples from three sites being under Miscanthus (C4-plant) cultivation for more than 17 years following former agricultural cropland (only C3-plant) cultivation were used. Due to natural shifts in 13C content, young and labile Miscanthus-derived SOC could be distinguished from stable and old C3-plant-derived SOC. The proportion of Miscanthus-derived SOC increased significantly with increasing temperatures up to 350°C in bulk soil samples, indicating increasing oxidation of labile and young SOC with increasing temperatures. Use of density fractions to validate the thermally oxidized SOC from bulk soil samples revealed that the thermal oxidation patterns did not reflect the biological stability of SOC. The suggested biologically labile particulate organic carbon (light fraction from density fractionation) was clearly enriched in Miscanthus-derived young SOC. The thermal oxidation patterns, however, revealed preferential oxidation of these biologically labile fractions not at low temperatures, but rather at higher temperatures. The reverse was found for the biologically stable mineral-associated density fraction (heavy fraction). Based on different soil types, it was concluded that the thermal stability of SOC between 200°C and 400°C is not a suitable indicator of the biological stability of SOC and, thus, thermal oxidation is not capable of fractionating SOC pools with differing biological stability.