Isolating organic carbon fractions with varying turnover rates in temperate agricultural soils – A comprehensive method comparison
Isolating organic carbon fractions with varying turnover rates in temperate agricultural soils – A comprehensive method comparison
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DOI：
10.1016/j.soilbio.2018.06.025
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发表时间：
2018-10
影响因子：
9.7
通讯作者：
C. Poeplau;A. Don;J. Six;M. Kaiser;D. Benbi;C. Chenu;M. F. Cotrufo;D. Derrien;P. Gioacchini-
中科院分区：
文献类型：
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作者：
C. Poeplau;A. Don;J. Six;M. Kaiser;D. Benbi;C. Chenu;M. F. Cotrufo;D. Derrien;P. Gioacchini-
土壤有机碳(SOC)分级对于从机理上理解和模拟土壤有机质分解和稳定过程是至关重要的。它通常的目的是将大量SOC分离成具有不同周转率的馏分，但缺乏实现这一目标的方法的全面比较。在这项研究中，参与实验室总共测试了20种不同的SOC分级方法，以测试它们是否适合分离不同周转率的组分，使用来自三个试验点的农业土壤，这些试验点的植被在22-36年前从C3到C4变化。对C4衍生碳的浓缩进行了追踪，并将其用作馏分中周转率的替代。采用物理(密度、大小)和化学(氧化、萃取)分级相结合的方法被认为是将SOC分离成具有不同周转率的分级的最有效的方法。密度分馏分离出的粗光SOC是C4碳富集度最高的组分，而NaOCl萃取后的抗氧化SOC是C4碳富集度最低的组分。令人惊讶的是，即使在温带气候下种植了36年的C4作物，也没有任何方法能够分离出周转率超过76%的一部分，这对模型中最活跃的植物来源碳库的联系构成了挑战。密度为>；2.8 g cm−3的颗粒表现出与抗氧化有机碳相似的C4碳浓缩，突显了倍半氧化物对有机碳稳定的重要性。粘土和粉粒(<；50 μm)对有机碳稳定的重要性也得到了证实。粒度分级明显优于集料分级，这是因为较大的集料包含较小的集料和不同大小的有机质颗粒，其周转率不同。使用包含不同标准的评价方案来确定分离具有不同周转率的分数的最合适方法，以及与特定选择相关的潜在好处和权衡。我们的研究结果对选择适合于农业土壤分级的方法(S)有很大的帮助。
Fractionation of soil organic carbon (SOC) is crucial for mechanistic understanding and modeling of soil organic matter decomposition and stabilization processes. It is often aimed at separating the bulk SOC into fractions with varying turnover rates, but a comprehensive comparison of methods to achieve this is lacking. In this study, a total of 20 different SOC fractionation methods were tested by participating laboratories for their suitability to isolate fractions with varying turnover rates, using agricultural soils from three experimental sites with vegetation change from C3 to C4 22–36 years ago. Enrichment of C4-derived carbon was traced and used as a proxy for turnover rates in the fractions. Methods that apply a combination of physical (density, size) and chemical (oxidation, extraction) fractionation were identified as most effective in separating SOC into fractions with distinct turnover rates. Coarse light SOC separated by density fractionation was the most C4-carbon enriched fraction, while oxidation-resistant SOC left after extraction with NaOCl was the least C4-carbon enriched fraction. Surprisingly, even after 36 years of C4 crop cultivation in a temperate climate, no method was able to isolate a fraction with more than 76% turnover, which challenges the link to the most active plant-derived carbon pools in models. Particles with density >2.8 g cm−3showed similar C4-carbon enrichment as oxidation-resistant SOC, highlighting the importance of sesquioxides for SOC stabilization. The importance of clay and silt-sized particles (<50 μm) for SOC stabilization was also confirmed. Particle size fractionation significantly outperformed aggregate size fractionation, due to the fact that larger aggregates contain smaller aggregates and organic matter particles of various sizes with different turnover rates. An evaluation scheme comprising different criteria was used to identify the most suitable methods for isolating fractions with distinct turnover rates, and potential benefits and trade-offs associated with a specific choice. Our findings can be of great help to select the appropriate method(s) for fractionation of agricultural soils.