Microbial contribution to SOM quantity and quality in density fractions of temperate arable soils
Microbial contribution to SOM quantity and quality in density fractions of temperate arable soils
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DOI：
10.1016/j.soilbio.2014.12.002
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发表时间：
2015-02-01
影响因子：
9.7
通讯作者：
Thiele-Bruhn, Soeren
中科院分区：
文献类型：
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作者：
Ludwig, Marie;Achtenhagen, Jan;Thiele-Bruhn, Soeren
土壤有机质的形成在很大程度上取决于微生物的活动。更重要的是，最新研究发现微生物坏死块本身是SOM的重要来源，并发现微生物产物可以启动和促进长期稳定SOM的形成。本研究的目的是研究不同稳定性池中微生物对SUM的贡献及其对SUM质量的影响。因此，采用多钨酸钠对4种性质差异很大的可耕地土壤进行密度分选，将其分为游离和封闭颗粒有机质（fPOM、oPOM < 1.6 g cm（-3）和oPOM < 2.0 g cm(-3)）和矿物伴生有机质（MOM > 2.0 g cm(-3)）。采用源内热解场电离质谱（Py-HMS）对各组分进行了表征。确定了各组分的主要SUM化合物类别，并进一步推导了SUM性能（多分散性、热稳定性）。通过碳水化合物的己糖与戊糖比值和C-4-C-26与C-26-C-36脂肪酸比值估算微生物源输入对耕地土壤有机质的贡献。此外，通过扫描电子显微镜（SEM）对选定的样品进行了研究，以可视化结构作为OM起源的指标。结果表明，尽管样品在土壤性质上存在显著差异，但SUM的组成具有可比性，所有土壤类型和所有密度组分中几乎50%的可识别SUM化合物被分配给酚类、木质素单体和烷基芳体。最显著的特征是MOM的高碳水化合物含量和POM馏分的高脂含量。定性特征，如多分散性或热稳定性一般不能分配到特定的化合物，密度分数或不同的平均停留时间。土壤碳水化合物中只有微生物来源部分与高SUM热稳定性相关（r(2) = 0.63**, n = 39）。微生物来源的碳水化合物和脂肪酸都在MOM中富集，表明微生物和植物来源的相对投入对耕地SUM的相对贡献随着密度的增加而增加，因此特别是MOM的热稳定性增加。然而，总体上微生物对土壤总养分的贡献在所有密度分数中都很高；估计碳水化合物的平均比例约为1:1。尽管从活微生物中释放生物分子，但扫描电镜显示微生物质量（生物量和坏死质量）是稳定SUM的重要来源，并且随着密度的增加而增加。(C) 2014 Elsevier Ltd.版权所有。
The formation of soil organic matter (SOM) very much depends on microbial activity. Even more, latest studies identified microbial necromass itself being a significant source of SOM and found microbial products to initiate and enhance the formation of long-term stabilized SOM. The objectives of this study were to investigate the microbial contribution to SUM in pools of different stability and its impact on SUM quality. Hence, four arable soils of widely differing properties were density-fractionated into free and occluded particulate organic matter (fPOM, oPOM < 1.6 g cm(-3) and oPOM < 2.0 g cm(-3)) and mineral associated organic matter (MOM > 2.0 g cm(-3)) by using sodium polytungstate. These fractions were characterized by in-source pyrolysis-field ionization mass spectrometry (Py-HMS). Main SUM compound classes of the fractions were determined and further SUM properties were derived (polydispersity, thermostability). The contribution of microbial derived input to arable soil OM was estimated from the hexose to pentose ratio of the carbohydrates and the ratio of C-4-C-26 to C-26-C-36 fatty acids. Additionally, selected samples were investigated by scanning electron microscopy (SEM) for visualizing structures as indicators for the origin of OM. Results showed that, although the samples differed significantly regarding soil properties, SUM composition was comparable and almost 50% of identifiable SUM compounds of all soils types and all density fractions were assigned to phenols, lignin monomers and alkylaromatics. Most distinguishing were the high contents of carbohydrates for the MOM and of lipids for the POM fractions. Qualitative features such as polydispersity or thermostability were not in general assignable to specific compounds, density fractions or different mean residence times. Only the microbial derived part of the soil carbohydrates could be shown to be correlated with high SUM thermostability (r(2) = 0.63**, n = 39). Microbial derived carbohydrates and fatty acids were both enriched in the MOM, showing that the relative contribution of microbial versus plant-derived input to arable SUM increased with density and therefore especially increased MOM thermostability. Nevertheless, the general microbial contribution to arable SUM is suggested to be high for all density fractions; a mean proportion of about 1:1 was estimated for carbohydrates. Despite biomolecules released from living microorganisms, SEM revealed that microbial mass (biomass and necromass) is a considerable source for stable SUM which is also increasing with density. (C) 2014 Elsevier Ltd. All rights reserved.