Decoupled carbon and nitrogen mineralization in soil particle size fractions of a forest topsoil
Decoupled carbon and nitrogen mineralization in soil particle size fractions of a forest topsoil
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DOI：
10.1016/j.soilbio.2014.08.001
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发表时间：
2014-11-01
影响因子：
9.7
通讯作者：
Koegel-Knabner, Ingrid
中科院分区：
文献类型：
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作者：
Bimueller, Carolin;Mueller, Carsten W.;Koegel-Knabner, Ingrid
为了更好地了解土壤中碳和氮的矿化作用是如何联系在一起的，我们进行了长期的培养实验，并比较了土壤中碳和氮的动态变化。从德国Tuttlingen附近的山毛榉林地采集的Rendzic Leptosol表土被分为三个粒度类别：砂土(2000-20亩)、粉土(20-2亩)和粘土(粘土和粉土)。各组分占土壤有机碳总量的比例分别为10.4%(砂质组分)、8.8%(粘粒组分)和4.4%(粉质组分)。然而，氮素矿化受分级过程(Sigma组分和散体土壤)的影响，并遵循粘土&粉砂&砂的顺序。分级增加了比表面积，因此提供了辅助矿物表面，这允许新的结合，特别是富氮的化合物，除了通过阳离子交换固定氨。由较低的代谢商表明，与计算的各组分之和相比，散体土壤中微生物的碳矿化效率更高。在粘粒组分中，碳矿化速率、盐析有机碳含量、微生物量碳和氮含量在培养结束时显著下降。这表明，在粘土部分，有机碳不能用于微生物的降解，微生物对碳的强烈限制导致了随后的氮固定被抑制。密度分馏表明，沙粒中的有机质主要是以轻质形式存在的颗粒状有机质，其中含有部分分解的植物残留物。粘土组分中的有机质主要吸附在矿物表面。砂粒和粘粒中的有机质主要以O/N-烷基C为主，表现出较低的顽固性，但有机质的C/N比随着粒径的减小而变窄。我们的结果表明，在土壤中与矿物相关的部分中，碳和氮的矿化是解偶联的。含碳组分和含氮组分与矿物基质的特殊相互作用强烈地调节了成矿动力学。因此，单独考虑有机物的C/N或烷基C/O/N-烷基C比率作为植物残渣分解的指标是不够的。综合考虑C/N和烷基C与O/N-烷基C的比值，可以第一次预测植物残渣的分解程度。然而，在有机质主要由空间不可达性和有机-矿物相互作用稳定的部分中，生物有效性不能用这些比率来解释，但可以用培养的方法来检验。(C)2014爱思唯尔有限公司。保留所有权利。
To better understand how carbon and nitrogen mineralization are linked in soils, we conducted a long-term incubation experiment and compared carbon and nitrogen dynamics in the bulk soil and in soil fractions. Topsoil of a Rendzic Leptosol from a beech forest site near Tuttlingen, Germany, was separated into three particle size classes: sand (2000-20 mu m), silt (20-2 mu m), and clay ( clay > silt. The fractions respired between 10.4% (sand fraction), 8.8% (clay fraction) and 4.4% (silt fraction) of total soil organic carbon. However, nitrogen mineralization was affected by the fractionation procedure (Sigma fractions < bulk soil) and followed the order clay > silt > sand. Fractionation increased the surface area and hence provided accessory mineral surfaces, which allowed new binding of especially nitrogen-rich compounds, in addition to ammonium fixation via cation exchange. As indicated by lower metabolic quotients, microbial carbon mineralization was more efficient in the bulk soil compared to the calculated sum of fractions. In the clay fraction, carbon mineralization rates, salt extractable organic carbon contents, and microbial biomass carbon and nitrogen contents declined strongly towards the end of the incubation. This indicates that in the clay fraction, organic carbon was not available for microbial degradation and that microorganisms were strongly carbon-limited causing a subsequent inhibition of nitrogen immobilization. Density fractionation revealed that organic matter in the sand fraction consisted mainly of particulate organic matter present as light material containing partly decomposed plant remnants. The organic matter in the clay fraction was mostly adsorbed on mineral surfaces. Organic matter in the sand and in the clay fraction was dominated by O/N-alkyl C indicating low recalcitrance, but the C/N ratio of organic matter narrowed with decreasing particle size. Our results suggest that carbon and nitrogen mineralization are decoupled in the mineral-associated fractions of the soil. The specific interactions of both carbon and nitrogen containing components with the mineral matrix strongly modulate the mineralization dynamics. Therefore, isolated considerations of C/N or alkyl C to O/N-alkyl C ratios of organic matter are insufficient as indicators for decomposition in plant residues. The combined consideration of C/N and alkyl C to O/N-alkyl C ratios provides a first inipression about the degree of decomposition in plant residues. However, bioavailability in fractions where organic matter is mainly stabilized by spatial inaccessibility and by organo-mineral interactions cannot be explained by these ratios, but can be examined by an incubation approach. (C) 2014 Elsevier Ltd. All rights reserved.