不同成土模式下黑土有机质热稳定性剖面分异特征
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作者单位:

1.土壤与农业可持续发展国家重点实验室(中国科学院南京土壤研究所);2.中国科学院大学;3.湖泊与环境国家重点实验室(中国科学院南京地理与湖泊研究所);4.中国科学院流域地理学重点实验室(中国科学院南京地理与湖泊研究所)

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国家自然科学基金项目(42130715)资助


Vertical Variations of Thermal Stability of Soil Organic Matter in Black Soils under Different Pedogenetic Modes
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Affiliation:

1.State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences;2.State Key Laboratory of Lake Science and Environment, Institute of Geography and Limnology, Chinese Academy of Sciences;3.University of Chinese Academy of Sciences;4.Key Laboratory of Watershed GeographicScience, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences

Fund Project:

Supported by the National Natural Science Foundation of China(No. 42130715)

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    摘要:

    土壤有机质(soil organic matter,SOM)含量及其稳定性是评价土壤质量的重要指标,热重分析法在反映SOM含量与热稳定性方面显示出了较好的潜力而受到重视。探究不同成土模式下黑土SOM热稳定性在剖面尺度的分异规律及影响因素,可以为黑土资源保护与碳固定提供理论参考。本研究在东北典型黑土区采集了相对稳定地形条件下(平坦)自然发育的3个典型黑土剖面和非稳定地形条件下(有地表侵蚀和沉积)受侵蚀堆积过程影响的2个黑土剖面,采用热重分析法,基于不同温度区间的质量损失,分别以Exo1(200~350℃区间的质量损失)和Exo2(350~550℃区间质量损失)代表热易分解SOM和热稳定SOM,以微分热重曲线及热重参数指标(Exo1/Exo2和TG-T50)表征不同土壤剖面的SOM热稳定性分异特征,并结合傅里叶红外光谱讨论了SOM化学稳定性剖面分异特征。结果表明:稳定地形下自然发育的黑土,热易分解SOM(Exo1)含量相较于热稳定SOM(Exo2)含量随深度下降更快,Exo1/Exo2随深度减小,TG-T50随深度增加,脂肪族碳/芳香族碳减少,SOM稳定性随深度增加。非稳定地形条件下,黑土SOM热稳定性并未随深度表现出规律性下降趋势,存在深层SOM含量和Exo1/Exo2高于表层的现象,这主要是由于复杂的地表历史过程导致母质和SOM来源不同。本研究证实了热重分析法在反映SOM稳定性方面的适用性。黑土中SOM稳定性的剖面变化在很大程度上受成土模式的制约,而成土模式与地貌稳定性密切相关。侵蚀过程携带的大量热易分解SOM在坡面下部及流域沉积地形部位堆积,由于埋藏作用,这些热易分解SOM可以长期存在于深层土壤中。然而,非稳定地形区域一旦再遭侵蚀,这些埋藏的不稳定SOM很可能再次启动分解过程,同样可以导致大量埋藏的“老碳”被释放,成为黑土区碳排放的“热点”。

    Abstract:

    【Objective】Soil organic matter (SOM) content and its stability are important indexes to evaluate soil quality. Thermogravimetric analysis has gained attention due to its good performance in reflecting SOM content and SOM stability. The objective of this paper is to explore the vertical variation patterns of SOM thermal stability in black soils under different pedogenetic modes. The causes for these variations are also explored. This study will provide a theoretical reference for the protection of black soil resources and carbon sequestration. 【Method】Black soils of two major pedogenetic modes, i.e., naturally developed mode and depositional mode were selected for comparison. The former one included three typical black soils under stable topographic conditions (flat terrain) and the latter one included two black soils affected by erosional-depositional processes under unstable topographic conditions (with surface erosion and sedimentation) in the typical black soil area of Northeast China. Thermogravimetric analysis was used as a tool to evaluate SOM thermal stability. Two SOM fractions were recognized based on mass loss in responding to different temperature intervals, with Exo1 (mass loss during 200~350 ℃) representing thermally labile SOM and Exo2 (mass loss during 350~550 ℃) representing thermally stable SOM. In addition, derivative thermogravimetry curves and two thermogravimetric parameters including Exo1/Exo2 and TG-50 were adopted to characterize the variations of SOM thermal stability in different soil profiles. Fourier transform infrared spectroscopy was used to assess SOM chemical stability. 【Result】For naturally developed black soils from the stable land surface, the content of thermally labile SOM (Exo1) decreased at a higher rate with depth than that of thermally stable SOM (Exo2). With the increase of depth, Exo1/Exo2 decreased, TG-T50 increased, and aliphatic C/aromatic C decreased, indicating that the SOM of naturally developed black soils tended to be thermally stable with depth. Under unstable geomorphic settings, on the contrary, the thermal stability of SOM did not show a regular decrease trend with depth, and the content of SOM and Exo1/Exo2 in deeper layers could be higher than those in the surface layer. This was mainly due to the different land surface histories that caused variations in sources of soil parent material and SOM. 【Conclusion】This study confirmed the usefulness of thermogravimetric analysis in reflecting SOM stability. Spatial variations in SOM stability in black soils were largely conditioned by a pedogenetic mode which was largely related to geomorphic stability. We found that depositional landscape positions tended to stack a large amount of labile SOM, which was carried by erosional processes. This occurs both at hillslope and watershed scales. These thermally unstable SOMs could be preserved in the deep soil for a long time, due to the blocking effect of burial. Once eroded, however, these blocked labile SOMs are easily decomposed, which may also lead to the release of a large amount of buried ""old carbon"" and become the ""hot spot"" of carbon emissions in the black soil area.

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龚可杨,杨 飞,隆 浩,谷 俊,张甘霖.不同成土模式下黑土有机质热稳定性剖面分异特征[J].土壤学报,2024,61(3). DOI:10.11766/trxb202211180627 GONG Keyang, YANG Fei, LONG Hao, GU Jun, ZHANG Ganlin. Vertical Variations of Thermal Stability of Soil Organic Matter in Black Soils under Different Pedogenetic Modes[J]. Acta Pedologica Sinica,2024,61(3).

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  • 收稿日期:2022-11-18
  • 最后修改日期:2023-04-11
  • 录用日期:2023-05-08
  • 在线发布日期: 2023-05-08
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