Spatial and molecular variations in forest topsoil dissolved organic matter as revealed by FT-ICR mass spectrometry

Ming Sheng; Shuang Chen; Cong-Qiang Liu; Qinglong Fu; Donghuan Zhang; Wei Hu; Junjun Deng; Libin Wu; Ping Li; Zhifeng Yan; Yong-Guan Zhu; Pingqing Fu

doi:10.1016/j.scitotenv.2023.165099

Spatial and molecular variations in forest topsoil dissolved organic matter as revealed by FT-ICR mass spectrometry

Sci Total Environ. 2023 Oct 15:895:165099. doi: 10.1016/j.scitotenv.2023.165099. Epub 2023 Jun 26.

Authors

Ming Sheng¹, Shuang Chen¹, Cong-Qiang Liu², Qinglong Fu³, Donghuan Zhang¹, Wei Hu¹, Junjun Deng¹, Libin Wu¹, Ping Li⁴, Zhifeng Yan¹, Yong-Guan Zhu⁵, Pingqing Fu⁶

Affiliations

¹ Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin, 300072, China.
² Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin, 300072, China. Electronic address: liucongqiang@tju.edu.cn.
³ School of Environment Studies, China University of Geosciences, Wuhan 430074, China.
⁴ LAPC, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
⁵ Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
⁶ Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin, 300072, China. Electronic address: fupingqing@tju.edu.cn.

PMID: 37379928
DOI: 10.1016/j.scitotenv.2023.165099

Abstract

Forest soils cover about 30 % of the Earth's land surface and play a fundamental role in the global cycle of organic matter. Dissolved organic matter (DOM), the largest active pool of terrestrial carbon, is essential for soil development, microbial metabolism and nutrient cycling. However, forest soil DOM is a highly complex mixture of tens of thousands of individual compounds, which is largely composed of organic matter from primary producers, residues from microbial process and the corresponding chemical reactions. Therefore, we need a detailed picture of molecular composition in forest soil, especially the pattern of large-scale spatial distribution, which can help us understand the role of DOM in the carbon cycle. To explore the spatial and molecular variations of DOM in forest soil, we choose six major forest reserves located in different latitudes ranging in China, which were investigated by Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). Results show that aromatic-like molecules are preferentially enriched in DOM at high latitude forest soils, while aliphatic/peptide-like, carbohydrate-like, and unsaturated hydrocarbon molecules are preferentially enriched in DOM at low latitude forest soils, besides, lignin-like compounds account for the highest proportion in all forest soil DOM. High latitude forest soils have higher aromatic equivalents and aromatic indices than low latitude forest soils, which suggest that organic matter at higher latitude forest soils preferentially contain plant-derived ingredients and are refractory to degradation while microbially derived carbon is dominant in organic matter at low latitudes. Besides, we found that CHO and CHON compounds make up the majority in all forest soil samples. Finally, we visualized the complexity and diversity of soil organic matter molecules through network analysis. Our study provides a molecular-level understanding of forest soil organic matter at large scales, which may contribute to the conservation and utilization of forest resources.

Keywords: Dissolved organic matter; FT-ICR MS; Forest soil; Molecular composition; Network analysis.