Decomposition decreases molecular diversity and ecosystem similarity of soil organic matter

Journal Article · 11 June 2023 · Proceedings of the National Academy of Sciences of the United States of America

DOI: https://doi.org/10.1073/pnas.2303335120 · OSTI ID:1984703

Davenport, Rachelle  ^[1]; Bowen, Benjamin P. ^[2]; Lynch, Laurel M.  ^[1]; Kosina, Suzanne M.  ^[3]; Shabtai, Itamar  ^[1]; Northen, Trent R.  ^[2]; Lehmann, Johannes  ^[4]

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1. Soil and Crop Sciences, School of Integrative Plant Sciences, Cornell University, Ithaca, NY 14850
2. Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, Metabolomics Technology Group Joint Genome Institute, Department of Energy, Walnut Creek, CA 94598
3. Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
4. Soil and Crop Sciences, School of Integrative Plant Sciences, Cornell University, Ithaca, NY 14850, Department of Global Development, Cornell University, Ithaca, NY 14850, Cornell Institute for Digital Agriculture, Cornell University, Ithaca, NY 14850, Cornell Atkinson Center for Sustainability, Cornell University, Ithaca, NY 14850

Soil organic matter (SOM) is comprised of a diverse array of reactive carbon molecules, including hydrophilic and hydrophobic compounds, that impact rates of SOM formation and persistence. Despite clear importance to ecosystem science, little is known about broad-scale controls on SOM diversity and variability in soil. Here, we show that microbial decomposition drives significant variability in the molecular richness and diversity of SOM between soil horizons and across a continental-scale gradient in climate and ecosystem type (arid shrubs, coniferous, deciduous, and mixed forests, grasslands, and tundra sedges). The molecular dissimilarity of SOM was strongly influenced by ecosystem type (hydrophilic compounds: 17%, P < 0.001; hydrophobic compounds: 10% P < 0.001) and soil horizon (hydrophilic compounds: 17%, P < 0.001; hydrophobic compounds: 21%, P < 0.001), as assessed using metabolomic analysis of hydrophilic and hydrophobic metabolites. While the proportion of shared molecular features was significantly higher in the litter layer than subsoil C horizons across ecosystems (12 times and 4 times higher for hydrophilic and hydrophobic compounds, respectively), the proportion of site-specific molecular features nearly doubled from the litter layer to the subsoil horizon, suggesting greater differentiation of compounds after microbial decomposition within each ecosystem. Together, these results suggest that microbial decomposition of plant litter leads to a decrease in SOM α-molecular diversity, yet an increase in β-molecular diversity across ecosystems. The degree of microbial degradation, determined by the position in the soil profile, exerts a greater control on SOM molecular diversity than environmental factors, such as soil texture, moisture, and ecosystem type.

• Research Organization: Cornell University, Ithaca, NY (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC), Biological and Environmental Research (BER). Biological Systems Science (BSS)
• Grant/Contract Number: AC02-05CH11231; SC0016364
• OSTI ID: 1984703
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 25 Vol. 120; ISSN 0027-8424
• Publisher: Proceedings of the National Academy of SciencesCopyright Statement
• Country of Publication: United States
• Language: English