Research from Cornell University has revealed critical insights into how soil microbes interact with plant materials, affecting carbon cycling and potentially influencing climate change. Published on December 10, 2023, in the journal Nature Communications, the study highlights how soil molecular diversity shifts during the decomposition of dead plants, a process essential for understanding carbon storage and release.
The study shows that as microbes decompose plant litter, molecular diversity initially increases over the first month, before plateauing and declining thereafter. This finding may hold significant implications for efforts to combat climate change by enhancing soil carbon retention. The research team, led by Johannes Lehmann, a professor of soil and crop sciences, emphasizes the importance of determining whether it is possible to retain more carbon in soil or even increase carbon stocks.
In a statement, Lehmann noted, “This is a hugely important question: can we lose less carbon from soil, or can we even increase our soil carbon stocks, which will help regulate CO2 in the atmosphere?” He underscored that even minor changes in soil organic carbon can have substantial effects on atmospheric carbon levels.
The first author of the paper, Rachelle Davenport, a former graduate student in Lehmann’s lab, has transitioned to an independent research consultant role. The study involved collaboration among 11 co-authors from seven institutions across six U.S. states and the Netherlands, supported by various public and private grants, including those from Cornell.
Historically, scientists believed that soil organic carbon primarily accumulated due to resistant plant materials. However, a pivotal paper published in 2011, co-authored by Lehmann, challenged this notion. It proposed that soil organic carbon results from complex interactions within ecosystems, including those with soil microorganisms. The authors called for new experimental approaches to explore mechanisms that either promote carbon storage or facilitate its release.
Building on this foundation, the current research provides empirical evidence that plant decomposition increases soil molecular diversity, peaking at 32 days post-decomposition. “It’s been a long time coming, since 2011, and has required a series of papers and experiments,” Lehmann stated. “We now have some empirical evidence that plant decomposition does increase molecular diversity, if only for a short time.”
To assess molecular diversity, the researchers employed high-resolution mass spectrometry to analyze organic matter extracted from soil using water. Notably, this study is the first to utilize “18O heavy water” to track changes in soil molecular composition due to microbial activity. Davenport explained that traditional methods using labeled carbon or nitrogen could skew results since they often involve feeding microbes glucose, which does not accurately reflect their natural consumption patterns.
Collaboration with the Environmental Molecular Sciences Laboratory in Richland, Washington, played a crucial role in developing this innovative method. Davenport’s research was supported by a Graduate Research Grant from Cornell Atkinson in 2022, enabling her to involve undergraduate student Caleb Levitt in measuring soil carbon dioxide emissions and monitoring the effects of decomposition on organic matter diversity.
The next phase of this research will investigate whether increased diversity among soil molecules, microorganisms, and minerals can enhance carbon storage in soils. If confirmed, strategies could be developed to promote this diversity, particularly through agricultural and forestry management practices. Lehmann emphasized that understanding these dynamics is vital for addressing climate change.
Funding for this research came from a combination of internal Cornell grants and external support from the U.S. National Institute for Food and Agriculture and the Pacific Northwest National Laboratory.
