“Because soils contain so much organic carbon, even small, incremental changes can make a big, big difference in the atmosphere and therefore for climate change.”
The study was led by Rachelle Davenport, Ph.D. ’24, formerly a graduate researcher in Lehmann’s laboratory and now an independent consultant. The international research team included 11 co-authors from seven institutions across the United States and the Netherlands, supported by several funding sources, including two Cornell grants.
Earlier scientific thinking assumed soil carbon accumulated mainly from plant compounds that were difficult to decompose. That view shifted after a landmark 2011 Nature paper co-authored by Lehmann demonstrated that soil carbon forms through interactions among microbes, organic molecules, and minerals. In 2020, Lehmann and colleagues proposed that greater molecular diversity could slow decomposition and enhance carbon storage.
The new study delivers the first direct evidence backing that idea, showing diversity peaks around day 32 of decomposition. “It’s been a long time coming, since 2011, and has required a series of papers and experiments, but we now have some empirical evidence that plant decomposition does increase molecular diversity, if only for a short time,” Lehmann said. “We still have much to learn, but this is one important piece of the bigger puzzle.”
Researchers also successfully used oxygen-18 labeled “heavy water” to trace microbial activity without disturbing natural soil conditions. “I think that method was a major success,” Davenport said. Future studies will investigate whether farming and forest management practices can boost soil diversity and increase long-term carbon storage.
Photo Credit: gettyimages-dmytro-diedov