Metal-organic interactions identified as a key factor in carbon cycling, improving predictions under climate change

September 30, 2026

The global annual amount of carbon dioxide (CO₂) released through the microbial decomposition of soil organic carbon is estimated to be approximately five times greater than anthropogenic CO₂ emissions, highlighting the importance of understanding how climate change affects soil CO₂ release dynamics.

A research group consisting of Assistant Professor Hirohiko Nagano and doctoral student Yuri Suzuki of the Institute of Science and Technology and Graduate School of Science and Technology, Niigata University, together with researchers from Kyushu University, Okayama University, the Forestry and Forest Products Research Institute of the National Research and Development Agency Forest Research and Management Organization, Tohoku University, the Acid Deposition and Oxidant Research Center, and Hokkaido University, conducted laboratory incubation experiments using surface soils and buried humic horizons collected from forests in Hokkaido. Buried humic horizons are former surface soils that became buried in deeper layers due to past volcanic ash deposition.

The results demonstrated that repeated cycles of extreme drying and rewetting conditions, which are expected to become more frequent as climate change increases the occurrence of extreme weather events such as heavy rainfall and drought, substantially increased CO₂ release from the soils. In particular, in buried humic horizons, the increase in CO₂ release was far greater than microbial biomass alone could explain, suggesting that drying-rewetting cycles may accelerate the breakdown of reactive metal-organic complex components, which have traditionally been regarded as an important mechanism for stabilizing soil carbon.

These findings support the research group's previous study published in 2025 (Suzuki, Nagano et al. 2026 SOIL, https://doi.org/10.5194/soil-11-35-2025). They are expected to improve predictions of carbon cycling under climate change, where considerable uncertainty remains, and to improve projections of future global environmental change.

Dr. Nagano pointed out that extreme weather phenomena are becoming more evident due to global warming. Furthermore, he said the results of this research will provide a detailed explanation of how extreme weather affects soil CO2 release, helping improve the accuracy of future global-environment prediction models. In the future, they plan to conduct impact assessments and mechanism verification in outdoor environments, in addition to further detailed research on mechanisms for the DWCs-induced increase in CO2 releases across soils worldwide.

Publication Details

Journal: Progress in Earth and Planetary Science (PEPS)
Title: An evaluation on contribution of organo–metal complexes to enhanced soil CO₂ release during drying–rewetting cycles using buried humic horizon soils
Authors: Yuri Suzuki, Syuntaro Hiradate, Jun Koarashi, Mariko Atarashi-Andoh, Kazuki Suzuki, Masataka Nakayama, Yukiko Abe, Kouki Hikosaka, Hirofumi Kajino, Hiroyuki Sase, Rieko Urakawa, Hirohiko Nagano
Doi: 10.1186/s40645-026-00843-6

News release

The article was released in  EurekAlert, the online publication of the American Association for the Advancement of Science.

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