The research is the first to leverage a global soil carbon database with state-of-the-art mathematical models to measure the relative importance of microbial processes in the soil carbon cycle at a global scale. The study’s authors found that the role microbes play in storing carbon in the soil is at least four times more important than any other process, including decomposition of organic matter. That’s important information: Earth’s soils hold three times more carbon than the atmosphere, creating a vital carbon sink in the fight against climate change.

Soils like this contain the bacteria and fungi that are the most important factor when it comes to how much carbon is stored in the soil. Photo: Stefano Manzoni.

Soil carbon dynamics have been studied for the last two centuries, but those studies were mainly concerned with how much carbon gets into the soil from leaf litter and roots, and how much is lost to the air in the form of CO2 when organic matter decomposes. But we are the first group that can evaluate the relative importance of microbial processes versus other processes,” said Yiqi Luo, professor at Cornell University, Ithaca, the paper’s senior author.

The new method estimated microbial carbon use efficiency, which tells how much carbon was used by microbes for growth versus how much was consumed for metabolism. When used for growth, carbon becomes sequestered by microbes in cells and ultimately in the soil, and when used for metabolism, carbon is released as a side product in the air as carbon dioxide, where it acts as a greenhouse gas. 

We knew from previous research that microbial carbon use efficiency is important for soil carbon and nutrient cycling, because it summarizes how soil microorganisms use organic matter. But now, in this article, we show that differences across space are fundamental to explain soil carbon distributions—more important than any other factors affecting carbon storage. We really moved the focus on soil microorganisms.” said co-author Stefano Manzoni, associate professor at the Department of Physical Geography.

The new insights point agricultural researchers toward studying farm management practices that may influence microbial carbon use efficiency to improve soil health, which also helps ensure greater food security. Future studies may investigate steps to increase overall soil carbon sequestration by microbes. Researchers may also study how different types of microbes and substrates (such as using manure or compost in fields and pastures) may influence soil carbon storage.

We are constantly working to bridge the gap between making maps of soil carbon and creating models that can actually simulate the dynamic changes in soil carbon with a high degree of accuracy. This study helps us by confirming that microbes are a key player. It is a strong argument for further improving how models simulate microbial ecology.” said co-author Gustaf Hugelius, professor at the Department of Physical Geography and vice director of the Bolin Centre for Climate Research at Stockholm University.

The study

The study, “Microbial Carbon Use Efficiency Promotes Global Soil Carbon Storage,” published May 24 in Nature and led by Feng Tao, a researcher at Tsinghua University, Beijing, describes a novel approach to better understanding soil carbon dynamics by combining a mathematical model of soil microbial processes with data assimilation and machine learning, to analyze big data related to the carbon cycle.
DOI: 10.1038/s41586-023-06042-3
https://www.nature.com/articles/s41586-023-06042-3

Contact

Stefano Manzoni, Department of Physical Geography, Stockholm University.
Phone: +46-8-674 78 02
E-post: stefano.manzoni@natgeo.su.se (engelska)

Gustaf Hugelius, Department of Physical Geography and Bolin Centre for Climate Research, Stockholm University.
Tel: +46-8-674 78 73
E-post: gustaf.hugelius@natgeo.su.se