Photo: Stefano Manzoni
Spatial heterogeneity in soils contributes to soil organic carbon persistence.
Photo: Stefano Manzoni

In an article published July 27 in Nature Geoscience, with Johannes Lehmann at Cornell University as lead author and with Stefano Manzoni at Stockholm University as one of the co-authors, the authors argue that scientists should develop new models that more accurately reflect the carbon-storage processes beneath our feet, in order to effectively draw down atmospheric carbon dioxide.

Managing soils properly could allow stabilizing carbon in soils, thus mitigating climatic changes. However, it is not easy to identify management strategies that ensure efficient carbon stabilization. In the article the researchers argue that we need to ‘think like a decomposer’ to define effective carbon sequestration strategies.

Three types of challenges

Microbial decomposers in soils face three types of challenges, which is referred to as ‘functional complexities’—soil organic matter is chemically diverse (requiring metabolically costly enzymes to break down), it is often out of reach (physically separated from the microorganisms), and its availability varies strongly through time (depending on environmental conditions).

Stefano Manzoni
Stefano Manzoni

“Because microbial activity promotes soil organic matter decomposition and decreases carbon persistence, we suggest that management strategies that make microbial life more challenging will also improve carbon persistence. For example, using cover crops and rotations in agricultural fields increases chemical diversity in the plant residues, which in turn can promote carbon persistence in soils. Similarly, tillage should be avoided to maintain the spatial distancing between organic matter and microorganisms, which also promotes carbon persistence,” said Stefano Manzoni.

Developing new mathematical tools

Modeling and thus prediction of the effects of spatial heterogeneity in soils (the second of the complexities discussed in the article) is particularly challenging. While intuitively simple, the idea that organic carbon located far from microorganisms is more persistent, is not easy to describe mathematically. This is the problem that Arjun Chakrawal (a PhD student in Stefano Manzoni´s lab) is tackling. He has developed mathematical tools to link the spatial distribution of organic carbon to the capacity of microorganisms to degrade it. With these tools, he provided strong theoretical support for the idea that spatial heterogeneity promotes carbon persistence. Read more here.

Need for new soil carbon-persistence models

The international, interdisciplinary group of scientists propose the creation of new soil carbon-persistence models through the lens of “functional complexity” – the interplay between time and space in soil carbon’s changing molecular structure.
With new models, scientists believe they can find out exactly how sequestration works. It could then be properly reflected in the next assessment of the United Nations Intergovernmental Panel on Climate Change (IPCC) – which likely will address drawing down atmospheric carbon.

Article in Nature Geoscience: Persistence of soil organic carbon caused by functional complexity

Read article at Cornell University website.