New Research Uncovers Fungi's Pivotal Role in Soil Carbon Cycling

The soil beneath our feet is a dynamic, living ecosystem made up of a complex network of microorganisms. Fungi and bacteria keep the planet’s ecological balance in check by maintaining soil health.

Scientists have long assumed that bacteria were the primary drivers in soil carbon cycling and decomposition processes because of their diverse metabolic capabilities. However, a recent study has revealed that fungi influence soil carbon loss more than bacteria, altering our understanding of soil ecology and its impact on climate change. 

Understanding the role of fungi and bacteria in soil carbon dynamics

One major dynamic in soil health is carbon cycling, which occurs when microorganisms consume organic matter and convert it into soil carbon, a significant component of fertile soil. Carbon cycling significantly impacts climate because soil acts as a carbon reservoir and keeps carbon stored in the ground, making it less readily available to be released back into the atmosphere as a greenhouse gas. In fact, the earth’s soil holds around 2,500 gigatons of carbon – three times the amount found in the atmosphere and four times more than what’s found in all living plants and animals.

Soil carbon loss is a crucial part of the carbon cycle. Carbon that has been stored in the soil is released back into the atmosphere, often as carbon dioxide. Fungi and bacteria help accelerate the decomposition of new plant material added to the soil, which helps quicken the decomposition of older stored carbon – a process known as the ‘priming effect.’

On the flip side, this process also contributes to carbon storage. Soil aggregates are small clusters of soil particles that are bound together to create the soil’s structure. They are essential for maintaining soil health by helping it retain water, cycle nutrients, and exchange gasses.

These aggregates also trap carbon, which slows down its release into the atmosphere, ensuring that not all carbon is immediately lost, as it would greatly contribute to greenhouse gas emissions. The balance between carbon release and storage in soil is a delicate ecological process that is closely tied to climate regulation, which is why it’s so important to research and understand the roles of different microorganisms in this cycle. 

Background of study

The study’s primary goal was to determine how soil bacteria and fungi differently affect soil carbon. To do so, researchers collected soil samples and treated them with biocides to selectively suppress microbe activity. Then, they added two types of organic materials: glucose, to represent simple carbon sources, and wheat root biomass, for more complex carbon compounds.

This allowed them to observe how bacteria and fungi interacted with these different carbon sources. During a 16-day period, the researchers closely monitored the soil response to the addition of organic materials and the suppressed microbial activity. To better understand how much carbon was being used up by microbes and how it was being stored in the soil, they measured soil respiration, microbial biomass, and how much added carbon was broken down (1).

Key findings

The study’s primary finding is that fungi have a greater influence than bacteria in contributing to soil carbon loss. Although bacteria were initially more active in decomposing simple carbon sources like glucose, the researchers discovered that fungi play an overall more significant role in the long-term decomposition of complex materials like wheat root biomass.

Fungi were also found to be more important than bacteria in forming soil aggregates. This is due to their network of hyphae, which acts as a binding agent that holds together soil particles, creating stable aggregates. By challenging the traditional view of how these different microbes impact carbon cycling and decomposition in the soil, the results of the study open up new ways for researchers to consider soil management and climate change mitigation strategies. 

Steps towards a greener future

The new recognition of fungi’s dominant role in carbon cycling can lead to evolved strategies that focus more on promoting fungal activity to support carbon sequestration. Additionally, by understanding fungi’s priming effect on soil, researchers can develop methods to stabilize carbon release and storage.

Based on the study’s findings, future research should examine how to balance fungi-induced carbon optimally. A greater understanding of how different soil management techniques may guide future research into developing more sustainable practices to ensure as much carbon remains locked in the soil as possible.

References

1. Husain, Hana, Claudia Keitel, and Feike A. Dijkstra. 2024. “Fungi Are More Important than Bacteria for Soil Carbon Loss through Priming Effects and Carbon Protection through Aggregation.” Applied Soil Ecology 195 (March): 105245. https://doi.org/10.1016/j.apsoil.2023.105245.