Nitrous oxide (N₂O) is one of the most important greenhouse gas causing global warming. At the same time, it also participates in many photochemical reactions in the atmosphere, destroying the atmospheric ozone layer. In terrestrial ecosystems, soil is an important source for N₂O emissions. The N₂O in the soil mainly comes from the transformation of available nitrogen mediated by various microorganisms. 

Arbuscular mycorrhizal (AM) fungus is a widely distributed soil fungus in terrestrial ecosystems, it can enhance the nutrient uptake of the host plant through its hyphae network, improve the host plant's stress resistance, and improve the physical and chemical properties of the soil. It is generally believed that AM fungi themselves do not have the saprophyte ability and are unlikely to be direct producers or consumers of N₂O, but they have the ability to absorb active nitrogen in the soil and interact with other soil microorganisms to affect the production of N₂O from the soil. 

In order to better explore how AM fungi regulate the production and emission of N₂O from the soil, researchers from the Kunming Institute of Botany of the Chinese Academy of Sciences (KIB/CAS), based on indoor experiments, set up a microcosm experiment under controlled environment to address this knowledge gap.  

In this experiment, two independent soil environments were established, which were either allowed (AM) or prevented (NM) access by AMF hyphae. Soil physicochemical properties, N₂O flux, the diversity of bacterial communities, and the abundance of key genes responsible for N₂O production were assessed in both treatments over three months.  

Results showed that the presence of AMF significantly decreased N₂O emissions from agricultural soils in the first month, and the abundance of key genes responsible for denitrification significantly decreased in AM treatments, indicating that the regulation of N₂O emissions is transmitted by AMF-induced changes in the denitrification process.  

A structural equation model further revealed that AMF indirectly influenced N₂O emissions by altering the abundance of N metabolism-related genes, rather than by altering soil chemical properties or the diversity of bacterial communities.  

Thus, the research proposed a possible mechanism by which AMF can regulate denitrification activities and therefore N₂O emissions from agricultural soils. 

Results were published online title "Arbuscular mycorrhizal fungi potentially regulate N₂Oemissions from agricultural soils via altered expression of denitrification genes" in Science of The Total Environment. 

This work was funded by the Yunnan Fundamental Research Projects and the National Natural Science Foundation of China. 

Fig. 1. Graphical abstract of general design and major findings of this research. (Image by KIB)

Fig. 2. Structural equation model demonstrating the possible effects of AM fungi on N₂O emssion from the soil. (Image by KIB)