Symbiotic relationships between soil fungi and plants reduce N2O emissions from soil

Abstract

N 2 O is a potent greenhouse gas involved in the destruction of the protective ozone layer in the stratosphere and contributing to global warming. The ecological processes regulating its emissions from soil are still poorly understood. Here, we show that the presence of arbuscular mycorrhizal fungi (AMF), a dominant group of soil fungi, which form symbiotic associations with the majority of land plants and which influence a range of important ecosystem functions, can induce a reduction in N 2 O emissions from soil. To test for a functional relationship between AMF and N 2 O emissions, we manipulated the abundance of AMF in two independent greenhouse experiments using two different approaches (sterilized and re-inoculated soil and non-mycorrhizal tomato mutants) and two different soils. N 2 O emissions were increased by 42 and 33% in microcosms with reduced AMF abundance compared to microcosms with a well-established AMF community, suggesting that AMF regulate N 2 O emissions. This could partly be explained by increased N immobilization into microbial or plant biomass, reduced concentrations of mineral soil N as a substrate for N 2 O emission and altered water relations. Moreover, the abundance of key genes responsible for N 2 O production (nirK) was negatively and for N 2 O consumption (nosZ) positively correlated to AMF abundance, indicating that the regulation of N 2 O emissions is transmitted by AMF-induced changes in the soil microbial community. Our results suggest that the disruption of the AMF symbiosis through intensification of agricultural practices may further contribute to increased N 2 O emissions.

Soil biodiversity and soil community composition determine ecosystem multifunctionality

“…2). This demonstrates that the simplification of soil biotic communities alters nitrogen transformation processes in the soil, resulting in increased emission of N 2 O, which is an important greenhouse gas (28).…”

Carbon and phosphorus exchange may enable cooperation between an arbuscular mycorrhizal fungus and a phosphate‐solubilizing bacterium

“…Other studies have demonstrated that AMF repress certain groups of bacteria and fungi in a microbial community (Filion et al, 1999;Nuccio et al, 2013;Bender et al, 2014) but enhance others (Nuccio et al, 2013;Bender et al, 2014). The exact mechanisms behind these interactions are unknown, although several suggestions have been proposed, including: niche competition for nutrients (Christensen & Jakobsen, 1993;Veresoglou et al, 2011), physical interactions including the ability to attach to AMF hyphae (Toljander et al, 2006;Scheublin et al, 2010), and manipulation of the community via direct or indirect influences of AMF hyphal exudation (Filion et al, 1999;Toljander et al, 2007).…”

“…For two unrelated species, reciprocity between two partners can maintain their cooperation (Harcombe, 2010), and several lines of indirect evidence suggest that reciprocity may maintain cooperation between AMF and associated soil microbes. AMF hyphae do not benefit all microbes; indeed, they inhibit some (Nuccio et al, 2013;Bender et al, 2014). By contrast, the stimulated microbes usually have potentially positive effects on AMF fitness (Scheublin et al, 2010;Nuccio et al, 2013).…”

The Role of Soil Microbes in Promoting Plant Growth

“…This could partly explain that AMF inhibited AOB growth and limited ammonia oxidation, thus, reducing the content of NO 3 - (Bollmann et al, 2002). The published paper also showed that AMF could induce a reduction in N 2 O emissions in soil by increasing N immobilization into plant biomass, reducing the concentrations of mineral soil N (Bender et al, 2014). In addition, the abundance of N 2 O production was negatively correlated with AMF abundance, whereas N 2 O consumption was positively, indicating that the regulation of N 2 O emissions influenced by AMF changes in soil microbial community.…”