Synergies between mycorrhizal fungi and soil microbial communities increase plant nitrogen acquisition

Rachel Hestrin,Johannes Lehmann,Carsten W Mueller,Edith C Hammer

doi:10.1038/s42003-019-0481-8

Abstract

Nitrogen availability often restricts primary productivity in terrestrial ecosystems. Arbuscular mycorrhizal fungi are ubiquitous symbionts of terrestrial plants and can improve plant nitrogen acquisition, but have a limited ability to access organic nitrogen. Although other soil biota mineralize organic nitrogen into bioavailable forms, they may simultaneously compete for nitrogen, with unknown consequences for plant nutrition. Here, we show that synergies between the mycorrhizal fungus Rhizophagus irregularis and soil microbial communities have a highly non-additive effect on nitrogen acquisition by the model grass Brachypodium distachyon. These multipartite microbial synergies result in a doubling of the nitrogen that mycorrhizal plants acquire from organic matter and a tenfold increase in nitrogen acquisition compared to non-mycorrhizal plants grown in the absence of soil microbial communities. This previously unquantified multipartite relationship may contribute to more than 70 Tg of annually assimilated plant nitrogen, thereby playing a critical role in global nutrient cycling and ecosystem function.

Highlights

Nitrogen availability often restricts primary productivity in terrestrial ecosystems
Plant mesocosms, Arbuscular mycorrhizal (AM) fungi, and soil microbial communities collected from an N gradient experiment to investigate how multipartite interactions influence plant N acquisition from organic matter and how these relationships respond to long-term N enrichment
Brachypodium distachyon seeds were planted in double-autoclaved sand and gravel with or without spores of the AM fungus Rhizophagus irregularis

Summary

Introduction

Nitrogen availability often restricts primary productivity in terrestrial ecosystems. Arbuscular mycorrhizal (AM) fungi form symbioses with the majority of terrestrial plants and can substantially enhance plant N acquisition from soil, thereby potentially alleviating plant N limitation and playing an important role in plant productivity and soil nutrient cycling[3,4,5,6,7,8,9]. Long-term N enrichment disrupts these synergies, resulting in diminished mycorrhizal N acquisition from organic matter These results have implications for terrestrial nutrient cycling models, agricultural management, and our understanding of ecosystem response to global change

Methods

Results

Conclusion