# Phosphorus availability modifies the responses of Glomeromycotina and Mucoromycotina to nitrogen addition

## TL;DR

This study explores how adding nitrogen and phosphorus affects two types of mycorrhizal fungi in grasslands, showing that phosphorus availability strongly influences fungal communities.

## Contribution

The study reveals how phosphorus availability modifies fungal responses to nitrogen addition, highlighting interactions between nutrient availability and fungal symbiosis.

## Key findings

- Phosphorus availability strongly affects the composition of both Glomeromycotina and Mucoromycotina fungal communities.
- Nitrogen fertilization impacts both fungal groups more than phosphorus fertilization, with effects varying based on local phosphorus levels.
- Fungal community composition varies significantly among host plant species and across different sites.

## Abstract

Grassland fertilisation modifies the relationship between mycorrhizal fungi and their plant hosts. The composition and diversity of the fungal community depend on the background nutrient availability and changes in nutrient availability caused by fertilisation. We determined the effects of nitrogen and phosphorus addition at 12 sites with different background nutrient availabilities using 5 species of bait seedlings planted in the field. We studied two groups of mycorrhizal fungi – arbuscular mycorrhizal fungi (Glomeromycotina, G-AMF) and fine root endophytes (Mucoromycotina, M-FRE) – using molecular methods and light microscopy. Both fungal communities showed large differences among forb and grass host species and among individual sites. G-AMF community composition varied more along background nutrient availability gradients than with short-term fertilisation. Phosphorus availability affected the composition of both fungal communities, but nitrogen availability only affected G-AMF community composition. Nitrogen fertilisation affected both fungal communities more than phosphorus fertilisation, and the effects of nitrogen addition varied with the local phosphorus availability. Our study provides an understanding of the long-term adaptation of mycorrhizal symbiosis to nutrient availability and how it interacts with nutrient addition.

The online version contains supplementary material available at 10.1007/s00572-026-01256-5.