# Communities of Arbuscular Mycorrhizal Fungi and Their Effects on Plant Biomass Allocation Patterns in Degraded Karst Grasslands of Southwest China

## TL;DR

This study explores how arbuscular mycorrhizal fungi (AMF) influence plant biomass allocation in degraded grasslands in China, showing that AMF communities, not individual species, help plants adapt to rocky desertification stress.

## Contribution

The study reveals that AMF communities, not bacteria or other fungi, are key in mediating plant biomass allocation in degraded karst grasslands.

## Key findings

- Degraded grasslands show allometric biomass allocation, while non-degraded ones show isometric partitioning.
- AMF keystone species combinations enhance belowground biomass allocation in Festuca ovina under rocky desertification stress.
- AMF influence plant biomass allocation by altering soil pH, ALP activity, and PT4 gene expression.

## Abstract

The biomass allocation patterns between aboveground and belowground are an essential functional trait for plant survival under a changing environment. The effects of arbuscular mycorrhizal fungi (AMF) communities on plant biomass allocation, particularly in degraded Festuca ovina grasslands in ecologically fragile karst areas, remain unclear. Therefore, we conducted a field investigation combined with a greenhouse experiment to explore the importance of AMF compared to bacteria and fungi for plant biomass allocation. The results showed that plant biomass in degraded grasslands exhibited allometric biomass allocation, contrasting with isometric partitioning in non-degraded grasslands. AMF, not bacteria or fungi, were the primary microbial mediators of grassland degradation effects on plant biomass allocation based on structural equation modeling. The greenhouse experiment demonstrated that the selected AMF keystone species from the field study performed according to ecological network analysis, particularly multi-species combinations, enhanced the belowground biomass allocation of F. ovina under rocky desertification stress compared to single-species inoculations, through decreasing soil pH, enhancing alkaline phosphatase (ALP) activity, and increasing the expression level of AMF-inducible phosphate transporter (PT4). This study highlights the critical role of the AMF community, rather than individual species, in mediating plant survival strategies under rocky desertification stress.