# Community Structure and Soil Environmental Drivers of Rhizosphere and Root Endophytic Microbiota of Polygonum divaricatum in a Temperate Grassland

## TL;DR

This study explores how soil conditions and plant roots shape the microbial communities of a grassland plant, revealing their roles in nutrient cycling and ecosystem stability.

## Contribution

The study identifies distinct microbial community structures and their environmental drivers in the rhizosphere and root endosphere of Polygonum divaricatum.

## Key findings

- Root endosphere had higher fungal diversity, while rhizosphere soils had greater bacterial diversity.
- Microbial communities responded to soil pH, organic carbon, nitrogen, and enzyme activities.
- Functional profiles showed distinct roles for rhizosphere and root endosphere microbes in nutrient metabolism and transport.

## Abstract

Grasslands are vital natural ecosystems that rely on close cooperation between plants and the microscopic life living in their roots and the surrounding soil. This study focused on a common grassland plant, Polygonum divaricatum, in the Hulunbuir Grassland to understand how different plant parts and soil conditions shape these hidden communities of bacteria and fungi. We found that plant roots act like a natural filter, allowing only certain microorganisms to live inside them, while the surrounding soil supports a different and more diverse group influenced by factors such as soil acidity and nutrient levels. Microorganisms in the soil mainly help break down organic matter, whereas those inside the roots are specialized in helping the plant absorb and transport nutrients. By revealing how these unseen partners respond to their environment, this study provides important knowledge for understanding how grasslands function. This information supports better land management and helps protect these ecosystems so they remain stable and resilient in the face of environmental change.

Understanding the ecological drivers of plant-associated microbiota is essential for predicting grassland ecosystem resilience. This study aimed to characterize the community structure, functional potential, and soil environmental drivers of rhizosphere and root endophytic microbiota associated with Polygonum divaricatum across three Hulunbuir Grassland sites. A nested sampling design was applied with three replicated plots per site, from which paired rhizosphere soil and root samples were collected. Each sample represented a composite of 15 plants, yielding six samples per site (total n = 18) and allowing the separation of compartmental and environmental effects on community assembly. P. divaricatum plays a key role in nutrient cycling and soil stability; however, its rhizosphere and root microbiomes remain poorly characterized. Fungal diversity was consistently higher in the root endosphere, whereas bacterial diversity was greater in rhizosphere soils. Fungal assemblages were dominated by Ascomycota and Mortierellomycota, primarily represented by Mortierella and Trichoderma, while bacterial communities were dominated by Actinomycetota and Pseudomonadota, enriched in Bradyrhizobium and Pseudonocardia. Community differentiation reflected strong compartmental filtering and responses to soil pH, organic carbon, nitrogen, and enzyme activities. Functional prediction indicated clear compartmental partitioning: in the rhizosphere, bacterial communities were enriched in pathways related to carbon and nitrogen metabolism and secondary metabolite biosynthesis, whereas in the root endosphere, functional profiles were more associated with transport, uptake, and fermentation; fungal communities were dominated by saprotrophic and symbiotrophic guilds. These findings demonstrate that soil biochemical gradients and host-driven filtering jointly structure the P. divaricatum microbiome, providing ecological insights into plant–microbe–soil interactions and the maintenance of grassland ecosystem stability.