Soil degradation influences soil bacterial and fungal community diversity in overgrazed alpine meadows of the Qinghai-Tibet Plateau

Lin Dong,Jingjing Li,Juan Sun,Chao Yang

doi:10.1038/s41598-021-91182-7

Abstract

Over half of the alpine meadows in the Qinghai-Tibet Plateau (QTP) are degraded due to human activities. Soil degradation from overgrazing is the most direct cause of grassland degradation. It is thus important to synthesize the effects of multiple soil degradation indicators on the belowground biomass of plants and soil microorganisms in the degraded QTP. We studied the diversities and structures of soil bacterial and fungal communities using soil bacterial 16S rRNA and the fungal ITS gene under four degradation gradients, D1: lightly degraded, D2: moderately degraded, D3: highly degraded, and a non-degraded control site (CK). The bacterial Shannon diversity in D3 was significantly lower than that in D1 (p < 0.001), and the bacterial richness index in D3 was significantly lower than that in D1 (p < 0.001). There was no difference in soil fungal diversity among the different degradation levels; however, soil fungal richness decreased significantly from CK to D3. The phyla Actinobacteria, Acidobacteria and the genus Mortierella were differed significantly under the four degradation gradients. Plant litter mass and root C/N ratio were important factors associated with bacterial and fungal diversity and richness. These results indicated that alpine meadow degradation can lead to variations in both microbial diversity and the potential functioning of micro-organisms in the QTP.

Highlights

Grassland degradation can produce highly negative environmental impacts, such as desertification, dust storms, and soil erosion[1]
The plant Root carbon (RC) and RC/N ratios significantly increased as the degradation level increased (p < 0.05, Table 1), while litter mass, plant root biomass (RB), and root nitrogen (RN) significantly decreased (Table 1; p < 0.05)
The soil pH, electrical conductivity (EC), and bulk density (BD) values significantly increased as the degradation level increased (p < 0.05, Table S1), while the contents of Soil water content (SWC), total carbon (TC), total nitrogen (TN), and the C/N ratio significantly decreased (p < 0.05)

Summary

Introduction

Grassland degradation can produce highly negative environmental impacts, such as desertification, dust storms, and soil erosion[1]. The changes in soil nutrient availability and plant diversity caused by alpine meadow degradation can alter the microbial community and its diversity[15]. Given the inconsistent response of soil micro-organisms to grassland degradation[22], understanding how both bacterial and fungal community composition and diversity respond to degradation, and clarifying the key soil factors related to degradation, could provide a basis for the health evaluation and management of alpine meadows in the Q TP6. There are few studies on the diversity of bacterial and fungal communities in degraded alpine meadows in the QTP, and it is unclear if soil degradation is related to the composition and structure of soil fungi. We hypothesized that (1) long-term overgrazing caused shifts in both plant and soil properties, and (2) soil degradation significantly altered bacterial and fungal diversity. The goals of this study were to (1) identify the plant root and soil properties under different degradation conditions, (2) evaluate the response of soil bacterial and fungal communities to a degraded meadow, and (3) assess the relationships between soil degradation, plant root properties, and soil microbial diversities

Objectives

Methods

Results

Discussion

Conclusion