The Structure and Species Co-Occurrence Networks of Soil Denitrifying Bacterial Communities Differ Between A Coniferous and A Broadleaved Forests.

Jie Chen,Weijun Shen,Tushou Luo,Han Xu,Yide Li,Jiajia Li

doi:10.3390/microorganisms7090361

Abstract

Acacia mangium (AM) and Pinus massoniana (PM) are widely planted in tropical regions, whereas their effects on soil microbial communities remain unclear. We did a comprehensive investigation of soil denitrifying bacterial communities in AM and PM monoculture plantations in Southern China based on the high throughput sequencing data of their functional genes: nirK, nirS, and nosZ. The average abundance of nosZ (1.3 × 107) was significantly higher than nirS (5.6 × 106) and nirK (4.9 × 105). Shannon estimator revealed a markedly higher α-diversity of nirS and nosZ communities in PM than in AM plantations. The AM and PM plantations were dominated by different nirS and nosZ taxa belonging to proteobacteria, actinobacteria, thermoleophilia, chloroflexia, and acidobacteria, while the dominant nirK taxa were mainly categorized into proteobacteria in both types of plantations. The structure of nirS and nosZ communities shifted substantially from AM to PM plantations with changes in soil moisture, NH4+, and microbial biomass nitrogen content. The species co-occurrence network of nirK community was better organized in a more modular manner compared to nirS and nosZ communities, and the network keystone species mostly occurred in PM plantations. These results indicated a highly species corporation of nirK community in response to environmental changes, especially in PM plantations. AM and PM plantations can form different soil denitrifying microbial communities via altering soil physicochemical properties, which may further affect soil N transformations.

Highlights

A large part of the natural forest has been transformed into different monoculture plantations in the tropical and subtropical regions in the past decades [1,2]
A recent study suggested that the nirS denitrifying bacteria was substantially affected by soil pH in both natural and re-vegetated subtropical forests in Southern China [51], the soil pH value was similar in the Pinus massoniana (PM) and Acacia mangium (AM) plantations
The two types of plantations had distinct structure of nirS and nosZ denitrifying bacteria, which are mainly associated with the different soil properties (i.e., microbial biomass nitrogen (MBN), NH4+, pH, and Soil water content (SWC)) between the two types of plantations

Summary

Introduction

A large part of the natural forest has been transformed into different monoculture plantations in the tropical and subtropical regions in the past decades [1,2]. The ecological effects of these plantations remain debatable. These forest managements often lead to substantial losses in forest productivity, biodiversity, and soil nutrient stocks [3,4,5,6]. Changes in forest environments are likely to be paralleled with shifts in the soil microbial communities that has potential feedbacks on the ecosystem function and ecological significance [7,8]. Establishing various types of plantations in the same region may form different soil microbial communities as a reflection of alterations in the soil environments. The majority of studies only focused on ubiquitous microorganisms [7,9,11], and the effects of different types of plantations on specific functional microorganisms responsible for N cycling are unclear

Objectives

Methods

Discussion

Conclusion