Effects of Nitrogen and Phosphorus Inputs on Soil Bacterial Abundance, Diversity, and Community Composition in Chinese Fir Plantations.

Qing Wang,Diwen Chen,Ying Huang,Junhua Ao,Yong Jiang,Weiwei Yu,Zhengrui Huang,Ali Turak,Cong Wang

doi:10.3389/fmicb.2018.01543

Abstract

Nutrient inputs to forest ecosystems significantly influence aboveground plant community structure and ecosystem functioning. However, our knowledge of the influence of nitrogen (N) and/or phosphorus (P) inputs on belowground microbial communities in subtropical forests is still unclear. In this study, we used quantitative polymerase chain reaction and Illumina Miseq sequencing of the bacterial 16S rRNA gene to investigate bacterial abundance, diversity, and community composition in a Chinese fir plantation. The fertilization regimes were as follows: untreated control (CK), P amendment (P), N amendment (N), and N with P amendment (NP). Additions of N decreased soil pH and bacterial 16S rRNA gene abundance by 3.95 (from 4.69 to 3.95) and 3.95 × 109 copies g−1 dry soil (from 9.27 × 109 to 3.95 × 109 g−1 dry soil), respectively. Bacterial richness and diversity decreased with N addition (N and NP) rather than only P input. Proteobacteria, Acidobacteria, and Actinobacteria were the major phylum across all treatments. Nitrogen addition increased the relative abundance of Proteobacteria and Actinobacteria by 42.0 and 10.5%, respectively, while it reduced that of Acidobacteria by 26.5%. Bacterial community structure in the CK and P treatments was different from that in the N and NP treatments upon principle coordinates analysis. Phosphorus addition did not significantly affect soil bacterial communities, and no interactions between N and P inputs on microbial traits were observed. Soil pH and mineral N availability appeared to have a cooperative effect on bacterial abundance and community structure, with soil pH being the key influencing factor by canonical correspondence analysis. These results indicate that inorganic N rather than P fertilization affected both bacterial abundance and community composition in subtropical forests.

Highlights

Soil nutrient inputs such as nitrogen (N) and phosphorus (P) are critical to control plant growth in tropical forest plantations (Chen et al, 2015)
Nitrogen fertilizer directly impacted mineral N availability, which were the key factors altering bacterial community composition (Figure 3), as revealed in previous studies (Zhong et al, 2015; Nie et al, 2018). These findings indicate that soil mineral N availability, which depends on N input, is essential to the bacterial community structure
Soil chemical properties and bacterial community were markedly influenced by N and/or P input in a subtropical fir plantation in southern China

Summary

Introduction

Soil nutrient inputs such as nitrogen (N) and phosphorus (P) are critical to control plant growth in tropical forest plantations (Chen et al, 2015). Nitrogen is considered as a limiting factor that influences the plant biodiversity and primary productivity in forest ecosystems (Bobbink et al, 2010; Weand et al, 2010). Chronic elevated N input has been shown to lead to many adverse impacts, including soil acidification (Guo et al, 2010; Mao et al, 2017), nutrients imbalance (Lu et al, 2010), and increased greenhouse gas emissions (IPCC, 2007). N input may result in element imbalance and further aggravate P limitation in the forest ecosystem (Tang et al, 2016). Effects of repeated N and P additions on belowground ecosystems such as soil bacterial communities in subtropical forest ecosystems remain poorly understood

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