Effect of Nitrogen Addition on Soil Microbial Functional Gene Abundance and Community Diversity in Permafrost Peatland.

Xiuyan Ma,Zhendi Liu,Jinli Gao,Nannan Wang,Yanyu Song,Changchun Song,Xiaofeng Cheng,Siqi Gao,Yu Du,Xianwei Wang

doi:10.3390/microorganisms9122498

Abstract

Nitrogen is the limiting nutrient for plant growth in peatland ecosystems. Nitrogen addition significantly affects the plant biomass, diversity and community structure in peatlands. However, the response of belowground microbe to nitrogen addition in peatland ecosystems remains largely unknown. In this study, we performed long-term nitrogen addition experiments in a permafrost peatland in the northwest slope of the Great Xing’an Mountains. The four nitrogen addition treatments applied in this study were 0 g N·m−2·year−1 (CK), 6 g N·m−2·year−1 (N1), 12 g N·m−2·year−1 (N2), and 24 g N·m−2·year−1 (N3). Effects of nitrogen addition over a period of nine growing seasons on the soil microbial abundance and community diversity in permafrost peatland were analyzed. The results showed that the abundances of soil bacteria, fungi, archaea, nitrogen-cycling genes (nifH and b-amoA), and mcrA increased in N1, N2, and N3 treatments compared to CK. This indicated that nitrogen addition promoted microbial decomposition of soil organic matter, nitrogen fixation, ammonia oxidation, nitrification, and methane production. Moreover, nitrogen addition altered the microbial community composition. At the phylum level, the relative abundance of Proteobacteria increased significantly in the N2 treatment. However, the relative abundances of Actinobacteria and Verrucifera in the N2 treatment and Patescibacteria in the N1 treatment decreased significantly. The heatmap showed that the dominant order composition of soil bacteria in N1, N2, and N3 treatments and the CK treatment were different, and the dominant order composition of soil fungi in CK and N3 treatments were different. The N1 treatment showed a significant increase in the Ace and Chao indices of bacteria and Simpson index of fungi. The outcomes of this study suggest that nitrogen addition altered the soil microbial abundance, community structure, and diversity, affecting the soil microbial carbon and nitrogen cycling in permafrost peatland. The results are helpful to understand the microbial mediation on ecological processes in response to N addition.

Highlights

We focused on two aspects: (1) the response of soil microbial abundance to N addition in N-limited peatland; (2) the relationship of soil substrate properties with the composition and diversity of microbial communities under N addition
Soil total carbon (TC) content was found to be in the range of 388.57 mg·g−1 to 406.53 mg·g−1
This study demonstrated that continued N addition for nine growing seasons increased the abundances of bacteria, fungi, archaea, nif H, b-amoA, and mcrA in permafrost peatland, indicating that N addition could stimulate the decomposition of soil organic matter, oxidation of ammonia, fixation of N, nitrification, and production of methane, thereby affecting soil C and N cycling

Summary

Introduction

Nitrogen (N) is the primary restricting factor for plant growth in terrestrial ecosystems [1]. The current global N deposition ranges from 0.05 to 2 g N·m−2 ·year−1 [4], and it is expected to increase 2.5-fold by the end of the current century [5]. A continuous rise in N deposition has become a global eco-environmental concern [6]. N deposition is the most vital driving factor for carbon sink in China’s terrestrial ecosystem [7]. The aggravation of N deposition has resulted in soil acidification [8]. This, in turn, has altered the composition and diversity

Methods

Discussion

Conclusion