Responses of soil nitrogen fixation to Spartina alterniflora invasion and nitrogen addition in a Chinese salt marsh.

Ming Xiao,Xiao Xu,Zhexue Quan,Min Wang,Shiyun Qiu,Jingxin Huang,Bo Li,Qing Wang,Ming Nie

doi:10.1038/srep20384

Abstract

Biological nitrogen fixation (BNF) is the major natural process of nitrogen (N) input to ecosystems. To understand how plant invasion and N enrichment affect BNF, we compared soil N-fixation rates and N-fixing microbes (NFM) of an invasive Spartina alterniflora community and a native Phragmites australis community in the Yangtze River estuary, with and without N addition. Our results indicated that plant invasion relative to N enrichment had a greater influence on BNF. At each N level, the S. alterniflora community had a higher soil N-fixation rate but a lower diversity of the nifH gene in comparison with the native community. The S. alterniflora community with N addition had the highest soil N-fixation rate and the nifH gene abundance across all treatments. Our results suggest that S. alterniflora invasion can increase soil N fixation in the high N-loading estuarine ecosystem, and thus may further mediate soil N availability.

Highlights

Promote biological invasion[22,23], and alter C/N cycling[24,25] and microbial activity[26]
S. alterniflora biomass was significantly higher than P. australis biomass at the same N level (Fig. 2a)
N-fixation rate was significantly higher in the soils of S. alterniflora communities than in those of P. australis communities (Fig. 2c)

Summary

Introduction

Promote biological invasion[22,23], and alter C/N cycling[24,25] and microbial activity[26]. In the Yangtze River estuary, for example, N enrichment stimulates CH4 emission in the S. alterniflora community but does not affect the emission in the native plant communities[27]. N enrichment stimulates N2O emissions in both invasive S. alterniflora and native P. australis communities[28]. We conducted an experimental study in the Yangtze River estuary. Because of the positive relationship between NFM and plant C input to soil[29], we hypothesized that invasive S. alterniflora relative to native P. australis has a higher simulative effect on soil N fixation. Previous studies suggest that N enrichment can affect soil N-fixation[2]. We further hypothesized that N enrichment can regulate soil N fixation after plant invasion

Methods

Results

Conclusion