Depression of soil nitrogen fixation by drying soil in a degraded alpine peatland

Xiaodong Zhang; Xin Jia; Haidong Wu; Jing Li; Liang Yan; Jinzhi Wang; Yong Li; Xiaoming Kang

doi:10.1016/j.scitotenv.2020.141084

Depression of soil nitrogen fixation by drying soil in a degraded alpine peatland

Sci Total Environ. 2020 Dec 10:747:141084. doi: 10.1016/j.scitotenv.2020.141084. Epub 2020 Jul 25.

Authors

Xiaodong Zhang¹, Xin Jia², Haidong Wu¹, Jing Li³, Liang Yan¹, Jinzhi Wang¹, Yong Li¹, Xiaoming Kang⁴

Affiliations

¹ Beijing Key Laboratory of Wetland Services and Restoration, Institute of Wetland Research, Chinese Academy of Forestry, Beijing 100091, China; Sichuan Zoige Wetland Ecosystem Research Station, Tibetan Autonomous Prefecture of Aba 624500, China.
² Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China.
³ Beijing Key Laboratory of Wetland Services and Restoration, Institute of Wetland Research, Chinese Academy of Forestry, Beijing 100091, China.
⁴ Beijing Key Laboratory of Wetland Services and Restoration, Institute of Wetland Research, Chinese Academy of Forestry, Beijing 100091, China; Sichuan Zoige Wetland Ecosystem Research Station, Tibetan Autonomous Prefecture of Aba 624500, China. Electronic address: xmkang@ucas.ac.cn.

PMID: 32771776
DOI: 10.1016/j.scitotenv.2020.141084

Abstract

Soil biological nitrogen fixation (BNF) represents a major pathway through which nitrogen enters pristine peatlands. Many peatlands have been undergoing human-induced changes in environmental factors, while environmental changes dramatically affect the community composition and activity of nitrogen-fixing prokaryotes (i.e., diazotrophs). However, the impact of peatland degradation on soil BNF remains unclear. By carrying out a field campaign, we examined how soil BNF varies along a natural gradient from pristine marshes to moderately-degraded meadows and sandy meadows on the Zoige Plateau. Plant and topsoil samples from four pristine marshes, three moderately-degraded meadows, and three sandy meadows were collected to determine the potential rate of nitrogen fixation (R_Nfix), abundance of the nifH gene, diazotrophic community composition, and soil and plant characteristics. Our results showed that topsoil R_Nfix varied in the range 0.018-3.00 μmol N g d.w.^-1 day^-1 (i.e. 21.74-1632.37 mg N m^-2 day^-1) across the ten sites, being lowest in sandy meadows and highest in pristine marshes. Topsoil R_Nfix and diazotrophic abundance were positively correlated with soil water content, sedge cover, plant biomass, soil organic carbon content, and total nitrogen and phosphorus contents. Soil water content, which affected most plant and soil characteristics, had dominant influences on the abundance and community structure of diazotrophs. The R_Nfix was closely correlated with the abundance of dominant diazotroph groups. The community composition of diazotrophs differed markedly among sites of different degradation levels. Proteobacteria was the most abundant diazotrophic phylum across the ten sites. Heterotrophic diazotrophs acted as the major contributor to BNF, especially in pristine marshes and moderately-degraded meadows. We conclude that soil water content was the main factor driving the depressed soil BNF during peatland degradation in Zoige, due to soil water effects on plant cover and biomass, soil organic carbon and total phosphorus, and the abundance and community structure of diazotrophs.

Keywords: Diazotroph; Meadow; Soil moisture; Zoige Plateau; nifH gene.

MeSH terms

Carbon
Nitrogen / analysis
Nitrogen Fixation*
Soil Microbiology
Soil*

Substances

Soil
Carbon
Nitrogen