Abstract
As a typical alpine wetland on the Tibetan Plateau, the Zoige wetland processes a large carbon stock and is a hotspot of methane emission. To date, many studies have investigated the methane flux in this wetland; however, the research on the source of methane in the soils of Zoige wetland is not clear enough. In this study, we determined the dynamic characteristics of the stable carbon isotopes during the methanogenesis of Zoige wetland soil and the corresponding microbial changes. The results showed that the δ13CH4 varied between −19.86‰ and −28.32‰ and the αC ranged from 1.0029 to 1.0104 in the methanogenesis process, which suggests the dominance of acetotrophic methanogenesis. And among the increased methanogens, acetotrophic methanogens multiplied more obviously than hydrogenotrophic menthanogens. In addition, the results of structural equation models showed that the variations in stable carbon isotopes during the process were mainly affected by acetotrophic methanogens. Although the acetotrophic pathway was dominate, the varied isotope characteristics, increased methanogens and ratio of carbon dioxide to methane all showed that hydrogenotrophic and acetotrophic methanogenesis coexisted in the Zoige wetland. Overall, our study provided a detailed and definitive information to the source of methane in the soil of the Zoige wetland and laid a foundation of mechanism to the research of greenhouse gas in this alpine wetland.
Highlights
As an important greenhouse gas, methane has attracted a great deal of attention under the background of global warming
In this study, we determined the methanogenic pathways in the Zoige wetland through analysis of both stable carbon isotopes and microorganisms in the methanogenic process without any exogenous addition
Few studies have investigated the dynamic features of the methanogenesis process of the soil and revealed where the methane come from without any exogenous additions in the Zoige wetland
Summary
As an important greenhouse gas, methane has attracted a great deal of attention under the background of global warming. To investigate the methanogenic pathways in this wetland, the addition of exogenous substrates combined with microbial analysis has been used in most studies[20,21,22]. Those cannot reveal the methanogenic activity of the soil itself in the Zoige wetland. In this study, we determined the methanogenic pathways in the Zoige wetland through analysis of both stable carbon isotopes and microorganisms in the methanogenic process without any exogenous addition. The objective of this study is to find out the methane sources in the soils from the Zoige alpine wetland through monitoring the dynamics of carbon isotopic compositions and analyzing the corresponding microbial changes during the methanogenic process. The microbial variance was studied based on quantification of Mcr α-subunit genes (mcrA) and high-throughput sequencing of archaeal 16S rRNA genes
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