The Synergism between Methanogens and Methanotrophs and the Nature of their Contributions to the Seasonal Variation of Methane Fluxes in a Wetland: The Case of Dajiuhu Subalpine Peatland

Abstract

Wetland ecosystems are the most important natural methane (CH₄) sources, whose fluxes periodically fluctuate. Methanogens (methane producers) and methanotrophs (methane consumers) are considered key factors affecting CH₄ fluxes in wetlands. However, the symbiotic relationship between methanogens and methanotrophs remains unclear. To help close this research gap, we collected and analyzed samples from four soil depths in the Dajiuhu subalpine peatland in January, April, July, and October 2019 and acquired seasonal methane flux data from an eddy covariance (EC) system, and investigated relationships. A phylogenetic molecular ecological networks (pMENs) analysis was used to identify keystone species and the seasonal variations of the co-occurrence patterns of methanogenic and methanotrophic communities. The results indicate that the seasonal variations of the interactions between methanogenic and methanotrophic communities contributed to CH₄ emissions in wetlands. The keystone species discerned by the network analysis also showed their importance in mediating CH₄ fluxes. Methane (CH₄) emissions in wetlands were lowest in spring; during this period, the most complex interactions between microbes were observed, with intense competition among methanogens while methanotrophs demonstrated better cooperation. Reverse patterns manifested themselves in summer when the highest CH₄ flux was observed. Methanoregula formicica was negatively correlated with CH₄ fluxes and occupied the largest ecological niches in the spring network. In contrast, both Methanocella arvoryzae and Methylocystaceae demonstrated positive correlations with CH₄ fluxes and were better adapted to the microbial community in the summer. In addition, soil temperature and nitrogen were regarded as significant environmental factors to CH₄ fluxes. This study was successful in explaining the seasonal patterns and microbial driving mechanisms of CH₄ emissions in wetlands.

摘要

湿地生态系统是甲烷(CH₄)最重要的天然来源,其排放呈现周期性变化规律。产甲烷菌和甲烷氧化菌是介导湿地CH₄循环的重要功能菌群,然而,产甲烷菌和甲烷氧化菌群落的共现模式尚不明晰。于是,本文在2019年1月、4月、7月和10月中旬采集了神农架大九湖亚高山泥炭湿地4个深度土层的土壤样本,利用涡度相关系统收集了CH₄通量数据。运用分子生态网络分析方法鉴定关键物种并分析大九湖湿地产甲烷菌和甲烷氧化菌群落共现模式的季节性变化规律。结果表明,产甲烷菌和甲烷氧化菌群落相互作用关系的季节性变化对湿地CH₄排放具有显著影响,由分子网络识别出的关键物种具有调节CH₄通量的重要作用。在春季,微生物间的相互作用关系最为复杂,产甲烷菌群落间呈现较为激烈的竞争关系而甲烷氧化菌群落间则呈现较好的合作关系,湿地CH₄排放量最低;与之相反,夏季CH₄排放量最高。Methanoregula formicica与CH₄通量呈负相关关系且在春季网络中占据最大的生态位,而Methanocella arvoryzae和Methylocystaceae与CH₄通量呈正相关关系且在夏季网络中占据较大的生态位。此外,土壤温度和土壤氮盐含量是影响CH₄通量的重要环境因素。本研究为揭示湿地CH₄排放季节性变化的微生物调控机理提供理论依据。