Seasonally saturated wetlands are hydrologically dynamic ecosystems that provide various ecosystem services; however, their variable hydrologic conditions may promote greenhouse gas emissions. The extent to which wetlands produce and emit greenhouse gases is intimately tied to the underlying microbial community. We established a linear transect spanning a hydrologic gradient on the margins adjacent to five seasonally saturated wetlands to characterize how water level, saturation duration, and frequency of wet-dry cycles influenced the soil and methane-cycling microbial community composition. We found that the soil and methane-cycling microbial community diversity and structure were strongly related to water level changes and saturation duration but not saturation frequency. Soils that experienced inundation or saturation for more than 50% of the year harbored a soil microbial composition distinct from soils that were rarely saturated or inundated. While soils closer to the wetland basin supported a higher relative abundance of methanogens, methane-oxidizing microbes were present across the entire topographic gradient; however, the composition shifted from a primarily anaerobic to aerobic methanotroph community. Findings suggest that soil and methane cycling microorganisms are influenced by the soil’s hydrologic conditions, with methane producers being restricted to specific ranges and methane oxidizers able to occur under a variety of hydrologic conditions. The mechanisms driving methane oxidation by the latter, however, may depend on the hydrologic conditions.

中文翻译：

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水文条件影响季节性饱和湿地土壤和甲烷循环微生物种群

季节性饱和湿地是提供各种生态系统服务的水文动态生态系统；然而，它们多变的水文条件可能会促进温室气体排放。湿地产生和排放温室气体的程度与潜在的微生物群落密切相关。我们在与五个季节性饱和湿地相邻的边缘建立了一个跨越水文梯度的线性断面，以表征水位、饱和持续时间和干湿循环频率如何影响土壤和甲烷循环微生物群落组成。我们发现土壤和甲烷循环微生物群落多样性和结构与水位变化和饱和持续时间密切相关，但与饱和频率无关。一年中超过 50% 的时间都经历过淹没或饱和的土壤含有不同于很少饱和或淹没的土壤的土壤微生物组成。虽然靠近湿地盆地的土壤支持相对丰度更高的产甲烷菌，但在整个地形梯度中都存在甲烷氧化微生物；然而，组成从主要厌氧转变为好氧甲烷氧化菌群落。研究结果表明，土壤和甲烷循环微生物受土壤水文条件的影响，甲烷生产者被限制在特定范围内，而甲烷氧化剂能够在各种水文条件下发生。然而，后者驱动甲烷氧化的机制可能取决于水文条件。