Responses of CH4 flux and microbial diversity to changes in rainfall amount and frequencies in a wet meadow in the Tibetan Plateau

Abstract

Global climate change scenarios forecast an increasing occurrence frequency of extreme precipitation events in the Qinghai-Tibet Plateau, events that likely will result in increasing amounts of annual rainfall. Increased precipitation and changes in its frequency may influence CH4 production. However, few studies have reported the responses of CH4 flux and soil microbes to increases in the amount and frequency of precipitation in alpine wet meadows. In this study, we experimentally altered the amount and frequency of precipitation events during the plant growing season (May to September) in 2019 at a wet meadow in the Qinghai-Tibet Plateau. All treatments included ambient rain (CK) plus 25 mm of extra water for each irrigation event but with different irrigation frequency (i.e., weekly (DF1), biweekly (DF2), every three weeks (DF3) and every four weeks (DF4)). Compared with CK (rainfall is 600 mm from May to September), the increase in rainfall frequency and amount not only affected the bacterial community structure and relative abundances of dominant genera in the soil, but also increased aboveground biomass and soil water-filled pore space (WFPS), and ultimately promotes CH4 emission. We also found that CH4 flux was positively correlated with soil temperature, easily-oxidizable organic carbon, particulate organic carbon, WFPS and ammonium nitrogen. In contrast, CH4 flux was negatively correlated with bulk density, microbial biomass carbon and dissolved organic carbon contents. Furthermore, among biological factors, vegetation biomass indirectly affected CH4 emissions by affecting the substrate supply of methanogens and the transport capacity of CH4 flux. Redundancy analysis showed that the CH4 flux was positively correlated with Acidobacteria, and negatively correlated with Proteobacteria. This study suggests that changes in rainfall amount and frequency in the future will lead to the increase in CH4 flux and will impact wet meadow carbon-sink function by affecting soil microbial abundance and community structure.