Diurnal variation in methane emissions in relation to plants and environmental variables in the Inner Mongolia marshes

摘要

Plants and environmental variables are of importance for methane (CH_4) emission from soils to the atmosphere. To understand the key factors controlling CH_4 emission in temperate wetlands, we performed field measurements in the Inner Mongolia marshes to compare the diurnal CH_4 fluxes between summer and winter, between a sandy site and an organic site, and between the wet meadow and the waterlogged habitat of each site, (ⅰ) In the summer, we found apparent diurnal patterns in CH_4 emission with unique peaks. For the sandy site, temperatures and water table were mediated to some degree by solar radiation, and thus their overall effect was noted in a diurnal cycle of CH_4 flux. Plant photosynthesis greatly affected the mechanisms of CH_4 production, oxidation and transport, resulting in a diurnal variation of CH_4 emission with a peak in the late afternoon and the lowest value immediately prior to sunrise of the next day. In the organic site, plant-mediated CH_4 transport, together with the absence of a significant relationship between CH_4 flux and environmental variables, indicated that diurnal CH_4 flux was determined by vascular plants, (ⅱ) In the winter, we found slight double peaks in CH_4 emissions in the sandy site but no diurnal variation rhythm in the organic site. The slight double peaks coincided with the maximal temperatures.