Differences of methanogenic community, potential CH4 production and its determinants in active layer and permafrost deposits on the Tibetan Plateau

Abstract:

Permafrost thaw frequently leads to increase methane release (CH₄), further may contributing to a large extent positive terrestrial feedback to climate change. It has been suggested that the strength of this positive climate feedback depend largely on CH₄ production process driven by methanogenic archaea, which determine the potential of CH₄ emissions from ecosystems. However, previous studies mainly limited on site-scale and focused on methanogens in active layer. Little is known methanogens in permafrost on region-scale and their differences in permafrost and active layer. Also, there is poorly understood whether or not there are differences in biotic and abiotic factors regulating potential CH₄ production between permafrost and active layer. Here, based on 12 swamp meadow sites acquired form ~1000 km permafrost transect on the Tibetan Plateau, we conducted anaerobic incubation at 4℃ and combined with qPCR and high throughput sequencing as well as Random Forest analysis, revealing the differences of methanogenic community, potential CH₄ production and its determinants in permafrost and active layer. Our results showed that potential CH₄ production, the abundance of mcrA gene and richness of methanogens in permafrost significantly lower than that in active layer. Hydrogenotrophic Methanocellales was highest relative abundance in the key phylotypes of methanogens regulating CH₄ production potential in permafrost, while facultative acetoclastic Methanosarcina was highest in active layer. Our result also showed that major drivers of potential CH₄ production in permafrost different from active layer: abiotic factors (TN and DON) were major drivers of permafrost while biotic factors (the abundance of mcrA gene and richness) were main drivers of active layer. These results emphasized that differences of the properties of methanogenic community and determinants of potential CH₄ production in permafrost and active layer should be considered to Earth system model to more precisely predict the feedback of CH₄ released from permafrost region to climate warming.