Abstract:

Qilian Mountain Permafrost，located in the north of Tibet Plateau, is one of the most important permafrost regions, and it is also known as an important area for gas hydrate distribution on land in China. Previous studies showed that two main types of alpine ecosystems, including alpine meadow and alpine swamp meadow, were observed around the gas hydrate drilling area. In order to insight into the archaeal community and its distribution in the both topsoils of alpine ecosystem, the geochemical parameters and archaeal community compositions were analyzed for the soil samples collected during the early winter of 2014. The results showed that pH of the soils from alpine meadow were neutral, whereas pH of the soils from alpine swamp meadow were slightly acidic. The TOC content and methane concentration in the soils of the drilling area were significantly higher than those in the background area (non-hydrate drilling area), however, they were shown no difference when compared with those in different topsoils of alpine ecosystems in background area. The microbial cell abundance in the drilling area (except for DZ2-14Q-5T sample) was 2 to 5 folds higher than that in the background area. The archaeal biodiversity was poor in the winter seasonal topsoils, and was comprised of three archaeal groups affiliated to Crenarchaeota and three groups affiliated to Eurarchaeota. The archaeal communities from alpine meadow topsoils were dominated by Group Ⅰ.1b affiliated to Crenarchaeota, while alpine swamp meadow topsoils were dominated by Methanosarcinales affiliated to Eurarchaeota.It was inferred that the moisture in topsoils may be one of the most important reasons causing the variation of microbial cell abundances and the different compositions of archaeal communities between the both topsoils of alpine ecosystem, and the methanogenic archaea dominated in the alpine swap meadow soils was more related to the higher TOC content. The results also showed that more abundance of methanogenic archaea inhabited in the alpine swamp meadow topsoils than that in the alpine meadow topsoils. It was well known that the methanogens oxidized the organic carbon to produce methane under anaerobic conditions, contributing of one source of soil methane from biogenesis.

Key words: archaeal community, alpine ecosystem, permafrost soil, gas hydrate drilling area, Qilian Mountain