Soil microorganisms and methane emissions in response to short-term warming field incubation in Svalbard.

Introduction: Global warming is caused by greenhouse gases (GHGs). It has been found that the release of methane (CH) from Arctic permafrost, soil, ocean, and sediment is closely related to microbial composition and soil factors resulting from warming over several months or years. However, it is unclear for how long continuous warming due to global warming affects the microbial composition and GHG release from soils along Arctic glacial meltwater rivers.

Methods: In this study, the soil upstream of the glacial meltwater river (GR) and the estuary (GR-0) in Svalbard, with strong soil heterogeneity, was subjected to short-term field incubation at 2°C ( temperature), 10°C, and 20°C. The incubation was carried out under anoxic conditions and lasted for few days. Bacterial composition and CH production potential were determined based on high-throughput sequencing and physiochemical property measurements.

Results: Our results showed no significant differences in bacterial 16S rRNA gene copy number, bacterial composition, and methanogenic potential, as measured by mcrA gene copy number and CH4 concentration, during a 7- and 13-day warming field incubation with increasing temperatures, respectively. The CH concentration at the GR site was higher than that at the GR-0 site, while the gene was lower at the GR site than that at the GR-0 site.

Discussion: Based on the warming field incubation, our results indicate that short-term warming, which is measured in days, affects soil microbial composition and CH concentration less than the spatial scale, highlighting the importance of warming time in influencing CH release from soil. In summary, our research implied that microbial composition and CH emissions in soil warming do not increase in the first several days, but site specificity is more important. However, emissions will gradually increase first and then decrease as warming time increases over the long term. These results are important for understanding and exploring the GHG emission fluxes of high-latitude ecosystems under global warming.