Large‐scale evidence for microbial response and associated carbon release after permafrost thaw

Abstract

Permafrost thaw could trigger the release of greenhouse gases through microbial decomposition of the large quantities of carbon (C) stored within frozen soils. However, accurate evaluation of soil C emissions from thawing permafrost is still a big challenge, partly due to our inadequate understanding about the response of microbial communities and their linkage with soil C release upon permafrost thaw. Based on a large‐scale permafrost sampling across 24 sites on the Tibetan Plateau, we employed meta‐genomic technologies (GeoChip and Illumina MiSeq sequencing) to explore the impacts of permafrost thaw (permafrost samples were incubated for 11 days at 5°C) on microbial taxonomic and functional communities, and then conducted a laboratory incubation to investigate the linkage of microbial taxonomic and functional diversity with soil C release after permafrost thaw. We found that bacterial and fungal α diversity decreased, but functional gene diversity and the normalized relative abundance of C degradation genes increased after permafrost thaw, reflecting the rapid microbial response to permafrost thaw. Moreover, both the microbial taxonomic and functional community structures differed between the thawed permafrost and formerly frozen soils. Furthermore, soil C release rate over five month incubation was associated with microbial functional diversity and C degradation gene abundances. By contrast, neither microbial taxonomic diversity nor community structure exhibited any significant effects on soil C release over the incubation period. These findings demonstrate that permafrost thaw could accelerate C emissions by altering the function potentials of microbial communities rather than taxonomic diversity, highlighting the crucial role of microbial functional genes in mediating the responses of permafrost C cycle to climate warming.

Carbon Isotopic Evidences for Gas Hydrate Release and Its Significance on Seasonal Wetland Methane Emissions in the Qilian Mountains Permafrost

“…This nding further suggest gas hydrate release is an important source of methane emission from wetland soils in Qilian Mountain permafrost. During spring and summer, soil temperature increase and permafrost thawing promoted ourishly growing of wetland organisms and exponentially incresing of microbial communities [37][38][39] , which can lead to an increase in biogenic methane emision. Simultaneously, the permafrost started to thaw after the soil temperautre above 0℃ in the late spring and the thawing depth peaked in July and August.…”

Linkage between microbial shift and ecosystem functionality

“…Currently, microbial functional gene analysis could possibly be performed on a large scale, while the measurement for in situ permafrost C release could not. Thus, the findings of Chen et al, (2020) inspire the possible adoption of microbial functional gene information as a proxy for field potential in Earth system models to predict future climate scenarios.…”

“…Clearly, permafrost C‐climate feedbacks are determined, or at least mediated, by not only how microbes respond to permafrost thaw, but also what microbial responses mean for ecosystem functionality. Chen et al, (2020) provide experimental evidence demonstrating that increases in microbial functional diversity and C decomposition gene abundances, rather than taxonomic shifts, are associated with permafrost C release upon permafrost thaw. This work represents a valuable step towards elucidating the ecological consequences of microbial shifts, thus detangling uncertainties in understanding and predicting permafrost C‐climate feedback (Xue, Xie, et al, 2016).…”

“…With a storage of ~50% of global belowground C, permafrost thaw may trigger the greatest positive ecosystem feedback to climate change on our planet (Xue et al, 2016) due to accelerated microbial decomposition activities in soil organic matter, otherwise preserved by low temperature and water saturation. Although it has received less attention, the importance of microbial functional gene shifts, rather than taxonomic shifts, was highlighted by Chen et al, (2020). The well‐established linkage between functional genes (reflecting genetic potential) and C release via laboratory incubation (reflecting field potential) is a good start that provides clues about the magnitude of in situ permafrost C release under permafrost thaw on the basis of microbial functional gene changes.…”

“…The study by Chen et al, (2020) was conducted on the Tibetan Plateau, which has the largest high‐altitude permafrost and experiences approximately twice the warming effect as the global average. However, most current permafrost studies on global climate change have been conducted in high‐latitude rather than high‐altitude permafrost regions.…”