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Soil microbiome plays a significant role in the development of the soil profile and the implementation of key soil biochemical processes. Observed Arctic warming creates significant environmental risks, since permafrost soils contain a huge amount of organic matter, which is in potential risk to be released in the form of greenhouse gases. This work is aimed to investigate the microbiomes in soils of mature tundra and anthropogenically affected areas of the Yamal region using a high-throughput sequencing approach. The taxonomic analysis of the soil microbiomes revealed 33 bacterial and archaeal phyla, among which the dominant were Proteobacteria, Acidobacteria, Actinobacteria, Bacteroides, Chloroflexi, Cyanobacteria, Firmicutes, Gematimonadetes, Patescibacteria, Plantomycetes, Thaumarchaeota, Verrucomicrobia, and WPS-2. The analysis of alpha and beta diversities revealed that undisturbed soil is completely different from anthropogenically affected ones in terms of microorganism biodiversity. Soils of the urban zone of Salekhard were found to be different with regard to the number of operational taxonomic units and beta diversity. Herein the microbiome in the upper and lower layers of soil developed under strong technogenic influence (M19) was unequal both in quality and in quantity. At the same time, soils developed in the recreational zone of Salekhard showed less differentiation profile of microbiome (former crop field and former vegetable garden soils). Microbial communities in the mature tundra soil showed less differentiated microbiome composition.

This work describes the microbial community structure of the continuously revegetated chronosequence of a former sand quarry, which demonstrates a unique example of nearly complete soil restoration in less than 100 years. Samples were collected at five time points (0, 3, 30, 70 years and mature soil) from the entire set of soil horizons, revealing the history of pedogenesis. Real-time PCR was applied to quantitatively describe the bacterial and archaeal communities. High-throughput sequencing of the bacterial and archaeal V4 variable region of the 16S rRNA gene was used to identify abundant microbial taxa. A beta-diversity analysis revealed that the prokaryotic community structure responded strongly to the processes of organic matter accumulation and the corresponding evolution of the soil into discrete horizons. Changes in soil microbiota in the course of soil profile evolution revealed three groups of prokaryotes, which tended to accumulate in the specific soil horizons and might be associated with the certain soil-forming processes, including plant roots growth. This research showed the heuristic potential of soil horizon profiling in microbiological studies as opposed to the formal depth-dependent separation of the soil layers. The results allowed us to trace the relationship between the structure of the soil prokaryotic community and the peculiarities of the evolution of the podzolic soil profile as well as to identify the microbial indicators and drivers of primary pedogenesis. [ABSTRACT FROM AUTHOR]

The collapse of collective farming in Russia after 1990 led to the abandonment of 23% of the agricultural area. Microbial biomass is a transit pool between fresh and soil organic matter; therefore, structural changes in soil microbial community determine the carbon cycle processes caused by self-restoration of arable lands after abandonment. Here, we assessed the influence of monthly changes in moisture and temperature on the bacterial community structure and abundance in Retisols under long-term abandoned cropland. Two periods with pronounced differences in bacterial properties were revealed: the growing period from March to September and the dormant period from October to February. The growing period was characterized by higher bacterial abundance and diversity compared to the dormant period. The relative abundances of the bacterial community dominants (Alpha-, Gamma- and Deltaproteobacteria, subgroup 6 of phylum Acidobacteria) did not change significantly over the year, either in total or active communities. The relative abundances of Bacteroidetes and Verrucomicrobia increased in the growing period, whereas Actinobacteria and Chloroflexi were more abundant in the dormant period. The microbial gene abundances positively correlated with soil and air temperature, but not with soil moisture. Thus, the seasonal dynamics of soil microbial communities are closely related to soil temperature and should be considered when assessing carbon cycles in abandoned lands. [ABSTRACT FROM AUTHOR]