Geoinformation analysis of soil cover protection in the Arctic Zone of the Russian Federation

The representativeness of the soil diversity in the network of nature protected areas of the Russian Arctic was calculated on the basis of the Soil Map of the Russian Federation, 1:2.5 M scale by using geoinformation analysis. The authors estimated soil cover composition and soil contours areas using the ArcView GIS system. They have identified 90 different soils and soil complexes in the Arctic zone of Russia, 30 of them belong to the Arctic and tundra soils and occupy 47% of total Russian Arctic zone area. In the nature reserves and national parks territory, 48 different soils and soil complexes have been identified, 15 of them belong to the group of arctic and tundra soils, which occupy 60% of the area of protected areas. The investigation shows that currently the existing system of the Arctic protected areas is characterized by high representation of the taxonomic soil diversity (the representativeness indicator is 94%). The only soil type, Arctic Gleezem (Turbic Criosols), is not territorial protected within its typical distribution areas. To optimize the system of Arctic protected areas, the authors propose to adjust the boundaries of the existing nature protected areas in the Anadyr River basin, as well as to consider the possibility of organizing a protected area in the southern part of the Novaya Zemlya Archipelago.

Metaplasmidome-encoded functions of Siberian low-centered polygonal tundra soils

Plasmids have the potential to transfer genetic traits within bacterial communities and thereby serve as a crucial tool for the rapid adaptation of bacteria in response to changing environmental conditions. Our knowledge of the environmental pool of plasmids (the metaplasmidome) and encoded functions is still limited due to a lack of sufficient extraction methods and tools for identifying and assembling plasmids from metagenomic datasets. Here, we present the first insights into the functional potential of the metaplasmidome of permafrost-affected active-layer soil—an environment with a relatively low biomass and seasonal freeze–thaw cycles that is strongly affected by global warming. The obtained results were compared with plasmid-derived sequences extracted from polar metagenomes. Metaplasmidomes from the Siberian active layer were enriched via cultivation, which resulted in a longer contig length as compared with plasmids that had been directly retrieved from the metagenomes of polar environments. The predicted hosts of plasmids belonged to Moraxellaceae, Pseudomonadaceae, Enterobacteriaceae, Pectobacteriaceae, Burkholderiaceae, and Firmicutes. Analysis of their genetic content revealed the presence of stress-response genes, including antibiotic and metal resistance determinants, as well as genes encoding protectants against the cold.

Rainfall Alters Permafrost Soil Redox Conditions, but Meta-Omics Show Divergent Microbial Community Responses by Tundra Type in the Arctic

Soil anoxia is common in the annually thawed surface (‘active’) layer of permafrost soils, particularly when soils are saturated, and supports anaerobic microbial metabolism and methane (CH4) production. Rainfall contributes to soil saturation, but can also introduce oxygen, causing soil oxidation and altering anoxic conditions. We simulated a rainfall event in soil mesocosms from two dominant tundra types, tussock tundra and wet sedge tundra, to test the impacts of rainfall-induced soil oxidation on microbial communities and their metabolic capacity for anaerobic CH4 production and aerobic respiration following soil oxidation. In both types, rainfall increased total soil O2 concentration, but in tussock tundra there was a 2.5-fold greater increase in soil O2 compared to wet sedge tundra due to differences in soil drainage. Metagenomic and metatranscriptomic analyses found divergent microbial responses to rainfall between tundra types. Active microbial taxa in the tussock tundra community, including bacteria and fungi, responded to rainfall with a decline in gene expression for anaerobic metabolism and a concurrent increase in gene expression for cellular growth. In contrast, the wet sedge tundra community showed no significant changes in microbial gene expression from anaerobic metabolism, fermentation, or methanogenesis following rainfall, despite an initial increase in soil O2 concentration. These results suggest that rainfall induces soil oxidation and enhances aerobic microbial respiration in tussock tundra communities but may not accumulate or remain in wet sedge tundra soils long enough to induce a community-wide shift from anaerobic metabolism. Thus, rainfall may serve only to maintain saturated soil conditions that promote CH4 production in low-lying wet sedge tundra soils across the Arctic.

Untargeted Exometabolomics Provides a Powerful Approach to Investigate Biogeochemical Hotspots with Vegetation and Polygon Type in Arctic Tundra Soils

Rising temperatures in the Arctic have led to the thawing of tundra soils, which is rapidly changing terrain, hydrology, and plant and microbial communities, causing hotspots of biogeochemical activity across the landscape. Despite this, little is known about how nutrient-rich low molecular weight dissolved organic matter (LMW DOM) varies within and across tundra ecosystems. Using a high-resolution nano-liquid chromatography-mass spectrometry (LC/MS) approach, we characterized the composition and availability of LMW DOM from high-centered polygons (HCP) and low-centered polygons (LCP) with Eriophorum angustifolium or Carex aquatilis as the dominant vegetation. Over 3000 unique features (i.e., discrete mass/charge ions) were detected; 521 were identified as differentially abundant between polygonal types and 217 were putatively annotated using high mass accuracy MS data. While polygon type was a strong predictor of LMW DOM composition and availability, vegetation and soil depth were also important drivers. Extensive evidence was found for enhanced microbial processing at the LCP sites, which were dominated by Carex plant species. We detected significant differences between polygon types with varying aboveground landscape features or properties, and hotspots of biogeochemical activity, indicating LMW DOM, as quantified by untargeted exometabolomics, provides a window into the dynamic complex interactions between landscape topography, vegetation, and organic matter cycling in Arctic polygonal tundra soils.