Microbial communities of soils and soil constructions in the Russian Arctic cities

Arctic cities attract researchers’ interest by a unique combination of extreme climatic conditions and anthropogenic pressure. Urban soils are different from natural references in terms of the formation and functioning conditions. Urban soils are very heterogeneous ranging from semi-natural soils altered by: on the urbanization to artificial soil constructions composed from different materials and mixtures. These soil constructions are mainly created to support green infrastructure and can be considered a new ecological niche for microorganisms. This research aimed to identify the microbial features of urban soils and soil constructions in Arctic cities compared to the background soils.

The studies were carried out in the recreational zones of Kola region cities: Murmansk (68.58°N, 33.03°E), Monchegorsk (67.56°N, 32.52°E), and Apatity (67.33°N, 33.24°E), different in population, operating industry, and climate. Samples were taken from different soil horizons. Soil morphological (WRB classification), physicochemical properties (density; pH; C, N content (CN analyzer) etc., including heavy metals (ICP) were assessed. Microbiological indicators included the number of archaea, bacteria, fungi genes copies (PCR real time), functional diversity (MicroResp), microbial respiration (SIR).

Four main types of urban soil disturbance of the Kola Arctic have been revealed: slightly disturbed natural podzols and podburs; disturbed urban-stratified podzols and podburs; artificially created soil constructions with evidences of soil formation; artificially created soil constructions. Disturbed urban soil profiles contain a gray-humus urban stratified horizon with a low C content, but high N content and pH values. Urban soils in Murmansk and Monchegorsk had higher contents of C and N compared to those in Apatity. Whereas in terms of the content of heavy metals (Cu, Ni) in soils of Monchegorsk was higher compared to the other cities.

Microbial communities of soils and soil constructions in the Kola Аrctic cities responded differently to the influence of urban anthropogenic factors. The microbiological parameters were significantly influenced by age, land use history, the productivity and structure of vegetation, the degree of soil cover transformation, and the level of pollution. However, general patterns identified for the microbial communities were similar for all urban soils. There was a tendency towards an increase in the functional activity and diversity of microbial communities in artificially created soil constructions compared to natural urban soils and background references. In contrast, microbial respiration was higher in natural urban soils compared to soil constructions, but no general pattern was found across cities when compared to background soils. For example, in Murmansk and Monchegorsk the values were lower compared to background soils, whereas the opposite was shown for Apatity. The number of archaea genes copy was also higher in urban soils of Apatity compared to background soils. For most chemical and microbiological parameters of urban soils, the highest values were identified in the subsoil horizons, which may be due to the presence of buried horizons, various substrates, and artifacts.

Urban soils and soil constructions can provide a niche for microorganisms, but a complex of external factors affecting them in specific conditions plays a fundamental role.

Acknowledgements This research was supported by RSF #23-17-00118 and RUDN University Strategic Academic Leadership Program.