Dolgikh, Andrey Vladimirovich

Ananyeva N.D., Ivashchenko K.V., Urabova S.A., Vasenev V.I., Dolgikh A.V., Gorbacheva A.Y., Dovletyarova E.A.

Ecosystem services are a modern tool of environmental assessment, planning, and design, especially in large cities. The top layer (0–10 cm) of soddy-podzolic soils (Albic Retisols) was sampled in urban forest parks of Moscow (Aleshkino, Bitsa, Lesnaya experimental dacha, Troparevo, Lianozovo, and Yugo-Zapadny) and suburban (background) forests. In total, 30 samples (6 × 5 plots) were taken in forest parks and 20 samples (4 × 5 plots) in background areas, altogether 50 samples. The contents of carbon (C); nitrogen (N); phosphorus (P); heavy metals (Pb, Cu, Ni, and Zn); nitrate nitrogen (N– $${\text{NO}}_{3}^{ - }$$ ); and C, N, and P in microbial biomass (Cmic, Nmic, and Pmic), basal (microbial) respiration were determined. The portion of Cmic, Nmic, and Pmic in the total contents of these elements in soil (Cmic/C, Nmic/N, and Pmic/P) were calculated. We suggest that the values of basal respiration, Cmic/C, Nmic/N, and Pmic/P characterizing the cycles of biophilic elements in the soil may be associated with supporting ecosystem services whereas soil pollution (heavy metals and N– $${\text{NO}}_{3}^{ - }$$ ), with ecosystem disservice. The basal respiration, Cmic/C, Nmic/N, and Pmic/P in the soils of each studied forest park were, on average, by 4–72% lower as compared with the background analogues, whereas the contents of Pb, Cu, Ni, Zn, and N– $${\text{NO}}_{3}^{ - }$$ were by 14–194% higher. According to the listed characteristics in integral index of soil (IIS, scores) is proposed to quantify their ecological state. This index in forest parks is by 32–72% lower as compared with the background analogues (IIS = 1) and reaches its maximum (0.68) in the Bitsa forest park (2208 ha) and minimum (0.28) in the Lianozovo park (44 ha).

Ivashchenko K., Gavrichkova O., Korneykova M., Vasenev V., Salnik N., Saltan N., Sarzhanov D., Babenko E., Urabova S., Slukovskaya M., Zavodskikh M., Gorbov S., Petrov D., Dolgikh A., Yu S., et. al.

The increasing popularity and recognition of citizen science approaches to monitor soil health have promoted the idea to assess soil microbial decomposition based on a standard litter sample - tea bags. Although tea bag initiatives are expanding across the world, the global datasets remain biased in regard to investigating regions and biomes. This study aimed to expand the tea bag initiative to European Russia, which remains a "white spot" on the tea bag index map. We also added urban soils into the analysis, which were underestimated previously. We compared the standard and local tea brands to explore possible adaptations of the standard approach to regions with limited access to standard tea brands. The established monitoring network included natural and urban sites in six vegetation zones along a 3000 km latitudinal gradient. There was a very close linear relationship (R2 = 0.94-0.98) in the mass loss of alternative and standard tea litter. The mass loss of green tea in soil along the latitudinal gradient showed an increasing trend from north to south. Variations in the microbial decomposition of green tea were mainly explained by the latitudinal gradient, with low soil temperature identified as key factors hampering decomposition. Mass loss of the more recalcitrant rooibos tea was mainly determined via land use, with decomposition rates on average 1.3 times higher in urban soils. This pattern was in line with higher soil temperatures and pH in urban sites compared to natural counterparts. The findings of our study could prove valuable in extending the tea bag network of soil decomposition assessment into broader territories, including urban areas. Additionally, they could facilitate the involvement of citizen science and complete the database for C cycle modeling depending on climatic conditions.

Korneykova M., Ivashchenko K., Dolgikh A., Kozlova E., Vasenev V.

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.    

Mergelov N., Zazovskaya E., Fazuldinova N., Petrov D., Dolgikh A., Matskovsky V., Golyeva A., Bichurin R., Miamin V., Dobryansky A.

Fire relentlessly modifies the belowground pool of pyrogenic carbon (PyC) in boreal ecosystems. However, only a few soils offer a consistent record of PyC accumulation. Here, we report on the Holocene-scale record of biomass burning and PyC sequestration in the paleosoils of dry topographic hollows at the Keiva ice-marginal landform. We combine soil stratigraphy, radiocarbon dating, and chemical analyses to explore the chronology and properties of macrocharcoal that accumulated in soils for millennia. The most ancient pyrogenic horizons refer to 10,700–10,200 cal BP. They contain charred remnants of well-pronounced root systems as a part of the paleosoil, suggesting enough biomass for intensive burning and significant PyC sink into soils soon after deglaciation. The major phase of woody biomass burning occurred during 7000–5000 cal BP and resulted in the abundant deposition of charcoal in topographic hollows. Soil macrocharcoal maintained a remarkably consistent concentration of total organic carbon (70.70 ± 2.96 %) over the millennial timescale. Its conservation was strengthened by burial in dry sandy soils soon after the fire. Raman spectra of the least weathered charcoal fragments of various ages indicate that intensive biomass burning occurred regularly in the Holocene. Capacity to form pyrogenic archives of Keiva II was predetermined by glacial-associated features like kettle topography and their postglacial modification. Rich PyC record of Keiva II highlights the significance of this landform for soil-based paleofire studies in eastern Fennoscandia.

Korneykova M.V., Vasenev V.I., Saltan N.V., Slukovskaya M.V., Soshina A.S., Zavodskikh M.S., Sotnikova Y.L., Dolgikh A.V.

Abstract Dynamics of soil CO2 emission, temperature, and moisture were studied during the vegetation season (from May to October) in 2021 and 2022 in the residential areas of Murmansk and Apatity cities (Murmansk oblast) in comparison with natural areas. The mean emissions from urban soils were 5–7 g C/(m2 day) in summer and 1–2 g C/(m2 day) in spring and fall. Temperature was the main abiogenic factor that determined the seasonal dynamics of soil respiration (R2 from 0.4 to 0.7, p < 0.05; Q10 temperature coefficient up to 2.5), while excess moisture had a limiting effect, especially in the natural areas. The heterogeneity of hydrothermal conditions and the content of biophilic elements determined the differences in the mean CO2 emission between natural and urban soils. For the natural soils, the mean temperature was lower and the moisture content was higher than for urban areas, which determined the lowest emission values. Among urban sites, higher CO2 emissions were found for tree and shrub vegetation sites.

Zamotaev I.V., Gracheva R.G., Konoplianikova Y.V., Dolgikh A.V., Karelin D.V., Belonovskaya E.A., Dobryansky A.S., Mikheev P.V.

Abstract Soils formed in treatment facilities of sugar beet factories in the forest-steppe zone of Kursk oblast were studied. Technogenic factors of soil formation associated with the industrial sugar beet activity and post-technogenic processes during the abandonment of treatment facilities are considered. The alternation of settling ponds and the earth walls separating them are the main factors determining “cellular” pattern of the soil cover. The mode of inflow and discharge and the composition of wastewater, as well as the duration of the abandonment of settling ponds determine the specifics of soils forming in the bottoms of the ponds. Mucky–humus quasi-gley stratified soils (Calcaric Gleysol) are formed in operating settling ponds under the periodic impact of sewage mixed with other wastes. When calcareous sewage sludge (press mud) is previously removed from abandoned ponds, dark-humus quasi-gley soils (Gleyic Cambisol) are formed in 30 years in the presence of perched water table, and quasi-gley zooturbated Chernozems are developed in 40 years under the conditions of periodic moistening. Soil formation in settling ponds with preserved sewage sludge and abandoned 20 years ago is noticeably intensive only in the upper 10–15 cm, and properties of the stratified sediment are preserved below. Dark-humus technogenic artistratified soils (Spolic Technosols) are identified there. Typical dark-humus soils (Eutric Cambisols (Organotransportic) are formed on earth walls in about 50–60 years, and incompletely developed strongly alkaline technogenic pelozems (Spolic Technosols (Transportic)) are formed on earth walls covered with calcareous sewage sludge; these soils consist of the virtually unchanged mixed material of technogenic sediments. All soils are alkaline and strongly alkaline and rich in organic matter, carbonates, phosphates, nutrients and some heavy metals from wastewater. According to the combination of properties, the soils of the sugar industry treatment facilities have no direct natural analogues in the central chernozemic region and are a vivid example of soils forming under extreme conditions of resource excess.

Vasenev V.I., Varentsov M.I., Sarzhanov D.A., Makhinya K.I., Gosse D.D., Petrov D.G., Dolgikh A.V.

Against the background of global warming, urban ecosystems are becoming increasingly vulnerable to climate stresses. Strategies for climate adaptation developed for almost every major city in the world pay considerable attention to urban green infrastructure as a nature-oriented solution for carbon sequestration. However, the influence of urban climate on the spatiotemporal variability of CO2 emissions from urban soils remains poorly understood, which can lead to inaccurate estimates and inflated expectations of urban green infrastructure in the context of carbon neutrality. In 2019–2022, studies of the dynamics of CO2 emission with parallel monitoring of soil temperature and soil moisture were carried out at three green infrastructure sites of Moscow differing in their mesoclimatic conditions. For each object, plots with different types of vegetation were compared, which made it possible to assess the internal heterogeneity of soil and microclimatic conditions. Soil temperature determined up to 70% of the total variance of CO2 emissions. Mean annual soil temperature in the city center was almost 3–6°C higher than that in the peripheral areas (10–12 km from the center), whereas soil moisture in the center was 10–15% lower. Soils under lawns and shrubs were, on average, 1–2°C warmer and 10–15% wetter than soils under trees. The annual CO2 emission from soils under lawns was, on average, 20–30% higher than that from soils under tree plantations in the same area. At the same time, the differences between the plots with the same vegetation in the center and on the periphery reached 50%, which reflects the high vulnerability of urban soil carbon stocks to mesoclimatic anomalies and the high risks of a further increase in CO2 emissions from urban soils against the background of climate change.

Velichko N.V., Rabochaya D.E., Dolgikh A.V., Mergelov N.S.

Abstract The research is devoted to the analysis of biodiversity of Antarctic cyanobacteria in hypolithic organic-accumulative horizons of soils in the Larsemann Hills oasis. Studies of fouling glasses by the methods of light and confocal microscopy, as well as by fluorescent in situ hybridization, indicate that filamentous forms predominate among cyanobacteria in the upper layers of Antarctic hypolithic microbial communities. Strains of the genera Nostoc, Halotia, Leptolyngbya, Plectolyngbya, and Phormidesmis, as well as some new and previously undescribed cyanobacteria, were isolated from corresponding soil samples to clarify their taxonomic status. As a result, a unique collection of Antarctic cyanobacteria isolated from soils was obtained for the first time. The strains were described according to the modern polyphasic taxonomy methods based on an integrated assessment of morphological and molecular-genetic features. Phylogenetic analysis of primary 16S rRNA sequences and peculiarities of secondary structures of internal transcribed spacers enabled us to identify new taxa of potentially endemic cyanobacteria among the strains studied. The high level of similarity between the 16S rRNA gene sequences of soil strains and those previously found in benthic mats of water bodies in the Larsemann Hills confirmed the ability of cyanobacteria to expand beyond different ecological niches and to adapt to contrasting environmental conditions.

Korneykova M.V., Myazin V.A., Fokina N.V., Chaporgina A.A., Nikitin D.A., Dolgikh A.V.

The relevance of the Arctic regions’ study is rapidly increasing due to the sensitive response of fragile ecosystems to climate change and anthropogenic pressure. The microbiome is an important component that determines the soils’ functioning and an indicator of changes occurring in ecosystems. Rybachy Peninsula is the northernmost part of the continental European Russia and is almost completely surrounded by Barents Sea water. For the first time, the microbial communities of the Entic Podzol, Albic Podzol, Rheic Histosol and Folic Histosol as well as anthropogenically disturbed soils (chemical pollution and human impact, growing crops) on the Rybachy Peninsula were characterized using plating and fluorescence microscopy methods, in parallel with the enzymatic activity of soils. The amount and structure of soil microbial biomass, such as the total biomass of fungi and prokaryote, the length and diameter of fungal and actinomycete mycelium, the proportion of spores and mycelium in the fungal biomass, the number of spores and prokaryotic cells, the proportion of small and large fungal spores and their morphology were determined. In the soils of the peninsula, the fungal biomass varied from 0.121 to 0.669 mg/g soil. The biomass of prokaryotes in soils ranged from 9.22 to 55.45 μg/g of soil. Fungi predominated, the proportion of which in the total microbial biomass varied from 78.5 to 97.7%. The number of culturable microfungi ranged from 0.53 to 13.93 × 103 CFU/g in the topsoil horizons, with a maximum in Entic Podzol and Albic Podzol soils and a minimum in anthropogenically disturbed soil. The number of culturable copiotrophic bacteria varied from 41.8 × 103 cells/g in a cryogenic spot to 5551.3 × 103 cells /g in anthropogenically disturbed soils. The number of culturable oligotrophic bacteria ranged from 77.9 to 12,059.6 × 103 cells/g. Changes in natural soils because of anthropogenic impact and a change in vegetation types have led to a change in the structure of the community of soil microorganisms. Investigated tundra soils had high enzymatic activity in native and anthropogenic conditions. The β-glucosidase and urease activity were comparable or even higher than in the soils of more southern natural zone, and the activity of dehydrogenase was 2–5 times lower. Thus, despite the subarctic climatic conditions, local soils have a significant biological activity upon which the productivity of ecosystems largely depends. The soils of the Rybachy Peninsula have a powerful enzyme pool due to the high adaptive potential of soil microorganisms to the extreme conditions of the Arctic, which allows them to perform their functions even under conditions of anthropogenic interference.

Ananyeva N.D., Khatit R.Y., Ivashchenko K.V., Sushko S.V., Gorbacheva A.Y., Dolgikh A.V., Kadulin M.S., Sotnikova Y.L., Vasenev V.I., Komarova A.E., Yudina A.V., Dovletyarova E.A.

Akulava V., Miamin U., Akhremchuk K., Valentovich L., Dolgikh A., Shapaval V.

In this study, for the first time, we report the identification and characterization of culturable fast-growing bacteria isolated from the sea-affected temporary meltwater ponds (MPs) in the East Antarctica area of the Vecherny region (−67.656317, 46.175058) of the Thala Hills Oasis, Enderby Land. Water samples from the studied MPs showed alkaline pH (from 8.0 to 10.1) and highly varied total dissolved solids (86–94,000 mg/L). In total, twenty-nine bacterial isolates were retrieved from the studied MPs. The phylogenetic analysis based on 16S rRNA gene sequence similarities showed that the isolated bacteria belong to the phyla Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes and the twelve genera Pseudomonas, Shewanella, Acinetobacter, Sporosarcina, Facklamia, Carnobacterium, Arthrobacter, Brachybacterium, Micrococcus, Agrococcus, Leifsonia, and Flavobacterium. Most of the isolated bacteria were psychrotrophs and showed the production of one or more extracellular enzymes. Lipolytic and proteolytic activities were more prevalent among the isolates. Five isolates from the Actinobacteria phylum and one isolate from the Bacteroidetes phylum had strong pigmentation. Antibiotic susceptibility testing revealed that most of the isolates are resistant to at least one antibiotic, and seven isolates showed multi-resistance.

Korneykova M.V., Vasenev V.I., Nikitin D.A., Dolgikh A.V., Soshina A.S., Myazin V.A., Nakhaev M.R.

Urban and technogenic landscapes in subarctic zones are not considered comfortable habitats for soil microbiota. However, green infrastructures in polar cities can provide a new niche for the development of a microbial soil community. Soil microbial biomass and the diversity of cultivable microfungi have been studied in relation to the chemical and morphological properties of urban soils in the polar city of Apatity. The quantitative indicators based on fluorescence microscopy and PCR real-time methods as well as the qualitative composition of the cultivable microfungal community were used to characterize the microbial community. Changes in the morphological and chemical composition of urban soils included a shift in pH and increased C and N content compared with forest soil. Studies have shown that the biomass of microfungi and actinomycetes in urban soils was lower than in forest soils and equals 0.12–0.19 mg/g and 0.06–0.44 × 10−3 mg/g, respectively. Bacterial biomass, on the contrary, increased in urban soils up to 2.6 × 10–3 – 5.6 × 10–3 mg/g. The number of ITS gene copies of fungi in urban soils varied from 5.0 × 109 to 1.45 × 1010 copies/g of soil, reaching the highest values in the courtyard. The number of rRNA gene copies of bacteria and archaea in urban soils increased compared with forest soil and amounted to 2.37 × 1010 – 9.99 × 1010 and 0.4 × 1010 – 0.8 × 1010 copies/g of soil, respectively. In urban soils, morphological changes in microfungi, including the predominance of small spores, were revealed in comparison with forest soils, where mycelium prevailed. An increase in the diversity of microfungi in urban soil and changes in the structure of their communities compared with forest soil was noted. Microfungi found in urban soils are not typical of the background soils of the region and would be expected in more southern conditions. Among them, opportunistic fungi species have been identified in humans, which increases the risk of diseases in residents of the northern region.

Korneykova M., Nikitin D., Vasenev V., Dolgikh A.

&lt;p&gt;Soil microbial properties are highly sensitive to anthropogenic disturbance and a considerable impact of urbanization on soil microbial activity and diversity was reported for various cities and climates. The quantitative parameters of the soils&amp;#8217; microbiome in Arctic cities including the structure of microbial biomass and the number of ribosomal genes remain overlooked. This research aimed to compare quantitative indicators, as well as the functional diversity of soil microbial communities in the Arctic cities of Murmansk and Apatity located on the Kola Peninsula.&lt;/p&gt;&lt;p&gt;Murmansk (68.967 N, 33.083 E) is the biggest Arctic city in the world, located in the natural zone of the forest-tundra. Apatity (67.5&amp;#176;N, 33.4&amp;#176;E) is the fifth largest city in polar zone, located in the northern taiga zone.&lt;/p&gt;&lt;p&gt;Samples were collected from the topsoil horizons according to the standard sampling procedure with possible measures to prevent contamination. Quantitative assessment of the content of ribosomal genes of bacteria, archaea, and fungi was performed by real-time polymerase chain reaction (PCR). The prokaryotes and fungal biomass were determined by luminescence microscopy method. Community level physiological profiling (CLPP) was based on MicroResp&lt;sup&gt;&amp;#1058;&amp;#1052;&lt;/sup&gt; approach using substrates representing C sources of different quality: amino acids, carbohydrates, carboxylic and phenolic acid.&lt;/p&gt;&lt;p&gt;The number of archaea was an order of magnitude higher in Murmansk (predominantly 10&lt;sup&gt;10&lt;/sup&gt; of 16s rRNA genes/g soil) than in Apatity (predominantly 10&lt;sup&gt;9 &lt;/sup&gt;of 16s rRNA genes/g soil); the number of 16s rRNA genes copies of bacteria was an order of magnitude lower in Murmansk (10&lt;sup&gt;9&lt;/sup&gt;-10&lt;sup&gt;10&lt;/sup&gt;) compared to Apatity; the number of copies of the ITS rRNA genes of fungi was the same for both locations - 10&lt;sup&gt;9 &lt;/sup&gt;on average.&lt;/p&gt;&lt;p&gt;The biomass of prokaryotes was 5 times higher in Murmansk (5-25 &amp;#956;g/g soil) compared to Apatity (1-6 &amp;#956;g/g soil); the fungal biomass was 3.3 times higher in Murmansk (50-1000 &amp;#956;g/g soil) than in Apatity (40-300 &amp;#956;g/g soil). The length of the mycelium of actinomycetes in the soils of Murmansk (1-100 m/g of soil) was an order of magnitude higher than that in Apatity (0-10 m/g of soil); the length of the fungal mycelium was 3.5 times longer in Murmansk (10-600 m/g of soil) than in Apatity (0-170 m/g of soil).&lt;/p&gt;&lt;p&gt;Soil microbial communities in Arctic cities had a similar physiological profile. Groups of microorganisms consuming carbohydrates and carboxylic acids prevailed. The soils of both cities contained microorganisms capable of decomposing complex organic compounds with a benzene ring, such as phenolic acids (vanillic and lilac), which indicates the potential for the destruction of difficult-to-decompose&amp;#160; substances.&lt;/p&gt;&lt;p&gt;Thus, soil microbial communities in Arctic cities differ to a greater extent in quantitative parameters than in qualitative ones (on example of functional diversity). Probably, the quantitative parameters are more influenced by microclimatic conditions, type of vegetation, level of anthropogenic load, etc.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgements &lt;/strong&gt;This research was supported by&lt;strong&gt; &lt;/strong&gt;RFBR #19-29-05187 and RUDN University Strategic Academic Leadership Program.&lt;/p&gt;

Zazovskaya E.P., Mergelov N.S., Shishkov V.A., Dolgikh A.V., Dobryansky A.S., Lebedeva M.P., Turchinskaya S.M., Goryachkin S.V.

Cryoconite is an organomineral sediment on the surface of glaciers. It has predominantly an eolian origin, demonstrates high microbial activity, and contains a relatively large pool of nutrients. When glaciers retreat, the cryoconite material is translocated to the periglacial zone, where it serves as a nutrient-rich fine-textured parent rock component that promotes establishment of initial soils. Here we examine the spatial patterns of cryoconite on the surface of Aldegonda Glacier (Svalbard) and investigate the further pedogenic transformation of cryoconite material in periglacial environments of this rapidly retreating glacier. The data on micromorphology, composition of carbon and nitrogen stable isotopes, and radiocarbon age of different organic matter fractions in cryoconite and cryoconite-influenced periglacial soils are discussed. We demonstrate that soils formed on cryoconite material partially inherit its properties, and the soil formation processes can be accelerated by an order of magnitude compared to the surrounding nutrient-poor and coarse-textured till.

Зазовская Э.П., Мергелов Н.С., Шишков В.А., Долгих А.В., Добрянский А.С., Лебедева М.П., Турчинская С.М., Горячкин С.В.

Korneykova M., Vasenev V., Ivashchenko K., Saltan N., Slukovskaya M., Kozlova E., Vasilieva M., Sarzhanov D., Gunina A.

Biella P., Bani L., Caprio E., Cochis F., Dondina O., Fiorilli V., Genre A., Gentili R., Orioli V., Ranalli R., Tirozzi P., Labra M.

Suleymanov A., Abakumov E., Polyakov V., Kozlov A., Saby N.P., Kuzmenko P., Telyagissov S., Coblinski J.A.

Passchier C.W., Wassenaar T.M., Groschopf N., Jantschke A., Mertz-Kraus R.

Pazos C., Gualoto M., Oña T., Velarde E., Portilla K., Cabrera-García S., Banchón C., Dávila G., Hernández-Alomia F., Bastidas-Caldes C.

The phenomenon of antimicrobial resistance (AMR) in cold environments, exemplified by the Antarctic, calls into question the assumption that pristine ecosystems lack clinically significant resistance genes. This study examines the molecular basis of AMR in Acinetobacter spp. Isolated from Antarctic soil, focusing on the blaTEM and blaSHV genes associated with extended-spectrum beta-lactamase (ESBL) production; Soil samples were collected and processed to isolate Antarctic soil bacteria. Molecular detection was then conducted using polymerase chain reaction (PCR) to identify the bacteria species by 16S rRNA/rpoB and 10 different beta-lactamase-producing genes. PCR amplicons were sequenced to confirm gene identity and analyze genetic variability. Acinetobacter baumannii were identified by both microbiological and molecular tests. Notably, both the blaTEM and blaSHV genes encoding the enzymes responsible for resistance to penicillins and cephalosporins were identified, indicating the presence of resistance determinants in bacteria from extreme cold ecosystems. The nucleotide sequence analysis indicated the presence of conserved ARGs, which suggest stability and the potential for horizontal gene transfer within microbial communities. These findings emphasize that AMR is not confined to human-impacted environments but can emerge and persist in remote, cold habitats, potentially facilitated by natural reservoirs and global microbial dispersal. Understanding the presence and role of AMR in extreme environments provides insights into its global dissemination and supports the development of strategies to mitigate the spread of resistance genes in both environmental and clinical contexts.

Fiorentino A., Rajput F.Z., Di Serio A., Baldi V., Guarino F., Baldantoni D., Ronga D., Mazzei P., Motta O., Falanga M., Cicatelli A., Castiglione S.

Urban soils are vital components of urban ecosystems, significantly influenced by anthropogenic activities and environmental factors. Despite misconceptions about their quality, urban soils play a pivotal role in carbon (C) cycling and storage, impacting global emissions and sequestration. However, challenges such as soil contamination, land use changes, and urban expansion pose significant threats to soil quality and C storage capacity. Over the last two decades, there has been an increasing interest in the C storage potential of soils as part of climate change mitigation strategies. In this review, a bibliometric analysis covering the last twenty years (2004–2024) was performed to offer insights into global research trends, mainly in urban soils of the Mediterranean region. This paper also identifies research gaps and proposes essential solutions for mitigating the negative impacts of urbanization on soil biodiversity and functions. Key modulators, including plants, microbes, and soil features, are highlighted for their role in C dynamics, emphasizing the importance of effective soil and vegetation management to enhance C sequestration and ecosystem services. Strategies such as reintroducing nature into urban areas and applying organic amendments are promising in improving soil quality and microbial diversity. Further research and awareness are essential to maximize the effectiveness of these strategies, ensuring sustainable urban soil management and climate resilience.

Philpott T.J., Danyagri G., Wallace B., Frank M.

Ávila M., Sánchez C., Calzada J., Briega I., Bailo P., Berruga M., Tomillo J., Rodríguez-Mínguez E., Picon A., Garde S.

Gorbach N.M., Startsev V.V., Yakovleva E.V., Mazur A.S., Dymov A.A.

Petrova A., Michael R.N., Pratt C.

Abstract Street and park trees often endure harsher conditions, including increased temperatures and drier soil and air, than those found in urban or natural forests. These conditions can lead to shorter lifespans and a greater vulnerability to dieback. This literature review aimed to identify confirmed causes of street and park tree dieback in urban areas from around the world. Peer-reviewed case studies related to urban tree decline were scanned for the words “urban”, “city”, “cities”, “tree*”, “decline”, “dieback”, “mortality”, and “survival”. From an initial pool of 1281 papers on Web of Science and 1489 on Scopus, 65 original peer-reviewed research papers were selected for detailed analysis. Out of all species reported to decline, 46 were native, while non-natives were represented by 35 species. The most commonly affected trees were Platanus, Fraxinus, Acer, and Ficus. Most studies were conducted in Mediterranean, humid subtropical, and humid continental climates, with the greatest representation from the United States, followed by Australia, Brazil, Iran, Italy, and Russia. Many authors focused on either biotic or abiotic causes of dieback; some explored both, and some also discussed underlying environmental and urban stresses as potential predisposing factors. The majority (81% of the papers) concluded that a decline was caused by either an arthropod or a microorganism. Overall, it was suggested that changing management strategies to improve water availability and soil health might help with tree resilience. Additionally, regular monitoring and research, along with improving tree species selection and implementing biological and chemical control methods, can help prevent or slow down tree decline. Increasing awareness and adopting preventative approaches could help to extend the lifespan of street and park trees in urban environments and mitigate some of the biological threats, especially considering the challenges we may be facing due to the changing climate.

Sbissi I., Chouikhi F., Ghodhbane-Gtari F., Gtari M.

The stone-dwelling genus Blastococcus plays a key role in ecosystems facing extreme conditions such as drought, salinity, alkalinity, and heavy metal contamination. Despite its ecological significance, little is known about the genomic factors underpinning its adaptability and resilience in such harsh environments. This study investigates the genomic basis of Blastococcus's adaptability within its specific microniches, offering insights into its potential for biotechnological applications. Comprehensive pangenome analysis revealed that Blastococcus possesses a highly dynamic genetic composition, characterized by a small core genome and a large accessory genome, indicating significant genomic plasticity. Ecogenomic assessments highlighted the genus's capabilities in substrate degradation, nutrient transport, and stress tolerance, particularly on stone surfaces and archaeological sites. The strains also exhibited plant growth-promoting traits, enhanced heavy metal resistance, and the ability to degrade environmental pollutants, positioning Blastococcus as a candidate for sustainable agriculture and bioremediation. Interestingly, no correlation was found between the ecological or plant growth-promoting traits (PGPR) of the strains and their isolation source, suggesting that these traits are not linked to their specific environments. This research highlights the ecological and biotechnological potential of Blastococcus species in ecosystem health, soil fertility improvement, and stress mitigation strategies. It calls for further studies on the adaptation mechanisms of the genus, emphasizing the need to validate these findings through wet lab experiments. This study enhances our understanding of microbial ecology in extreme environments and supports the use of Blastococcus in environmental management, particularly in soil remediation and sustainable agricultural practices.

Kamal N., Saharan B.S.

The earth’s surface constitutes a layer of soil around it which is termed as pedosphere. Soil holds millions of microbes that are involved in improving soil fertility. The increasing use of chemical fertilizers has become a major factor which is deteriorating soil microflora. It has resulted in decreased soil fertility. Soil organisms are involved in a number of processes like cycling of soil nutrients and providing them to plants. They are also involved in volatilization that may lead to nutrient loss. Microorganisms have an important role in carbon, nitrogen, and sulfur transformations, as well as organic matter degradation. They have an impact on the global nutrient and carbon cycle. The soil microflora is also involved in modulating the various physico-chemical properties of soil like pH, moisture, temperature etc. Soil properties and soil microorganisms are highly correlated with each other. The huge diversity of microorganisms in soil also plays a central role in regulating and supporting various ecosystem services. This review highlights the crucial role of different microbes in various nutrient cycling which is one of the major concerns to address the decreasing status of soil nutrients. It also covers various physico-chemical properties which affects soil microbial community and various ecosystem services provided by microbial activity.

Prikhodko V., Savelev N., Kotov V., Nikolaev S., Ruslanov E., Rumyantsev M., Manakhova E.

Soil, geochemical, microbiological, and archeological studies were conducted at eight settlements dating from the Paleolithic to Late Medieval and Modern Ages near the southern Trans-Urals Mountains, Russia. The forest-steppe landscapes, rivers, and abundant mineral resources have attracted people to the region since ancient times. Cultural layers (CLs) are marked by finds of ceramics fragments, animal bones, stone, and metal tools. The properties of CLs include close-to-neutral pH, being well structured, the absence of salinity, enrichment with exchangeable calcium, and anthropogenic phosphorus (0.2–0.4%). The majority of CLs start at a depth of 3–25 cm, extend to 40–60 cm, and contain 6–10% organic carbon (Corg) in the 0–20 cm layer, reflecting carbon input from modern-day processes. At the Ishkulovo site (0.6–0.8 ka BP), Corg decreases to 1.3% because the CL is below 80 cm, and in the absence of fresh organic material input, carbon has been mineralized. The proximity of sites to deposits of copper, chromium, zinc, and manganese in the Ural Mountains creates natural high-content anomalies in the region, as indicated by their abundance in soils and parent rocks. In the past, these elements were also released into CLs from metal products, ceramic fragments, and raw materials used in their manufacture. The sites are quite far (18–60 km) from the Magnitogorsk Metallurgical plant, but industrial stockpiles of S (technogenic coefficient—Ct 30–87%), and, less often, Cr, Mn, and Sr (Ct 30–40%) accumulated in surface layers. These three factors have led to the concentration of pollutants of the first (arsenic, chromium, lead, and zinc) and second (cobalt, copper, and nickel) hazard classes at CLs, often in quantities 2–5 times higher than values for parent materials and geosphere average content (“Clarke” value), and, and less often, more than the allowable content for human health. This may have influenced their health and behavioral functions. Due to the above properties, chernozems have a high buffering capacity and a strong bond with heavy metals. Therefore, no inhibition of microbes was observed. The microbial biomass of the 0–10 cm layer is high, 520–680 µg C/g, and microbes cause the emission of 1.0 C-CO2 µg/g of soil per hour. During the ancient settlements’ development, a favorable paleoclimate was noted based on the data cited. This contributed to the spread of productive paleolandscapes, ensuring the development of domestic cattle breeding and agriculture.

Dvornikov Y., Grigorieva V., Vasenev V., Varentsov M., Romzaykina O., Maximova O., Konstantinova A., Matasov V., Kozlova E.

Fowler G., Levy J.

Abstract Continuous permafrost is present across the McMurdo Dry Valleys of southern Victoria Land, Antarctica. While summer active-layer thaw is common in the low-elevation portions of the Dry Valleys, active layers have not significantly thickened over time. However, in some locations, coastal Antarctic permafrost has begun to warm. Here, based on soil and meteorological measurements from 1993 to 2023, we show that wintertime soil temperatures have increased across multiple sites in the Dry Valleys, at rates exceeding the pace of summer soil warming. Linear warming trends over time are significant (P < 0.05) at six of seven soil monitoring sites. Winter warming is strongly correlated with increased numbers of down-valley wind events (Foehn/katabatics), but it may also be driven by increased incident longwave radiation at some stations (although winter longwave increase is not significant over time). While down-valley wind events increase winter warming, when down-valley wind events are excluded from the record, winter soil warming remains persistent and significant, suggesting that Antarctic soils are experiencing less cold winters over time in response to regional warming. Together, these observations suggest that some Antarctic permafrost may be approaching a transition to discontinuous permafrost in some regions as winter freezing intensity is reduced over time.

Guo H., Du E., Terrer C., Jackson R.B.

AbstractUrban greenspaces continue to grow with global urbanization. The global distribution and stock of soil organic carbon (SOC) in urban greenspaces remain largely undescribed and missing in global carbon (C) budgets. Here, we synthesize data of 420 observations from 257 cities in 52 countries to evaluate the global pattern of surface SOC density (0–20 cm depth) in urban greenspaces. Surface SOC density in urban greenspaces increases significantly at higher latitudes and decreases significantly with higher mean annual temperature, stronger temperature and precipitation seasonality, as well as lower urban greenness index. By mapping surface SOC density using a random forest model, we estimate an average SOC density of 55.2 (51.9–58.6) Mg C ha−1 and a SOC stock of 1.46 (1.37–1.54) Pg C in global urban greenspaces. Our findings present a comprehensive assessment of SOC in global urban greenspaces and provide a baseline for future urban soil C assessment under continuing urbanization.

Vasenev V.I., Varentsov M.I., Sarzhanov D.A., Makhinya K.I., Gosse D.D., Petrov D.G., Dolgikh A.V.

Against the background of global warming, urban ecosystems are becoming increasingly vulnerable to climate stresses. Strategies for climate adaptation developed for almost every major city in the world pay considerable attention to urban green infrastructure as a nature-oriented solution for carbon sequestration. However, the influence of urban climate on the spatiotemporal variability of CO2 emissions from urban soils remains poorly understood, which can lead to inaccurate estimates and inflated expectations of urban green infrastructure in the context of carbon neutrality. In 2019–2022, studies of the dynamics of CO2 emission with parallel monitoring of soil temperature and soil moisture were carried out at three green infrastructure sites of Moscow differing in their mesoclimatic conditions. For each object, plots with different types of vegetation were compared, which made it possible to assess the internal heterogeneity of soil and microclimatic conditions. Soil temperature determined up to 70% of the total variance of CO2 emissions. Mean annual soil temperature in the city center was almost 3–6°C higher than that in the peripheral areas (10–12 km from the center), whereas soil moisture in the center was 10–15% lower. Soils under lawns and shrubs were, on average, 1–2°C warmer and 10–15% wetter than soils under trees. The annual CO2 emission from soils under lawns was, on average, 20–30% higher than that from soils under tree plantations in the same area. At the same time, the differences between the plots with the same vegetation in the center and on the periphery reached 50%, which reflects the high vulnerability of urban soil carbon stocks to mesoclimatic anomalies and the high risks of a further increase in CO2 emissions from urban soils against the background of climate change.

Blanco J.A., Durán M., Luquin J., Emeterio L.S., Yeste A., Canals R.M.

Soils store an important amount of carbon (C), mostly in the form of organic matter in different decomposing stages. Hence, understanding the factors that rule the rates at which decomposed organic matter is incorporated into the soil is paramount to better understand how C stocks will vary under changing atmospheric and land use conditions. We studied the interactions between vegetation cover, climate and soil factors using the Tea Bag Index in 16 different ecosystems (eight forests, eight grasslands) along two contrasting gradients in the Spanish province of Navarre (SW Europe). Such arrangement encompassed a range of four climate types, elevations from 80 to 1420 m.a.s.l., and precipitation (P) from 427 to 1881 mm year-1. After incubating tea bags during the spring of 2017, we identified strong interactions between vegetation cover type, soil C/N and precipitation affecting decomposition rates and stabilization factors. In both forests and grasslands, increasing precipitation increased decomposition rates (k) but also the litter stabilization factor (S). In forests, however, increasing the soil C/N ratio raised decomposition rates and the litter stabilization factor, while in grasslands higher C/N ratios caused the opposite effects. In addition, soil pH and N also affected decomposition rates positively, but for these factors no differences between ecosystem types were found. Our results demonstrate that soil C flows are altered by complex site-dependent and site-independent environmental factors, and that increased ecosystem lignification will significantly change C flows, likely increasing decomposition rates in the short term but also increasing the inhibiting factors that stabilize labile litter compounds.

Middelanis T., Pohl C.M., Looschelders D., Hamer U.

AbstractSince its first publication in 2013, the Tea Bag Index (TBI) has attained widespread ecological application, generating scientific data on stabilization and turnover of organic matter in soils. As a result of manufacturing changes (net structure, net material, tea varieties) in the past years, a critical examination of alternative tea bag products is necessary. The present study for the first time generated decomposition data on a wide range of potential alternative tea brands (four brands tested) and varieties (rooibos [RB], green [GT], black [BT], and peppermint tea [PM]). They were tested in both a laboratory and a field experiment lasting 90 days. Under controlled laboratory conditions GT, BT, and PM corresponded well to the kinetic assumptions of an asymptote model of the TBI, but RB did not. In the field experiment, the tea mass remaining after 90 days was determined for all tea bags across different land uses (arable land, grassland, and forest). BT imitated the decomposition behavior of Lipton's original GT even better than any of the GT tested. The finer structure of Lipton's new tea bag nets did not negatively affect the precision of resultant remaining masses and thus can be recommended for future studies. In conclusion, alternative tea bags should be explored across brands as well as varieties. Based on our findings, we proposed an update of the TBI, which is based on the readily feasible modeling of the decomposition curve. Crucial is the combined consideration of both multiple tea varieties and incubation intervals of different durations.

Intergovernmental Panel on Climate Change (IPCC)

The Working Group II contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) provides a comprehensive assessment of the scientific literature relevant to climate change impacts, adaptation and vulnerability. The report recognizes the interactions of climate, ecosystems and biodiversity, and human societies, and integrates across the natural, ecological, social and economic sciences. It emphasizes how efforts in adaptation and in reducing greenhouse gas emissions can come together in a process called climate resilient development, which enables a liveable future for biodiversity and humankind. The IPCC is the leading body for assessing climate change science. IPCC reports are produced in comprehensive, objective and transparent ways, ensuring they reflect the full range of views in the scientific literature. Novel elements include focused topical assessments, and an atlas presenting observed climate change impacts and future risks from global to regional scales. Available as Open Access on Cambridge Core.

Li D., Lu Q., Cai L., Chen L., Wang H.

In this study, we compared the concentrations of the heavy metals Cd, Cr, Cu, Zn, Ni, and Pb in the surface soils of urban parks in Wuhan, Hubei Province, with those in the surface soils of urban parks worldwide. The soil contamination data were assessed using enrichment factors and spatial analysis of heavy metals using inverse distance weighting and quantitative analysis of heavy metal sources with a positive definite matrix factor (PMF) receptor model. Further, a probabilistic health risk assessment of children and adults using Monte Carlo simulation was performed. The average Cd, Cr, Cu, Zn, Ni, and Pb concentrations in the surface soils of urban parks were 2.52, 58.74, 31.39, 186.28, 27.00, and 34.89 mg·kg−1, respectively, which exceeded the average soil background values in Hubei. From the inverse distance spatial interpolation map, heavy metal contamination was primarily observed to be present to the southwest of the main urban area. The PMF model resolved four sources: mixed traffic and industrial emission, natural, agricultural, and traffic sources, with relative contributions of 23.9%, 19.3%, 23.4%, and 33.4%, respectively. The Monte Carlo health risk evaluation model demonstrated negligible noncancer risks for both adult and child populations, whereas the health effects of Cd and Cr on children were a concern for cancer risks.

Namsaraev Z., Bobrik A., Kozlova A., Krylova A., Rudenko A., Mitina A., Saburov A., Patrushev M., Karnachuk O., Toshchakov S.

Cryogenic soils are the most important terrestrial carbon reservoir on the planet. However, the relationship between soil microbial diversity and CO2 emission by cryogenic soils is poorly studied. This is especially important in the context of rising temperatures in the high Arctic which can lead to the activation of microbial processes in soils and an increase in carbon input from cryogenic soils into the atmosphere. Here, using high-throughput sequencing of 16S rRNA gene amplicons, we analyzed microbial community composition and diversity metrics in relation to soil carbon dioxide emission, water-extractable organic carbon and microbial biomass carbon in the soils of the Barents Sea archipelagos, Novaya Zemlya and Franz Josef Land. It was found that the highest diversity and CO2 emission were observed on the Hooker and Heiss Islands of the Franz Josef Land archipelago, while the diversity and CO2 emission levels were lower on Novaya Zemlya. Soil moisture and temperature were the main parameters influencing the composition of soil microbial communities on both archipelagos. The data obtained show that CO2 emission levels and community diversity on the studied islands are influenced mostly by a number of local factors, such as soil moisture, microclimatic conditions, different patterns of vegetation and fecal input from animals such as reindeer.

Bekier J., Jamroz E., Walenczak-Bekier K., Uściła M.

In urban areas, because of anthropopressure, the transformation of the soil cover can lead to the complete destruction of the natural layout and properties of these soils. The object of this study was to determine the quantity and quality of soil organic matter (SOM) originating in the topsoil horizons of the central part of Wroclaw (SW of Poland). Fractional composition of SOM and humic substances (HS) analysis were performed. Elemental composition and CP MAS 13C NMR spectra for the humic acids (HA) were determined, and α (aromaticity) and ω (oxidation) ratios were calculated. Total organic carbon content ranged from 22.39 to 66.1 g kg–1, while that of total nitrogen ranged from 2.09 to 4.6 g kg1. In most analysed urban soils, the highest share in SOM was found for residual carbon (CR), while HA of low maturity was the predominant group over FA. CP MAS 13C NMR spectroscopy of HA molecules indicated the structure of the samples was dominated by compounds with low aromaticity cores and considerable contents of aliphatic components. In urban soils, efforts should be made to enhance organic matter transformation into more matured and stable forms via, e.g., compost application and chemical treatments, and lawn maintenance should be very strictly controlled and limited.

Ananyeva N.D., Khatit R.Y., Ivashchenko K.V., Sushko S.V., Gorbacheva A.Y., Dolgikh A.V., Kadulin M.S., Sotnikova Y.L., Vasenev V.I., Komarova A.E., Yudina A.V., Dovletyarova E.A.

Yakushev A.V., Velichko N.V., Fedorov-Davydov D.G., Mergelov N.S., Lupachev A.V., Rabochaya D.E., Belosokhov A.F., Soina V.S.

The study of microbial complexes in organo-accumulative horizons of Antarctic soils (Cryosols, Leptosols) at the Larsemann Hills and Schirmacher oases and on King George Island has been carried out by the fouling glass method. This method allows one to study the taxonomic composition of microorganisms, features of their morphology, inter-organism interactions, and spatial organization of the complex of microorganisms, as well as to simulate the processes of colonization of mineral surfaces. The investigated microbial complexes can be subdivided into four groups with respect to dominant microorganisms: (1) diverse microbial complexes of King George Island with a considerable portion of diatoms among algae and with a predominance of mycelium in the fungal biomass; (2) complexes of lichen–moss, moss, and algal–moss associations in lake basins with a greater proportion of eukaryotic and coccoid cyanobacteria and with mycelium and sporous forms of micromycetes; (3) complexes of moss and algal–moss associations in the bottoms of wet valleys with a higher proportion of filamentous cyanobacteria and with the absence of fungi, or their presence in the form of short chains of chlamydospores; and (4) hypolithic microbial complexes of rock baths in dry rocky habitats, where the fouling of glasses did not take place. The microbial complexes in different glass samples taken in February–March in different years proved to be at different stages of development. Microscopic mycelium of fungi was not abundant in all algae and moss associations; in some, it was practically absent. Among algae, not cyanobacteria, but eukaryotic algae dominated in a number of habitats: diatoms, green algae, and streptophytes. The totality of the complex features indicated the extremity of the habitat: one morphotype of melanized fungal mycelium dominated in a particular sample; there was no diversity of spore forms, which indirectly indicates a low taxonomic diversity of fungi; multiple chlamydospore formation and microcycles of development were common. Among cyanobacteria, brown and reddish coloration was often found, and the formation of biofilms on glasses was limited to microcolonies, while algal biofilms abundantly covered the soil of the studied horizons. Apparently, extended biofilms were formed over time exceeding the exposure time of the glasses. Hypolithic communities did not colonize new habitats (glasses) for several years of exposure, unlike the bottoms of hydromorphic valleys and lake basins in oases (glasses overgrown in a year) and King George Island (glasses overgrown in 10 days).

Pino V., McBratney A., O'Brien E., Singh K., Pozza L.

A fifty-four per cent of the global population is estimated to live disconnected from the natural environment. Furthermore, a large majority of our community unknown how significant is the soil in their life, e.g. the provider of food, energy and medicine, etc. Strengthening this connection is one relevant action toward Soil Security, referred to as "Soil Connectivity". Citizen Science (CS) improves soil connectivity by increasing citizens awareness and making them collect scientific data. Unfortunately, an indicator of soil connectivity increases is difficult to estimate. Here, we provide a review of fifty-five soil CS initiatives worldwide to collect information such as experts' motivation for starting these projects, technologies being used, and participants' profiles. Our findings show three main trends that citizen soil initiatives tend to follow: those linking soil to human health (e.g. lead, food quality, antibiotics), those focused on future-proofing and education, and those focused on soil health (degradation) and productivity (agriculture). In addition, simplifying scientific technicalities and methods, maintaining communication with participants, and acknowledging contributions are critical factors in crowdsourcing soil research.

Jin M., Sun R., Yang X., Yan M., Chen L.

The morphology of core city growth can be defined as the area, geometry, and change rate of core city within a specific period. A global analysis of core city growth can help predict future development with respect to different natural and social settings. However, current studies largely focus on limited cities or time series of urban expansion, providing limited insight to assess the status of global sustainable development in urban areas. In this study, we examined the morphological evolution of 2276 cities worldwide from 2003 to 2018 using harmonized nighttime satellite data. We found that during the study period the global core city area increased nearly 52 % with Asia leading the growth (4.5 × 10 5 km 2 ) and North America growing the least (0.8 × 10 5 km 2 ). Based on the morphological characteristics, we further identified six city morphological types: decelerated, intensifying, stable, mature, growing, and shrinking. The decelerated type dominated, followed by the intensifying and shrinking types. Cities falling within the other three patterns accounted for about 10 % of the total. Cities with the stable and mature types grew slowly, mainly found in developed regions such as Europe and North America, while cities with the growing type exhibited a high growth rate and were mostly located in developing regions such as Africa and Asia. Moreover, cities with the shrinking pattern were also found in certain developed regions such as Japan, coinciding with the population decline there. Our analysis of global urban morphology 16 years can provide valuable insights into the variations of global core city growth, which are critical for formulating effective policies to achieve urban sustainability. • Global core city area has increased 52 % from 2003 to 2018. • 54 % of all cities were growing slowly with small initial core city area which were designated as the decelerated morphology. • Cities with slow-growing rate were mainly distributed in developed countries. • Only 7 % of all cities developed with a higher population growth than urban sprawl.

McMahen K., Anglin C.D., Lavkulich L.M., Grayston S.J., Simard S.W.

Beneficial soil microbes, such as mycorrhizal fungi and nitrogen-fixing bacteria, can improve plant nutrient acquisition and increase plant resilience to stressors. Yet, the waste materials left behind following major disturbances, such as mining, have negligible biological activity and fresh topsoil availability for reclamation is often limited. We tested if small-volume additions of native forest topsoil can improve early seedling survival and growth, and promote colonization of beneficial root symbionts. In a greenhouse experiment, we grew seedlings representing different functional groups in tailings and glacial-till overburden from the Mount Polley Mine, Canada. We applied 5 % (38 mL) and 25 % (188 mL) forest-soil additions for comparison with tailings/overburden controls and reference forest soil. The experiment was replicated with sterilized soil to isolate the biological effects of the forest soil from the physical and chemical effects. Willow ( Salix scouleriana ) and spruce ( Picea engelmannii x glauca ) seedling survival and growth increased with proportion of forest soil, which corresponded with increased ectomycorrhizal fungal colonization. Forest soil additions benefited seedlings grown in both overburden and tailings, with ~200 mL (25 %) forest soil additions generally supporting initial seedling growth comparable to seedlings grown in reference forest soil. Alder ( Alnus viridis ) showed minimal benefit from forest soil additions, likely due to a lack of nitrogen-fixing bacteria in the forest soil, highlighting the importance of matching the plant and microbial communities of the soil donor site with the target plant species. Differential results among plant species in sterilized soil indicated that plants exhibiting greater dependence on microbial symbionts (spruce and alder), benefited from the biological component of the inoculum, while willow, an early successional species with low mycorrhizal dependence, benefited from the physical and chemical properties of the forest soil. This research showed that targeted additions of small volumes of topsoil from native ecosystems can improve initial seedling survival and growth, and promote recovery of limiting soil microbial communities, making it a promising approach for mine reclamation when topsoil availability is limited. • Small-volume forest soil additions improve seedling growth in mine reclamation. • Forest soil inoculates beneficial microbes e.g., EM fungi and N-fixing bacteria. • The living component of soil benefits plants dependent on microbial mutualists. • Non-living forest soil benefits early successional, non-microbial dependent plants. • Consider compatibility of the donor soil microbial community with planted species.

Kim D., Chae N., Kim M., Nam S., Kim T.K., Park K., Lee B.Y., Kim E., Lee H.

Recent rapid air temperature increases across the northern-latitude tundra have prolonged permafrost thawing and snow melting periods, resulting in increased soil temperature (Ts) and volumetric soil water content (SWC). Under prolonged soil warming at 8°C, Alaskan tundra soils were incubated in a microcosm system and examined for the SWC differential influence on the microbial decomposition activity of large molecular weight (MW) humic substances (HS). When one microcosm soil (AKC1-1) was incubated at a constant SWC of 41% for 90 days (T = 90) and then SWC was gradually decreased from 41% to 29% for another T = 90, the initial HS was partly depolymerized. In contrast, in AKC1-2 incubated at a gradually decreasing SWC from the initial 32% to 10% for T = 90 and then increasing to 27% for another T = 90, HS depolymerization was undetected. Overall, the microbial communities in AKC1-1 could maintain metabolic activity at sufficient and constant SWC during the initial T = 90 incubation. In contrast, AKC1-2 microbes may have been damaged by drought stress during the drying SWC regimen, possibly resulting in the loss of HS decomposition activity, which did not recover even after re-wetting to an optimal SWC range (20–40%). After T = 90, the CO2 production in both treatments was attributed to the increased decomposition of small-MW organic compounds (including aerobic HS-degradative products) within an optimal SWC range. We expect this study to provide new insights into the early effects of warming- and topography-induced SWC variations on the microbial contribution to CO2 emissions via HS decomposition in northern-latitude tundra soil.

Yan Y., Wang C., Zhang J., Sun Y., Xu X., Zhu N., Cai Y., Xu D., Wang X., Xin X., Chen J.

The carbon and nutrients in the soil microbial biomass (SMB) and their proportion in soil elements, namely soil microbial quotient (SMQ), are the key indicators of the soil quality and quickly respond to the shift in the land-use pattern. However, the degree of the land-use shift influences on the soil microbial biomass, and the soil microbial quotient in the meadow steppe is not well-understood. The soil microbial biomass carbon (MBC), nitrogen (MBN), phosphorous (MBP), and SMQ were determined separately in grassland, cropland, and abandoned cropland in four sites within 50 km at a meadow steppe in northeast China. The results showed that the soil MBC, MBN, and MBP declined significantly as soil depth increased among the three land-use patterns. Agriculture has resulted in a significant decrease in the soil MBC, MBN, MBP, and SMQ compared to their corresponding values in grassland. The soil MBC content significantly was increased at the 0–10 cm soil layer after agriculture abandonment, but the SMQ had no significant improvement in the entire profile when compared to cropland. Besides, for the three types of land-use patterns, the C, N, and P stoichiometry of the soil microbial biomass was relatively stable, except for the stoichiometry in the relatively deep soil layer. Overall, the present agricultural abandonment (~ 19 years) got a certain of restoration in soil microbial biomass. Their corresponding values, however, were significantly lower than those found in native grassland. This highlighted that the restoration of the poor soil quality caused by the long term agriculture cultivation is a slow and hard process; it is important to maintain natural grasslands for protecting and maintaining soil microbial biomass and SMQ in the meadow steppe of northeast China. • Agriculture significantly decreased both soil microbial biomass and soil microbial quotient. • Grassland-cropland conversion caused the greater reduction in the nutrients of soil microbial biomass than those of soils. • Agriculture abandonment significantly improved surface soil MBC but had no significant effect on soil microbial quotient. • The stoichiometry of C, N and P in soil microbial biomass kept relatively stable during grassland-cropland conversion.