A natural micro- (ciliates, diatoms, flagellates) and meiobenthic (nematodes, harpacticoids) assemblage from the White Sea intertidal was used to study the effect of irradiance on the sustainability and species composition. Four treatments were maintained for two months: unshaded (control), lightly shaded (90 % light flux), semi-shaded (50 %), and completely shaded (darkness). Different groups of organisms displayed a variety of responses to the light conditions. Abundance and diversity of diatoms were not significantly affected by the light regime, except for the largest size class (>1000 mu m(3)), which decreased in abundance fourfold. At the same time, redox potential and nitrate content decreased in the dark treated sediments, and the ratio of reduced (NH4+) to oxidized (NO3- + NO2-) forms of nitrogen increased consistently, as the phaeopigments to chlorophyll a ratio. These results are consistent with the survival of small-to-medium-sized diatoms under dark and hypoxic conditions owing to switch their metabolic pathway from photosynthesis to dissimilatory nitrate reduction to ammonium (DNRA). Evidence was provided in support of less ability of large diatoms to stock nitrates intracellularly and employ DNRA. Other groups, both autotrophs (phytoflagellates) and heterotrophs (flagellates, ciliates, nematodes and harpacticoids) decreased in abundance under fully shaded conditions, whereas diversity and assemblage structure were less affected by shading. These changes, however, did not exceed the range of natural spatiotemporal variability observed at the site, indicating a pronounced resistance of the polar benthic community to two-month light limitation.

Studying vegetation dynamics in the regions with high volcanic activity is crucial for understanding ecosystem responses to environmental disturbances and predicting future ecological changes. However, the impacts of tephra deposition on vegetation at local and regional scales remain poorly quantified, limiting understanding of ecosystem resilience to volcanic disturbances. This study presents a high-resolution, multiproxy palaeobotanical record from the Kumroch peatland (Kamchatka, Eurasian Far East), integrating detailed tephrostratigraphy, radiocarbon ages, pollen, plant macrofossil, and loss on ignition data. The peat sequence spans the last similar to 5 kyr, anchored by 28 recorded tephra layers. Birch forests (Betula ermanii) and alder shrublands (Alnus alnobetula subsp. fruticosa) dominated during the Middle and Late Holocene, with their proportions shifting in response to climate variations. These changes align in timing with the Late Holocene climate oscillations, primarily reflecting temperature fluctuations. Tephra fallout events had no persistent impact on regional vegetation and limited effects on the local vegetation. These findings demonstrate the resilience of boreal ecosystems to tephra deposition across volcanically active areas and underscore the importance of large-scale studies for understanding ashfall-related disturbances.

Trait-based approaches are increasingly used in ecology to better understand species' functional roles and adaptations. Testate amoebae, a diverse group of microbial eukaryotes driving important ecological functions, are particularly suited for trait-based analysis due to their considerable morphological variability. However, traditional classifications of testate amoebae rely primarily on morphology, potentially overlooking ecologically relevant information. This study developed a novel system of functional groups for testate amoebae based on 18 functional traits and assessed its ecological significance. We used hierarchical clustering on a trait database encompassing 372 species from the Northern Holarctic realm. Our analysis identified seven distinct functional groups, which reflect adaptive strategies linked to shell size, aperture traits, and feeding modes: large-bodied predators (Groups 1 and 2), medium-sized bacterivores (Groups 3-5), patelliform generalists (Group 6), and small, highly adaptable taxa (Group 7). A case study in the Eastern European Plain revealed that organic soils harbored greater functional diversity, with species spanning all groups, while mineral soils were dominated by Group 5 (hemispheric, drought-tolerant bacterivores). Functional space ordination highlighted habitat-driven divergence, with organic soil communities characterized by traits optimizing resource exploitation (e.g., straight terminal apertures, idiosome shells) and mineral soils favoring desiccation-resistant morphologies (central ventral apertures, compact shells). The new functional classification provides a more comprehensive understanding of the testate amoebae's ecological functions and improves our ability to predict their responses to environmental change.

Understanding the long-term dynamics of hydrological changes in mire ecosystems is critical for predicting their responses to climate changes and managing carbon-rich peat deposits. This study reconstructs the late-Holocene hydrological dynamics of a mire at the southern boundary of the mixed forests of the East European Plain, with a focus on non-Sphagnum (consisting of wood and grass remains) peats. We apply a multiproxy approach, utilising plant macrofossil analysis, testate amoeba assemblages, and peat humification measurements as proxies of past moisture conditions. The data reveal that the main changes in vegetation cover over the last 3000 years correspond well to climatic variation. However, the agreement among the hydrological reconstructions based on three proxies was good only at the initial stage of peat accumulation and greatly reduced with the predominance of trees in vegetation cover. Moreover, our findings show that Sphagnum-dominated peats of an adjacent mire were characterised by a better agreement among hydrological proxies. Overall, despite the agreement among various proxies can vary depending on the type of peat deposits, an application of a multi-proxy approach can reveal complimentary aspects of the hydrological regime variation in mires.

Permafrost mires are very sensitive to climate variations and can potentially release considerable amounts of carbon to the atmosphere due to permafrost degradation. On the other hand, permafrost degradation may promote mires development, leading to atmospheric carbon sequestration in the form of peat. In order to understand the dynamics of mire development in a continuous permafrost region, we used a multi-proxy paleoecological reconstruction based on 120-year-old peat deposit from Central Siberia. At the initial stages, a waterlogged forest at the border of a permafrost mire was subjected to burning that resulted in further waterlogging leading to a quick transition from waterlogged forest to a poor fen over ca. 15 years. Further accelerated mire development and corresponding rapid peat accumulation coincided with climate warming and were associated with a post-fire succession on the surrounding area. This resulted in a formation of a dry forested oligotrophic mire. Overall, our findings demonstrate a substantial potential for permafrost mires to develop in the marginal zone after forest disturbance with the subsequent establishment of a new equilibrium between forests and mires in accordance with the climatic conditions.

The genus Leptomyxa unifies two morphologically distinct groups of species: reticulate and non-reticulate. Previously, it was believed that only large reticulate species were capable of adopting a fan-shaped form. In recent years, fan-shaped cells have been discovered in four small non-reticulate species. In this study, we describe Leptomyxa echinata n. sp., isolated from a bottom sediment sample from Sobachiy Pond, Izmailovsky Park, Moscow, Russia. Amoebae of this species are non-reticulate, flattened, and branched, and can adopt a monopodial form. Interestingly, the morphology of monopodial cells differs on the surface of glass slides and in culture dishes. Leptomyxa echinata n. sp. is capable of adopting a remarkable fan-shaped form with numerous pointed outgrowths along the anterior margin. In addition, the karyoplasm of these amoebae, besides rounded nucleoli, contains tiny rounded granules. These features have not previously been described for other species of the genus Leptomyxa. The 18S rRNA gene sequence differentiates L. echinata n. sp. from all other species of this genus.

The permafrost peatlands of Central Siberia are crucial carbon sinks that are vulnerable to climate warming. However, their Holocene dynamics remain poorly understood. This study presents a high-resolution, multiproxy reconstruction of hydroclimatic changes, peatland development and the history of vegetation from the Gornoye palsa peatland in the Inner Central Siberian Plateau. By analyzing plant macrofossils, pollen, testate amoebae, stable isotopes (delta(13), delta N-15) and radiocarbon dating, we have traced peatland evolution over the Holocene. Our results revealed a non-linear development characterized by complex feedbacks between regional climate and local conditions. Paludification of a wet larch forest began similar to 8700 cal yr BP, evolving into a rich fen during the Holocene Thermal Maximum (7800-5300 cal yr BP). The first permafrost aggradation occurred similar to 5500-5000 cal yr BP. The Mid-Late Holocene time interval (5380-600 cal yr BP) was marked by cyclical oscillations between permafrost uplift (peat plateau stages) and degradation (fen conditions), driven by climate fluctuations. A major phase of sustained palsa growth commenced after 2250 cal yr BP, reflecting Neoglacial cooling. An abrupt shift to a waterlogged thaw hollow similar to 600 cal yr BP signifies a major collapse of the perennial frost mound. We conclude that the peatland's evolution is highly sensitive to hydroclimatic changes, with its carbon and nitrogen cycles directly impacted by freeze-thaw dynamics. The current mosaic of stable and degrading peat plateaus suggests that the system is responding to modern warming. This study provides a benchmark for understanding the long-term vulnerability of Siberian peatland carbon stocks to climate change.

The Western Siberian peatlands rank among the largest in the Northern Hemisphere. This study investigates peatland development and palaeohydrological changes of the Mukhrino mire during the Holocene focussing on climatic, regional and local factors. The multiproxy and multi-core approach reveals spatial variability driven by topography and sedimentary conditions. Our study integrates testate amoebae, plant macrofossils, peat geochemical and biomarkers to provide insights into past vegetation and environmental conditions. Peat accumulation in Mukhrino mire began in the early Holocene, with regional vegetation influenced by climatic and soil factors. Forest cover has been present since the Early Holocene. Birch and pine dominated in the drained areas and episodic regional presence of Tilia and Ulmus indicated warmer intervals. Since ~8800 cal yr BP, Mukhrino mire transitioned to an oligotrophic/ombrotrophic state dominated by Sphagnum fuscum . A key focus of this study is the dynamics of peatland surface wetness over millennia. Proxy-specific responses revealed both short-term variability (via testate amoebae) and long-term climatic trends (via plant macrofossils). Local dry phases (~6500–5700/4700 and 2200–1800 cal yr BP) resulted in partial mire afforestation, while wetter periods (~5700/4700–2500 cal yr BP) facilitated the restoration of its current state. Comparisons with prior studies identified two wet and four dry zones, with synchronised wetness trends across cores despite localised variations in peat accumulation rates. A pronounced local wet phase (~6700–6800 cal yr BP) corresponds with a marker layer from nearby Lake Svetlenkoye sediments (~8000–6700 cal yr BP), attributed to Ob River palaeo-floods. This evidence supports the presence of regionally wet environmental conditions during this period.

Soil microbial communities play a crucial role in the functioning of terrestrial ecosystems. Rapid changes in climate and land-use will likely cause major changes in belowground biodiversity with unknown consequences on ecosystem functioning. The functional traits, taxonomic and functional diversities of soil microorganisms are known to vary in relation to soil type and climate, but few studies have compared these patterns and explored assembly community mechanisms systematically in contrasted ecological conditions. Here we address this gap and focus on testate amoebae, a key group of shell-producing microbial predators known to play significant roles in C and N cycling in terrestrial ecosystem. We used morphological approach to assess and compare their taxonomic and functional diversity in organic (Histosols) and mineral soils in six regions (320 samples) spanning a wide range of latitudes (52-67 degrees N, 2126 km) and longitudes (46-107 degrees E, 3927 km) in Central-North Eurasia. Our study revealed significant differences in testate amoeba community composition, diversity, functional traits and assembly mechanisms among ecoregions and soil type. In the ecoregions with drier soils, testate amoeba taxonomic and functional diversities were higher in organic soils compared to mineral soils, while the opposite was observed in ecoregions with wetter soils. With respect to morphological traits, in drier-soil ecoregions such as forest-steppes, testate amoebae were longer and had a relatively smaller aperture in organic soils, while the opposite is true in wetter-soil ecoregions such as taiga and tundra. Habitat filtering was identified as the leading assembly process in mineral soils, while biotic factors were more influential in organic soils. This study provides a comprehensive comparative analysis of testate amoeba communities, enhancing our understanding of how abiotic and biotic factors shape microbial communities in ecosystems, highlighting the role of soil moisture regime, and offering valuable insights for predicting ecological responses to environmental changes.

Carbon storage capacity of peat deposits in permafrost mires is highly sensitive to climate change which effects might be strongly mediated by mire moisture and permafrost. Thus, it is essential to develop appropriate indicator tools of hydrological regime which can be used for monitoring present and past conditions in these mires. We use testate amoebae to investigate their indicator value to water table depth (WTD) and substrate water content (SWC) and to develop transfer functions for quantitative reconstructions of these environmental characteristics in the permafrost mires on the Central Siberian Plateau. In many cased, direct measurement of WTD in permafrost mires are not possible due to the presence of ice, so that SWC can be used as an alternative characteristic. Overall, 330 surface samples were collected in five study regions together with the corresponding environmental measurements. We find that testate amoebae form diverse assemblages with the species structure strongly controlled by WTD and SWC. We developed two testate amoeba-based transfer functions to reconstruct these characteristics based on Modern Analogue Technique which were assessed using leave-one-out and bootstrap cross-validation. We find that both transfer functions have good predictive power (for WTD: RMSEP = 6.8-7.6 cm, R2 = 0.54, for SWC: RMSEP = 2.0-2.3 %, R2 = 0.74-0.76). The ecological preferences of the majority of testate amoebae were similar to those reported by the studies in lower-latitudes, although some hydrophilic taxa were observed in the drier end of the surface wetness gradient. These data represent an important source for improvement of quantitative reconstructions based on subfossil testate amoebae in permafrost mires.

The genus Leptomyxa (Amoebozoa, Tubulinea, Leptomyxida) includes both nonreticular and reticular amoebae. Some of them are able to alter the shape of the cell from monopodial to flattened. To date, this genus includes 13 valid species. However, most of the species have been described from Europe and Russia, while data on other geographic regions are almost absent. In this paper, we describe the first species of this genus, Leptomyxa xiamenii n. sp., isolated from China, namely from a pond on the campus of the Institute of Urban Environment in Xiamen. The morphology of the current isolate is similar to other non-reticular species of the genus Leptomyxa. Meanwhile, it is characterized by the variability of nucleolar material and has a remarkable floating form with thin pseudopodia. In old cultures of this species, some cells are covered with a loose envelope consisting of bacteria embedded in a slime, which has never been observed for other Leptomyxa species. The 18S rRNA gene sequence reliably differs L. xiamenii n. sp. from all other species of this genus.

Across the northern East-European Plain, and especially in the Mologa-Sheksna Lowland (MSL), short-term climate variability in the Late Glacial caused significant palaeohydrological alterations, which drove vegetation successions. The MSL is prominent for the dense river and lake network, which have evolved through multiple water level and sedimentation regime oscillations since the Last Glacial Maximum. Extensive bogs inherit morphology of the basins, which had been filled with paleolakes for several millennia until their ultimate drainage in the early Holocene. Correspondingly, intricate morphology of lakes and deltas conditioned mosaic distribution of vegetation across the MSL. Continuous palaeoenvironmental record for the Holocene in the MSL has been derived from several peat and lacustrine sites. The data regarding the Late Glacial is much more scarce, due to the low abundance of the relevant deposits, and poor state of preservation. Except for the MSL bog plains, pronounced evidence for the short-term palaeoenvironmental offset was discovered in the section of the sand terraces in the Mologa River catchment. The onset of Allerød warming has been traced via an organomineral layer, which was confirmed to have a continuous bedding over the area of 100 km2 in the central MSL, as revealed by auger drilling and ground-penetrating radar survey at eight sites. This layer dates back to 13.4– 12.1 cal ka BP, and is represented by interbedding of fine sand with medium decomposed peat. Palynological and plant macrofossil studies of the buried peat from three boreholes reveal several inferences about the formation of this layer and the general palaeohydrology of the MSL in the Late Glacial. The first palaeoclimatic evidence is provided by the high abundance of spruce pollen and bark pieces, supporting the hypothesis that the layer formation occurred during the Allerød interstadial, which was characterized by a rapid expansion of spruce in the region. Secondly, high abundances of pollen and remains of hydrophytes or hydrophilous lacustrine vascular plants (Cyperaceae, Poaceae, Potamogetonaceae), mosses (Sphagnum sp., Drepanocladus aduncus and Calliergonella cuspidatum) and chara algae indicate lentic shallow water environment or the proximity of the paleolake shoreline. In general, a transition from shallow lacustrine environments, surrounded by spruce-birch forests, to tundra steppes and bogged grasslands can be deduced, based on the pollen spectra and subfossils assemblages. Third, true altitude of the buried peat layer (96.5 – 102.5 m above sea level) may be considered as a limit for the paleolake water level in the Allerød, because it delineates the surface uncovered from water or proximate to the shoreline. Thus, its lowermost discovered position can trace the extent to which the paleolake level had dropped in the Allerød. The peat was rapidly formed and buried during the late Allerød, which makes it a reliable regional isochronous stratigraphic level for the poorly studied Late Glacial sedimentary successions. This level can be used as a reference point for tracing recent short-term climate-environment interactions and effects.

Urban areas contribute the vast majority of greenhouse gas (GHG) emissions, and urban greenspaces, including urban parks, are being established to promote environmental health by mitigating GHG emissions. However, the diversity of CH4 and N2O cycling genes and microbiomes in urban park ecosystems remains poorly understood. Here, we sampled five types of habitats in subtropical urban parks, including moss, sediment, soil, tree hole, and water, to explore the microbial communities and microbially mediated CH4 and N2O cycling processes using metagenomic sequencing. We found strongly positive biodiversity-ecosystem-functioning (BEF) relationships in nitrogen cycling functions, as well as in CH4 cycling, except in sediment, indicating the microbial community in the sediment had reached function saturation for CH4 cycling. CH4 cycling was driven by a few specific microbial genera, whereas many microorganisms participated in the denitrification process. Microbes in sediment exhibited the highest CH4 and N2O metabolic potential among the five habitats, especially for methanogenesis and N2O production processes. Significant positive correlations were observed between the mcrA and N2O cycling genes, suggesting methanogenesis could be coupled with denitrification. Environmental factors, such as dissolved oxygen, total nitrogen, and total carbon greatly affected microbial community composition and functional gene families. These results highlight that pond sediments are an overlooked potential source of CH4 and N2O emissions, which may undermine the role of urban greenspace in reducing GHG emissions. Reducing nitrogen pollution and eutrophication is recommended to mitigate CH4 and N2O emissions from pond sediments in urban environments.

Lake terrestrialisation greatly transforms functioning of freshwater ecosystems leading to considerable changes in primary production, sedimentation rates and community composition. In order to understand the main factors controlling this process, the long-term data accounting for various aspects of lake functioning are required. Here we present a multi-proxy palaeoecological study of shoreline terrestrialisation of Lake Glubokoe located in the forest zone of East European Plain (Moscow region) during the late Holocene. We have used radiocarbon dating, loss on ignition, X-ray fluorescence, humification degree, plant macrofossil, pollen, Cladocera, chironomid and testate amoeba analyses. We found that the water level in the lake was higher than present until 1840 cal yr BP, that resulted in minerogenic sediment accumulation at the site. After that, the lake underwent the following stages of shoreline terrestrialisation including a gradual water-level decrease and eutrophication with the accumulation of organic-rich deposits (1840–1120 cal yr BP), intensive development of riparian vegetation (1120–990 cal yr BP), a short-term dry interval which was probably associated with Medieval Warm Period (MWP, 990–850 cal yr BP) and the formation of an eutrophic wetland at the shoreline (850 cal yr BP—the present). The eutrophication was associated with a climate-driven increase in biological productivity of the lake and possibly by a greater human activity in the area. Our data suggest that terrestrialisation of Lake Glubokoe was a complex process driven by climate, ecological succession and human activities. These findings support the results of the previous studies on the long-term dynamics of lake ecosystems showing the importance of climate effects on the water level in the lakes with small upstream catchment and provide a context for an interpretation of the existing century-long instrumental observations.

ABSTRACTAimThe role of environmental factors that shape the large‐scale distribution of eukaryotic microbes remains understudied. We aimed to disentangle the impacts of latitudinal and longitudinal gradients on the distribution of Sphagnum‐dwelling testate amoebae in mires and to understand the influence of environmental factors related to both local habitats (hummock—lawn—hollows) and regional climates.LocationA range from temperate to subarctic and from the European part to the Far East of Russia (51°–70°N, 32°–158°E).TaxonTestate amoeba (Arcellinida, Euglyphida, and Amphitremida).MethodsWe analysed the testate amoeba (TA) composition and abundance data from 816 samples collected in 75 peatlands. Linear mixed‐effects models and redundancy analysis were applied to determine the likely environmental drivers of TA α‐ and β‐diversity.ResultsWe identified a significant reversed latitudinal gradient in α‐diversity which negatively correlated with the mean annual temperature. This gradient is microhabitat‐specific, being prominent in lawn and hollow microhabitats, but not in hummocks. Longitude, which corresponds mainly to a gradient of precipitation seasonality, was a significant predictor of TA β‐diversity, especially in hollows.Main ConclusionsOur findings identify climatic factors (e.g., mean annual temperature and precipitation seasonality) as likely shaping the continental‐scale TA α‐ and β‐diversity patterns, emphasising the microhabitat‐specific nature of these relationships. The absence of pattern in hummocks is interpreted as evidence for a predominant microhabitat stress (i.e., low moisture and pH) in this habitat.

Co-occurrence analyses were originally employed to explore community assembly mechanisms driven by species interaction, especially competition. Here, we applied co-occurrence analysis based on community null models to explore metacommunity assembly mechanisms of soil testate amoeba communities in two contrasted environmental settings in the Ural Mountains: 1) within a single type of microbiotope (Picea obovata sub-crown soil litter microbiotope) and 2) in the most typical microbiotopes from each vegetation type across the landscape. The former revealed random co-occurrence pattern that we interpret as evidence for the mass effect mechanism. The latter revealed segregated non-random co-occurrence pattern that we interpret as evidence for the species sorting mechanism. We tested several null models which differ in their underlying assumptions regarding ecological features of sites and species, and our findings underscore the crucial role of a reasonable choice of a null model for subsequent ecological inferences. In terms of site treatment, we recommend assessing species richness variability among sites to substantiate the choice of a specific null model. At the species features side, we base our choice of a specific null model on the species occurrence evidence.

Microbiomes are integral to ecological health and human well-being; however, their ecological and evolutionary drivers have not been systematically investigated, especially in urban park ecosystems. As microbes have different levels of tolerance to environmental changes and habitat preferences, they can be categorized into habitat generalists and specialists. Here, we explored the ecological and evolutionary characteristics of both prokaryotic and microeukaryotic habitat generalists and specialists from six urban parks across five habitat types, including moss, soil, tree hole, water, and sediment. Our results revealed that different ecological and evolutionary processes maintained and regulated microbial diversity in urban park ecosystems. Under ecological perspective, community assembly of microbial communities was mainly driven by stochastic processes; however, deterministic processes were higher for habitat specialists than generalists. Microbial interactions were highly dynamic among habitats, and habitat specialists played key roles as module hubs in intradomain networks. In aquatic interdomain networks, microeukaryotic habitat specialists and prokaryotic habitat specialists played crucial roles as module hubs and connectors, respectively. Furthermore, analyzing evolutionary characteristics, our results revealed that habitat specialists had a much higher diversification potential than generalists, while generalists showed shorter phylogenetic branch lengths as well as larger genomes than specialists. This study broadens our understanding of the ecological and evolutionary features of microbial habitat generalists and specialists in urban park ecosystems across multi-habitat. IMPORTANCE:Urban parks, as an important urban greenspace, play essential roles in ecosystem services and are important hotspots for microbes. Microbial diversity is driven by different ecological and evolutionary processes, while little is currently known about the distinct roles of ecological and evolutionary features in shaping microbial diversity in urban park ecosystems. We explored the ecological and evolutionary characteristics of prokaryotic and microeukaryotic habitat generalists and specialists in urban park ecosystems based on a representative set of different habitats. We found that different ecological and evolutionary drivers jointly maintained and regulated microbial diversity in urban park microbiomes through analyzing the community assembly process, ecological roles in hierarchical interaction, and species diversification potential. These findings significantly advance our understanding regarding the mechanisms governing microbial diversity in urban park ecosystems.

The functional traits of soil protists have been employed in ecological research to enhance comprehension of the underlying mechanisms of ecological processes. Among the numerous soil protists, testate amoebae emerge as a prominent and abundant group, playing a pivotal role in soil micro-food webs. Furthermore, they are regarded as valuable bioindicators for environmental monitoring and palaeoecological studies due to their sensitivity to environmental changes. We screened 372 testate amoebae species widely distributed across Northern Holarctic realm and collected trait data, representing the morphological and feeding characteristics of testate amoebae. The dataset would provide valuable basis for investigation of the functional diversity and ecological roles of testate amoebae, thus facilitating further research on soil protist communities and ecosystem dynamics.

The Mologa-Sheksna Lowland peatlands represent incredibly valuable archives of information for reconstruction of the Holocene regional palaeoenvironmental dynamics. A profound application of multiproxy techniques (AMS dating, XRF scanning, testate amoebae and loss on ignition analyses), coupled with a palaeogeographical review, enabled us to perform a robust reconstruction of peat deposition and main palaeoenvironmental milestones during the Holocene. Peat accumulation started ~11.0 cal. ka BP over the upland watershed areas, preceded by mineral lacustrine sedimentation. In smaller enclosed basins, peat accumulation took place from ~8.7 cal. ka BP. Oscillations in accumulation rates and decomposition degree of peat along the cores provide evidence for dry Middle Holocene (8.6–4.4 cal. ka BP) and a 2-ka time lag in oligotrophic peat deposition onset between the two different geomorphological localities.

In the Caucasus, the total area taken up by glaciers is known to have reduced by 23% over the last 20 years. This natural experiment allows for additive and replacement models of autogenic succession of biocoenoses within paraglacial landscapes to be tested. A certain risk of the extinction of cryophilic species also exists. However, montane paraglacial successions of invertebrate assemblages have hitherto been studied neither in the Caucasus nor in Russia as a whole. Structural changes of taxocoenoses were traced in a spatial and temporal sequence of ten properly dated paraglacial sites in the Tsey Gorge, North Ossetia − Alania (1–170-years old) among the testate amoebae, earthworms, molluscs, myriapods, mites, spiders, harvestmen, pseudoscorpions, collembolans, and beetles. As the glacier retreats, in place of bare paraglacial wastelands, grassland communities are formed that, after 10–14 years, are replaced by shrub vegetation and, on 30–35-year old surfaces, by forest communities. Most of the invertebrate groups, once “appearing” along a postglacial transect, were recorded from most older plots as well. Yet, their taxocoenoses underwent considerable transformations through increasing (or an increase turning into some decline in beetles) the species diversity and a strong, often complete change in the taxonomic composition and dominance structure. The most considerable transformations were observed at all major vegetation changes. The “appearance” of some groups in the transect was determined not only by dispersion capacities but mainly by the environmental conditions of particular habitats. When comparing the composition of the pioneer postglacial species complex of the study region with that in the mountains of Europe’s south and north, its high-degree regional specificity was noted, sometimes shown at the family level (in spiders). Spatial β-diversity of all larger taxa studied was mainly attributed to turnover (due to “the replacement model” of succession). The general level of change diminished towards the later succession stages. Endemic arthropod species were revealed both in pioneer grassland and developed forest communities.