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Author(s): Igor Volkov [1]; Jayanth R. Banavar (corresponding author) [1]; Amos Maritan [2]; Stephen P. Hubbell [3] The unified neutral theory of biodiversity and biogeography [1] provides a dynamic null [...]

In contrast to the well-studied West Siberian sector of frozen bogs in the Russian Arctic, the frozen mound bogs (so-called "palsas") on the highlands of Southern Siberia have not yet been studied, but they are suspected to be even more sensitive to ongoing climate change. This article provides the pilot study on palsa mire Kara-Sug in the highland areas of Western Sayan mountain system, Tuva Republic. The study focuses on the current state of palsa mire and surrounding landscapes, providing wide range of ecological characteristics while describing ongoing transformations of natural landscapes under a changing climate. The study used a variety of field and laboratory methods: the integrated landscape-ecological approach, the study of peat deposits, geobotanical analysis, and modern analysis of the chemical composition of water, peat, and soils. The study shows that highland palsa mires are distinguished by their compactness and high variety of cryogenic landforms leading to high floristic and ecosystem diversity compared with lowland palsa mires. This information brings new insights and contributes to a better understanding of extrazonal highland palsa mires, which remain a "white spot" in the global environmental sciences. [ABSTRACT FROM AUTHOR]

We present a new photoelectric light curve of a Coronae Borealis. The derived rate of apsidal motion differs from the theoretical prediction. A possible solution of the problem is suggested. [ABSTRACT FROM AUTHOR]

UBVRI photoelectric and CCD photometry of the slow nova V723 Cas obtained in the years 1995-2003 is presented. The evolution of light curves in 1-year intervals, folded with the orbital period 0.69326 days, shows an increase of the amplitude of the wave-like variations from 0.07 to 1.3 mag during the years 1997-2003. The fact that the shape and amplitude of the orbital light curves does not depend on wavelength is most probably related to the geometry of eclipses combined with the distribution of circumstellar matter in the system. [ABSTRACT FROM AUTHOR]

Changes in climate, land-use and pollution are having disproportionate impacts on ecosystems and biodiversity of arctic and mountain ecosystems. While these impacts are well-documented for many areas of the Arctic and alpine regions, some isolated and inaccessible mountain areas are poorly studied. Furthermore, even in well-studied regions, assessments of biodiversity and species responses to environmental change are biased towards vascular plants and cryptogams, particularly bryophytes are far less represented. This paper aims to document the environments of the remote and inaccessible Altai-Sayan mountain mires and particularly their bryofloras where threatened species exist and species new to the regional flora are still being found. As these mountain mires are relatively inaccessible, changes in drivers of change and their ecosystem and biodiversity impacts have not been monitored. However, the remoteness of the mires has so far protected them and their species. In this study, we describe the mires, their bryophyte species and the expected impacts of environmental stressors to bring attention to the urgency of documenting change and conserving these pristine ecosystems. [ABSTRACT FROM AUTHOR]

We present optical spectroscopic and photometric observations of type II SNe 2019vxm and 2020tlf. The photometric monitoring of SN 2019vxm continued for 592 days, two spectra were collected. SN 2020tlf was observed for 163 days and we obtained one spectra. The maximum luminosity of both SNe is high: MV=−20.0,−18.33$$ {M}_V=-20.0,-18.33 $$ mag for SN 2019vxm and SN 2020tlf, respectively. SN 2019vxm displays typical for most of SNe IIn photometric evolution: long rise to the maximum and slow brightness decline with several changes of the decline rate. The light curve of SN 2020tlf shows it may be considered as an intermediate object between classes II‐P and II‐L. The spectral evolution of SN 2019vxm was typical for SNe IIn, while for SN 2020tlf only weak signs of circumstellar interaction were observed at maximum light. [ABSTRACT FROM AUTHOR]

The toxic metal mercury (Hg) has been mined, processed, and used throughout the Fergana Valley region of post-Soviet Central Asia for millennia. Although most historical Hg mining activities have ceased throughout the Fergana Valley region, Hg is still mined, processed, and exported globally from the Khaidarkan kombinat in southwestern Kyrgyzstan. Despite the rich history of Hg mining and use throughout the Fergana Valley region, the legacy effects of these activities on environmental Hg contamination remain undescribed. Mercury concentrations were analyzed in topsoil, terrestrial vegetation, earthworms, riverine sediments, and fish collected from sites with varied histories of Hg mining within the Fergana Valley region. Environmental and biological Hg concentrations were greatest at contemporary mining sites where Hg has been mined after 1940, intermediate at ancient mining sites where all historical Hg mining activities ceased before 1300 AD, and lowest at reference sites without known Hg mining history. For all environmental media and biota, Hg concentrations were 1–2 orders of magnitude greater at contemporary mining sites than at reference sites. Elevated Hg concentrations at contemporary mining sites are attributed to the recency and intensity of Hg mining and showcase the detrimental effects of Hg mining on diverse environmental media and biota. Elevated Hg concentrations at ancient mining sites are attributed to a combination of (1) legacy Hg contamination in soils and sediments introduced by historical mining and processing activities over 700 years ago and (2) the presence of naturally Hg-rich geologic belts upon which ancient mines were constructed. [ABSTRACT FROM AUTHOR]

Our March–May photometry of the optical counterpart of the black hole candidate XTE J1118+480 during the plateau of outburst confirmed the existence ofthe known 0.17085 d variations in the R-band with amplitude 0m.06 and the 10-s QPOs, which are stronger in the I-band. [ABSTRACT FROM AUTHOR]

The rapid increase in serendipitous X-ray source detections requires the development of novel approaches to efficiently explore the nature of X-ray sources. If even a fraction of these sources could be reliably classified, it would enable population studies for various astrophysical source types on a much larger scale than currently possible. Classification of large numbers of sources from multiple classes characterized by multiple properties (features) must be done automatically and supervised machine learning (ML) seems to provide the only feasible approach. We perform classification of Chandra Source Catalog version 2.0 (CSCv2) sources to explore the potential of the ML approach and identify various biases, limitations, and bottlenecks that present themselves in these kinds of studies. We establish the framework and present a flexible and expandable Python pipeline, which can be used and improved by others. We also release the training data set of 2941 X-ray sources with confidently established classes. In addition to providing probabilistic classifications of 66,369 CSCv2 sources (21% of the entire CSCv2 catalog), we perform several narrower-focused case studies (high-mass X-ray binary candidates and X-ray sources within the extent of the H.E.S.S. TeV sources) to demonstrate some possible applications of our ML approach. We also discuss future possible modifications of the presented pipeline, which are expected to lead to substantial improvements in classification confidences. [ABSTRACT FROM AUTHOR]

Peatlands cover 3% of the land, occur in 169 countries, and have—by sequestering 600 Gt of carbon—cooled the global climate by 0.6 °C. After a general review about peatlands worldwide, this paper describes the importance of the Great Vasyugan Mire and presents suggestions about its protection and future research. The World's largest peatland, the Great Vasyugan Mire in West-Siberia, forms the border between the Taiga and the Forest-Steppe biomes and harbours rare species and mire types and globally unique self-organizing patterns. Current oil and gas exploitation may arguably be largely phased out by 2050, which will pave the way for a stronger focus on the mire's role in buffering climate change, maintaining ecosystem diversity, and providing other ecosystem services. Relevant new research lines will benefit from the extensive data sets that earlier studies have gathered for other purposes. Its globally unique character as the 'largest life form on land' qualifies the Great Vasyugan Mire in its entirety to be designated as a UNESCO World Heritage Site and a Ramsar Wetland of International Importance. [ABSTRACT FROM AUTHOR]

Pyritization in late Pleistocene sediments of the Black Sea is driven by sulfide formed during anaerobic methane oxidation. A sulfidization front is formed by the opposing gradients of sulfide and dissolved iron. The sulfidization processes are controlled by the diffusion flux of sulfide from above and by the solid reactive iron content. Two processes of diffusion-limited pyrite formation were identified. The first process includes pyrite precipitation with the accumulation of iron sulfide precursors with the average chemical composition of FeSn (n = 1.10–1.29), including greigite. Elemental sulfur and polysulfides, formed from H2S by a reductive dissolution of Fe(III)-containing minerals, serve as intermediates to convert iron sulfides into pyrite. In the second process, a “direct” pyrite precipitation occurs through prolonged exposure of iron-containing minerals to dissolved sulfide. Methane-driven sulfate reduction at depth causes a progressive formation of pyrite with a δ34S of up to +15.0‰. The S-isotopic composition of FeS2 evolves due to contributions of different sulfur pools formed at different times. Steady-state model calculations for the advancement of the sulfidization front showed that the process started at the Pleistocene/Holocene transition between 6360 and 11 600 yr BP. Our study highlights the importance of anaerobic methane oxidation in generating and maintaining S-enriched layers in marine sediments and has paleoenvironmental implications. [Copyright &y& Elsevier]

The main terminal processes of organic matter mineralization in anoxic Black Sea sediments underlying the sulfidic water column are sulfate reduction in the upper 2–4 m and methanogenesis below the sulfate zone. The modern marine deposits comprise a ca. 1-m-deep layer of coccolith ooze and underlying sapropel, below which sea water ions penetrate deep down into the limnic Pleistocene deposits from >9000 years BP. Sulfate reduction rates have a subsurface maximum at the SO42−-CH4 transition where H2S reaches maximum concentration. Because of an excess of reactive iron in the deep limnic deposits, most of the methane-derived H2S is drawn downward to a sulfidization front where it reacts with Fe(III) and with Fe2+ diffusing up from below. The H2S-Fe2+ transition is marked by a black band of amorphous iron sulfide above which distinct horizons of greigite and pyrite formation occur. The pore water gradients respond dynamically to environmental changes in the Black Sea with relatively short time constants of ca. 500 yr for SO42− and 10 yr for H2S, whereas the FeS in the black band has taken ca. 3000 yr to accumulate. The dual diffusion interfaces of SO42−-CH4 and H2S-Fe2+ cause the trapping of isotopically heavy iron sulfide with δ34S = +15 to +33‰ at the sulfidization front. A diffusion model for sulfur isotopes shows that the SO42− diffusing downward into the SO42−-CH4 transition has an isotopic composition of +19‰, close to the +23‰ of H2S diffusing upward. These isotopic compositions are, however, very different from the porewater SO42− (+43‰) and H2S (−15‰) at the same depth. The model explains how methane-driven sulfate reduction combined with a deep H2S sink leads to isotopically heavy pyrite in a sediment open to diffusion. These results have general implications for the marine sulfur cycle and for the interpretation of sulfur isotopic data in modern sediments and in sedimentary rocks throughout earth’s history. [Copyright &y& Elsevier]

We demonstrate that when power scaling occurs for an individual tree and in a forest, there is great resulting simplicity notwithstanding the underlying complexity characterizing the system over many size scales. Our scaling framework unifies seemingly distinct trends in a forest and provides a simple yet promising approach to quantitatively understand a bewilderingly complex many-body system with imperfectly known interactions. We show that the effective dimension, D tree , of a tree is close to 3, whereas a mature forest has D forest approaching 1. We discuss the energy equivalence rule and show that the metabolic rate-mass relationship is a power law with an exponent D /( D + 1) in both cases leading to a Kleiber's exponent of 3/4 for a tree and 1/2 for a forest. Our work has implications for understanding carbon sequestration and for climate science., (© The Author(s) 2022. Published by Oxford University Press on behalf of the National Academy of Sciences.)

Biological diversity is the basis for, and an indicator of biosphere integrity. Together with climate change, its loss is one of the two most important planetary boundaries. A halt in biodiversity loss is one of the UN Sustainable Development Goals. Current changes in biodiversity in the vast landmass of Siberia are at an initial stage of inventory, even though the Siberian environment is experiencing rapid climate change, weather extremes and transformation of land use and management. Biodiversity changes affect traditional land use by Indigenous People and multiple ecosystem services with implications for local and national economies. Here we review and analyse a large number of scientific publications, which are little known outside Russia, and we provide insights into Siberian biodiversity issues for the wider international research community. Case studies are presented on biodiversity changes for insect pests, fish, amphibians and reptiles, birds, mammals and steppe vegetation, and we discuss their causes and consequences., (© 2021. Royal Swedish Academy of Sciences.)

We present climate-dependent changes in the high-mountain forest ecotone, old-growth forests, alpine phytocenoses, and deglaciated forelands in the Aktru glacial basin (Altai Republic, Russia). A number of independent sources (variations in upper treeline altitude, dendrochronological data, analysis of lacustrine sediments and botanical and geographical studies linked with the dynamics of glacial-dammed lakes in the Chuya and Kurai intermountain depressions) suggest Holocene temperatures reached about 4 °C higher than today. Unlike the European Alps, glaciers in the continental Altai Mountains disappeared before forming again. Also, the upper altitudinal limit of mountain forests during the Holocene was greater than in the European Alps. The high variability of mountain ecosystems in southern Siberia suggests their potential instability in a currently changing climate. However, periglacial successions associated with the strong continental climate and glacier retreat represent an area of increasing biodiversity and plant cover. The historical and current sensitivity of the continental mountains to climate variations which exceeds that of the European Alps requires greater understanding, environmental protection, and increased social responsibility for the consequences of anthropogenic contributions to climate change: the isolated Altai areas contribute little to climate changes, but are greatly affected by them., (© 2021. Royal Swedish Academy of Sciences.)

We present 2 distinct and independent approaches to deduce the effective interaction strengths between species and apply it to the 20 most abundant species in the long-term 50-ha plot on Barro Colorado Island, Panama. The first approach employs the principle of maximum entropy, and the second uses a stochastic birth-death model. Both approaches yield very similar answers and show that the collective effects of the pairwise interspecific interaction strengths are weak compared with the intraspecific interactions. Our approaches can be applied to other ecological communities in steady state to evaluate the extent to which interactions need to be incorporated into theoretical explanations for their structure and dynamics.