Permafrost regime affects the nutritional status and productivity of larches in Central Siberia

Вечная мерзлота оказывает сильное влияние на развитие лесов благодаря доступности питательных веществ. Основные вопросы этого исследования касались влияния условий площадки на концентрацию макроэлементов в массе и стабильную изотопную (13C и 15N) динамику в течение вегетационного периода, а также стехиометрию питательных веществ и эффективность резорбции в листве двух общих видов лиственницы в Сибири. Концентрация личинок, выращенных на многолетнемерзлых почвах лиственных пород (N, P и K), была чрезвычайно высокой в юных иглах по сравнению с концентрациями в зоне без вечной мерзлоты, но была в 2 раза ниже с созреванием игл. В пределах вечной мерзлоты деревья с участков с более теплым и более глубоким почвенным активным слоем имели концентрацию питательных веществ на 15-60% и более высокую 15N в их иглах по сравнению с более слабыми, более холодными почвами. Лиственница без вечной мерзлоты демонстрировала обогащение листвой в 15N (от +1,4 до +2,4 ‰) по сравнению с вечной мерзлотой (от -2,0 до -6,9 ‰). Сезонная динамика листьев d13C, как правило, снижалась с июня по август на всех участках, положительно коррелируя с массовыми концентрациями N (r = 0,69, p <0,05) и отрицательно с отношением C: N (r = -0,79, p <0,05) , При старении концентрация питательных веществ в иглах лиственницы значительно уменьшилась на 60-90%. Эта сильная способность лиственницы сохранять питательные вещества посредством резорбции является важным механизмом, который поддерживает рост деревьев в начале вегетационного периода, когда почва остается замороженной. Высокая резорбтивная эффективность, обнаруженная для K и P для лиственниц, установленных на вечной мерзлоте, указывает на ограничение питательных веществ роста деревьев в Центрально-Сибирском плато не только по N, как сообщалось ранее, но и по P и K. Наряду с увеличением биомассы (до 50 раз ), более высокие концентрации питательных веществ и обогащение листьев 15N в более теплых местах указывают на сильную реакцию производительности лиственницы на углубление активного слоя почвы

ФОРМИРОВАНИЕ «НОВОЙ БИФУРКАЦИИ» У БОЛЬНЫХ С ПРОЛОНГИРОВАННЫМ АТЕРОСКЛЕРОТИЧЕСКИМ ПОРАЖЕНИЕМ ВСА

This article provides indications for and description of surgical technique of carotid endarterectomy with the formation of a new bifurcation. It also presents the results of observations in the immediate postoperative period based on the findings of this surgery among patients of Vishnevsky National Medical Research Center of Surgery.В данной статье приведены показания для проведения и подробная техника выполнения КЭАЭ с формированием новой бифуркации. Также приведены результаты наблюдений в ближайшем послеоперационном периоде по результатам этой операции среди пациентов института хирургии им. А. В. Вишневского

Hydroclimatic Controls on the Isotopic (δ18 O, δ2 H, d-excess) Traits of Pan-Arctic Summer Rainfall Events

Arctic sea-ice loss is emblematic of an amplified Arctic water cycle and has critical feedback implications for global climate. Stable isotopes (delta O-18, delta H-2, d-excess) are valuable tracers for constraining water cycle and climate processes through space and time. Yet, the paucity of well-resolved Arctic isotope data preclude an empirically derived understanding of the hydrologic changes occurring today, in the deep (geologic) past, and in the future. To address this knowledge gap, the Pan-Arctic Precipitation Isotope Network (PAPIN) was established in 2018 to coordinate precipitation sampling at 19 stations across key tundra, subarctic, maritime, and continental climate zones. Here, we present a first assessment of rainfall samples collected in summer 2018 (n = 281) and combine new isotope and meteorological data with sea ice observations, reanalysis data, and model simulations. Data collectively establish a summer Arctic Meteoric Water Line where delta H-2 = 7.6.delta O-18-1.8 (r(2) = 0.96, p 0.75 parts per thousand/degrees C) were observed at continental sites, while statistically significant temperature relations were generally absent at coastal stations. Model outputs indicate that 68% of the summer precipitating air masses were transported into the Arctic from mid-latitudes and were characterized by relatively high delta O-18 values. Yet 32% of precipitation events, characterized by lower delta O-18 and high d-excess values, derived from northerly air masses transported from the Arctic Ocean and/or its marginal seas, highlighting key emergent oceanic moisture sources as sea ice cover declines. Resolving these processes across broader spatial-temporal scales is an ongoing research priority, and will be key to quantifying the past, present, and future feedbacks of an amplified Arctic water cycle on the global climate system

Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire : an expert assessment

As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.Peer reviewe

Permafrost Regime Affects the Nutritional Status and Productivity of Larches in Central Siberia

Permafrost exerts strong controls on forest development through nutrient availability. The key question of this study was to assess the effect of site conditions on macroelement concentration and stable isotope (&delta;13C and &delta;15N) dynamics during the growing season, and nutrient stoichiometry and resorption efficiency in the foliage of two common larch species in Siberia. Foliar nutrient (N, P and K) concentrations of larches grown on permafrost soils were exceptionally high in juvenile needles compared to those from a permafrost-free region (+50% and 130% for P and K), but were two-fold lower at needle maturation. Within permafrost terrain trees, sites with a warmer and deeper soil active layer had 15&ndash;60% greater nutrient concentrations and higher &delta;15N in their needles compared to shallower, colder soils. Larch of permafrost-free sites demonstrated an enrichment of foliage in 15N (+1.4% to +2.4&permil;) in comparison to permafrost terrain (&minus;2.0% to &minus;6.9&permil;). At all sites, foliar &delta;13C decreased from June to August, which very likely results from an increasing contribution of current photoassimilates to build foliar biomass. With senescence, nutrient concentrations in larch needles decreased significantly by 60&ndash;90%. This strong ability of larch to retain nutrients through resorption is the essential mechanism that maintains tree growth early in the growing season when soil remains frozen. The high resorptive efficiency found for K and P for larches established on permafrost suggests nutrient limitation of tree growth within the Central Siberian Plateau not only by N, as previously reported, but also by P and K. The increasing nutrient concentrations and a 15N enrichment of foliage towards warmer sites was paralleled by an up to 50-fold increase in biomass production, strongly suggesting that accelerated nutrient cycling with permafrost degradation contributes to an increased productivity of Siberian larch forests

Dissolved Carbon Concentrations and Emission Fluxes in Rivers and Lakes of Central Asia (Sayan–Altai Mountain Region, Tyva)

The carbon (C) cycle in inland waters, including carbon concentrations in and carbon dioxide (CO2) emissions from water surfaces, are at the forefront of biogeochemical studies, especially in regions strongly impacted by ongoing climate change. Towards a better understanding of C storage, transport and emission in Central Asian mountain regions, an area of knowledge that has been extremely poorly studied until now, here, we carried out systematic measurements of dissolved C and CO2 emissions in rivers and lakes located along a macrotransect of various natural landscapes in the Sayan–Altai mountain region, from the high mountains of the Western Sayan in the northwest of Tyva to the arid (dry) steppes and semideserts in the intermountain basins in the southeast of Tyva on the border with Mongolia. New data on major hydrochemical parameters and CO2 fluxes (fCO2) gathered by floating chambers and dissolved organic and inorganic carbon (DOC and DIC, respectively) concentrations collected over the four main hydrological seasons allowed us to assess the current C biogeochemical status of these water bodies in order to judge possible future changes under climate warming. We further tested the impact of permafrost, river watershed size, lake area and climate parameters as well as ‘internal’ biogeochemical drivers (pH, mineralization, organic matter quality and bacterial population) on CO2 concentration and emissions in lakes and rivers of this region and compared them with available data from other subarctic and mountain settings. We found strong environmental control of the CO2 pattern in the studied water bodies, with thermokarst lakes being drastically different from other lakes. In freshwater lakes, pCO2 negatively correlated with O2, whereas the water temperature exerted a positive impact on pCO2 in large rivers. Overall, the large complexity of counteracting external and internal drivers of CO2 exchange between the water surfaces and the atmosphere (CO2-rich underground DIC influx and lateral soil and subsurface water; CO2 production in the water column due to dissolved and particulate OC biodegradation; CO2 uptake by aquatic biota) precluded establishing simple causalities between a single environmental parameter and the fCO2 of rivers and lakes. The season-averaged CO2 emission flux from the rivers of Tyva measured in this study was comparable, with some uncertainty, to the C uptake fluxes from terrestrial ecosystems of the region, which were assessed in other works

Novel potential causative genes in carotid paragangliomas

Abstract Background Carotid paragangliomas (CPGLs) are rare neuroendocrine tumors that arise from the paraganglion at the bifurcation of the carotid artery and are responsible for approximately 65% of all head and neck paragangliomas. CPGLs can occur sporadically or along with different hereditary tumor syndromes. Approximately 30 genes are known to be associated with CPGLs. However, the genetic basis behind the development of these tumors is not fully elucidated, and the molecular mechanisms underlying CPGL pathogenesis remain unclear. Methods Whole exome and transcriptome high-throughput sequencing of CPGLs was performed on an Illumina platform. Exome libraries were prepared using a Nextera Rapid Capture Exome Kit (Illumina) and were sequenced under 75 bp paired-end model. For cDNA library preparation, a TruSeq Stranded Total RNA Library Prep Kit with Ribo-Zero Gold (Illumina) was used; transcriptome sequencing was carried out with 100 bp paired-end read length. Obtained data were analyzed using xseq which estimates the influence of mutations on gene expression profiles allowing to identify potential causative genes. Results We identified a total of 16 candidate genes (MYH15, CSP1, MYH3, PTGES3L, CSGALNACT2, NMD3, IFI44, GMCL1, LSP1, PPFIBP2, RBL2, MAGED1, CNIH3, STRA6, SLC6A13, and ATM) whose variants potentially influence their expression (cis-effect). The strongest cis-effect of loss-of-function variants was found in MYH15, CSP1, and MYH3, and several likely pathogenic variants in these genes associated with CPGLs were predicted. Conclusions Using the xseq probabilistic model, three novel potential causative genes, namely MYH15, CSP1, and MYH3, were identified in carotid paragangliomas

Mutational load in carotid body tumor

Abstract Background Carotid body tumor (CBT) is a rare neoplasm arising from paraganglion located near the bifurcation of the carotid artery. There is great intra-tumor heterogeneity, and CBT development could be associated with both germline and somatic allelic variants. Studies on the molecular genetics of CBT are limited, and the molecular mechanisms of its pathogenesis are not fully understood. This work is focused on the estimation of mutational load (ML) in CBT. Methods Using the NextSeq 500 platform, we performed exome sequencing of tumors with matched lymph node tissues and peripheral blood obtained from six patients with CBT. To obtain reliable results in tumors with low ML, we developed and successfully applied a complex approach for the analysis of sequencing data. ML was evaluated as the number of somatic variants per megabase (Mb) of the target regions covered by the Illumina TruSeq Exome Library Prep Kit. Results The ML in CBT varied in the range of 0.09–0.28/Mb. Additionally, we identified several pathogenic/likely pathogenic somatic and germline allelic variants across six patients studied (including TP53 variants). Conclusions Using the developed approach, we estimated the ML in CBT, which is much lower than in common malignant tumors. Identified variants in known paraganglioma/pheochromocytoma-causative genes and novel genes could be associated with the pathogenesis of CBT. The obtained results expand our knowledge of the mutation process in CBT as well as the biology of tumor development