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The magnitude of terrestrial carbon (C)-climate feedback largely depends on the temperature sensitivity of soil organic matter (SOM) decomposition (Q10). However, our understanding of determinants of Q10 for SOM fractions such as particulate and mineral-associated organic matter (POM and MAOM, respectively) is still inadequate. Particularly, it remains unclear whether microbial effects on Q10 are fraction-dependent, which induces large uncertainties in projecting soil C dynamics. Here, we conducted large-scale topsoil sampling on the Tibetan Plateau, in combination with SOM fractionation and 300-day laboratory incubation to assess SOM fraction-dependent linkages between Q10 and microbial properties. We found that compared with MAOM, POM had larger Q10 and greater microbial diversity, and also structured distinct microbial communities as well as their co-occurrence patterns. Furthermore, associations of Q10 with microbial properties differed between the two SOM fractions. Bacterial community composition and relative abundance of bacterial keystone taxa affected Q10 for POM and MAOM respectively, while bacterial alpha diversity showed opposite relationships with Q10 for POM and MAOM. These findings highlight the necessity of incorporating SOM fraction-dependent microbial properties and their linkages with Q10 into Earth system models to accurately predict terrestrial C-climate feedback.
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Microbiota , Microbiología del Suelo , Suelo , Temperatura , Suelo/química , Tibet , Bacterias/clasificación , Bacterias/metabolismo , Bacterias/aislamiento & purificación , Carbono/análisis , Carbono/metabolismoRESUMEN
Significant attention has been given to the way in which the soil nitrogen (N) cycle responds to permafrost thaw in recent years, yet little is known about anaerobic N transformations in thermokarst lakes, which account for more than one-third of thermokarst landforms across permafrost regions. Based on the N isotope dilution and tracing technique, combined with qPCR and high-throughput sequencing, we presented large-scale measurements of anaerobic N transformations of sediments across 30 thermokarst lakes over the Tibetan alpine permafrost region. Our results showed that gross N mineralization, ammonium immobilization, and dissimilatory nitrate reduction rates in thermokarst lakes were higher in the eastern part of our study area than in the west. Denitrification dominated in the dissimilatory nitrate reduction processes, being two and one orders of magnitude higher than anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA), respectively. The abundances of the dissimilatory nitrate reduction genes (nirK, nirS, hzsB, and nrfA) exhibited patterns consistent with sediment N transformation rates, while α diversity did not. The inter-lake variability in gross N mineralization and ammonium immobilization was dominantly driven by microbial biomass, while the variability in anammox and DNRA was driven by substrate supply and organic carbon content, respectively. Denitrification was jointly affected by nirS abundance and organic carbon content. Overall, the patterns and drivers of anaerobic N transformation rates detected in this study provide a new perspective on potential N release, retention, and removal upon the formation and development of thermokarst lakes.
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Compuestos de Amonio , Nitratos , Nitratos/análisis , Lagos , Nitrógeno , Anaerobiosis , Desnitrificación , Compuestos Orgánicos , CarbonoRESUMEN
Mineralization of dissolved organic matter (DOM) in thermokarst lakes plays a non-negligible role in the permafrost carbon (C) cycle, but remains poorly understood due to its complex interactions with external C and nutrient inputs (i.e., aquatic priming and nutrient effects). Based on large-scale lake sampling and laboratory incubations, in combination with 13 C-stable-isotope labeling, optical spectroscopy, and high-throughput sequencing, we examined large-scale patterns and dominant drivers of priming and nutrient effects of DOM biodegradation across 30 thermokarst lakes along a 1100-km transect on the Tibetan Plateau. We observed that labile C and phosphorus (P) rather than nitrogen (N) inputs stimulated DOM biodegradation, with the priming and P effects being 172% and 451% over unamended control, respectively. We also detected significant interactive effects of labile C and nutrient supply on DOM biodegradation, with the combined labile C and nutrient additions inducing stronger microbial mineralization than C or nutrient treatment alone, illustrating that microbial activity in alpine thermokarst lakes is co-limited by both C and nutrients. We further found that the aquatic priming was mainly driven by DOM quality, with the priming intensity increasing with DOM recalcitrance, reflecting the limitation of external C as energy sources for microbial activity. Greater priming intensity was also associated with higher community-level ribosomal RNA gene operon (rrn) copy number and bacterial diversity as well as increased background soluble reactive P concentration. In contrast, the P effect decreased with DOM recalcitrance as well as with background soluble reactive P and ammonium concentrations, revealing the declining importance of P availability in mediating DOM biodegradation with enhanced C limitation but reduced nutrient limitation. Overall, the stimulation of external C and P inputs on DOM biodegradation in thermokarst lakes would amplify C-climate feedback in this alpine permafrost region.
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Understanding biogeographical patterns and underlying processes of belowground community assembly is crucial for predicting soil functions and their responses to global environmental change. However, little is known about potential differences of belowground community assembly among bacteria, fungi, protists and soil animals, particularly for alpine ecosystems. Based on the combination of large-scale field sampling, high-throughput marker-gene sequencing and multiple statistical analyses, we explored patterns and drivers of belowground community assembly in alpine grasslands on the Tibetan Plateau. Our results revealed that the distance-decay rates varied among trophic levels, with organisms of higher trophic level having weaker distance-decay pattern. The spatial and environmental variables explained limited variations of belowground communities. By contrast, the stochastic processes, mainly consisting of dispersal limitation and drift, played a primary role in regulating belowground community assembly. Moreover, the relative importance of stochastic processes varied among trophic levels, with the role of dispersal limitation weakening whereas that of drift enhancing in the order of bacteria, fungi, protists and soil animals. These findings advance our understanding of patterns and mechanisms driving belowground community assembly in alpine ecosystems and provide a reference basis for predicting the dynamics of ecosystem functions under changing environment.
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Ecosistema , Pradera , Animales , Suelo , Microbiología del Suelo , Procesos Estocásticos , TibetRESUMEN
Warming-induced permafrost thaw may stimulate soil respiration (Rs) and thus cause a positive feedback to climate warming. However, due to the limited in situ observations, it remains unclear about how Rs and its autotrophic (Ra) and heterotrophic (Rh) components change upon permafrost thaw. Here we monitored variations in Rs and its components along a permafrost thaw sequence on the Tibetan Plateau, and explored the potential linkage of Rs components (i.e., Ra and Rh) with biotic (e.g., plant functional traits and soil microbial diversity) and abiotic factors (e.g., substrate quality). We found that Ra and Rh exhibited divergent responses to permafrost collapse: Ra increased with the time of thawing, while Rh exhibited a hump-shaped pattern along the thaw sequence. We also observed different drivers of thaw-induced changes in the ratios of Ra:Rs and Rh:Rs. Except for soil water status, plant community structure, diversity, and root properties explained the variation in Ra:Rs ratio, soil substrate quality and microbial diversity were key factors associated with the dynamics of Rh:Rs ratio. Overall, these findings demonstrate divergent patterns and drivers of Rs components as permafrost thaw prolongs, which call for considerations in Earth system models for better forecasting permafrost carbon-climate feedback.
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Hielos Perennes , Procesos Autotróficos , Ciclo del Carbono , Respiración , Suelo/químicaRESUMEN
Permafrost thaw could trigger the release of greenhouse gases through microbial decomposition of the large quantities of carbon (C) stored within frozen soils. However, accurate evaluation of soil C emissions from thawing permafrost is still a big challenge, partly due to our inadequate understanding about the response of microbial communities and their linkage with soil C release upon permafrost thaw. Based on a large-scale permafrost sampling across 24 sites on the Tibetan Plateau, we employed meta-genomic technologies (GeoChip and Illumina MiSeq sequencing) to explore the impacts of permafrost thaw (permafrost samples were incubated for 11 days at 5°C) on microbial taxonomic and functional communities, and then conducted a laboratory incubation to investigate the linkage of microbial taxonomic and functional diversity with soil C release after permafrost thaw. We found that bacterial and fungal α diversity decreased, but functional gene diversity and the normalized relative abundance of C degradation genes increased after permafrost thaw, reflecting the rapid microbial response to permafrost thaw. Moreover, both the microbial taxonomic and functional community structures differed between the thawed permafrost and formerly frozen soils. Furthermore, soil C release rate over five month incubation was associated with microbial functional diversity and C degradation gene abundances. By contrast, neither microbial taxonomic diversity nor community structure exhibited any significant effects on soil C release over the incubation period. These findings demonstrate that permafrost thaw could accelerate C emissions by altering the function potentials of microbial communities rather than taxonomic diversity, highlighting the crucial role of microbial functional genes in mediating the responses of permafrost C cycle to climate warming.
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Hielos Perennes , Carbono , Ciclo del Carbono , Suelo , Microbiología del SueloRESUMEN
Permafrost thaw could increase methane (CH4) emissions, which largely depends on CH4 production driven by methanogenic archaea. However, large-scale evidence regarding key methanogenic taxa and their relative importance to abiotic factors in mediating methanogenesis remains limited. Here, we explored the methanogenic community, potential CH4 production and its determinants in the active layer and permafrost deposits based on soil samples acquired from 12 swamp meadow sites along a â¼1000 km permafrost transect on the Tibetan Plateau. Our results revealed lower CH4 production potential, mcrA gene abundance, and richness in the permafrost layer than those in the active layer. CH4 production potential in both soil layers was regulated by microbial and abiotic factors. Of the microbial properties, marker OTUs, rather than the abundance and diversity of methanogens, stimulated CH4 production potential. Marker OTUs differed between the two soil layers with hydrogenotrophic Methanocellales and facultative acetoclastic Methanosarcina predominant in regulating CH4 production potential in the permafrost and active layer, respectively. Besides microbial drivers, CH4 production potential increased with the carbon/nitrogen (C/N) ratio in both soil layers and was also stimulated by soil moisture in the permafrost layer. These results provide empirical evidence for model improvements to better predict permafrost carbon feedback to climate warming.
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The study aimed to identify the independent prognostic factors of mixed endometrial carcinoma (MEC) patients treated with hysterectomy and to explore the optimal treatment modalities for overall survival (OS) and cancer-specific survival (CSS). Using the Surveillance, Epidemiology, and End Results (SEER) database, a total of 12,848 MEC patients treated with hysterectomy were screened out. Independent prognostic factors were identified by Cox regression analysis and used to construct the nomogram. The concordance index (C-index) of OS and CSS were 0.807 and 0.834 in the training set. Validation of the nomogram revealed that the receiver operating curve (ROC) maintained good discrimination, the decision curve analysis (DCA) had a high net benefit rate, and the calibration curves showed high consistency. Patients were grouped by the nomogram formula and the number of positive regional lymph nodes (NPR-Lymph node) to evaluate the therapeutic outcomes of chemotherapy, radiotherapy, neoadjuvant treatment and lymph node operation. Survival analysis revealed that chemotherapy could improve the prognosis for OS and CSS in the high-risk group and in the group with NPR-Lymph node counts above 1 (P < 0.05). Radiotherapy was associated with better OS and CSS in the intermediate-risk and high-risk groups, and in the group with NPR-Lymph node counts above 0 (P < 0.05). Lymphadenectomy was found to prolong OS and CSS in the high-risk group (P < 0.05), while neoadjuvant treatment did not prolong OS and CSS in any group. Thus, in this study, the nomogram for MEC patients treated with hysterectomy was successfully built and validated which could effectively predict the prognosis and identify at-risk population to guide clinical decision-making. The NPR-Lymph node was identified as a potentially strong prognostic indicator with good clinical value.
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Permafrost, characterized by its frozen soil, serves as a unique habitat for diverse microorganisms. Understanding these microbial communities is crucial for predicting the response of permafrost ecosystems to climate change. However, large-scale evidence regarding stratigraphic variations in microbial profiles remains limited. Here, we analyze microbial community structure and functional potential based on 16S rRNA gene amplicon sequencing and metagenomic data obtained from an â¼1000 km permafrost transect on the Tibetan Plateau. We find that microbial alpha diversity declines but beta diversity increases down the soil profile. Microbial assemblages are primarily governed by dispersal limitation and drift, with the importance of drift decreasing but that of dispersal limitation increasing with soil depth. Moreover, genes related to reduction reactions (e.g., ferric iron reduction, dissimilatory nitrate reduction, and denitrification) are enriched in the subsurface and permafrost layers. In addition, microbial groups involved in alternative electron accepting processes are more diverse and contribute highly to community-level metabolic profiles in the subsurface and permafrost layers, likely reflecting the lower redox potential and more complicated trophic strategies for microorganisms in deeper soils. Overall, these findings provide comprehensive insights into large-scale stratigraphic profiles of microbial community structure and functional potentials in permafrost regions.
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Metagenómica , Microbiota , Hielos Perennes , ARN Ribosómico 16S , Microbiología del Suelo , Hielos Perennes/microbiología , Tibet , ARN Ribosómico 16S/genética , Microbiota/genética , Bacterias/genética , Bacterias/clasificación , Bacterias/metabolismo , Suelo/química , Metagenoma , Ecosistema , Cambio Climático , Biodiversidad , FilogeniaRESUMEN
Enriching the active sites and enhancing the intrinsic activity of a single site are two basic strategies for improving the activity toward the electrocatalytic oxygen evolution reaction (OER), and designing an advanced microstructure with a boosted pre-oxidation process can further guarantee durability toward long-term catalysis. Herein, we propose a dual oxidation strategy of a Co Prussian blue analog (Co PBA), which simultaneously achieves Co3+ active site enrichment, in situ CeO2 decoration and lattice disordering with abundant undercoordinated sites, realizing highly efficient and ultrastable OER performance. The dual oxidation process can induce the enrichment of high-valence Co ions by combined chemical oxidation and d-f electron coupling compared to the singly oxidized catalysts, thereby providing more active sites with enhanced intrinsic activity for the early triggered OER process. In addition, the disordered lattice can provide abundant reactive Co sites for the pre-oxidation process, thereby leading to obvious activation of the catalysts and remarkable operational stability due to the substantially accumulated Co3+ sites. Benefitting from the structural advantages of lattice-disordered dual-oxidized Co PBA nanocages, a low overpotential of 240 mV can be achieved for a 10 mA cm-2 current density, and the large catalytic current density and intrinsic activity are among the best compared to those of previously reported PBA-based and PBA-derived catalysts and even RuO2 and IrO2. In addition, ultrastable OER behavior with a 263 % activity enhancement in 150 h can result, making the dual-oxidized catalyst a promising candidate for water electrolysis.
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Photochemical and biological degradation of dissolved organic carbon (DOC) and their interactions jointly contribute to the carbon dioxide released from surface waters in permafrost regions. However, the mechanisms that govern the coupled photochemical and biological degradation of DOC are still poorly understood in thermokarst lakes. Here, by combining Fourier transform ion cyclotron resonance mass spectrometry and microbial high-throughput sequencing, we conducted a sunlight and microbial degradation experiment using water samples collected from 10 thermokarst lakes along a 1100-km permafrost transect. We demonstrate that the enhancement of sunlight on DOC biodegradation is not associated with the low molecular weight aliphatics produced by sunlight, but driven by the photo-produced aromatics. This aromatic compound-driven acceleration of biodegradation may be attributed to the potential high abilities of the microbes to decompose complex compounds in thermokarst lakes. These findings highlight the importance of aromatics in regulating the sunlight effects on DOC biodegradation in permafrost-affected lakes.
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Lagos , Procesos Fotoquímicos , Materia Orgánica Disuelta , Lagos/microbiología , Compuestos Orgánicos , Hielos Perennes , Luz SolarRESUMEN
Understanding methane (CH4) emission from thermokarst lakes is crucial for predicting the impacts of abrupt thaw on the permafrost carbon-climate feedback. However, observational evidence, especially from high-altitude permafrost regions, is still scarce. Here, by combining field surveys, radio- and stable-carbon isotopic analyses, and metagenomic sequencing, we present multiple characteristics of CH4 emissions from 120 thermokarst lakes in 30 clusters along a 1100 km transect on the Tibetan Plateau. We find that thermokarst lakes have high CH4 emissions during the ice-free period (13.4 ± 1.5 mmol m-2 d-1; mean ± standard error) across this alpine permafrost region. Ebullition constitutes 84% of CH4 emissions, which are fueled primarily by young carbon decomposition through the hydrogenotrophic pathway. The relative abundances of methanogenic genes correspond to the observed CH4 fluxes. Overall, multiple parameters obtained in this study provide benchmarks for better predicting the strength of permafrost carbon-climate feedback in high-altitude permafrost regions.
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The electrocatalytic urea oxidation reaction (UOR) has attracted substantial research interests over the past few years owing to its critical role in coupled electrochemical systems for energy conversion, for example, coupling with the hydrogen evolution reaction (HER) to realize urea-assisted hydrogen production and assembling direct urea fuel cells (DUFC) by coupling with the oxygen reduction reaction (ORR). The UOR process has been proved to be a two-step process which involves an electrochemical pre-oxidation reaction of the metal sites and a subsequent chemical oxidation of the urea molecules on the as-formed high-valence metal sites. Hence, designing advanced (pre-)catalysts with a boosted pre-oxidation reaction is of great importance in improving the UOR performance and thus accelerating the coupled reactions. In this feature article, we discuss the significant role of the pre-oxidation process during the urea electro-oxidation reaction, and summarize detailed strategies and recent advances in promoting the pre-oxidation reaction, including the modulation of the crystallinity, active phase engineering, defect engineering, elemental incorporation and constructing hierarchical nanostructures. We anticipate that this feature article will offer helpful guidance for the design and optimization of advanced (pre-)catalysts for UOR and related energy conversion applications.
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In this work, cerium-incorporated Co-based catalysts encapsulated in nitrogen-doped carbon were fabricated for the electrocatalytic hydrazine oxidation reaction (HzOR). The Ce incorporation could lead to the formation of surface oxide nanolayers with a disordered lattice, endowing the catalyst with enriched active sites and enhanced intrinsic activity for promoted HzOR.
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In this work, Co-based nanocatalysts with variable degrees of sulfurization (DoS) were fabricated for the oxygen evolution reaction (OER). The partially sulfurized catalyst with a medium DoS could exhibit a promoted pre-oxidation process, leading to a highly efficient and ultrastable OER performance.
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Herein, hydrated copper pyrophosphate ultrathin nanosheets with a unique "pit-dot" nanostructure were fabricated as efficient pre-catalysts for the oxygen evolution reaction, and systematic post-catalytic characterization studies confirmed the important role of the boosted pre-oxidation reaction in promoting the OER catalysis.