Permafrost carbon cycle and its dynamics on the Tibetan Plateau.

Our knowledge on permafrost carbon (C) cycle is crucial for understanding its feedback to climate warming and developing nature-based solutions for mitigating climate change. To understand the characteristics of permafrost C cycle on the Tibetan Plateau, the largest alpine permafrost region around the world, we summarized recent advances including the stocks and fluxes of permafrost C and their responses to thawing, and depicted permafrost C dynamics within this century. We find that this alpine permafrost region stores approximately 14.1 Pg (1 Pg=1015 g) of soil organic C (SOC) in the top 3 m. Both substantial gaseous emissions and lateral C transport occur across this permafrost region. Moreover, the mobilization of frozen C is expedited by permafrost thaw, especially by the formation of thermokarst landscapes, which could release significant amounts of C into the atmosphere and surrounding water bodies. This alpine permafrost region nevertheless remains an important C sink, and its capacity to sequester C will continue to increase by 2100. For future perspectives, we would suggest developing long-term in situ observation networks of C stocks and fluxes with improved temporal and spatial coverage, and exploring the mechanisms underlying the response of ecosystem C cycle to permafrost thaw. In addition, it is essential to improve the projection of permafrost C dynamics through in-depth model-data fusion on the Tibetan Plateau.

Global turnover of soil mineral-associated and particulate organic carbon.

Soil organic carbon (SOC) persistence is predominantly governed by mineral protection, consequently, soil mineral-associated (MAOC) and particulate organic carbon (POC) turnovers have different impacts on the vulnerability of SOC to climate change. Here, we generate the global MAOC and POC maps using 8341 observations and then infer the turnover times of MAOC and POC by a data-model integration approach. Global MAOC and POC storages are 975 964 987 Pg C (mean with 5% and 95% quantiles) and 330 323 337 Pg C, while global mean MAOC and POC turnover times are 129 45 383 yr and 23 5 82 yr in the top meter, respectively. Climate warming-induced acceleration of MAOC and POC decomposition is greater in subsoil than that in topsoil. Overall, the global atlas of MAOC and POC turnover, together with the global distributions of MAOC and POC stocks, provide a benchmark for Earth system models to diagnose SOC-climate change feedback.

Preparation of Bispecific IgY-scFvs Inhibition Adherences of Enterotoxigenic Escherichia coli (K88 and F18) to Porcine IPEC-J2 Cell.

Enterotoxigenic Escherichia coli (ETEC) strains are significant contributors to postweaning diarrhea in piglets. Of the ETEC causing diarrhea, K88 and F18 accounted for 92.7%. Despite the prevalence of ETEC K88 and F18, there is currently no effective vaccine available due to the diversity of these strains. This study presents an innovative approach by isolating chicken-derived single-chain variable fragment antibodies (scFvs) specific to K88 and F18 fimbrial antigens from chickens immunized against these ETEC virulence factors. These scFvs effectively inhibited adhesion of K88 and F18 to porcine intestinal epithelial cells (IPEC-J2), with the inhibitory effect demonstrating a dose-dependent increase. Furthermore, a bispecific scFv was designed and expressed in Pichia pastoris. This engineered construct displayed remarkable potency; at a concentration of 25.08 µg, it significantly reduced the adhesion rate of ETEC strains to IPEC-J2 cells by 72.10% and 69.11% when challenged with either K88 or F18 alone. Even in the presence of both antigens, the adhesion rate was notably decreased by 57.92%. By targeting and impeding the initial adhesion step of ETEC pathogenesis, this antibody-based intervention holds promise as a potential alternative to antibiotics, thereby mitigating the risks associated with antibiotic resistance and residual drug contamination in livestock production. Overall, this study lays the groundwork for the development of innovative treatments against ETEC infections in piglets.

A national-scale assessment of land subsidence in China's major cities.

China's massive wave of urbanization may be threatened by land subsidence. Using a spaceborne synthetic aperture radar interferometry technique, we provided a systematic assessment of land subsidence in all of China's major cities from 2015 to 2022. Of the examined urban lands, 45% are subsiding faster than 3 millimeters per year, and 16% are subsiding faster than 10 millimeters per year, affecting 29 and 7% of the urban population, respectively. The subsidence appears to be associated with a range of factors such as groundwater withdrawal and the weight of buildings. By 2120, 22 to 26% of China's coastal lands will have a relative elevation lower than sea level, hosting 9 to 11% of the coastal population, because of the combined effect of city subsidence and sea-level rise. Our results underscore the necessity of enhancing protective measures to mitigate potential damages from subsidence.

Simultaneous detection of glycinin and ß-conglycinin in processed soybean products by high-performance liquid chromatography-tandem mass spectrometry with stable isotope-labeled standard peptides.

Glycinin and ß-conglycinin are the two main allergic proteins in soybean. Due to their complex structures and lack of protein standards, it is difficult to achieve quantitative determination of these proteins in soybeans. In this study, an HPLC-MS/MS method was developed for the simultaneous determination of five subunits of glycinin (G1, G2, G3, G4, and G5) and three subunits of ß-conglycinin (α, α', and ß) in processed soybean products based on 8 specific peptides and their stable isotope-labeled peptides. Here, each specific peptide was derived from one of the above 8 subunits. When soy protein was extracted and digested with trypsin, 8 specific peptides, and corresponding stable isotope-labeled peptides were analyzed by HPLC-MS/MS. The linear range for the specific peptides was between 3.2 and 1000 ng/mL (R2 > 0.9955). The recoveries of added peptides ranged from 83.4% to 117.8%, and the intra-day precisions (% CV) were below 17.4%. The limit of quantification of each subunit of glycinin and ß-conglycinin in processed soybean products (in terms of protein amount) was between 15.1 and 156.1 g/g. This method was successfully applied to the analysis of 8 subunits of glycinin and ß-conglycinin in 68 different processed soybean products, which provides technical support for processed product quality evaluation and monitoring soybean processing technology.

Accelerated organic matter decomposition in thermokarst lakes upon carbon and phosphorus inputs.

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.

Experimental warming altered plant functional traits and their coordination in a permafrost ecosystem.

Knowledge about changes in plant functional traits is valuable for the mechanistic understanding of warming effects on ecosystem functions. However, observations have tended to focus on aboveground plant traits, and there is little information about changes in belowground plant traits or the coordination of above- and belowground traits under climate warming, particularly in permafrost ecosystems. Based on a 7-yr field warming experiment, we measured 26 above- and belowground plant traits of four dominant species, and explored community functional composition and trait networks in response to experimental warming in a permafrost ecosystem on the Tibetan Plateau. Experimental warming shifted community-level functional traits toward more acquisitive values, with earlier green-up, greater plant height, larger leaves, higher photosynthetic resource-use efficiency, thinner roots, and greater specific root length and root nutrient concentrations. However, warming had a negligible effect in terms of functional diversity. In addition, warming shifted hub traits which have the highest centrality in the network from specific root area to leaf area. These results demonstrate that above- and belowground traits exhibit consistent adaptive strategies, with more acquisitive traits in warmer environments. Such changes could provide an adaptive advantage for plants in response to environmental change.

Photo-produced aromatic compounds stimulate microbial degradation of dissolved organic carbon in thermokarst lakes.

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.

Characteristics of methane emissions from alpine thermokarst lakes on the Tibetan Plateau.

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.

Priming effect stimulates carbon release from thawed permafrost.

Climate warming leads to widespread permafrost thaw with a fraction of the thawed permafrost carbon (C) being released as carbon dioxide (CO2 ), thus triggering a positive permafrost C-climate feedback. However, large uncertainty exists in the size of this model-projected feedback, partly owing to the limited understanding of permafrost CO2 release through the priming effect (i.e., the stimulation of soil organic matter decomposition by external C inputs) upon thaw. By combining permafrost sampling from 24 sites on the Tibetan Plateau and laboratory incubation, we detected an overall positive priming effect (an increase in soil C decomposition by up to 31%) upon permafrost thaw, which increased with permafrost C density (C storage per area). We then assessed the magnitude of thawed permafrost C under future climate scenarios by coupling increases in active layer thickness over half a century with spatial and vertical distributions of soil C density. The thawed C stocks in the top 3 m of soils from the present (2000-2015) to the future period (2061-2080) were estimated at 1.0 (95% confidence interval (CI): 0.8-1.2) and 1.3 (95% CI: 1.0-1.7) Pg (1 Pg = 1015 g) C under moderate and high Representative Concentration Pathway (RCP) scenarios 4.5 and 8.5, respectively. We further predicted permafrost priming effect potential (priming intensity under optimal conditions) based on the thawed C and the empirical relationship between the priming effect and permafrost C density. By the period 2061-2080, the regional priming potentials could be 8.8 (95% CI: 7.4-10.2) and 10.0 (95% CI: 8.3-11.6) Tg (1 Tg = 1012 g) C year-1 under the RCP 4.5 and RCP 8.5 scenarios, respectively. This large CO2 emission potential induced by the priming effect highlights the complex permafrost C dynamics upon thaw, potentially reinforcing permafrost C-climate feedback.

Microbial nitrogen and phosphorus co-limitation across permafrost region.

The status of plant and microbial nutrient limitation have profound impacts on ecosystem carbon cycle in permafrost areas, which store large amounts of carbon and experience pronounced climatic warming. Despite the long-term standing paradigm assumes that cold ecosystems primarily have nitrogen deficiency, large-scale empirical tests of microbial nutrient limitation are lacking. Here we assessed the potential microbial nutrient limitation across the Tibetan alpine permafrost region, using the combination of enzymatic and elemental stoichiometry, genes abundance and fertilization method. In contrast with the traditional view, the four independent approaches congruently detected widespread microbial nitrogen and phosphorus co-limitation in both the surface soil and deep permafrost deposits, with stronger limitation in the topsoil. Further analysis revealed that soil resources stoichiometry and microbial community composition were the two best predictors of the magnitude of microbial nutrient limitation. High ratio of available soil carbon to nutrient and low fungal/bacterial ratio corresponded to strong microbial nutrient limitation. These findings suggest that warming-induced enhancement in soil nutrient availability could stimulate microbial activity, and probably amplify soil carbon losses from permafrost areas.

Spatially explicit estimate of nitrogen effects on soil respiration across the globe.

Soil respiration (Rs), as the second largest flux of carbon dioxide (CO2 ) between terrestrial ecosystems and the atmosphere, is vulnerable to global nitrogen (N) enrichment. However, the global distribution of the N effects on Rs remains uncertain. Here, we compiled a new database containing 1282 observations of Rs and its heterotrophic component (Rh) in field N manipulative experiments from 317 published papers. Using this up-to-date database, we first performed a formal meta-analysis to explore the responses of Rs and Rh to N addition, and then presented a global spatially explicit quantification of the N effects using a Random Forest model. Our results showed that experimental N addition significantly increased Rs but had a minimal impact on Rh, not supporting the prevailing view that N enrichment inhibits soil microbial respiration. For the major biomes, the magnitude of N input was the main determinant of the spatial variation in Rs response, while the most important predictors for Rh response were biome specific. Based on the key predictors, global mapping visually demonstrated a positive N effect in the regions with higher anthropogenic N inputs (i.e., atmospheric N deposition and agricultural fertilization). Overall, our analysis not only provides novel insight into the N effects on soil CO2 fluxes, but also presents a spatially explicit assessment of the N effects at the global scale, which are pivotal for understanding ecosystem carbon dynamics in future scenarios with more frequent anthropogenic activities.

Hot moment of N2O emissions in seasonally frozen peatlands.

Since the start of the Anthropocene, northern seasonally frozen peatlands have been warming at a rate of 0.6 °C per decade, twice that of the Earth's average rate, thereby triggering increased nitrogen mineralization with subsequent potentially large losses of nitrous oxide (N2O) to the atmosphere. Here we provide evidence that seasonally frozen peatlands are important N2O emission sources in the Northern Hemisphere and the thawing periods are the hot moment of annual N2O emissions. The flux during the hot moment of thawing in spring was 1.20 ± 0.82 mg N2O m-2 d-1, significantly higher than that during the other periods (freezing, -0.12 ± 0.02 mg N2O m-2 d-1; frozen, 0.04 ± 0.04 mg N2O m-2 d-1; thawed, 0.09 ± 0.01 mg N2O m-2 d-1) or observed for other ecosystems at the same latitude in previous studies. The observed emission flux is even higher than those of tropical forests, the World's largest natural terrestrial N2O source. Furthermore, based on soil incubation with 15N and 18O isotope tracing and differential inhibitors, heterotrophic bacterial and fungal denitrification was revealed as the main source of N2O in peatland profiles (0-200 cm). Metagenomic, metatranscriptomic, and qPCR assays further revealed that seasonally frozen peatlands have high N2O emission potential, but thawing significantly stimulates expression of genes encoding N2O-producing protein complexes (hydroxylamine dehydrogenase (hao) and nitric oxide reductase (nor)), resulting in high N2O emissions during spring. This hot moment converts seasonally frozen peatlands into an important N2O emission source when it is otherwise a sink. Extrapolation of our data to all northern peatland areas reveals that the hot moment emissions could amount to approximately 0.17 Tg of N2O yr-1. However, these N2O emissions are still not routinely included in Earth system models and global IPCC assessments.

Patterns and drivers of anaerobic nitrogen transformations in sediments of thermokarst lakes.

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.

A globally relevant stock of soil nitrogen in the Yedoma permafrost domain.

Nitrogen regulates multiple aspects of the permafrost climate feedback, including plant growth, organic matter decomposition, and the production of the potent greenhouse gas nitrous oxide. Despite its importance, current estimates of permafrost nitrogen are highly uncertain. Here, we compiled a dataset of >2000 samples to quantify nitrogen stocks in the Yedoma domain, a region with organic-rich permafrost that contains ~25% of all permafrost carbon. We estimate that the Yedoma domain contains 41.2 gigatons of nitrogen down to ~20 metre for the deepest unit, which increases the previous estimate for the entire permafrost zone by ~46%. Approximately 90% of this nitrogen (37 gigatons) is stored in permafrost and therefore currently immobile and frozen. Here, we show that of this amount, ¾ is stored >3 metre depth, but if partially mobilised by thaw, this large nitrogen pool could have continental-scale consequences for soil and aquatic biogeochemistry and global-scale consequences for the permafrost feedback.

Global soil profiles indicate depth-dependent soil carbon losses under a warmer climate.

Soil organic carbon (SOC) changes under future climate warming are difficult to quantify in situ. Here we apply an innovative approach combining space-for-time substitution with meta-analysis to SOC measurements in 113,013 soil profiles across the globe to estimate the effect of future climate warming on steady-state SOC stocks. We find that SOC stock will reduce by 6.0 ± 1.6% (mean±95% confidence interval), 4.8 ± 2.3% and 1.3 ± 4.0% at 0-0.3, 0.3-1 and 1-2 m soil depths, respectively, under 1 °C air warming, with additional 4.2%, 2.2% and 1.4% losses per every additional 1 °C warming, respectively. The largest proportional SOC losses occur in boreal forests. Existing SOC level is the predominant determinant of the spatial variability of SOC changes with higher percentage losses in SOC-rich soils. Our work demonstrates that warming induces more proportional SOC losses in topsoil than in subsoil, particularly from high-latitudinal SOC-rich systems.

Divergent changes in particulate and mineral-associated organic carbon upon permafrost thaw.

Permafrost thaw can stimulate microbial decomposition and induce soil carbon (C) loss, potentially triggering a positive C-climate feedback. However, earlier observations have concentrated on bulk soil C dynamics upon permafrost thaw, with limited evidence involving soil C fractions. Here, we explore how the functionally distinct fractions, including particulate and mineral-associated organic C (POC and MAOC) as well as iron-bound organic C (OC-Fe), respond to permafrost thaw using systematic measurements derived from one permafrost thaw sequence and five additional thermokarst-impacted sites on the Tibetan Plateau. We find that topsoil POC content substantially decreases, while MAOC content remains stable and OC-Fe accumulates due to the enriched Fe oxides after permafrost thaw. Moreover, the proportion of MAOC and OC-Fe increases along the thaw sequence and at most of the thermokarst-impacted sites. The relatively enriched stable soil C fractions would alleviate microbial decomposition and weaken its feedback to climate warming over long-term thermokarst development.

Nitrogen input enhances microbial carbon use efficiency by altering plant-microbe-mineral interactions.

Microbial growth and respiration are at the core of the soil carbon (C) cycle, as these microbial physiological performances ultimately determine the fate of soil C. Microbial C use efficiency (CUE), a critical metric to characterize the partitioning of C between microbial growth and respiration, thus controls the sign and magnitude of soil C-climate feedback. Despite its importance, the response of CUE to nitrogen (N) input and the relevant regulatory mechanisms remain poorly understood, leading to large uncertainties in predicting soil C dynamics under continuous N input. By combining a multi-level field N addition experiment with a substrate-independent 18 O-H2 O labelling approach as well as high-throughput sequencing and mineral analysis, here we elucidated how N-induced changes in plant-microbial-mineral interactions drove the responses of microbial CUE to N input. We found that microbial CUE increased significantly as a consequence of enhanced microbial growth after 6-year N addition. In contrast to the prevailing view, the elevated microbial growth and CUE were not mainly driven by the reduced stoichiometric imbalance, but strongly associated with the increased soil C accessibility from weakened mineral protection. Such attenuated organo-mineral association was further linked to the N-induced changes in the plant community and the increased oxalic acid in the soil. These findings provide empirical evidence for the tight linkage between mineral-associated C dynamics and microbial physiology, highlighting the need to disentangle the complex plant-microbe-mineral interactions to improve soil C prediction under anthropogenic N input.

Divergent Trajectory of Soil Autotrophic and Heterotrophic Respiration upon Permafrost Thaw.

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.

Substantial non-growing season carbon dioxide loss across Tibetan alpine permafrost region.

One of the major uncertainties for projecting permafrost carbon (C)-climate feedback is a poor representation of the non-growing season carbon dioxide (CO2 ) emissions under a changing climate. Here, combining in situ field observations, regional synthesis and a random forest model, we assessed contemporary and future soil respired CO2 (i.e., soil respiration, Rs ) across the Tibetan alpine permafrost region, which has received much less attention compared with the Arctic permafrost domain. We estimated the regional mean Rs of 229.8, 72.9 and 302.7 g C m-2  year-1 during growing season, non-growing season and the entire year, respectively; corresponding to the contemporary losses of 296.9, 94.3 and 391.2 Tg C year-1 from this high-altitude permafrost-affected area. The non-growing season Rs accounted for a quarter of the annual soil CO2 efflux. Different from the prevailing view that temperature is the most limiting factor for cold-period CO2 release in Arctic permafrost ecosystems, precipitation determined the spatial pattern of non-growing season Rs on the Tibetan Plateau. Using the key predictors, model extrapolation demonstrated additional losses of 38.8 and 74.5 Tg C from the non-growing season for a moderate mitigation scenario and a business-as-usual emissions scenario, respectively. These results provide a baseline for non-growing season CO2 emissions from high-altitude permafrost areas and help for accurate projection of permafrost C-climate feedback.