Understanding the dynamics of soil respiration (Rs) in response to freeze-thaw cycles is crucial due to permafrost degradation on the Qinghai-Tibet Plateau (QTP). We conducted continuous in situ observations of Rs using an Li-8150 automated soil CO2 flux system, categorizing the freeze-thaw cycle into four stages: completely thawed (CT), autumn freeze-thaw (AFT), completely frozen (CF), and spring freeze-thaw (SFT). Our results revealed distinct differences in Rs magnitudes, diurnal patterns, and controlling factors across these stages, attributed to varying thermal regimes. The mean Rs values were as follows: 2.51 (1.10) mu mol center dot m(-2)center dot s(-1) (CT), 0.37 (0.04) mu mol center dot m(-2)center dot s(-1) (AFT), 0.19 (0.06) mu mol center dot m(-2)center dot s(-1) (CF), and 0.68 (0.19) mu mol center dot m(-2)center dot s(-1) (SFT). Cumulatively, the Rs contributions to annual totals were 89.32% (CT), 0.79% (AFT), 5.01% (CF), and 4.88% (SFT). Notably, the temperature sensitivity (Q10) value during SFT was 2.79 times greater than that in CT (4.63), underscoring the significance of CO2 emissions during spring warming. Soil temperature was the primary driver of Rs in the CT stage, while soil moisture at 5 cm depth and solar radiation significantly influenced Rs during SFT. Our findings suggest that global warming will alter seasonal Rs patterns as freeze-thaw phases evolve, emphasizing the need to monitor CO2 emissions from alpine meadow ecosystems during spring.

Environmental changes, such as climate warming and higher herbivory pressure, are altering the carbon balance of Arctic ecosystems; yet, how these drivers modify the carbon balance among different habitats remains uncertain. This hampers our ability to predict changes in the carbon sink strength of tundra ecosystems. We investigated how spring goose grubbing and summer warming-two key environmental-change drivers in the Arctic-alter CO2 fluxes in three tundra habitats varying in soil moisture and plant-community composition. In a full-factorial experiment in high-Arctic Svalbard, we simulated grubbing and warming over two years and determined summer net ecosystem exchange (NEE) alongside its components: gross ecosystem productivity (GEP) and ecosystem respiration (ER). After two years, we found net CO2 uptake to be suppressed by both drivers depending on habitat. CO2 uptake was reduced by warming in mesic habitats, by warming and grubbing in moist habitats, and by grubbing in wet habitats. In mesic habitats, warming stimulated ER (+75%) more than GEP (+30%), leading to a 7.5-fold increase in their CO2 source strength. In moist habitats, grubbing decreased GEP and ER by similar to 55%, while warming increased them by similar to 35%, with no changes in summer-long NEE. Nevertheless, grubbing offset peak summer CO2 uptake and warming led to a twofold increase in late summer CO2 source strength. In wet habitats, grubbing reduced GEP (-40%) more than ER (-30%), weakening their CO2 sink strength by 70%. One-year CO2-flux responses were similar to two-year responses, and the effect of simulated grubbing was consistent with that of natural grubbing. CO2-flux rates were positively related to aboveground net primary productivity and temperature. Net ecosystem CO2 uptake started occurring above similar to 70% soil moisture content, primarily due to a decline in ER. Herein, we reveal that key environmental-change drivers-goose grubbing by decreasing GEP more than ER and warming by enhancing ER more than GEP-consistently suppress net tundra CO2 uptake, although their relative strength differs among habitats. By identifying how and where grubbing and higher temperatures alter CO2 fluxes across the heterogeneous Arctic landscape, our results have implications for predicting the tundra carbon balance under increasing numbers of geese in a warmer Arctic.

Freeze-thaw (FT) events profoundly perturb the biochemical processes of soil and water in mid- and high-latitude regions, especially the riparian zones that are often recognized as the hotspots of soil-water interactions and thus one of the most sensitive ecosystems to future climate change. However, it remains largely unknown how the heterogeneously composed and progressively discharged meltwater affect the biochemical cycling of the neighbor soil. In this study, stream water from a valley in the Chinese Loess Plateau was frozen at -10 degrees C for 12 hours, and the meltwater (at +10 degrees C) progressively discharged at three stages (T1 similar to T3) was respectively added to rewet the soil collected from the same stream bed (Soil+T1 similar to Soil+T3). Our results show that: (1) Approximately 65% of the total dissolved organic carbon and 53% of the total NO3--N were preferentially discharged at the first stage T1, with enrichment ratios of 1.60 similar to 1.94. (2) The dissolved organic matter discharged at T1 was noticeably more biodegradable with significantly lower SUVA(254) but higher HIX, and also predominated with humic-like, dissolved microbial metabolite-like, and fulvic acid-like components. (3) After added to the soil, the meltwater discharged at T1 (e.g., Soil+T1) significantly accelerated the mineralization of soil organic carbon with 2.4 similar to 8.07-folded k factor after fitted into the first-order kinetics equation, triggering 125 similar to 152% more total CO2 emissions. Adding T1 also promoted significantly more accumulation of soil microbial biomass carbon after 15 days of incubation, especially on the FT soil. Overall, the preferential discharge of the nutrient-enriched meltwater with more biodegradable DOM components at the initial melting stage significantly promoted the microbial growth and respiratory activities in the recipient soil, and triggered sizable CO2 emission pulses. This reveals a common but long-ignored phenomenon in cold riparian zones, where progressive freeze-thaw can partition and thus shift the DOM compositions in stream water over melting time, and in turn profoundly perturb the biochemical cycles of the neighbor soil body.

目的 水合物法封存CO2稳定性良好、储气密度高，是一种极具潜力的碳封存方式，利用冻土区的地层条件更具独特优势，将CO2气体注入冻土区地层中，在一定的温度和压力条件下，形成固态CO2水合物实现封存。方法 依据国内冻土地区地层深度对应的温度和压力条件，选取不同地层深度（150 m和200 m）对应温度（1.27℃和2.72℃）和有效孔隙含水率（40%）,研究不同注气压力（3.5 MPa、4.5 MPa和5.5 MPa）下的封存特征。分析封存过程的温度和压力变化、封存速率、最终水转化率和最终封存率等动力学规律。结果 封存压力越高，水合物法封存所需的诱导时间越短，压力降幅越大。较高的封存压力导致初期封存速率较慢，缓慢封存期的持续时间减少，且封存压力越高，封存率、最终水转化率和水合物相饱和度越高。封存温度越高，压力对封存率的影响效果越明显。结论 在地层深度150 m（对应地层平均温度1.27℃）、5.5 MPa及有效孔隙含水率（40%）的条件下，CO2封存效果最佳。

Significant progress in permafrost carbon science made over the past decades include the identification of vast permafrost carbon stocks, the development of new pan-Arctic permafrost maps, an increase in terrestrial measurement sites for CO2 and methane fluxes, and important factors affecting carbon cycling, including vegetation changes, periods of soil freezing and thawing, wildfire, and other disturbance events. Process-based modeling studies now include key elements of permafrost carbon cycling and advances in statistical modeling and inverse modeling enhance understanding of permafrost region C budgets. By combining existing data syntheses and model outputs, the permafrost region is likely a wetland methane source and small terrestrial ecosystem CO2 sink with lower net CO2 uptake toward higher latitudes, excluding wildfire emissions. For 2002-2014, the strongest CO2 sink was located in western Canada (median: -52 g C m-2 y-1) and smallest sinks in Alaska, Canadian tundra, and Siberian tundra (medians: -5 to -9 g C m-2 y-1). Eurasian regions had the largest median wetland methane fluxes (16-18 g CH4 m-2 y-1). Quantifying the regional scale carbon balance remains challenging because of high spatial and temporal variability and relatively low density of observations. More accurate permafrost region carbon fluxes require: (a) the development of better maps characterizing wetlands and dynamics of vegetation and disturbances, including abrupt permafrost thaw; (b) the establishment of new year-round CO2 and methane flux sites in underrepresented areas; and (c) improved models that better represent important permafrost carbon cycle dynamics, including non-growing season emissions and disturbance effects. Climate change and the consequent thawing of permafrost threatens to transform the permafrost region from a carbon sink into a carbon source, posing a challenge to global climate goals. Numerous studies over the past decades have identified important factors affecting carbon cycling, including vegetation changes, periods of soil freezing and thawing, wildfire, and other disturbance events. Overall, studies show high wetland methane emissions and a small net carbon dioxide sink strength over the terrestrial permafrost region but results differ among modeling and upscaling approaches. Continued and coordinated efforts among field, modeling, and remote sensing communities are needed to integrate new knowledge from observations to modeling and predictions and finally to policy. Rapid warming of northern permafrost region threatens ecosystems, soil carbon stocks, and global climate targets Long-term observations show importance of disturbance and cold season periods but are unable to detect spatiotemporal trends in C flux Combined modeling and syntheses show the permafrost region is a small terrestrial CO2 sink with large spatial variability and net CH4 source

土壤碳通量是森林生态系统碳循环的重要组成部分，根系对土壤碳通量起着关键作用，研究根系对土壤碳通量的影响对寒温带冻土区温室气体研究有重要意义。以杜香-兴安落叶松林（DXL）、杜鹃-兴安落叶松林（DJL）和苔藓-兴安落叶松林（TXL）为研究对象，通过壕沟法进行断根处理，采用便携式土壤呼吸仪G4301对土壤碳通量进行日动态和月动态变化测定与分析。结果表明：6—11月，断根对DXL和DJL土壤CH4的吸收起抑制作用，降幅分别为15.16%—54.31%和11.26%—33.84%,对TXL土壤CH4的排放起促进作用，增幅为19.22%—75.52%;对3种类型兴安落叶松林土壤CO2的排放均起抑制作用，其中对TXL影响最大，对土壤CO2降幅为32.29%—87.62%。断根对DXL和TXL土壤CH4的影响在8月最为显著，增幅分别为-54.31%和75.52%,DJL在11月影响最为显著，降幅为33.84%。断根对3种类型兴安落叶松林土壤CO2排放的影响在6—11月均...

北方内陆水体是温室气体排放的热点，对量化区域碳收支起重要作用，但其排放的季节变化尚不清楚。观测了大兴安岭多年冻土区府库奇河及其改道形成的牛轭湖（演替晚期）冻结期冰层中储存的二氧化碳（CO2）和甲烷（CH4）浓度，并比较了两种水体中CO2和CH4浓度在三个不同时期（冻结期、非冻结期、春季融化）的差异。结果表明：两种水体CO2和CH4浓度季节变化存在差异。牛轭湖在冻结期水体中CO2和CH4浓度最高，有明显的冰下积累现象，其中CH4浓度平均值为（2.21±0.54）μmo/L,分别是非冻结期和春季融化期水体CH4浓度的5倍和14倍。河流水体中CO2和CH4浓度最高出现在春季融化期，显著高于非冻结期和冻结期（P<0.05）。水中CO2和CH4浓度受多种环境因子的影响，与可溶性有机碳（D...

水合物法二氧化碳封存是目前具有潜力的碳封存方式之一，将一定压力的CO2气体注入冻土带的沉积层中，在特定的地层温度条件下CO2气体可形成CO2水合物从而达到长期稳定封存的目的。依据我国多年冻土地区地层的温压条件，选取冻土地区不同地层深度（110,150,200,250,300,350 m）对应的温度（0,1.27,2.72,4.53,6.38,8.70℃）进行了CO2水合物封存实验。实验结果表明：在快速合成阶段实验温度为1.27℃下反应釜内温度上升幅度最大，生成速度最快，最终储气率最高，缓慢合成期持续时间随温度的升高而减少。在较低温度下（0和1.27℃）水合物的各相饱和度基本保持在约18%（水合物相）、15%（水相）和67%（气相）。在地层深度为150 m时（平均温度1.27℃）封存CO2效果优于其他深度的地层。

Ongoing studies conducted in northern polar regions reveal that permafrost stability plays a key role in the modern carbon cycle as it potentially stores considerable quantities of greenhouse gases. Rapid and recent warming of the Arc-tic permafrost is resulting in significant greenhouse gas emissions, both from physical and microbial processes. The po-tential impact of greenhouse gas release from the Antarctic region has not, to date, been investigated. In Antarctica, the McMurdo Dry Valleys comprise 10 % of the ice-free soil surface areas in Antarctica and like the northern polar regions are also warming albeit at a slower rate.The work presented herein examines a comprehensive sample suite of soil gas (e.g., CO2, CH4 and He) concentrations and CO2 flux measurements conducted in Taylor Valley during austral summer 2019/2020. Analytical results reveal the presence of significant concentrations of CO2, CH4 and He (up to 3.44 vol%, 18,447 ppmv and 6.49 ppmv, respec-tively) at the base of the active layer. When compared with the few previously obtained measurements, we observe increased CO2 flux rates (estimated CO2 emissions in the study area of 21.6 km2 approximate to 15 tons day-1). We suggest that the gas source is connected with the deep brines migrating from inland (potentially from beneath the Antarctic Ice Sheet) towards the coast beneath the permafrost layer. These data provide a baseline for future investigations aimed at monitoring the changing rate of greenhouse gas emissions from Antarctic permafrost, and the potential origin of gases, as the southern polar region warms.

Short-lived climate pollutants (SLCPs) including methane, tropospheric ozone, and black carbon in this work, is a set of compounds with shorter lifetimes than carbon dioxide (CO2) and can cause warming effect on climate. Here, the effective radiative forcing (ERF) is estimated by using an online aerosol-climate model (BCC_AGCM2.0_CUACE/Aero); then the climate responses to SLCPs concentration changes from the pre-industrial era to the present (1850-2010) are estimated. The global annual mean ERF of SLCPs was estimated to be 0.99 [0.79-1.20] W m(-2), and led to warming effects over most parts of the globe, with the warming center (about 1.0 K increase) being located in the mid-high latitudes of the Northern Hemisphere (NH) and the ocean around Antarctica. The changes in annual mean surface air temperature (SAT) caused by SLCPs changes were more prominent in the NH [0.78 (0.62-0.94) K] than in the Southern Hemisphere [0.62 (0.45-0.74) K], and the global annual mean value is 0.70 K. By looking at other variable responses, we found that precipitation had been increased by about 0.10 mm d(-1) in mid- and high-latitudes and decreased by about 0.20 mm d(-1) in subtropical regions, with the global annual mean value of 0.02 mm d(-1). Changes in SLCPs also influenced atmospheric circulation change, a northward shift in the Intertropical Convergence Zone was induced due to the interhemispheric asymmetry in SAT. However, it is found in this work that SLCPs changes had little effect on global average cloud cover, whereas the local cloud cover changes could not be ignored, low cloud cover increase by about 2.5% over high latitudes in the NH and the ribbon area near 60 degrees S, and high cloud cover increased by more than 2.0% over northern Africa and the Indian Ocean. Finally, we compared the ERFs and global and regional warming effects of SLCPs with those induced by CO2 changes. From 1850 to the present, the ERF of SLCPs was equivalent to 66%, 83%, and 50% of that of CO2 in global, NH, and SH mean, respectively. The increases in SAT caused by SLCPs were 43% and 55% of those by CO2 over the globe and China, respectively.