Carbon Sink Research Articles

New insights into controlling factors of organic matter enrichment in Carboniferous−Permian shales based on machine learning

Shale deposits constitute Earth’s largest and most stable organic carbon reservoir. Organic matter enrichment of fine-grained sediments is paramount for carbon sink research and oil and gas exploration. The Carboniferous to Permian interval, an especially critical period in Earth’s ecosystem evolution that encompassed the late Paleozoic ice age, witnessed widespread accumulation of organic-rich shale. However, the mechanisms driving organic matter enrichment and the role of organic carbon burial as a carbon sink during this period remain contentious. Our study focuses on upper Carboniferous and lower Permian shale deposited on the North China Block (NCB). A total of 370 elemental geochemical datasets were obtained to elucidate paleoenvironmental conditions associated with these deposits. We employed random forest (RF) and artificial neural network (ANN) algorithms to elucidate the controlling mechanisms of organic matter enrichment during this time period and to offer a quantitative assessment of the magnitude of organic carbon burial. Our results suggest that upper Carboniferous and lower Permian shale accumulated contemporaneous with a dominantly warm, humid climate that experienced episodes of cooler, drier conditions. The water column exhibited low primary surface productivity, oxic-suboxic, saline water conditions, and elevated terrigenous input and sedimentation rates. RF and ANN analysis reveals that paleoclimate was the dominant factor influencing organic matter enrichment of fine-grained sediments during this time. The inferred warm, humid climate not only promoted enhanced organic carbon production but also favored increased delivery of organic matter as a result of increased chemical weathering and associated terrestrial input to the basin. Concurrently, elevated sedimentation rates and the establishment of saline water conditions facilitated enhanced preservation of deposited organic matter. Organic carbon burial associated with accumulation of the upper Carboniferous and lower Permian shale succession of the NCB reached 95.5 × 103 PgC. These deposits appear to have served as a significant carbon sink based on an estimated organic carbon burial rate of shale containing total organic carbon >6% of as great as 65.6 gC/m2/yr. Results of the present study enhance our understanding of the carbon cycle during the Carboniferous to Permian interval and provide guidance for shale gas exploration and development of Carboniferous and Permian shale deposits.

Ecosystem carbon stock variation along forest stand ages: insight from eastern coast mangrove ecosystem of India

BackgroundThe mangrove ecosystem has the highest carbon sink potential which significantly contributes to bringing carbon neutrality. Understanding the carbon stock dynamics along the age of forest stands in the mangrove forest ecosystem is of significance for managing the forests and their carbon accumulation. This study aimed to estimate the forest structural attributes, biomass and total ecosystem carbon stock (TECS) of old natural (age > 50 years) and young planted (age ~ 20 years) mangrove forest stands at Bichitrapur Mangrove Reserve Forest in eastern coast of India. We also attempted to understand the interrelationship of structural attributes, biomass and soil properties in the mangrove forests. To achieve the results, twenty random plots were established (size: 20 m × 25 m) and suitable allometric equations along with species-specific wood density values were used to estimate the biomass and carbon stock.ResultsAltogether, 29 plant species (18 exclusive and 11 associate species) were recorded. The mean total biomass (± SE) and soil organic carbon (at 30 cm depth) were 165.31 ± 20.89 t ha−1 and 40.20 ± 1.24 t C ha−1 for young stands, and 586.12 ± 56.74 t ha−1 and 49.68 ± 2.39 t C ha−1 for old stands, respectively. Among mangrove species, Avicennia marina contributed the highest vegetation biomass in both forest stands (59.72 t ha−1 and 262.28 t ha−1 in young and old stands, respectively), followed by Avicennia officinalis (35.05 t ha−1) and Sonneratia apetala (26.09 t ha−1) in young stand and Avicennia alba (169.28 t ha−1) and Avicennia officinalis (115.58 t ha−1) in old stand. The mean TECS was 235.62 ± 27.34 t C ha−1. The contribution of vegetation and soil to TECS was 63% and 37% in the young stand, whereas in the old stand it was 83% and 17%, respectively. The correlation analyses revealed that mean stand height (r = 0.87), basal area (r = 0.99), soil nitrogen (r = 0.76), potassium (r = 0.78), and carbon (r = 0.80) were significantly positively correlated with total biomass at p < 0.01.ConclusionsOur results demonstrate that old mangrove forest stands store substantially high carbon stock than young planted forest stands, implying the role of forest age in determining the carbon storage potential of mangrove ecosystems.

Future Wood Availability in Europe in Light of Climate and Energy Policy and Geopolitical Developments—A Wood Resource Balance-Based Assessment

The amended European Union (EU) Renewable Energy Directive—in aiming to increase the share of renewable energy in overall energy consumption—promotes an increased demand for wood, while the EU’s updated Land Use, Land-Use Change, and Forestry (LULUCF) Regulation sets ambitious, binding national targets for the increase in net greenhouse gas removals that could restrict the supply of wood. Additionally, the ongoing war in Ukraine has directly affected the availability of woody biomass in Europe through the EU’s import ban on timber and timber products from Russia and Belarus. This paper provides an in-depth comparative analysis of sources and uses of woody biomass in four European regions in light of these recent climate and energy policies and geopolitical developments. The analysis indicates significantly underestimated reported removals in three of the four European regions studied. Further, projections suggest policy incoherence between current climate and energy objectives until 2030 in all four regions, as fellings increase at a faster rate than net annual increment in all four regions, decreasing the forest carbon sink and thus making it all but impossible to reach the 2030 target of the LULUCF regulation. However, between 2030 and 2040, energy-related fellings could decrease in regions north and west, while they could continue to grow in regions east and south, albeit at a lower rate.

Spatiotemporal Analysis, Predictive Modeling, and Driving Mechanism Investigation of Carbon Storage Dynamics in Changde City Under the Framework of LUCC

In the context of the worldwide attention on climate change, examining how land use relates to the carbon sink functions of regions is essential. This research innovatively utilizes the 2000–2020 land use data of Changde City, integrating the PLUS and InVEST models to analyze spatiotemporal changes and predict scenarios. It also combines the parameter geodetector and multiscale geographically weighted regression model to dissect driving factor distributions and mechanisms, capture interactions and multiscale impacts, uncover underlying laws, pioneer new paths for similar studies, and support regional ecological sustainability. The results show that from 2000–2020, forest and arable land areas declined while construction land expanded, leading to a yij1,172,200-ton carbon storage reduction in Changde City. Carbon storage decreased under natural development and arable land protection scenarios but increased in the ecological scenario. The main drivers of carbon storage in Changde City are the DEM, slope, and annual average temperature, with their interactions enhancing spatial heterogeneity. Human activities, especially in mountains and urbanizing regions, negatively impact carbon storage. This study aids in optimizing land resource allocation, improving land use efficiency, and promoting coordinated and sustainable development in Changde City’s ecological, economic, and social systems.

Primary Mid-Succession Carbon Fluxes in a Spontaneously Recovering Post-Mining Ecosystem

Limited research exists on the carbon sequestration potential of spontaneously developing post-coal-mining sites in the mid-stage of primary succession. Therefore, in 2023, net ecosystem exchange (NEE) was quantified in Czechia using an eddy covariance (EC) tower to assess carbon fluxes in a spontaneously developing ecosystem dominated by pioneer tree species such as willow, along with aspen and birch, growing on a wave-like microtopography. The ecosystem functioned as a strong carbon sink, with an annual NEE of −415 g C m−2 yr−1, ~39 years after coal mining. This NEE was derived by gross ecosystem exchange (GEE) of −1423 g C m−2 yr−1 and ecosystem respiration (Reco) of 1008 g C m−2 yr−1. Seasonal variation was driven by higher GEE in summer rather than by Reco. Consequently, Reco accounted for ca. 51% of GEE in summer, compared to 56% in spring. In addition, temperature was an important climatic factor in spring, whereas vapor pressure deficit (VPD) and global radiation (Rg) were more critical in summer. Overall, our results highlight the robust carbon sequestration capacity of naturally developing pioneer forests, suggesting their potential role in restoring mined areas in Central Europe and other regions without water limitations following coal mining.

Estimating Soil Carbon Sequestration Potential in Portuguese Agricultural Soils Through Land-Management and Land-Use Changes

Soil carbon sequestration (SCS) is a nature-based, low-cost climate mitigation strategy that also contributes to the climate adaptation of agricultural systems. Some land-use and land-management practices potentially lead to an enhancement of the soil organic carbon (SOC) sink, such as no-till, the use of cover crops, leaving residues on fields, improving the variety of legume species in grasslands and reducing grazing intensity. However, uncertainties remain both in estimating and measuring the impact of the application of certain practices, as these vary with the soil, climate and historic land use. IPCC (Intergovernmental Panel on Climate Change) guidelines are commonly used to estimate SOC and SOC sequestration potentials at different tiers. Here, the IPCC’s tier 1 methodology was applied to estimate (1) the sequestration potential of nine mitigation practices and (2) the emission or sequestration potential of four current land-change trends for n = 7092 unique agricultural sites in mainland Portugal. The conversion of irrigated crops to improved grasslands resulted in the highest average unit sequestration (1.05 tC ha−1 yr−1), while cropland conversion to poor degraded pasture (abandonment) resulted in the highest unit SOC loss (−0.08 tC ha−1 yr−1). The abandonment of cropland results in a national SOC loss of up to 0.09 MtC yr−1, while the improvement of poor degraded pastures has the highest national sequestration potential, equal to 0.6 MtC yr−1 (2.2 MtCO2eq yr−1), about 4% of Portugal’s emissions in 2021, if applied in all managed areas. The results enable a comparison between different practices and land uses; however, to enhance accuracy, a higher tier methodology tailored to the Portuguese context should be developed.

Getting the best of carbon bang for mangrove restoration buck

Mangrove loss has reduced its carbon (C) sink function and ecosystem services. To effectively allocate climate finance for mangrove restoration, a thorough assessment of restoration potential is necessary. Here we show a net loss of ecosystem service value (ESV) of 29.2 billion USD ($) due to land changes in mangroves from 1996 to 2019. The estimated mangrove ESV in 2019 amounts to $894 billion yr−1, mainly provided by regulating and provisioning services (57.4% and 19.7%). Over the next two decades, we project that the restoration of mangroves would necessitate an investment of $40.0–52.1 billion, yielding net gains in ESV of $231–725 billion. The global benefit-cost ratio (BCR) of mangrove restoration ranges from 6.35 to 15.0, demonstrating that such projects are highly cost-effective. Furthermore, an estimated of 19.4 Tg C can be sequestrated in mangrove soils based on a 20-year mangrove restoration program, which can generate $68.6–$236 million via blue C trading. Our findings highlight the significant opportunities for blue C restoration projects to mitigate climate change and support livelihoods.

Dynamic land-plant carbon sources in marine sediments inferred from ancient DNA

Terrigenous organic matter in marine sediments is considered a significant long-term carbon sink, yet our knowledge regarding its source taxa is severely limited. Here, we leverage land-plant ancient DNA from six globally distributed marine sediment cores covering the Last Glacial–Holocene transition as a proxy for the share, burial rate, preservation, and composition of terrigenous organic matter. We show that the spatial and temporal plant composition as revealed by sedimentary ancient DNA records reflects mainly the vegetation dynamics of nearby continents as revealed by comparison with pollen from land archives. However, we also find indications of a global north-to-south translocation of sedimentary ancient DNA. We also find that plant sedimentary ancient DNA has a higher burial rate in samples from the Late Glacial, which is characterized by high runoff and mineral load. This study provides an approach to understanding the global linkages between the terrestrial and marine carbon cycle, highlighting the need for further research to quantify the processes of DNA preservation and dispersal in marine sediments.

Modelling the social cost of carbon for Malaysia

The interest in the economics of climate change and the need to quantify a more accurate financial value of the damage caused by every additional metric tonne of greenhouse gas (GHG), known as the social cost of carbon (SCC), is growing. Governments and decision-makers have utilised SCC estimations for more than ten years in benefit-cost analysis, using insights from climate science, economics, demography, and other fields. Malaysia has committed to reduce 45% of its GHG emission intensity by Gross Domestic Product (GDP) by 2030 compared to the 2005 level and achieve net-zero as early as the year 2050. However, current estimations of SCC are high and may negatively impact the Malaysian economy and no longer align with the latest research. To achieve its objective of net-zero emissions, the government of Malaysia must capitalise on the country's potential as a carbon sink by increasing conservation efforts in protected areas and arresting deforestation. It will establish an ideal trajectory for the SCC that aligns with its environmental obligations while supporting sustainability in the face of climate change challenges. A price on GHG emissions can help mitigate and adapt to climate change. This study aims to determine the SCC in Malaysia, fill the gap in the downscaled Integrated Assessment Models (IAMs) and develop a new model called the Integrated Climate Model for Malaysia (ICLIM-2024R). The Nordhaus IAM model was downscaled using Malaysian data, including emissions from deforestation and an additional function for carbon sinks. With current policies, the SCC in the business-as-usual scenario (BAU) will be 64 USD/tCO2e in 2025 and 212 USD/tCO2e by 2050. The study recommended pathway is to increase the Totally Protected Area (TPA) of forests, which will yield a lower SCC of 23 USD/tCO2e in 2025 and 152 USD/tCO2e by 2050 compared to BAU, meeting commitments to the Convention of Biological Diversity (CBD) as well as the Paris Agreement. The Malaysian government should urgently leverage its carbon sink potential to set Malaysia's optimal SCC, achieve its net-zero goal, and grow the climate-friendly economy by marketing lower carbon-intensity products.Graphical

Carbon sinks associated with biological carbon pump in karst surface waters: Progress, challenges, and prospects.

The biological carbon pump (BCP) associated with aquatic photosynthesis in karst surface waters converts dissolved inorganic carbon (DIC) into organic carbon. In the context of global climate change, BCP could be an important carbon sink mechanism, ultimately regulating atmospheric carbon dioxide (CO2) and mitigating climate change. Because of the high DIC and pH, and low dissolved CO2 [CO2 (aq)], the hydrochemical characteristics of karst surface water bodies cause C limitation in BCP efficiency. The effect of CO2 fertilization on water bodies can promote autochthonous production, thereby creating carbon sinks in such water bodies. The significant sink-enhancement potential of BCP in karst surface water bodies has attracted widespread attention. The stability of the autochthonous organic carbon (AOC) produced by BCP in karst aquatic ecosystems is key to the formation of long-term carbon sinks by carbonate weathering. In this review, we summarize recent progress in the carbonate weathering of carbon sinks in karst surface waters with coupled BCPs. Furthermore, we elucidated the possibility of using CO2 (aq) fertilization to achieve carbon sinks and its mechanism of action. On this basis, we propose three processes and mechanisms that could affect AOC stability and outline the challenge of accurately estimating carbonate weathering carbon sinks associated with BCP in karst surface waters. Our comprehensive analyses facilitated the identification of the role of karst surface aquatic ecosystems in the global carbon cycle by providing a reference and scientific basis.

Assessment of CO2 fluxes in the hinterland of the Gurbantunggut Desert and its response to climate change.

Desert ecosystems, as an important part of terrestrial ecosystems, are considered potential hidden carbon sinks in the global carbon cycle. The Gurbantunggut Desert, as China's largest fixed/semi-fixed desert, has received little research on its role in the global carbon cycle and future trends. This study utilizes continuous observational data from the Gurbantunggut Desert from 2018 to 2022 and integrates CMIP6 global climate model scenario data to study the evolution of carbon balance in the desert ecosystem, carbon source/sink functions, and future trends. The result showed that: 1) The CO2 flux in the Gurbantunggut Desert shows Carbon sink during the day and carbon source at night, with an annual cumulative carbon sink duration of over 240 days.2)From 2018 to 2020, the desert ecosystem of the Gurbantunggut Desert functioned as a net CO2 sink.3) Desert ecosystems were subjected to concurrent influences from multiple environmental factors across varying time scales, with photosynthetically active radiation, air temperature, and soil temperature identified as the most influential factors affecting CO2 flux in the Gurbantunggut Desert. 4) The climate of the Gurbantunggut Desert is projected to exhibit a trend of warming and increased humidity in the future. Against the backdrop of future warming and humidification, the Gurbantunggut desert ecosystem is anticipated to exhibit a pronounced carbon sink characteristic.

Insight into the impact of biogeochemical reactions of groundwater nitrogen on chemical weathering and carbon cycling

Groundwater nitrate pollution is a global environmental issue impacted by complex biogeochemical processes. The biogeochemical behavior of nitrogen in groundwater can significantly influence the hydrogeochemical processes and the carbon cycle. This study, taking the Jinghuiqu Irrigation District in China as an example, analyzed the biogeochemical processes of nitrate in groundwater and discussed their effects on groundwater chemical weathering and the carbon cycle by using groundwater chemistry, multiple isotopes (δ15N-NO3−, δ18O-NO3−, and δ18O-H2O), and microbial techniques. Results indicated that nitrification predominantly drives the biogeochemical processes of nitrogen in groundwater in this area. Anthropogenic nitrogen inputs enhanced the geochemical weathering of sediments in shallow groundwater systems through nitrification. As nitrification increased nitrate concentrations, the net CO2 sink gradually shifted to a net CO2 source. Under the influence of nitrification, the CO2 consumption decreases, leading to a reduction in the carbon sink. The average CO2 consumption rates of carbonate weathering and silicate weathering were 1.10 × 105 mol/km2/yr and 0.60 × 105 mol/km2/yr, respectively. Additionally, energy released during nitrification may promote microbial metabolic processes related to the carbon cycle. Correlation analysis of the nitrogen cycle and carbon cycle pathways revealed a significant association (p ≤ 0.05) between nitrification and both the reductive tricarboxylic acid cycle and the Calvin-Benson-Bassham cycle. Therefore, nitrification significantly influences the nitrogen cycle and may indirectly affect the carbon cycle. This research enhances our understanding of how the biogeochemical processes of groundwater nitrogen impact hydrochemistry and the carbon cycle, providing scientific insights for addressing climate change and ecosystem management.

Multi-scale urban ecosystem service changes and their impact mechanisms on human well-being.

With increasing urbanization pressures, there is an urgent need to improve the urban residents' well-being and achieve the sustainable development goals (SDGs). Ecosystem services (ESs) are vital for human well-being (HW) and survival, providing essential benefits like clean water while supporting the SDGs. However, understanding the impact mechanism of urban ESs on the HW under the framework of the SGDs in a changing world remains challenging. This study simulated five key ESs: net primary productivity (NPP), water yield (WY), soil conservation (SC), soil fixation (SF), and ecosystem carbon sink (ECSI) using ecological models at the pixel, urban green space and county scales, and calculated supply services at the county scale. Then we established an evaluation index system of the HW to reveal the impact mechanism of the ESs on the HW. The study found that in Beijing, the ESs improved by 29.14%-267.42%, while SF decreased by 55.84% during 2000-2020, and the urban green space became a carbon sink since 2010. At the pixel and urban green space scales, vegetation significantly drove the ES dynamics, with the relative importances exceeding 90% in supporting NPP and exceeding 55% in restraining WY. The urban landscape patterns dominated the ES dynamics at the county scale. The impervious landscape percentage inhibited NPP, ECSI and SC with the relative importances of 66.47%, 39.94% and 19.52%. The HW in Beijing increased from 2005 to 2020, with a notable difference between central urban and non-central urban counties. The supporting services supply had significantly negative direct and indirect impacts on the HW. The indirect impact of the urban ecosystem supporting service supply on the HW was through restraining provisioning service supply and supporting regulating service supply. The provisioning service supply had a significantly positive direct influence on the HW. This study can provide valuable references for sustainable urban management.

Towards Equitable Carbon Responsibility: Integrating Trade-Related Emissions and Carbon Sinks in Urban Decarbonization

Towards Equitable Carbon Responsibility: Integrating Trade-Related Emissions and Carbon Sinks in Urban Decarbonization

Rainstorms drive the carbon dioxide emissions during the algae-growing season in a large eutrophic lake.

Lakes are sources of atmospheric carbon dioxide (CO2), contributing to global climate change. Temporal variations in lake CO2 emissions are pronounced, with algal growth and precipitation identified as important drivers. Eutrophic lakes often act as atmospheric CO2 sinks during the growing season. However, these lakes can also emit CO2 during the same period, a paradox that we hypothesize is driven by precipitation. This study tests this hypothesis and examines how rainstorms influence lake CO2 emissions. To investigate, seven buoys were deployed in eutrophic Lake Taihu and a major inflow river to monitor water quality at 4-h intervals throughout 2021. CO2 flux (FCO2) was calculated using integrated methods, including gas diffusion models, the CO2calc program, and machine learning algorithms, based on water quality and meteorological data. Results revealed that only rainstorms (daily rainfall >50mm) significantly increased FCO2. Although only three rainstorm events occurred, they accounted for 12.15% of the annual CO2 emissions. During the growing season, the lake was a net CO2 source, but without rainstorm-induced emissions, it would have functioned as a CO2 sink, highlighting the crucial role of rainstorms in shifting lake dynamics. Piecewise structural equation modeling indicated that both abiotic factors (e.g., gas transfer velocity) and biotic factors (e.g., aquatic metabolism) influenced by rainstorms contributed to the elevated FCO2. These findings suggest that future reductions in lake FCO2 due to eutrophication, combined with more frequent rainstorms under climate change, could amplify the impact of extreme precipitation on CO2 emissions.

Long-term warming offsets the beneficial effect of elevated CO2 on mineral associated organic carbon in Mollisols.

The stability of soil organic carbon (SOC) is fundamentally important to the carbon-climate feedback because soils act as a major carbon source or sink under climate change. The uncertainty of SOC stability in farming soils in response to climate change necessitates mechanistic studies on microbial attributes to the change of SOC. Here, we used open-top chambers to simulate elevated CO2 (eCO2) and warming for 12years in a soybean-grown Mollisol. We did not find the change of SOC stock under eCO2 or warming. Although eCO2 resulted in the accumulation of mineral-associated organic carbon, this effect diminished under warming. The amplicon sequencing of 16S gene indicated a significant change in microbial community composition under warming or eCO2. The metagenomic sequencing demonstrated that warming increased the abundances of microbial genes related to decomposition of labile carbon such as hemicellulose and pectin. The warming-induced stimulation of microbial catabolic metabolisms on organic carbon decomposition might have accelerated SOC turnover, which may offset the increased mineral-associated organic carbon of the Mollisol under eCO2. Long-term eCO2 and warming might not significantly alter the SOC stock or stability but accelerate carbon cycling in farming Mollisols.

Synergistic effects of carbon and heat under disturbance of human activities: Evidence from a resource-based city of China.

For resource-based cities, the rapid development of industrialization and urbanization has led to significant carbon emissions (CEs), accelerated the rise of urban land surface temperatures (LSTs) and hindered sustainable urban development. This study constructed a model to measure the carbon-heat relationship to clarify the complex relationship between LSTs and CEs in resource-based cities. The results show that:1) High-temperature areas are primarily concentrated around the urban center and large industrial zones, with average LSTs reaching a peak of 35.7°C in 2015, indicating severe temperature polarization; 2) CEs exhibited an overall upward trend with a diffusion effect, particularly pronounced in the urban center and industrial zones. Areas with extremely significant, strong significant, and generally significant growth in CEs accounted for 4.64%, 3.81%, and 81.35%, respectively, showing a concentrated increase in the urban center; 3) A positive correlation between CEs and LSTs of the city was identified, and the distribution of urban heat island and the high value area of CEs are concentrated and similar; 4) The synergistic effects between LSTs and CEs varied between urban center, suburban and peripheral areas, due to human activities. Areas with a high positive correlation between CEs and LSTs are concentrated in urban centers and peripheral areas, while for urban suburbs, the correlation is weak or even absent. To mitigate the negative effects of carbon-heat accumulation, urban centers should avoid high population concentrations, and the carbon sink potential of green spaces near industrial zones and peripheral areas should be fully utilized. These insights provide actionable strategies for sustainability of resource-based cities, particularly in the governance of urban thermal environments and the mitigation of CEs.

Advancing Hydrothermal Carbonization: Assessing Hydrochar's Role and Challenges in Carbon Sequestration.

The increasing urgency to reduce atmospheric CO2 emissions has driven research into sustainable carbon sequestration technologies, with hydrochar (HC) emerging as a promising material. HC is derived from hydrothermal carbonization (HTC), a thermochemical process that converts biomass into a carbon-rich solid at moderate temperatures and self-generated pressure in an aqueous environment. Due to its unique reaction pathways, HC differs significantly from biochar (BC) derived from pyrolysis in terms of application, performance, and structural characteristics. Despite HC's potential for long-term carbon storage, critical gaps remain in understanding its sequestration mechanisms, influencing factors, and optimization strategies-hindering its effective application. This review critically evaluates HC's carbon sequestration capacity, focusing on overlooked complexities that influence its performance. Key parameters, including feedstock composition, reaction temperature, pH, and residence time, are systematically examined to elucidate their impact on HC's structural integrity and carbon stability. Special attention is given to the role of lignin in enhancing stability and thermal resilience, as well as the concept of carbon-ash recalcitrance, where mineral embedding enhances carbon stability. To assess HC's long-term sequestration effectiveness, this study analyzes key indicators such as thermal stability, chemical resilience, aromaticity, and dissolved organic carbon (DOC) leaching.Besides, this review explores innovative strategies for improving HC's sequestration performance, including HTC liquid recycling, chemical modification, and salinity control. By integrating expert-driven insights and identifying research gaps, this synthesis advances theoretical understanding while outlining future directions for optimizing HC as a sustainable carbon sink. Ultimately, this work establishes HC as a critical material in global carbon management efforts and climate change mitigation.

Large burial flux of modern organic carbon in the St. Lawrence estuarine system indicates a substantial atmospheric carbon sink

Large burial flux of modern organic carbon in the St. Lawrence estuarine system indicates a substantial atmospheric carbon sink

Interactions Between Climate Mean and Variability Drive Future Agroecosystem Vulnerability.

Agriculture is crucial for global food supply and dominates the Earth's land surface. It is unknown, however, how slow but relentless changes in climate mean state, versus random extreme conditions arising from changing variability, will affect agroecosystems' carbon fluxes, energy fluxes, and crop production. We used an advanced weather generator to partition changes in mean climate state versus variability for both temperature and precipitation, producing forcing data to drive factorial-design simulations of US Midwest agricultural regions in the Energy Exascale Earth System Model. We found that an increase in temperature mean lowers stored carbon, plant productivity, and crop yield, and tends to convert agroecosystems from a carbon sink to a source, as expected; it also can cause local to regional cooling in the earth system model through its effects on the Bowen Ratio. The combined effect of mean and variability changes on carbon fluxes and pools was nonlinear, that is, greater than each individual case. For instance, gross primary production reduces by 9%, 1%, and 13% due to change in mean temperature, change in temperature variability, and change in both temperature mean and variability, respectively. Overall, the scenario with change in both temperature and precipitation means leads to the largest reduction in carbon fluxes (-16% gross primary production), carbon pools (-35% vegetation carbon), and crop yields (-33% and -22% median reduction in yield for corn and soybean, respectively). By unambiguously parsing the effects of changing climate mean versus variability and quantifying their nonadditive impacts, this study lays a foundation for more robust understanding and prediction of agroecosystems' vulnerability to 21st-century climate change.