Search

In the global context, countries must reduce carbon dioxide emissions to "net zero" by 2050 to limit global warming to 1.5 °C above pre-industrial levels. China's Nationally Determined Contributions (NDCs) are to peak carbon dioxide emissions by 2030 and achieve the carbon neutrality target by 2060. To monitor the achievements of the NDCs, establishing an annual-based accounting mechanism is necessary to record the carbon stocks in China, especially for Blue Carbon. The paper aims to present China's first national-scale systematic Blue Carbon accounting for mangroves, salt marshes, and seagrasses, covering the accounting subjects of physical and monetary assets, as well as relevant indicators for investors. It focuses on the design of the accounting method and system, the selection of data categories applied to this system, and the application of China's Blue Carbon accounting based on this accounting system. Taking Blue Carbon accounting as a starting point, this paper analyses the restoration prospects of these ecosystems and their application potential for NDCs in China compared with the terrestrial ecosystems. The results indicate that mangroves are the most cost-effective type of ecosystem, even compared to terrestrial forests. Thus, the paper provides policymakers with a new perspective on the decision-making of carbon sequestration relevant decisions, aiming to promote the monitoring, restoration, and expansion of China's coastal blue carbon ecosystem through the establishment of a sound Blue Carbon accounting system, and to help achieve the carbon neutrality goal in China's NDCs through regular and systematic monitoring of its national Blue Carbon inventories. • China's coastal blue carbon ecosystems are carbon sources rather than carbon sinks. • Mangroves are the most cost-effective coastal blue carbon ecosystem compared to salt marshes and seagrass beds. • The Blue Carbon of mangroves is more cost-effective than the Green Carbon of terrestrial forests when meeting China's Nationally Determined Contributions target of increasing forest stocks. • Establishing guidelines for Blue Carbon data requirements will lay a scientific foundation for formulating strategies and policies to cope with global climate change. [ABSTRACT FROM AUTHOR]

The carbon trading policy seeks to control carbon emissions by putting a price on carbon emissions and establishing a corresponding carbon market for trading. It is a significant move by China to address climate issues and achieve its Carbon Neutrality target. Therefore, assessing the policy effects of carbon trading is fundamental to its implementation nationwide. Based on the panel data of 30 provinces and cities in China from 2008 to 2018, this paper uses the Synthetic Control Method and Differences-in-Differences method to assess the effects of carbon trading policy on achieving Carbon Neutrality. By measuring the net carbon emissions, this research explores the level of Carbon Neutrality in each region. Based on the Five-sphere Integrated Plan (which covers the economy, politics, culture, social and ecological civilization), this research further verifies the impact paths of carbon trading policy on Carbon Neutrality. The results show that: First, carbon trading policy has a significant and sustainable effect on Carbon Neutrality. Second, from the perspective of the Five-sphere Integrated Plan, the carbon trading policy can help to reduce carbon sources and increase carbon sinks by adjusting the industrial structure, coordinating low-carbon policies, promoting cultural dissemination, increasing green space construction, and reducing energy intensity to achieve Carbon Neutrality. Third, cultural construction plays the most significant role in mediating carbon trading and Carbon Neutrality, followed by political construction. • This paper examines the effectiveness of carbon trading policy for Carbon Neutrality. • We use the Synthetic Control Method and Difference-in-Differences method. • The impact paths of carbon trading policy are examined from the Five-sphere Integrated Plan perspective. • Carbon Neutrality should be incorporated into the Five-sphere Integrated Plan. • A cross-perspective study of the Five-sphere Integrated Plan, carbon trading with Chinese characteristics has been formed. [ABSTRACT FROM AUTHOR]

Process-related carbon emissions, which cannot be completely eliminated by the improvement of processes and energy structure, are recognized as an enormous challenge for in-depth decarbonization. To accelerate the achievement of carbon neutrality, the concept of 'artificial carbon cycle' is proposed based on the integrated system of process-related carbon emissions from high-emitting industries and CCU technology as a potential pathway towards a sustainable future. This paper conducts a systematic review on the integrated system with the case of China, which is the largest carbon-emitting and manufacturing country, to provide a clearer and more meaningful analysis. Multi-index assessment was used to organize the literature and draw the useful conclusion. Based on literature review, the high-quality carbon sources, reasonable carbon capture approaches and promising chemical products were identified and analyzed. Then the potential and practicability of the integrated system was further summarized and analyzed. Finally, key factors of future development including technology improvement, green hydrogen, clean energy and industrial cooperation were stressed to provide a theoretical reference for future researchers and policy makers. • Demonstration on the rationality and importance of applying CCU technology on process-based carbon emissions. • Multi-index assessment on adoptable carbon sources, possible pathways of carbon capture and carbon conversion. • Analysis on the potential and practicability of the integrated system to accelerate carbon neutrality. [ABSTRACT FROM AUTHOR]

Coastal embayments play a vital role in the global carbon cycle either as sources of organic matter to open sea or as carbon sinks due to the accumulation of organic matter in sediments. This paper describes a study of Luoyuan Bay, a typical semi-enclosed embayment with a total area of approximately 227 km 2 in a strong tidal environment. The analysed results indicate that the particulate organic carbon (POC) concentration in suspended particulate matter (SPM) varies from 0.57 mg/L to 1.33 mg/L at the bottom layer (0.5 MAB, meters above bed) and from 0.54 mg/L to 1.25 mg/L at the surface layer (0.5 MBS, meters below surface). The δ 13 C‰ ranges from −25.52‰ to −23.54‰ and exhibits different variations at the surface and bottom layers in spring and neap tides. The POC content in deposited particulate matter (DPM) varies from 0.62% to 2.95%, increasing from spring to neap tide, and the δ 13 C and C/N molar ratio are −25.29‰ ∼ −21.41‰ and 4.18–8.53, respectively. The settling fluxes of POC obtained by sediment trap decrease from 2.25 g/m 2 ·tide during the spring tide to 0.55 g/m 2 ·tide during the neap tide with a mean value of 1.41 g/m 2 ·tide during the observation, whereas the settling flux of SPM decreases from 456.76 g/m 2 ·tide during the spring tide to 37.12 g/m 2 ·tide during the neap tide. Combining the δ 13 C and C/N molar ratio, three end-members are recognized, i.e., freshwater algae and phytoplankton, marine algae and phytoplankton, and kelp-derived detritus. The mean contribution to POC from these three sources is 57.2%, 31.8% and 11.0% in SPM, and 39.9%, 35.0% and 25.1% in DPM, respectively. The POC from freshwater algae, phytoplankton and kelp-derived detritus is controlled by sediment dynamic processes. [ABSTRACT FROM AUTHOR]

The Chinese government has made great efforts in air pollutant reduction and carried out strict regulation policies. Since numerous air pollutants and CO 2 tend to have the same root, source, and process, recent studies argue that environmental regulation may also contribute to reducing carbon emissions. To investigate how various types of environmental regulations affect carbon emissions reduction, this paper constructs the spatial Durbin model and panel threshold model based on provincial panel data in China during 2003–2019. The main findings are as follows: First, China's net carbon emissions show a decreasing trend from east to west, displaying significant spatial agglomeration characteristics. Then, formal and informal environmental regulations have inverted U-shaped impacts on net carbon emissions. The "green paradox" and "reverse emission reduction" effects come into play at different stages. Finally, the threshold model reveals that with the improvement of regional technological innovation levels, the carbon-reducing effect of environmental regulation will increasingly come to the fore. These research findings are conducive to providing theoretical guidance for government to formulate and implement environmental regulation policies rationally. • Carbon sink effect is considered in the carbon emissions assessment framework. • The spatial spillover and threshold effects of environmental regulation is studied. • Environmental regulation has an inverted U-shaped impact on net carbon emissions. • Technological innovation level exerts a threshold effect between them. [ABSTRACT FROM AUTHOR]

Frequency and severity of droughts were projected to increase in many regions. However, their effects of temporal dynamics on the terrestrial carbon cycle remain uncertain, and hence deserve further investigation. In this paper, the droughts that occurred in China during 2001–2010 were identified by using the standardized precipitation index (SPI). Standardized anomaly index (SAI), which has been widely employed in reflecting precipitation, was extended to evaluate the anomalies of net primary productivity (NPP). In addition, influences of the droughts on vegetation were explored by examining the temporal dynamics of SAI–NPP along with area-weighted drought intensity at different time scales (1, 3, 6, 9 and 12 months). Year-to-year variability of NPP with several factors, including droughts, NDVI, radiation and temperature, was analyzed as well. Consequently, the droughts in the years 2001, 2006 and 2009 were well reconstructed. This indicates that SPI could be applied to the monitoring of the droughts in China during the past decade (2001–2010) effectively. Moreover, strongest correlations between droughts and NPP anomalies were found during or after the drought intensities reached their peak values. In addition, some droughts substantially reduced the countrywide NPP, whereas the others did not. These phenomena can be explained by the regional diversities of drought intensity, drought duration, areal extents of the droughts, as well as the cumulative and lag responses of vegetation to the precipitation deficits. Besides the drought conditions, normalized difference vegetation index (NDVI), radiation and temperature also contribute to the interannual variability of NPP. [Copyright &y& Elsevier]

Abstract: Preservation of organic matter in estuarine and coastal areas is an important process in the global carbon cycle. This paper presents bulk δ13C and C/N of organic matter from source to sink in the Pearl River catchment, delta and estuary, and discusses the applicability of δ13C and C/N as indicators for sources of organic matter in deltaic and estuarine sediments. In addition to the 91 surface sediment samples, other materials collected in this study cover the main sources of organic material to estuarine sediment. These are: terrestrial organic matter (TOM), including plants and soil samples from the catchment; estuarine and marine suspended particulate organic carbon (POC) from both summer and winter. Results show that the average δ13C of estuarine surface sediment increases from −25.0 ± 1.3‰ in the freshwater environment to −21.0 ± 0.2‰ in the marine environment, with C/N decreasing from 15.2 ± 3.3 to 6.8 ± 0.2. In the source areas, C3 plants have lower δ13C than C4 plants (−29.0 ± 1.8‰ and −13.1 ± 0.5‰ respectively). δ13C increases from −28.3 ± 0.8‰ in the forest soil to around −24.1‰ in both riverbank soil and mangrove soil due to increasing proportion of C4 grasses. The δ13CPOC increases from −27.6 ± 0.8‰ in the freshwater areas to −22.4 ± 0.5‰ in the marine-brackish-water areas in winter, and ranges between −24.0‰ in freshwater areas and −25.4‰ in brackish-water areas in summer. Comparison of the δ13C and C/N between the sources and sink indicates a weakening TOM and freshwater POC input in the surface sedimentary organic matter seawards, and a strengthening contribution from the marine organic matter. Thus we suggest that bulk organic δ13C and C/N analysis can be used to indicate sources of sedimentary organic matter in estuarine environments. Organic carbon in surface sediments derived from anthropogenic sources such as human waste and organic pollutants from industrial and agricultural activities accounts for less than 10% of the total organic carbon (TOC). Although results also indicate elevated δ13C of sedimentary organic matter due to some agricultural products such as sugarcane, C3 plants are still the dominant vegetation type in this area, and the bulk organic δ13C and C/N is still an effective indicator for sources of organic matter in estuarine sediments. [Copyright &y& Elsevier]

Soil organic carbon (SOC) is of great importance in the global carbon cycle. Distribution patterns of SOC in various regions of China constitute a nation-wide baseline for studies on soil carbon changes. This paper presents an integrated and multi-level study on SOC stock patterns of China, and presents baseline SOC stock estimates by great administrative regions, river watersheds, soil type regions and ecosystem. The assignment is done by means of a recently completed 1: 1,000,000 scale soil database of China, which is the most detailed and reliable one in China at the present time. SOC densities of 7292 soil profiles collected across China in the middle of the 1980s were calculated and then linked to corresponding polygons in a digital soil map, resulting in a SOC Density Map of China on a 1: 1,000,000 scale, and a 1km×1km grid map. Corresponding maps of administrative regions, river watersheds, soil types (ST), and ecosystems in China were also prepared with an identical resolution and coordinate control points, allowing GIS analyses. Results show that soils in China cover an area of 9.281×106 km2 in total, with a total SOC stock of 89.14Pg (1Pg=1015 g) and a mean SOC density of 96.0tC/ha. Confidence limits of the SOC stock and density in China are estimated as [89.23Pg, 89.08Pg] and [96.143tC/ha, 95.981tC/ha] at 95% probability, respectively. The largest total SOC stock (23.60Pg) is found in South-west China while the highest mean SOC density (181.9tC/ha) is found in north-east China. The total SOC stock and the mean SOC density in the Yangtze river watershed are 21.05Pg and 120.0tC/ha, respectively, while the corresponding figures in theYellow river watershed are 8.46Pg and 104.3tC/ha, respectively. The highest total SOC stocks are found in Inceptisols (34.39Pg) with SOC density of 102.8tC/ha. The lowest and highest mean SOC densities are found on Entisols (28.1tC/ha), and on Histosols (994.728.1tC/ha), repectively. Finally, the total SOC stock in shrub and forest ecosystem classes are 25.55 and 21.50Pg, respectively; the highest mean SOC density (209.9tC/ha) was recorded in the wetland ecosystem class and the lowest (29.0tC/ha) in the desert ecosystem class. Among five forest ecosystem types, Evergreen conifer forest stores the highest SOC stock (6.81Pg), and Deciduous conifer forest shows the highest SOC density (225.9tC/ha). Figures of SOC stocks stratified by Administrative regions, river watersheds, soil types and ecosystem types presented in the study may constitute national-wide baseline for studies of SOC stock changes in various regions in the future. [Copyright &y& Elsevier]

Large scale process-based modeling is a useful approach to estimate distributions of global net primary productivity (NPP). In this paper, in order to validate an existing NPP model with observed data at site level, field experiments were conducted at three sites in northern China. One site is located in Qilian Mountain in Gansu Province, and the other two sites are in Changbaishan Natural Reserve and Dunhua County in Jilin Province. Detailed field experiments are discussed and field data are used to validate the simulated NPP. Remotely sensed images including Landsat Enhanced Thematic Mapper plus (ETM+, 30m spatial resolution in visible and near infrared bands) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER, 15m spatial resolution in visible and near infrared bands) are used to derive maps of land cover, leaf area index, and biomass. Based on these maps, field measured data, soil texture and daily meteorological data, NPP of these sites are simulated for year 2001 with the boreal ecosystem productivity simulator (BEPS). The NPP in these sites ranges from 80 to 800gCm−2 a−1. The observed NPP agrees well with the modeled NPP. This study suggests that BEPS can be used to estimate NPP in northern China if remotely sensed images of high spatial resolution are available. [Copyright &y& Elsevier]

This paper reports the annual carbon (C) balance of China''s forests during 1901–2001 estimated using the Integrated Terrestrial Ecosystem C-budget model (InTEC). Annual carbon source and sink distributions are simulated for the same period using various spatial datasets including land cover and leaf area index (LAI) obtained from remote sensing, soil texture, climate, forest age, and nitrogen deposition. During 1901–1949, China''s forests were a source of 21.0±7.8TgCyr−1 due to disturbances (human activities). Its size increased to 122.3±25.3TgCyr−1 during 1950–1987 due to intensified human activities in the late 1950s, early 1960s, 1970s and early 1980s. The forests became large sinks of 176.7±44.8TgCyr−1 during 1988–2001, owing to large-scale plantation and forest regrowth in previously disturbed areas as well as growth stimulation by nondisturbance factors such as climatic warming, atmospheric CO2 fertilization, and N deposition. From 1901 to 2001, China''s forests were a small carbon source of 3.32PgC, about 32.9±22.3TgCyr−1. The overall C balance in biomass from InTEC generally agrees with previous results derived from forest inventories of China''s forests. InTEC results also include C stock variation in soils and are therefore more comprehensive than previous results. The uncertainty in InTEC results is still large, but it can be reduced if a detailed forest age map becomes available. [Copyright &y& Elsevier]

Coastal wetlands play an increasingly important role in regulating greenhouse gas (GHG) fluxes and thus affecting climate change. However, the overall magnitude, trend, and environmental drivers of GHG fluxes in these wetlands of China remain uncertain. Herein, we synthesized data from 70 publications involving 187 field observations to identify patterns and drivers of GHG fluxes across coastal wetlands in China. Average methane (CH 4), nitrous oxide (N 2 O) fluxes, and carbon dioxide (CO 2) emissions (ecosystem respiration) across coastal wetlands were estimated as 2.20±0.31 mg·m-2·h-1, 16.44±2.96 μg·m-2·h-1, and 388.76±42.28 mg·m-2·h-1, respectively. GHG emissions varied with tidal inundation, where CH 4 and CO 2 emissions during tidal inundation were lower than during ebbing. CH 4 and CO 2 emissions from wetlands decreased linearly with increasing latitude, while N 2 O did not. CH 4 fluxes were positively related to air temperature and aboveground biomass, and CO 2 emissions were positively related to soil organic carbon. N 2 O fluxes were lower with increasing soil pH, and CH 4 and CO 2 emissions were greater with increasing soil moisture. Based on the results of sustained-flux global warming potential and sustained-flux global cooling potential models, our paper indicate that the fluxes of CH 4 and N 2 O in coastal wetlands have a positive feedback to global warming, which is mainly driven by the CH 4 emission. Our synthesis improved understanding of the roles of coastal wetlands in the ecosystem C cycle under global change. We suggest that long-term field observations of GHG fluxes across a wider range of spatiotemporal scales are urgently required to improve the prediction accuracy in GHG fluxes and the assessment of net GHG balance and its contribution to the GWP of coastal wetlands. [ABSTRACT FROM AUTHOR]

Terrestrial ecosystems have received considerable attention as a significant sink for organic carbon at regional to global scales. Previous studies were focused on assessment and quantification of carbon sinks for one ecotype, and few have worked on the interconnection of terrestrial sinks. In this paper, we synthesized the data from China's second national soil survey and direct measurements from 54 lakes. Meanwhile, we investigated the controlling factors of carbon accumulation dynamics in soils and lakes. Results showed varied spatial distribution of soil and lake organic carbon in different regions, and three storage modes were found. The storage mode of watershed collection was observed in the region of the Qinghai-Tibetan Plateau, while the northeast China and Yunnan-Guizhou Plateau revealed another storage mode of autochthonous deposition, and the mode of human activities affection was represented by the East Plain and Mongolia-Xinjiang Plateau. The spatial difference throughout China was regulated by various climate patterns, geological conditions and anthropogenic interference. Our results provide insights into carbon storage modes in various regions, and also inform strategies for enhancing global carbon sequestration and future mitigation policies towards global climate change. • Climate, topography and human activity regulate regional soil and lake carbon storage. • Three carbon storage modes based on relationship between soil and lake carbon. • Suggestions to enhance carbon sequestration through soil and lake management. [ABSTRACT FROM AUTHOR]