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Petroleum hydrocarbons (PHCs) can be biodegraded into CO 2 , and PHC-contaminated aquifers are always deemed as carbon sources. Fortunately, some carbon fixation microorganisms have been found in PHC-contaminated sites. However, most of the studies are related to volatile short-chain PHC, and few studies focus on long-chain PHC-contaminated sites. To reveal the carbon fixation microorganisms in these sites, in the study, a long-chain PHC polluted site in North China was selected. Through hydrochemical and metagenomics analysis, the structure and capacity of carbon fixing microorganisms in the site were revealed. Results showed that there were many kinds of carbon fixed microorganisms that were identified such as Flavobacterium, Pseudomonas. HP/4HB, rTCA, and DC/4HB cycles were dominated carbon fixation pathways. The long-chain PHC were weakly correlated with carbon fixation microorganisms, but it may stimulate the growth of some carbon fixation microorganisms, such as microorganisms involved in rTCA cycle. PRACTITIONER POINTS: The microorganisms with carbon fixation gene exist in the aquifer contaminated by long-chain petroleum hydrocarbon. Microorganisms that have the ability to degrade petroleum also have the ability to carbon fixation. Long-chain petroleum hydrocarbon may promote the growth of carbon fixation microorganisms., (© 2024 Water Environment Federation.)

Pulp and paper industry is one of the eight critical industries for controlling carbon emissions in China. As the paper productions increase, the pulp and paper industry may fail in achieving the emission reduction target due to the rapid growth of greenhouse gas emissions. The study uses life cycle assessment to evaluate the greenhouse gas emissions of China's papermaking industry chain in order to propose emission reduction targets and find ways to achieve the emission reduction targets for China's papermaking industry. Considering the net carbon absorption of plant raw materials and the extensive paper industrial chain, this study obtained that the greenhouse gas emission of major paper types under corresponding pathways ranges from 1.96 t CO 2 eq/t paper to 6.55 t CO 2 eq/t paper. Plant carbon sink can reduce greenhouse gas emissions by 14.3%–42.9% under virgin fiber-based pathways. This study found that the greenhouse gas emissions caused by terminal products of 814 papermaking enterprises counted in China were 282.23 Mt CO 2 eq in 2015, accounting for 10.23% of the total greenhouse gas emissions of manufacturing industries and construction. To achieve the emission reduction target by 2050, emissions of the pulp and paper industry in China have been investigated from the perspective of three ideal energy structures. The research findings show that the emission reduction target of Intended Nationally Determined Contribution will be achieved in 30 years if the energy structure of the pulp and paper industry is adjusted only based on the optimal 450 scenario. In terms of other energy structures, the pulp and paper industry should assume afforestation areas ranged from 5900 km2 to 223,000 km2 at least to make up for the greenhouse gas emissions beyond allowance, which accounts for 0.85%–32.16% of the existing areas of plantation forestry in China. • Statistics in this work reveal the problem of excess capacity in China's pulp and paper industry. • GHG emission of paper products in different pathways range from 1.95 to 6.52 t CO 2 eq/t paper. • Energy supply mode transition is conductive to green development of pulp and paper industry. • Pulp and paper enterprises should assume afforestation areas to achieve emission reduction targets. [ABSTRACT FROM AUTHOR]

Blue Carbon is increasingly popular worldwide, and it also belongs to circular economy field which would last a long period in academy. To further understand the development and characteristics of Blue Carbon, this study uses CiteSpace software to perform quantitative analysis on literature published on Web of Science and Chinese CNKI database with the main topic of "Blue Carbon." The results show that: (1) Since 2009, increasing attention has been paid to Blue Carbon research, among which the United States, Australia and China are the leading countries. (2) Keywords such as "Blue Carbon," "mangrove," "carbon sequestration" and "carbon neutrality" are the high-frequency keywords appearing both in China and the World in recent years. (3) Spartina alterniflora, soil organic carbon, livestock, trophic cascade, biodiversity and seagrass ecosystem clustering are hot topics related to international Blue Carbon research, while organic carbon, seagrass-conservation, methodology, sustainable development, climate change, carbon neutralization, coastal zone and carbon storage are hot topics related to Chinese Blue Carbon research. In addition, based on the research trends of Blue Carbon, this paper attempts to sort out the research framework from three levels: core characteristics, theoretical basis and research methods, respectively. Facing a series of challenges brought by climate change, Blue Carbon research should strengthen the accurate estimations of Blue Carbon sink and its market potential, and explore the reasonable market mechanism and protection mechanism, to respond to realistic demands, solve major concerns and promote new progress in Blue Carbon theory and practice. [ABSTRACT FROM AUTHOR]

The land use, land-use change and forestry (LULUCF) sector, as a source and a sink of greenhouse gas (GHG) emissions, is critical for achieving carbon neutrality. Many academic journals have published papers on land use carbon emission or sink (LUCES), but LUCES reviews are relatively rare, which poses great challenges in accurately understanding the research progress and future prospects. This work analyzes the research characteristics, hotspots and future perspectives of LUCES research by using a bibliometric analysis (such as DDA, VOSviewer, CiteSpace software) and a review based on the data (6115 scientific papers) during 1991–2023 from the Web of Science (WoS) platform. We found that (1) over the past 33 years, it first presented a steady growth, then fluctuating growth, and finally a rapid growth trend in the yearly number of publications in LUCES research. The USA (17.31%), China (14.96%), and the UK (7.37%) occupy a dominant position in this research field. (2) The related LUCES research is interdisciplinary, which mainly cover science and technology, meteorology and atmospheric sciences, geology, and environmental sciences and ecology disciplines. (3) The research hotspot analysis on LUCES shows that these articles mostly covered the follow three aspects: ecosystem services, climate change, and carbon neutrality. (4) A review of the past LUCES literature suggests that it is mainly focused on exploring the forefront issues in terms of the definition and boundaries, evaluation method and influencing factors, etc. This work suggests that further research could explore the main scientific problems on quantification of land-based carbon neutrality, quantitative analysis of the impact mechanisms, as well as interdisciplinary research and collaborative governance needed for carbon neutrality. [ABSTRACT FROM AUTHOR]

The energy saving and emissions reduction of the construction industry are crucial for China to achieve the "carbon peaking and carbon neutrality" goals. In order to promote the green development of the life cycle of the construction industry and improve the efficiency of emissions reduction. This paper examines the spatial-temporal distribution of life cycle carbon emissions in China's construction industry (LCCECI) from 2004 to 2018. It uses the SBM-Malmquist total factor productivity (TFP) index to measure technological progress and establishes the spatial econometric model based on the STIRPAT model. The study investigates the driving factors of the LCCECI at the provincial and regional levels, aiming to provide suggestions for low-carbon development in the construction industry. The research results are as follows. © The growth in the SBM-Malmquist TFP index of the construction industry distinctly curbs the LCCECI. © Total population and urbanization level are not the primary driving factors for the LCCECI. The growth of per capita GDP significantly induces the LCCECI, while concurrently exhibiting a notable inhibitory effect on the LCCECI of neighboring regions. © The improvement of the SBM-Malmquist TFP index is conducive to the reduction of the LCCECI in the three major regions. The per capita GDP has the largest positive driving effect of the LCCECI in the eastern region, and the urbanization level the urbanization rate only significantly inhibits the growth of the LCCECI in the central region. [ABSTRACT FROM AUTHOR]

Carbon emissions are critical to climate change, and land-use change is an essential source of growth in carbon emissions. Research on land-use carbon emissions has become one of the hotspots in academic research. To explore the research hotspots and development trends of land-use carbon emissions in the last 20 years, CiteSpace software was used to conduct a quantitative analysis of relevant literature. This paper was based on the China National Knowledge Infrastructure (CNKI) and Web of Science (WoS) database literature on land-use carbon emissions from 2001 to 2020. The scientific research cooperation network CiteSpace software, with keyword co-occurrence, clustering, and burst word detection, was used to systematically analyze the main research strengths, hotspots and frontiers and clarify the research progress. The research results are as follows: (1) the amount of literature and the depth of research on land-use carbon emissions have increased yearly. However, there is little cooperation between research institutions and scholars, and there is still a lack of large-scale and stable research teams. (2) At the research hotspot level, the English literature focuses on building models and theoretical frameworks to study the internal mechanisms and driving factors of carbon emissions and climate change. The Chinese literature focuses on achieving regional carbon emissions reductions and carbon cycle goals and optimizing a low-carbon economy, transportation and land-use structure. (3) Research frontiers and trends show that the English literature first explored carbon sequestration, organic carbon, and carbon accounting. In China, the research frontiers are gradually becoming focused on influencing factors, decoupling analysis, and the built environment. The study will strengthen the intensity and depth of global carbon emission research and provide a reference for improving global climate change, protecting ecology and balancing economic development. [ABSTRACT FROM AUTHOR]

Due to the serious problems with energy efficiency, carbon emissions, and thermal comfort of rural residences in northern China, an optimization of active and passive heating technologies for rural residences is necessary. In this paper, an optimization for rural residences in northern China is conducted with four objectives: the whole life cycle carbon emission; the annual energy consumption through heating, ventilation, and air conditioning systems; the annual cost; and thermal comfort. In addition, the optimization model with active–passive heating technology synergy is resolved by NSGA-II genetic algorithm. The active and passive design variables, including the type of air source heat pump, orientation, the type and thickness of envelope insulation, the layer of window glass, the window-to-wall area ratio, as well as sunspace parameters are preferred to obtain the optimal solution. The results indicate that the optimal solution obtained by the ideal point method gives the most outstanding performance. Compared with the prototype, the optimized carbon emissions in severe cold and cold regions decreased by 56.1% and 54.6%, respectively. The annual energy consumption decreased by 59.7% and 62.2%. Finally, the roof insulation thickness is the most sensitive design variable in Pareto-optimal solution sets. This paper offers significant guidance in the application of the optimization method of active–passive technology synergy to the energy-saving design of buildings. [ABSTRACT FROM AUTHOR]

Amending the definition of energy land, this paper calculates and analyzes China's energy ecological footprint, energy biocapacity, energy ecological deficit or surplus, energy ecological footprint efficiency, and energy ecological footprint index based on the carbon cycle. Meanwhile, this paper applies the ARIMA model to predict China's energy ecological footprint. The results show that the per capita energy ecological footprint continues to rise and the per capita energy biocapacity continues to decline. In 2010, the growth of China's energy ecological footprint exceeds energy biocapacity for the first time and becomes an unsustainable state. Energy ecological footprint efficiency continues to increase and is in an ecological deficit and economically developed zone after 2010. From a structural point of view, China's energy ecological footprint mainly consists of row coal, coke, and crude oil consumption. The main reason for the increase in energy ecological footprint is the rapid increase in row coal and crude oil consumption while energy efficiency can mitigate this impact. From 2020 to 2030, China's energy ecological footprint will increase from 1.2207 to 1.3573 ha/cap. [ABSTRACT FROM AUTHOR]

Deciphering riverine dissolved carbon dynamics is pivotal for a comprehensive picture of the global carbon cycle. Through rigorous in-situ sampling across the Pearl River Basin (PRB), our investigation reveals the Pearl River networks function as a significant carbon source, with the annual carbon dioxide (CO 2 ) emission of 2.57 ± 1.94 Tg C, which offsets 10 ± 8 % of the forest carbon sequestration or 65 ± 49 % carbon sink via chemical weathering in the PRB. Based on the mass balance of 222 Rn, we initially reveal that the contributions of water flux from the hyporheic zone increased with the river orders (Hack Order) across both dry and wet seasons. Conversely, the evasion rates of dissolved CO 2 (CO 2 *) and dissolved inorganic carbon (DIC) from the hyporheic zone into river channels exhibited a decline with the increasing river orders. The hyporheic exchange contributes 4 - 11 % of the lateral and vertical DIC losses, thereby is a key mechanism in the riverine carbon cycle. Furthermore, CO 2 * derived from the hyporheic zone was ∼4 times of riverine CO 2 emissions and this CO 2 * flux from the hyporheic zone was buffered into carbonates/bicarbonates in river channels, due to the high riverine pH resulted from carbonate weathering in the basin. These results not only highlight the substantial role of carbonates and hyporheic processes in modulating riverine carbon fluxes but also signify their broader implications on understanding riverine carbon dynamics at both regional and global scales., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The dune ecosystem plays a significant role in the global carbon cycle. The Horqin Sandy Land is a typical semi-arid fragile ecosystem in northern China. Understanding the magnitudes and dynamics of carbon dioxide fluxes within this region is essential for understanding the carbon balance. Used 6 years (2013-2018) measurements from an eddy-covariance system, we analyzed the dynamic patterns of net ecosystem carbon exchange (NEE), gross primary production (GPP), and ecosystem respiration (Reco) of the dune ecosystem in Horqin Sandy Land and examined their responses to climate factors with a focus on the precipitation. The results showed that the NEE of the dune ecosystem fluctuated from -166 to 100 gCO 2 ·m -2 ·year -1 across the 6 growing seasons, with an average of -56 gCO 2 ·m -2 ·year -1 . The precipitation was not a key factor influencing the carbon flux variability. During the mid-growth stage, GPP was primarily affected by the effective precipitation frequency (R 2 ranging from 0.65 to 0.85, P < 0.05), followed by fractional vegetation cover (R 2 ranging from 0.65 to 0.68, P < 0.05). However, in the early and late growth stages, temperature predominantly drove the carbon flux (R 2  = 0.75, P < 0.01). The interannual variability of carbon flux can be predominantly elucidated by phenological indicators such as CO 2 uptake (CU start ), end of CO 2 uptake (CU end ), CO 2 uptake period (CUP), and Spring lag. The results demonstrated the dune ecosystem is a weak carbon sink in semi-arid ecosystems. Furthermore, we emphasized the significance of effective precipitation frequency in regulating carbon fluxes. Our results provide a foundational understanding of the carbon balance in semi-arid ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

The persistence of dissolved organic matter (DOM) plays a crucial role in the cycling and distribution of carbon and nutrients. Nonetheless, our understanding of how environmental alterations affect the persistence of sedimentary DOM remains incomplete. Excitation Emission Fluorescence Matrix-Parallel Factor Analysis (EEM-PARAFAC) was used to examine the fluorescence and compositional characteristics of hydrophilic and hydrophobic DOM (separated using XAD-8 resin) within sediments from twelve lakes and reservoirs. Fluorescence analysis indicated that DOM persistence is dependent on the proportions of the three components derived from PARAFAC. The Mantel test showed that climatic factors had the most significant impact on DOM persistence (Mantel's r = 0.46-0.54, Mantel's p = 0.001-0.007), while anthropogenic (Mantel's r = 0.24-0.32, Mantel's p = 0.03-0.05) and hydrological factors (Mantel's r = 0.03-0.22, Mantel's p = 0.06-0.40) had a somewhat lesser influence. Environmental changes resulted in a consistent decline in DOM persistence from Northeast to Southwest China, accompanied by an increase in gross primary productivity (GPP). Reduced DOM persistence due to climate, hydrological, and anthropogenic factors may lead to elevated concentrations of total phosphorus (TP), contributing to deteriorating water quality and events such as algal blooms. The decline in water quality due to reduced DOM persistence in lakes with high GPP can exacerbate the transition from carbon sinks to carbon sources. Consequently, the persistence of sedimentary DOM significantly influences nutrient and carbon cycling in lakes. Investigating DOM persistence in lakes across diverse geographic locations offers a new perspective on lake eutrophication and carbon emissions. Furthermore, it is crucial to develop targeted recommendations for lake restoration and management., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Carbon-fixing bacterial communities are essential drivers of carbon fixation in estuarine ecosystems that critically affect the global carbon cycle. This study compared the abundances of the Calvin cycle functional genes cbbL and cbbM and Reductive tricarboxylic acid cycle gene aclB, as well as compared carbon-fixing bacterial community features in the two estuaries, predicted potential ecological functions of carbon-fixation bacteria, and analyzed their symbiosis strategies in two estuaries having different geographical distributions. Gammaproteobacteria was the dominant carbon-fixing bacterial community in the two estuaries. However, a higher number of Alphaproteobacteria were noted in the Liaohe Estuary, and a higher number of Betaproteobacteria were found in the Yalujiang Estuary. The carbon-fixing functional gene levels exhibited the order of aclB > cbbL > cbbM, and significant effects of Cu, Pb, and petroleum were observed (p < 0.05). Nitrogen-associated nutrient levels are major environmental factors that affect carbon-fixing bacterial community distribution patterns. Spatial factors significantly affected cbbL carbon-fixing functional bacterial community structure more than environmental factors. With the increase in offshore distance, the microbial-led processes of methylotrophy and nitrogen fixation gradually weakened, but a gradual strengthening of methanotrophy and nitrification was observed. Symbiotic network analysis of the microorganisms mediating these ecological processes revealed that the carbon-fixing bacterial community in these two estuaries had a non-random symbiotic pattern, and microbial communities from the same module were strongly linked among the carbon, nitrogen, and sulfur cycle. These findings could advance the understanding of carbon fixation in estuarine ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The increases in extent and frequency of extreme drought events and increased nitrogen (N) deposition due to global change are expected to have profound impacts on carbon cycling in semi-arid grasslands. However, how ecosystem CO 2 exchange processes respond to different drought scenarios individually and interactively with N addition remains uncertain. In this study, we experimentally explored the effects of different drought scenarios (early season extreme drought, 50 % reduction in precipitation amount, and 50 % reduction in precipitation events) and N addition on net ecosystem CO 2 exchange (NEE), ecosystem respiration (ER), and gross ecosystem productivity (GEP) over three growing seasons (2019-2021) in a semi-arid grassland in northern China. The growing-season ecosystem carbon fluxes in response to drought and N addition were influenced by inter-annual precipitation changes, with 2019 as a normal precipitation year, and 2020 and 2021 as wet years. Early season extreme drought stimulated NEE by reducing ER. 50 % reduction in precipitation amount decreased ER and GEP consistently in three years, but only significantly suppressed NEE in 2019. 50 % reduction in precipitation events stimulated NEE. Nitrogen addition stimulated NEE, ER, and GEP, but only significantly in wet years. The structural equation models showed that changes in carbon fluxes were regulated by soil moisture, soil temperature, microbial biomass nitrogen (MBN), and the key plant functional traits. Decreased community-weighted means of specific leaf area (CWM SLA ) was closely related to the reduced ER and GEP under early season extreme drought and 50 % reduction in precipitation amount. While increased community-weighted means of plant height (CWM PH ) largely accounted for the stimulated ER and GEP under 50 % reduction in precipitation events. Our study stresses the distinct effects of different drought scenarios and N enrichment on carbon fluxes, and highlights the importance of soil traits and the key plant traits in determining carbon exchange in this water-limited ecosystem., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The poverty-stricken counties on the Qinghai-Tibet Plateau are characterized by ecological vulnerability and ecological degradation, which are vulnerable to economic development and human activities, thereby leading to frequent alterations of Land carbon sink changes. Therefore, it is of great significance to study the changes of land carbon sink capacity during the process of eradication of extreme poverty in poverty-stricken counties. Using remote sensing images and socio-economic data, this paper constructed land transfer matrix and land carbon sink model to analyze the changes of land carbon sink capacity in poverty-stricken counties and identified the relevant impact factors through geographic detectors. The results show significant changes in carbon sink-type land and a continuous decrease in the snow area, resulting in an obvious trend of grassland area decrease and barren area increase. Land carbon sink capacity of poverty-stricken counties during the eradication of extreme poverty is higher with an added value of 2.74 times than that before this period. Using the geographic detector to analyze the related factors, strong explanatory power was found in cash crops per capita, share of secondary industry, population density and per capita savings on the changes of carbon sink capacity in poverty-stricken counties. [ABSTRACT FROM AUTHOR]

The "Dual Carbon" initiative is a two-stage carbon reduction goal proposed by China, with significant implications for global climate change mitigation. This article examines the impact of the "Dual Carbon" strategy on China's forestry development and explores how to leverage this strategy to facilitate the transformation and advancement of the forestry sector. Current review indicated that forestry has the advantage of achieving higher emission reduction targets at a low cost. Starting with an overview of the "Dual Carbon" strategy, this paper analyzes the carbon sequestration potential of plants and soil, and the challenges and opportunities faced by forestry development under this framework. Furthermore, we outline implementation pathways for forestry development, aiming to provide insights for the progress of China's forestry sector. Overall, it should be noted that the priority is to vigorously develop timber resources, and we also need to vigorously develop and protect forestry talent with the support of China's policies. By trapping into the carbon storage capabilities and leveraging carbon trading mechanisms of forests, a favorable ecological environment can be created, thus achieving the goal of carbon neutrality. Highlights: • Forest development and its carbon sinks, attributed to plant and soil have the potential in carbon sequestration process, thus helping China achieve carbon neutrality. • The supply of forest products and the balance of economic growth and environmental protection are the key difficulties under the "Dual Carbon" strategy. • Trading forest carbon sinks can boost China's sequestration. [ABSTRACT FROM AUTHOR]

Background: China has made great progress in ecological restoration. However, there have been no analyses on ecological restoration for specific terrestrial ecosystems. This study identified the important knowledge gaps and advances related to terrestrial ecological restoration in China. Results: 7973 papers published between 1978 and 2020 were investigated and about 962 articles were used in this analysis after manually screening. Since the first large national ecological restoration project in 1978, the most frequently studied ecosystem has shifted from farmland ecosystems in 1978–2000 to forest ecosystems after 2000. Forests were the most common ecosystem type investigated, while less attention was paid to wetlands and riparian systems. Meanwhile, the most common ecological issue shifted from environmental pollution in 1978–2000 to the declining resource-carrying capacity of ecosystems after 2000. Studies of ecoregions on the Loess Plateau catchment accounted for more than 40% of papers reviewed in this study, with predominant emphasis on soil and water conservation functionality. Besides, revegetation and afforestation characterized most ecological restoration projects in China, but the natural restoration was relatively less adopted. Additionally, the important tool of reference ecosystem was only used in four studies. Conclusions: Ecological restoration has made significant progress in China. We investigated how the ecological restoration can be implemented more effectively. More projects should be implemented for restorative work in wetlands and riparian systems in future. The tradeoff between restorative activities, water resources, and carbon sink needs further research efforts. More emphasis on biodiversity conservation is warranted. Newly developed theory (e.g., stepwise ecological restoration) and the recently issued Chinese National Guidelines for Ecological Restoration Projects should be more effectively implemented in future restorative works. This study provides essential information for future restorative work in China. It also provides insights into the development of policy relevant to restoration and adaptive management during the U.N. restoration decade. [ABSTRACT FROM AUTHOR]

In the past few decades, human activities have caused the emission of large amounts of carbon dioxide, which has severely impacted the Earth's ecosystem and human health. Therefore, carbon reduction has become the focus of global attention. In this study, the Zhouyuan region of China, which is rich in ancient remains, is taken as an example. Based on the land use characteristics in 1990, 2000, 2010, and 2020, the spatial-temporal evolution of land use and carbon storage in the Zhouyuan region is simulated using four methods, including land use classification, land use transfer maps, patch-level land-use simulation (PLUS), and the integrated valuation of ecosystem services and trade-offs (InVEST) models under three scenarios, including the natural development scenario, urban development priority, and heritage conservation priority in 2030. According to the results, the carbon storage in the area in 2030 under all three scenario simulations has decreased compared with 2020, indicating that the region faces great challenges in achieving its targets of carbon peak and carbon neutrality. The paper points out four causes for the decrease in carbon storage, and five suggestions for increasing carbon storage are proposed, such as developing a carbon storage master plan, applying energy-saving technologies, establishing an ecological substitution mechanism, and so on. Through the study of carbon storage in the Zhouyuan region, this paper hopes to establish a mechanism to balance urban development, heritage conservation, and carbon sinks on the one hand, and encourage more scholars to participate in the study of carbon sinks in areas rich in ancient remains, so as to to jointly promote their healthy development on the other. [ABSTRACT FROM AUTHOR]

Lifespan of fine roots plays important roles in regulating carbon (C) cycling in terrestrial ecosystems. Determination of root lifespan and elucidation of its regulatory mechanism in different plant communities are essential for accurate prediction of C cycling from ecosystem to regional scales. Temperate steppes in Inner Mongolia grasslands have three major types, i.e., Stipa krylovii, Stipa grandis and Stipa breviflora grasslands. There have been no studies to compare the root dynamics among the three types of grasslands. In the present study, we determined root lifespan of the three grasslands using the rhizotron. We found that root lifespan differed substantially among the three types of grasslands within the temperate steppes of Inner Mongolia, such that root lifespan of Stipa breviflora > Stipa grandis > Stipa krylovii grasslands. Root lifespan across the three types of grasslands in the Inner Mongolian temperate steppes displayed a similar temporal pattern, i.e. lifespan of the roots produced in spring and autumn was shortest and longest, respectively, whereas lifespan of summer-produced roots was between that of roots produced in spring and autumn. The spatial and temporal differences in root lifespan across the three types of grasslands were mainly determined by contents of soluble sugars in roots of the dominant species. The differences in root lifespan across the major types of grasslands and different seasons highlight the necessity to take into account these differences in the prediction of C cycling within grassland ecosystem by the simulating model. [ABSTRACT FROM AUTHOR]

Forests play a leading role in regional and global terrestrial carbon (C) cycles. Changes in C sequestration within forests can be attributed to areal expansion (increase in forest area) and forest growth (increase in biomass density). Detailed assessment of the relative contributions of areal expansion and forest growth to C sinks is crucial to reveal the mechanisms that control forest C sinks and is helpful for developing sustainable forest management policies in the face of climate change. Using the Forest Identity concept and forest inventory data, this study quantified the spatial and temporal changes in the relative contributions of forest areal expansion and increased biomass growth to China's forest C sinks from 1977 to 2008. Over the last 30 years, the areal expansion of forests was a larger contributor to C sinks than forest growth for all forests and planted forests in China (74.6 vs. 25.4% for all forests, and 62.4 vs. 37.8% for plantations). However, for natural forests, forest growth made a larger contribution than areal expansion (60.4 vs. 39.6%). The relative contribution of forest growth of planted forests showed an increasing trend from an initial 25.3 to 61.0% in the later period of 1998 to 2003, but for natural forests, the relative contributions were variable without clear trends owing to the drastic changes in forest area and biomass density over the last 30 years. Our findings suggest that afforestation can continue to increase the C sink of China's forests in the future subject to persistently-increasing forest growth after establishment of plantation. [ABSTRACT FROM AUTHOR]

Eucalyptus plantation forests in southern China provide not only the economic value of producing timber, but also the ecological value service of absorbing carbon dioxide and releasing oxygen. Based on the theory of spatial colonial modeling, this paper proposes a new method for 3D reconstruction of tree terrestrial LiDAR point clouds for determining the aboveground carbon stock of eucalyptus monocotyledons, which consists of the main steps of tree branch and trunk separation, skeleton extraction and optimization, 3D reconstruction, and carbon stock calculation. The main trunk and branches of the tree point clouds are separated using a layer-by-layer judgment and clustering method, which avoids errors in judgment caused by sagging branches. By optimizing and adjusting the skeleton to remove small redundant branches, the near-parallel branches belonging to the same tree branch are fused. The missing parts of the skeleton point clouds were complemented using the cardinal curve interpolation algorithm, and finally a real 3D structural model was generated based on the complemented and smoothed tree skeleton expansion. The bidirectional Hausdoff distance, average Hausdoff distance, and F distance were used as evaluation indexes, which were reduced by 0.7453 m, 0.0028 m, and 0.0011 m, respectively, and the improved spatial colonization algorithm enhanced the accuracy of the reconstructed tree 3D structural model. To verify the accuracy of our method to determine the carbon stock and its related parameters, we cut down 41 eucalyptus trees and destructively sampled the measurement data as reference values. The R2 of the linear fit between the reconstructed single-tree aboveground carbon stock estimates and the reference values was 0.96 with a CV(RMSE) of 16.23%, the R2 of the linear fit between the trunk volume estimates and the reference values was 0.94 with a CV(RMSE) of 19.00%, and the R2 of the linear fit between the branch volume estimates and the reference values was 0.95 with a CV(RMSE) of 38.84%. In this paper, a new method for reconstructing eucalyptus carbon stocks based on TLS point clouds is proposed, which can provide decision support for forest management and administration, forest carbon sink trading, and emission reduction policy formulation. [ABSTRACT FROM AUTHOR]

Carbon emissions and land use intensity serve as crucial indicators of land management. This paper proposes a methodological framework to elucidate the sustainability of carbon emissions in rural areas via a coordination model, scrutinizes the correlation with land use intensity, and investigates the significance of influential factors. The study focuses on village-level units within Ningde City, and finds the pronounced spatial heterogeneity characterizing the distribution of carbon emissions across different villages: (1) Villages exhibiting high levels of carbon emissions are predominantly concentrated in the southeast region, whereas those with low carbon emission levels are primarily clustered in the northwest region. The majority of the villages serve as net carbon emission sources. (2) Spatial disparities exist in the impact of land use intensity on economic benefits from carbon sources, ecological benefits from carbon sinks, and carbon emission sustainability. (3) Significant variations exist in the influence of factors affecting land use intensity, economic benefits of carbon sources, ecological benefits of carbon sinks, and the sustainability of carbon emissions in rural areas. These findings could guide governments in implementing distinct land use control policies and provide a framework for assessing carbon emission sustainability within land management strategies. [ABSTRACT FROM AUTHOR]

As a world-class urban agglomeration, the Yangtze River Delta urban agglomeration is significant for China's carbon neutrality strategy when calculating the carbon budget and dividing carbon compensation zones. This paper focused on 129 county-level cities in the core area of the Yangtze River Delta urban agglomeration, calculating the carbon budget for 2000–2020 using night-time light data and analyzing the evolution of spatiotemporal patterns. On this basis, a carbon compensation zoning model was constructed using the K-means algorithm; 129 cities were divided into different carbon compensation zones after combining this model with the main functional zones. The results showed that (1) the carbon emissions increased, with overall stabilization after 2012. The distribution of high carbon emission areas evolved from a "core-periphery" pattern into a "Z-shaped" pattern. Ecological carbon sinks showed a continuous decline, with the southern sinks performing better than the northern ones. (2) The carbon budget of the study area showed a deficit, gradually widening and exhibiting an unbalanced spatial distribution characterized by a "high in the south and low in the north" pattern. (3) Eleven types of carbon compensation zones were designated after overlaying the main functional zones. Low-carbon development suggestions were proposed for each zone type. [ABSTRACT FROM AUTHOR]

China's rapid economic development has consumed a large amount of energy, causing serious environmental pollution problems and contributing to global warming. This paper calculates the carbon emissions of the fishery sector and uses Random Forest (RF) for the first time to analyze the influencing factors of future carbon emissions. The results of the study show that increasing carbon sinks dominate the reduction of carbon emissions in the fisheries sector. Carbon sinks will continue to dominate emission reductions in the fisheries sector if positive mitigation measures are taken. Continuing the current pattern of fisheries development, the fishery population has a significant impact on future carbon emissions. Per capita incomes under a crude economic model will inhibit carbon emission reductions. The research results can provide guidance for the development of fishery low carbon economy and the formulation of emission reduction policies. [ABSTRACT FROM AUTHOR]

Carbon flow in forest products trade will affect the report of a country's carbon stock. This will have an impact on a country's contribution of carbon flows. Based on the analysis of China's forest product trade, this paper uses the stock-change approach, the production approach and the atmospheric-flow approach to calculate the changes of China's forest products trade carbon flows. Different carbon flow measurement approaches have very different results. From the perspective of the contribution of forest products to carbon flow, the production approach of calculation for forest products trade carbon flow has the largest contribution to atmospheric carbon flows. However, the calculation results of the stock-change approach and the atmospheric-flow approach are just the opposite, that is, the calculation for forest products trade has a negative contribution to China's carbon sinks, and forest products trade has become a source of carbon emissions. [ABSTRACT FROM AUTHOR]

Anthropogenic land cover change is one of the primary sources of increasing carbon emissions and affects the potential of terrestrial ecosystems to store carbon and act as carbon sinks. As a necessary means to reduce land expansion, land-use intensification significantly impacts greenhouse gas emission reduction and the low-carbon transition of the economy. This paper constructs a framework for the relationship between intensive land use (ILU) and low carbon transition (LCT), considering direct and spatially driven effects. First, this paper constructs a multidimensional indicator to measure intensive land use and documents the spatial pattern of intensive land use levels in China. Second, this paper assesses the spatial driving effect of intensive land use on China's economic low-carbon transition. Based on data from 283 Chinese cities from 2006–2019 and using a spatial Durbin model, the study provides empirical evidence that intensive land use can significantly promote low-carbon transition in neighboring and economically linked cities (especially in eastern cities, large and medium-sized cities, and veteran economic circles). Tests introducing exogenous policy shocks further confirm the robustness of the findings. In addition, industrial structure transformation and technology spillovers are identified as the dual mechanism channels of intensive land use for low-carbon transition in China, and the spatial driving effect on neighboring cities attenuating with geographic distance is also confirmed. [ABSTRACT FROM AUTHOR]

The relationship between population, agriculture, and carbon dioxide emissions has been an issue of concern to scientists and institutions for many years. Concerns about the impact of population growth on the environment and agriculture go back several decades. As the world's population continued to grow, scientists and researchers became increasingly aware of the potential consequences of this growth on food production, resource use, and greenhouse gas emissions. A growing population means higher demand for food. This has increased pressure on agriculture to produce more food, often leading to increased acreage and more intensive farming methods. Intensification involves the increased use of fertilizers, pesticides, and machinery, which can lead to higher greenhouse gas emissions. The goal of this study is to quantify the contribution of agriculture and population growth to carbon dioxide emissions. In this context, 412 papers were found on the Web of Science. Papers in this area often address the role of agriculture in greenhouse gas emissions, including its direct and indirect effects on the carbon cycle. Although most studies were published in 2020, the number of publications has changed over time as regulations in the field have emerged. The data show that the country with the most authors is China, which is recognized as a country with a significant increase in scientific research. [ABSTRACT FROM AUTHOR]

Land-use–cover change (LUCC)/vegetation cover plays a critical role in Earth system science and is a reflection of human activities and environmental changes. LUCC will affect the structure and function of ecosystems and a series of other terrestrial surface processes, such as energy exchange, water circulation, biogeochemical circulation, and vegetation productivity. Therefore, accurate LUCC mapping and vegetation cover monitoring are the bases for simulating the global carbon and hydrological cycles, studying the interactions of the land surface and climate, and assessing land degradation. Based on field GPS surveys and UAV data, with cloud-free and snow/glacier algorithms and the SVM classifier to train and model alpine grassland, the alpine grassland and LUCC were extracted by using Landsat-8 OLI satellite images in Sanjiangyuan National Park in this paper. The latest datasets of vegetation types with 30 m × 30 m spatial resolution in the three parks were prepared and formed. The classification results show that the SVM classifier could better distinguish the major land-use types, and the overall classification accuracy was very high. However, in the alpine grassland subcategories, the classification accuracies of the four typical grasslands were relatively low, especially between desert steppes and alpine meadows, and desert steppes and alpine steppes. It manifests the limitations of Landsat-8 multispectral remote sensing imageries in finer-resolution grassland classifications of high-altitude alpine mountains. The method can be utilized for other multispectral satellite imageries with the same band matching, such as Landsat 7, Landsat 9, Sentinel-2, etc. The method described in this paper can rapidly and efficiently process annual alpine grassland maps of the source areas of the Yellow River, the Yangtze River, and the Lancang River. It can provide timely and high-spatial-resolution datasets for supporting scientific decisions for the sustainable management of Sanjiangyuan National Park. [ABSTRACT FROM AUTHOR]

Understanding the impact mechanisms of territorial space composition and landscape pattern changes on carbon storage is critical to balance the development and utilization of territorial space and the conservation of the ecosystem. Thus, taking the Fujian Delta urban agglomeration (FDUA) of China as an example, this paper analyzed the impact of the transference in territorial space composition and the change in the coupling coordination degree (CCD) of landscape patterns on carbon storage based on the urban–rural gradient and grid scales. Results illustrated that the areas of agricultural, green, and blue spaces continued to decline, while the intensity of economic space expansion increased from 20.86 to 42.45% during 2000–2020. The grids with CCD change of landscape patterns declined mainly (accounting for 64.31%) in the first decade and rose mainly (accounting for 76.79%) in the second decade. The carbon loss of each under rural gradient was gradually serious. The percentage of grids with moderate and significant decrease in carbon storage escalated from 27.83 to 70.21%. Additionally, grids experiencing high carbon loss moved from the northeast coast to the southwest inland. The response of carbon storage change showed that the expansion of agricultural space occupied by economic space played a crucial role in the carbon loss in each urban–rural gradient. The carbon loss caused by supplementing agricultural space with green space increased from the urban to the field. Enhancing the CCD of landscape patterns can boost carbon storage, and the scattering expansion of economic space needs to be avoided. This paper provides a novel perspective to explore the spatial response of carbon storage change to the territorial space composition and landscape pattern evolution, which is important to optimize the territorial space pattern and improve the regional carbon sink capacity. [ABSTRACT FROM AUTHOR]

Southwest China is one of the three largest continuous karst clusters in the world; therefore, studies on karst rocky desertification in this area are very important. For more than 20 years' control, the decreasing area and risk of karst rocky desertification has contributed to the continuous ecological improvement. Nowadays, studies on rocky desertification mainly focus on the eight provinces in Southwest China, which have been designated as rocky desertification monitoring areas by the Chinese government. After the first phase of the comprehensive control project for karst rocky desertification in 2016, the expansion trend of rocky desertification in the southwest region was effectively curbed. Subsequent articles published tend to focus on analyzing the current situation, comprehensive management, or species adaptability of rocky desertification monitoring areas. However, the Qinba region in Shaanxi Province is located outside the monitoring area. In the process of studying the karst geological relics of the Zhenba Sanyuan Tiankeng Group, signs of rocky desertification have been found, but there still exists a research gap in the investigation and research on karst rocky desertification in this area which is one of the areas with the richest biodiversity in China, known as "ecological lung", "central water tower" and "biological gene bank". Unfortunately, this area is burdened with poverty, so the investigation and study of karst rocky desertification in the Qinba region of Shaanxi Province is of great significance to ensure green and high-quality development and ecological civilization construction. In this paper, by analyzing the current situation of karst rocky desertification in Southwest China, we summarized its harm to the ecological environment and social economy, clarify natural and human factors resulting in rocky desertification, and integrate the typical treatment experience in Southwest China. We also introduce three technical methods, including remote sensing interpretation, UAV remote sensing survey and analysis of carbonate dissolution rate, to provide a scientific basis for studies on karst rocky desertification in the Qinba region of Shaanxi Province. Study results show that the area of karst rocky desertification in the Qinba region covers 63.37 km², and the areas of severe, moderate and mild rocky desertification cover 17.97 km², 21.60 km² and 23.80 km², respectively. Based on the survey results, there are both regional differences and some similarities in distribution patterns in the areas of rocky desertification development. Specifically, the degree of rocky desertification in the limestone area is more severe than that in the dolomite area. It is also more severe in the area with developed water system than that in the arid and semi-arid area, and the more active the new structure is, the more severe the rocky desertification is. Compared to the Southwest China, the degree of karst rocky desertification in the Qinba region of Shaanxi Province is relatively light, with a smaller distribution area, mainly due to the less rainfall in the study area. The karst rocky desertification in Beiyang mountain of Zhen'an county is the most severe, with an area of 7.28 km². In the 1960s, a large-scale free-range of livestock severely damaged vegetation. The indiscriminate deforestation by humans further exacerbated the process of rocky desertification. The rocky desertification in Hailuogong village of Shanyang county is also severe, covering an area of 5.83 km², because the landform in this area is a typical peak-cluster depression, which is likely developed into rocky desertification. The contradiction between people and land needs to be solved urgently. In conclusion, more monitoring and research efforts are needed in Beiyang mountain and Hailuogong where the rocky desertification is severe. Firstly, we should clarify the causes of rocky desertification in the Qinba region and compare them with the causes in Southwest China to determine whether the rocky desertification is mainly resulted from natural factors or human factors. Secondly, we should know how to clarify the causes of karst rocky desertification in the Qinba region; for example, we can dynamically monitor the change of rock desertification by field verification, remote sensing interpretation, climate change analysis, etc. We can also calculate the contribution rate of each influence factor by geographical detector model. Thirdly, we should further study influence factors of karst dissolution rate. We can monitor physical and chemical properties of soil (soil moisture, carbon dioxide concentration, pH, organic matter content and porosity) in areas with moderate to severe rocky desertification, and analyze the relationship between dissolution rate and physical and chemical properties of soil in rocky desertification areas. Finally, in order to provide basic data for carbon neutrality research in Shaanxi, we should conduct studies on the carbon sink of rocky desertification areas in the Qinba region, with the methods such as dissolution test pieces and hydrochemical runoff. [ABSTRACT FROM AUTHOR]

The local land use carbon budget (LUCB) balance is an important factor in achieving regional carbon neutrality. As the basic unit of China's economic development and social governance, the county level is an important part of the realization of the "double carbon" goal. This paper focuses on 1069 county units within the Yangtze River Economic Belt (YREB). It utilizes data on land use, nighttime light, energy consumption, and social and economic factors to construct carbon emission models. The spatiotemporal characteristics of LUCB in these county units are analyzed using standard deviational ellipse (SDE) and spatial autocorrelation methods. Additionally, a zoning study is conducted by examining the economic contribution coefficient (ECC) of carbon emissions, the ecological support coefficient (ESC), and their coupling relationship. The results show that (1) the total land use carbon emissions (LUCE) increased significantly during the research period, and the total carbon sink was relatively stable. (2) The LUCB is spatially high in the east and low in the west, with the center of gravity moving to the southwest as a whole. (3) The LUCB shows positive spatial autocorrelation and has significant spatial agglomeration characteristics, which are mainly high–high and low–low regional agglomeration types. (4) The ECC is high in the east and low in the west, the ESC is high in the west and low in the east, and the coordination and coupling degrees of the two are low. (5) According to the ECC and ESC, the county unit is divided into a low-carbon conservation area, an economic development area, a carbon sink development area, and a comprehensive optimization area. This study is helpful in promoting the sustainable development of carbon neutrality and low carbon in the YREB. [ABSTRACT FROM AUTHOR]

Globally, forest ecosystems, especially subtropical forests, play a central role in biogeochemical cycles and climate regulation, demonstrating their irreplaceable function. The subtropical region of China, characterized by its unique forest ecosystem, complex terrain, climate heterogeneity, diverse vegetation types, and frequent human activities, underscores the importance of the in-depth study of its net primary productivity (NPP). This paper employs the eddy covariance–light use efficiency (EC-LUE) model to quantitatively estimate the gross primary productivity (GPP) of this region from 2001 to 2018, followed by an estimation of the actual net primary productivity (ANPP) using the carbon use efficiency (CUE). The results showed that over these 18 years, the annual average ANPP was 677.17 gC m−2 a−1, exhibiting an overall increasing trend, particularly in mountainous areas, reserves, and the cultivated lands of the northeastern plains, whereas a significant decrease was observed around the urban agglomerations on the southeast coast. Furthermore, the Thornthwaite memorial model was applied to calculate the potential net primary productivity (PNPP), and diverse scenarios were set to quantitatively evaluate the impact of climate change and human activities on the vegetation productivity in the study area. It was found that in areas where the ANPP increased, both human activities and climate change jointly influenced ANPP dynamics; in areas with a decreased ANPP, the impact of human activities was particularly significant. Additionally, the heterogeneous distribution of ANPP across different altitudinal gradients and the driving effects of various climatic factors were analyzed. Finally, a partial correlation analysis was used to examine the relationships between the temperature, precipitation, and ANPP. This study indicated that temperature and precipitation have a substantial impact on the growth and distribution of vegetation in the region, yet the extent of this influence shows considerable variation among different areas. This provides a robust scientific basis for further research and understanding of the carbon dynamics of subtropical forest ecosystems and their role in the global carbon cycle. [ABSTRACT FROM AUTHOR]

Forest stock volume is the main factor to evaluate forest carbon sink level. At present, the combination of multi-source remote sensing and non-parametric models has been widely used in FSV estimation. However, the biodiversity of natural forests is complex, and the response of the spatial information of remote sensing images to FSV is significantly reduced, which seriously affects the accuracy of FSV estimation. To address this challenge, this paper takes China's Baishanzu Forest Park with representative characteristics of natural forests as the research object, integrates the forest survey data, SRTM data, and Landsat 8 images of Baishanzu Forest Park, constructs a time series dataset based on survey time, and establishes an FSV estimation model based on the CNN-LSTM-Attention algorithm. The model uses the convolutional neural network to extract the spatial features of remote sensing images, uses the LSTM to capture the time-varying characteristics of FSV, captures the feature variables with a high response to FSV through the attention mechanism, and finally completes the prediction of FSV. The experimental results show that some features (e.g., texture, elevation, etc.) of the dataset based on multi-source data feature variables are more effective in FSV estimation than spectral features. Compared with the existing models such as MLR and RF, the proposed model achieved higher accuracy in the study area (R2 = 0.8463, rMSE = 26.73 m3/ha, MAE = 16.47 m3/ha). [ABSTRACT FROM AUTHOR]

Improving the efficiency of carbon sequestration in Marine fisheries is an important way for China to achieve the goal of carbon neutrality. This paper uses the Super-SBM model to calculate the carbon sink efficiency of Marine fisheries in nine coastal provinces of China, and analyzes its global and local spatial autocorrelation. Meanwhile, the spatial Dubin model is used to analyze the influencing factors and spatial spillover effects of carbon sink efficiency in Marine fisheries. The study found that: (1) the overall efficiency level of Marine fisheries in nine coastal provinces of China is relatively high, Regional differences are significant; (2) From the overall perspective, There is a spatial positive correlation between the efficiency of carbon sink in regional Marine fisheries, Agglomeration effect is significant; (3) From the direct effect, The number of fishery employees and the per capita disposable income of residents can promote the efficiency of carbon sink in Marine fisheries, The total economic output value of mariculture, the power of aquaculture fishing boats and the area of affected aquaculture have an inhibitory effect on the carbon sink efficiency of Marine fishery; (4) In terms of the spatial effect, The number of fishery employees, the power of aquaculture fishing boats, and the per capita disposable income of residents have a positive spatial spillover effect, The total output value of mariculture and the area of aquaculture have negative spatial spillover effect. [ABSTRACT FROM AUTHOR]

Compared to more developed countries, the use of land resources is less efficient in China. China's vast forest land area gives it a rich and underutilized carbon sink. This is an important way for China to achieve the goals of "carbon peaking" and "carbon neutrality", which is of great significance to China's sustainable development. In the past 20 years, China has designed a series of policies to serve the development of forestry carbon sinks, namely the forestry carbon sink mechanism (FCSM). However, the questions of which policy is the most important, and what is the socio-economic value it generates, have not been fully investigated. Accordingly, this paper studied 30 provincial-level regions in China from 2005 to 2020 using the difference-in-differences (DID) model. The conclusions show that: (1) the FCSM does increase the socio-economic value of land resources, thus improving the sustainability of land resources; (2) the FCSM helps to increase forest coverage, forest stock volume and the forest coverage rate, which increases the social value of land resources from the greening path; (3) the FCSM helps to increase the gross forestry product, which increases the economic value of land resources through the path of increasing production value. [ABSTRACT FROM AUTHOR]

To achieve the goal of urban carbon dioxide emission reduction, how to increase carbon sequestration has become a top priority. The biological sink is mainly divided into green carbon sink and blue carbon sink. Coastal cities have two kinds of carbon sinks. There, the study of carbon sinks in coastal cities is the primary choice to cope with climate change. Therefore, this study chooses coastal cities with primary industries including agriculture, fishery, and forestry as the study subjects. The LMDI (Log-Mean Divisia Index) method and multiple regression prediction models were used to explore the low-carbon countermeasures which increase urban net carbon sink from the perspective of influencing factors and future potential. The study found that the average output value of employees in the primary industry is the main driving factor, and the change in the purchasing power of unit carbon sinks and the change in the proportion of employees in the primary industry have inhibited the increase in net carbon sinks. Projections based on the primary industry's output and afforestation area as independent variables show an overall upward trend in net carbon sinks, reaching 15.70 million tons of net carbon sinks in 2060, offsetting 10–20% of total carbon emissions in the same year. Based on the calculation results, this paper puts forward some corresponding countermeasures to increase carbon sinks. This paper provides a theoretical reference for the low-carbon development of coastal cities in China, and the strategies can be also expanded to other cities with similar resources around the world. [ABSTRACT FROM AUTHOR]

As the primary source of carbon dioxide fixation, vegetation is critical to the carbon sink process. In this paper, the Net Primary Productivity (NPP) and the Gross Primary Productivity (GPP) were simulated using the Carnegie-Ames-Stanford Approach (CASA) model and the Vegetation Photosynthesis Model (VPM), respectively, and then the Potential Gross Primary Productivity (PGPP) and the GPP affected by human activities (AGPP) were simulated by combining Potential Net Primary Productivity (PNPP), and then the impact of climate change and human activities on GPP was assessed in the Heihe River Basin (HRB). The results showed that the GPP of grassland and Bare or Sparse Vegetation (BSV) exhibited a fluctuation rise, with increases of 0.709 gCm−2 a−1 and 0.115 gCm−2 a−1, respectively, whereas the GPP of cropland showed a fluctuation reduction, with a decline rate of −0.465 gCm−2 a−1. Climate change and human activity are both positive for vegetation growth, and human activity being the primary factor influencing GPP change. Human-dominated vegetation restoration accounted for 56.1% of the overall restoration area, with grassland GPP being the most visible response to human activities. The GPP changes in crop and grassland had a positive correlation with precipitation but a negative correlation with temperature among climate change factors, whereas the GPP changes in BSV had a negative correlation with both precipitation and temperature. Quantitative analyses of climate change and human activities' dynamic contributions to vegetation can give scientific and theoretical insight for dealing with global climate change. [ABSTRACT FROM AUTHOR]

Provinces (cities and districts) with identifiable boundaries are under intense pressure to reduce emissions as a fundamental unit and research object of carbon peaking and carbon-neutrality goals. Due to the significant variability of regional development, achieving equilibrium between carbon emissions and carbon absorption is challenging, contributing to the difficulty of developing carbon emission reduction and relevant green strategic initiatives in China. Therefore, this paper explored the spatial effect of carbon balance with carbon pressure as the starting point. First, this paper defined the "carbon pressure index" (CPI) of 30 provinces (cities and districts) in China from 2000 to 2019. Second, this paper validated the CPI agglomeration evolutionary characteristics in global and local aspects based on the Moran's index. Third, this paper identified and decomposed the spatial heterogeneity of CPI using the kernel density estimation method and the Theil index, then extracted typical cities to analyze the specific causes. Finally, this paper classified the seven regions in China into four types according to a comprehensive analysis of CPI. The results indicated that China's ecological carbon cycle system was in a serious "carbon overload" state. Thirty provinces (cities and districts) showed significant spatial agglomeration characteristics. The spatial gap of CPI was gradually decreasing nationwide, and the intra-regional differences were the leading cause of CPI levels in China. This can provide policy basis for the improvement of China's balanced development system of regional carbon emission reduction., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

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Accurate measurement of agricultural total factor productivity (AGTFP) is crucial to measure the level of sustainable agricultural development, and agricultural carbon sink is an important element to leverage the development of green transformation. Few studies have incorporated agricultural carbon sink into the measurement framework of AGTFP, and the evolutionary dynamics and related spatial effects of Chinese AGTFP from the perspective of carbon sinks are unclear. On this basis, the paper used a provincial-level agricultural panel data set of China from 2000 to 2019 to measure the provincial indicators of agricultural carbon sinks, CO2 emissions and agricultural non-point source pollution. Then, we incorporated these environmental factors into the measurement framework of AGTFP and used the SBM-DEA model to calculate the Chinese AGTFP from the perspective of carbon sinks. We further analyzed the spatial and temporal divergence and convergence of AGTFP in China using Moran'I and spatial econometric models. We found that after measuring AGTFP, including agricultural carbon sinks, 28 out of 30 Chinese provinces showed an increased trend, but the development gap between regions was obvious. The spatial econometric model showed a significantly positive spatial correlation between the AGTFP of each province and did not have absolute α-convergence and absolute β-convergence characteristics. After adding the control variables of resource endowment of each province, it showed conditional β-convergence characteristics, and the spatial spillover effect of China's AGTFP was increasing. Finally, the paper proposed policy recommendations for the sustainable and coordinated development of China's agricultural regions in response to the research findings. [ABSTRACT FROM AUTHOR]

In the context of carbon peaking and carbon neutrality ("double carbon"), it is urgent to clarify the effect of marine spatial planning (MSP) on carbon sink increases and emission reductions, since such planning acts as a spatial governance tool for the earth's largest carbon pool. In this paper, a linkage model between marine spatial functional zones and carbon distribution is established. To explore the relationship between marine spatial functional zones and carbon, the study analyzed the carbon increase or reduction role of sea-use activities in each zone and considered the carbon sequestration function of the marine ecosystem itself. A marine spatial pattern of "Two Spaces and Four Carbon Areas" is proposed to present the linkage. A carbon distribution pattern in marine space is delimited using the linkage model and the current MSP in the case study of the city of Tangshan, Hebei, China. Some measures have been taken or planned to be taken in Tangshan to improve the carbon sink function of the ecosystem and the marine space. The supporting role of MSP in achieving the "double carbon" goal is studied, and the paths and suggestions for integrating the "double carbon" goal into MSP are explored. [ABSTRACT FROM AUTHOR]

Rubber plantations are among the most important in the world's tropical regions. They play a positive role in carbon sequestration and in delaying climate change, supplying strategic resources of natural rubber (NR), and aiding in poverty alleviation and rural revitalisation. This paper reviews six methods of research on carbon sinks in rubber plantations: the biomass inventory method, the biomass conversion factor continuous function method, the trade potential of carbon sinks method, the calculation method for carbon storage of rubber latex, the eddy covariance method, and the remote sensing image model method. This study clarifies the carbon sink assessment and enhancement model for rubber plantations and describes the composition of the carbon pool, which includes the aboveground and belowground vegetation biomass carbon pools, litter carbon pool, latex carbon pool, and soil carbon pool. It also examines influencing factors such as tree age, global climate change, and human disturbance, as well as improvement pathways including afforestation, fertilisation, irrigation, and tapping, and evaluation methods like field surveys, positional observations, remote sensing monitoring, and model simulation. Research on carbon sequestration in rubber plantations faces challenges, including the unclear dynamics of carbon sources and sequestration, uncertain spatial and temporal patterns, and the long-term lack of accurate monitoring of carbon sinks and technologies for increasing sinks and reducing emissions. Future research should focus on the methodology of rubber plantation carbon sequestration projects, the dynamics of carbon sequestration, and the spatial allocation pattern of carbon sequestration in rubber plantations. [ABSTRACT FROM AUTHOR]

The properties of copper tailings, the relevant policies and current status of comprehensive utilization of copper tailings were systematically reviewed in this paper. The comprehensive utilization direction of copper tailings under the background of dual carbon was further discussed. China has provided a good policy environment for the comprehensive utilization of copper tailings. The comprehensive utilization of copper tailings also shows the characteristics of multiple approaches, directions, and benefits. However, the actual industrial application process still has problems, such as limited methods and low utilization rates. The development of large--scale consumption of copper tailings resources is an important measure to realize the construction of green mines and ecological civilization in China. Under the background of dual carbon, the comprehensive utilization of copper tailings includes two directions: carbon reduction and carbon sink enhancement. The main development direction of copper tailings comprehensive utilization in the future is to realize ecological restoration of tailings pond by adopting efficient improvement measures, increasing the carbon sink of the tailings matrix, and promoting the growth of vegetation carbon pool in mining area as well as establishing the corresponding technical method and standard system. [ABSTRACT FROM AUTHOR]

Achieving carbon neutrality is an important initiative to cope with global warming. Most studies on the role of tourism towards carbon neutrality were based on the carbon emission reduction (CER) perspective while the carbon sink (CS) perspective was lacking. Based on the quasi-natural experiment of high-standard scenic spots, this paper aimed to examine the effect of tourism resources development on regional CS with high-precision multi-source datasets of 2601 Chinese county units. According to the results of the time-varying difference-in-difference (DID) model regression, CNSA significantly deteriorated CS, but the findings of the rolling regression test confirmed that the adverse effect diminished over time. [ABSTRACT FROM AUTHOR]

Carbon sequestration in farmland ecosystems is an important link in the world carbon cycle and plays an important role in regional carbon reduction. Guangdong, a major industrial and economic province in China, was used as the study area, and the period 2001–2020 was taken as the study period. The carbon emissions, sequestration, and footprint of farmland ecosystems in Guangdong were estimated using carbon emission factors for agricultural inputs that are closer to the actual situation in China. The study showed that: (1) Carbon average emissions from farmland in Guangdong during the study period was 3.7624 million t a−1, with a balanced overall trend of change, and that nitrogen fertilize applications was the main factor contributing to carbon emissions. (2) The carbon sink capacity of Guangdong farmland ecosystems showed an overall decreasing trend of 10.32%, with an average annual carbon sink of 19.0363 million t a−1. Paddy and sugar cane cultivations were the main factor of carbon sink in farmland. (3) The average annual carbon footprint of Guangdong's farmland ecosystems was 531,100 ha a−1, which was in a carbon surplus. Carbon surplus and footprint showed a decreasing trend year by year. The paper results provide a theoretical basis for the formulation of carbon emission reduction policies and industrial restructuring in Guangdong and provinces with the same industrial structure. [ABSTRACT FROM AUTHOR]

The rapid development of tourism in China has also caused a lot of energy consumption and serious environmental problems. In the context of sustainable development, low-carbon tourism has become the consensus of management departments, relevant industries, and academia. In environmental-related fields, DEA is considered as an excellent efficiency analysis tool because of its powerful optimization ability. The final variable of DEA method is weight. In order to avoid the influence of human factors with predetermined weights in tourism analysis, this paper studies the evaluation of tourism ecological efficiency based on DEA model. China's overall tourism ecological efficiency showed a fluctuating upward trend, rising from 0.853 in 2018 to 0.906 in 2021. The national average efficiency over the past four years is 0.855, which is at a low level, indicating that the construction of tourism ecology is still in its infancy, and there is still much room for improvement in the future. As the tourism industry system involves many aspects, such as natural ecology, humanities, economy, and so on, it is an extremely complex system. The research on the ecological efficiency of tourism cannot simply rely on the knowledge system and thinking of a single discipline. Therefore, combined with the relevant theories and knowledge of tourism, management, industrial economics, regional economics, industrial ecology, and other disciplines, this paper makes a systematic study on the problems and countermeasures of Qiaozhai. [ABSTRACT FROM AUTHOR]

To achieve carbon peak targets, realize carbon neutrality vision, and tackle global climate change, China must improve the carbon emission performance at the city level. Based on the carbon emission performance of 191 prefecture-level cities in China from 1997 to 2017, this paper analyses the evolution characteristics of urban carbon emission performance from three aspects: the overall spatial and temporal evolution, the differences according to both region and city size, and the differences among clusters categorized by carbon emission performance at the city level. This paper also reveals the impact of the social and economic transition on China's carbon emission performance. The results show that: (1) The overall level of carbon emission performance of Chinese cities is low, and there is a downward trend during the study period. The differences in carbon emission performance among cities are convergent, but there is a wide gap between high and low values. (2) The carbon emission performance of cities in eastern coastal areas is higher than that in non-coastal areas cities. Large urban agglomerations and economically developed regions, such as provincial capitals, are the agglomeration areas of high urban carbon emission performance values. (3) The carbon emission performance level of cities with similar sizes will converge. At the same time, such changes will enhance the differences among carbon emission performances at the city level within the same region. (4) Cities that belong to high urban carbon emission performance clusters are mainly distributed in the eastern region. Such cities are classified into large cities, supercities, and megacities. Compared with low urban carbon emission performance clusters, cities in high urban carbon emission performance clusters show a higher proportion in the medium-high level and high level of carbon emission performance. Moreover, cities in high urban carbon emission performance clusters are more likely to improve theirurban carbon emission performance. (5) The economic agglomeration effect, industrial structure adjustment and carbon intensity reduction have a significant impact on improving urban carbon emission performance. Population agglomeration has an incremental effect, and the anticipated benefits of environmental regulation have yet to be fully realized. The impacts of different clusters and different regions are variable. Finally, this paper advances policy enlightenment according to its research findings. [ABSTRACT FROM AUTHOR]

China's largest high-latitude permafrost distribution zone is in Northeast China. With the intensification of global warming and engineering construction, the carbon stored in permafrost will gradually thaw and be released in the form of methane gas. However, research on the changes in methane concentration and emission sources in this area is still unclear. In this paper, the AIRS (Atmospheric Infrared Sounder) data carried by the Aqua satellite were used to analyze the distribution and change trends in the overall methane concentration in the near-surface troposphere in Northeast China from 2003 to 2022. These data, combined with national meteorological and on-site monitoring data, were used to study the methane emission characteristics and sources in the permafrost area in Northeast China. The results show that the methane concentration in the near-surface troposphere of Northeast China is mainly concentrated in the permafrost area of the Da and Xiao Xing'an Mountains. From 2003 to 2022, the methane concentration in the near-surface troposphere of the permafrost area in Northeast China showed a rapid growth trend, with an average linear trend growth rate of 4.787 ppbv/a. In addition, the methane concentration in the near-surface troposphere of the permafrost area shows a significant bimodal seasonal variation pattern. The first peak appears in summer (June–August), with its maximum value appearing in August, and the second peak appears in winter (December–February), with its maximum value appearing in December. Combined with ground surface methane concentration monitoring, it was found that the maximum annual ground surface methane concentration in degraded permafrost areas occurred in spring, causing the maximum average growth rate in methane concentration, also in spring, in the near-surface troposphere of permafrost areas in Northeast China (with an average value of 6.05 ppbv/a). The growth rate of methane concentration in the southern permafrost degradation zone is higher than that in the northern permafrost stable zone. In addition, with the degradation of permafrost, the geological methane stored deep underground (methane hydrate, coal seam, etc., mainly derived from the accumulation of ancient microbial origin) in the frozen layer will become an important source of near-surface troposphere methane in the permafrost degradation area. Due to the influence of high-permeability channels after permafrost degradation, the release rate of methane gas in spring is faster than predicted, and the growth rate of methane concentration in the near-surface troposphere of permafrost areas can be increased by more than twice. These conclusions can provide a data supplement for the study of the carbon cycle in permafrost areas in Northeast China. [ABSTRACT FROM AUTHOR]

Land use and land cover (LULC) change has greatly altered ecosystem carbon storage and exerted an enormous impact on terrestrial carbon cycling. Characterizing its impact on ecosystem carbon storage is critical to balance regional carbon budgets and make land use decisions. However, due to the availability of LULC data and the strong variability in LULC change, uncertainty remains high in quantifying the effect of LULC change on the historical and future carbon stock. Based on four historical LULC maps and one future LULC projection, this study combined the Land Use and Carbon Scenario Simulator (LUCAS) with a process-based CENTURY model to evaluate the historical and future LULC change and its impact on grassland carbon storage from 1991 to 2050 in northern China. Results showed that grassland experienced a drastic decrease of 16.10 × 103 km2 before 2005, while agriculture and barren land increased by 16.91 × 103 km2 and 3.73 × 103 km2, respectively. After that, grassland was projected to increase, agriculture kept steady, and barren land decreased. LULC change has resulted in enormous total ecosystem carbon loss, mainly in agro-pasture areas; the maximum 8.54% of carbon loss happened in 2000, which was primarily attributed to agriculture to grassland, forest to grassland, grassland to agriculture, and grassland to barren. Before 2000, the grassland net biome productivity was projected to be −15.54 Tg C/yr and −2.69 Tg C/yr with and without LULC change. After 2001, the LULC change showed a positive impact on the grassland carbon balance, and the region was projected to be a carbon sink. Ecological projects have made a significant contribution to grassland carbon storage. The paper provides a framework to account for the effects of LULC change on ecosystem carbon and highlights the importance of improving grassland management in balancing the grassland carbon budget, which is helpful to understand the regional carbon budget and better inform local land use strategies. [ABSTRACT FROM AUTHOR]

Global climate change caused by greenhouse gas emissions has a direct impact on the sustainable development of human society and has gained widespread concern globally. Biological carbon sequestration measures, mainly forests, are conducive to improving the ecological carbon sink capacity and play an important role in mitigating global climate change. Therefore, assessing the efficiency of forest carbon storage (FCS) is key. In view of the lack of evaluation methods for forest carbon storage efficiency (FCSE) on a large spatial scale and long time series, a method based on Data Envelopment Analysis (DEA) was proposed in this paper. The FCS was calculated using the forest storage expansion method, and the FCSE was calculated using the DEA-Malmquist index to solve the dynamic balance between regional forestry economic input and carbon storage output efficiency. The FCSE in Chinese provinces was analyzed. The results showed that from 1999 to 2018, China's FCS increased annually, from 7558.34 million tons to 9476.73 million tons, and the spatial distribution pattern of total FCS was always different among regions. The average TFP value of FCSE was 1.089, which proves that the FCSE in China has been on the rise in the past 20 years, but the efficiency growth differed between provinces and was affected by different factors such as technical efficiency and technological progress. [ABSTRACT FROM AUTHOR]