Carbon Sink Effect Research Articles

A Simulation-Based Prediction of Land Use Change Impacts on Carbon Storage from a Regional Imbalance Perspective: A Case Study of Hunan Province, China

Land use imbalances are a critical driving factor contributing to regional disparities in carbon storage (CS). As a significant component of China’s Yangtze River Economic Belt, Hunan Province has undergone substantial shifts in land use types, resulting in an uneven distribution of ecosystem CS and sequestration capacity. Therefore, within the framework of the “dual carbon” strategy, examining the effects of land use changes driven by regional resource imbalances on CS holds practical importance for advancing regional sustainable development. This study focuses on Hunan Province, utilizing the PLUS-InVEST model to assess the spatiotemporal evolution of CS under land use changes from 1990 to 2020. Additionally, multiple scenario-based development modes were employed to predict county-level CS. The results indicate the following: (1) From 1990 to 2020, Hunan Province experienced continuous urban expansion, with forest land and cultivated land, which are core ecological land types, being converted into construction land. (2) Over these 30 years, the province’s total CS increased by 2.47 × 108 t, with significant spatial differentiation. High-value zones were concentrated in bands along the province’s borders, while lower values were observed in the central and northern regions. The highest CS values were recorded in forested areas at the province’s periphery, whereas the lowest values were observed in the northern water bodies. (3) The scenario-based predictions revealed notable differences, with the ecological protection scenario demonstrating a substantial carbon sink effect. By prioritizing forest and cultivated land, CS could be maximized. This research provides valuable insights for enhancing CS and optimizing land use structures in regions facing resource imbalances.

How does the value of ecological restoration techniques affect ecosystem carbon density: A resource endowment-based perspective

In the context of carbon neutrality and carbon peaks, innovations in ecological restoration technology play a key role in carbon adsorption and maintaining ecological balance. Regional governments, tasked with formulating differentiated and rational ecologically sustainable development plans and carbon-neutral strategies tailored to various resource endowment conditions, require timely identification of the mechanisms by which ecological restoration technologies affect the carbon density of ecosystems. Based on data from 31 provinces in China from 2006 to 2021, this study employed the Spatial Durbin Model with both time and space fixed effects to examine the impact of the value of ecological restoration technologies on ecosystem carbon density under varying resource endowments. The empirical results indicate that (1) the value of ecological restoration technology has a significantly positive effect on ecosystem carbon density, particularly in neighbouring areas; (2) energy resource endowment exhibits a significantly inverted U-shaped boundary effect, whereby regions with moderate energy endowment can optimise the positive impact of ecological restoration technology; (3) the heterogeneity analysis, based on levels of regional environmental governance and forest cover, shows that in regions with less investment in environmental infrastructure and lower forest cover, ecosystem carbon density is more sensitive to the value of ecological restoration techniques, making their carbon sink effect more pronounced. This study elucidates the key role of ecological restoration techniques in enhancing carbon storage, promoting the goal of carbon neutrality, and identifying optimal pathways for increasing ecosystem carbon stocks across various regions with differing resource endowments. Moreover, it provides a reference for accelerating the achievement of carbon neutrality targets.

Estimation and Spatial Distribution of Individual Tree Aboveground Biomass in a Chinese Fir Plantation in the Dabieshan Mountains of Western Anhui, China

Understanding aboveground biomass (AGB) and its spatial distribution is key to evaluating the productivity and carbon sink effect of forest ecosystems. In this study, a 123-year-old Chinese fir forest in the Dabieshan Mountains of western Anhui Province was used as the research subject. Using AGB data calculated from field measurements of individual Chinese fir trees (diameter at breast height [DBH] and height) and spectral vegetation indices derived from unmanned aerial vehicle (UAV) remote sensing images, a random forest regression model was developed to predict individual tree AGB. This model was then used to estimate the AGB of individual Chinese fir trees. Combined with digital elevation model (DEM) data, the effects of topographic factors on the spatial distribution of AGB were analyzed. We found that remote sensing spectral vegetation indices obtained by UAVs can be used to predict the AGB of individual Chinese fir trees, with the normalized difference vegetation index (NDVI) and the optimized soil-adjusted vegetation index (OSAVI) being two important predictors. The estimated AGB of individual Chinese fir trees was 339.34 Mg·ha−1 with a coefficient of variation of 23.21%. At the local scale, under the influence of elevation, slope, and aspect, the AGB of individual Chinese fir trees showed a distribution pattern of decreasing from the middle to the northwest and southeast along the northeast-southwest trend. The effect of elevation on AGB was influenced by slope and aspect; AGB on steep slopes was higher than on gentle slopes, and the impact of slope on AGB was influenced by aspect. Additionally, AGB on north-facing slopes was higher than on south-facing slopes. Our results suggest that local environmental factors such as elevation, slope, and aspect should be considered in future Chinese fir plantation management and carbon sink assessments in the Dabieshan Mountains of western Anhui, China.

Prospects for the potential carbon sink effects of afforestation to enhance weathering in China

Prospects for the potential carbon sink effects of afforestation to enhance weathering in China

Influence of Biomass Amendments on Soil CO2 Concentration and Carbon Emission Flux in a Subtropical Karst Ecosystem

Soil in karst areas is rare and precious, and karst carbon sinks play an important role in the global carbon cycle. Therefore, the purpose of karst soil improvement is to improve soil productivity and a carbon sink effect. Biomass amendment experiments in this study included three schemes: filter mud (FM), filter mud + straw + biogas slurry (FSB), and filter mud + straw + cow manure (FSC). The characteristics of soil CO2 production, transport, and the effect on soil respiration carbon emissions in two years were compared and analyzed. The results were as follows: 1. The rate, amount, and depth of CO2 concentration were affected by the combinations with biogas slurry (easy to leach) or cow manure (difficult to decompose). 2. The diurnal variation curves of soil respiration in the FSB- and FSC-improved soils lagged behind those in the control soil for three hours. While the curves of FM-improved soil and the control soil were nearly the same. 3. Soil–air carbon emissions increased by 35.2 tCO2/(km2·a−1) under the FM scheme, decreased by 212.9 tCO2/(km2·a−1) under the FSB scheme, and increased by 279.5 tCO2/(km2·a−1) under the FSC scheme. The results were related to weather CO2 accumulation in the deep or surface layers under different schemes.

A potential CO2 carrier to improve the utilization of HCO3– by plant-soil ecosystem for carbon sink enhancement

IntroductionImproving the rhizospheric HCO3– utilization of plant-soil ecosystem could increase the carbon sink effect of terrestrial ecosystem. However, to avoid its physiological stress on the crop growth, the dosage of HCO3– allowed to add into the rhizosphere soil was always low (i.e., <5–20 mol/m3). ObjectivesTo facilitate the utilization of relatively high concentrations of HCO3– by plants in the pursuit of achieving terrestrial carbon sink enhancement. MethodsIn this study, the feasibility of directly supplementing a high concentration HCO3– carried by the biogas slurry to the plant rhizosphere was investigated using the tomato as a model plant. ResultsThe CO2-rich biogas slurry was verified as a potential CO2 carrier to increase the rhizospheric HCO3– concentration to 36 mol/m3 without causing a physiological stress. About 88.3 % of HCO3– carried by biogas slurry was successfully fixed by tomato-soil ecosystem, in which 43.8 % of HCO3– was assimilated by tomato roots for the metabolism, 0.5 ‰ of HCO3– was used by microorganisms for substances synthesis of cell structure through dark fixation, and 44.4 % of HCO3– was retained in the soil. The rest of HCO3– (∼11.7 %) might escape into the atmosphere through the reaction with H+. Correspondingly, the carbon fixation of tomato-soil ecosystem increased by 150.1 g-CO2/m2-soil during a tomato growth cycle. As for the global countries that would adopt the strategy proposed in this study to cultivate the tomato, an extra carbon sink of soil with about 1031.1 kt-C per year (i.e., an additional 0.21 tons of carbon per hectare soil) could be obtained. ConclusionThis would be consistent with the goal of soil carbon sink enhancement launched at COP21. Furthermore, the regions with low GDP per capita may easily achieve a high reduction potential of CO2 emissions from the agricultural land after adopting the irrigation of CO2-rich biogas slurry.

Spatial and temporal divergence and driving mechanisms of carbon sinks in terrestrial ecosystems in the middle reaches of the Yangtze River urban agglomerations during 2008–2020

Urban cluster carbon sinks are key parts of the terrestrial carbon cycle, and play an important role in global climate change. Based on the inversion results of net ecosystem productivity (NEP) in Middle Reaches of the Yangtze River Urban Agglomeration (MRYRUA), this study considered the influence of both natural environmental and socioeconomic factors on NEP, and investigated the driving mechanism of carbon sink emphasizing spatial and temporal heterogeneity by the geographically and temporally weighted regression model (GTWR). Results demonstrated that (1) During 2008–2020, the annual average NEP was positive in MRYRUA, and the carbon sink effect of terrestrial ecosystem increased. (2) In MRYRUA, Precipitation and DEM were positively correlated with carbon sinks, opposite for temperature, percentage of water areas and population density. (3) During the study period, the influence of natural environmental factors, such as temperature and precipitation on NEP grew gradually weaker, whereas that of socioeconomic factors increased. The influence of urbanization rate, night lights index and factors of industrial structure changed from negative to positive, while percentage of built-up area had an increasing negative effect on NEP. Based on the conclusions above, this study proposed differentiated policy implications, including improving vegetation hydrothermal environment, controlling urban expansion and accelerating industrial transformation. It would provide empirical inspiration for attaining peak carbon, carbon neutrality, and sustainable development goals.

Response of weathering carbon sink effect to anthropogenic sulfuric acid in different lithological catchments: A case study from Southwest China

Accurately quantifying the carbon sink effect resulting from chemical weathering caused by anthropogenic H2SO4 is imperative to improve the assessment of the global carbon budget. Nevertheless, there is still a lack of precise understanding regarding the impact of anthropogenic H2SO4 on CO2 consumption during chemical weathering. Here, spring water samples were collected monthly from three catchments with distinct bedrock lithologies affected by severe acid precipitation in Southwest China for analyses of hydrogeochemistry and δ13CDIC to quantitatively estimate the effect of anthropogenic H2SO4 on the weathering carbon sink budget. The results show that carbonates contribute 97.4 %, 95.0 % and 88.8 % of the total cationic load using a straightforward method in the Beidiping carbonate catchment, as well as in the Shegengyan and Bianyan silicate catchments, respectively. The [Ca2++Mg2+]/[HCO3−] (0.98–1.19) and [Ca2++Mg2+]/[HCO3−+SO42−] (approximately 1) equivalent ratios, and δ13CDIC values (−16.8 to −8.0 ‰) of the samples suggest that besides H2CO3, H2SO4 is involved in carbonate weathering. The stoichiometry of the chemical compositions of spring water indicates that the presence of H2SO4 enhances carbonate weathering rates by 14.8 %, 8.1 % and 7.5 % while decreasing the CO2 consumption by 8.2 %, 4.3 % and 4.0 % in Beidiping, Shegengyan and Bianyan, respectively. Thus the reduced proportion of karst carbon sink in the carbonate catchment is approximately 2 times that in the silicate catchment, suggesting that carbonate weathering in the karst catchment is more sensitive to acid precipitation. The impact of acid precipitation on rock weathering in the silicate catchment is constrained by the soil buffering effect. Our study highlights the important role of anthropogenic H2SO4 in carbonate weathering, which should be critically evaluated in regional and global carbon cycles in future studies.

Carbon Sink Effect of Plateau Grassland and Contribution of Carbon Cycle

This paper reviews the research progress of plateau grassland carbon sink effect and its contribution and role to global carbon cycle. The paper also evaluates the size and change of plateau grassland carbon sink effect, and reveals its spatiotemporal distribution and dynamic characteristics. The paper discusses the relationship between plateau grassland carbon sink effect and global carbon cycle, and elucidates its role and significance in contributing to global carbon balance, mitigating global climate change, and protecting global biodiversity. The paper analyzes the positive and negative effects and interactions of climate change, human activities, grassland type and management on plateau grassland carbon sink effect, and proposes the influencing mechanism and mode of plateau grassland carbon sink effect. The paper points out the difficulties and shortcomings of the research on plateau grassland carbon sink effect, and puts forward some suggestions and prospects for future research. The paper aims to provide reference and inspiration for deepening the understanding of the internal mechanism and external influence of plateau grassland carbon sink effect, and for formulating effective grassland protection and management measures.

Analysis of Dynamic Evolution and Driving Factors of Low-Carbon Utilization Efficiency of Cultivated Land in China

In order to cope with global climate warming, measurement of the low-carbon utilization efficiency (LCUE) of cultivated land, considering carbon sink and carbon emission effects, is proposed. To address this, based on the data of 30 provinces in China, this study conducts a LCUE evaluation system by the MinDS-U-M productivity index model in order to analyze the spatiotemporal patterns and driving factors of LCUE with the geographic detector model and GTWR model. The results show the following: (1) Over the past 20 years, the average LCUE value exhibits a slow increasing trend from 2001 to 2021, which ranges from 0.9864 to 1.0272. Provinces with mid-level LCUE ranging from 1.0000 to 1.0990 account for the highest proportion in each period. (2) The annual growth rate of LCUE in the central region is the highest, where the promotion of green technology and farmland protection policies have played important roles. (3) According to the Geodetector analysis, urbanization rate (UR), irrigation index (IR), grain output value (GOV), precipitation (PR), arable land area (ALA), and environmental pollution control (EPC) are important drivers of the spatial difference of LCUE. (4) The GTWR model shows that the positive effects of ALA and SRT have always been concentrated in the main grain-producing areas over time. UR and PR have strong explanatory power for the space/time differentiation of LCUE, especially in eastern coastal regions. IR has an increasing effect on LCUE in the Western region, and the positive effect of EPC on the LCUE is concentrated in the central region. In order to coordinate regional LCUE contradictions, it is suggested to be wary of land resource damage caused by economic development, warn about the impacts of climate change, and strengthen the supervision of land remediation projects in order to achieve sustainable land management.

Analysis of regional differences and spatial and temporal evolution of tourism carbon emissions in China: considering carbon sink effect

ABSTRACT The purpose of this study is to analyze the regional differences and spatial-temporal evolutionary characteristics of carbon dioxide emissions of tourism in China during 2001–2022 from the perspective of carbon sink effect by using an econometric modeling approach. The findings show that CO2 emissions from China's tourism industry exhibit non-equilibrium spatial characteristics or non-linear relationships. Secondly, the results of Theil's index show that the intra-regional differences in tourism CO2 emissions are greater than the inter-regional differences and exhibit a gradient of ‘West > Central > East’. Finally, under the condition of considering the existence of spatial regional heterogeneity, it is found that tourism CO2 emissions have significant spatial agglomeration, with high CO2 emission regions primarily clustered within the eastern region and the economically developed regions, and low CO2 emission regions distributed centrally within the central region and less developed areas of the tourism economy. It is worth noting that the intra-regional differences mainly come from the eastern belt, and that there are large regional differences in tourism CO2 emissions within the eastern region, while the western region is the next largest and the central region the smallest.

Spatiotemporal patterns of net regional productivity and its causes throughout Ordos, China.

A comprehensive understanding of the terrestrial carbon sink is essential for proficient regional carbon management. However, previous studies predominantly relied on net ecosystem productivity (NEP) as an indicator of regional carbon sink, overlooking the impacts of carbon emissions from physical processes and carbon leakage associated with anthropogenic activities. In this study, net region productivity (NRP), a vital metric representing carbon sink dynamics in regional multi-landscape ecosystems, was employed to systematically analyze the patterns, trends, and causes of carbon sink in Ordos. The results revealed that spatially averaged NRP in Ordos was 70.334 g·m-2·a-1, indicating a carbon sink effect. The coefficient of variation of NRP was 68.035%, with a higher NRP in the southern region. Normalized difference vegetation index (NDVI) predominantly controlled the spatial heterogeneity of NRP in Ordos, while precipitation emerged as the primary climatic factor influencing spatial differences in NRP. Regional variations in the impact of environmental factors on NRP were evident. In most areas, NRP showed a notable increasing trend influenced by various factors. Specifically, the simultaneous rise in NDVI and improvements in hydrothermal conditions contributed to the gradual elevation of NRP, each with varying degrees of influence across Ordos and its sub-regions.

Heading towards carbon neutrality: how do marine carbon sinks serve as important handle for promoting marine ecological civilization construction?

As an efficient long-term carbon sink, marine carbon sinks and the associated carbon sink effects, technology, accounting and trading market construction warrant investigation across various disciplines. However, information on the interrelationships and their development over time with respect to the research conducted in China is limited, affecting the ability to drive research directions and optimize continued advancement in this field. Therefore, in this study, we aimed to understand the current situation of marine carbon sink research in China to promote a deeper level of scientific development based on the research literature related to marine blue carbon sinks in the core databases of the China National Knowledge Internet (CNKI) and Web of Science (WOS). We used bibliometric tools in the Citespace software to quantitatively compare and analyse the main characteristics of marine blue carbon sink research including publication volume, time, journals, authors and institutions. We also explored the popular research topics, frontier areas, and theme evolution trends through keyword clustering and emergent and co-occurring knowledge maps. The key recommended research directions for ocean carbon sinks are: (1) to promote the unified carbon sink market research of land and sea integration through multidisciplinary and cross-disciplinary research; (2) to achieve new breakthroughs in ocean carbon sinks with the support of coastal wetlands and seawater offshore aquaculture environments; (3) to explore the protection provided by ocean carbon sinks with a comprehensive eco-compensation mechanism; (4) to improve the application of marine carbon sinks by taking the theory and technological innovation research related to marine carbon sinks as the guide. Ultimately, our work helps characterise the current situation of marine carbon sink research, promote the research in this field to a deeper level of development and provide reference for subsequent scholars to carry out related research.

The Chemical Weathering of Rocks and Its Carbon Sink Effect in the Naqu River Basin of the Nujiang River Source Area, Southwest China

Carbon plays an important role in global climate change. The mechanisms of carbon sources and carbon sinks have also received wide attention from society, and the physical and chemical characteristics of riverine ions can reflect the chemical weathering of rocks and carbon sink capacity of river basins. Based on the data on river, rainwater, and rock samples from 2019, this study used various methods, such as ion ratio diagrams and ternary diagrams, to analyze the chemical characteristics of water; the chemical weathering and carbon sink effects of rocks were also calculated while assuming three scenarios based on the main sources of ions in the Naqu River. The results showed that for the whole catchment, the main ion sources in the river were: carbonate rock chemical weathering &gt; silicate rock chemical weathering &gt; evaporite dissolution &gt; atmospheric precipitation input. According to the calculations, in the three scenarios, the carbonate weathering rates were 16.84, 11.32, and 14.08 t/km2/yr, and the carbon sink capacities were 66.47, 121.13, and 93.80 mol/km2/yr, respectively; the evaporite weathering rates were 2.20, 9.63, and 5.92 t/km2/yr, respectively. The silicate chemical weathering rate and carbon sink capacity did not change significantly in either scenario, with 6.82 t/km2/yr and 248.6 mol/km2/yr, respectively. This study quantified the ion sources in the Naqu River basin and accurately analyzed their chemical genesis, which helps in understanding the role of the rivers of the Qinghai–Tibet Plateau in the global carbon cycle and global climate change, in addition to providing a reference for the scientific development of the Nujing River.

The impact of non-grain conversion of cultivated land on the relationship between agricultural carbon supply and demand

Increasing carbon sinks and reducing emissions in agricultural system is important for global sustainable development. Affected by the increasing cost and the declining profit of grain planting in China, the overall agricultural planting structure in the Northwest region showed a trend of conversion to non-grain crops. However, the impact of the non-grain conversion of cultivated land on agricultural carbon supply and demand is unclear. Therefore, taking Gansu Province as an example, this paper constructed a theoretical framework for the impact of non-grain conversion on agricultural carbon supply and demand, and empirically tests the relationship between non-grain conversion and carbon supply and demand index using a two-way fixed effects model based on statistical panel data from 2000 to 2020. The study found that the proportion of non-grain crop planting areas in the Gansu Province increased from 24.88% to 32.90% from 2000 to 2020. The proportion of non-grained medium and high value areas increased significantly and spread from a localized to a province-wide influence. In the past 21 years, the total agricultural carbon absorption showed an inverted “N” type downward development trend and was greatly affected by the carbon absorption of grain crops (especially wheat, corn), while the total agricultural carbon emission showed an “N” type upward trend and was greatly affected by the carbon emissions of non-grain crops (especially vegetables). The increase in the area of non-grain crops weakened the carbon sink effect of farmland and intensified its carbon source properties, resulting in a decrease in the carbon supply-demand index (SDIC) from 0.187 to 0.023. The rate of non-grained level (NGL) is significantly negatively correlated with the SDIC, and that for every 1% increase in the NGL, the SDIC will decrease by 0.728%. Based on this, policy recommendations for optimizing planting structures and agricultural practices are proposed with a view to providing theoretical support for achieving a win-win situation for food security and ecological safety in Gansu Province.

Dissolved inorganic carbon budget of two alpine catchments in the central Tibetan Plateau: Glaciation matters

Dissolved inorganic carbon (DIC) fluxes account for over one-third of the total carbon transported in most rivers. The DIC budget for glacial meltwater of the Tibetan Plateau (TP), however, is still poorly understood, despite the fact, the TP has the largest glacier distribution outside of the Poles. In this study, the Niyaqu and Qugaqie catchments in the central TP were selected to examine the influence of glaciation on the DIC budget in vertical evasion (CO2 exchange rate at the water-air interface) and lateral transport (sources and fluxes) from 2016 to 2018. Significant seasonal variation in DIC concentration was found in the glaciated Qugaqie catchment, but was absent in the not glaciated Niyaqu catchment. δ13CDIC showed seasonal changes for both catchments, with more depleted signatures during the monsoon season. The average CO2 exchange rates in river water of Qugaqie were ~8 times lower compared to Niyaqu with values of −1294.6 ± 438.58 mg/m2/h and −163.4 ± 581.2 mg/m2/h, respectively, indicating that proglacial rivers can act as a substantial CO2 sink due to CO2 consumption by chemical weathering. DIC sources were quantified via the MixSIAR model using δ13CDIC and ionic ratios. During the monsoon season, the contribution from carbonate/silicate weathering driven by atmospheric CO2 was 13–15 % lower, while biogenic CO2 involved in chemical weathering was 9–15 % higher, indicating a seasonal control on weathering agents. Carbonate dissolution driven by H2SO4/HNO3 was the most important contributor to DIC in both catchments (40.7 ± 2.2 % in Niyaqu and 48.5 ± 3.1 % in Qugaqie). The net CO2 consumption rate in the not glaciated Niyaqu catchment was close to 0 (−0.07 ± 0.04 × 105 mol/km2/y), indicating the carbon sink effect caused by chemical weathering in this area was weak. The net CO2 consumption rate in the glaciated Qugaqie catchment, however, was much lower than that in the not glaciated catchment with a value of −0.28 ± 0.05 × 105 mol/km2/y. This study highlights that chemical weathering in small glaciated catchments of the central TP plays an active role in releasing CO2 to the atmosphere.

Migration of dissolved carbon on bare karst slopes in soil in response to natural rainfall events

Soil carbon in karst critical zones is an essential part of the global carbon pool, and the migration of dissolved carbon is a vital component of the carbon cycle in such regions. The unique “dual hydrological structure” makes the path and process of migration of soil dissolved carbon driven by rainfall unclear in karst slopes, which ultimately hinders the accurate evaluation of the carbon sink effect in such regions. Therefore, based on field monitoring of natural rainfall, this study evaluated the process and characteristics of the spatial migration of soil dissolved carbon in bare karst slopes and its response to natural rainfall (rainfall duration and amount). The results showed that the concentration of dissolved carbon transported in surface runoff was significantly lower than that transported within the soil layer; however, carbon loss displayed the opposite trend. Rainfall factors (rainfall amount and duration) and runoff volume significantly affected soil dissolved carbon, contributing 46.91% to soil dissolved carbon. Rainfall factors significantly affect soil dissolved carbon migration by influencing runoff. In addition, the hydrological path is an important factor affecting soil dissolved carbon transport. Our study shows that the soil and bedrock interface (SBI) and shallow karst fissures (SKF) are the main routes of dissolved carbon migration in soils in bare karst slopes. Dissolved carbon migrating along SKF is a vital contributor to the “missing carbon sink” in karst regions, and dissolved carbon migrating along the SBI is potentially an important contributor to the “missing carbon sink.” This study provides primary data and is expected to serve as a reference for revealing the mechanism of karst carbon migration and transformation and accurately evaluating the carbon sink effect in karst areas.

Study on Effects of Land Use Change on Carbon Emissions in Beijing Tianjin Hebei region from 1990 to 2020

In order to deeply understand the impact of land use types on carbon effect, we choose the Beijing Tianjin Hebei region as the study area. By using the IPCC calculation method and the modified carbon emission calculation model, our paper estimates the carbon source and carbon sink effects of change in land use type in Hebei, Beijing and Tianjin from 1990 to 2020, and analyzes their temporal and spatial changes. The results show that: (1) Development of some factories has gradually shifted to Hebei, so its land area for industrial development has increased. The corresponding total energy consumption has also increased. (2) Construction land is the primary carbon source. The region is in the golden stage of urban construction and industrial development, and the regional infrastructure land will increase accordingly. The construction land will maintain a high growth trend over a long period. (3) Total carbon dioxide in this study area is increasing, and the massive carbon dioxide emissions of change in land use type is far greater than the amount of carbon dioxide absorbed.

Carbon Sequestration Characteristics Under Natural Vegetation Restoration in Ziwuling Area of the Loess Plateau

The aim of this study was to analyze the carbon sink effect under natural vegetation restoration and the influence of changes in vegetation community characteristics on ecosystem carbon density in ecologically fragile areas of the Loess Plateau. In this study, the changes in carbon sequestration of a vegetation-soil system under eight successional stages[slope cropland, abandoned cropland for 10 years, abandoned cropland for 20 years, Sophora davidii (Franch.) Skeels., Betula platyphylla Suk., Pinus tabulaeformis Carr., Quercus wutaishanic Mary+P. tabulaeformis Carr mixed forests, and Q. wutaishanic Mary] in Ziwuling area over 150 restoration periods were investigated using the common method of spatial and temporal substitution. This study also discussed the relationship between changes in vegetation community characteristics and vegetation-soil system carbon density. The results showed that the community coverage of the investigated vegetation fluctuated from 85% in the slope cropland stage to 100% in the arbor stage. The number of species, Margalef index, Shannon-Wiener index, Pielou index, and Simpson index initially increased rapidly, then declined slowly until becoming stable, and reached a peak in the middle of the succession (B. platyphylla Suk.). The biomass and carbon density of vegetation components (above-ground biomass, below-ground roots, and litter) increased exponentially during the succession, i.e., increased slowly before B. platyphylla Suk. but increased significantly in B. platyphylla Suk. and P. tabulaeformis Carr.(P<0.05). The biomass and carbon density reached the maximum values of 27858.08 g·m-2 and 13232.51 g·m-2, respectively, in Q. wutaishanic Mary+P. tabulaeformis Carr mixed forests and tended to be stable in the late succession stage. Soil organic carbon density showed a power function relationship with vegetation restoration, with the greatest increase in the stages of abandoned cropland for 10 years and B. platyphylla, but no significant changes in the subsequent stages (P>0.05). In the early succession stage, the carbon density of the farmland ecosystem was the lowest (4395.70 g·m-2), whereas the other seven stages increased by 55.54%, 40.37%, 69.96%, 202.48%, 326.35%, 357.43%, and 351.07%, respectively, compared with the farmland ecosystem. Community coverage, Margalef index, Shannon-Wiener index, above-ground biomass, root biomass, and litter biomass were significantly positively correlated with vegetation-soil system carbon density (P<0.05). The carbon sink effect of long-term natural restoration in Ziwuling Region was significant, and the carbon density of the vegetation-soil system under interspecific competition tended to be stable in the late succession stage. Dynamic changes in the vegetation community structure and plant diversity during the succession process increased vegetation carbon density and soil carbon density. This study helps to clarify the carbon sink effect of natural vegetation restoration in ecologically fragile areas of the Loess Plateau and provides a theoretical basis for promoting natural forest conservation and achieving carbon neutrality.

Assessing the Spatio-Temporal Dynamics of Land Use Carbon Emissions and Multiple Driving Factors in the Guanzhong Area of Shaanxi Province

Land use change is one of the key elements leading to carbon emission changes, and is of great significance to the process of achieving the goals of carbon peaking and carbon neutrality. In this study, we calculated the land-use carbon emissions (LCE) in the Guanzhong area (GZA) of Shaanxi province from 2000 to 2019 by using an improved LCE measurement model. Meanwhile, the spatial and temporal changes of LCE were analyzed and the driving forces were investigated based on the correlation analysis and multi-scale geographical weighting regression (MGWR). The results showed that the total amount of LCE showed a significant increasing trend from 2000 to 2019. Regions where the LCE significantly increased occupied 71.20% of the total area; these regions were distributed in the central and eastern parts of the study area. The LCE showed a significant positive spatial correlation and had a remarkable aggregation state. The H-H agglomeration area of LCE was distributed in the central urban agglomeration. The L-L agglomeration areas were always distributed in the southwest part of the GZA with low carbon emissions. The average correlation coefficients between LCE and nighttime light (NTL), population density (PD), and gross primary productivity (GPP) were 0.13, 0.21, and −0.05, respectively. The NLT and PD had obvious positive effects on LCE, while GPP has obvious negative effects on carbon emissions, which can be ascribed to the carbon sink effect of forests and grasslands. The results of this study have important reference value regarding the formulation of carbon emission reduction policies and the development of a low-carbon social economy.