Effects of urbanization and forest type on species composition and diversity,forest characteristics,biomass carbon sink,and their associations in Changchun,Northeast China:implications for urban carbon stock improvement

Differences in forest attributes and carbon sequestration of each organ and layer between broadleaved and conifer forests of central and outer urban areas are not well-defined,hindering the precise management of urban forests and improvement of function.To clarify the effect of two forest types with different urbanization intensities,we determined differences in vegetation composition and diversity,structural traits,and carbon stocks of 152 plots(20 m×20 m)in urban park forests in Changchun,which had the largest green quantity and carbon density effectiveness.We found that 1.1-fold thicker and healthier trees,and 1.6-to 2.0-fold higher,healthier,denser,and more various shrubs but with sparser trees and herbs occurred in the central urban forests(p<0.05)than in the outer forests.The conifer forests exhibited 30–70%obviously higher tree aboveground carbon sequestration(including stem and leaf)and 20%bigger trees,especially in the outer forests(p<0.05).In contrast,1.1-to 1.5-fold higher branch stocks,healthier and more diverse trees were found in broadleaved forests of both the inner and outer forests(p<0.05).Plant size and dominant species had similarly important roles in carbon stock improvement,especially big-sized woody plants and Pinus tabuliformis.In addition,a higher number of deciduous or needle species positively affected the broadleaved forest of the central urban area and conifer forest of the outer urban area,respectively.These findings can be used to guide precise management and accelerate the improvement of urban carbon function in Northeast China in the future.

Multi-scenario Simulation for 2060 and Driving Factors of the Eco-spatial Carbon Sink in the Beibu Gulf Urban Agglomeration, China

Since China announced its goal of becoming carbon-neutral by 2060, carbon neutrality has become a major target in the development of China's urban agglomerations. This study applied the Future Land Use Simulation(FLUS) model to predict the land use pattern of the ecological space of the Beibu Gulf urban agglomeration, in 2060 under ecological priority, agricultural priority and urbanized priority scenarios. The Integrated Valuation of Ecosystem Services and Trade-offs(In VEST) model was employed to analyse the spatial changes in ecological space carbon storage in each scenario from 2020 to 2060. Then, this study used a Geographically Weighted Regression(GWR) model to determine the main driving factors that influence the changes in land carbon sinking capacity. The results of the study can be summarised as follows: firstly, the agricultural and ecological priority scenarios will achieve balanced urban expansion and environmental protection of resources in an ecological space. The urbanized priority scenario will reduce the carbon sinking capacity. Among the simulation scenarios for 2060, carbon storage in the urbanized priority scenario will decrease by 112.26 × 10^(6) t compared with that for 2020 and the average carbon density will decrease by 0.96 kg/m^(2) compared with that for 2020. Carbon storage in the agricultural priority scenario will increase by 84.11 × 10^(6) t, and the average carbon density will decrease by 0.72 kg/m^(2). Carbon storage in the ecological priority scenario will increase by 3.03 × 10^(6) t, and the average carbon density will increase by 0.03 kg/m^(2). Under the premise that the population of the town will increases continuously, the ecological priority development approach may be a wise choice.Secondly, slope, distance to river and elevation are the most important factors that influence the carbon sink pattern of the ecological space in the Beibu Gulf urban agglomeration, followed by GDP, population density, slope direction and distance to traffic infrastructure.At the same time, urban space expansion is the main cause of the changes of this natural factors. Thirdly, the decreasing trend of ecological space is difficult to reverse, so reasonable land use policy to curb the spatial expansion of cities need to be made.

Survey on the Policy Evolution of the International Marine Carbon Sink and Carbon Trading Market

Climate change is currently the biggest environmental challenge facing sustainable development in human society,and an inherent requirement for achieving sustainable development is actively addressing climate change.Under the increasingly strict constraints of climate governance,developed countries such as the United States,European Union countries,and Japan have responded and actively formulated low-carbon development goals and policy measures that are in line with their national conditions.These policies mainly involve various fields such as low-carbon technology,energy conservation and emission reduction,and circular development,with clear policy guidance.In this paper,the evolution of policies on marine carbon sink and carbon trading in developed countries such as the United States and Europe is summarized,providing support for a better understanding of the background of international and domestic policy formulation.

Survey on the Policy Evolution of China s Marine Carbon Sink and Carbon Trading Market

Climate change is currently the biggest environmental challenge facing sustainable development in human society,and it is an inherent requirement for achieving sustainable development by actively addressing climate change.Under the increasingly strict constraints of climate governance,developed countries such as the United States,European Union countries,and Japan have responded and actively formulated low-carbon development goals and policy measures that are in line with their national conditions.These policies mainly involve various fields such as low-carbon technology,energy conservation and emission reduction,and circular development,with clear policy guidance.In this paper,the evolution of policies on marine carbon sink and carbon trading in China is summarized,providing support for better understanding the background of formulating relevant international and domestic policies.

Responses of Carbon Sink of Ecosystem Vegetation to Land Use Changes in Kunming City

[Objectives]To analyze the relationship between the land use pattern and the carbon sequestration level of the ecosystem vegetation in Kunming City,and to provide a certain reference for optimizing the land ecological use pattern and scientific carbon reduction and sequestration.[Methods]Based on remote sensing data,meteorological data,vegetation data and soil data,the Carnegie-Ames-Stanford Approach(CASA)was adopted to estimate the vegetation net primary productivity(NPP)in Kunming during 2005-2020,and then the vegetation carbon sink was calculated through the plant mortality model.Besides,it established the land use transfer matrix of Kunming City,and analyzed the change characteristics of the carbon sink of ecosystem vegetation in Kunming City under the influence of land use changes.[Results]During 2005-2020,the water area,construction land and unused land area in Kunming increased by 43.52,710.51 and 2.8 km 2,respectively;farmland,woodland and grassland decreased by 269.72,140.20 and 347.03 km 2,respectively;farmland,woodland,grassland,water area,construction land and unused land caused a total of 58212.72 t of vegetation net carbon sink loss in land conversion,accounting for 14.88%,25.23%,11.95%,10.58%,37.09%,and 0.26%,respectively.[Conclusions]This study is expected to help to improve the ecological carbon sequestration capacity of Kunming and promote the sustainable development of land resources.

Bicarbonate Daily Variations in a Karst River:the Carbon Sink Effect of Subaquatic Vegetation Photosynthesis

Using the Guancun River, an underground stream-fed river, in Rong＇an County of Guangxi, China as a case study, the daily biochemical cycle was examined in this paper based on the data collected a weeklong via high resolution data logger monitoring and high-frequency sampling. Furthermore, the loss of inorganic carbon along its flow path was estimated. Results show that chemical components of the groundwater input are quite stable, showing little change extent; while all of the chemical parameters from two downstream monitoring stations show diel variation over the monitoring period, suggesting that plant activity in the river has a strong influence on water chemistry of the river. The comparison of the input fluxes from the groundwater with the output fluxes of HCO~ estimated at the downstream monitoring station during the high-frequency sampling period shows a strong decrease of HCO~, indicating that the river is losing inorganic carbon along its flow path. The loss is estimated to be about 1,152 mmol/day/m of HCO~ which represent about 94.9 kg/day of inorganic carbon along the 1,350 m section of the Guancun River. It means that HCO~ entering the river from karst underground stream was either consumed by plants or trapped in the authigenic calcite and thus constitutes a natural sink of carbon for the Guancun karst system.

The Variability of Air-sea O_(2)Flux in CMIP6:Implications for Estimating Terrestrial and Oceanic Carbon Sinks

The measurement of atmospheric O_(2)concentrations and related oxygen budget have been used to estimate terrestrial and oceanic carbon uptake.However,a discrepancy remains in assessments of O_(2)exchange between ocean and atmosphere(i.e.air-sea O_(2)flux),which is one of the major contributors to uncertainties in the O_(2)-based estimations of the carbon uptake.Here,we explore the variability of air-sea O_(2)flux with the use of outputs from Coupled Model Intercomparison Project phase 6(CMIP6).The simulated air-sea O_(2)flux exhibits an obvious warming-induced upward trend(~1.49 Tmol yr−2)since the mid-1980s,accompanied by a strong decadal variability dominated by oceanic climate modes.We subsequently revise the O_(2)-based carbon uptakes in response to this changing air-sea O_(2)flux.Our results show that,for the 1990−2000 period,the averaged net ocean and land sinks are 2.10±0.43 and 1.14±0.52 GtC yr−1 respectively,overall consistent with estimates derived by the Global Carbon Project(GCP).An enhanced carbon uptake is found in both land and ocean after year 2000,reflecting the modification of carbon cycle under human activities.Results derived from CMIP5 simulations also investigated in the study allow for comparisons from which we can see the vital importance of oxygen dataset on carbon uptake estimations.

Ecosystem-driven karst carbon cycle and carbon sink effects

It is recognized that karst processes are actively involved in the current global carbon cycle based on twenty years research,and the carbon sink occurred in karst processes is possibly an important part of“missing sink”in global carbon cycle.In this paper,an overview is given on karst carbon cycle research,and influence factors,formed carbon pools(background carbon sink)and sink increase potentials of current karst carbon cycle are analyzed.Carbonate weathering could contribute to the imbalance item(BIM)and land use change item(ELUC)in the global carbon cycle model,owing to its uptake of both atmospheric CO_(2)(carbon sink effect)and CO_(2) produced by soil respiration(carbon source reduction effect).Karst carbon sink includes inorganic carbon sink resulted from hydrogeochemical process and organic carbon sink generated by aquatic photosynthetic DIC conversion,forming relatively stable river(reservoir)water body or sediment carbon sink.The sizes of both sinks are controlled by terrestrial ecosystems and aquatic ecosystems,respectively.Desertification rehabilitation and carbon sequestration by aquatic plants are two effective ways to increase the carbon sink in karst area.It is estimated that the rate of carbon sink is at least 381000 t CO_(2)/a with vegetation restoration and afforestation in southwest China karst area,while the annual organic carbon sink generated by aquatic photosynthesis is about 84200 t C in the Pearl River Basin.The development of a soil CO_(2) based model for assessment of regional dissolution intensity will help to improve the estimation accuracy of carbon sink increase and potential,thus provide a more clear and efficient karst sink increase scheme and pathway to achieve the goals of“double carbon”.With the deep investigation on karst carbon cycle,mechanism and carbon sink effect,and the improvement of watershed carbon sink measurement methods and regional sink increase evaluation approaches.Karst carbon sink is expected to be included in the list of atmospheric CO_(2) sources/sinks of the global carbon budget in the near future.

Division of carbon sink functional areas and path to carbon neutrality in coal mines

Remote sensing image data of typical mining areas in the Loess Plateau from 1986 to 2018 were used to analyze the evolution of land use,explore the division of carbon sink functional areas,and propose carbon neutrality paths to provide a reference for the coal industry carbon peak,carbon-neutral action plan.Results show that(1)land use has changed signifcantly in the Pingshuo mining area over the past 30 years.Damaged land in industrial,opencast,stripping,and dumping areas comprises 4482.5 ha of cultivated land,1648.13 ha of grassland,and 963.49 ha of forestland.(2)The carbon sink functional areas of the Pingshuo mining land is divided into invariant,enhancement,low carbon optimization,and carbon emission control areas.The proportion of carbon sinks in the invariant area is decreasing,whereas the proportion in enhancement,low carbon optimization,and carbon emission control areas is gradually increasing.(3)The carbon neutrality of the mining area must be reduced from the entire process of stripping–mining–transport–disposal–reclamation,and carbon emissions and carbon sink accounting must start from the life cycle of coal resources.Therefore,carbon neutrality in mining areas must follow the 5R principles of reduction,reuse,recycling,redevelopment,and restoration,and attention must be paid to the potential of carbon sinks in ecological protection and restoration projects in the future.

Mechanism of Ecological Compensating and Carbon Sink Trade in Qinghai-Tibet Plateau

The Tibetan, Han and other ethnic people in Tibetan Autonomous Region labored hard to protect the forests and steppes and produce invisible ecological products. The forests and steppes in Qinghai -Tibet Plateau conserved water and added the Jinsha River. In order to achieve sustainable development, it needs to construct compensating mechanism inter Provinces between the upper Yangtze River and the middle and lower Yangtze River, to implement carbon sink trading, and to assist farmers and herdsmen in the Tibet to get rich as soon as possible.

Types of Countryside Carbon Source and Carbon Sink against the Background of Carbon Neutral and Corresponding Strategies

Countryside is rich in large-scale blue and green spaces such as woodland, farmland, grassland and water, which means a great potential of carbon sink. Rural architecture still has a long way to go in terms of low-carbon construction, which makes countryside carbon source and carbon sink significant in researches and practices of realizing objectives of carbon neutral. In view of the problems of current researches on rural carbon source and carbon sink, such as indistinct rural characteristics, incomplete system construction, this paper through sorting out these researches systematically classified the types of countryside carbon source and carbon sink, proposed corresponding strategies, made prospects on researches and practices of countryside carbon source and carbon sink, so as to provide references for future researches.

SWOT Analysis of Forest Carbon Sink Projects in Yunnan Province and Recommendations for Enhancing Competitiveness

Using the SWOT analysis method,this paper analyzed the internal strengths,weaknesses,external opportunities and threats of forest carbon sink projects in Yunnan Province.It found that Yunnan Province has strengths in economic environment and practical experience,weaknesses in social participation,project scale and carbon sink talents,opportunities in international climate environment,domestic policies,etc.,and threats in project crediting period and forest resource protection,etc.In view of these,Yunnan Province can change the participation mode of forest carbon sink projects,adopt appropriate trading methods,get familiar with the relevant rules of forest carbon sink projects,strengthen the publicity and research of forest carbon sink theory,strengthen the management of carbon sink forests and expand forest carbon sink projects to enhance the market competitiveness of the Yunnan forest carbon sink projects.

Important Progress Made in the Study of Chinese Geological Carbon Sink Potential

From 2010 to 2012, geologists at the Institute of Karst Geology the Chinese Academy of Geological Sciences carried out the ＂Chinese Geological Carbon Sink Projects Research＂. They did investigation and research work according to three aspects of carbon sink： karst, soil, and mineral, and achieved important results.

Aged forests could still act as carbon sinks

Old-growth forests are traditionally negligible as carbon sinks, but CAS scientists recently reported that

Effects of organic mineral fertiliser on heavy metal migration and potential carbon sink in soils in a karst region

Heavy metal pollution in karst mountainous area of Guizhou has spread due to the long-term exploitation of mineral resources and the improper disposal of environmentally hazardous waste. Heavy metals are characterised by non-degradation, strong toxicity, and constant accumulation, posing a grave threat to karst mountain fragile soil ecosystem. To reduce the harm caused by heavy metal pollution and damage to agricultural products, research was undertaken on the basis of previous work by simulating pot experiments on pak choi cabbage(Brassica rapa chinensis)planted in Cd-contaminated soil: different amounts of organic mineral fertilisers(OMF) compared with chemical fertiliser(CF) were used and by detecting the amount of heavy metal in the mature vegetable, a better fertilisation strategy was developed. The results showed that the Cd content in vegetables grown with CF was 23.70 mg/kg,while that of vegetables grown with OMF and bacterial inoculant was the lowest at 15.13 mg/kg. This suggests that the use of OMF and microbes in karst areas not only promotes plant growth but also hinders plant absorption of heavy metal ions in the soil. In addition, through the collection of pot leachate, the detection of water chemistrycharacteristics, and the calculation of the calcite saturation index, it was found that the OMF method also induces certain carbon sink effects. The results provide a new way in which rationalise the use of OMFs in karst areas to alleviate soil heavy metal pollution and increase soil carbon sequestration.

Primary Discussion of a Carbon Sink in the Oceans

As a consequence of global warming and rising sea levels, the oceans are becoming a matter of concern for more and more people because these changes will impact the growth of living organisms as well as people's living standards. In particular, it is extremely important that the oceans absorb massive amounts of carbon dioxide. This paper takes a pragmatic approach to analyzing the oceans with respect to the causes of discontinuities in oceanic variables of carbon dioxide sinks. We report on an application of chemical, physical and biological methods to analyze the changes of carbon dioxide in oceans. Based on the relationships among the oceans, land, atmosphere and sediment with respect to carbon dioxide, the foundation of carbon dioxide in shell-building and ocean acidification, the changes in carbon dioxide in the oceans and their impact on climate change, and so on, a vital conclusion can be drawn from this study. Specifically, under the condition that the oceans are not disturbed by external forces, the oceans are a large carbon dioxide sink. The result can also be inferred by the formula: C=A-B and G=E+F when the marine ecosystem can keep a natural balance and the amount of carbon dioxide emission is limited within the carrying capacity of the oceans.

Trends in carbon sink along the Belt and Road in the future under high emission scenario

目前,在区域尺度,NEP趋势变化的强度和影响机制还存在很大的不确定性.针对这一问题,我们选取了一带一路覆盖的区域为研究对象,基于全球陆面模式(CABLE)和第六次国际耦合模式比较计划(CMIP6),评估了历史和未来NEP趋势的变化,分析了影响的机制.从过去到未来,CABLE结果表明NEP的趋势从0.015 Pg C yr^(-2)减少到-0.023 Pg C yr^(-2);CMIP6结果为从0.014 Pg C yr^(-2)转变为-0.009 Pg C yr^(-2).气候变化是引起这一变化的主因.我们的研究结果强调了碳-气候-氮相互作用的重要性,这对碳中和目标下碳汇潜力的准确估算尤为重要.

Feasibility of Haze Governance Based on Carbon Sink Mode

In recent years,there are research findings of haze formation in various fields of academic circle. It has proved that causes of haze take on diverse characteristics. Thus,from both the natural and human perspective,haze governance should be diverse. Research conclusions on causes of haze formation mainly focus on special geographical structure,and meteorological factors such as relatively stable atmosphere,high rate of calm wind,high relative humidity and temperature of air,and human factors such as industrial pollution,automotive exhaust emissions,aerosol pollution,eutrophication of soil water,and change of city underlying surface. Carbon sink mode is a new channel for haze governance.In carbon sink mode,it is feasible to regulate relative humidity and temperature in air,enhance global wind,and reduce fine particles and microorganisms of air pollution,so as to reduce haze pollution. Besides,China's special potential of carbon sink market makes it possible to govern haze on the base of carbon sink.

The Carbon Sinks and Mitigation Potential of Deodar (<i>Cedrus deodara</i>) Forest Ecosystem at Different Altitude in Kumrat Valley, Pakistan

Forest carbon monitoring and reporting are critical for informing global climate change assessment. The regional estimates of forest carbon attached greater attention, to assess the role of forest in carbon mitigation. Here using field inventory, we examined the carbon sink and mitigation potential of monospecific Deodar forest in the Kumrat valley, of Hindu Kush Himalaya, Region of Pakistan, at a different elevation. The elevation of monospecific Deodar forest ranges from 2300 to 2700 m (a.s.l). We divided the forest into three elevation classes (that is 2300 - 2400 m (EI) 2400 - 2500 m (EII) and 2500 - 2700 m (EIII) a.s.l respectively). In each elevation class, we laid out 09 sample plots (33*33 m2) for measuring carbon values in living tree biomass (LT), soil (SC), litter, dead wood, cone (LDWC) and understory vegetation (USV). Our results showed that the carbon density at EI was 432.37 ± 277.96 Mg·C-1, while the carbon density at EII and EIII was 668.35 ± 323.94 and 1016.79 ± 542.99 Mg·C-1 respectively. Our finding revealed that the carbon mitigation potential of the forest increases with increasing elevation. Among the different elevation classes, EIII stored significantly higher carbon due to the dominance of mature, old age, larger trees, and the minimum anthropogenic disturbance, whereas EI stored statistically lower carbon because of maximum anthropogenic disturbance, which resulted in the removal of mature and over-mature trees. Furthermore, our correlation analysis between tree height and carbon stock and basal area and LT carbon, underlines that the basal area is the stronger predictor of LT carbon estimation than height. Overall our results highlight that deodar forest stored 716.94 ± 462.06 Mg?C·ha-1. However, the rehabilitation, preservation and sustainable management of disturb forest located at a lower elevation could considerably improve carbon mitigation potential.

Carbon sink response of terrestrial vegetation ecosystems in the Yangtze River Delta and its driving mechanism

The carbon cycle of terrestrial ecosystems is influenced by global climate change and human activities.Using remote sensing data and land cover products,the spatio-temporal variation characteristics and trends of NEP in the Yangtze River Delta from 2000 to 2020 were analyzed based on the soil respiration model.The driving influences of ecosystem structure evolution,temperature,rainfall,and human activities on NEP were studied.The results show that the NEP shows an overall distribution pattern of high in the southeast and low in the northwest.The area of carbon sinks is larger than that of the carbon sources.NEP spatial heterogeneity is significant.NEP change trend is basically unchanged or significantly better.The future change trend in most areas will be continuous decrease.Compared with temperature,NEP are more sensitive to precipitation.The positive influence of human activities on NEP is mainly observed in north-central Anhui and northern Jiangsu coastal areas,while the negative influence is mainly found in highly urbanized areas.In the process of ecosystem structure,the contribution of unchanged areas to NEP change is greater than that of changed areas.