SOME FEATURES OF CARBON CYCLES IN KARST SYSTEM AND THE IMPLICATION FOR EPIKARSTIFICATION —An Example of Yaji Karst Experimental Site in Guilin,China

The carbon pools of biomass,littering,and SOC wre studied with regards to carbon cycles in epikarst zone,taking an example of Yaji Karst Experiemnt Site in Guilin.This study was focused on SOC and its lability,SOC decomposition rate,CO 2 regime in the soils. 13 ctracing was used to persua the relation of bicarbonate in karst water to soil carbon.The results indicated sufficient carbon pool in SOC for the driveing CO 2 in the karst system.It was revealed that about 60percent of carbon in epi-karst springs resulted from SOC during spring and summer.Thus,the CO 2,driving the karstification,was not simply due to adsorption of atmospheric CO 2 but due to carbon transfer through the pathway of air-plant-soil-water.The driving force should not be overlooked for the epi-karst formation by soil as an interface of carbon environmental geochemistry.

Air–water CO2 flux in an algae bloom year for Lake Hongfeng,Southwest China:implications for the carbon cycle of global inland waters

The carbon cycle of global inland waters is quantitatively comparable to other components in the global carbon budget. Among inland waters, a significant part is man-made lakes formed by damming rivers. Manmade lakes are undergoing a rapid increase in number and size. Human impacts and frequent algae blooms lead to it necessary to make a better constraint on their carbon cycles. Here, we make a primary estimation on the air–water CO_2 transfer flux through an algae bloom year for a subtropical man-made lake—Hongfeng Lake, Southwest China. To do this a new type of glass bottles was designed for content and isotopic analysis of DIC and other environmental parameters. At the early stage of algae bloom,CO_2 was transferred from the atmosphere to the lake with a net flux of 1.770 g·C·m^(-2). Later, the partial pressure(pCO_2) of the aqueous CO_2 increased rapidly and the lake outgassed to the atmosphere with a net flux of 95.727 g·C·m^(-2). In the remaining days, the lake again took up CO_2 from the atmosphere with a net flux of 14.804 g·C·m^(-2). As a whole, Lake Hongfeng released 4527 t C to the atmosphere, accounting for one-third of the atmosphere/soil CO_2 sequestered by chemical weathering in the whole drainage. With an empirical mode decomposition method, we found air temperature plays a major role in controlling water temperature, aqueous pCO_2 and hence CO_2 flux. This work indicates a necessity to make detailed and comprehensive carbon budgets in man-made lakes.

A model study on carbon cycle and phytoplankton dynamical processes in the Bohai Sea

The carbon cycle of lower trophic level in the Bohai Sea is studied with a three-dimensional biological and physical coupled model. The influences of the processes (including horizontal advection, river nutrient load, active transport etc. ) on the phytoplankton biomass and its evolution are estimated. The Bohai Sea is a weak sink of the CO2 in the atmosphere. During the cycle, 13.7% of the gross production of the phytoplankton enter the higher trophic level and 76.8 % of it are consumed by the respiration itself. The nutrient reproduction comes mainly from the internal biogeochemical loop and the rem-ineralization is an important mechanism of the nutrient transfer from organic form to inorganic. Horizontal advection decreases the total biomass and the eutrophication in some sea areas. Change in the nutrient load of a river can only adjust the local system near its estuary. Controlling the input of the nutrient, which limits the alga growth, can be very useful in lessening the phytoplankton biomass.

The Paleoproterozoic and Neoproterozoic Carbon Cycle Promoted the Evolution of a Habitable Earth

The carbon cycle is an important process that regulates Earth's evolution.We compare two typical periods,in the Paleoproterozoic and Neoproterozoic,in which many geological events occurred.It remains an open question when modern plate tectonics started on Earth and how it has influenced the carbon cycle through time.In the Paleoproterozoic,intense weathering in a highly CO_(2)and CH_(4)rich atmosphere caused more nutritional elements to be carried into the ocean.Terrestrial input boosted high biological productivity,deposition of sediments and the formation of an altered oceanic crust,which may have promoted an increase in the oxygen content.Sediment lubrication and a decrease in mantle potential temperature made cold and deep subduction possible,which carried more carbon into the deep mantle.Carbon can be stored in the mantle as diamond and carbonated mantle rocks,being released by arc and mid-ocean ridge outgassing at widely different times.From the Paleoproterozoic through the Neoproterozoic to the Phanerozoic,the carbon cycle has promoted the evolution of a habitable Earth.

Simulation of terrestrial carbon cycle balance model in Tibet

Based on climate material, the simplified terrestrial carbon cycle balance (TCCB) model was established, which is semi-mechanism and semi-statistics. Through TCCB model, our estimate indicates that the southeastern part of the Tibetan Plateau has much higher carbon content, and we have calculated the litter carbon pool, NPP, carbon fluxes and described their spatial characteristics in this region. Based on the TCCB model simulation, NPP in Tibet is 1.73×10 8 tC/a, soil organic input rate is 0.66×10 8 tC/a, litter mineralization rate is 1.07×10 8 tC/a, vegetation litterfall rate is 1.73×10 8 tC/a, the litter carbon pool is 7.26×10 8 tC, and soil decomposition rate is 309.54×10 8 tC/a. The carbon budget was also analyzed based on the estimates of carbon pool and fluxes. The spatial distributions of carbon pools and carbon fluxes in different compartments of terrestrial ecosystem were depicted with map respectively in Tibet. The distribution of NPP, vegetation litterfall rate, litter, litter mineralization rate, soil organic input rate and the soil decomposition rate were abstracted with temperature, precipitation, fractional vegetation and land feature.

Effects of solar radiation modification on the ocean carbon cycle:An earth system modeling study

Solar radiation modification(SRM,also termed as geoengineering)has been proposed as a potential option to counteract anthropogenic warming.The underlying idea of SRM is to reduce the amount of sunlight reaching the atmosphere and surface,thus offsetting some amount of global warming.Here,the authors use an Earth system model to investigate the impact of SRM on the global carbon cycle and ocean biogeochemistry.The authors simulate the temporal evolution of global climate and the carbon cycle from the pre-industrial period to the end of this century under three scenarios:the RCP4.5 CO_(2) emission pathway,the RCP8.5 CO_(2) emission pathway,and the RCP8.5 CO_(2) emission pathway with the implementation of SRM to maintain the global mean surface temperature at the level of RCP4.5.The simulations show that SRM,by altering global climate,also affects the global carbon cycle.Compared to the RCP8.5 simulation without SRM,by the year 2100,SRM reduces atmospheric CO_(2) by 65 ppm mainly as a result of increased CO_(2) uptake by the terrestrial biosphere.However,SRM-induced change in atmospheric CO_(2) and climate has a small effect in mitigating ocean acidification.By the year 2100,relative to RCP8.5,SRM causes a decrease in surface ocean hydrogen ion concentration([H^(+)])by 6% and attenuates the seasonal amplitude of[H^(+)]by about 10%.The simulations also show that SRM has a small effect on globally integrated ocean net primary productivity relative to the high-CO_(2) simulation without SRM.This study contributes to a comprehensive assessment of the effects of SRM on both the physical climate and the global carbon cycle.

Research and Application of Role Theory in Ocean Carbon Cycle Ontology Construction

Many researchers have studied the ocean carbon cycle model trying to regulate the level of CO2 in atmosphere from viewpoint of quantification. Unlike other researches, this paper analyzes the conversion process of carbon element in the ocean from the qualitative viewpoint. There are many complex roles in the ocean carbon cycle, and it is hard to represent the case that an entity plays different role in different environment. An ontology technology Hozo role theory developed by Osaka University Mizoguchi Laboratory is proposed as a solution. The basic concepts and representation mode of Hozo role theory is introduced. The conversion process of ocean carbon cycle is abstracted and an ontology model using Hozo role theory is proposed. Instead of comprehensive common ontology construction method, we propose our own ontology development steps. Then an ontology about ocean carbon cycle is built in order to describe and share the basic knowledge of ocean carbon cycle. A knowledge base of material circulation is proposed based on the ontology. Its construction framework is described and some knowledge base query examples are also illustrated. Conclusions show that the role theory can effectively solve the problem of multirole description in ocean carbon cycle, and knowledge reasoning based on ontology is also effective.

Effects of elevated pO_3 on carbon cycle between above andbelowground organs of trees

Translocation of carbohydrate from leaves to roots via phloem and reallocation from roots to leaves via xylem regulate the allocation of carbon （C） between above and belowground organs of trees. To quantitatively analyze effects of elevated ozone concentrations pO3 on the internal cycle of C, juvenile beech and spruce were grown in phytotrons and exposed to ambient and elevated pO3 （i.e. twice-ambient O3 levels, restricted to 〈 150 ppb） for two growing seasons. The translocation of C in the phloem and xylem was quantitatively studied by investigating the phloem/xylem-loading of sugars, the differentiation of stem conductive tissue and the hourly water flow through the stem. Results in the present study shown, elevated pO3 significantly decreased C translocation from shoot to roots in beech by reducing both sugar concentration in the phloem and conductive phloem area. Elevated pO3 also significantly decreased C reallocation from the roots to the shoot in beech by reducing both of sugar concentration in the xylem and transpiration rate. The adverse effects of elevated pO3 on C translocation in the phloem and xylem, however, were small in spruce. Contrasting to beech, spruce is less sensitive to elevated pO3, regarding to phloem differentiation and sugar concentrations in the phloem and xylem.

Interannual variability of carbon cycle implied by a 2-D atmospheric transport model

A 2-dimensional atmospheric transport model is deployed in a simplified CO 2 inverse study. Calculated carbon flux distribution for the interval from 1981 to 1997 confirms the existence of a terrestrial carbon sink in mid-high latitude area of North Hemisphere. Strong interannual variability exists in carbon flux patterns, implying a possible link with ENSO and other natural episodes such as Pinatubo volcano eruption in 1991. Mechanism of this possible link was investigated with statistic method. Correlation analysis indicated that in North Hemisphere, climatic factors such as temperature and precipitation, to some extend, could influence the carbon cycle process of land and ocean, thus cause considerable change in carbon flux distribution. In addition, correlation study also demonstrated the possible important role of Asian terrestrial ecosystems in carbon cycle.

Three-step modernization of the ocean:Modeling of carbon cycles and the revolution of ecological systems in the Ediacaran/Cambrian periods

Important ecological changes of the Earth （oxidization of the atmosphere and the ocean） increase in nutrient supply due to the break-up of the super continent （Rodinia） and the appearance of multi-cellular organisms （macroscopic algae and metazoan） took place in the Ediacaran period, priming the Cambrian explosion. The strong perturbations in carbon cycles in the ocean are recorded as excursions in carbonate and organic carbon isotope ratio （δ13Ccarb and δ13Corg） from the Ediacaran through early Cambrian periods. The Ediacaran-early Cambrian sediment records of δ13Ccarb and δ13Corg, obtained from the drill-core samples in Three Gorges in South China, are compared with the results of numerical simulation of a sim- ple one-zone model of the carbon cycle of the ocean, which has two reservoirs （i.e., dissolved organic carbon （DOC） and dissolved inorganic carbon （DIC）. The fluxes from the reservoirs are assumed to be proportional to the mass of the carbon reservoirs. We constructed a model, referred to here as the Best Fit Model （BFM）, which reproduce δ13Ccarb and δ13Corg records in the Ediacaran-early Cambrian period noted above. BFM reveals that the Shuram excursion is related to three major changes in the carbon cycle or the global ecological system of the Earth： （1） an increase in the coefficient of remineralization by a factor of ca. 100, possibly corresponding to a change in the dominant metabolism from anaerobic respiration to aerobic respiration, （2） an increase of carbon fractionation index from 25‰, to 33‰, possibly corresponding to the change in the primary producer from rock-living cyanobacteria to free-living macro algae, and （3） an in- crease in the coefficient of the organic carbon burial by a factor of ca. 100, possibly corresponding to the onset of a biological pump driven by the flourishing metazoan and zooplankton. The former two changes took place at the start of the Shuram excursion, while the third occurred at the end of the Shuram excursion. The other two excursions are explained by the tentative decrease in primary production due to cold periods, which correspond to the Gaskiers （ca. 580 Ma） and Bikonor （ca. 542 Ma） glaciations.

δ^(13)C_(org) perturbations preserved by the interglacial Datangpo Formation in South China with implications for stratigraphic correlation and carbon cycle

Palaeoclimatic and palaeoenvironmental reconstructions of the Cryogenian Period have attracted attention in relation to the debated“Snowball Earth”hypothesis and the early evolution of metazoan life.The carbon cycle and redox conditions of the Sturtian-Marinoan non-glacial interval have been subjected to much controversy in the past decades because of the lack of a high-resolution stratigraphic correlation scheme.As one of the typical Sturtian-Marinoan interglacial deposits,the Datangpo Formation was widely distributed in South China with shales continuously deposited.The previous zircon dating data of the Datangpo Formation provide important ages for global constrain of the Sturtian-Marinoan non-glacial interval.Here we present a high-resolution straitigraphic study of the organic carbon isotopes of the Datangpo Formation from a drill core section in northern Guizhou Province.Based on measured episodicδ^(13)C_(org) perturbations,three positive shifts and three negative excursions are identified.Aδ^(13)C_(org)-based chemostratigraphic correlation scheme is proposed herein that works well for the Datangpo Formation regionally.Meanwhile,theδ^(13)C_(org) vertical gradients changed dynamically throughout the formation.This discovery implies that a significant ocean circulation overturn might have occurred in the upper Datangpo Formation,coinciding with the potential oxygenation.

Global Carbon Project (GCP) Beijing Office:a new bridge for understanding regional carbon cycles

It has been widely accepted that human activities, especially burning fossil fuels and land use change, have altered the climate on earth and anthropogenic carbon fluxes have become comparable in magnitude with the natural fluxes in the global carbon cycle. The present and potential threat of adverse consequences has focused the attention of the scientists, policy makers and general public on the interaction among carbon cycle, climate change and human system. Asia is a hot spot from environmental change and sustainable development perspectives. The development pathways and environmental changes in the region have obvious consequences for the regional carbon cycle, even for global carbon budget, and the complex, diverse social, economic and environmental conditions make it highly diffficult to understand and quantify these consequences. The GCP Beijing Office ＂will have a supporting and coordinating role and will provide coordination, leadership and capacity building on carbon cycle sciences in China and to the larger region of Asia＂ and ＂liaise with the two International Project Offices based in Canberra and Tsukuba to coordinate a regional and global strategy consistent with the GCP Science and Implementation Framework＂.

Sino-Canadian Project on Carbon Cycle Kicks Off

A Sino-Canadian research project titled "Responding to the global warming: Improving China's carbon storage capacity" was officially initiated on August 2.……

Supply of Dissolved Organic Carbon from the Cold Seeps-Hydrothermal System and Its Impact on the Deep-Sea Carbon Cycle:An Overview

Dissolved carbon(dissolved organic carbon and dissolved inorganic carbon)is the major component of the ocean carbon cycle,representing one of the largest carbon pools on Earth.Cold seeps and hydrothermal systems serve as the two main windows for the material and energy recycling exchange between the lithosphere and outer spheres(biosphere,hydrosphere and atmosphere).However,recent studies have found that the dynamic activities of fluids in these two extreme systems are a crucial source of‘new'carbon in the deep ocean.These carbon sources may become vital contributors to carbon and energy in marine ecosystems,which affect the global deep-sea carbon budget,and the marine ecosystems as well.In this review,we summarize the sources and formation mechanisms of dissolved carbon in the seep fluids from the cold seeps and hydrothermal vents,the contribution of methane oxidation to dissolved carbon,and the characteristics of the carbon isotope composition in the fluid.Furthermore,we analyze and discuss the influence of carbon discharged from seabed on the seawater carbon cycle by comparing and contrasting these two extreme environments.The research may assist in promoting a deeper understanding of the carbon cycle and material interaction in the ocean,particularly further carbon cycle research in the back-arc basin where cold seeps and hydrothermal vents commonly prevail.

Unraveling the Cenozoic carbon cycle by reconstructing carbonate compensation depth(CCD)

The Carbonate Compensation Depth(CCD)refers to the depth within the ocean where the production and dissolution rates of carbonates reach equilibrium,widely likened to the oceanic calcareous‘snowline’.The reconstruction of deep-time CCD has significant implications for understanding ocean circulation,seawater chemical conditions,sediment distribution,and the surface carbon cycle.This paper critically reviews the methods for CCD reconstruction,summarizes the driving mechanisms of the Cenozoic CCD evolution and its association with the carbon cycle,and offers insights into future directions for CCD research.CCD reconstruction has evolved over the past half century from early qualitative to quantitative methods.These methodological improvements have markedly improved the accuracy and resolution of CCD.Existing studies have indicated a general trend of the CCD deepening across major ocean basins since the Cenozoic,interspersed with a minor shallowing phase during the mid-Miocene.The variations in the CCD are primarily influenced by factors such as ocean productivity,weathering,and shelf-basin partitioning.During climate events such as the Paleocene-Eocene Thermal Maximum,the CCD exhibits pulselike fluctuations.Future research should focus on precision and quantification while integrating model simulations to further explore the correlations and response mechanisms between the CCD and the paleoclimate as well as the carbon cycle.

Key processes of carbon cycle and sink enhancement paths in natural wetland ecosystems in China

Wetland ecosystems have become one of the long-term solutions for mitigating global climate change due to their strong carbon sequestration potential.However,the key carbon cycle processes in wetland ecosystems still lack a systematic summary.In the context of wetland protection and restoration,there is still a lack of consensus on the technical pathways to realize carbon sink multiplication in wetland ecosystems.In this paper,the key processes of carbon cycle,such as photosynthetic carbon uptake,microbial carbon decomposition and carbon deposition and burial,are sorted out and summarized in four major wetland types,namely,swamp and peat wetlands,river and riparian wetlands,lake and lakeshore wetlands,and estuarine and coastal wetlands.Based on the key processes of carbon cycle,three technological pathways for carbon sink multiplication are proposed,including,vegetation carbon sequestration and sink enhancement technology,soil carbon emission reduction technology and carbon deposition and burial technology.The key technologies under each pathway are further refined.And the carbon sink effects of the carbon sink technologies in different wetland types are qualitatively described.Also,wetland protection and restoration methods in corresponding regions are given in the light of the regional characteristics of wetlands in China.This will provide a scientific basis for the strategy of doubling the carbon sinks of China′s wetland ecosystems.

Extensive carbon cycle between peatland and vegetation:Insights from high net primary productivity of the Middle Jurassic in northwestern China

Peatlands have obvious carbon storage capacity and are crucial in mitigating global climate change.As the end-product of peatlands,coals have preserved a large amount of palaeoenvironmental information.The carbon accumulation rate and the net primary productivity(NPP)of coal-forming peatlands can be used as proxies for recovering palaeoenvironments.A super-thick coal seam(42°35'N,91°25'E)was developed in the Middle Jurassic Xishanyao Formation in the Shaerhu coalfield in the southern margin of the Tuha(Turpan-Hami)Basin,northwestern China.In this study,we use the time series analysis to identify the periods of Milankovitch orbital cycles in the Gamma-ray curve of this super-thick(124.85 m)coal and then use the obtained cycle periods of 405 ka,173 ka,44 ka,37.6 ka,22.5 ka to calculate the timeframe of the coalforming peatlands which ranges from 2703.44 to 2975.11 ka.Considering that the carbon content of the coal seam is 78.32%and the carbon loss during the coalification is about 25.80%,the carbon accumulation rate of the targeted coal seam is estimated to be 58.47-64.34 g C/m^(2)·a,and the NPP is estimated to be252.28-277.63 g C/m^(2)·a.The main palaeoenvironmental factors controlling the NPP of peatlands are CO_(2)content,palaeolatitude and palaeotemperature.The reduced NPP values of the palaeo-peatlands in the Shaerhu coalfield can be attributed to the mid-palaeolatitude and/or too low atmospheric CO_(2)contents.To a certain extent,the NPP of palaeo-peatlands reflects the changes in atmospheric CO_(2),which can further reveal the dynamic response of the global carbon cycle to climate change.Therefore,predicting the level of NPP in the Middle Jurassic and studying the final destination of carbon in the ecosystem are beneficial to understanding the coal-forming process and palaeoenvironment.

Impacts of land-use and climate changes on ecosystem productivity and carbon cycle in the cropping-grazing transitional zone in China

The impact of land-use/land-cover and climate changes on ecosystem productivity and carbon cycle is one of the most important issues in global change studies.In the past 20 years,the climate and land-use in China have changed significantly and have had important ecological consequences,especially in ecologically sensitive regions,e.g.the cropping-grazing transition zone(CGTZ).Here we present a study that used a process-based ecosystem model and data of land-use changes based on remote sensing and of climate change at high spatial and temporal resolution to estimate the impacts of land-use and climate changes on net primary productivity(NPP),vegetation carbon storage,soil heterotrophic respiration(HR),carbon storage and net ecosystem productivity(NEP)in the CGTZ of China.The results show that the warming and decreases in precipitation in CGTZ reduced NPP by 3.4%,increased HR by 4.3%,and re-duced annual mean total NEP by 33.7Tg from the 1980s to the 1990s.Although carbon storage in vegetation and soil was increasing because the mean NPP for the period was higher than HR,the decreasing NEP indicate that climate change reduced the carbon uptake rate.However,land-use changes in this zone caused increases in NPP by 3.8%,vegetation carbon storage by 2.4%,and annual total NEP by 0.59Tg.The land-use changes enhanced ecosystem carbon up-take,but not enough to offset the negative effect of the climate change.The climate change had greater impacts than the land-use change for the whole CGTZ zone,but had smaller impacts than the land-use change in the regions where it occurred.

Why are East Asian ecosystems important for carbon cycle research?

The global carbon cycle is one of the most important biogeochemical cycles. Through photosynthesis, green plants absorb CO2 from the atmosphere to produce organic matters,

The spatio-temporal responses of the carbon cycle to climate and land use/land cover changes between 1981-2000 in China

This paper represents the first national effort of its kind to systematically investigate the impact of changes in climate and land use and land cover （LULC） on the carbon cycle with high-resolution dynamic LULC data at the decadal scale （1990s and 2000s）. Based on simulations using well calibrated and validated Carbon Exchanges in the Vegetation-Soil-Atmosphere （CEVSA） model, tem- poral and spatial variations in carbon storage and fluxes in China may be generated empower us to relate these variations to climate variability and LULC with respect to net primary productivity （NPP）, heterotrophic respiration （HR）, net ecosystem productivity （NEP）, storage and soil carbon （SOC）, and vegetation carbon （VEGC） individually or collectively. Overall, the increases in NPP were greater than HR in most cases due to the effect of global warming with more precipitation in China from 1981 to 2000. With this trend, the NEP remained positive during that period, resulting in a net increase of total amount of carbon being stored by about 0.296 PgC within a 20-year time frame. Because the climate effect was much greater than that of changes of LULC, the total carbon storage in China actually increased by about 0.17 PgC within the 20-year time period. Such findings will contribute to the generation of carbon emissions control policies under global climate change impacts.