Primary productivity in the Antarctic aquatic environment with simple ecosystems is sensitive to climate and environmental fluctuations.We investigatedδ13C values for n-alkanoic acids derived from phototrophic organi...Primary productivity in the Antarctic aquatic environment with simple ecosystems is sensitive to climate and environmental fluctuations.We investigatedδ13C values for n-alkanoic acids derived from phototrophic organisms in a lacustrine sediment core(IIL3)to indicate primary productivity in ponds on Inexpressible Island in the western Ross Sea,Antarctica.Short-chain n-alkanoic acids(C14–C18)were abundant in the IIL3 sediment profile.The carbon isotope ratios of short-chain n-alkanoic acids in the sediment samples and floating microbial mats were similar,indicating that the short-chain n-alkanoic acids in the IIL3 sediment profile predominantly originated from phototrophic organisms.Theδ13C values for the short-chain n-alkanoic acids varied widely through the sediment profile,and 13C-enrichment of n-alkanoic acids was most likely related to high productivity due to carbon-limited conditions caused by enhanced photosynthetic efficiency.Theδ13C values for the n-alkanoic acids changed over the past 3200 years in similar ways to organic proxies for aquatic productivity(n-alkanoic acid and sterol sedimentary fluxes).C16 n-alkanoic acid was enriched in 13C in periods of high aquatic productivity~750–1650 and 3000–3200 a BP but depleted in 13C in periods of relatively low productivity~150–600 and 2500–3000 a BP.The results indicated that carbon isotope ratios of lipids from phototrophic organisms could be used as new proxies to reconstruct paleo-productivity in Antarctic lakes and ponds and therefore improve our understanding of past climate changes.展开更多
In order to understand the relative importance of anthropogenic and biological sources of carbonaceous aerosols in Northeast Asia,we measured total carbon(TC)and water-soluble organic carbon(WSOC)and their stable carb...In order to understand the relative importance of anthropogenic and biological sources of carbonaceous aerosols in Northeast Asia,we measured total carbon(TC)and water-soluble organic carbon(WSOC)and their stable carbon isotope ratios(d^(13)C)in total suspended particulates collected from Sapporo,northern Japan(43.07°N,141.36°E)over a 1-year period(during 2 September 2009and 5 October 2010).Temporal variations of TC showed a gradual decrease from mid-autumn to winter followed by a gradual increase to growing season with a peak in early summer.Both d^(13)C_(TC)and d^(13)C_(WSOC)showed very similar temporal trends with a gradual enrichment of^(13)C from mid-autumn to winter followed by a depletion in the^(13)C to early summer and thereafter it remained stable,except for few cases.Based on the results obtained together with the air mass trajectories,we found that biogenic emissions including biological particles(e.g.,pollen)and secondary organic aerosol formation from biogenic volatile organic compounds are the important sources of carbonaceous aerosols in spring/summer whereas fungal spores from soil and biomass burning and enhanced fossil fuel combustion contribute significantly in autumn/winter and in winter,respectively,in Northeast Asia.展开更多
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 organis...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.展开更多
The objective of this study was to investigate the geographical origin of Chinese teas using carbon and nitrogen stable isotope ratio technology.The results showed that inter-provincial dispersion of teas in Guangdong...The objective of this study was to investigate the geographical origin of Chinese teas using carbon and nitrogen stable isotope ratio technology.The results showed that inter-provincial dispersion of teas in Guangdong(GD),Guangxi(GX),Hainan(HA),Fujian(FJ),Shandong(SD),Sichuan(SC),Chongqing(CQ),and Henan(HN) provinces was high,while in Zhejiang(ZJ),Hubei(HB),Yunnan(YN),and Anhui(AH) provinces,it was low.Tea samples from GD,GX,HA,and FJ provinces were clustered in one group and separated from those from AH and HB provinces.Thus,carbon and nitrogen stable isotope ratio technology could discriminate teas from among some provinces of China,but not from among others.Better separation might be obtained with a combination of isotopic ratios and other indexes,such as elemental data and organic components.展开更多
Natural gases were widely distributed in the Jiyang Depression with complicated component composition, and it is difficult to identify their genesis. Based on investigation of gas composition, carbon isotope ratios, l...Natural gases were widely distributed in the Jiyang Depression with complicated component composition, and it is difficult to identify their genesis. Based on investigation of gas composition, carbon isotope ratios, light hydrocarbon properties, as well as geological analysis, natural gases in the Jiyang Depression are classified into two types, one is organic gas and the other is abiogenic gas. Abiogenic gas is mainly magmatogenic or mantlederived CO2. Organic gases are further divided into coaltype gas, oil-type gas, and biogas according to their kero- gen types and formation mechanisms. The oil-type gases are divided into mature oil-type gas （oil-associated gas） and highly mature oil-type gas. The highly mature oil-type gases can be subdivided into oil-cracking gas and kerogen thermal degradation gas. Identification factors for each kind of hydrocarbon gas were summarized. Based on genesis analysis results, the genetic types of gases buried in different depths were discussed. Results showed that shallow gases （〈1,500 m） are mainly mature oil-type gases, biogas, or secondary gases. Secondary gases are rich in methane because of chromatographic separation during migration and secondary biodegradation. Secondary biodegradation leads to richness of heavy carbon isotope ratios in methane and propane. Genesis of middle depth gases （1,500-3,500 m） is dominated by mature oil-type gases.Deep gases （3,500-5,500 m） are mainly kerogen thermal degradation gas, oil-cracking gas, and coal-type gas.展开更多
At present, shallow gases have received much attention due to low cost in exploration and production. Low-mature gases, as one significant origin to shallow gas, turns to be an important research topic. The present un...At present, shallow gases have received much attention due to low cost in exploration and production. Low-mature gases, as one significant origin to shallow gas, turns to be an important research topic. The present understanding of low-mature gases is confined within some geological cases, and few laboratory studies have been reported. Therefore, the potential and characters of low- mature gases are not clear up to now. Here, two premature samples （one coal and the other shale） were pyrolyzed in a gold confined system. The gaseous components including hydrocarbon gases and non-hydrocarbon gases were analyzed. Based on kinetic modeling, the formation of low-mature gases was modeled. The results showed that during low mature stage, about 178 mL/gTOC gas was generated from the shale and 100 mL/gTOC from the coal. Two third to three fourth of the generated gases are non-hydrocarbon gases such as H2S and CO2. The total yields of C1-5 for the two samples are almost the same, 30-40 mL/gTOC, but individual gaseous hydrocarbon is different. The shale has much lower C1 but higher C2-5, whereas the coal has higher C1 but lower C2-5. Hydrocarbon gases formed during low-mature stage are very wet. The stable carbon isotope ratios of methane range from -40‰ to -50‰ （PDB）, in good consistence with empiric criterion for low-mature gases summed up by the previous researchers. The generation characters suggest that the low-mature gases could be accumulated to form an economic gas reservoir, but most of them occur only as associated gases.展开更多
In this study,a coniferous tree species(Pinus tabuliformis Carr.) was investigated at a moderate-altitude mountainous terrain on the southern slope of the middle Qinling Mountains(QLM) to detect the trends in carbon i...In this study,a coniferous tree species(Pinus tabuliformis Carr.) was investigated at a moderate-altitude mountainous terrain on the southern slope of the middle Qinling Mountains(QLM) to detect the trends in carbon isotope ratio( δ^(13)C),leaf nitrogen content(LNC) and stomatal density(SD) with altitude variation in northsubtropical humid mountain climate zone of China.The results showed that LNC and SD both significantly increased linearly along the altitudinal gradient ranging from 1000 to 2200 m,whereas leafδ^(13)C exhibited a significantly negative correlation with the altitude.Such a correlation pattern differs obviously from that obtained in offshore low-altitude humid environment or inland high-altitude semi-arid environment,suggesting that the pattern of increasing δ^(13)C with the altitude cannot be generalized.The negative correlation between δ ^(13)C and altitude might be attributed mainly to the strengthening of carbon isotope fractionation in plants caused by increasing precipitation with altitude.Furthermore,there was a remarkable negative correlation between leaf δ ^(13)C and LNC.One possible reason was that increasing precipitation that operates to increase isotopic discrimination with altitude overtook the LNC in determining the sign of leaf δ ^(13)C.The significant negative correlation between leaf δ ^(13)C and SD over altitudes was also found in the present study,indicating that increases in SD with altitude would reduce,rather than enhance plant δ^(13)C values.展开更多
A long-term experiment set up in 1980 compared the effects of applying manures and chemical fertilizers on a paddy soil in the Taihu Lake region, China. Of the fourteen randomly distributed treatments consisting of di...A long-term experiment set up in 1980 compared the effects of applying manures and chemical fertilizers on a paddy soil in the Taihu Lake region, China. Of the fourteen randomly distributed treatments consisting of different combinations of organic manure, inorganic nitrogen （N）, phosphorus （P）, and potassium （K）, and rice straw, eight were selected for the present study in 2007. Application of organic manure plus straw significantly increased soil organic carbon （SOC） content of the topsoil （0-10 cm） compared to that of chemical fertilizers alone. The content of SOC was relatively stable in the 10-30 cm layer in the chemical fertilizer treatments and in the 20-40 cm layer in the manure treatments. The stable carbon isotope ratio （513C） ranged from -24% to -28% and increased gradually with depth. The content of SOC was significantly （P 〈 0.05） negatively correlated with 513C. In the 0-20 cm layer, the 513C value significantly decreased in the treatments of manure alone （M）, manure and chemical N and P fertilizers （MNP）, manure and chemical N, P, and K fertilizers （MNPK）, manure, rice straw, and chemical N fertilizer （MRN）, and chemical N fertilizer and rice straw （CNR）, as compared with the no-fertilizer control. In the 30-50 cm layer, however, the ratio significantly increased in all the treatments except Treatment CNR. Mineralization of organic C peaked in the first 2-4 d of incubation and gradually leveled off thereafter over the first 3 weeks, being faster in the manure treatments than the chemical fertilizer treatments. The average rate of mineralization varied from 55.36 to 75.46 mL CO2 kg-1 d-1 and that of stable mineralization from 10 to 20 mL CO2 kg-1 d-1. In eight weeks of incubation, cumulative mineralization was always higher in the manure treatments than the chemical fertilizer treatments, being the highest in Treatment MRN. Combined humus in the soil was mainly （over 50%） composed of tightly combined fraction. The loosely combined humus and its ratio of humic acid （HA） to fulvic acid （FA） significantly increased with long-term application of organic manure and chemical fertilizers. It could be concluded that the cycle of organic C in the paddy soil ecosystem studied was stable over the long-term application of fertilizers and continued cultivation.展开更多
Carbonate cement is the most abundant cement type in the Fourth Member of the Xujiahe Formation in the Xiaoquan-Fenggu area of the West Sichuan Depression. Here we use a systematic analysis of carbonate cement petrolo...Carbonate cement is the most abundant cement type in the Fourth Member of the Xujiahe Formation in the Xiaoquan-Fenggu area of the West Sichuan Depression. Here we use a systematic analysis of carbonate cement petrology, mineralogy, carbon and oxygen isotope ratios and enclosure homogenization temperatures to study the precipitation mechanism, pore fluid evolu- tion, and distribution of different types of carbonate cement in reservoir sand in the study area. Crystalline calcite has relatively heavy carbon and oxygen isotope ratios （δ13C = 2.14%o, 8180 = -5.77‰）, and was precipitated early. It was precipitated di- rectly from supersaturated alkaline fluid under normal temperature and pressure conditions. At the time of precipitation, the fluid oxygen isotope ratio was very light, mainly showing the characteristics of a mixed meteoric water-seawater fluid（ δ180 = -3‰）, which shows that the fluid during precipitation was influenced by both meteoric water and seawater. The calcite cement that fills in the secondary pores has relatively lighter carbon and oxygen isotope ratios （δ13C = -2.36%0, 8180 = -15.68‰）. This cement was precipitated late, mainly during the Middle and Late Jurassic. An important material source for this carbonate cement was the feldspar corrosion process that involved organic matter. The Ca2＋, Fe3＋ and Mg2＋ ions released by the clay mineral transformation process were also important source materials. Because of water-rock interactions during the buri- al process, the oxygen isotope ratio of the fluid significantly increased during precipitation, by about 3‰. The dolomite ce- ments in calcarenaceous sandstone that was precipitated during the Middle Jurassic have heavier carbon and oxygen isotope ratios, which are similar to those of carbonate debris in the sandstone （δ13C = 1.93%o, δ180 = -6.11‰）, demonstrating that the two are from the same source that had a heavier oxygen isotope ratio （δ180 of about 2.2‰）. The differences in fluid oxygen isotope ratios during cement precipitation reflect the influences of different water-rock interaction systems or different wa- ter-rock interaction strengths. This is the main reason why the sandstone containing many rigid particles （lithic quartz sand- stone） has a relatively negative carbon isotope ratio and why the precipitation fluid in calcarenaceous sandstone has a relatively heavier oxygen isotope ratio.展开更多
The Mid-Miocene Climatic Optimum （MMCO; 15-17 Ma） was one of the short-term climatic warm events that punctuated the Cenozoic long-term cooling trend. Because there are very few terrestrial records of this event, m...The Mid-Miocene Climatic Optimum （MMCO; 15-17 Ma） was one of the short-term climatic warm events that punctuated the Cenozoic long-term cooling trend. Because there are very few terrestrial records of this event, most of our understanding comes from marine cores. In this report, we first present new palaeomagnetic data that revises the dating of our 400 m-thick lacustrine section in Wenshan （Yunnan）, previously thought to be Late Mio- cene. These new data suggest an older age, ca. 15.2-16.5 Ma, coinciding with the MMCO. We measured δ13C on bulk organic matter （3 Corg）, total organic carbon （TOC）, total nitrogen （TN） and C/N ratios at a high sample resolution to： （1） reconstruct the palaeoenvironmental changes in the lake catchment area, and （2） infer mechanisms responsible for these changes. Our results show that all four geochemical parameters demonstrate that a strong environmental change occurred around the middle of the section, shortly after the C5Cn/C5Br geomagnetic reversal and the Early/Middle Miocene boundary at 15.97 Ma. We propose that the environmental shift may be due to a combination of a change in climate, which became cooler, together with a change in organic matter cycling within the lake. This study provides a new insight into the MMCO and demonstrates that although the MMCO was generally a warm event, it was also a time of climatic instability and abrupt environmental changes.展开更多
The innovations of agricultural production and their extensive dispersal promoted the transformation of human livelihoods and profoundly influenced the evolution of human-land relationships in late prehistoric Eurasia...The innovations of agricultural production and their extensive dispersal promoted the transformation of human livelihoods and profoundly influenced the evolution of human-land relationships in late prehistoric Eurasia.The Steppe and Silk Roads(SSRs)played important roles in the transcontinental exchange and dispersal of cereal crops and livestock related to agricultural innovation across Eurasia before the Han Dynasty(202 BC to AD 220),while the geographical-temporal variations in prehistoric subsistence in relation to the spread and exchange of cereal crops and livestock originating from different areas of Eurasia still remain unclear.In this paper,we explore these issues based on the review and analysis of published archaeobotanical,zooarchaeological,and carbon-stable isotope data from human bones from Neolithic-Early Iron Age sites in areas along the SSRs,with a comparison to updated results based on radiocarbon dating and ancient DNA analyses.Our results suggest that humans engaged in hunting game,while foxtail/broomcorn millet cultivation gradually became the primary subsistence strategy in Eastern SSRs from 10,500 to 6000 a BP.In contemporaneous Western SSRs,humans mainly cultivated wheat/barley and raised sheep/goats,cattle,and pigs.Trans-Eurasian exchange,which is reflected by the mixed utilization of wheat/barley and millet,emerged in the south-central Steppe during 6000–4000 a BP,while millet cultivation and pig husbandry became the dominant livelihoods in most areas of Eastern SSRs.During 4000–2200 a BP,Silk Roads became the major passageway for trans-Eurasian exchange,the interactive development of oasis agriculture and pastoralism facilitated intensive human settlement in the Central Silk Roads,and subsistence strategies substantially changed with significant geographical differences in Eastern SSRs,while subsistence in some areas of Western SSRs was evidently affected by the introduction and adoption of millet crops after 3000 a BP.The geographical-temporal variations in subsistence in the SSRs from the Neolithic to Early Iron Age were primarily affected by the prehistoric dispersal of farming groups across Eurasia,which was accompanied by the spread of cereal crops/livestock,while the impacts of climate change still need to be further evaluated.展开更多
Aims Subalpine coniferous species are distributed over a wide range of elevations in which they must contend with stressful conditions,such as high elevations and extended periods of darkness.Two evergreen coniferous ...Aims Subalpine coniferous species are distributed over a wide range of elevations in which they must contend with stressful conditions,such as high elevations and extended periods of darkness.Two evergreen coniferous species,Abies veitchii and Abies mariesii,dominate at low and high elevations,respectively,in the subalpine zone,central Japan.The aim of this study is to examine the effects of leaf age,elevation and light conditions on photosynthetic rates through changes in morphological and physiological leaf traits in the two species.Methods We here examined effects of leaf age,elevation and light conditions on photosynthesis,and leaf traits in A.veitchii and A.mariesii.Saplings of the two conifers were sampled in the understory and canopy gaps at their lower(1600 m)and upper(2300 m)distribution limits.Important Findings The two species showed similar responses to leaf age and different responses to elevation and light conditions in photosynthesis and leaf traits.The maximum photosynthetic rate of A.veitchii is correlated negatively with leaf mass per area(LMA)and non-structural carbohydrate(NSC)concentration.LMA increased at high elevations in the two species,whereas NSC concentrations increased only in A.veitchii.Therefore,the maximum photosynthetic rate of A.veitchii decreased at high elevations.Furthermore,maximum photosynthetic rates correlate positively with nitrogen concentration in both species.In the understory,leaf nitrogen concentrations decreased and increased in A.veitchii and A.mariesii,respectively.LMA decreased and the chlorophyll-to-nitrogen ratio increased in understory conditions only for A.mariesii,suggesting it has a higher light-capture efficiency in dark conditions than does A.veitchii.This study concluded that A.mariesii has more shade-tolerant photosynthetic and leaf traits and its photosynthetic rate is less affected by elevation compared with A.veitchii,allowing A.mariesii to survive in the understory and to dominate at high elevations.展开更多
基金supported by the National Natural Science Foundation of China (Grant nos. 42276240, 42206243, 41776188)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant no. XDB40000000)+3 种基金the Shanghai Sailing Program (Grant no. 22YF1418800)the China Postdoctoral Science Foundation (Grant no. 2022M712038)the Shanghai Frontiers Science Center of Polar Science (SCOPS)the Chinese Arctic and Antarctic Administration (CAA) for supporting the project
文摘Primary productivity in the Antarctic aquatic environment with simple ecosystems is sensitive to climate and environmental fluctuations.We investigatedδ13C values for n-alkanoic acids derived from phototrophic organisms in a lacustrine sediment core(IIL3)to indicate primary productivity in ponds on Inexpressible Island in the western Ross Sea,Antarctica.Short-chain n-alkanoic acids(C14–C18)were abundant in the IIL3 sediment profile.The carbon isotope ratios of short-chain n-alkanoic acids in the sediment samples and floating microbial mats were similar,indicating that the short-chain n-alkanoic acids in the IIL3 sediment profile predominantly originated from phototrophic organisms.Theδ13C values for the short-chain n-alkanoic acids varied widely through the sediment profile,and 13C-enrichment of n-alkanoic acids was most likely related to high productivity due to carbon-limited conditions caused by enhanced photosynthetic efficiency.Theδ13C values for the n-alkanoic acids changed over the past 3200 years in similar ways to organic proxies for aquatic productivity(n-alkanoic acid and sterol sedimentary fluxes).C16 n-alkanoic acid was enriched in 13C in periods of high aquatic productivity~750–1650 and 3000–3200 a BP but depleted in 13C in periods of relatively low productivity~150–600 and 2500–3000 a BP.The results indicated that carbon isotope ratios of lipids from phototrophic organisms could be used as new proxies to reconstruct paleo-productivity in Antarctic lakes and ponds and therefore improve our understanding of past climate changes.
基金supported by the Environment Research and Technology Development Fund(B-0903)of the Ministry of the Environment,Japan,the Japan Society for the Promotion of Science(JSPS)Japan through Grant-in-Aid No.24221001985 Project of National Key Universities,Tianjin University,China
文摘In order to understand the relative importance of anthropogenic and biological sources of carbonaceous aerosols in Northeast Asia,we measured total carbon(TC)and water-soluble organic carbon(WSOC)and their stable carbon isotope ratios(d^(13)C)in total suspended particulates collected from Sapporo,northern Japan(43.07°N,141.36°E)over a 1-year period(during 2 September 2009and 5 October 2010).Temporal variations of TC showed a gradual decrease from mid-autumn to winter followed by a gradual increase to growing season with a peak in early summer.Both d^(13)C_(TC)and d^(13)C_(WSOC)showed very similar temporal trends with a gradual enrichment of^(13)C from mid-autumn to winter followed by a depletion in the^(13)C to early summer and thereafter it remained stable,except for few cases.Based on the results obtained together with the air mass trajectories,we found that biogenic emissions including biological particles(e.g.,pollen)and secondary organic aerosol formation from biogenic volatile organic compounds are the important sources of carbonaceous aerosols in spring/summer whereas fungal spores from soil and biomass burning and enhanced fossil fuel combustion contribute significantly in autumn/winter and in winter,respectively,in Northeast Asia.
基金partly supported by grants for "Secular variation of seawater composition(No. 16740284)""Coevolution of surface environment and solid Earth from the Neoproterozoic Snowball Earth to Cambrian explosion events(No.18740318)"+1 种基金the 21st Century COE Program "How to build habitable planets" at the Tokyo Institute of Technology from the Ministry of Education,Culture,Sports,Science and Technology,Japanthe Mitsubishi Foundation (T.K.)
文摘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.
基金Project supported by the National Key Technologies R&D Program of China during the 11th Five-Year Plan Period (No. 2006BAK02A18)the Innovation Team of the Safety Standards and Testing Technology for Agricultural Products of Zhejiang Province,China(No. 2010R50028)
文摘The objective of this study was to investigate the geographical origin of Chinese teas using carbon and nitrogen stable isotope ratio technology.The results showed that inter-provincial dispersion of teas in Guangdong(GD),Guangxi(GX),Hainan(HA),Fujian(FJ),Shandong(SD),Sichuan(SC),Chongqing(CQ),and Henan(HN) provinces was high,while in Zhejiang(ZJ),Hubei(HB),Yunnan(YN),and Anhui(AH) provinces,it was low.Tea samples from GD,GX,HA,and FJ provinces were clustered in one group and separated from those from AH and HB provinces.Thus,carbon and nitrogen stable isotope ratio technology could discriminate teas from among some provinces of China,but not from among others.Better separation might be obtained with a combination of isotopic ratios and other indexes,such as elemental data and organic components.
文摘Natural gases were widely distributed in the Jiyang Depression with complicated component composition, and it is difficult to identify their genesis. Based on investigation of gas composition, carbon isotope ratios, light hydrocarbon properties, as well as geological analysis, natural gases in the Jiyang Depression are classified into two types, one is organic gas and the other is abiogenic gas. Abiogenic gas is mainly magmatogenic or mantlederived CO2. Organic gases are further divided into coaltype gas, oil-type gas, and biogas according to their kero- gen types and formation mechanisms. The oil-type gases are divided into mature oil-type gas （oil-associated gas） and highly mature oil-type gas. The highly mature oil-type gases can be subdivided into oil-cracking gas and kerogen thermal degradation gas. Identification factors for each kind of hydrocarbon gas were summarized. Based on genesis analysis results, the genetic types of gases buried in different depths were discussed. Results showed that shallow gases （〈1,500 m） are mainly mature oil-type gases, biogas, or secondary gases. Secondary gases are rich in methane because of chromatographic separation during migration and secondary biodegradation. Secondary biodegradation leads to richness of heavy carbon isotope ratios in methane and propane. Genesis of middle depth gases （1,500-3,500 m） is dominated by mature oil-type gases.Deep gases （3,500-5,500 m） are mainly kerogen thermal degradation gas, oil-cracking gas, and coal-type gas.
基金supported by the CNPC Project(Grant No.06-01C-01-04)National Natural Science Foundation of China(Grant No.40603014).
文摘At present, shallow gases have received much attention due to low cost in exploration and production. Low-mature gases, as one significant origin to shallow gas, turns to be an important research topic. The present understanding of low-mature gases is confined within some geological cases, and few laboratory studies have been reported. Therefore, the potential and characters of low- mature gases are not clear up to now. Here, two premature samples （one coal and the other shale） were pyrolyzed in a gold confined system. The gaseous components including hydrocarbon gases and non-hydrocarbon gases were analyzed. Based on kinetic modeling, the formation of low-mature gases was modeled. The results showed that during low mature stage, about 178 mL/gTOC gas was generated from the shale and 100 mL/gTOC from the coal. Two third to three fourth of the generated gases are non-hydrocarbon gases such as H2S and CO2. The total yields of C1-5 for the two samples are almost the same, 30-40 mL/gTOC, but individual gaseous hydrocarbon is different. The shale has much lower C1 but higher C2-5, whereas the coal has higher C1 but lower C2-5. Hydrocarbon gases formed during low-mature stage are very wet. The stable carbon isotope ratios of methane range from -40‰ to -50‰ （PDB）, in good consistence with empiric criterion for low-mature gases summed up by the previous researchers. The generation characters suggest that the low-mature gases could be accumulated to form an economic gas reservoir, but most of them occur only as associated gases.
基金supported by Hunan Province Natural Science Foundation (No.2015JJ2062)the State Key Laboratory of Soil and Sustainable Agriculture (Grant No.Y412201416)the Scientific Research Fund of Hunan Provincial Education Department (Grant No.14A054)
文摘In this study,a coniferous tree species(Pinus tabuliformis Carr.) was investigated at a moderate-altitude mountainous terrain on the southern slope of the middle Qinling Mountains(QLM) to detect the trends in carbon isotope ratio( δ^(13)C),leaf nitrogen content(LNC) and stomatal density(SD) with altitude variation in northsubtropical humid mountain climate zone of China.The results showed that LNC and SD both significantly increased linearly along the altitudinal gradient ranging from 1000 to 2200 m,whereas leafδ^(13)C exhibited a significantly negative correlation with the altitude.Such a correlation pattern differs obviously from that obtained in offshore low-altitude humid environment or inland high-altitude semi-arid environment,suggesting that the pattern of increasing δ^(13)C with the altitude cannot be generalized.The negative correlation between δ ^(13)C and altitude might be attributed mainly to the strengthening of carbon isotope fractionation in plants caused by increasing precipitation with altitude.Furthermore,there was a remarkable negative correlation between leaf δ ^(13)C and LNC.One possible reason was that increasing precipitation that operates to increase isotopic discrimination with altitude overtook the LNC in determining the sign of leaf δ ^(13)C.The significant negative correlation between leaf δ ^(13)C and SD over altitudes was also found in the present study,indicating that increases in SD with altitude would reduce,rather than enhance plant δ^(13)C values.
基金Supported by the National Key Basic Research and Development Program of China (No. 2005CB121108)the Key Project of National Natural Science Foundation of China (No. 40335047)
文摘A long-term experiment set up in 1980 compared the effects of applying manures and chemical fertilizers on a paddy soil in the Taihu Lake region, China. Of the fourteen randomly distributed treatments consisting of different combinations of organic manure, inorganic nitrogen （N）, phosphorus （P）, and potassium （K）, and rice straw, eight were selected for the present study in 2007. Application of organic manure plus straw significantly increased soil organic carbon （SOC） content of the topsoil （0-10 cm） compared to that of chemical fertilizers alone. The content of SOC was relatively stable in the 10-30 cm layer in the chemical fertilizer treatments and in the 20-40 cm layer in the manure treatments. The stable carbon isotope ratio （513C） ranged from -24% to -28% and increased gradually with depth. The content of SOC was significantly （P 〈 0.05） negatively correlated with 513C. In the 0-20 cm layer, the 513C value significantly decreased in the treatments of manure alone （M）, manure and chemical N and P fertilizers （MNP）, manure and chemical N, P, and K fertilizers （MNPK）, manure, rice straw, and chemical N fertilizer （MRN）, and chemical N fertilizer and rice straw （CNR）, as compared with the no-fertilizer control. In the 30-50 cm layer, however, the ratio significantly increased in all the treatments except Treatment CNR. Mineralization of organic C peaked in the first 2-4 d of incubation and gradually leveled off thereafter over the first 3 weeks, being faster in the manure treatments than the chemical fertilizer treatments. The average rate of mineralization varied from 55.36 to 75.46 mL CO2 kg-1 d-1 and that of stable mineralization from 10 to 20 mL CO2 kg-1 d-1. In eight weeks of incubation, cumulative mineralization was always higher in the manure treatments than the chemical fertilizer treatments, being the highest in Treatment MRN. Combined humus in the soil was mainly （over 50%） composed of tightly combined fraction. The loosely combined humus and its ratio of humic acid （HA） to fulvic acid （FA） significantly increased with long-term application of organic manure and chemical fertilizers. It could be concluded that the cycle of organic C in the paddy soil ecosystem studied was stable over the long-term application of fertilizers and continued cultivation.
基金supported by the State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Foundation (Grant No. PLC201101)the National Natural Science Foundation of China (Grant Nos. 41172119 and 41272130)
文摘Carbonate cement is the most abundant cement type in the Fourth Member of the Xujiahe Formation in the Xiaoquan-Fenggu area of the West Sichuan Depression. Here we use a systematic analysis of carbonate cement petrology, mineralogy, carbon and oxygen isotope ratios and enclosure homogenization temperatures to study the precipitation mechanism, pore fluid evolu- tion, and distribution of different types of carbonate cement in reservoir sand in the study area. Crystalline calcite has relatively heavy carbon and oxygen isotope ratios （δ13C = 2.14%o, 8180 = -5.77‰）, and was precipitated early. It was precipitated di- rectly from supersaturated alkaline fluid under normal temperature and pressure conditions. At the time of precipitation, the fluid oxygen isotope ratio was very light, mainly showing the characteristics of a mixed meteoric water-seawater fluid（ δ180 = -3‰）, which shows that the fluid during precipitation was influenced by both meteoric water and seawater. The calcite cement that fills in the secondary pores has relatively lighter carbon and oxygen isotope ratios （δ13C = -2.36%0, 8180 = -15.68‰）. This cement was precipitated late, mainly during the Middle and Late Jurassic. An important material source for this carbonate cement was the feldspar corrosion process that involved organic matter. The Ca2＋, Fe3＋ and Mg2＋ ions released by the clay mineral transformation process were also important source materials. Because of water-rock interactions during the buri- al process, the oxygen isotope ratio of the fluid significantly increased during precipitation, by about 3‰. The dolomite ce- ments in calcarenaceous sandstone that was precipitated during the Middle Jurassic have heavier carbon and oxygen isotope ratios, which are similar to those of carbonate debris in the sandstone （δ13C = 1.93%o, δ180 = -6.11‰）, demonstrating that the two are from the same source that had a heavier oxygen isotope ratio （δ180 of about 2.2‰）. The differences in fluid oxygen isotope ratios during cement precipitation reflect the influences of different water-rock interaction systems or different wa- ter-rock interaction strengths. This is the main reason why the sandstone containing many rigid particles （lithic quartz sand- stone） has a relatively negative carbon isotope ratio and why the precipitation fluid in calcarenaceous sandstone has a relatively heavier oxygen isotope ratio.
基金The authors are grateful to two anonymous reviewers for their constructive comments, which significantly improved the manuscript. The authors thank fellow members of staff of the Palaeoecology group in Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences for assistance during sample collection and productive critical discussions Professor Yun Fu from the Central Laboratory of Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences for assistance during the TN mea- surements+1 种基金 Dr. Olesya V. Bondarenko, from the Russian Academy of Sciences, Vladivostok, for her help and support during sample preparation Yi-Min Tian from the Faculty of Land Resource Engi- neering, Kunming University of Science and Technology, for her assistance when preparing and observing thin sections. The authors are grateful to Dr. Andrea Kern from the USGS and Dr. Dayou Zhai from Yunnan University for fruitful discussions and suggestions to improve the manuscript. This study was supported by National Nat- ural Science Foundation of China （U1502231）, the CAS 135 Program （XTBG-F01）, and a grant from the China Scholarship Council to J. Lebreton Anberr6e （2013GCX606）. Shihu Li and Chenglong Deng acknowledge support from the National Natural Science Foundation of China （41404056）, and the State Key Laboratory of Lithospheric Evolution （11431780）. Shu-Feng Li was supported by the Foundation of the State Key Laboratory of Paleobiology and Stratigraphy, Nanjing Institute of Geology and Paleontology, CAS （15310）. This work is part of the NECLIME （Neogene Climate of Eurasia） network.
文摘The Mid-Miocene Climatic Optimum （MMCO; 15-17 Ma） was one of the short-term climatic warm events that punctuated the Cenozoic long-term cooling trend. Because there are very few terrestrial records of this event, most of our understanding comes from marine cores. In this report, we first present new palaeomagnetic data that revises the dating of our 400 m-thick lacustrine section in Wenshan （Yunnan）, previously thought to be Late Mio- cene. These new data suggest an older age, ca. 15.2-16.5 Ma, coinciding with the MMCO. We measured δ13C on bulk organic matter （3 Corg）, total organic carbon （TOC）, total nitrogen （TN） and C/N ratios at a high sample resolution to： （1） reconstruct the palaeoenvironmental changes in the lake catchment area, and （2） infer mechanisms responsible for these changes. Our results show that all four geochemical parameters demonstrate that a strong environmental change occurred around the middle of the section, shortly after the C5Cn/C5Br geomagnetic reversal and the Early/Middle Miocene boundary at 15.97 Ma. We propose that the environmental shift may be due to a combination of a change in climate, which became cooler, together with a change in organic matter cycling within the lake. This study provides a new insight into the MMCO and demonstrates that although the MMCO was generally a warm event, it was also a time of climatic instability and abrupt environmental changes.
基金supported by the National Key R&D Program of China(Grant No.2018YFA0606402)the Strategic Priority Research Program of the Chinese Academy of Sciences(A)(Grant No.XDA2004010101)the Second Tibetan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK0601)。
文摘The innovations of agricultural production and their extensive dispersal promoted the transformation of human livelihoods and profoundly influenced the evolution of human-land relationships in late prehistoric Eurasia.The Steppe and Silk Roads(SSRs)played important roles in the transcontinental exchange and dispersal of cereal crops and livestock related to agricultural innovation across Eurasia before the Han Dynasty(202 BC to AD 220),while the geographical-temporal variations in prehistoric subsistence in relation to the spread and exchange of cereal crops and livestock originating from different areas of Eurasia still remain unclear.In this paper,we explore these issues based on the review and analysis of published archaeobotanical,zooarchaeological,and carbon-stable isotope data from human bones from Neolithic-Early Iron Age sites in areas along the SSRs,with a comparison to updated results based on radiocarbon dating and ancient DNA analyses.Our results suggest that humans engaged in hunting game,while foxtail/broomcorn millet cultivation gradually became the primary subsistence strategy in Eastern SSRs from 10,500 to 6000 a BP.In contemporaneous Western SSRs,humans mainly cultivated wheat/barley and raised sheep/goats,cattle,and pigs.Trans-Eurasian exchange,which is reflected by the mixed utilization of wheat/barley and millet,emerged in the south-central Steppe during 6000–4000 a BP,while millet cultivation and pig husbandry became the dominant livelihoods in most areas of Eastern SSRs.During 4000–2200 a BP,Silk Roads became the major passageway for trans-Eurasian exchange,the interactive development of oasis agriculture and pastoralism facilitated intensive human settlement in the Central Silk Roads,and subsistence strategies substantially changed with significant geographical differences in Eastern SSRs,while subsistence in some areas of Western SSRs was evidently affected by the introduction and adoption of millet crops after 3000 a BP.The geographical-temporal variations in subsistence in the SSRs from the Neolithic to Early Iron Age were primarily affected by the prehistoric dispersal of farming groups across Eurasia,which was accompanied by the spread of cereal crops/livestock,while the impacts of climate change still need to be further evaluated.
基金supported by grants(20292081)from the Ministry of Education,Culture,Sports,Science and Technology,Japan.
文摘Aims Subalpine coniferous species are distributed over a wide range of elevations in which they must contend with stressful conditions,such as high elevations and extended periods of darkness.Two evergreen coniferous species,Abies veitchii and Abies mariesii,dominate at low and high elevations,respectively,in the subalpine zone,central Japan.The aim of this study is to examine the effects of leaf age,elevation and light conditions on photosynthetic rates through changes in morphological and physiological leaf traits in the two species.Methods We here examined effects of leaf age,elevation and light conditions on photosynthesis,and leaf traits in A.veitchii and A.mariesii.Saplings of the two conifers were sampled in the understory and canopy gaps at their lower(1600 m)and upper(2300 m)distribution limits.Important Findings The two species showed similar responses to leaf age and different responses to elevation and light conditions in photosynthesis and leaf traits.The maximum photosynthetic rate of A.veitchii is correlated negatively with leaf mass per area(LMA)and non-structural carbohydrate(NSC)concentration.LMA increased at high elevations in the two species,whereas NSC concentrations increased only in A.veitchii.Therefore,the maximum photosynthetic rate of A.veitchii decreased at high elevations.Furthermore,maximum photosynthetic rates correlate positively with nitrogen concentration in both species.In the understory,leaf nitrogen concentrations decreased and increased in A.veitchii and A.mariesii,respectively.LMA decreased and the chlorophyll-to-nitrogen ratio increased in understory conditions only for A.mariesii,suggesting it has a higher light-capture efficiency in dark conditions than does A.veitchii.This study concluded that A.mariesii has more shade-tolerant photosynthetic and leaf traits and its photosynthetic rate is less affected by elevation compared with A.veitchii,allowing A.mariesii to survive in the understory and to dominate at high elevations.
