Understanding the relationship between forest management and water use efficiency(WUE)is important for evaluating forest adaptability to climate change.However,the effects of thinning and understory removal on WUE and...Understanding the relationship between forest management and water use efficiency(WUE)is important for evaluating forest adaptability to climate change.However,the effects of thinning and understory removal on WUE and its key controlling processes are not well understood,which limits our comprehension of the physiological mechanisms of various management practices.In this study,four forest management measures(no thinning:NT;understory removal:UR;light thinning:LT;and heavy thinning:HT)were carried out in Pinus massoniana plantations in a subtropical region of China.Photosynthetic capacity and needle stable carbon isotope composition(δ^(13)C)were measured to assess instantaneous water use efficiency(WUE_(inst))and long-term water use efficiency(WUE_(i)).Multiple regression models and structural equation modelling(SEM)identified the effects of soil properties and physiological performances on WUE_(inst)and WUE_(i).The results show that WUE_(inst)values among the four treatments were insignificant.However,compared with the NT stand(35.8μmol·mol^(-1)),WUE_(i)values significantly increased to 41.7μmol·mol^(-1)in the UR,50.1μmol·mol^(-1)in the LT and 46.6μmol·mol^(-1)in HT treatments,largely explained by photosynthetic capacity and soil water content.Understory removal did not change physiological performance(needle water potential and photosynthetic capacity).Thinning increased the net photosynthetic rate(A_n)but not stomatal conductance(g_s)or predawn needle water potential(ψ_(pd)),implying that the improvement in water use efficiency for thinned stands was largely driven by radiation interception than by soil water availability.In general,thinning may be an appropriate management measure to promote P.massoniana WUE to cope with seasonal droughts under future extreme climates.展开更多
Stable isotopes of carbon and oxygen variations in foraminiferal shells have been widely used in paleo-environment studies.However,studies about the shells of benthic foraminifera in methanehydrate-bearing sediments a...Stable isotopes of carbon and oxygen variations in foraminiferal shells have been widely used in paleo-environment studies.However,studies about the shells of benthic foraminifera in methanehydrate-bearing sediments as reliable geochemical proxies to reconstruct the potential methane release events in the geologic past are rare.In this study,we present the stable carbon and oxygen isotopes of fossil benthic foraminifera including one epifaunal species(Cibicidoides wuellerstorfi)and two infaunal species(Bulimina mexicana and Uvigerina peregrina)from the Site U1447 of IODP 353 Expedition to trace methane events in the Andaman Sea,where one of the thickest and deepest gas hydrate stability zones was discovered.Theδ^(13)C values of benthic foraminifera show that there are eight distinct intervals with negative values in the last~10 Myr,interpreted as a record of long-term fluctuations in methane emission.Six of these methane events occurred during the glacial sea-level lowstands in the last~1.1 Myr.We,therefore,infer that the trigger mechanism for these events might be the hydrate destabilization caused by sea level fall.The methane events that occurred at~2.11 and~5.93 Ma are more likely related to the sudden changes in sedimentation,either slide events or marked variations in sedimentation rate.展开更多
Black carbon(BC)has received increasing attention in the last 20 years because it is not only an absorbent of toxic pollutants but also a greenhouse substance,preserving fire-history records,and more importantly,actin...Black carbon(BC)has received increasing attention in the last 20 years because it is not only an absorbent of toxic pollutants but also a greenhouse substance,preserving fire-history records,and more importantly,acting as an indicator of biogeochemical cycles and global changes.By adopting an improved chemothermal oxidation method(WXY),this study reconstructed the century-scale high-resolution records of BC deposition from two fine-grained sediment cores collected from the Yellow Sea Cold Water Mass in the South Yellow Sea.The BC records were divided into five stages,which exhibited specific sequences with three BC peaks at approximately 1891,1921,and 2007 AD,representing times at which the first heavy storms appeared just after the termination of long-term droughts.The significant correlation between the times of the BC peaks in the cores and heavy storms in the area of the Huanghe(Yellow)River demonstrated that BC peaks could result from markedly strengthened sedimentation due to surface runof f,which augmented the atmospheric deposition.Stable carbon isotope analysis indicated that the evident increase in carbon isotope ratios of BC in Stage 5 might have resulted from the input of weathered rock-derived graphitic carbon cardinally induced by the annual anthropogenic modulation of water-borne sediment in the Huanghe River since 2005 AD.Numerical calculations demonstrated that the input fraction of graphitic carbon was 22.97% for Stage 5,whereas no graphitic carbon entered during Stages 1 and 3.The obtained data provide new and important understanding of the source-sink history of BC in the Yellow Sea.展开更多
Soils of the Chinese Loess Plateau(CLP)contain substantial amounts of soil inorganic carbon(SIC),as well as recent and ancient soil organic carbon(SOC).With the advent of the Anthropocene,human perturbation,including ...Soils of the Chinese Loess Plateau(CLP)contain substantial amounts of soil inorganic carbon(SIC),as well as recent and ancient soil organic carbon(SOC).With the advent of the Anthropocene,human perturbation,including excavation,has increased soil CO_(2) emission from the huge loess carbon pool.This study aims to determine the potential of loess CO_(2) emission induced by excavation.Soil CO_(2) were continuously monitored for seven years on a newly-excavated profile in the central CLP and the stable C isotope compositions of soil CO_(2) and SOC were used to identify their sources.The results showed that the soil CO_(2) concentrations ranged from 830μL·L^(-1) to 11190μL·L^(-1) with an annually reducing trend after excavation,indicating that the human excavation can induce CO_(2) production in loess profile.Theδ^(13) C of CO_(2) ranged from–21.27‰to–19.22‰(mean:–20.11‰),with positive deviation from top to bottom.The range of δ^(13)CSOC was–24.0‰to–21.1‰with an average of–23.1‰.Theδ^(13) C-CO_(2) in this study has a positive relationship with the reversed CO_(2) concentration,and it is calculated that 80.22%of the soil CO_(2) in this profile is from the microbial decomposition of SOC and 19.78%from the degasification during carbonate precipitation.We conclude that the human excavation can significantly enhance the decomposition of the ancient OC in loess during the first two years after perturbation,producing and releasing soil CO_(2) to atmosphere.展开更多
Despite the upsurge in hydrocarbon exploration in the Lake Albert Rift Basin(LARB)over the past three decades,systematic characterization of hydrocarbon compositions remains lacking,leading to uncertainties in source ...Despite the upsurge in hydrocarbon exploration in the Lake Albert Rift Basin(LARB)over the past three decades,systematic characterization of hydrocarbon compositions remains lacking,leading to uncertainties in source rock and oil generation determination.We characterized crude oil compositions and oil sand samples in the northern and southern subbasins of LARB.The relative abundance of normal and branched linear alkanes,hopanes,steranes,and aromatic hydrocarbon suggest that northern and southern hydrocarbons were deposited in anoxic to suboxic lacustrine environments and share similar biological source compositions(i.e.,a mixture of plants and aquatic algae and bacteria).Relative to southern samples,northern samples show more negative δ^(13)C values for oils,saturates and aromatics,indicating longer migration paths,and exhibit higher MPI-1,DNR-1 and 4-/1-MDBT ratios,indicating higher maturity.Between the two possible sets of source rocks(upper Miocene and Jurassic strata),the positive δ^(13)C values of saturated hydrocarbons(average=-20.5‰)suggest that the upper Miocene lacustrine shale is the most likely candidate.Oleanane index(<5% in our samples)does not exclude either source rock possibility,and C_(28)/C_(29) regular sterane(average=0.63)may be biased by high terrestrial inputs in a lacustrine setting.Together,our data show that northern and southern oils originate from the same source rocks but different oil kitchens.Given the similar geochemical characteristics of southern and northern oils,previous exploration successes in the northern subbasin likely suggest similar potential in the southern sector,while other elements influencing exploration success must be also evaluated.展开更多
Isotopic signature is a powerful tool to discriminate methane(CH_(4)) source types and constrain regional and global scale CH_(4) budgets.Peatlands on the Qinghai-Tibetan Plateau are poorly understood about the isotop...Isotopic signature is a powerful tool to discriminate methane(CH_(4)) source types and constrain regional and global scale CH_(4) budgets.Peatlands on the Qinghai-Tibetan Plateau are poorly understood about the isotopic signature of CH_(4) due to the limited experimental conditions.In this study,three campaigns of diurnal air samples spacing 2-3 h were taken from an alpine peatland on the eastern Qinghai-Tibetan Plateau to investigate its source signal characteristics.Both CH_(4) concentration and its stable carbon isotope(δ^(13)C-CH_(4)) were measured to derive the carbon isotopic signature of the CH_(4) source using the Keeling plot technique.Diurnal variation patterns in CH_(4) concentration and δ^(13)C-CH_(4) were observed during summertime,with depleted δ^(13)C-CH_(4) signals and high CH_(4) concentration appearing at nighttime.The δ^(13)C-CH4 signature during summer was calculated to be-71 % ± 1.3%,which falls within the range of other wetland studies and close to high-latitude peatlands.The boundary layer dynamic and CH_(4) source were supposed to influence the measured CH_(4) concentration and δ^(13)C-CH_(4.)Further investigations of CH_(4) isotopic signals into the nongrowing season are still needed to constrain the δ^(13)C-CH_(4) signature and its environmental controls in this region.展开更多
Early Eocene hyperthermals are geologically short-lived global warming events and represent fundamental perturbations to the global carbon cycle and the Earth’s ecosystem due to massive additions of isotopically ligh...Early Eocene hyperthermals are geologically short-lived global warming events and represent fundamental perturbations to the global carbon cycle and the Earth’s ecosystem due to massive additions of isotopically light carbon to the ocean-atmosphere system.They serve as ancient analogs for understanding how the oceanic carbonate system and surface-ocean ecosystem would respond to ongoing and future climate change.Here,we present a continuous carbonate record across the Eocene Thermal Maximum 2(ETM2 or H1,ca.54.1 Ma)and H2(ca.54 Ma)events from an expanded section at Ocean Drilling Program Site 1258 in tropical Atlantic.The abundant calcareous nannofossils and moderate carbonate content throughout the studied interval suggest this record was deposited above the calcite compensation depth(CCD),but below the lysocline and under the influence of terrestrial dilution.An Earth system model cGENIE is used to simulate the carbon cycle dynamics across the ETM2 and H2 to offer insights on the mechanism of the rapid warming and subsequent recovery in climate and ecosystem.The model suggests moderate changes in ocean pH(0.1–0.2 unit)for the two scenarios,biogenic methane from a rechargeable methane capacitor and organic matter oxidation from thawing of the permafrost.These pH changes are consistent with a recent independent pH estimate across the ETM2 using boron isotopes.The carbon emission flux during the ETM2 is at least an order of magnitude smaller than that during the Paleocene–Eocene Thermal Maximum(PETM)(0.015–0.05 Pg C yr^(-1)vs.0.3–1.7 Pg C yr^(-1)).The comparable pre-and post-event carbonate contents suggest the lysocline did not over deepen following the ETM2 at this tropical Atlantic site,indicating spatial heterogeneity in the carbonate system due to strong dilution influence from terrestrial weathering and riverine discharge at Site 1258.展开更多
Based on long-term dynamic tracing of dissolved inorganic carbon(DIC)and stable carbon isotope(δ13CDIC)in produced water from 20 coalbed methane(CBM)wells in western Guizhou,the spatial-temporal dynamic variations of...Based on long-term dynamic tracing of dissolved inorganic carbon(DIC)and stable carbon isotope(δ13CDIC)in produced water from 20 coalbed methane(CBM)wells in western Guizhou,the spatial-temporal dynamic variations ofδ13CDIC of the GP well group produced in multi-layer commingled manner were analyzed,and the relationship between the value ofδ13CDIC and CBM productivity was examined.The produced water samples of typical wells in the GP well group were amplified and sequenced using 16S rDNA,and a geological response model ofδ13CDIC in produced water from CBM wells with multi-coal seams was put forward.The research shows that:δ13CDIC in produced water from medium-rank coal seams commonly show positive anomalies,the produced water contains more than 15 species of methanogens,and Methanobacterium is the dominant genus.The dominant methanogens sequence numbers in the produced water are positively correlated withδ13CDIC,and the positive anomaly of v is caused by reduction of methanogens,and especially hydrogenotrophic methanogens.Vertical segmentation of sedimentary facies and lithology in stratum with multi-coal seams will result in permeability and water cut segmentation,which will lead to the segmentation ofδ13CDIC and archaea community in produced water,so in the strata with better permeability and high water cut,theδ13CDIC of the produced water is abnormally enriched,and the dominant archaea is mainly Methanobacterium.In the strata with weak permeability and low water cut,theδ13CDIC of the produced water is small,and the microbial action is weak.The shallow layer close to the coal seam outcrop is likely to be affected by meteoric precipitation,so theδ13CDIC of the produced water is smaller.The geological response model ofδ13CDIC in produced water from multi-coal seams CBM wells in the medium-rank coal reveals the geological mechanism and microbial action mechanism of theδ13CDIC difference in the produced water from the multi-coal seams CBM wells.It also provides effective geochemical evidence for the superimposed fluid system controlled by sedimentary facies,and can also be used for the contribution analysis of the produced gas and water by the multi-layer CBM wells.展开更多
The fall armyworm(FAW),Spodoptera frugiperda(J.E.Smith),is an important agricultural pest with a strong migratory ability.While the species is native to the Americas,it has recently invaded China,ravaging crops in man...The fall armyworm(FAW),Spodoptera frugiperda(J.E.Smith),is an important agricultural pest with a strong migratory ability.While the species is native to the Americas,it has recently invaded China,ravaging crops in many provinces(autonomous regions,municipalities).Its long-distance migration,which is critical to understand for pest management programs,has been well studied in its native region.In other regions however,the moth’s migration patterns have not yet been characterized.Here,the migratory behavior of FAW populations in China was studied on an isolated island located in the center of the Bohai Strait from spring to autumn 2019,the year in which FAW first reached this region,by using searchlight trapping,stable carbon isotopes and trajectory simulation.The main results were summarized as follows:(i)The number of FAW moths caught by searchlight trapping provided direct evidence that the species migrated across the Bohai Sea.(ii)Species identification was confirmed by both morphology and molecular methods,and only the"corn-strain"that preferentially infests maize and sorghum was found in the collections.(iii)Stable carbon isotope measurements showed that up to 95.07%of captured moths displayed the C4 isotope signature,thus providing additional evidence that this species is a migrant as there are no major C4 plants at the trapping site.(iv)Backward trajectory analysis indicated that the pest now threatens to expand its range into the agriculturally important region of Northeast China,and thus authorities in this region should be vigilant to the threat posed by this species.Together,these findings add to our knowledge concerning the occurrence of FAW in northern China,and will help us to develop sustainable and effective monitoring,forecasting,and pest management strategies.展开更多
A static flux chamber method was applied to study natural emissions of methane into the atmosphere in the Yakela condensed oil/gas field in Talimu Basin, Xinjiang, China. Using an online method, which couples a gas ch...A static flux chamber method was applied to study natural emissions of methane into the atmosphere in the Yakela condensed oil/gas field in Talimu Basin, Xinjiang, China. Using an online method, which couples a gas chromatography/high-temperature conversion/isotope ratio mass spectrometry (GC/C/MS) together, the 13C/12C ratios of methane in the flux chambers were measured. The results demonstrated that methane gases were liable to migrate from deep oil/gas reservoir to the surface through microseepage and pervasion, and that a part of the migrated methane that remained unoxidized could emit into the atmosphere. Methane emission rates varied less in the oil/gas field because the whole region was homogeneous in geology and geography, with a standard deviation of less than 0.02 mg/(m2·h). These were the differences in methane emission flux in the day and at night in the oil/gas field. The maximum methane emission flux reached 0.15 mg/(m2·h) at 5:00-6:00 early in the morning, and then decreased gradually. The minimum was shown 0.10 mg/(m2·h) at 17:00-18:00 in the afternoon, and then increased gradually. The daily methane released flux of the study area was 2.89 mg/(m2·d), with a standard deviation of 0.43 mg/(m2·d), using the average methane flux of every hour in a day for all chambers. δ13C of methane increased with the increase of methane concentration in the flux chambers, further indicating that the pyrogenetic origin of methane was come from deep oil/gas reservoirs.展开更多
The Juhugeng Sag,located in northwest of the Muli Basin,Tibetan Plateau,has been investigated for coal and petroleum resources during the past several decades.There have been successful recoveries of gas hydrates duri...The Juhugeng Sag,located in northwest of the Muli Basin,Tibetan Plateau,has been investigated for coal and petroleum resources during the past several decades.There have been successful recoveries of gas hydrates during recent years from the Middle Jurassic Yaojie Formation that offer insight into the origin of the hydrocarbon gases from the complex sag feature.This study examines the organic geochemical and stable carbon isotopic characteristics of shale and coal samples from the Middle Jurassic Yaojie Formation of the Juhugeng Sag,as well as compares with carbon isotopes,gas amounts and components of hydrate-bound gas.A total of 19 samples from surface mining,including 12 samples of black shale and 7 samples of coal,were analysed using a micro-photometer,a gas chromatograph,Rock–Eval and isotope methods.All the shale samples contained 100%type I kerogen,and the random vitrinite reflectance values vary from 0.65%to 1.32%and achieve thermal pyrolysis phase.Isotope values of methane(δ13C ranging from−52.6‰to−39.5‰andδD ranging from−285‰to−227‰)in the hydrate bound gases suggest that the methane originates mainly from thermogenic contributions.It is proposed that ethane from the gas hydrate is thermogenic-produced,and this conjecture is supported by the fact that most of the gas hydrate also contains more than 30%of thermogenic C2+hydrocarbons and is similar to structure II hydrate.Carbon isotope data from the gas hydrates show a positive carbon isotope series(δ13C1<δ13C2<δ13C3),with ethaneδ13C values being lighter than−28.5‰,as high consistency with source rocks from the Jurassic period indicate thermal oil-prone gas.A model of the accumulation of gas hydrate is plotted.However,the gaseous sources of gas hydrates may be a subject for more research.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
Geochemical studies of crude oil and source rock play an important role in future exploration in Zhanhua Depression.In this study,thirty-one oil samples collected from Shahejie Formation in Zhanhua Depression,Bohai Ba...Geochemical studies of crude oil and source rock play an important role in future exploration in Zhanhua Depression.In this study,thirty-one oil samples collected from Shahejie Formation in Zhanhua Depression,Bohai Bay Basin,NE China have been geochemically analyzed and their organic geochemical characteristics have been applied to differentiate groups of oils.These oil samples can be classified into two families based on multiple biomarker proxies and stable carbon isotopic values.FamilyⅠis characterized by a low ratio of pristane over phytane(Pr/Ph<0.7),a relatively high ratio of phytane over n-C18(Ph/n-C18),varying ratios of gammacerane over C30 hopane(Ga/C30H)and C22/C21 tricyclic terpane,and a low ratio of C19/C23 tricyclic terpane.FamilyⅡis marked by a relatively high Pr/Ph ratio(0.7-1.6),relative low ratios of Ph/n-C18 and C22/C21 tricyclic terpane,and avarying ratio of C19/C23 tricyclic terpane.Both familiesⅠandⅡwithin these crude oils can be subdivided into two families based on different values of stable carbon isotopic composition of individual n-alkanes.Moreover,the potential source rocks of oil samples in FamilyⅠand FamilyⅡwere likely derived from the upper Es4 member and Es3 member,respectively,based on the correlation of organic geochemical characteristics of the oils and source rocks.The results of oil-source rock correlation provide insight into the process from oil generation to migration and to final accumulation,providing a better understanding of factors controlling oil-gas distribution for prediction of sweet spots.展开更多
Monoculture of sea cucumber(pond S) and polyculture of shrimp with sea cucumber(pond SS) were established to evaluate the effect of shrimp on the environmental conditions of sea cucumber farming pond. Contributions of...Monoculture of sea cucumber(pond S) and polyculture of shrimp with sea cucumber(pond SS) were established to evaluate the effect of shrimp on the environmental conditions of sea cucumber farming pond. Contributions of sediment organic matter(SOM2) resuspended from benthic sediment and the suspended particulate organic matter(SPOM) deposited from the water column to the precipitated organic matter(SOM1) collected with sediment traps were estimated with carbon stable isotope analysis. The results showed that the levels of SPOM and SOM2 in pond SS significantly decreased in comparison with those in pond S at the end of experiment(P < 0.05), indicating that co-culturing shrimp in sea cucumber farming pond could purify the farming water. Carbon stable isotope analysis showed that the proportion of SOM2 in SOM1 in pond SS(84.97% ± 0.38%) was significantly lower than that in pond S(95.20% ± 0.30%)(P < 0.05), suggesting that the resuspension of organic matter from benthic sediment into overlying water was reduced in polyculture pond. In contrast, the proportion of SPOM in SOM1 in pond SS(15.03% ± 0.38%) was significantly higher than that in pond S(4.80% ± 0.30%)(P < 0.05), indicating that the sedimentation of SPOM from water column was enhanced in pond SS owing to the biodeposition effect of shrimp.展开更多
Inland waters are important sources of greenhouse gases(GHGs)to the atmosphere that may partially offset the terrestrial carbon sink.However,GHG emissions from high altitude saline lakes on the Tibetan Plateau are cur...Inland waters are important sources of greenhouse gases(GHGs)to the atmosphere that may partially offset the terrestrial carbon sink.However,GHG emissions from high altitude saline lakes on the Tibetan Plateau are currently poorly constrained.In this study,we measured methane(CH_(4))and carbon dioxide(CO_(2))concentrations and their carbon stable isotope(δ13C),and calculated diffusive water-to-air fluxes from two saline high-altitude lakes,Qinghai Lake and Hala Lake,located in northeast Tibetan Plateau in October 2020.The two lakes were mostly supersaturated in CH_(4)(89.8%-4623.9%sat)and acted as sources of CH_(4) to the atmosphere.Conversely,more than 96%investigated area of Qinghai Lake and all investigated area of Hala Lake was a sink of CO_(2).The average diffusive fluxes of CH_(4) and CO_(2) in the surface waters of Qinghai Lake were 34.51μmol m−2 d−1 and−1.29 mmol m−2 d−1,while diffusive fluxes of CH_(4) and CO_(2) in Hala Lake averaged 5.48μmol m−2 d−1 and−5.24 mmol m−2 d−1,respectively.Salinity(Sal),fluorescent dissolved organic matter(fDOM),temperature(Temp)and dissolved oxygen(DO)are key factors for diffusive CH_(4) and CO_(2) flux in Qinghai Lake and Hala Lake.CH_(4) diffusive fluxes across water-air interface from Qinghai Lake and Hala Lake were found to be significantly lower than other freshwater lakes,likely due to their saline nature.A simple isotope mixing model(Miller-Tans plots)revealed a distinctly different isotopic source values of CO_(2) and CH_(4) in Qinghai Lake and Hala Lake.The CH_(4) production pathway of Qinghai Lake was mainly by the acetate fermentation,while that of Hala Lake was mainly by the CO_(2) reduction.The results show that the continuous measurement can help capture the spatial variability of GHGs fluxes in saline lakes.展开更多
The scaling of the energetic cost of locomotion with body mass is well documented at the interspecific level.However,methodological restrictions limit our understanding of the scaling of flight metabolic rate(MR)in fr...The scaling of the energetic cost of locomotion with body mass is well documented at the interspecific level.However,methodological restrictions limit our understanding of the scaling of flight metabolic rate(MR)in free-flying insects.This is particularly true at the intraspecific level,where variation in body mass and flight energetics may have direct consequences for the fitness of an individual.We applied a 13C stable isotope method to investigate the scaling of MR with body mass during free-flight in the beetle Batocera rufomaculata.This species exhibits large intraspecific variation in adult body mass as a consequence of the environmental conditions during larval growth.We show that the flight-MR scales with body mass to the power of 0.57,with smaller conspecifics possessing up to 2.3 fold higher mass-specific flight MR than larger ones.Whereas the scaling exponent of free-flight MR was found to be like that determined for tethered-flight,the energy expenditure during free-flight was more than 2.7 fold higher than for tethered-flight.The metabolic cost of flight should therefore be studied under free-flight conditions,a requirement now enabled by the 13C technique described herein for insect flight.展开更多
Continental organic-rich shales are well developed in the Dameigou Formation within the Yuka Depression of the Qaidam Basin. Here, the Rock-Eval pyrolysis, biomarkers, organic petrology, and stable carbon isotope have...Continental organic-rich shales are well developed in the Dameigou Formation within the Yuka Depression of the Qaidam Basin. Here, the Rock-Eval pyrolysis, biomarkers, organic petrology, and stable carbon isotope have been carried out on the Middle Jurassic Dameigou Formation source rocks from the northwest part of Yuka Depression, Qaidam Basin in order to study their thermal maturity, source of organic matter(OM), and palaeoenvironment changes. The Rock-Eval pyrolysis data(e.g., T_(max)), vitrinite reflectance, and biomarker-derived thermal maturity parameters(e.g., carbon preference index, Ts/(Ts+Tm), C_(29)Ts/(C_(29)Ts+C_(29)αβ hopane), C_(30) αβ/(αβ+βα) hopanes, C_(29)ααα 20S/(20S+20R) steranes, and C_(29)αββ/(αββ+ααα) steranes) suggest all studied samples stay between immature and low mature stage. The maceral compositions, stable carbon isotope compositions, n-alkane distributions, and biomarker-derived source parameters(e. g., C_(27)/C_(29)ααα 20R sterane, ternary diagram of C_(27)-C28-C_(29)steranes, C24 tetracyclic terpane) indicate both aquatic organisms and higher plants are the source of OM in the shales, but land plants are dominant. Generally low gammacerane concentration and environment-related parameters(e. g., cross-plots of C_(27)/C_(29)ααα 20R sterane vs. Pr/Ph) indicate these source rocks may be derived from lacustrine and fluvial-deltaic environments with fresh water, which is also supported by the variations of stable carbon isotopes from OM in the source rocks. However, the stable carbon isotope compositions of OM in the source rocks were influenced by multiple factors(e.g., source types and depositional environment) in the Yuka Depression. Slightly brackish condition is recorded in the upper part of the ZK6-1 well favor the formation of lacustrine algae, as confirmed by high contents of C_(27) steranes and short-chain n-alkanes. The variation of reducing to oxidizing condition of study area is possibly associated with the periodical flooded river-influenced aquatic condition during the deposition of the Middle Jurassic Dameigou Formation.展开更多
Scleractinian corals exhibit a dual trophic pattern of autotrophic photosynthesis and heterotrophic predation.However,whether corals can adjust their trophic status under contrasting environmental conditions remains u...Scleractinian corals exhibit a dual trophic pattern of autotrophic photosynthesis and heterotrophic predation.However,whether corals can adjust their trophic status under contrasting environmental conditions remains unclear.In our study,70 scleractinian corals(Favia palauensis)were collected from Sanya and the Xisha and Nansha Islands in the South China Sea.We measured the zooxanthellae density(ZD)andδ^(13)C of zooxanthellae(δ^(13)C_(z))and host tissue(δ^(13)C_(h))and analyzed the difference betweenδ^(13)C_(h) andδ^(13)C_(z)(i.e.,△^(h-z)^(13)C).The relatively high ZD andδ^(13)C_(z) values in the samples from Sanya indicate that these corals might have higher photosynthetic rates and autotrophic abilities than those from Xisha and Nansha.In contrast,the relatively lowδ^(13)C_(h) and△^(h-z)^(13)C values in the samples from Xisha and Nansha suggest that these corals might have a higher heterotrophic ability than those from Sanya.In addition,we tested the coral tissue biomass and skeletalδ^(13)C(δ^(13)C_(s))in the samples from Sanya and examined their correlations with△^(h-z)^(13)C.The results showed a negative correlation,indicating that the more the organic material produced by the coral,the stronger its heterotrophic ability.Our results show that corals can adjust their trophic status under different environmental and physiological conditions,which is essential for increasing their adaptability to different environmental conditions.展开更多
Rice planting(RP)is significant to methane(CH4_(4))emissions from paddy fields,but its effect on the relative contribution of the acetoclastic methanogenesis to total CH4_(4) production(F_(ac))and the fraction of CH4_...Rice planting(RP)is significant to methane(CH4_(4))emissions from paddy fields,but its effect on the relative contribution of the acetoclastic methanogenesis to total CH4_(4) production(F_(ac))and the fraction of CH4_(4) oxidized(Fox)is poorly understood.To quantify the responses of the F_(ac) and Fox to RP,we investigated CH4_(4) fluxes,CH4_(4) production and oxidation potentials,dissolved CH4_(4) concentrations,and their stable carbon isotopes in a flooded paddy soil.The mcrA and pmoA gene copies were also determined by quantitative polymerase chain reaction(qPCR).Compared with the unplanted soil(control,CK),the seasonal CH4_(4) emissions from the planted soil were significantly enhanced,13.6 times,resulting in large decreases in the CH4_(4) concentrations in the soil solution.This indicated that much more CH4_(4) was released into the atmosphere by the RP than was stored in the soils.Acetoclastic methanogenesis became more important from the tillering stage(TS)to the ripening stage(RS)for the CK,with F_(ac) values increased from 17%-20% to 46%-55%.With RP,the F_(ac) values were enhanced by 10%-20%,and it significantly increased the copy numbers of the mcrA gene at the four rice stages(TS,booting stage(BS),grain-filling stage(GS),and RS).Furthermore,the effect of the RP on the abundance of the mcrA gene was highly concurrent with the effect on the F_(ac) values.At the TS,the Fox values at the soil-water interface were around 50%-75% for the CK,being 15%-20% lower than those of the RP in the rhizosphere.It increased to 65%-100% at the GS,but was reduced by 20%-30% after the RP.These differences might be because the copy numbers of the pmoA gene were significantly raised at the TS while lowered at the GS by the RP.This was further demonstrated by the strong correlations between the effect of the RP on the abundance of the pmoA gene and the effect on the Fox values.These findings suggest that RP markedly impacts on the abundances of the mcrA and pmoA genes,affecting the pathway of CH4_(4) production and the fraction of CH4_(4) oxidization,respectively.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
基金supported by the National Key Research and Development Program of China(2016YFD0600201)the National Nonprofit Institute Research Grant of CAF(CAFYBB2017ZB003)+1 种基金the National Natural Science Foundation of China(3187071631670720)。
文摘Understanding the relationship between forest management and water use efficiency(WUE)is important for evaluating forest adaptability to climate change.However,the effects of thinning and understory removal on WUE and its key controlling processes are not well understood,which limits our comprehension of the physiological mechanisms of various management practices.In this study,four forest management measures(no thinning:NT;understory removal:UR;light thinning:LT;and heavy thinning:HT)were carried out in Pinus massoniana plantations in a subtropical region of China.Photosynthetic capacity and needle stable carbon isotope composition(δ^(13)C)were measured to assess instantaneous water use efficiency(WUE_(inst))and long-term water use efficiency(WUE_(i)).Multiple regression models and structural equation modelling(SEM)identified the effects of soil properties and physiological performances on WUE_(inst)and WUE_(i).The results show that WUE_(inst)values among the four treatments were insignificant.However,compared with the NT stand(35.8μmol·mol^(-1)),WUE_(i)values significantly increased to 41.7μmol·mol^(-1)in the UR,50.1μmol·mol^(-1)in the LT and 46.6μmol·mol^(-1)in HT treatments,largely explained by photosynthetic capacity and soil water content.Understory removal did not change physiological performance(needle water potential and photosynthetic capacity).Thinning increased the net photosynthetic rate(A_n)but not stomatal conductance(g_s)or predawn needle water potential(ψ_(pd)),implying that the improvement in water use efficiency for thinned stands was largely driven by radiation interception than by soil water availability.In general,thinning may be an appropriate management measure to promote P.massoniana WUE to cope with seasonal droughts under future extreme climates.
基金supported by the National Key R&D Program of China(No.2018YFC031000404)the National Natural Science Foundation of China(No.42276068)State Key Laboratory of Marine Geology,Tongji University(No.MGK202206)。
文摘Stable isotopes of carbon and oxygen variations in foraminiferal shells have been widely used in paleo-environment studies.However,studies about the shells of benthic foraminifera in methanehydrate-bearing sediments as reliable geochemical proxies to reconstruct the potential methane release events in the geologic past are rare.In this study,we present the stable carbon and oxygen isotopes of fossil benthic foraminifera including one epifaunal species(Cibicidoides wuellerstorfi)and two infaunal species(Bulimina mexicana and Uvigerina peregrina)from the Site U1447 of IODP 353 Expedition to trace methane events in the Andaman Sea,where one of the thickest and deepest gas hydrate stability zones was discovered.Theδ^(13)C values of benthic foraminifera show that there are eight distinct intervals with negative values in the last~10 Myr,interpreted as a record of long-term fluctuations in methane emission.Six of these methane events occurred during the glacial sea-level lowstands in the last~1.1 Myr.We,therefore,infer that the trigger mechanism for these events might be the hydrate destabilization caused by sea level fall.The methane events that occurred at~2.11 and~5.93 Ma are more likely related to the sudden changes in sedimentation,either slide events or marked variations in sedimentation rate.
基金Supported by the National Basic Research Program of China(973 Program)(No.2012CB956004)the Fundamental Research Funds for the Central Universities(No.16lgjc22)
文摘Black carbon(BC)has received increasing attention in the last 20 years because it is not only an absorbent of toxic pollutants but also a greenhouse substance,preserving fire-history records,and more importantly,acting as an indicator of biogeochemical cycles and global changes.By adopting an improved chemothermal oxidation method(WXY),this study reconstructed the century-scale high-resolution records of BC deposition from two fine-grained sediment cores collected from the Yellow Sea Cold Water Mass in the South Yellow Sea.The BC records were divided into five stages,which exhibited specific sequences with three BC peaks at approximately 1891,1921,and 2007 AD,representing times at which the first heavy storms appeared just after the termination of long-term droughts.The significant correlation between the times of the BC peaks in the cores and heavy storms in the area of the Huanghe(Yellow)River demonstrated that BC peaks could result from markedly strengthened sedimentation due to surface runof f,which augmented the atmospheric deposition.Stable carbon isotope analysis indicated that the evident increase in carbon isotope ratios of BC in Stage 5 might have resulted from the input of weathered rock-derived graphitic carbon cardinally induced by the annual anthropogenic modulation of water-borne sediment in the Huanghe River since 2005 AD.Numerical calculations demonstrated that the input fraction of graphitic carbon was 22.97% for Stage 5,whereas no graphitic carbon entered during Stages 1 and 3.The obtained data provide new and important understanding of the source-sink history of BC in the Yellow Sea.
基金funded by National Natural Science Foundation of China(Grant No.41877398)the Basic Science Research Fund from the Institute of Chinese Academy of Geological Sciences(Grant No.SK201911)the Belt and Road Fund on Water and Sustainability(U2019NKMS01)。
文摘Soils of the Chinese Loess Plateau(CLP)contain substantial amounts of soil inorganic carbon(SIC),as well as recent and ancient soil organic carbon(SOC).With the advent of the Anthropocene,human perturbation,including excavation,has increased soil CO_(2) emission from the huge loess carbon pool.This study aims to determine the potential of loess CO_(2) emission induced by excavation.Soil CO_(2) were continuously monitored for seven years on a newly-excavated profile in the central CLP and the stable C isotope compositions of soil CO_(2) and SOC were used to identify their sources.The results showed that the soil CO_(2) concentrations ranged from 830μL·L^(-1) to 11190μL·L^(-1) with an annually reducing trend after excavation,indicating that the human excavation can induce CO_(2) production in loess profile.Theδ^(13) C of CO_(2) ranged from–21.27‰to–19.22‰(mean:–20.11‰),with positive deviation from top to bottom.The range of δ^(13)CSOC was–24.0‰to–21.1‰with an average of–23.1‰.Theδ^(13) C-CO_(2) in this study has a positive relationship with the reversed CO_(2) concentration,and it is calculated that 80.22%of the soil CO_(2) in this profile is from the microbial decomposition of SOC and 19.78%from the degasification during carbonate precipitation.We conclude that the human excavation can significantly enhance the decomposition of the ancient OC in loess during the first two years after perturbation,producing and releasing soil CO_(2) to atmosphere.
基金funded by National Natural Science Foundation of China(Grant No.42072149)support of US National Science Foundation grant(Grant No.EAR-1255724)。
文摘Despite the upsurge in hydrocarbon exploration in the Lake Albert Rift Basin(LARB)over the past three decades,systematic characterization of hydrocarbon compositions remains lacking,leading to uncertainties in source rock and oil generation determination.We characterized crude oil compositions and oil sand samples in the northern and southern subbasins of LARB.The relative abundance of normal and branched linear alkanes,hopanes,steranes,and aromatic hydrocarbon suggest that northern and southern hydrocarbons were deposited in anoxic to suboxic lacustrine environments and share similar biological source compositions(i.e.,a mixture of plants and aquatic algae and bacteria).Relative to southern samples,northern samples show more negative δ^(13)C values for oils,saturates and aromatics,indicating longer migration paths,and exhibit higher MPI-1,DNR-1 and 4-/1-MDBT ratios,indicating higher maturity.Between the two possible sets of source rocks(upper Miocene and Jurassic strata),the positive δ^(13)C values of saturated hydrocarbons(average=-20.5‰)suggest that the upper Miocene lacustrine shale is the most likely candidate.Oleanane index(<5% in our samples)does not exclude either source rock possibility,and C_(28)/C_(29) regular sterane(average=0.63)may be biased by high terrestrial inputs in a lacustrine setting.Together,our data show that northern and southern oils originate from the same source rocks but different oil kitchens.Given the similar geochemical characteristics of southern and northern oils,previous exploration successes in the northern subbasin likely suggest similar potential in the southern sector,while other elements influencing exploration success must be also evaluated.
基金financially supported by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No.XDB40010000)the National Natural Science Foundation of China (Grant Nos.41907288,41673119,and 41773140)+1 种基金the Science and Technology Foundation of Guizhou Province (Grant Nos.[2019]1317 and [2020]1Y193)supported by the“Light of West China”Program and the CAS Scholarship。
文摘Isotopic signature is a powerful tool to discriminate methane(CH_(4)) source types and constrain regional and global scale CH_(4) budgets.Peatlands on the Qinghai-Tibetan Plateau are poorly understood about the isotopic signature of CH_(4) due to the limited experimental conditions.In this study,three campaigns of diurnal air samples spacing 2-3 h were taken from an alpine peatland on the eastern Qinghai-Tibetan Plateau to investigate its source signal characteristics.Both CH_(4) concentration and its stable carbon isotope(δ^(13)C-CH_(4)) were measured to derive the carbon isotopic signature of the CH_(4) source using the Keeling plot technique.Diurnal variation patterns in CH_(4) concentration and δ^(13)C-CH_(4) were observed during summertime,with depleted δ^(13)C-CH_(4) signals and high CH_(4) concentration appearing at nighttime.The δ^(13)C-CH4 signature during summer was calculated to be-71 % ± 1.3%,which falls within the range of other wetland studies and close to high-latitude peatlands.The boundary layer dynamic and CH_(4) source were supposed to influence the measured CH_(4) concentration and δ^(13)C-CH_(4.)Further investigations of CH_(4) isotopic signals into the nongrowing season are still needed to constrain the δ^(13)C-CH_(4) signature and its environmental controls in this region.
基金This study was supported by the National Natural Science Foundation of China(Grant Nos.41976045&41888101)and the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)through a group research project(99147-42080024).Y.Cui is supported by the U.S.National Science Foundation award 1603051.Samples and core data were provided by ODP.ODP is sponsored by the U.S.National Science Foundation(NSF)and participating countries under management of Joint Oceanographic Institutions(JOI),Inc.
文摘Early Eocene hyperthermals are geologically short-lived global warming events and represent fundamental perturbations to the global carbon cycle and the Earth’s ecosystem due to massive additions of isotopically light carbon to the ocean-atmosphere system.They serve as ancient analogs for understanding how the oceanic carbonate system and surface-ocean ecosystem would respond to ongoing and future climate change.Here,we present a continuous carbonate record across the Eocene Thermal Maximum 2(ETM2 or H1,ca.54.1 Ma)and H2(ca.54 Ma)events from an expanded section at Ocean Drilling Program Site 1258 in tropical Atlantic.The abundant calcareous nannofossils and moderate carbonate content throughout the studied interval suggest this record was deposited above the calcite compensation depth(CCD),but below the lysocline and under the influence of terrestrial dilution.An Earth system model cGENIE is used to simulate the carbon cycle dynamics across the ETM2 and H2 to offer insights on the mechanism of the rapid warming and subsequent recovery in climate and ecosystem.The model suggests moderate changes in ocean pH(0.1–0.2 unit)for the two scenarios,biogenic methane from a rechargeable methane capacitor and organic matter oxidation from thawing of the permafrost.These pH changes are consistent with a recent independent pH estimate across the ETM2 using boron isotopes.The carbon emission flux during the ETM2 is at least an order of magnitude smaller than that during the Paleocene–Eocene Thermal Maximum(PETM)(0.015–0.05 Pg C yr^(-1)vs.0.3–1.7 Pg C yr^(-1)).The comparable pre-and post-event carbonate contents suggest the lysocline did not over deepen following the ETM2 at this tropical Atlantic site,indicating spatial heterogeneity in the carbonate system due to strong dilution influence from terrestrial weathering and riverine discharge at Site 1258.
基金Supported by the National Natural Science Foundation of China(41772155)the National Science and Technology Major Project of China(2016ZX05044-002)
文摘Based on long-term dynamic tracing of dissolved inorganic carbon(DIC)and stable carbon isotope(δ13CDIC)in produced water from 20 coalbed methane(CBM)wells in western Guizhou,the spatial-temporal dynamic variations ofδ13CDIC of the GP well group produced in multi-layer commingled manner were analyzed,and the relationship between the value ofδ13CDIC and CBM productivity was examined.The produced water samples of typical wells in the GP well group were amplified and sequenced using 16S rDNA,and a geological response model ofδ13CDIC in produced water from CBM wells with multi-coal seams was put forward.The research shows that:δ13CDIC in produced water from medium-rank coal seams commonly show positive anomalies,the produced water contains more than 15 species of methanogens,and Methanobacterium is the dominant genus.The dominant methanogens sequence numbers in the produced water are positively correlated withδ13CDIC,and the positive anomaly of v is caused by reduction of methanogens,and especially hydrogenotrophic methanogens.Vertical segmentation of sedimentary facies and lithology in stratum with multi-coal seams will result in permeability and water cut segmentation,which will lead to the segmentation ofδ13CDIC and archaea community in produced water,so in the strata with better permeability and high water cut,theδ13CDIC of the produced water is abnormally enriched,and the dominant archaea is mainly Methanobacterium.In the strata with weak permeability and low water cut,theδ13CDIC of the produced water is small,and the microbial action is weak.The shallow layer close to the coal seam outcrop is likely to be affected by meteoric precipitation,so theδ13CDIC of the produced water is smaller.The geological response model ofδ13CDIC in produced water from multi-coal seams CBM wells in the medium-rank coal reveals the geological mechanism and microbial action mechanism of theδ13CDIC difference in the produced water from the multi-coal seams CBM wells.It also provides effective geochemical evidence for the superimposed fluid system controlled by sedimentary facies,and can also be used for the contribution analysis of the produced gas and water by the multi-layer CBM wells.
基金funded by the National Natural Science Foundation of China(31901873 and 31727901)the Central Public-interest Scientific Institution Basal Research Fund,China(CAAS-ZDRW202007)。
文摘The fall armyworm(FAW),Spodoptera frugiperda(J.E.Smith),is an important agricultural pest with a strong migratory ability.While the species is native to the Americas,it has recently invaded China,ravaging crops in many provinces(autonomous regions,municipalities).Its long-distance migration,which is critical to understand for pest management programs,has been well studied in its native region.In other regions however,the moth’s migration patterns have not yet been characterized.Here,the migratory behavior of FAW populations in China was studied on an isolated island located in the center of the Bohai Strait from spring to autumn 2019,the year in which FAW first reached this region,by using searchlight trapping,stable carbon isotopes and trajectory simulation.The main results were summarized as follows:(i)The number of FAW moths caught by searchlight trapping provided direct evidence that the species migrated across the Bohai Sea.(ii)Species identification was confirmed by both morphology and molecular methods,and only the"corn-strain"that preferentially infests maize and sorghum was found in the collections.(iii)Stable carbon isotope measurements showed that up to 95.07%of captured moths displayed the C4 isotope signature,thus providing additional evidence that this species is a migrant as there are no major C4 plants at the trapping site.(iv)Backward trajectory analysis indicated that the pest now threatens to expand its range into the agriculturally important region of Northeast China,and thus authorities in this region should be vigilant to the threat posed by this species.Together,these findings add to our knowledge concerning the occurrence of FAW in northern China,and will help us to develop sustainable and effective monitoring,forecasting,and pest management strategies.
基金the National Natural Sci-ence Foundation of China (No. 40273034)the Science Foundation of Hangzhou Dianzi University
文摘A static flux chamber method was applied to study natural emissions of methane into the atmosphere in the Yakela condensed oil/gas field in Talimu Basin, Xinjiang, China. Using an online method, which couples a gas chromatography/high-temperature conversion/isotope ratio mass spectrometry (GC/C/MS) together, the 13C/12C ratios of methane in the flux chambers were measured. The results demonstrated that methane gases were liable to migrate from deep oil/gas reservoir to the surface through microseepage and pervasion, and that a part of the migrated methane that remained unoxidized could emit into the atmosphere. Methane emission rates varied less in the oil/gas field because the whole region was homogeneous in geology and geography, with a standard deviation of less than 0.02 mg/(m2·h). These were the differences in methane emission flux in the day and at night in the oil/gas field. The maximum methane emission flux reached 0.15 mg/(m2·h) at 5:00-6:00 early in the morning, and then decreased gradually. The minimum was shown 0.10 mg/(m2·h) at 17:00-18:00 in the afternoon, and then increased gradually. The daily methane released flux of the study area was 2.89 mg/(m2·d), with a standard deviation of 0.43 mg/(m2·d), using the average methane flux of every hour in a day for all chambers. δ13C of methane increased with the increase of methane concentration in the flux chambers, further indicating that the pyrogenetic origin of methane was come from deep oil/gas reservoirs.
基金This study was supported by the National Natural Science Fundamental of China(No.41702144)the Fundamental Research Funds for the Central Universities(No.2652018234)+1 种基金the Key Program of exploration Foundation of Qinghai province(No.2017042007ky007)The authors wish to thank Prof.Yuzhuang Sun for his comments and suggestions to improve the manuscripts.
文摘The Juhugeng Sag,located in northwest of the Muli Basin,Tibetan Plateau,has been investigated for coal and petroleum resources during the past several decades.There have been successful recoveries of gas hydrates during recent years from the Middle Jurassic Yaojie Formation that offer insight into the origin of the hydrocarbon gases from the complex sag feature.This study examines the organic geochemical and stable carbon isotopic characteristics of shale and coal samples from the Middle Jurassic Yaojie Formation of the Juhugeng Sag,as well as compares with carbon isotopes,gas amounts and components of hydrate-bound gas.A total of 19 samples from surface mining,including 12 samples of black shale and 7 samples of coal,were analysed using a micro-photometer,a gas chromatograph,Rock–Eval and isotope methods.All the shale samples contained 100%type I kerogen,and the random vitrinite reflectance values vary from 0.65%to 1.32%and achieve thermal pyrolysis phase.Isotope values of methane(δ13C ranging from−52.6‰to−39.5‰andδD ranging from−285‰to−227‰)in the hydrate bound gases suggest that the methane originates mainly from thermogenic contributions.It is proposed that ethane from the gas hydrate is thermogenic-produced,and this conjecture is supported by the fact that most of the gas hydrate also contains more than 30%of thermogenic C2+hydrocarbons and is similar to structure II hydrate.Carbon isotope data from the gas hydrates show a positive carbon isotope series(δ13C1<δ13C2<δ13C3),with ethaneδ13C values being lighter than−28.5‰,as high consistency with source rocks from the Jurassic period indicate thermal oil-prone gas.A model of the accumulation of gas hydrate is plotted.However,the gaseous sources of gas hydrates may be a subject for more research.
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.
基金financially supported by the Chinese NSF Grants[41903064]to Hong Lu。
文摘Geochemical studies of crude oil and source rock play an important role in future exploration in Zhanhua Depression.In this study,thirty-one oil samples collected from Shahejie Formation in Zhanhua Depression,Bohai Bay Basin,NE China have been geochemically analyzed and their organic geochemical characteristics have been applied to differentiate groups of oils.These oil samples can be classified into two families based on multiple biomarker proxies and stable carbon isotopic values.FamilyⅠis characterized by a low ratio of pristane over phytane(Pr/Ph<0.7),a relatively high ratio of phytane over n-C18(Ph/n-C18),varying ratios of gammacerane over C30 hopane(Ga/C30H)and C22/C21 tricyclic terpane,and a low ratio of C19/C23 tricyclic terpane.FamilyⅡis marked by a relatively high Pr/Ph ratio(0.7-1.6),relative low ratios of Ph/n-C18 and C22/C21 tricyclic terpane,and avarying ratio of C19/C23 tricyclic terpane.Both familiesⅠandⅡwithin these crude oils can be subdivided into two families based on different values of stable carbon isotopic composition of individual n-alkanes.Moreover,the potential source rocks of oil samples in FamilyⅠand FamilyⅡwere likely derived from the upper Es4 member and Es3 member,respectively,based on the correlation of organic geochemical characteristics of the oils and source rocks.The results of oil-source rock correlation provide insight into the process from oil generation to migration and to final accumulation,providing a better understanding of factors controlling oil-gas distribution for prediction of sweet spots.
基金funded by the National Natural Science Foundation of China (Nos. 31172426 and 31372549)Ministry of Science and Technology of China (Nos. 2011BAD13B03 and 2012GA740001)supported by the Program for New Century Excellent Talents in University (NCET-11-0466)
文摘Monoculture of sea cucumber(pond S) and polyculture of shrimp with sea cucumber(pond SS) were established to evaluate the effect of shrimp on the environmental conditions of sea cucumber farming pond. Contributions of sediment organic matter(SOM2) resuspended from benthic sediment and the suspended particulate organic matter(SPOM) deposited from the water column to the precipitated organic matter(SOM1) collected with sediment traps were estimated with carbon stable isotope analysis. The results showed that the levels of SPOM and SOM2 in pond SS significantly decreased in comparison with those in pond S at the end of experiment(P < 0.05), indicating that co-culturing shrimp in sea cucumber farming pond could purify the farming water. Carbon stable isotope analysis showed that the proportion of SOM2 in SOM1 in pond SS(84.97% ± 0.38%) was significantly lower than that in pond S(95.20% ± 0.30%)(P < 0.05), suggesting that the resuspension of organic matter from benthic sediment into overlying water was reduced in polyculture pond. In contrast, the proportion of SPOM in SOM1 in pond SS(15.03% ± 0.38%) was significantly higher than that in pond S(4.80% ± 0.30%)(P < 0.05), indicating that the sedimentation of SPOM from water column was enhanced in pond SS owing to the biodeposition effect of shrimp.
基金funded by the National Natural Science Foundation of China(41801054)Beijing Normal University Talent Introduction Project(12807-312232101)+1 种基金Youth Innovation Promotion Association,CAS(2020419)Scientific Research Foundation of the Key Laboratory of Cryospheric Sciences(SKLCSZZ-2021).
文摘Inland waters are important sources of greenhouse gases(GHGs)to the atmosphere that may partially offset the terrestrial carbon sink.However,GHG emissions from high altitude saline lakes on the Tibetan Plateau are currently poorly constrained.In this study,we measured methane(CH_(4))and carbon dioxide(CO_(2))concentrations and their carbon stable isotope(δ13C),and calculated diffusive water-to-air fluxes from two saline high-altitude lakes,Qinghai Lake and Hala Lake,located in northeast Tibetan Plateau in October 2020.The two lakes were mostly supersaturated in CH_(4)(89.8%-4623.9%sat)and acted as sources of CH_(4) to the atmosphere.Conversely,more than 96%investigated area of Qinghai Lake and all investigated area of Hala Lake was a sink of CO_(2).The average diffusive fluxes of CH_(4) and CO_(2) in the surface waters of Qinghai Lake were 34.51μmol m−2 d−1 and−1.29 mmol m−2 d−1,while diffusive fluxes of CH_(4) and CO_(2) in Hala Lake averaged 5.48μmol m−2 d−1 and−5.24 mmol m−2 d−1,respectively.Salinity(Sal),fluorescent dissolved organic matter(fDOM),temperature(Temp)and dissolved oxygen(DO)are key factors for diffusive CH_(4) and CO_(2) flux in Qinghai Lake and Hala Lake.CH_(4) diffusive fluxes across water-air interface from Qinghai Lake and Hala Lake were found to be significantly lower than other freshwater lakes,likely due to their saline nature.A simple isotope mixing model(Miller-Tans plots)revealed a distinctly different isotopic source values of CO_(2) and CH_(4) in Qinghai Lake and Hala Lake.The CH_(4) production pathway of Qinghai Lake was mainly by the acetate fermentation,while that of Hala Lake was mainly by the CO_(2) reduction.The results show that the continuous measurement can help capture the spatial variability of GHGs fluxes in saline lakes.
文摘The scaling of the energetic cost of locomotion with body mass is well documented at the interspecific level.However,methodological restrictions limit our understanding of the scaling of flight metabolic rate(MR)in free-flying insects.This is particularly true at the intraspecific level,where variation in body mass and flight energetics may have direct consequences for the fitness of an individual.We applied a 13C stable isotope method to investigate the scaling of MR with body mass during free-flight in the beetle Batocera rufomaculata.This species exhibits large intraspecific variation in adult body mass as a consequence of the environmental conditions during larval growth.We show that the flight-MR scales with body mass to the power of 0.57,with smaller conspecifics possessing up to 2.3 fold higher mass-specific flight MR than larger ones.Whereas the scaling exponent of free-flight MR was found to be like that determined for tethered-flight,the energy expenditure during free-flight was more than 2.7 fold higher than for tethered-flight.The metabolic cost of flight should therefore be studied under free-flight conditions,a requirement now enabled by the 13C technique described herein for insect flight.
基金financially supported by the National Natural Science Foundation of China (Nos.42102215,41702144)the Science and Technology Research Project for Higher Education Institutions in Hebei Province (No.QN2021033)。
文摘Continental organic-rich shales are well developed in the Dameigou Formation within the Yuka Depression of the Qaidam Basin. Here, the Rock-Eval pyrolysis, biomarkers, organic petrology, and stable carbon isotope have been carried out on the Middle Jurassic Dameigou Formation source rocks from the northwest part of Yuka Depression, Qaidam Basin in order to study their thermal maturity, source of organic matter(OM), and palaeoenvironment changes. The Rock-Eval pyrolysis data(e.g., T_(max)), vitrinite reflectance, and biomarker-derived thermal maturity parameters(e.g., carbon preference index, Ts/(Ts+Tm), C_(29)Ts/(C_(29)Ts+C_(29)αβ hopane), C_(30) αβ/(αβ+βα) hopanes, C_(29)ααα 20S/(20S+20R) steranes, and C_(29)αββ/(αββ+ααα) steranes) suggest all studied samples stay between immature and low mature stage. The maceral compositions, stable carbon isotope compositions, n-alkane distributions, and biomarker-derived source parameters(e. g., C_(27)/C_(29)ααα 20R sterane, ternary diagram of C_(27)-C28-C_(29)steranes, C24 tetracyclic terpane) indicate both aquatic organisms and higher plants are the source of OM in the shales, but land plants are dominant. Generally low gammacerane concentration and environment-related parameters(e. g., cross-plots of C_(27)/C_(29)ααα 20R sterane vs. Pr/Ph) indicate these source rocks may be derived from lacustrine and fluvial-deltaic environments with fresh water, which is also supported by the variations of stable carbon isotopes from OM in the source rocks. However, the stable carbon isotope compositions of OM in the source rocks were influenced by multiple factors(e.g., source types and depositional environment) in the Yuka Depression. Slightly brackish condition is recorded in the upper part of the ZK6-1 well favor the formation of lacustrine algae, as confirmed by high contents of C_(27) steranes and short-chain n-alkanes. The variation of reducing to oxidizing condition of study area is possibly associated with the periodical flooded river-influenced aquatic condition during the deposition of the Middle Jurassic Dameigou Formation.
基金supported by the National Natural Science Foundation of China(Grant Nos.42090041,42030502&41663001)the Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology(Grant No.MGQNLMTD201801)the Guangxi Scientific Projects(Grant Nos.AD17129063,AA17204074&2020GXNSFAA297026)。
文摘Scleractinian corals exhibit a dual trophic pattern of autotrophic photosynthesis and heterotrophic predation.However,whether corals can adjust their trophic status under contrasting environmental conditions remains unclear.In our study,70 scleractinian corals(Favia palauensis)were collected from Sanya and the Xisha and Nansha Islands in the South China Sea.We measured the zooxanthellae density(ZD)andδ^(13)C of zooxanthellae(δ^(13)C_(z))and host tissue(δ^(13)C_(h))and analyzed the difference betweenδ^(13)C_(h) andδ^(13)C_(z)(i.e.,△^(h-z)^(13)C).The relatively high ZD andδ^(13)C_(z) values in the samples from Sanya indicate that these corals might have higher photosynthetic rates and autotrophic abilities than those from Xisha and Nansha.In contrast,the relatively lowδ^(13)C_(h) and△^(h-z)^(13)C values in the samples from Xisha and Nansha suggest that these corals might have a higher heterotrophic ability than those from Sanya.In addition,we tested the coral tissue biomass and skeletalδ^(13)C(δ^(13)C_(s))in the samples from Sanya and examined their correlations with△^(h-z)^(13)C.The results showed a negative correlation,indicating that the more the organic material produced by the coral,the stronger its heterotrophic ability.Our results show that corals can adjust their trophic status under different environmental and physiological conditions,which is essential for increasing their adaptability to different environmental conditions.
基金financially supported by the National Key Research and Development Program of China(No.2017YFD 0300105)the National Natural Science Foundation of China(Nos.41571232,41671241,and 41877325)+1 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(CASmember No.2018349)。
文摘Rice planting(RP)is significant to methane(CH4_(4))emissions from paddy fields,but its effect on the relative contribution of the acetoclastic methanogenesis to total CH4_(4) production(F_(ac))and the fraction of CH4_(4) oxidized(Fox)is poorly understood.To quantify the responses of the F_(ac) and Fox to RP,we investigated CH4_(4) fluxes,CH4_(4) production and oxidation potentials,dissolved CH4_(4) concentrations,and their stable carbon isotopes in a flooded paddy soil.The mcrA and pmoA gene copies were also determined by quantitative polymerase chain reaction(qPCR).Compared with the unplanted soil(control,CK),the seasonal CH4_(4) emissions from the planted soil were significantly enhanced,13.6 times,resulting in large decreases in the CH4_(4) concentrations in the soil solution.This indicated that much more CH4_(4) was released into the atmosphere by the RP than was stored in the soils.Acetoclastic methanogenesis became more important from the tillering stage(TS)to the ripening stage(RS)for the CK,with F_(ac) values increased from 17%-20% to 46%-55%.With RP,the F_(ac) values were enhanced by 10%-20%,and it significantly increased the copy numbers of the mcrA gene at the four rice stages(TS,booting stage(BS),grain-filling stage(GS),and RS).Furthermore,the effect of the RP on the abundance of the mcrA gene was highly concurrent with the effect on the F_(ac) values.At the TS,the Fox values at the soil-water interface were around 50%-75% for the CK,being 15%-20% lower than those of the RP in the rhizosphere.It increased to 65%-100% at the GS,but was reduced by 20%-30% after the RP.These differences might be because the copy numbers of the pmoA gene were significantly raised at the TS while lowered at the GS by the RP.This was further demonstrated by the strong correlations between the effect of the RP on the abundance of the pmoA gene and the effect on the Fox values.These findings suggest that RP markedly impacts on the abundances of the mcrA and pmoA genes,affecting the pathway of CH4_(4) production and the fraction of CH4_(4) oxidization,respectively.
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.
