Tamarix taklamakanensis,a dominant species in the Taklimakan Desert of China,plays a crucial role in stabilizing sand dunes and maintaining regional ecosystem stability.This study aimed to determine the water use stra...Tamarix taklamakanensis,a dominant species in the Taklimakan Desert of China,plays a crucial role in stabilizing sand dunes and maintaining regional ecosystem stability.This study aimed to determine the water use strategies of T.taklamakanensis in the Taklimakan Desert under a falling groundwater depth.Four typical T.taklamakanensis nabkha habitats(sandy desert of Tazhong site,saline desert-alluvial plain of Qiemo site,desert-oasis ecotone of Qira site and desert-oasis ecotone of Aral site)were selected with different climate,soil,groundwater and plant cover conditions.Stable isotope values of hydrogen and oxygen were measured for plant xylem water,soil water(soil depths within 0–500 cm),snowmelt water and groundwater in the different habitats.Four potential water sources for T.taklamakanensis,defined as shallow,middle and deep soil water,as well as groundwater,were investigated using a Bayesian isotope mixing model.It was found that groundwater in the Taklimakan Desert was not completely recharged by precipitation,but through the river runoff from snowmelt water in the nearby mountain ranges.The surface soil water content was quickly depleted by strong evaporation,groundwater depth was relatively shallow and the height of T.taklamakanensis nabkha was relatively low,thus T.taklamakanensis primarily utilized the middle(23%±1%)and deep(31%±5%)soil water and groundwater(36%±2%)within the sandy desert habitat.T.taklamakanensis mainly used the deep soil water(55%±4%)and a small amount of groundwater(25%±2%)within the saline desert-alluvial plain habitat,where the soil water content was relatively high and the groundwater depth was shallow.In contrast,within the desert-oasis ecotone in the Qira and Aral sites,T.taklamakanensis primarily utilized the deep soil water(35%±1%and 38%±2%,respectively)and may also use groundwater because the height of T.taklamakanensis nabkha was relatively high in these habitats and the soil water content was relatively low,which is associated with the reduced groundwater depth due to excessive water resource exploitation and utilization by surrounding cities.Consequently,T.taklamakanensis showed distinct water use strategies among the different habitats and primarily depended on the relatively stable water sources(deep soil water and groundwater),reflecting its adaptations to the different habitats in the arid desert environment.These findings improve our understanding on determining the water sources and water use strategies of T.taklamakanensis in the Taklimakan Desert.展开更多
Stable Pb isotopes in surface and core sediments were determined to identify the sources of Pb contaminants in the northern East China Sea(ECS).The Bayesian stable isotope mixing model was used to quantify the contrib...Stable Pb isotopes in surface and core sediments were determined to identify the sources of Pb contaminants in the northern East China Sea(ECS).The Bayesian stable isotope mixing model was used to quantify the contributions of Pb sources.The results show that since the late 1980 s,ratios of^(207)Pb/^(206)Pb and^(208)Pb/^(206)Pb increased in the top 34-cm sediment shown in the coastal core samples,reflecting elevated anthropogenic Pb input in coastal sea.Seaward increase of^(207)Pb/^(206)Pb and^(208)Pb/^(206)Pb ratios in surface sediments reveals that anthropogenic Pb came mainly via atmospheric transmission into the ECS.Anthropogenic sources accounted for 12.0%-21.1%of the total Pb in sediments after the 1990 s.Coal combustion was the largest anthropogenic contributor(47.5%±18.8%),and Pb mining and smelting,cement production,and vehicle exhaust/gasoline contributed 23.2%±7.1%,19.0%±13.0%,and 10.3%±6.9%,respectively.The proportions of the anthropogenic sources gradually increased while geogenic source(riverine sediment)decreased from the coast to the outer shelf.This study demonstrated that the significant influence of atmospheric input of Pb contaminants into the ECS,and also the urgent need to control coal combustion and Pb discharge from industrial dust and fume emission in China.It also highlights the promising application of the Simmr model to quantify the proportions of multiple sources of trace elements in an environment.展开更多
Hydrograph separation is a fundamental catchment descriptor,revealing information about sources of water in runoff generation processes. The water isotopes are ideal tracers in studying hydrological processes since th...Hydrograph separation is a fundamental catchment descriptor,revealing information about sources of water in runoff generation processes. The water isotopes are ideal tracers in studying hydrological processes since the isotope fractionation produces a natural labeling effect within the hydrologic cycle. The water isotope technique has become one of effective means for investigating complex hydrologic system on a catchment scale. This paper reviews the progress on the use of stable water isotope techniques in catchment hydrograph separation in last decades. Also,the isotope mixing model for hydrograph separation and its uncertainties are explained in detail. In future research,there are three hot issues in the use of isotopic hydrograph separation（ IHS） ： integrating new approaches into IHS,calibration and verification of IHS model and IHS application in large river basins.展开更多
In order to understand origin and fate of particulate organic matter,the isotopic composition(δ^(13)C andδ^(15)N),total or-ganic carbon content,total nitrogen content,and C/N ratios were measured for suspended parti...In order to understand origin and fate of particulate organic matter,the isotopic composition(δ^(13)C andδ^(15)N),total or-ganic carbon content,total nitrogen content,and C/N ratios were measured for suspended particulate organic matter(POM)collected from the northern South China Sea(NSCS)during summer.Our study revealed thatδ^(13)C generally decreased from land to sea,and elevatedδ^(13)C occurred at the nearshore stations,suggesting that POC was mainly contributed from the eutrophic level and microbial activity.Moreover,the distribution ofδ^(15)N values were complicated,and heterotrophic modification was responsible for higherδ^(15)N in the nearshore stations.These distribution patterns ofδ^(13)C andδ^(15)N in the nearshore stations may be associated with the intensifi-cation of human activity in the coast.Based on the Stable Isotope Analysis in R model,65%of POM was contributed by marine or-ganic matter in the NSCS,20%by terrestrial inputs,and 15%by freshwater algae.展开更多
Background Although freshwater ecosystems cover less than 1%of the earth’s surface,they support extremely high levels of biodiversity and provide vital ecosystem services.However,due to the introduction of non-native...Background Although freshwater ecosystems cover less than 1%of the earth’s surface,they support extremely high levels of biodiversity and provide vital ecosystem services.However,due to the introduction of non-native fishes,aquatic ecosystem functioning has been altered,and in some cases,declined sharply.Quantifying the impacts of invasive species has proven problematic.In this study,we examined the relative trophic position of native piscivorous fishes to estimate the effects of invasive Nile tilapia on food webs in the downstream sections of an invaded large subtropical river,the Pearl River,China.Furthermore,we quantified how native piscivorous fish diets changed as the Nile tilapia invasion progressed.Results The trophic position of the widely distributed and locally important economically harvested piscivorous culter fish(Culter recurviceps),mandarinfish(Siniperca kneri),and catfish(Pelteobagrus fulvidraco)lowered significantly in the invaded Dongjiang River compared to an uninvaded reference Beijiang River.The lower trophic position of these piscivorous fishes was reflected by a major reduction in the proportion of prey fish biomass in their diets following the Nile tilapia invasion.Small fishes in the diet of culter fish from the reference river(33%small fishes,17%zooplankton)shifted to lower trophic level zooplankton prey in the invaded river(36%zooplankton,25%small fish),possibly due to the presence of Nile tilapia.Additionally,small fishes in the diet of mandarinfish in the reference river(46%small fishes,11%aquatic insects)declined in the invaded river(20%aquatic insects,30%small fishes).Similarly,the diet of catfish from the reference river shifted from fish eggs(25%fish eggs,25%aquatic insects)to aquatic insects in the invaded river(44%aquatic insects,5%fish eggs).Conclusions The results of this study contributed to a growing body of evidence,suggesting that Nile tilapia can modify trophic interactions in invaded ecosystems.It is crucial to understand the processes outlined in this study in order to better assess non-native aquatic species,conserve the stability of freshwater ecosystems,and improve current conservation strategies in reaches of the Pearl River and other similar rivers that have experienced invasions of non-native species.展开更多
Background:Conifers partition different N forms from soil,including ammonium,nitrate,and dissolved organic N(DON),to sustain plant growth.Previous studies focused on inorganic N sources and specific amino acid forms u...Background:Conifers partition different N forms from soil,including ammonium,nitrate,and dissolved organic N(DON),to sustain plant growth.Previous studies focused on inorganic N sources and specific amino acid forms using ^(15)N labelling,but knowledge of the contribution of DON to mature conifers’N uptake is still scarce.Here,we quantified the contribution of different N forms(DON vs.NH_(4)^(+)vs.NO_(3)^(−))to total N uptake,based on ^(15)N natural abundance of plant and soil available N,in four mature conifers(Pinus koraiensis,Pinus sylvestris,Picea koraiensis,and Larix olgensis).Results:DON contributed 31%,29%,28%,and 24%to total N uptake by Larix olgensis,Picea koraiensis,Pinus koraiensis,and Pinus sylvestris,respectively,whereas nitrate contributed 42 to 52%and ammonium contributed 19 to 29%of total N uptake for these four coniferous species.Conclusions:Our results suggested that all four conifers could take up a relatively large proportion of nitrate,while DON was also an important N source for the four conifers.Given that DON was the dominant N form in study soil,such uptake pattern of conifers could be an adaptive strategy for plants to compete for the limited available N sources from soil so as to promote conifer growth and maintain species coexistence.展开更多
基金supported by the "Research and Development of Sand Prevention Technology of Highway and Soil Erosion Control Technology of Pipelines" of the Strategic Priority Research Program of the Chinese Academy of Sciences "Environmental Changes and Silk Road Civilization in Pan-Third Pole Region"(XDA2003020201)the Key Inter-governmental Projects for International Scientific and Technological Innovation Cooperation of the National Key Research and Development Program of China:"China-Mongolia Cooperation Research and Demonstration in Grassland Desertification Control Technology"(2017YFE0109200)+2 种基金the National Natural Science Foundation of China(41571011,31971731,U1703102)the Key Technical Personnel(Y932111)the Thousand Youth Talents Plan Project(Y472241001)
文摘Tamarix taklamakanensis,a dominant species in the Taklimakan Desert of China,plays a crucial role in stabilizing sand dunes and maintaining regional ecosystem stability.This study aimed to determine the water use strategies of T.taklamakanensis in the Taklimakan Desert under a falling groundwater depth.Four typical T.taklamakanensis nabkha habitats(sandy desert of Tazhong site,saline desert-alluvial plain of Qiemo site,desert-oasis ecotone of Qira site and desert-oasis ecotone of Aral site)were selected with different climate,soil,groundwater and plant cover conditions.Stable isotope values of hydrogen and oxygen were measured for plant xylem water,soil water(soil depths within 0–500 cm),snowmelt water and groundwater in the different habitats.Four potential water sources for T.taklamakanensis,defined as shallow,middle and deep soil water,as well as groundwater,were investigated using a Bayesian isotope mixing model.It was found that groundwater in the Taklimakan Desert was not completely recharged by precipitation,but through the river runoff from snowmelt water in the nearby mountain ranges.The surface soil water content was quickly depleted by strong evaporation,groundwater depth was relatively shallow and the height of T.taklamakanensis nabkha was relatively low,thus T.taklamakanensis primarily utilized the middle(23%±1%)and deep(31%±5%)soil water and groundwater(36%±2%)within the sandy desert habitat.T.taklamakanensis mainly used the deep soil water(55%±4%)and a small amount of groundwater(25%±2%)within the saline desert-alluvial plain habitat,where the soil water content was relatively high and the groundwater depth was shallow.In contrast,within the desert-oasis ecotone in the Qira and Aral sites,T.taklamakanensis primarily utilized the deep soil water(35%±1%and 38%±2%,respectively)and may also use groundwater because the height of T.taklamakanensis nabkha was relatively high in these habitats and the soil water content was relatively low,which is associated with the reduced groundwater depth due to excessive water resource exploitation and utilization by surrounding cities.Consequently,T.taklamakanensis showed distinct water use strategies among the different habitats and primarily depended on the relatively stable water sources(deep soil water and groundwater),reflecting its adaptations to the different habitats in the arid desert environment.These findings improve our understanding on determining the water sources and water use strategies of T.taklamakanensis in the Taklimakan Desert.
基金the Open Fund of CAS Key Laboratory of Marine Ecology and Environmental Sciences,Institute of Oceanology,Chinese Academy of Sciences(No.KLMEES201805)the National Natural Science Foundation of China(No.41406087)the"First Class Fishery Discipline"Program in Shandong Province,China。
文摘Stable Pb isotopes in surface and core sediments were determined to identify the sources of Pb contaminants in the northern East China Sea(ECS).The Bayesian stable isotope mixing model was used to quantify the contributions of Pb sources.The results show that since the late 1980 s,ratios of^(207)Pb/^(206)Pb and^(208)Pb/^(206)Pb increased in the top 34-cm sediment shown in the coastal core samples,reflecting elevated anthropogenic Pb input in coastal sea.Seaward increase of^(207)Pb/^(206)Pb and^(208)Pb/^(206)Pb ratios in surface sediments reveals that anthropogenic Pb came mainly via atmospheric transmission into the ECS.Anthropogenic sources accounted for 12.0%-21.1%of the total Pb in sediments after the 1990 s.Coal combustion was the largest anthropogenic contributor(47.5%±18.8%),and Pb mining and smelting,cement production,and vehicle exhaust/gasoline contributed 23.2%±7.1%,19.0%±13.0%,and 10.3%±6.9%,respectively.The proportions of the anthropogenic sources gradually increased while geogenic source(riverine sediment)decreased from the coast to the outer shelf.This study demonstrated that the significant influence of atmospheric input of Pb contaminants into the ECS,and also the urgent need to control coal combustion and Pb discharge from industrial dust and fume emission in China.It also highlights the promising application of the Simmr model to quantify the proportions of multiple sources of trace elements in an environment.
基金Supported by the National Natural Science Foundation of China(41101066)the China Postdoctoral Science Foundation Funded Project(2013M532094)
文摘Hydrograph separation is a fundamental catchment descriptor,revealing information about sources of water in runoff generation processes. The water isotopes are ideal tracers in studying hydrological processes since the isotope fractionation produces a natural labeling effect within the hydrologic cycle. The water isotope technique has become one of effective means for investigating complex hydrologic system on a catchment scale. This paper reviews the progress on the use of stable water isotope techniques in catchment hydrograph separation in last decades. Also,the isotope mixing model for hydrograph separation and its uncertainties are explained in detail. In future research,there are three hot issues in the use of isotopic hydrograph separation（ IHS） ： integrating new approaches into IHS,calibration and verification of IHS model and IHS application in large river basins.
基金This work was supported by the National Natural Science Foundation of China(Nos.U1901213,41466010,41676008)the China National Key Research and Development Plan Project(No.2016YFC1401403)+3 种基金the Guangdong Natural Science Foundation of China(Nos.2016 A0303120042020A1515010500)the Project of Enhancing School with Innovation of Guangdong Ocean University(Nos.GDOU2016050260,230419097)the Marine Science Research Team Project of Guangdong Ocean University(No.002026002004).
文摘In order to understand origin and fate of particulate organic matter,the isotopic composition(δ^(13)C andδ^(15)N),total or-ganic carbon content,total nitrogen content,and C/N ratios were measured for suspended particulate organic matter(POM)collected from the northern South China Sea(NSCS)during summer.Our study revealed thatδ^(13)C generally decreased from land to sea,and elevatedδ^(13)C occurred at the nearshore stations,suggesting that POC was mainly contributed from the eutrophic level and microbial activity.Moreover,the distribution ofδ^(15)N values were complicated,and heterotrophic modification was responsible for higherδ^(15)N in the nearshore stations.These distribution patterns ofδ^(13)C andδ^(15)N in the nearshore stations may be associated with the intensifi-cation of human activity in the coast.Based on the Stable Isotope Analysis in R model,65%of POM was contributed by marine or-ganic matter in the NSCS,20%by terrestrial inputs,and 15%by freshwater algae.
基金supported by the National Natural Science Foundation of China(General Program No.31870527)China-ASEAN Maritime Cooperation Fund(CAMC-2018F)Science and Technology Program of Guangzhou,China(202201010761).
文摘Background Although freshwater ecosystems cover less than 1%of the earth’s surface,they support extremely high levels of biodiversity and provide vital ecosystem services.However,due to the introduction of non-native fishes,aquatic ecosystem functioning has been altered,and in some cases,declined sharply.Quantifying the impacts of invasive species has proven problematic.In this study,we examined the relative trophic position of native piscivorous fishes to estimate the effects of invasive Nile tilapia on food webs in the downstream sections of an invaded large subtropical river,the Pearl River,China.Furthermore,we quantified how native piscivorous fish diets changed as the Nile tilapia invasion progressed.Results The trophic position of the widely distributed and locally important economically harvested piscivorous culter fish(Culter recurviceps),mandarinfish(Siniperca kneri),and catfish(Pelteobagrus fulvidraco)lowered significantly in the invaded Dongjiang River compared to an uninvaded reference Beijiang River.The lower trophic position of these piscivorous fishes was reflected by a major reduction in the proportion of prey fish biomass in their diets following the Nile tilapia invasion.Small fishes in the diet of culter fish from the reference river(33%small fishes,17%zooplankton)shifted to lower trophic level zooplankton prey in the invaded river(36%zooplankton,25%small fish),possibly due to the presence of Nile tilapia.Additionally,small fishes in the diet of mandarinfish in the reference river(46%small fishes,11%aquatic insects)declined in the invaded river(20%aquatic insects,30%small fishes).Similarly,the diet of catfish from the reference river shifted from fish eggs(25%fish eggs,25%aquatic insects)to aquatic insects in the invaded river(44%aquatic insects,5%fish eggs).Conclusions The results of this study contributed to a growing body of evidence,suggesting that Nile tilapia can modify trophic interactions in invaded ecosystems.It is crucial to understand the processes outlined in this study in order to better assess non-native aquatic species,conserve the stability of freshwater ecosystems,and improve current conservation strategies in reaches of the Pearl River and other similar rivers that have experienced invasions of non-native species.
基金funded by the National Key Research and Development Program of China(2016YFA0600802)Key Research Program of Frontier Sciences of Chinese Academy of Sciences(QYZDB-SSW-DQC002)+4 种基金K.C.Wong Education Foundation(GJTD-2018-07)Liaoning Vitalization Talents Program(XLYC1902016)the National Natural Science Foundation of China(41773094,41811530305,31901134,41571455,and 31770498)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23070103)Scientific Research Foundation of the Educational Department of Liaoning Province(L201908).
文摘Background:Conifers partition different N forms from soil,including ammonium,nitrate,and dissolved organic N(DON),to sustain plant growth.Previous studies focused on inorganic N sources and specific amino acid forms using ^(15)N labelling,but knowledge of the contribution of DON to mature conifers’N uptake is still scarce.Here,we quantified the contribution of different N forms(DON vs.NH_(4)^(+)vs.NO_(3)^(−))to total N uptake,based on ^(15)N natural abundance of plant and soil available N,in four mature conifers(Pinus koraiensis,Pinus sylvestris,Picea koraiensis,and Larix olgensis).Results:DON contributed 31%,29%,28%,and 24%to total N uptake by Larix olgensis,Picea koraiensis,Pinus koraiensis,and Pinus sylvestris,respectively,whereas nitrate contributed 42 to 52%and ammonium contributed 19 to 29%of total N uptake for these four coniferous species.Conclusions:Our results suggested that all four conifers could take up a relatively large proportion of nitrate,while DON was also an important N source for the four conifers.Given that DON was the dominant N form in study soil,such uptake pattern of conifers could be an adaptive strategy for plants to compete for the limited available N sources from soil so as to promote conifer growth and maintain species coexistence.
