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
Identifying plant water sources is fundamental for elucidating ecohydrological processes and improving water resource management in arid zones under climate change.Stable hydrogen and oxygen isotopes are commonly used...Identifying plant water sources is fundamental for elucidating ecohydrological processes and improving water resource management in arid zones under climate change.Stable hydrogen and oxygen isotopes are commonly used to trace plant water uptake;however,cryogenic vacuum extraction(CVE),the standard method for extracting plant xylem water,may induce deuterium depletion,thereby biasing source attribution.To systematically assess the effects of CVE-induced deuterium depletion across species,size classes,and habitats,we excavated five representative soil profiles along the mainstream of the Tarim River in northwestern China,in mid-July 2022.A total of 29 individuals,comprising both Populus euphratica and Tamarix ramosissima,were sampled.We divided P.euphratica individuals into four groups based on diameter at breast height(<50,50-100,100-250,and>250 cm),while categorized T.ramosissima individuals into four groups according to plant height(<1.0,1.0-2.0,2.0-4.0,and>4.0 m).Plant xylem water was extracted using CVE,and five deuterium depletion scenarios(-5.00‰,-7.00‰,-9.00‰,-11.00‰,and-13.00‰)were simulated.The Bayesian Mixing Model for Stable Isotope Analysis in R(MixSIAR)was applied under six input modes to quantify the proportional contributions of potential water sources and associated prediction errors.Model evaluation revealed that P.euphratica achieved the highest accuracy with a-9.00‰correction of depletion,whereas a-11.00‰ correction was optimal for T.ramosissima,reducing relative prediction errors by 68.65%and 67.73%,respectively,compared with uncorrected scenario.Small-sized P.euphratica individuals exhibited less deuterium depletion,whereas no clear size-dependent pattern was observed for T.ramosissima.Spatially,plant individuals located farther from the river exhibited reduced deuterium depletion in xylem water.Despite differences in species traits and habitat conditions,both species predominantly relied on deep soil water and groundwater,which together contributed,on average,61.45%and 59.95%for P.euphratica and T.ramosissima,respectively.These findings highlight the necessity of accounting for CVE-induced deuterium depletion when identifying plant water-use strategies and provide methodological guidance for isotope-based ecohydrological studies in arid environments.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
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supported by the National Key R&D Program of China(2023YFC3206801)the National Natural Science Foundation of China(42171041).
文摘Identifying plant water sources is fundamental for elucidating ecohydrological processes and improving water resource management in arid zones under climate change.Stable hydrogen and oxygen isotopes are commonly used to trace plant water uptake;however,cryogenic vacuum extraction(CVE),the standard method for extracting plant xylem water,may induce deuterium depletion,thereby biasing source attribution.To systematically assess the effects of CVE-induced deuterium depletion across species,size classes,and habitats,we excavated five representative soil profiles along the mainstream of the Tarim River in northwestern China,in mid-July 2022.A total of 29 individuals,comprising both Populus euphratica and Tamarix ramosissima,were sampled.We divided P.euphratica individuals into four groups based on diameter at breast height(<50,50-100,100-250,and>250 cm),while categorized T.ramosissima individuals into four groups according to plant height(<1.0,1.0-2.0,2.0-4.0,and>4.0 m).Plant xylem water was extracted using CVE,and five deuterium depletion scenarios(-5.00‰,-7.00‰,-9.00‰,-11.00‰,and-13.00‰)were simulated.The Bayesian Mixing Model for Stable Isotope Analysis in R(MixSIAR)was applied under six input modes to quantify the proportional contributions of potential water sources and associated prediction errors.Model evaluation revealed that P.euphratica achieved the highest accuracy with a-9.00‰correction of depletion,whereas a-11.00‰ correction was optimal for T.ramosissima,reducing relative prediction errors by 68.65%and 67.73%,respectively,compared with uncorrected scenario.Small-sized P.euphratica individuals exhibited less deuterium depletion,whereas no clear size-dependent pattern was observed for T.ramosissima.Spatially,plant individuals located farther from the river exhibited reduced deuterium depletion in xylem water.Despite differences in species traits and habitat conditions,both species predominantly relied on deep soil water and groundwater,which together contributed,on average,61.45%and 59.95%for P.euphratica and T.ramosissima,respectively.These findings highlight the necessity of accounting for CVE-induced deuterium depletion when identifying plant water-use strategies and provide methodological guidance for isotope-based ecohydrological studies in arid environments.
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.
