Estimating the design flood under nonstationary conditions is challenging. In this study, a sample reconstruction approach was developed to transform a nonstationary series into a stationary one in a future time windo...Estimating the design flood under nonstationary conditions is challenging. In this study, a sample reconstruction approach was developed to transform a nonstationary series into a stationary one in a future time window (FTW). In this approach, the first-order moment (EFTW) of an extreme flood series in the FTW was used, and two possible methods of estimating EFTW values in terms of point values and confidence intervals were developed. Three schemes were proposed to analyze the uncertainty of design flood estimation in terms of sample representativeness, uncertainty from EFTW estimation, and both factors, respectively. To investigate the performance of the sample reconstruction approach, synthesis experiments were designed based on the annual peak series of the Little Sugar Creek in the United States. The results showed that the sample reconstruction approach performed well when the high-order moment of the series did not change significantly in the specified FTW. Otherwise, its performance deteriorated. In addition, the uncertainty of design flood estimation caused by sample representativeness was greater than that caused by EFTW estimation.展开更多
The Zoige Basin,located in the eastern region of the Tibetan Plateau of China,is characterized by its climate sensitivity and complex surface environment.It is vital to understand the response of the surface processes...The Zoige Basin,located in the eastern region of the Tibetan Plateau of China,is characterized by its climate sensitivity and complex surface environment.It is vital to understand the response of the surface processes to environmental changes in the Zoige Basin since the last deglaciation,as well as the response of environmental changes and surface processes on the Tibetan Plateau relate to global changes.In August 2020,a field investigation was conducted in the Zoige Basin.A complete set of stratigraphic profile from the high platform at the front of the glacial-diluvial fan in the Maqu reach of the western basin was selected as the research subject.Optically stimulated luminescence(OSL)dating samples and sedimentary samples were collected from key layers and brought back to the laboratory for experimental analysis,and the surface processes and environment changes since the last deglaciation in the Zoige Basin were investigated through particle size analysis and OSL dating.The results showed that during the last glacial period before 14.5 kyr,a substantial glacial-alluvial fan composed of sand and gravel layers was formed by flash flood processes triggered by glacial meltwater and heavy precipitation.In the Bølling-Allerød warm period of 14.5–11.7 kyr,a warm and humid climate prevailed,with the formation of silty bog environments in the shallow depressions at the glacial-alluvial fan's forefront and the development of gray-green bog soil deposits.However,during the Younger Dryas period,an abrupt climate deterioration occurred,with the upper section of the gray-green bog soil layer in the shallow depression to experience folding and deformation due to surface freeze-thaw actions.During the early Holocene period from 11.7 kyr to 8.5 kyr,the climate was relatively dry,resulting in prevalent aeolian sand activitities.Coarse silt accumulated in the shallow depression,and sedimentary facies alternating between aeolian sand and bog soil deposits developed owing to strong wind patterns on the plateau surface.In the warm and humid period from 8.5 kyr to 3.1 kyr,increased weathering and pedogenesis enhanced clay content in sediments,which developed into the paleosol.In the late Holocene,starting from 3.1 kyr,the climate became relatively dry once more,with aeolian sand activity prevalent.The coarse silt that accumulated during the late Holocene transformed into subalpine meadow black soil because of rising temperature and humidity levels.These findings indicated that the developmental process of the high platform in the Maqu reach of the Zoige Basin,which was significant for understanding the environmental changes and surface processes in the source region of the Yellow River since the last deglaciation.展开更多
Environmental conditions change constantly either by anthropogenic perturbation or naturally across space and time.Often,a change in behavior is the frst response to changing conditions.Behavioral fexibility can poten...Environmental conditions change constantly either by anthropogenic perturbation or naturally across space and time.Often,a change in behavior is the frst response to changing conditions.Behavioral fexibility can potentially improve an organism’s chances to survive and reproduce.Currently,we lack an understanding on the time-scale such behavioral adjustments need,how they actually affect reproduction and survival and whether behavioral adjustments are suffcient in keeping up with changing conditions.We used house mice(Mus musculus)to test whether personality and life-history traits can adjust to an experimentally induced food-switch fexibly in adulthood or by intergenerational plasticity,that is,adjustments only becoming visible in the offspring generation.Mice lived in 6 experimental populations of semi-natural environments either on high or standard quality food for 4 generations.We showed previously that high-quality food induced better conditions and a less risk-prone personality.Here,we tested whether the speed and/or magnitude of adjustment shows condition-dependency and whether adjustments incur ftness effects.Life-history but not personality traits reacted fexibly to a food-switch,primarily by a direct reduction of reproduction and sloweddown growth.Offspring whose parents received a food-switch developed a more active stress-coping personality and gained weight at a slower rate compared with their respective controls.Furthermore,the modulation of most traits was condition-dependent,with animals previously fed with high-quality food showing stronger responses.Our study highlights that life-history and personality traits adjust at different speed toward environmental change,thus,highlighting the importance of the environment and the mode of response for evolutionary models.展开更多
Understanding the dynamics of phytoplankton communities in coastal zones is crucial for the management and conservation of coastal ecosystems.Previous research indicated that the phytoplankton community structure and ...Understanding the dynamics of phytoplankton communities in coastal zones is crucial for the management and conservation of coastal ecosystems.Previous research indicated that the phytoplankton community structure and dominant taxa in the Bohai Sea(BHS)have exhibited significant shifts from the 1990s to the early 2010s in response to environmental changes,especially the change in nutrient structure.This study comprehensively investigated the variations in net-collected phytoplankton(>76μm)community structure,diversity,and environmental factors in the BHS during the late summers of 2011-2020,aiming to understand the recent trend in phytoplankton community structure and to explore the interactions between the communities and the environment.During the study period,the nutrient status in the BHS was characterized by a decrease in dissolved inorganic nitrogen(DIN)concentration,an increase in dissolved inorganic phosphorus(DIP)concentration,and a return of the nitrogen-to-phosphorus(N/P)molar ratio(hereinafter referred to as N/P ratio)to the Redfield ratio since 2016.The eutrophication index(EI)in the BHS remained stable and was generally at a low level(<1).The Dia/Dino index fluctuated but did not show an obvious trend.Overall,the eutrophication,the imbalance in nutrient ratio,and the shift in phytoplankton community structure did not continue during the study period.The increased abundance of phytoplankton was strongly associated with elevated concentrations of DIN,as well as higher N/P and nitrogen-to-silicon(N/Si)ratios,whereas the greater diversity was strongly linked to higher concentrations of DIP.Diatoms and dinoflagellates showed significant differences in their interactions with the environment,and their relative dominance was related to water column depth and stratification intensity;their impacts on the phytoplankton community diversity were also significantly different.The variations of certain dominant species,i.e.,Skeletonema costatum,Paralia sulcata,and Tripos longipes,exhibited strong links to the changes in nutrient structure in the BHS.The findings of this study contribute to understanding the regional environmental changes and provide insights into the adaptive strategies of coastal ecosystems in response to environmental shifts and fluctuations.展开更多
The accumulation processes of loess in northeastern(NE)China record the varying characteristics of the East Asian Monsoons(EAM)and the evolution of the local environment.In this study,grain size end-member analysis of...The accumulation processes of loess in northeastern(NE)China record the varying characteristics of the East Asian Monsoons(EAM)and the evolution of the local environment.In this study,grain size end-member analysis of the Dajiugang(DJG)section deposited since the Last Glacial in Chifeng City,NE China was used to reveal the dynamic depositional characteristics of loess and environmental evolution of NE China.Results showed that the Chifeng loess comprises three grain size end-members(EM),EM1(7.38μm),EM2(49.4μm)and EM3(90.00μm),indicating the three transport dynamics of dust delivered to the region.The EM1 represents atmospheric dust as the background.The EM2,mainly derived from relatively distant-sources deposition,and EM3,material transported over a short distance,correspond to the intensity of southwesterly winds and the East Asian Winter Monsoon(EAWM),respectively.Results of climate reconstruction,combined with other records,showed that the climate was generally cold and dry with a strong EAWM and a weak East Asian summer monsoon(EASM)during the stadial-period[Marine Isotope Stage(MIS)4 and MIS 2 stage].The climate was predominantly warm and humid,with weak EAWM and surface winds and strong EASM in interstadial-period(MIS 3 and MIS 1 stage).Comparisons between indicators,e.g.,EM3,the LR04 benthicδ18O stack and summer insolation at 65°N suggest that the strong EAWM is induced by increasing the Northern Hemisphere ice volume and reduced summer solar radiation.展开更多
Particle size, the contents of carbonate and TOC were analyzed on lake sediments from a short core in Hongjiannao Lake to discuss the environmental changes during the past decades. On the basis of the records in lake ...Particle size, the contents of carbonate and TOC were analyzed on lake sediments from a short core in Hongjiannao Lake to discuss the environmental changes during the past decades. On the basis of the records in lake sediments and comparison with the meteorological data of Yulin region, the environmental changes in Hongjiannao Lake were approximately divided into two stages. In stage A （1957 -1996）, the lake evolution and the environmental change were mainly influenced by natural factors. It contains three sub-stages： A1 （1957-1969）, a period of lake expansion, A2 （1969-1990）, a stable period with high lake levels, and A3 （1990 -1996）, a period of gradual extraction of the lake. In stage B （1996 -2005）, the lake area still keeps diminishing. During this period, organic matter increased rapidly due to the input of nutrient elements in the catchment. The carbonate content, however, decreased. As the precipitation was decreasing and the temperature was increasing, the decrease of carbonate content could not be explained by either temperature or precipitation change.展开更多
Wetlands play a critical role in the global environment.The Middle Yangtze River Basin(MYRB),known for its abundant wetland resources,has experienced notable changes resulting from the complex interplay of environment...Wetlands play a critical role in the global environment.The Middle Yangtze River Basin(MYRB),known for its abundant wetland resources,has experienced notable changes resulting from the complex interplay of environmental factors.Therefore,we investigated the spatiotemporal characteristics of wetland ecological quality in the MYRB from 2001 to 2020.Utilizing the random forest(RF)regression algorithm and patch-generated land-use simulation(PLUS)model,we forecasted variations in wetland habitat quality and their determinants under the Shared Socioeconomic Pathway-Representative Concentration Pathway(SSPRCP)framework from 2035 to 2095.The main findings are as follows:(1)The RF algorithm was optimal for land-use and land-cover(LULC)classification in the MYRB from 2001 to 2020,when notable changes were observed in water bodies and buildings.However,the forested area exhibited an increase and decrease of 3.9%and 1.2%under the SSP1-2.6 and SSP5-8.5 scenarios,respectively,whereas farmland exhibited a diminishing trend.(2)Wetlands were primarily concentrated in the central and eastern MYRB,with counties in the southwest exhibiting superior ecological-environmental quality from 2001 to 2020.Notably,wetland coverage revealed significantly high level,significant changes,frequent but relatively minor changes under the SSP1-2.6,SSP2-4.5,and SSP 5-8.5 scenarios,respectively.(3)Regions with lower habitat quality were primarily concentrated in urbanized areas characterized by frequent human activities,indicating a clear degradation in habitat quality across different scenarios.In conclusion,we established a foundational framework for future investigations into the eco-hydrological processes and ecosystem quality of watersheds.展开更多
Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the wo...Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the world.JMS mainly publishes academic and technical papers concerning environmental changes and sustainable development in mountain areas under natural conditions or/and with the influence of human activities.It also accepts book reviews,commentary,and reports on mountain research and introductions to mountain research organizations.展开更多
Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the wo...Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the world.JMS mainly publishes academic and technical papers concerning environmental changes and sustainable development in mountain areas under natural conditions or/and with the influence of human activities.It also accepts book reviews,commentary,and reports on mountain research and introductions to mountain research organizations.展开更多
Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the wo...Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the world.JMS mainly publishes academic and technical papers concerning environmental changes and sustainable development in mountain areas under natural conditions or/and with the influence of human activities.It also accepts book reviews,commentary,and reports on mountain research and introductions to mountain research organizations.展开更多
Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the wo...Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the world.JMS mainly publishes academic and technical papers concerning environmental changes and sustainable development in mountain areas under natural conditions or/and with the influence of human activities.It also accepts book reviews,commentary,and reports on mountain research and introductions to mountain research organizations.展开更多
Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the wo...Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the world.JMS mainly publishes academic and technical papers concerning environmental changes and sustainable development in mountain areas under natural conditions or/and with the influence of human activities.It also accepts book reviews,commentary,and reports on mountain research and introductions to mountain research organizations.展开更多
Lacustrine sedimentary nitrogen isotope(δ^(15)N)records offer crucial insights into the impacts of regional anthropogenic activities and environmental changes on nitrogen cycling dynamics within the context of global...Lacustrine sedimentary nitrogen isotope(δ^(15)N)records offer crucial insights into the impacts of regional anthropogenic activities and environmental changes on nitrogen cycling dynamics within the context of global climate change.This study summarized δ^(15)N data from 27 Chinese lakes since 1750 CE,categorizing them into Types Ⅰ(eastern and southern China,densely populated area)and Ⅱ(Northwestern China[NWC]and the Qinghai-Tibet Plateau[QTP],sparsely populated area).The results showed pronounced regional and temporal variability in nitrogen isotope trends.Type Ⅰ lakes exhibited a significant positive δ^(15)N deviation post-1950 CE,linked to population growth(r=0.91,p<0.01)and economic development,with mitigation after 2000 CE likely due to enhanced environmental policies.Conversely,Type Ⅱ lakes showed coherent δ^(15)N variations with natural climate change from 1750 to 1950 CE,followed by a post-1950 CE decline exceeding natural variability.This shift is attributed to a“warming-wetting trend”in NWC and the QTP,which presumably increased terrestrial productivity,altered nitrogen cycling,and enhanced ^(15)N-depleted nitrogen input via surface runoff.Rising temperatures may have enhanced the activity and abundance of nitrogen-fixing microorganisms,jointly driving a negative δ^(15)N shift.This study highlights climate conditions and anthropogenic activities as key drivers of nitrogen cycle perturbations in China,with their influences varying spatiotemporally,thereby providing crucial insights into the nitrogen cycling dynamics in Chinese lakes.展开更多
Environments in arid and semiarid regions are extremely sensitive to climate changes. High wind activity in these regions has resulted in an extensively developed arid geomorphology, but past environmental changes are...Environments in arid and semiarid regions are extremely sensitive to climate changes. High wind activity in these regions has resulted in an extensively developed arid geomorphology, but past environmental changes are poorly understood because of the absence of relatively high-resolution proxies. The accumulation characteristics of nebkhas, which have developed extensively in these regions, can be used as a method of reconstructing environmental changes. Here we summarized recent advances in research on the formation, development, and sediment characteristics of nebkhas and their significance to environmental changes in arid and semiarid regions. Based on the studies of our colleagues, we suggested that research on nebkha formation can provide distinct clues about environmental changes in arid and semiarid regions; however, continued studies are needed.展开更多
Based on data from a field survey in 2001 along the Northeast China transect (NECT), a precipitation gradient,and a short-term simulation experiment under ambient CO2 of 350 μmol mol-1 and doubled CO2 of 700 μmol mo...Based on data from a field survey in 2001 along the Northeast China transect (NECT), a precipitation gradient,and a short-term simulation experiment under ambient CO2 of 350 μmol mol-1 and doubled CO2 of 700 μmol mol-1with different soil moisture contents of 30%-45%, 45%-60%, and 60%-80% soil water holding capacity, the distributionof soil organic carbon and labile carbon along the NECT, their relationships with precipitation and their responses toCO2 enrichment and soil moisture changes were analyzed. The results indicated that the soil labile carbon along thegradient was significantly related to soil organic carbon (r = 0.993, P < 0.001). The soil labile carbon decreased morerapidly with depth than organic carbon. The soil organic and labile carbon along the gradient decreased with decrease inlongitude in both the topsoils and subsoils, and the coefficient of variation for the labile carbon was greater than that forthe organic carbon. Both the soil organic carbon and labile carbon had significant linear relationships with precipitation,with the correlation coefficient of soil organic carbon being lower (0.677 at P < 0.001) than that of soil labile carbon(0.712 at P < 0.001). In the simulation experiment with doubled and ambient CO2 and different moisture contents, thecoefficient of variation for soil organic carbon was only 1.3%, while for soil labile carbon it was 29.7%. With doubled CO2concentration (700 μmol mol-1), soil labile carbon decreased significantly at 45% to 60% of soil moisture content. Theseindicated that soil labile carbon was relatively more sensitive to environmental changes than soil organic carbon.展开更多
Over the past two decades in China, stress on the environment has increased continuously. This paper will assess the change in environmental quality over time, and its spatial variation using data from the statistical...Over the past two decades in China, stress on the environment has increased continuously. This paper will assess the change in environmental quality over time, and its spatial variation using data from the statistical yearbooks of 31 provincial administrative regions in 1990, 1995, 2000, 2005, and 2010. These books provide a general assessment of the environment at the provincial level, and the three major economic regions from western to eastern China. By using the geographic information system （GIS） and SPSS, we analyzed the changing trend of China＇s eco-environment and calculated the changing trajectory in the gravity center of the eco-environmental quality. We conclude the following. （1） From 1990 to 2010, the rate of deterioration of the environment went down. We argue that the cause of this trend was neither the result as ＂the deterioration trend was under control＂ noticed by the government departments concerned, nor ＂the deterioration rate of the environment was increasingly intensified＂ suggested by many researchers. （2） Since 1990, the general environment has been worsening in China, but it was improved in some regions; however, the ecological deficit is still expanding and will last for a long time. （3） From western to eastern China, the deterioration rate of environmental quality was slowed down. The reasons include a good natural environment, a developed regional economy, and technology and finance in eastern China. （4） After extensive economic development in China, there are imbalances of population, economy, society, and the environment in the 31 provincial regions. The governments at all levels should play an important role in research and protecting the environment. In addition, it is imperative to implement positive measures such as controlling population, improving the environment, and promoting smart development to balance the socio-ecological system.展开更多
The Xiaohe Cemetery archaeological site （Cal. 4-3.5 ka BP） is one of the most important Bronze Age sites in Xinjiang, China. Although the surrounding environment is an extremely arid desert now, abundant archaeologi...The Xiaohe Cemetery archaeological site （Cal. 4-3.5 ka BP） is one of the most important Bronze Age sites in Xinjiang, China. Although the surrounding environment is an extremely arid desert now, abundant archaeological remains indicate that human occupation was common during certain periods in the Holocene. Field investigations and laboratory analyses of a sediment profile near the Xiaohe Cemetery indicate that while the regional environment was arid desert throughout the Holocene there were three episodes of lake forma- tion near the site in the periods 4.8-3.5 ka BP, 2.6-2.1 ka BP and 1.2-0.9 ka BP. Geomorphic and hydrological investigations reveal that a lake or lakes formed in a low-lying area when water was derived initially from the Kongque River and then shunted into the Xiaohe River basin. Low amounts of active chemical elements in lacustrine sediment between 4.8-3.5 ka BP indicate abundant and continuous water volume in the lake; the content of active chemical elements increased between 2.6-2.1 ka BP but was still at a relatively low level, suggesting a declining amount of water and diminished inflow. Between 1.2-0.9 ka BP there was a very high content of active elements, suggesting decreased water volume and indicating that the lake was stagnate. In contrast, the general climate condition shows that there had a warm-humid stage at 8-6 ka BP, a cool-humid stage at 6-2.9 ka BP and a warm-dry stage at 2.9-0.9 ka BP in this region. The hydrological evolutions around Xiaohe Cemetery did not have one-to-one correspondence with climate changes. Regional comparison indicates that broad-scale climatic conditions played an important role through its influences on the water volume of the Tarim River and Kongque River. But, the formation of the lakes and their level were controlled by geomorphic conditions that influenced how much water volume could be shunted to Xiaohe River from Kongque River. Human occupation of the Xiaohe Cemetery and nearby regions during the Bronze Age and Han-Jin period （202 BC-420 AD） corresponded to the two earlier lake periods, while no human activities existed in the third lake period because of the decreased water volume.展开更多
Controlled by climate changes, there were three large-scale transgressions and regressions around the Bohai Sea during the late Quaternary, which were accepted by most geologists. However, a big controversy still exis...Controlled by climate changes, there were three large-scale transgressions and regressions around the Bohai Sea during the late Quaternary, which were accepted by most geologists. However, a big controversy still exists about the time when the transgressions occurred separately. In order to find out the process of the paleoenvironmental changes around the Bohai Sea in the late Quaternary, the foraminifera assemblages from a new borehole Lz908 in the southern coast of the Laizhou Bay were studied, and then the transgressive strata were indentified. Combined with accelerator mass spectrometry radiocarbon 14C（AMS14C） and optically stimulated luminescence（OSL） ages, the occurrence time of these transgressions were re-determined. The result showed that three major large-scale transgressions occurred separately at the beginning of marine isotopic stage 7（MIS7）, the last interglacial period（MIS5） and the Holocene. In addition, a small-scale transgression occurred in the mid-MIS6, and the corresponding transgressive stratum was deposited. The transgressive deposition of MIS3 was also discovered in this study. However, the characteristics of the foraminifera indicated the environment during this period was colder than that in the MIS5. By comparison with the global sea-level changes, the paleoenvironmental changes around the Bohai Sea in the late Quaternary can be consistent with the global climate changes.展开更多
The Jiaozhou Bay is characterized by heavy eutrophication that is associated with intensive anthropogenic activities. Four core sediments from the Jiaozhou Bay are analyzed using bulk technologies, including sedimenta...The Jiaozhou Bay is characterized by heavy eutrophication that is associated with intensive anthropogenic activities. Four core sediments from the Jiaozhou Bay are analyzed using bulk technologies, including sedimentary total organic carbon（TOC）, total nitrogen（TN）, the stable carbon（δ13C） and nitrogen（δ15 N） isotopic composition to obtain the comprehensive understanding of the source and composition of sedimentary organic matter and further shed light on the environmental changes of the Jiaozhou Bay on a centennial time scale.Results suggest that the TOC and TN concentrations increase in the upper core, having indicated a probable eutrophication process since the 1920 s in the inner bay and the 2000 s in the bay mouth. The TOC and TN concentrations outside the bay have also changed since 1916 owing to the variation of terrigenous input.Considering TOC/TN ratio, δ13 C and δ15 N, it can be concluded there is a mixture of terrigenous and marine organic matter sources in the study area. A simple two end-member（terrigenous and marine） mixing model usingδ13 C indicats that 45%–79% of TOC in the Jiaozhou Bay is from the marine source. The environmental changes of the Jiaozhou Bay are recorded by geochemical proxies, which are influenced by the intensive anthropogenic activities（e.g., extensive use of fertilizers, and discharge of sewage） and climate changes（e.g., rainfall）.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2018YFC1508001)the National Natural Science Foundation of China(Grant No.51709073)the Fundamental Research Funds for the Central Universities of China(Grant No.B220202031).
文摘Estimating the design flood under nonstationary conditions is challenging. In this study, a sample reconstruction approach was developed to transform a nonstationary series into a stationary one in a future time window (FTW). In this approach, the first-order moment (EFTW) of an extreme flood series in the FTW was used, and two possible methods of estimating EFTW values in terms of point values and confidence intervals were developed. Three schemes were proposed to analyze the uncertainty of design flood estimation in terms of sample representativeness, uncertainty from EFTW estimation, and both factors, respectively. To investigate the performance of the sample reconstruction approach, synthesis experiments were designed based on the annual peak series of the Little Sugar Creek in the United States. The results showed that the sample reconstruction approach performed well when the high-order moment of the series did not change significantly in the specified FTW. Otherwise, its performance deteriorated. In addition, the uncertainty of design flood estimation caused by sample representativeness was greater than that caused by EFTW estimation.
基金Under the auspices of the National Natural Science Foundation of China(No.41971116,42271046,42277449)Fundamental Research Funds for the Central Universities(No.2020TS102)。
文摘The Zoige Basin,located in the eastern region of the Tibetan Plateau of China,is characterized by its climate sensitivity and complex surface environment.It is vital to understand the response of the surface processes to environmental changes in the Zoige Basin since the last deglaciation,as well as the response of environmental changes and surface processes on the Tibetan Plateau relate to global changes.In August 2020,a field investigation was conducted in the Zoige Basin.A complete set of stratigraphic profile from the high platform at the front of the glacial-diluvial fan in the Maqu reach of the western basin was selected as the research subject.Optically stimulated luminescence(OSL)dating samples and sedimentary samples were collected from key layers and brought back to the laboratory for experimental analysis,and the surface processes and environment changes since the last deglaciation in the Zoige Basin were investigated through particle size analysis and OSL dating.The results showed that during the last glacial period before 14.5 kyr,a substantial glacial-alluvial fan composed of sand and gravel layers was formed by flash flood processes triggered by glacial meltwater and heavy precipitation.In the Bølling-Allerød warm period of 14.5–11.7 kyr,a warm and humid climate prevailed,with the formation of silty bog environments in the shallow depressions at the glacial-alluvial fan's forefront and the development of gray-green bog soil deposits.However,during the Younger Dryas period,an abrupt climate deterioration occurred,with the upper section of the gray-green bog soil layer in the shallow depression to experience folding and deformation due to surface freeze-thaw actions.During the early Holocene period from 11.7 kyr to 8.5 kyr,the climate was relatively dry,resulting in prevalent aeolian sand activitities.Coarse silt accumulated in the shallow depression,and sedimentary facies alternating between aeolian sand and bog soil deposits developed owing to strong wind patterns on the plateau surface.In the warm and humid period from 8.5 kyr to 3.1 kyr,increased weathering and pedogenesis enhanced clay content in sediments,which developed into the paleosol.In the late Holocene,starting from 3.1 kyr,the climate became relatively dry once more,with aeolian sand activity prevalent.The coarse silt that accumulated during the late Holocene transformed into subalpine meadow black soil because of rising temperature and humidity levels.These findings indicated that the developmental process of the high platform in the Maqu reach of the Zoige Basin,which was significant for understanding the environmental changes and surface processes in the source region of the Yellow River since the last deglaciation.
文摘Environmental conditions change constantly either by anthropogenic perturbation or naturally across space and time.Often,a change in behavior is the frst response to changing conditions.Behavioral fexibility can potentially improve an organism’s chances to survive and reproduce.Currently,we lack an understanding on the time-scale such behavioral adjustments need,how they actually affect reproduction and survival and whether behavioral adjustments are suffcient in keeping up with changing conditions.We used house mice(Mus musculus)to test whether personality and life-history traits can adjust to an experimentally induced food-switch fexibly in adulthood or by intergenerational plasticity,that is,adjustments only becoming visible in the offspring generation.Mice lived in 6 experimental populations of semi-natural environments either on high or standard quality food for 4 generations.We showed previously that high-quality food induced better conditions and a less risk-prone personality.Here,we tested whether the speed and/or magnitude of adjustment shows condition-dependency and whether adjustments incur ftness effects.Life-history but not personality traits reacted fexibly to a food-switch,primarily by a direct reduction of reproduction and sloweddown growth.Offspring whose parents received a food-switch developed a more active stress-coping personality and gained weight at a slower rate compared with their respective controls.Furthermore,the modulation of most traits was condition-dependent,with animals previously fed with high-quality food showing stronger responses.Our study highlights that life-history and personality traits adjust at different speed toward environmental change,thus,highlighting the importance of the environment and the mode of response for evolutionary models.
基金The National Natural Science Foundation of China under contract No.42206161the Natural Science Foundation of Hebei Province under contract No.D2022407004+1 种基金the Science Research Project of Hebei Education Department under contract No.QN2022167the Open Fund Project of Hebei Key Laboratory of Ocean Dynamics,Resources and Environments under contract No.HBHY04.
文摘Understanding the dynamics of phytoplankton communities in coastal zones is crucial for the management and conservation of coastal ecosystems.Previous research indicated that the phytoplankton community structure and dominant taxa in the Bohai Sea(BHS)have exhibited significant shifts from the 1990s to the early 2010s in response to environmental changes,especially the change in nutrient structure.This study comprehensively investigated the variations in net-collected phytoplankton(>76μm)community structure,diversity,and environmental factors in the BHS during the late summers of 2011-2020,aiming to understand the recent trend in phytoplankton community structure and to explore the interactions between the communities and the environment.During the study period,the nutrient status in the BHS was characterized by a decrease in dissolved inorganic nitrogen(DIN)concentration,an increase in dissolved inorganic phosphorus(DIP)concentration,and a return of the nitrogen-to-phosphorus(N/P)molar ratio(hereinafter referred to as N/P ratio)to the Redfield ratio since 2016.The eutrophication index(EI)in the BHS remained stable and was generally at a low level(<1).The Dia/Dino index fluctuated but did not show an obvious trend.Overall,the eutrophication,the imbalance in nutrient ratio,and the shift in phytoplankton community structure did not continue during the study period.The increased abundance of phytoplankton was strongly associated with elevated concentrations of DIN,as well as higher N/P and nitrogen-to-silicon(N/Si)ratios,whereas the greater diversity was strongly linked to higher concentrations of DIP.Diatoms and dinoflagellates showed significant differences in their interactions with the environment,and their relative dominance was related to water column depth and stratification intensity;their impacts on the phytoplankton community diversity were also significantly different.The variations of certain dominant species,i.e.,Skeletonema costatum,Paralia sulcata,and Tripos longipes,exhibited strong links to the changes in nutrient structure in the BHS.The findings of this study contribute to understanding the regional environmental changes and provide insights into the adaptive strategies of coastal ecosystems in response to environmental shifts and fluctuations.
基金supported by the National Natural Science Foundation of China(No:41771245).
文摘The accumulation processes of loess in northeastern(NE)China record the varying characteristics of the East Asian Monsoons(EAM)and the evolution of the local environment.In this study,grain size end-member analysis of the Dajiugang(DJG)section deposited since the Last Glacial in Chifeng City,NE China was used to reveal the dynamic depositional characteristics of loess and environmental evolution of NE China.Results showed that the Chifeng loess comprises three grain size end-members(EM),EM1(7.38μm),EM2(49.4μm)and EM3(90.00μm),indicating the three transport dynamics of dust delivered to the region.The EM1 represents atmospheric dust as the background.The EM2,mainly derived from relatively distant-sources deposition,and EM3,material transported over a short distance,correspond to the intensity of southwesterly winds and the East Asian Winter Monsoon(EAWM),respectively.Results of climate reconstruction,combined with other records,showed that the climate was generally cold and dry with a strong EAWM and a weak East Asian summer monsoon(EASM)during the stadial-period[Marine Isotope Stage(MIS)4 and MIS 2 stage].The climate was predominantly warm and humid,with weak EAWM and surface winds and strong EASM in interstadial-period(MIS 3 and MIS 1 stage).Comparisons between indicators,e.g.,EM3,the LR04 benthicδ18O stack and summer insolation at 65°N suggest that the strong EAWM is induced by increasing the Northern Hemisphere ice volume and reduced summer solar radiation.
基金Supported by National Natural Science Foundation(40871093)~~
文摘Particle size, the contents of carbonate and TOC were analyzed on lake sediments from a short core in Hongjiannao Lake to discuss the environmental changes during the past decades. On the basis of the records in lake sediments and comparison with the meteorological data of Yulin region, the environmental changes in Hongjiannao Lake were approximately divided into two stages. In stage A （1957 -1996）, the lake evolution and the environmental change were mainly influenced by natural factors. It contains three sub-stages： A1 （1957-1969）, a period of lake expansion, A2 （1969-1990）, a stable period with high lake levels, and A3 （1990 -1996）, a period of gradual extraction of the lake. In stage B （1996 -2005）, the lake area still keeps diminishing. During this period, organic matter increased rapidly due to the input of nutrient elements in the catchment. The carbonate content, however, decreased. As the precipitation was decreasing and the temperature was increasing, the decrease of carbonate content could not be explained by either temperature or precipitation change.
基金National Natural Science Foundation of China,No.42207078CUG Scholar-Scientific Research Funds at China University of Geosciences(Wuhan),No.2022166+1 种基金China Scholarship Council,No.202306410026Opening Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin,China Institute of Water Resources and Hydropower Research,No.IWHR-SKL-KF202217。
文摘Wetlands play a critical role in the global environment.The Middle Yangtze River Basin(MYRB),known for its abundant wetland resources,has experienced notable changes resulting from the complex interplay of environmental factors.Therefore,we investigated the spatiotemporal characteristics of wetland ecological quality in the MYRB from 2001 to 2020.Utilizing the random forest(RF)regression algorithm and patch-generated land-use simulation(PLUS)model,we forecasted variations in wetland habitat quality and their determinants under the Shared Socioeconomic Pathway-Representative Concentration Pathway(SSPRCP)framework from 2035 to 2095.The main findings are as follows:(1)The RF algorithm was optimal for land-use and land-cover(LULC)classification in the MYRB from 2001 to 2020,when notable changes were observed in water bodies and buildings.However,the forested area exhibited an increase and decrease of 3.9%and 1.2%under the SSP1-2.6 and SSP5-8.5 scenarios,respectively,whereas farmland exhibited a diminishing trend.(2)Wetlands were primarily concentrated in the central and eastern MYRB,with counties in the southwest exhibiting superior ecological-environmental quality from 2001 to 2020.Notably,wetland coverage revealed significantly high level,significant changes,frequent but relatively minor changes under the SSP1-2.6,SSP2-4.5,and SSP 5-8.5 scenarios,respectively.(3)Regions with lower habitat quality were primarily concentrated in urbanized areas characterized by frequent human activities,indicating a clear degradation in habitat quality across different scenarios.In conclusion,we established a foundational framework for future investigations into the eco-hydrological processes and ecosystem quality of watersheds.
文摘Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the world.JMS mainly publishes academic and technical papers concerning environmental changes and sustainable development in mountain areas under natural conditions or/and with the influence of human activities.It also accepts book reviews,commentary,and reports on mountain research and introductions to mountain research organizations.
文摘Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the world.JMS mainly publishes academic and technical papers concerning environmental changes and sustainable development in mountain areas under natural conditions or/and with the influence of human activities.It also accepts book reviews,commentary,and reports on mountain research and introductions to mountain research organizations.
文摘Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the world.JMS mainly publishes academic and technical papers concerning environmental changes and sustainable development in mountain areas under natural conditions or/and with the influence of human activities.It also accepts book reviews,commentary,and reports on mountain research and introductions to mountain research organizations.
文摘Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the world.JMS mainly publishes academic and technical papers concerning environmental changes and sustainable development in mountain areas under natural conditions or/and with the influence of human activities.It also accepts book reviews,commentary,and reports on mountain research and introductions to mountain research organizations.
文摘Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the world.JMS mainly publishes academic and technical papers concerning environmental changes and sustainable development in mountain areas under natural conditions or/and with the influence of human activities.It also accepts book reviews,commentary,and reports on mountain research and introductions to mountain research organizations.
基金National Natural Science Foundation of China,No.42171160。
文摘Lacustrine sedimentary nitrogen isotope(δ^(15)N)records offer crucial insights into the impacts of regional anthropogenic activities and environmental changes on nitrogen cycling dynamics within the context of global climate change.This study summarized δ^(15)N data from 27 Chinese lakes since 1750 CE,categorizing them into Types Ⅰ(eastern and southern China,densely populated area)and Ⅱ(Northwestern China[NWC]and the Qinghai-Tibet Plateau[QTP],sparsely populated area).The results showed pronounced regional and temporal variability in nitrogen isotope trends.Type Ⅰ lakes exhibited a significant positive δ^(15)N deviation post-1950 CE,linked to population growth(r=0.91,p<0.01)and economic development,with mitigation after 2000 CE likely due to enhanced environmental policies.Conversely,Type Ⅱ lakes showed coherent δ^(15)N variations with natural climate change from 1750 to 1950 CE,followed by a post-1950 CE decline exceeding natural variability.This shift is attributed to a“warming-wetting trend”in NWC and the QTP,which presumably increased terrestrial productivity,altered nitrogen cycling,and enhanced ^(15)N-depleted nitrogen input via surface runoff.Rising temperatures may have enhanced the activity and abundance of nitrogen-fixing microorganisms,jointly driving a negative δ^(15)N shift.This study highlights climate conditions and anthropogenic activities as key drivers of nitrogen cycle perturbations in China,with their influences varying spatiotemporally,thereby providing crucial insights into the nitrogen cycling dynamics in Chinese lakes.
基金National Natural Science Foundation of China, No.41071008
文摘Environments in arid and semiarid regions are extremely sensitive to climate changes. High wind activity in these regions has resulted in an extensively developed arid geomorphology, but past environmental changes are poorly understood because of the absence of relatively high-resolution proxies. The accumulation characteristics of nebkhas, which have developed extensively in these regions, can be used as a method of reconstructing environmental changes. Here we summarized recent advances in research on the formation, development, and sediment characteristics of nebkhas and their significance to environmental changes in arid and semiarid regions. Based on the studies of our colleagues, we suggested that research on nebkha formation can provide distinct clues about environmental changes in arid and semiarid regions; however, continued studies are needed.
基金the National Key Basic Research Support Foundation of China (No. G1999043407), the KnowledgeInnovation Project of the Chinese Academy of Sciences (Nos. KZCX1-SW-01-12 and KSCX2-1-07) and the NationalNatural Science Foundation of China (No. 40231018).
文摘Based on data from a field survey in 2001 along the Northeast China transect (NECT), a precipitation gradient,and a short-term simulation experiment under ambient CO2 of 350 μmol mol-1 and doubled CO2 of 700 μmol mol-1with different soil moisture contents of 30%-45%, 45%-60%, and 60%-80% soil water holding capacity, the distributionof soil organic carbon and labile carbon along the NECT, their relationships with precipitation and their responses toCO2 enrichment and soil moisture changes were analyzed. The results indicated that the soil labile carbon along thegradient was significantly related to soil organic carbon (r = 0.993, P < 0.001). The soil labile carbon decreased morerapidly with depth than organic carbon. The soil organic and labile carbon along the gradient decreased with decrease inlongitude in both the topsoils and subsoils, and the coefficient of variation for the labile carbon was greater than that forthe organic carbon. Both the soil organic carbon and labile carbon had significant linear relationships with precipitation,with the correlation coefficient of soil organic carbon being lower (0.677 at P < 0.001) than that of soil labile carbon(0.712 at P < 0.001). In the simulation experiment with doubled and ambient CO2 and different moisture contents, thecoefficient of variation for soil organic carbon was only 1.3%, while for soil labile carbon it was 29.7%. With doubled CO2concentration (700 μmol mol-1), soil labile carbon decreased significantly at 45% to 60% of soil moisture content. Theseindicated that soil labile carbon was relatively more sensitive to environmental changes than soil organic carbon.
基金National Natural Science Foundation of China,No.41171134 National Social Science Funds Special Commission Project of China,No.2007@ZH005 Key Project of National Soft Science of China,No.2700ZXQ4D166
文摘Over the past two decades in China, stress on the environment has increased continuously. This paper will assess the change in environmental quality over time, and its spatial variation using data from the statistical yearbooks of 31 provincial administrative regions in 1990, 1995, 2000, 2005, and 2010. These books provide a general assessment of the environment at the provincial level, and the three major economic regions from western to eastern China. By using the geographic information system （GIS） and SPSS, we analyzed the changing trend of China＇s eco-environment and calculated the changing trajectory in the gravity center of the eco-environmental quality. We conclude the following. （1） From 1990 to 2010, the rate of deterioration of the environment went down. We argue that the cause of this trend was neither the result as ＂the deterioration trend was under control＂ noticed by the government departments concerned, nor ＂the deterioration rate of the environment was increasingly intensified＂ suggested by many researchers. （2） Since 1990, the general environment has been worsening in China, but it was improved in some regions; however, the ecological deficit is still expanding and will last for a long time. （3） From western to eastern China, the deterioration rate of environmental quality was slowed down. The reasons include a good natural environment, a developed regional economy, and technology and finance in eastern China. （4） After extensive economic development in China, there are imbalances of population, economy, society, and the environment in the 31 provincial regions. The governments at all levels should play an important role in research and protecting the environment. In addition, it is imperative to implement positive measures such as controlling population, improving the environment, and promoting smart development to balance the socio-ecological system.
基金Major Program of National Social Science Foundation of China, No.11＆ZD183 National Key Project of Scientific and Technical Supporting Program of China, No.2013BAK08B02 National Natural Science Foundation of China, No.41171006
文摘The Xiaohe Cemetery archaeological site （Cal. 4-3.5 ka BP） is one of the most important Bronze Age sites in Xinjiang, China. Although the surrounding environment is an extremely arid desert now, abundant archaeological remains indicate that human occupation was common during certain periods in the Holocene. Field investigations and laboratory analyses of a sediment profile near the Xiaohe Cemetery indicate that while the regional environment was arid desert throughout the Holocene there were three episodes of lake forma- tion near the site in the periods 4.8-3.5 ka BP, 2.6-2.1 ka BP and 1.2-0.9 ka BP. Geomorphic and hydrological investigations reveal that a lake or lakes formed in a low-lying area when water was derived initially from the Kongque River and then shunted into the Xiaohe River basin. Low amounts of active chemical elements in lacustrine sediment between 4.8-3.5 ka BP indicate abundant and continuous water volume in the lake; the content of active chemical elements increased between 2.6-2.1 ka BP but was still at a relatively low level, suggesting a declining amount of water and diminished inflow. Between 1.2-0.9 ka BP there was a very high content of active elements, suggesting decreased water volume and indicating that the lake was stagnate. In contrast, the general climate condition shows that there had a warm-humid stage at 8-6 ka BP, a cool-humid stage at 6-2.9 ka BP and a warm-dry stage at 2.9-0.9 ka BP in this region. The hydrological evolutions around Xiaohe Cemetery did not have one-to-one correspondence with climate changes. Regional comparison indicates that broad-scale climatic conditions played an important role through its influences on the water volume of the Tarim River and Kongque River. But, the formation of the lakes and their level were controlled by geomorphic conditions that influenced how much water volume could be shunted to Xiaohe River from Kongque River. Human occupation of the Xiaohe Cemetery and nearby regions during the Bronze Age and Han-Jin period （202 BC-420 AD） corresponded to the two earlier lake periods, while no human activities existed in the third lake period because of the decreased water volume.
基金The National Basic Research Program of China(973 Program)under contract No.2010CB951200the Marine Public Service Specific Research under contract No.201105020
文摘Controlled by climate changes, there were three large-scale transgressions and regressions around the Bohai Sea during the late Quaternary, which were accepted by most geologists. However, a big controversy still exists about the time when the transgressions occurred separately. In order to find out the process of the paleoenvironmental changes around the Bohai Sea in the late Quaternary, the foraminifera assemblages from a new borehole Lz908 in the southern coast of the Laizhou Bay were studied, and then the transgressive strata were indentified. Combined with accelerator mass spectrometry radiocarbon 14C（AMS14C） and optically stimulated luminescence（OSL） ages, the occurrence time of these transgressions were re-determined. The result showed that three major large-scale transgressions occurred separately at the beginning of marine isotopic stage 7（MIS7）, the last interglacial period（MIS5） and the Holocene. In addition, a small-scale transgression occurred in the mid-MIS6, and the corresponding transgressive stratum was deposited. The transgressive deposition of MIS3 was also discovered in this study. However, the characteristics of the foraminifera indicated the environment during this period was colder than that in the MIS5. By comparison with the global sea-level changes, the paleoenvironmental changes around the Bohai Sea in the late Quaternary can be consistent with the global climate changes.
基金The Joint Fund between Natural Science Foundation of China and Shandong Province under contract No.U1606404the National Basic Research Program(973 Program)of China under contract Nos 2015CB452901 and 2015CB452902+1 种基金the National Key Research and Development Plan Sino-Australian Centre for Healthy Coasts under contract No.2016YFE0101500the Program for Aoshan Excellent Scholars of Qingdao National Laboratory for Marine Science and Technology of China under contract No.2015ASTP-OS13
文摘The Jiaozhou Bay is characterized by heavy eutrophication that is associated with intensive anthropogenic activities. Four core sediments from the Jiaozhou Bay are analyzed using bulk technologies, including sedimentary total organic carbon（TOC）, total nitrogen（TN）, the stable carbon（δ13C） and nitrogen（δ15 N） isotopic composition to obtain the comprehensive understanding of the source and composition of sedimentary organic matter and further shed light on the environmental changes of the Jiaozhou Bay on a centennial time scale.Results suggest that the TOC and TN concentrations increase in the upper core, having indicated a probable eutrophication process since the 1920 s in the inner bay and the 2000 s in the bay mouth. The TOC and TN concentrations outside the bay have also changed since 1916 owing to the variation of terrigenous input.Considering TOC/TN ratio, δ13 C and δ15 N, it can be concluded there is a mixture of terrigenous and marine organic matter sources in the study area. A simple two end-member（terrigenous and marine） mixing model usingδ13 C indicats that 45%–79% of TOC in the Jiaozhou Bay is from the marine source. The environmental changes of the Jiaozhou Bay are recorded by geochemical proxies, which are influenced by the intensive anthropogenic activities（e.g., extensive use of fertilizers, and discharge of sewage） and climate changes（e.g., rainfall）.
