Mangrove wetlands are a vital component of the blue carbon ecosystem,which is of great significance to coastal ecosystems and the global carbon balance.However,mangrove forests worldwide face a combination of natural ...Mangrove wetlands are a vital component of the blue carbon ecosystem,which is of great significance to coastal ecosystems and the global carbon balance.However,mangrove forests worldwide face a combination of natural and anthropogenic threats.This study employs highresolution sedimentology,geochemistry,and pollen analysis to reveal the sedimentary evolution and vegetation succession in the mangrove wetland of Dongzhai Harbor,Hainan Island.By utilizing multiple proxies,including^(14)C chronology,δ^(13)C,C/N,and the chemical index of alteration(CIA),we identified three distinct stages in the sedimentary records spanning from the Late Pleistocene to the modern age.Prior to the last glaciation,during the Late Pleistocene,the study area exhibited marine carbonate facies,with an abundance of marine-derived organic matter.During the low sea-level stage of the last glaciation,the strata in the core location were exposed.Following the last glaciation,the study area gradually transitioned into intertidal settings in response to fluctuating sea levels.Since the Middle Holocene or even earlier,sedimentary organic matter continued to accumulate as terrestrial C3 vegetation and mangrove forests established,persisted,and developed.This period witnessed the formation of the current estuarine environment.Simultaneously,the pioneering mangrove species,probably represented by Avicennia,might be initially established,followed by Rhizophora,Bruguiera and Ceriops communities,ultimately being replaced by Kandelia obovata to date.These findings not only fill the gap in the study of paleo-mangroves in China but also contribute valuable knowledge to the global reconstruction of paleo-mangroves,providing crucial reference for the conservation of mangroves and prediction of their responses in the context of climate change.展开更多
Mangrove wetlands are among the four most productive tropical and subtropical ecosystems.They are also a core component of the coastal blue carbon ecosystem,which is of great ecological significance to human beings,pl...Mangrove wetlands are among the four most productive tropical and subtropical ecosystems.They are also a core component of the coastal blue carbon ecosystem,which is of great ecological significance to human beings,plants,animals,and the global carbon balance.There has been a global decrease in the distribution of mangrove forests,and their ecological function has gradually degenerated since the Holocene.Sediment from coastal mangrove wetlands can provide records of climate change and human activities,and multiple proxies including palynology,leaf fossil,biomarkers,DNA,phytolith and stable isotopes,can be used to reconstruct the evolutionary stages of paleo-mangroves and to identify the effect of natural processes and human activities on the distribution and evolution of mangroves.This information can provide theoretical support for mangrove protection and for improving carbon sequestration capacity.This paper summarizes and compares the multiple proxies for mangrove reconstruction,reviews progress in the study of natural succession of global mangroves since the Holocene,expands on the influence mechanisms of human activities on mangrove growth and development and uses past information to lay a foundation for a model to predict future mangrove development.展开更多
A relatively high resolution pollen record and data of loss of ignition(LOI),grain size and susceptibility of the Daxigou profile in the head area of the Urumqi River.central Tianshan Mountains,revealed new informatio...A relatively high resolution pollen record and data of loss of ignition(LOI),grain size and susceptibility of the Daxigou profile in the head area of the Urumqi River.central Tianshan Mountains,revealed new information about vegetation changes and environmental evolution since 3.6 ka BP.Results showed that from 3.6 ka BP to present,climate was unstable with multi-changes of warming-cooling and wetting-drying.From ca.3.6 to 3.2 ka BP,climate was warmer and more humid than today.Climate changed to cooler and drier between ca.3.2 and 2.0 ka BP.coinciding with a glacier advance in the head area of the Urumqi River.From ca.2.0 to 1.4 ka BP.climate became warmer and more humid again.From ca.1.4 to 0.5 ka BP temperature and humidity went on increasing and a period of Climatic Optimum since 3.6 ka BP might occur.A few limnetic hydrophytes pollen are counted for all zones,indicating a freshwater habitat since 3.6 ka BP in this region.Based on synthetically analysis of ecological characteristics and dispersal of spruce pollen.the abundance of Picea is influenced by treeline moving upward,valley wind and glacier ablation.Statistics of charcoal concentration and susceptibility further suggest that fires may have occurred in this region since 0.5 ka BP and the peak value of charcoal might be related to human activities.展开更多
Short sediment cores retrieved from Bosten Lake, the largest inland freshwater lake in China, were used to explore humidity and precipitation variations in arid central Asia during the past millennium. The chronology ...Short sediment cores retrieved from Bosten Lake, the largest inland freshwater lake in China, were used to explore humidity and precipitation variations in arid central Asia during the past millennium. The chronology of the cores was established using 137Cs, 210Pb and AMS 14C dating re- sults. Multi-proxy high-resolution analysis, including pollen ratios of Artemisia and Chenopodiaceae (A/C), carbonate content and grain size, indicates that the climate during the past millennium can be divided into three stages: a dry climate between 1000―1500 AD, a humid climate during the Little Ice Age (LIA) (c. 1500―1900 AD), and a warm dry period after 1900 AD. On centennial timescales, the climate change in northwestern China during the past 1000 years is characterized by oscillations between warm-dry and cold-humid climate conditions. All the proxies changed significantly and indi- cate increased precipitation during the LIA, including increased pollen A/C ratios and pollen concen- trations, decreased carbonate content and increased grain size. The humid period during the LIA re- corded by the Bosten Lake sediments is representative of arid central Asia and is supported by nu- merous records from other sites. During the LIA, the water runoff into the Keriya River and Tarim River in the Tarim Basin increased, while the ice accumulation in the Guliya ice core increased. Additionally, the lake levels of the Aral and Caspian Sea also rose, while tree-ring analysis indicates that precipita- tion increased. We hypothesize that both the lower temperature within China and the negative anomalies of North Atlantic Oscillation (NAO) during this period may have contributed to the humid climate within this area during LIA.展开更多
Lake Chany is the largest endorheic lake in Siberia whose catchment is entirely on the territory of Russia.Its geographical location on the climate-sensitive boundary of wet and dry landscapes provides an opportunity ...Lake Chany is the largest endorheic lake in Siberia whose catchment is entirely on the territory of Russia.Its geographical location on the climate-sensitive boundary of wet and dry landscapes provides an opportunity to gain more knowledge about environmental changes in the West Siberian interior during the Holocene and about the evolution of the lake itself.Sediment cores obtained from the Yarkov subbasin of the lake in 2008 have been comprehensively studied by a number of approaches including sedimentology and AMS dating,pollen,diatom and chironomid analyses(with statistical interpretation of the results),mineralogy of authigenic minerals and geochemistry of plant lipids(biomarker analysis.).Synthesis of new results presented here and published data provides a good justification for our hypothesis that Lake Chany is very young,no older than 3.6 ka BP.Before that,between 9 and 3.6 ka BP,the Chany basin was a swampy landscape with a very low sedimentation rate;it could not be identified as a water body.In the early lake phase,between 3.6 and 1.5 ka BP,the lake was shallow,1.2–3.5 m in depth,and it rose to its modern size,up to 6.5 m in depth,during the last millennium.Our data reveal important changes in the understanding of the history of this large endorheic lake,as before it was envisioned as a large lake with significant changes in water level since ca.14 ka BP.In addition to hydrology,our proxies provide updates and details of the regional vegetation and climate change since ca.4 ka BP in the WestSiberian forest-steppe and steppe.As evolution of the Chany basin is dependent on hydroclimatic changes in a large region of southern West Siberia,we compare lake-level change and climate-change proxies from the other recently and most comprehensively studied lakes of the region.展开更多
基金financially supported by the National Natural Science Foundation of China(No.U2244225)the Fundamental Research Funds for the Central Universities,China University of Geosciences and China Geological Survey(No.DD20211391)。
文摘Mangrove wetlands are a vital component of the blue carbon ecosystem,which is of great significance to coastal ecosystems and the global carbon balance.However,mangrove forests worldwide face a combination of natural and anthropogenic threats.This study employs highresolution sedimentology,geochemistry,and pollen analysis to reveal the sedimentary evolution and vegetation succession in the mangrove wetland of Dongzhai Harbor,Hainan Island.By utilizing multiple proxies,including^(14)C chronology,δ^(13)C,C/N,and the chemical index of alteration(CIA),we identified three distinct stages in the sedimentary records spanning from the Late Pleistocene to the modern age.Prior to the last glaciation,during the Late Pleistocene,the study area exhibited marine carbonate facies,with an abundance of marine-derived organic matter.During the low sea-level stage of the last glaciation,the strata in the core location were exposed.Following the last glaciation,the study area gradually transitioned into intertidal settings in response to fluctuating sea levels.Since the Middle Holocene or even earlier,sedimentary organic matter continued to accumulate as terrestrial C3 vegetation and mangrove forests established,persisted,and developed.This period witnessed the formation of the current estuarine environment.Simultaneously,the pioneering mangrove species,probably represented by Avicennia,might be initially established,followed by Rhizophora,Bruguiera and Ceriops communities,ultimately being replaced by Kandelia obovata to date.These findings not only fill the gap in the study of paleo-mangroves in China but also contribute valuable knowledge to the global reconstruction of paleo-mangroves,providing crucial reference for the conservation of mangroves and prediction of their responses in the context of climate change.
基金financially supported by the Geological Survey Project of China Geological Survey(No.DD20190304)。
文摘Mangrove wetlands are among the four most productive tropical and subtropical ecosystems.They are also a core component of the coastal blue carbon ecosystem,which is of great ecological significance to human beings,plants,animals,and the global carbon balance.There has been a global decrease in the distribution of mangrove forests,and their ecological function has gradually degenerated since the Holocene.Sediment from coastal mangrove wetlands can provide records of climate change and human activities,and multiple proxies including palynology,leaf fossil,biomarkers,DNA,phytolith and stable isotopes,can be used to reconstruct the evolutionary stages of paleo-mangroves and to identify the effect of natural processes and human activities on the distribution and evolution of mangroves.This information can provide theoretical support for mangrove protection and for improving carbon sequestration capacity.This paper summarizes and compares the multiple proxies for mangrove reconstruction,reviews progress in the study of natural succession of global mangroves since the Holocene,expands on the influence mechanisms of human activities on mangrove growth and development and uses past information to lay a foundation for a model to predict future mangrove development.
文摘A relatively high resolution pollen record and data of loss of ignition(LOI),grain size and susceptibility of the Daxigou profile in the head area of the Urumqi River.central Tianshan Mountains,revealed new information about vegetation changes and environmental evolution since 3.6 ka BP.Results showed that from 3.6 ka BP to present,climate was unstable with multi-changes of warming-cooling and wetting-drying.From ca.3.6 to 3.2 ka BP,climate was warmer and more humid than today.Climate changed to cooler and drier between ca.3.2 and 2.0 ka BP.coinciding with a glacier advance in the head area of the Urumqi River.From ca.2.0 to 1.4 ka BP.climate became warmer and more humid again.From ca.1.4 to 0.5 ka BP temperature and humidity went on increasing and a period of Climatic Optimum since 3.6 ka BP might occur.A few limnetic hydrophytes pollen are counted for all zones,indicating a freshwater habitat since 3.6 ka BP in this region.Based on synthetically analysis of ecological characteristics and dispersal of spruce pollen.the abundance of Picea is influenced by treeline moving upward,valley wind and glacier ablation.Statistics of charcoal concentration and susceptibility further suggest that fires may have occurred in this region since 0.5 ka BP and the peak value of charcoal might be related to human activities.
文摘Short sediment cores retrieved from Bosten Lake, the largest inland freshwater lake in China, were used to explore humidity and precipitation variations in arid central Asia during the past millennium. The chronology of the cores was established using 137Cs, 210Pb and AMS 14C dating re- sults. Multi-proxy high-resolution analysis, including pollen ratios of Artemisia and Chenopodiaceae (A/C), carbonate content and grain size, indicates that the climate during the past millennium can be divided into three stages: a dry climate between 1000―1500 AD, a humid climate during the Little Ice Age (LIA) (c. 1500―1900 AD), and a warm dry period after 1900 AD. On centennial timescales, the climate change in northwestern China during the past 1000 years is characterized by oscillations between warm-dry and cold-humid climate conditions. All the proxies changed significantly and indi- cate increased precipitation during the LIA, including increased pollen A/C ratios and pollen concen- trations, decreased carbonate content and increased grain size. The humid period during the LIA re- corded by the Bosten Lake sediments is representative of arid central Asia and is supported by nu- merous records from other sites. During the LIA, the water runoff into the Keriya River and Tarim River in the Tarim Basin increased, while the ice accumulation in the Guliya ice core increased. Additionally, the lake levels of the Aral and Caspian Sea also rose, while tree-ring analysis indicates that precipita- tion increased. We hypothesize that both the lower temperature within China and the negative anomalies of North Atlantic Oscillation (NAO) during this period may have contributed to the humid climate within this area during LIA.
基金The biomarker analysis and all organic matter related interpretations were made in favor of the joint Russia-China research project,RFBR no.21-55-53037 and NSFC no.42111530031The lake level changes were investigated in favor of the RFBR project No.19-29-05085+6 种基金Numerical reconstruction of climate was made in the frame of ANSO Collaborative Research(ANSO-CR-PP-2021-02)The contribution by Natalia Rudaya matches interests of the RSF project no.20-17-00110the Tomsk State University Development Program(Priority 2030)financed by National Natural Science Foundation of China(grant no.41988101)the Sino-German Mobility Program(grant no.M-0359)Diatom and chironomid analyses were funded by the RSF project No.20-17-00135Databases developed with the support of the RSF No.22-17-00185 and 22-17-00113 projects were used for quantitative environmental reconstructions(WD and T July)and supplementary statistical research.
文摘Lake Chany is the largest endorheic lake in Siberia whose catchment is entirely on the territory of Russia.Its geographical location on the climate-sensitive boundary of wet and dry landscapes provides an opportunity to gain more knowledge about environmental changes in the West Siberian interior during the Holocene and about the evolution of the lake itself.Sediment cores obtained from the Yarkov subbasin of the lake in 2008 have been comprehensively studied by a number of approaches including sedimentology and AMS dating,pollen,diatom and chironomid analyses(with statistical interpretation of the results),mineralogy of authigenic minerals and geochemistry of plant lipids(biomarker analysis.).Synthesis of new results presented here and published data provides a good justification for our hypothesis that Lake Chany is very young,no older than 3.6 ka BP.Before that,between 9 and 3.6 ka BP,the Chany basin was a swampy landscape with a very low sedimentation rate;it could not be identified as a water body.In the early lake phase,between 3.6 and 1.5 ka BP,the lake was shallow,1.2–3.5 m in depth,and it rose to its modern size,up to 6.5 m in depth,during the last millennium.Our data reveal important changes in the understanding of the history of this large endorheic lake,as before it was envisioned as a large lake with significant changes in water level since ca.14 ka BP.In addition to hydrology,our proxies provide updates and details of the regional vegetation and climate change since ca.4 ka BP in the WestSiberian forest-steppe and steppe.As evolution of the Chany basin is dependent on hydroclimatic changes in a large region of southern West Siberia,we compare lake-level change and climate-change proxies from the other recently and most comprehensively studied lakes of the region.
