Earth is moving through a period of extreme uncertainty as global climates change,natural disasters become more frequent and severe,and governments grapple with the difficulty these issues pose for managing natural re...Earth is moving through a period of extreme uncertainty as global climates change,natural disasters become more frequent and severe,and governments grapple with the difficulty these issues pose for managing natural resources and people.Nowhere are these challenges more pressing than across the world's drylands,where a combination of hotter drier climates challenge food security,sustainable food production and often fuel unrest and political instability.It is against this backdrop that Fu and Stafford Smith,two global leaders in dryland science draw on>80 years of collective wisdom on drylands to describe how humans and natural processes intersect in an era of global change(Fu and Stafford Smith,2024).展开更多
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
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
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 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
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 East China Sea continental shelf is a unique area for the study of land-sea interactions and paleoenvironmental change because it receives a large amount of terrestrial material inputs. In recent decades, human ac...The East China Sea continental shelf is a unique area for the study of land-sea interactions and paleoenvironmental change because it receives a large amount of terrestrial material inputs. In recent decades, human activities and global climate change have greatly aff ected river discharges into the sea. However, changes in the deposition process caused by these factors in the East China Sea continental shelf are unclear. We collected eight short sediment cores from the East China Sea inner shelf(ECSIS) using a box core sampler in 2012 and 2015. The grainsize, 2 10 Pb, and 1 37 Cs of these cores were analyzed in order to reconstruct the deposition history since the 1950 s, and to reveal human activity and climate change influences on sediment deposition in the ECSIS. Results indicated that sediment grain size became finer after 1969, turned coarser after 1987, and then further coarser since 2003, corresponding well to the three steps of sediment load drop in the Changjiang(Yangtze) River, which are mainly caused by human activities(particularly the closure of the Three Gorges Dam). Simultaneously, the East Asian Monsoon influenced the deposition process in the ECSIS by changing the intensity of coastal currents. Mean grain size variations in the fine-grained population(divided by grain size vs. standard deviation method) coincided with that of the East Asian Winter Monsoon strength and reflected its weakness in 1987. Abrupt changes in sediment grain size over a short time scale in these sediment cores were generally caused by floods and typhoons. Spectral analyses of the sediment cores showed periodicities of 10–11 and 20–22 years, corresponding to the periodicity of solar activity(Schwabe cycle and Hale cycle). Mean grain size time series also displayed a 3–8 year periodicity corresponding to El Ni?o Southern Oscillation periodic change.展开更多
Neolithic culture series in the Yishu River Basin developed in the order of Beixin culture-Dawenkou culture-Longshan culture-Yueshi culture. During the early and middle stage of Longshan culture （4600-4300 cal. yr BP...Neolithic culture series in the Yishu River Basin developed in the order of Beixin culture-Dawenkou culture-Longshan culture-Yueshi culture. During the early and middle stage of Longshan culture （4600-4300 cal. yr BP）, the climate in the Yishu River Basin was warm and wet. Paddy-oriented agriculture planted paddy was very developed. The society was flourishing with great amount of archaeological sites. The cooling starting in 4200 cal. yr BP made the paddies shortfall in output or even no seeds were gathered. This situation intensified the discrepancy between population and resource. The scarcity in natural resource led to substantial decrease in population and subsequent drop in archaeological sites. About 4000 cal. yr BP Longshan culture was displaced by Yueshi culture which was relatively un- derdeveloped, simple and unsophisticated.展开更多
At about 173 ka BP of the late period of mid-Pleistocene, the second terrace of the river had been formed as a result of uplift happening in Shangshan area because of the climate, sea level change and tectonic action....At about 173 ka BP of the late period of mid-Pleistocene, the second terrace of the river had been formed as a result of uplift happening in Shangshan area because of the climate, sea level change and tectonic action. Between 173-75 ka BP, aeolian deposited on the terrace, a layer of reticulate red clayey soil about 80-100 cm thick deposited and developed under the warmer and higher temperature. In the last glacial period, the drop of the temperature and the decrease of the precipitation induced the dust-storms increased, A layer of Xiashu loess about 1.0-1.5 m thick accumulated on Shangshan terrace in the last glacial, which has the reticulate red clayey soil buried. At the beginning of the Holocene （11500 a BP-）, temperature went higher gradually and precipitation got more, the pre-persons moved on the Shangshan terrace （11,400-8600 a BP）, which is one of the most important archaeological sites, and can connect the paleolithic culture with Neolithic culture. It could be assumed from the results that the lower reaches of the Yangtze River are the home of rice cultivation, too. The lower place to the west of the Shangshan site experienced the two cycles process of the fluvial facies and the lacustrine facies, indicating that the water source of the pre-historical Shangshan is the river water or lake water. Two AMS 14C age proved the water source disappeared more than 1000 years ago.展开更多
Previous studies carried out in the East China Sea （ECS） mud area focused on long-term environmental changes in sedimentary records during the Holoeene, especially during the mid-Holocene high-stand water levels per...Previous studies carried out in the East China Sea （ECS） mud area focused on long-term environmental changes in sedimentary records during the Holoeene, especially during the mid-Holocene high-stand water levels period. These results indicate that sensitive grain size groups can be used as a sedimentary proxy to reconstruct the evolution of the East Asian Winter Monsoon （EAWM）. The studies have been carried out mainly in the northern and middle portions of the Zhejiang-Fujian coastal mud, however, similar research in the southern portion and the comparison between sedimentary proxy and modern measured data of EAWM are lacking. In this paper, we focused on a sedimentary record of the past 100 years with an enhanced resolution of 1.8 years. Investigations of the southern end of the Zhejiang-Fujian coastal mud area were conducted on the basis of 21~Pb chronology, grain-size analysis and chemical element analysis. The correspondence between the mean grain size （Mz） of sediment sensitive grain size and the measured EAWM was confirmed for the first time. We found that during the recent 100 years, the variation of the mean grain size of the sensitive population in the southern portion of the Zhejiang-Fujian mud was mainly controlled by the EAWM intensity changes; and not directly related to changes in the sediment discharge from Datong station of the Changjiang River （DTSD）. Finally, recent changes in the content of heavy metals in study area reflect the impact of human activities on the environment.展开更多
The Huaihe River basin of Anhui is not only a transitional zone of physical geography, but also a convergent area of many cultures in China. It is one of the sensitive ecotones to global changes and the birthplace of ...The Huaihe River basin of Anhui is not only a transitional zone of physical geography, but also a convergent area of many cultures in China. It is one of the sensitive ecotones to global changes and the birthplace of Chinese civilization. Using the field archaeological data and the sporo-pollens and the age data of the drilling cores, we analysed Neolithic cultural development and environmental evolution in the Huaihe River basin of Anhui. According to the combination of some research results in archaeology with environmental evolution research, this paper discusses the relationship between culture and environment in the Huaihe River basin of Anhui. The Neolithic cultural development was strongly impacted by the environmental change. The primitive culture （Shishanzi） was developed in the beginning of the Holocene Megathermal Period with distinct regional feature of the culture. From 6.5 kaBP to 5.5 kaBP, the climate changed warmer and wetter. The frequent occurrence of flood and waterlog due to such a climate regime and high sea level caused the earth＇s surface environment deteriorated in the Huaihe River basin of Anhui and the interruption of the Neolithic cultural development, hence a lack of archaeological sites. From 5.5 kaBP to 4.0 kaBP, the climate changed from wet to dry, the natural environment was propitious to human survival. Dawenkou Culture and Longshan Culture flourished in this period. The Neolithic cultural development, the number of the sites and their distribution characteristics of the sites in the study area differed apparently from those in Central China and Shandong Province.展开更多
The CC1 core, with a length of 216 cm, was drilled in the west part of the Chen Co (Lake) in southern Tibet Plateau. The210Pb and137Cs measurement indicated that it was a consecutive sedimentary sequence since ca. 140...The CC1 core, with a length of 216 cm, was drilled in the west part of the Chen Co (Lake) in southern Tibet Plateau. The210Pb and137Cs measurement indicated that it was a consecutive sedimentary sequence since ca. 1400 years. The ostracoda and their assemblages under the level of 1 cm samples’ cutting interval were finished for this core to reveal the past environmental changes in the lake area. A total of 15 species of ostracods belonging to 7 genera in the core sediments had been identified. According to the ostracod distributions, abundances and preservations in the core, seven ostracod assemblages had been distinguished. The ostracod assemblages and their ecological features, together with the sediments dating decision were used to infer the past ca. 1400 years environmental changes of the Chen Co environmental evolutions in three stages, which had responded to the Medieval Ages Warm-period (MAW), the Little Ice Age (LIA) and modern warm period. The results show that the changes of the Chen Co environment had been mainly influenced by the climatic variations. The trend of the lake level fluctuations had been accorded with that of climatic variation during the past 1400 years.展开更多
A 332-cm long lacustrine core was drilled in the Nam Co in the central-southern part of the Tibetan Plateau. From the core, 15 species of ostracods （Crustacea： Ostracoda）, which belong to 6 genera have been identif...A 332-cm long lacustrine core was drilled in the Nam Co in the central-southern part of the Tibetan Plateau. From the core, 15 species of ostracods （Crustacea： Ostracoda）, which belong to 6 genera have been identified. According to the variations of the ostracod assemblages and the ostracods ecological features, which are sensitive to the changing environment, three main stages can be distinguished as follows： Stage Ⅰ was from 8400 to 6800 a BP, during which the climate was cold-humid, and the lake depth changed from shallow to deep. Stage Ⅱ was from 6400 to 2500 a BP, during which the climate changed from warm-humid to cold-humid, and then to cold-dry. The lake depth gradually became deep. The shifting of climate, from wet-cold to dry-cold during this period, had constructed the basis of present environment in the Nam Co. Stage Ⅲ was from 2500 a BP to the present, which showed a trait of lake depth increasing. At the earlier period of this stage, the climate kept as cold-dry as that in the former stage, but the salinity of the lake increased. At the later period of this stage, the degree of cold-dry was enhanced, and the activities of land surface runoff tended to be weakened. Our research also found that the peak values of ostracods with black shell was coherent with the maximum production of the ostracods, and agreed with the increasing sedimentary water dynamics. This indicated that the ostracods with black shell was simulta- neous with the high prolificacy of ostracod, and transported from other places. The abun- dance of Candonajuvenile shells reflected the high mortality of that kind of ostracods under an unfavorable condition. This was probably a result of the rapid change of water dynamics of sedimentary environment.展开更多
Based on analysis of parameters of cores taken from Gaoyou Lake, including magnetic susceptibility, grain-size characteristics and sedimentary rate, environmental changes during the modern period were examined with th...Based on analysis of parameters of cores taken from Gaoyou Lake, including magnetic susceptibility, grain-size characteristics and sedimentary rate, environmental changes during the modern period were examined with the assistance of historical records and Gaoyou Lake water level materials. It is concluded that during the modern period a higher value of magnetic susceptibility and a lower sediment grain size coincided with a wet climate, while a lower value of magnetic susceptibility and a higher grain size were related with a dry climate. The results indicate that the climate in the 123 years period from 1880 to 2003AD can be divided into four stages： two low water level stages （1880-1915AD, 1948-1981AD） and two high water level stages （1915-1948AD, 1981-2003AD）. It appears that the regional climate generally underwent a dry-wet-dry-wet pattern in 30-year cycles. At present, it is at the end of a wet period, so the regional climate is expected to become dry in the near future. This conclusion corresponds with the climate records in the historical literature of the Gaoyou area, and it also matches with the climatic changes in North Jiangsu area.展开更多
The taiga coniferous forests of the Siberian region are the main carbon sinks in the forest ecosystems.Quantitatively, the size of the carbon accumulation is determined by the photosynthetic productivity, which is str...The taiga coniferous forests of the Siberian region are the main carbon sinks in the forest ecosystems.Quantitatively, the size of the carbon accumulation is determined by the photosynthetic productivity, which is strongly influenced by environmental factors. As a result,an assessment of the relationship between environmental factors and photosynthetic productivity makes it possible to calculate and even predict carbon sinks in coniferous forests at the regional level. However, at various stages of the vegetative period, the force of the connection between environmental conditions and the productivity of photosynthesis may change. In this research, correlations between the photosynthetic activity of Scots pine(Pinus sylvestris L.) with the environmental conditions were compared in spring and in autumn. In spring, close positive correlation of the maximum daily net photosynthesis was identified with only one environmental factor. For different years, correlations were for soil temperature(rs= 0.655,p = 0.00315) or available soil water supply(rs= 0.892,p = 0.0068). In autumn within different years, significant correlation was shown with two(temperature of air and soil; rs= 0.789 and 0.896, p = 0.00045 and 0.000006,respectively) and four factors: temperature of air(rs=0.749, p = 0.00129) and soil(rs= 0.84, p = 0.00000),available soil water supply(rs= 0.846, p = 0.00013) and irradiance(rs= 0.826, p = 0.000001). Photosynthetic activity has a weaker connection with changes in environmental factors in the spring, as compared to autumn.This is explained by the multidirectional influence of environmental conditions on photosynthesis in this period and by the necessity of earlier photosynthesis onset, despite the unfavorable conditions. This data may be useful for predicting the flow of carbon in dependence on environmental factors in this region in spring and in autumn.展开更多
Based on the samples collected from the west wall of the ABYT2004 at Yuhuicun Site in Bengbu, Anhui Province, the multi-environmental substitute indexes such as the grain-size, Rb/Sr, zircon crystal morphology and mag...Based on the samples collected from the west wall of the ABYT2004 at Yuhuicun Site in Bengbu, Anhui Province, the multi-environmental substitute indexes such as the grain-size, Rb/Sr, zircon crystal morphology and magnetic susceptibility were analyzed. The age of archaeological strata was determined by AMS^14C dating. According to the results, combined with the information of the ancient human activities and the cultural heritage data obtained from the Longshan cultural archaeological strata, it can be concluded that （1） Before 4500 aBP, the climate was humid and water level was high in the Huaihe River and its tributaries, the drainage basin and its surrounding areas were even flooded, so the site area was submerged and there were no human activities around the site. （2） About 4500 aBP, the climate began to become drier and water level of the Huaihe River and its tributaries began to decline, thus floodplain gradually appeared, Yuhuicun Site and Longshan Culture began to appear. （3） Around 4100 aBP, the climate was humid and rainfall was abundant, which resulted in frequent flood disasters in the whole Huaihe River Basin. （4） After 4100 aBP, the climate gradually transited to be cold and dry, agricultural production was constrained to reduce the food source, Yuhuicun Site was almost abandoned. （5） The environmental information in sedimentary strata and historical records based on ancient books agree with each other. In addition, Yuhuicun Site was related to Dayu Zhishui （Yu the Great in taming the floods） in ancient books.展开更多
文摘Earth is moving through a period of extreme uncertainty as global climates change,natural disasters become more frequent and severe,and governments grapple with the difficulty these issues pose for managing natural resources and people.Nowhere are these challenges more pressing than across the world's drylands,where a combination of hotter drier climates challenge food security,sustainable food production and often fuel unrest and political instability.It is against this backdrop that Fu and Stafford Smith,two global leaders in dryland science draw on>80 years of collective wisdom on drylands to describe how humans and natural processes intersect in an era of global change(Fu and Stafford Smith,2024).
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.
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.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）.
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Supported by the National Natural Science Foundation of China(No.41430965)the Open Fund of the Key Laboratory of Marine Geology and Environment,Chinese Academy of Sciences(No.MGE2015KG08)
文摘The East China Sea continental shelf is a unique area for the study of land-sea interactions and paleoenvironmental change because it receives a large amount of terrestrial material inputs. In recent decades, human activities and global climate change have greatly aff ected river discharges into the sea. However, changes in the deposition process caused by these factors in the East China Sea continental shelf are unclear. We collected eight short sediment cores from the East China Sea inner shelf(ECSIS) using a box core sampler in 2012 and 2015. The grainsize, 2 10 Pb, and 1 37 Cs of these cores were analyzed in order to reconstruct the deposition history since the 1950 s, and to reveal human activity and climate change influences on sediment deposition in the ECSIS. Results indicated that sediment grain size became finer after 1969, turned coarser after 1987, and then further coarser since 2003, corresponding well to the three steps of sediment load drop in the Changjiang(Yangtze) River, which are mainly caused by human activities(particularly the closure of the Three Gorges Dam). Simultaneously, the East Asian Monsoon influenced the deposition process in the ECSIS by changing the intensity of coastal currents. Mean grain size variations in the fine-grained population(divided by grain size vs. standard deviation method) coincided with that of the East Asian Winter Monsoon strength and reflected its weakness in 1987. Abrupt changes in sediment grain size over a short time scale in these sediment cores were generally caused by floods and typhoons. Spectral analyses of the sediment cores showed periodicities of 10–11 and 20–22 years, corresponding to the periodicity of solar activity(Schwabe cycle and Hale cycle). Mean grain size time series also displayed a 3–8 year periodicity corresponding to El Ni?o Southern Oscillation periodic change.
基金National Natural Science Foundation of China, No.40271103 Subject Construction of Physical Geography during ＂985＂ and Testing Fund of Nanjing University
文摘Neolithic culture series in the Yishu River Basin developed in the order of Beixin culture-Dawenkou culture-Longshan culture-Yueshi culture. During the early and middle stage of Longshan culture （4600-4300 cal. yr BP）, the climate in the Yishu River Basin was warm and wet. Paddy-oriented agriculture planted paddy was very developed. The society was flourishing with great amount of archaeological sites. The cooling starting in 4200 cal. yr BP made the paddies shortfall in output or even no seeds were gathered. This situation intensified the discrepancy between population and resource. The scarcity in natural resource led to substantial decrease in population and subsequent drop in archaeological sites. About 4000 cal. yr BP Longshan culture was displaced by Yueshi culture which was relatively un- derdeveloped, simple and unsophisticated.
基金National Science and Technology Support Program, No.2006BAK21B02 National Basic Research Program of China, No.2003CB415201 National Natural Science Foundation of China, No.40671016
文摘At about 173 ka BP of the late period of mid-Pleistocene, the second terrace of the river had been formed as a result of uplift happening in Shangshan area because of the climate, sea level change and tectonic action. Between 173-75 ka BP, aeolian deposited on the terrace, a layer of reticulate red clayey soil about 80-100 cm thick deposited and developed under the warmer and higher temperature. In the last glacial period, the drop of the temperature and the decrease of the precipitation induced the dust-storms increased, A layer of Xiashu loess about 1.0-1.5 m thick accumulated on Shangshan terrace in the last glacial, which has the reticulate red clayey soil buried. At the beginning of the Holocene （11500 a BP-）, temperature went higher gradually and precipitation got more, the pre-persons moved on the Shangshan terrace （11,400-8600 a BP）, which is one of the most important archaeological sites, and can connect the paleolithic culture with Neolithic culture. It could be assumed from the results that the lower reaches of the Yangtze River are the home of rice cultivation, too. The lower place to the west of the Shangshan site experienced the two cycles process of the fluvial facies and the lacustrine facies, indicating that the water source of the pre-historical Shangshan is the river water or lake water. Two AMS 14C age proved the water source disappeared more than 1000 years ago.
基金Supported by the National Natural Science Foundation of China(No.41030856)the Taishan Scholar Project
文摘Previous studies carried out in the East China Sea （ECS） mud area focused on long-term environmental changes in sedimentary records during the Holoeene, especially during the mid-Holocene high-stand water levels period. These results indicate that sensitive grain size groups can be used as a sedimentary proxy to reconstruct the evolution of the East Asian Winter Monsoon （EAWM）. The studies have been carried out mainly in the northern and middle portions of the Zhejiang-Fujian coastal mud, however, similar research in the southern portion and the comparison between sedimentary proxy and modern measured data of EAWM are lacking. In this paper, we focused on a sedimentary record of the past 100 years with an enhanced resolution of 1.8 years. Investigations of the southern end of the Zhejiang-Fujian coastal mud area were conducted on the basis of 21~Pb chronology, grain-size analysis and chemical element analysis. The correspondence between the mean grain size （Mz） of sediment sensitive grain size and the measured EAWM was confirmed for the first time. We found that during the recent 100 years, the variation of the mean grain size of the sensitive population in the southern portion of the Zhejiang-Fujian mud was mainly controlled by the EAWM intensity changes; and not directly related to changes in the sediment discharge from Datong station of the Changjiang River （DTSD）. Finally, recent changes in the content of heavy metals in study area reflect the impact of human activities on the environment.
基金National Natural Science Foundation of China, No.40271103 Natural Science Foundation of Anhui Provincial Education Department, No.2005KJ202/021
文摘The Huaihe River basin of Anhui is not only a transitional zone of physical geography, but also a convergent area of many cultures in China. It is one of the sensitive ecotones to global changes and the birthplace of Chinese civilization. Using the field archaeological data and the sporo-pollens and the age data of the drilling cores, we analysed Neolithic cultural development and environmental evolution in the Huaihe River basin of Anhui. According to the combination of some research results in archaeology with environmental evolution research, this paper discusses the relationship between culture and environment in the Huaihe River basin of Anhui. The Neolithic cultural development was strongly impacted by the environmental change. The primitive culture （Shishanzi） was developed in the beginning of the Holocene Megathermal Period with distinct regional feature of the culture. From 6.5 kaBP to 5.5 kaBP, the climate changed warmer and wetter. The frequent occurrence of flood and waterlog due to such a climate regime and high sea level caused the earth＇s surface environment deteriorated in the Huaihe River basin of Anhui and the interruption of the Neolithic cultural development, hence a lack of archaeological sites. From 5.5 kaBP to 4.0 kaBP, the climate changed from wet to dry, the natural environment was propitious to human survival. Dawenkou Culture and Longshan Culture flourished in this period. The Neolithic cultural development, the number of the sites and their distribution characteristics of the sites in the study area differed apparently from those in Central China and Shandong Province.
基金National Natural Science Foundation of China, No.G1998040800Chinese Academy of Sciences+1 种基金No.KZCX2-314-2Knowledge Innovation Project of IGSNRR, CAS, No.CXIOG-A1-02
文摘The CC1 core, with a length of 216 cm, was drilled in the west part of the Chen Co (Lake) in southern Tibet Plateau. The210Pb and137Cs measurement indicated that it was a consecutive sedimentary sequence since ca. 1400 years. The ostracoda and their assemblages under the level of 1 cm samples’ cutting interval were finished for this core to reveal the past environmental changes in the lake area. A total of 15 species of ostracods belonging to 7 genera in the core sediments had been identified. According to the ostracod distributions, abundances and preservations in the core, seven ostracod assemblages had been distinguished. The ostracod assemblages and their ecological features, together with the sediments dating decision were used to infer the past ca. 1400 years environmental changes of the Chen Co environmental evolutions in three stages, which had responded to the Medieval Ages Warm-period (MAW), the Little Ice Age (LIA) and modern warm period. The results show that the changes of the Chen Co environment had been mainly influenced by the climatic variations. The trend of the lake level fluctuations had been accorded with that of climatic variation during the past 1400 years.
基金National Basic Research Program of China, No.2005CB422002National Natural Science Foundation of China, No.40571172The sixth framework project BRAHMATWINN, No.FP6-036952
文摘A 332-cm long lacustrine core was drilled in the Nam Co in the central-southern part of the Tibetan Plateau. From the core, 15 species of ostracods （Crustacea： Ostracoda）, which belong to 6 genera have been identified. According to the variations of the ostracod assemblages and the ostracods ecological features, which are sensitive to the changing environment, three main stages can be distinguished as follows： Stage Ⅰ was from 8400 to 6800 a BP, during which the climate was cold-humid, and the lake depth changed from shallow to deep. Stage Ⅱ was from 6400 to 2500 a BP, during which the climate changed from warm-humid to cold-humid, and then to cold-dry. The lake depth gradually became deep. The shifting of climate, from wet-cold to dry-cold during this period, had constructed the basis of present environment in the Nam Co. Stage Ⅲ was from 2500 a BP to the present, which showed a trait of lake depth increasing. At the earlier period of this stage, the climate kept as cold-dry as that in the former stage, but the salinity of the lake increased. At the later period of this stage, the degree of cold-dry was enhanced, and the activities of land surface runoff tended to be weakened. Our research also found that the peak values of ostracods with black shell was coherent with the maximum production of the ostracods, and agreed with the increasing sedimentary water dynamics. This indicated that the ostracods with black shell was simulta- neous with the high prolificacy of ostracod, and transported from other places. The abun- dance of Candonajuvenile shells reflected the high mortality of that kind of ostracods under an unfavorable condition. This was probably a result of the rapid change of water dynamics of sedimentary environment.
基金Foundation： National Natural Science Foundation of China, No.40271004Acknowledgements： We wish to thank Professor Wang Ying for her supervision during fieldwork and paper writing, Professor Bruce Mitchell, Associate Provost of University of Waterloo, for reviewing the paper, Shi Xiaodong and Luo Weiwei for making ^210pb dating measurements, and Ding Haiyan for participating in grain size and magnetic susceptibility measurements.
文摘Based on analysis of parameters of cores taken from Gaoyou Lake, including magnetic susceptibility, grain-size characteristics and sedimentary rate, environmental changes during the modern period were examined with the assistance of historical records and Gaoyou Lake water level materials. It is concluded that during the modern period a higher value of magnetic susceptibility and a lower sediment grain size coincided with a wet climate, while a lower value of magnetic susceptibility and a higher grain size were related with a dry climate. The results indicate that the climate in the 123 years period from 1880 to 2003AD can be divided into four stages： two low water level stages （1880-1915AD, 1948-1981AD） and two high water level stages （1915-1948AD, 1981-2003AD）. It appears that the regional climate generally underwent a dry-wet-dry-wet pattern in 30-year cycles. At present, it is at the end of a wet period, so the regional climate is expected to become dry in the near future. This conclusion corresponds with the climate records in the historical literature of the Gaoyou area, and it also matches with the climatic changes in North Jiangsu area.
基金funded by The Program of Basic Research of the Presidium of the Russian Academy of Sciences No.23 ‘‘Biodiversity’’(Project 23.31:Relationship between the use of environmental resources and photosynthesis of conifers as a factor in the sustainability and biological diversity of forest ecosystems in Northern Eurasia)
文摘The taiga coniferous forests of the Siberian region are the main carbon sinks in the forest ecosystems.Quantitatively, the size of the carbon accumulation is determined by the photosynthetic productivity, which is strongly influenced by environmental factors. As a result,an assessment of the relationship between environmental factors and photosynthetic productivity makes it possible to calculate and even predict carbon sinks in coniferous forests at the regional level. However, at various stages of the vegetative period, the force of the connection between environmental conditions and the productivity of photosynthesis may change. In this research, correlations between the photosynthetic activity of Scots pine(Pinus sylvestris L.) with the environmental conditions were compared in spring and in autumn. In spring, close positive correlation of the maximum daily net photosynthesis was identified with only one environmental factor. For different years, correlations were for soil temperature(rs= 0.655,p = 0.00315) or available soil water supply(rs= 0.892,p = 0.0068). In autumn within different years, significant correlation was shown with two(temperature of air and soil; rs= 0.789 and 0.896, p = 0.00045 and 0.000006,respectively) and four factors: temperature of air(rs=0.749, p = 0.00129) and soil(rs= 0.84, p = 0.00000),available soil water supply(rs= 0.846, p = 0.00013) and irradiance(rs= 0.826, p = 0.000001). Photosynthetic activity has a weaker connection with changes in environmental factors in the spring, as compared to autumn.This is explained by the multidirectional influence of environmental conditions on photosynthesis in this period and by the necessity of earlier photosynthesis onset, despite the unfavorable conditions. This data may be useful for predicting the flow of carbon in dependence on environmental factors in this region in spring and in autumn.
基金National Natural Science Foundation of China, No.40971115 No.40701190+1 种基金 National Key Technology R＆D Program, No.2006BAK21B02 The Key Subject Foundation of Human Geography in West Anhui University The authors thank Prof. Zhou Kunshu of Institute of Geology and Geophysics, Chinese Academy of Sciences, Prof. Wang Fubao of Nanjing University, and Prof. Huang Run of West Anhui University for their constructive advices to the paper.
文摘Based on the samples collected from the west wall of the ABYT2004 at Yuhuicun Site in Bengbu, Anhui Province, the multi-environmental substitute indexes such as the grain-size, Rb/Sr, zircon crystal morphology and magnetic susceptibility were analyzed. The age of archaeological strata was determined by AMS^14C dating. According to the results, combined with the information of the ancient human activities and the cultural heritage data obtained from the Longshan cultural archaeological strata, it can be concluded that （1） Before 4500 aBP, the climate was humid and water level was high in the Huaihe River and its tributaries, the drainage basin and its surrounding areas were even flooded, so the site area was submerged and there were no human activities around the site. （2） About 4500 aBP, the climate began to become drier and water level of the Huaihe River and its tributaries began to decline, thus floodplain gradually appeared, Yuhuicun Site and Longshan Culture began to appear. （3） Around 4100 aBP, the climate was humid and rainfall was abundant, which resulted in frequent flood disasters in the whole Huaihe River Basin. （4） After 4100 aBP, the climate gradually transited to be cold and dry, agricultural production was constrained to reduce the food source, Yuhuicun Site was almost abandoned. （5） The environmental information in sedimentary strata and historical records based on ancient books agree with each other. In addition, Yuhuicun Site was related to Dayu Zhishui （Yu the Great in taming the floods） in ancient books.
