The plateau environment not only affects the development of concrete's early strength but also damages its durability during its service life.This paper summarized and analyzed the impact of plateau environments o...The plateau environment not only affects the development of concrete's early strength but also damages its durability during its service life.This paper summarized and analyzed the impact of plateau environments on concrete’properties and proposed methods to improve the performance of concrete in plateau environment.The results indicated that low humidity and high evaporation rates in plateau regions inhibit the hydration of cement in concrete,leading to an increased content of micro-pores ranging from 500 to 1000 nm and raising the risk of early-stage cracking,thus reducing the impermeability of concrete.The low atmospheric pressure(AP)condition of 60 kPa decreases the entrained air content in concrete by over 20%,diminishes the pores under 200μm,and increases the average air-voids diameter and spacing factor,resulting in a decrease of more than 5%in the 28 d compressive strength of concrete.Consequently,the durability of concrete is compromised.Saponin and rosinbased air-entraining agents are recommended to improve the performance of concrete in plateau environments.Nanoparticles also aid in stabilizing bubbles in such conditions.Selecting low-heat specialty cements,increasing the amount of cement used,and extending the curing period are also vital measures to enhance the performance of plateau concrete.展开更多
A three-dimensional diesel particulate filter(DPF)simulation model was developed by using AVL software FIRE to study the effects of four factors on soot particle distributions along the axial and radial directions in ...A three-dimensional diesel particulate filter(DPF)simulation model was developed by using AVL software FIRE to study the effects of four factors on soot particle distributions along the axial and radial directions in the DPF after the model accuracy was validated.An orthogonal test method was used to determine the importance and weights of the design of experiments(DoE)factors such as the expanding angle,the number of channels per square inch,and the exhaust mass flow rate.The effects of these factors on the uniformity of the soot particle distributions were also analyzed.The results show that when the soot loading time was 400 s,the soot particles inside the DPF along the axial direction exhibited a bowl shape,which was high on the both ends and low in the middle.The uniformity of the axial distribution of soot particles reduces significantly with an increase in the number of channels per square inch.The uniformity of the radial distribution reduced with an increase in the expanding angle of the divergent tube.Based on the impacts on the axial uniformity,the three most influencing factors in a descending order are the number of channels per square inch,the exhaust mass flow rate,and the expanding angle of the divergent tube.展开更多
The impact of interbasin water transfer on environment is very significant. The affected area of the west route scheme of the South to North Water Transfer Project in China (SNWT) is located in the eastern Tibetan Pla...The impact of interbasin water transfer on environment is very significant. The affected area of the west route scheme of the South to North Water Transfer Project in China (SNWT) is located in the eastern Tibetan Plateau, where the altitude is high with frigid eco-environment. In this article, remote sensing and GIS are applied to analyze the natural environment and the natural environment index is established to express the natural conditions of the study area. After the natural environment index is divided into four grades and the features of each grade are analysed, some results are obtained for reference in environmental assessment of the west route of SNWT.展开更多
We designed two types of pre-adaption plans for this study. One was a pre-adaption training with progressive intermittent hypoxia, with a constant lower pressure oxygen tank used in the plain before arriving at the pl...We designed two types of pre-adaption plans for this study. One was a pre-adaption training with progressive intermittent hypoxia, with a constant lower pressure oxygen tank used in the plain before arriving at the plateau （PG）. The other was by progressively increasing the time of exposure to hypoxia with oxygen supplied in stages after radical plateau （RG）. By testing the blood oxygen saturation （SpO2）, heart rate （HR）, and quality of sleep after arriving at the 3800 m high plateau, results showed that the pre-acclimatization and radical groups performed better than the control group （CG）. Both strategies were equivalent in terms of effects and principles in providing more flexible choices for acclimatization.展开更多
Based on the investigation and analysis of characteristics of precipitation, natural environment, socio-economic factors and soil erosion, this paper indicates that the precipitation is the main driving force for the ...Based on the investigation and analysis of characteristics of precipitation, natural environment, socio-economic factors and soil erosion, this paper indicates that the precipitation is the main driving force for the soil erosion in the sediment-rich area, its variability determines the characteristics of soil and water loss; the natural conditions such as the drainage systems, geological and topographic features, the composition of soil and land surface materials, vegetation and climate determine the seriousness of soil and water loss; irrational socio-economic activities of human beings usually accelerated soil and water loss; meanwhile, the low preservation rate and inferiority of soil and water conservation measures made it impossible to make rapid progress on soil and water loss control. Furthermore, the characteristics of erosion environment endowed this area with more sediment that is the main reason for the flooding disasters by the Yellow River. Therefore, more emphasis should be placed on the enhancement of soil and water conservation. The soil loss prediction models will provide scientific basis for the planning of soil and water conservation, the designing of soil and water conservation measures and the valuation of effects of soil and water loss control. According to the analysis of the previous studies on soil loss prediction, and the water-sediment variation features, it is thought that study on soil loss prediction under various rainfall conditions and soil-water conservation measures should be carried out.展开更多
The Qinghai Xizang (Tibet) Plateau area was subjected to twice uplift and planation in the Tertiary. Intense uplifting of the plateau area has given rise to drastic changes and differentiation of physical environment ...The Qinghai Xizang (Tibet) Plateau area was subjected to twice uplift and planation in the Tertiary. Intense uplifting of the plateau area has given rise to drastic changes and differentiation of physical environment on the plateau and the surrounding area since 3.4 Ma B.P. Significant environmental changes with dry tendency in interior of the plateau had occurred during the last 150 ka B.P. By comparative study on several mountains of the plateau, two systems of the structure type of the altitudinal belt are identified and nine groups are subdivided . A distribution model with close relevance to highland uplift effect has been generalized. A number of striking geo ecological phenomena and their spatial pattern such as moisture corridor, dry valleys, high cold meadow zone, and high cold arid core area are investigated and discussed. Based on the thermal conditions, moisture regimes and variation in landforms of the plateau is sequentially demarcated. A tentative scheme of 2 temperature belts, 10 natural zones and 28 physical districts has been proposed not including southern slopes of the East Himalayas. The Qinghai Xizang Plateau is sensitive to “green house effect”, showing close relation with global change. Characteristics of temperature and precipitation on the plateau during the last 2000 years, and response of glaciers, snow deposit and permafrost on the plateau to global change are dealt with in the present paper.展开更多
1. The environmental quality of the Loess Plateau and Liupanshan mountainous area in Ningxia The landuse structure in the studied region was very irrational in 1970s, the propor-tions covered by farming, forestry and ...1. The environmental quality of the Loess Plateau and Liupanshan mountainous area in Ningxia The landuse structure in the studied region was very irrational in 1970s, the propor-tions covered by farming, forestry and animal husbandry are separately 50.91%, 6.32% and33.3%. Since 1980s, the farmland has been returned back to forestry and pasture so that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
The community assembly rules and species coexistence have always been interested by ecologists. The community phylogenetic structure is the consequence of the interaction process between the organisms and the abiotic ...The community assembly rules and species coexistence have always been interested by ecologists. The community phylogenetic structure is the consequence of the interaction process between the organisms and the abiotic environment and has been used to explain the relative impact of abiotic and biotic factors on species co-existence. In recent years, grassland degradation and biodiversity loss have become increasingly severe on the Mongolian Plateau, while the drivers for these changes are not clearly explored, especially whether climate change is a main factor is debated in academia. In this study, we examined the phylogenetic structure of grassland communities along five transects of climate aridity on the Mongolian Plateau, and analyzed their relations with environmental factors, with the aims to understand the formation mechanism of the grassland communities and the role of climatic factors. We surveyed grassland communities at 81 sites along the five transects, and calculated their net relatedness index(NRI) at two different quadrat scales(small scale of 1 m2 and large scale of 5 m2) to characterize the community phylogenetic structure and analyze its relationship with the key 11 environmental factors. We also calculated the generalized UniFrac distance(GUniFrac) among the grassland communities to quantify the influence of spatial distance and environmental distance on the phylogenetic β diversity. The results indicated that plant community survey using the large scale quadrat contained sufficient species to represent community compositions. The community phylogenetic structure of grasslands was significantly overdispersed at both the small and large scales, and the degree of overdispersion was greater at the large scale than at the small scale, suggesting that competitive exclusion instead of habitat filtering played a major role in determination of community composition. Altitude was the main factor affecting the community phylogenetic structure, whereas climatic factors, such as precipitation and temperature, had limited influence. The principal component analysis of the 11 environmental factors revealed that 94.04% of their variation was accounted by the first four principal components. Moreover only 14.29% and 23.26% of the variation in community phylogenetic structure were explained by the first four principal components at the small and large scales, respectively. Phylogenetic β diversity was slightly significantly correlated with both spatial distance and environmental distance, however, environmental distance had a less explanatory power than spatial distance, indicating a limited environmental effect on the community phylogenetic structure of grasslands on the Mongolian Plateau. In view of the limited effect of climatic factors on the community phylogenetic structure of grasslands, climate change may have a smaller impact on grassland degradation than previously thought.展开更多
The Tibetan Plateau （TP） plays a unique role in Earth System Sciences. It represents a key area to understand not only basic geodynamic processes linked with the formation and uplift of mountains and plateaus, but a...The Tibetan Plateau （TP） plays a unique role in Earth System Sciences. It represents a key area to understand not only basic geodynamic processes linked with the formation and uplift of mountains and plateaus, but also the interaction between plateau uplift and environmental changes. Over the last 50 million years the formation of the TP has considerably influenced the global climate and monsoon system. Moreover, the TP proves to be extremely sensitive to present-day global change phenomena. Based upon the foundation of the new Institute of Tibetan Plateau Research （1TP） by the Chinese Academy of Sciences （CAS） and through the Memorandum signed by the CAS and DFG （Deutschen Forschungsgemeinschaft）, both CAS and DFG provide opportunities to intensify TP research and to develop coordinated research programs. ＂The Tibetan Plateau - Geodynamics and Environmental Evolution＂ consisting of one big projects funded by CAS and five projects funded by DFG that cover the pre- and early-collision history of the TP, the Palaeogene/Neogene uplift and climatic dynamics as well as the Late Quaternary and recent environmental and climatic changes on the TP. The projects are linked through several levels of interactions.展开更多
A series of faulted inland basins were developed in the central Qinghai-Tibet Plateau, among which the Co Ngoin Basin containing thick lacustrine sediments is located in the peripheral area of the Indian monsoon. In t...A series of faulted inland basins were developed in the central Qinghai-Tibet Plateau, among which the Co Ngoin Basin containing thick lacustrine sediments is located in the peripheral area of the Indian monsoon. In this paper, we present the weathering history and paleoclimatic changes in the last 2.8 Ma based on studies of high-resolution temporal distributions of Sr, Rb and Zr concentrations, Rb/Sr and Zr/Rb ratios and δ 13C and TOC for the Co Ngoin sediments, in combination with the sediment properties, grain size distribution and clay mineralogy. The sedimentary records indicate three environmental stages in the last 2.8 Ma. At the core depth of 197?170 m (about 2.8?2.5 Ma), low-intensity chemical weathering in the Co Ngoin catchment was experienced under warm-dry to cool-wet climate conditions with relatively low Sr concentration and high Rb/Sr and Zr/Rb ratios. The sudden occurrence of both subalpine coniferous forest and coarse sand and gravel sediments in the Co Ngoin core reflects a strong tectonic uplift. The high Sr concentrations and low Rb/Sr and Zr/Rb ratios reflect a relatively strong chemical weathering between 2.5 Ma and 0.8 Ma (at the core depth of 170?38.5 m) under a temperate/cool and wet climate, characterized by mud and silt with fine sand, probably indicating a stable process of denudation and planation of the plateau. Above the depth of 38.5 m (about 0.8?0 Ma), the coarsening of sediments indicates a strong tectonic uplift and a relatively low intensity of chemical weathering as supported by the record of sediments having relatively low Sr concentrations and high Rb/Sr and Zr/Rb ratios. Since then, the plateau has taken the shape of the modern topographic pattern above 4000 m a.s.l.展开更多
The gut microbiome shows changes under a plateau environment,while the disbalance of intestinal microbiota plays an important role in the pathogenesis of irritable bowel syndrome(IBS);however,the relationship between ...The gut microbiome shows changes under a plateau environment,while the disbalance of intestinal microbiota plays an important role in the pathogenesis of irritable bowel syndrome(IBS);however,the relationship between the two remains unexplored.In this work,we followed up a healthy cohort for up to a year before and after living in a plateau environment and performed 16S ribosomal RNA(rRNA)sequencing analysis of their fecal samples.Through evaluating the participants’clinical symptoms,combined with an IBS questionnaire,we screened the IBS sub-population in our cohort.The sequencing results showed that a high-altitude environment could lead to changes in the diversity and composition of gut flora.In addition,we found that the longer the time volunteers spent in the plateau environment,the more similar their gut microbiota composition and abundance became compared to those before entering the plateau,and IBS symptoms were significantly alleviated.Therefore,we speculated that the plateau may be a special environment that induces IBS.The taxonomic units g_Alistipes,g_Oscillospira,and s_Ruminococcus_torques,which had been proved to play important roles in IBS pathogenesis,were also abundant in the IBS cohort at high altitudes.Overall,the disbalance of gut microbiota induced by the plateau environment contributed to the high frequency of IBS and the psychosocial abnormalities associated with IBS.Our results prompt further research to elucidate the relevant mechanism.展开更多
The Zoige Wetland is located in the northeastern Qinghai-Tibetan Plateau, which is highly sensitive to global environment change and human disturbance because of its high elevation and cold environment, thus, it＇s a ...The Zoige Wetland is located in the northeastern Qinghai-Tibetan Plateau, which is highly sensitive to global environment change and human disturbance because of its high elevation and cold environment, thus, it＇s a hotspot for land use and land cover change （LUCC） research. We used Landsat MSS images from 1975, Landsat ETM images from 2000, and Landsat TM images fi：om 1990 and 2005 to assess the LUCC in the study area, using GIS techniques, as well as topographic, vegetation, and soil maps combined with field investigations. The monitoring result shows that the study area＇s environment degraded rapidly between 1975 and 2005, including wetland shrinkage from 5,308 km2 to 4,980 lan2, sandy land expansion from 112 krn2 to 137 krn2, forest land decreasing from 5,686 km2 to 5,443 km2, and grassland degradation from 12,309 km2 to 10,672 km2. According to the analysis of meteorological data and social-economic statistical data, we concluded that the LUCC in the Zoige Wetland was caused by both natural and anthropogenic factors, but human activities were primarily responsible for the observed LUCC, thereby, we suggest human behaviors must be adjusted to control environmental degradation.展开更多
The fluctuation of lake levels in Tibetan area may be well reflected by the landformevidences, especially the last highest lake levels. This, in a certain degree, is more suitable fordetermning the climatic humidity a...The fluctuation of lake levels in Tibetan area may be well reflected by the landformevidences, especially the last highest lake levels. This, in a certain degree, is more suitable fordetermning the climatic humidity and aridity in macro scale compared with many other indicatorswhich are also sensitive to the sedimentary environmental change. According to the analyses of thelakes such as Tianshuihai Lake, Bangdag Co, Lungmu Co, Bangong Co, Serfing Co, Chabyer Caka,Qahan salt lake, Qinghai lake, the lake group in north-east Qiangtang and the lake group in southTibet. the authors thought that the lakes on the Tibetan Plateau generally appeared the high lakelevel during 40-25 ka BP. The plenty of water quantity may represent a special warm-humid stage inTibet area compared with the sub-warm-humid stage reflected by marine oxygen isotope records.Thus, there may existed different driving factors to climatic changes between the high latitUde areasand middle-low latitude mountains.展开更多
Soil nitrogen(N) is critical to ecosystem services and environmental quality. Hotspots of soil N in areas with high soil moisture have been widely studied, however, their spatial distribution and their linkage with so...Soil nitrogen(N) is critical to ecosystem services and environmental quality. Hotspots of soil N in areas with high soil moisture have been widely studied, however, their spatial distribution and their linkage with soil N variation have seldom been examined at a catchment scale in areas with low soil water content. We investigated the spatial variation of soil N and its hotspots in a mixed land cover catchment on the Chinese Loess Plateau and used multiple statistical methods to evaluate the effects of the critical environmental factors on soil N variation and potential hotspots. The results demonstrated that land cover, soil moisture, elevation, plan curvature and flow accumulation were the dominant factors affecting the spatial variation of soil nitrate(NN), while land cover and slope aspect were the most important factors impacting the spatial distribution of soil ammonium(AN) and total nitrogen(TN). In the studied catchment, the forestland, gully land and grassland were found to be the potential hotspots of soil NN, AN and TN accumulation, respectively. We concluded that land cover and slope aspect could be proxies to determine the potential hotspots of soil N at the catchment scale. Overall, land cover was the most important factor that resulted in the spatial variations of soil N. The findings may help us to better understand the environmental factors affecting soil N hotspots and their spatial variation at the catchment scale in terrestrial ecosystems.展开更多
More and more concentrations have been focused on the uplift of the Tibetan Plateau and its effects on regional and global environment. The development of Asian monsoon has a close relationship with the uplift of the ...More and more concentrations have been focused on the uplift of the Tibetan Plateau and its effects on regional and global environment. The development of Asian monsoon has a close relationship with the uplift of the Tibetan Plateau. The understanding for the development of Asian monsoon is the key to the understanding of the process and the mechanism of the environmental evolution of the Asian region and to the understanding of the history of the uplift of the Tibetan Plateau. It is found that a big change of the Asian monsoon system occurred at about 2 6Ma ago. The winter monsoon strengthened (Ding et al.,1992 ), the change of winter monsoon began to in the opposite phase to the summer monsoon in East Asia (An et al., 1998 ), the tropical Southwest monsoon was hard to influence the North China (Li, 1999). However, whether there were changes in direction of winter monsoon and strength of summer monsoon occurred and how to change are still not clear. In this paper, the changes of the Asian monsoon system at about 2 6Ma ago are discussed, based on the reanalysis and combination of the results of atmospheric simulations and the geological records existed. It is suggested that, at about 2 6Ma ago, both winter monsoon and summer monsoon strengthened obviously, because that the amplitude of the climatic change increased a lot—warmer during the warm periods and colder during the cold periods. The direction of winter monsoon in Northern China changed from North—West—West to Northwest or North—West—North, because that the expansion direction of eolian\|deposit\|distribution area in China changed from mainly eastward to mainly southward. The area influenced by subtropical monsoon increased, but the area influenced by tropical monsoon decreased in China, because of the rising of the Tibetan Plateau and the southwest\|ward migration of the center of the Asian Low. At some time of the Pliocene, the tropical monsoon had penetrated onto the Qinghai\|Xizang region and influenced on the North China and Northwest China. However, after 2.6Ma B.P., the effects of the tropical monsoon on Northwest China and the northern part of the Tibetan Plateau decreased. All these suggest that the Tibetan Plateau perhaps reached about 2000m elevation at about 2 6Ma B.P..展开更多
基金funded by the National Natural Science Foundation of China(No.52278429)the Key R&D Program in Shaanxi Province(Nos.2023-ZDLGY-25,2025SF-YBXM-537)+1 种基金the Fundamental Research Funds for the Central Universities,CHD(No.300102315203)Transportation Science and Technology Project in Shaanxi Province(Nos.23-91K,24-14K,24-39K).
文摘The plateau environment not only affects the development of concrete's early strength but also damages its durability during its service life.This paper summarized and analyzed the impact of plateau environments on concrete’properties and proposed methods to improve the performance of concrete in plateau environment.The results indicated that low humidity and high evaporation rates in plateau regions inhibit the hydration of cement in concrete,leading to an increased content of micro-pores ranging from 500 to 1000 nm and raising the risk of early-stage cracking,thus reducing the impermeability of concrete.The low atmospheric pressure(AP)condition of 60 kPa decreases the entrained air content in concrete by over 20%,diminishes the pores under 200μm,and increases the average air-voids diameter and spacing factor,resulting in a decrease of more than 5%in the 28 d compressive strength of concrete.Consequently,the durability of concrete is compromised.Saponin and rosinbased air-entraining agents are recommended to improve the performance of concrete in plateau environments.Nanoparticles also aid in stabilizing bubbles in such conditions.Selecting low-heat specialty cements,increasing the amount of cement used,and extending the curing period are also vital measures to enhance the performance of plateau concrete.
基金Project(52066008)supported by the National Natural Science Foundation,ChinaProject(2018FA030)supported by Yunnan Province Fundamental Research Key Project Foundation,China+1 种基金Project(2018ZE001)supported by Yunnan Province Major Science and Technology Project Foundation,ChinaProject(202005AG070057)supported by Yunnan Province Science and Technology Innovation Funds for key Laboratories,China。
文摘A three-dimensional diesel particulate filter(DPF)simulation model was developed by using AVL software FIRE to study the effects of four factors on soot particle distributions along the axial and radial directions in the DPF after the model accuracy was validated.An orthogonal test method was used to determine the importance and weights of the design of experiments(DoE)factors such as the expanding angle,the number of channels per square inch,and the exhaust mass flow rate.The effects of these factors on the uniformity of the soot particle distributions were also analyzed.The results show that when the soot loading time was 400 s,the soot particles inside the DPF along the axial direction exhibited a bowl shape,which was high on the both ends and low in the middle.The uniformity of the axial distribution of soot particles reduces significantly with an increase in the number of channels per square inch.The uniformity of the radial distribution reduced with an increase in the expanding angle of the divergent tube.Based on the impacts on the axial uniformity,the three most influencing factors in a descending order are the number of channels per square inch,the exhaust mass flow rate,and the expanding angle of the divergent tube.
基金National key research program of basic science, No.G1999043601
文摘The impact of interbasin water transfer on environment is very significant. The affected area of the west route scheme of the South to North Water Transfer Project in China (SNWT) is located in the eastern Tibetan Plateau, where the altitude is high with frigid eco-environment. In this article, remote sensing and GIS are applied to analyze the natural environment and the natural environment index is established to express the natural conditions of the study area. After the natural environment index is divided into four grades and the features of each grade are analysed, some results are obtained for reference in environmental assessment of the west route of SNWT.
基金supported in part by the national basic research program of China 973 program(NO.2012CB518200-G)Army major issue of comprehensive medical security research of flight crew in the plateau(N0.AKJ11J005)
文摘We designed two types of pre-adaption plans for this study. One was a pre-adaption training with progressive intermittent hypoxia, with a constant lower pressure oxygen tank used in the plain before arriving at the plateau （PG）. The other was by progressively increasing the time of exposure to hypoxia with oxygen supplied in stages after radical plateau （RG）. By testing the blood oxygen saturation （SpO2）, heart rate （HR）, and quality of sleep after arriving at the 3800 m high plateau, results showed that the pre-acclimatization and radical groups performed better than the control group （CG）. Both strategies were equivalent in terms of effects and principles in providing more flexible choices for acclimatization.
基金Knowledge Innovation Project of CAS, No. KZCX1-10-04
文摘Based on the investigation and analysis of characteristics of precipitation, natural environment, socio-economic factors and soil erosion, this paper indicates that the precipitation is the main driving force for the soil erosion in the sediment-rich area, its variability determines the characteristics of soil and water loss; the natural conditions such as the drainage systems, geological and topographic features, the composition of soil and land surface materials, vegetation and climate determine the seriousness of soil and water loss; irrational socio-economic activities of human beings usually accelerated soil and water loss; meanwhile, the low preservation rate and inferiority of soil and water conservation measures made it impossible to make rapid progress on soil and water loss control. Furthermore, the characteristics of erosion environment endowed this area with more sediment that is the main reason for the flooding disasters by the Yellow River. Therefore, more emphasis should be placed on the enhancement of soil and water conservation. The soil loss prediction models will provide scientific basis for the planning of soil and water conservation, the designing of soil and water conservation measures and the valuation of effects of soil and water loss control. According to the analysis of the previous studies on soil loss prediction, and the water-sediment variation features, it is thought that study on soil loss prediction under various rainfall conditions and soil-water conservation measures should be carried out.
文摘The Qinghai Xizang (Tibet) Plateau area was subjected to twice uplift and planation in the Tertiary. Intense uplifting of the plateau area has given rise to drastic changes and differentiation of physical environment on the plateau and the surrounding area since 3.4 Ma B.P. Significant environmental changes with dry tendency in interior of the plateau had occurred during the last 150 ka B.P. By comparative study on several mountains of the plateau, two systems of the structure type of the altitudinal belt are identified and nine groups are subdivided . A distribution model with close relevance to highland uplift effect has been generalized. A number of striking geo ecological phenomena and their spatial pattern such as moisture corridor, dry valleys, high cold meadow zone, and high cold arid core area are investigated and discussed. Based on the thermal conditions, moisture regimes and variation in landforms of the plateau is sequentially demarcated. A tentative scheme of 2 temperature belts, 10 natural zones and 28 physical districts has been proposed not including southern slopes of the East Himalayas. The Qinghai Xizang Plateau is sensitive to “green house effect”, showing close relation with global change. Characteristics of temperature and precipitation on the plateau during the last 2000 years, and response of glaciers, snow deposit and permafrost on the plateau to global change are dealt with in the present paper.
文摘1. The environmental quality of the Loess Plateau and Liupanshan mountainous area in Ningxia The landuse structure in the studied region was very irrational in 1970s, the propor-tions covered by farming, forestry and animal husbandry are separately 50.91%, 6.32% and33.3%. Since 1980s, the farmland has been returned back to forestry and pasture so that
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supported by the National Key Research and Development Program of China (2016YFC0500503)the Science and Technology Program of Inner Mongolia Autonomous Region of China (20140409, 201503001)
文摘The community assembly rules and species coexistence have always been interested by ecologists. The community phylogenetic structure is the consequence of the interaction process between the organisms and the abiotic environment and has been used to explain the relative impact of abiotic and biotic factors on species co-existence. In recent years, grassland degradation and biodiversity loss have become increasingly severe on the Mongolian Plateau, while the drivers for these changes are not clearly explored, especially whether climate change is a main factor is debated in academia. In this study, we examined the phylogenetic structure of grassland communities along five transects of climate aridity on the Mongolian Plateau, and analyzed their relations with environmental factors, with the aims to understand the formation mechanism of the grassland communities and the role of climatic factors. We surveyed grassland communities at 81 sites along the five transects, and calculated their net relatedness index(NRI) at two different quadrat scales(small scale of 1 m2 and large scale of 5 m2) to characterize the community phylogenetic structure and analyze its relationship with the key 11 environmental factors. We also calculated the generalized UniFrac distance(GUniFrac) among the grassland communities to quantify the influence of spatial distance and environmental distance on the phylogenetic β diversity. The results indicated that plant community survey using the large scale quadrat contained sufficient species to represent community compositions. The community phylogenetic structure of grasslands was significantly overdispersed at both the small and large scales, and the degree of overdispersion was greater at the large scale than at the small scale, suggesting that competitive exclusion instead of habitat filtering played a major role in determination of community composition. Altitude was the main factor affecting the community phylogenetic structure, whereas climatic factors, such as precipitation and temperature, had limited influence. The principal component analysis of the 11 environmental factors revealed that 94.04% of their variation was accounted by the first four principal components. Moreover only 14.29% and 23.26% of the variation in community phylogenetic structure were explained by the first four principal components at the small and large scales, respectively. Phylogenetic β diversity was slightly significantly correlated with both spatial distance and environmental distance, however, environmental distance had a less explanatory power than spatial distance, indicating a limited environmental effect on the community phylogenetic structure of grasslands on the Mongolian Plateau. In view of the limited effect of climatic factors on the community phylogenetic structure of grasslands, climate change may have a smaller impact on grassland degradation than previously thought.
文摘The Tibetan Plateau （TP） plays a unique role in Earth System Sciences. It represents a key area to understand not only basic geodynamic processes linked with the formation and uplift of mountains and plateaus, but also the interaction between plateau uplift and environmental changes. Over the last 50 million years the formation of the TP has considerably influenced the global climate and monsoon system. Moreover, the TP proves to be extremely sensitive to present-day global change phenomena. Based upon the foundation of the new Institute of Tibetan Plateau Research （1TP） by the Chinese Academy of Sciences （CAS） and through the Memorandum signed by the CAS and DFG （Deutschen Forschungsgemeinschaft）, both CAS and DFG provide opportunities to intensify TP research and to develop coordinated research programs. ＂The Tibetan Plateau - Geodynamics and Environmental Evolution＂ consisting of one big projects funded by CAS and five projects funded by DFG that cover the pre- and early-collision history of the TP, the Palaeogene/Neogene uplift and climatic dynamics as well as the Late Quaternary and recent environmental and climatic changes on the TP. The projects are linked through several levels of interactions.
基金supported by the National Natural Science Foundation of China(Grant No.40373004)the National Key Basic Research Science Foundation(Grant No.G199804O810)+1 种基金the UK Royal Society BP Research Fellowshipthe Doctors Foundation of Liaocheng University.
文摘A series of faulted inland basins were developed in the central Qinghai-Tibet Plateau, among which the Co Ngoin Basin containing thick lacustrine sediments is located in the peripheral area of the Indian monsoon. In this paper, we present the weathering history and paleoclimatic changes in the last 2.8 Ma based on studies of high-resolution temporal distributions of Sr, Rb and Zr concentrations, Rb/Sr and Zr/Rb ratios and δ 13C and TOC for the Co Ngoin sediments, in combination with the sediment properties, grain size distribution and clay mineralogy. The sedimentary records indicate three environmental stages in the last 2.8 Ma. At the core depth of 197?170 m (about 2.8?2.5 Ma), low-intensity chemical weathering in the Co Ngoin catchment was experienced under warm-dry to cool-wet climate conditions with relatively low Sr concentration and high Rb/Sr and Zr/Rb ratios. The sudden occurrence of both subalpine coniferous forest and coarse sand and gravel sediments in the Co Ngoin core reflects a strong tectonic uplift. The high Sr concentrations and low Rb/Sr and Zr/Rb ratios reflect a relatively strong chemical weathering between 2.5 Ma and 0.8 Ma (at the core depth of 170?38.5 m) under a temperate/cool and wet climate, characterized by mud and silt with fine sand, probably indicating a stable process of denudation and planation of the plateau. Above the depth of 38.5 m (about 0.8?0 Ma), the coarsening of sediments indicates a strong tectonic uplift and a relatively low intensity of chemical weathering as supported by the record of sediments having relatively low Sr concentrations and high Rb/Sr and Zr/Rb ratios. Since then, the plateau has taken the shape of the modern topographic pattern above 4000 m a.s.l.
基金supported by the Research and Innovation Team Topics of Characteristic Medical Center of Chinese People’s Armed Police Force(No.KYCXTD0503)the National Natural Science Foundation of China(No.82170558).
文摘The gut microbiome shows changes under a plateau environment,while the disbalance of intestinal microbiota plays an important role in the pathogenesis of irritable bowel syndrome(IBS);however,the relationship between the two remains unexplored.In this work,we followed up a healthy cohort for up to a year before and after living in a plateau environment and performed 16S ribosomal RNA(rRNA)sequencing analysis of their fecal samples.Through evaluating the participants’clinical symptoms,combined with an IBS questionnaire,we screened the IBS sub-population in our cohort.The sequencing results showed that a high-altitude environment could lead to changes in the diversity and composition of gut flora.In addition,we found that the longer the time volunteers spent in the plateau environment,the more similar their gut microbiota composition and abundance became compared to those before entering the plateau,and IBS symptoms were significantly alleviated.Therefore,we speculated that the plateau may be a special environment that induces IBS.The taxonomic units g_Alistipes,g_Oscillospira,and s_Ruminococcus_torques,which had been proved to play important roles in IBS pathogenesis,were also abundant in the IBS cohort at high altitudes.Overall,the disbalance of gut microbiota induced by the plateau environment contributed to the high frequency of IBS and the psychosocial abnormalities associated with IBS.Our results prompt further research to elucidate the relevant mechanism.
基金support of the National Natural Science Foundation of China(Grant No.41201002)Foundation for Excellent Youth Scholars of Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences(Grant No.51Y184A61)+1 种基金China Postdoctoral Science Foundation funded project(Grant No.2012M512050)the National Natural Science Foundation of China(Grant No.41130533,41171010)
文摘The Zoige Wetland is located in the northeastern Qinghai-Tibetan Plateau, which is highly sensitive to global environment change and human disturbance because of its high elevation and cold environment, thus, it＇s a hotspot for land use and land cover change （LUCC） research. We used Landsat MSS images from 1975, Landsat ETM images from 2000, and Landsat TM images fi：om 1990 and 2005 to assess the LUCC in the study area, using GIS techniques, as well as topographic, vegetation, and soil maps combined with field investigations. The monitoring result shows that the study area＇s environment degraded rapidly between 1975 and 2005, including wetland shrinkage from 5,308 km2 to 4,980 lan2, sandy land expansion from 112 krn2 to 137 krn2, forest land decreasing from 5,686 km2 to 5,443 km2, and grassland degradation from 12,309 km2 to 10,672 km2. According to the analysis of meteorological data and social-economic statistical data, we concluded that the LUCC in the Zoige Wetland was caused by both natural and anthropogenic factors, but human activities were primarily responsible for the observed LUCC, thereby, we suggest human behaviors must be adjusted to control environmental degradation.
文摘The fluctuation of lake levels in Tibetan area may be well reflected by the landformevidences, especially the last highest lake levels. This, in a certain degree, is more suitable fordetermning the climatic humidity and aridity in macro scale compared with many other indicatorswhich are also sensitive to the sedimentary environmental change. According to the analyses of thelakes such as Tianshuihai Lake, Bangdag Co, Lungmu Co, Bangong Co, Serfing Co, Chabyer Caka,Qahan salt lake, Qinghai lake, the lake group in north-east Qiangtang and the lake group in southTibet. the authors thought that the lakes on the Tibetan Plateau generally appeared the high lakelevel during 40-25 ka BP. The plenty of water quantity may represent a special warm-humid stage inTibet area compared with the sub-warm-humid stage reflected by marine oxygen isotope records.Thus, there may existed different driving factors to climatic changes between the high latitUde areasand middle-low latitude mountains.
基金financially supported by the National key research and development program (2017YFD0800502)the National Natural Science Foundation of China (Grant Nos. 41573067, 41790444, 41471189, 31700414)
文摘Soil nitrogen(N) is critical to ecosystem services and environmental quality. Hotspots of soil N in areas with high soil moisture have been widely studied, however, their spatial distribution and their linkage with soil N variation have seldom been examined at a catchment scale in areas with low soil water content. We investigated the spatial variation of soil N and its hotspots in a mixed land cover catchment on the Chinese Loess Plateau and used multiple statistical methods to evaluate the effects of the critical environmental factors on soil N variation and potential hotspots. The results demonstrated that land cover, soil moisture, elevation, plan curvature and flow accumulation were the dominant factors affecting the spatial variation of soil nitrate(NN), while land cover and slope aspect were the most important factors impacting the spatial distribution of soil ammonium(AN) and total nitrogen(TN). In the studied catchment, the forestland, gully land and grassland were found to be the potential hotspots of soil NN, AN and TN accumulation, respectively. We concluded that land cover and slope aspect could be proxies to determine the potential hotspots of soil N at the catchment scale. Overall, land cover was the most important factor that resulted in the spatial variations of soil N. The findings may help us to better understand the environmental factors affecting soil N hotspots and their spatial variation at the catchment scale in terrestrial ecosystems.
文摘More and more concentrations have been focused on the uplift of the Tibetan Plateau and its effects on regional and global environment. The development of Asian monsoon has a close relationship with the uplift of the Tibetan Plateau. The understanding for the development of Asian monsoon is the key to the understanding of the process and the mechanism of the environmental evolution of the Asian region and to the understanding of the history of the uplift of the Tibetan Plateau. It is found that a big change of the Asian monsoon system occurred at about 2 6Ma ago. The winter monsoon strengthened (Ding et al.,1992 ), the change of winter monsoon began to in the opposite phase to the summer monsoon in East Asia (An et al., 1998 ), the tropical Southwest monsoon was hard to influence the North China (Li, 1999). However, whether there were changes in direction of winter monsoon and strength of summer monsoon occurred and how to change are still not clear. In this paper, the changes of the Asian monsoon system at about 2 6Ma ago are discussed, based on the reanalysis and combination of the results of atmospheric simulations and the geological records existed. It is suggested that, at about 2 6Ma ago, both winter monsoon and summer monsoon strengthened obviously, because that the amplitude of the climatic change increased a lot—warmer during the warm periods and colder during the cold periods. The direction of winter monsoon in Northern China changed from North—West—West to Northwest or North—West—North, because that the expansion direction of eolian\|deposit\|distribution area in China changed from mainly eastward to mainly southward. The area influenced by subtropical monsoon increased, but the area influenced by tropical monsoon decreased in China, because of the rising of the Tibetan Plateau and the southwest\|ward migration of the center of the Asian Low. At some time of the Pliocene, the tropical monsoon had penetrated onto the Qinghai\|Xizang region and influenced on the North China and Northwest China. However, after 2.6Ma B.P., the effects of the tropical monsoon on Northwest China and the northern part of the Tibetan Plateau decreased. All these suggest that the Tibetan Plateau perhaps reached about 2000m elevation at about 2 6Ma B.P..
