The Lhasa River Basin forms an essential human settlement area in the southern part of the Qinghai-Tibet Plateau.This study employed ecosystem service value(ESV)evaluation model,terrain gradient grading,and Geodetecto...The Lhasa River Basin forms an essential human settlement area in the southern part of the Qinghai-Tibet Plateau.This study employed ecosystem service value(ESV)evaluation model,terrain gradient grading,and Geodetector to analyze land use and ESV in the Lhasa River Basin from 1985 to 2020.The findings reveal that:(1)From 1985 to 2020,grassland was the dominant land use.There was a trend of grassland reduction and the expansion of other land types.(2)ESV has increased over the research period(with a total increase of 0.84%),with higher values in the southeast and lower values in the northwest.Grassland contributed the most to ESV,and climate regulation and hydrological regulation were the ecosystem services that contribute the most to ESV.(3)Natural factors like NDVI and altitude,as well as economic factors like population density and distance from roads,influenced the spatial differentiation of ESV,the explanatory power of NDVI reached up to 0.47.The interaction between factors had a greater impact than individual factors.These research results can provide theoretical support for national spatial planning and ecological environment protection in the Lhasa River Basin and other similar areas.展开更多
The Lhasa River Basin is one of the typical distribution regions of alpine wetlands on the Tibetan Plateau. It is very important to get a better understanding of the background and characteristics of alpine wetland fo...The Lhasa River Basin is one of the typical distribution regions of alpine wetlands on the Tibetan Plateau. It is very important to get a better understanding of the background and characteristics of alpine wetland for monitoring, protection and utilization. Wetland construction and distribution in the basin were analyzed based on multi-source data including field investigation data, CBERS remote sensing data and other thematic data provided by 3S technology. The results are （1） the total area of wetlands is 209,322.26 hm^2, accounting for 6.37% of the total land area of the basin. The wetlands are mainly dominated by natural wetland, with artificial wetland occupying only 1.09% of the wetland area; marsh wetland is the principal part of natural wetland, dominated by Kobresia littledalei swampy meadow which is distributed in the river source area and upstream of Chali, Damshung and Medro Gongkar counties. The ratio and type of wetlands in different counties differ significantly, which are widely distributed in Chali and Damshung counties （accounting for 62% of the total wetland area）. （2） The concentrated vertical distribution of wetlands is at an elevation of 3600-5100 m The wetlands are widely distributed throughout the Yarlung Zangbo River Valley from river source to river mouth into the Yarlung Zangbo River. Marsh wetland is dominant in the source area and upstream of the river, with the mosaic distribution of lakes, Kobresia litUedalei and Carex moorcroftii swampy meadow, shrubby swamp and river; as for the middle-down streams, the primary types are river wetland and flooded wetland. The distribution is in a mosaic pattern of river, Kobresia humilis and Carex moorcroftii swampy meadow, Phragmites australis and subordinate grass marsh, flooded wetland and artificial wetland.展开更多
Taking the Lhasa River Basin above Lhasa hydrological station in Tibetan Plateau as a study area, the characteristics of the annual and monthly mean runoff during 1956-2003 were analyzed, based on the hydro-data of th...Taking the Lhasa River Basin above Lhasa hydrological station in Tibetan Plateau as a study area, the characteristics of the annual and monthly mean runoff during 1956-2003 were analyzed, based on the hydro-data of the two hydrological stations （Lhasa and Tanggya） and the meteorological data of the three meteorological stations （Damxung, Lhasa and Tanggya）. The trends and the change points of runoff and climate from 1956 to 2003 were detected using the nonparametric Mann-Kendall test and Pettitt-Mann-Whitney change-point statistics. The correlations between runoff and climate change were analyzed using multiple linear regression. The major results could be summarized as follows： （1） The annual mean runoff during the last 50 years is characterized by a great fluctuation and a positive trend with two change points （around 1970 and the early 1980s）, after which the runoff tended to increase and was increasing intensively in the last 20 years. Besides, the monthly mean runoff with a positive trend is centralized in winter half-year （November to April） and some other months （May, July and September）. （2） The trends of the climate change in the study area are generally consistent with the trend of the runoff, but the leading climate factors which aroused the runoff variation are distinct. Precipitation is the dominant factor influencing the annual and monthly mean runoff in summer half year, while temperature is the primary factor in winter season.展开更多
Land use/land cover(LULC) is an important part of exploring the interaction between natural environment and human activities and achieving regional sustainable development. Based on the data of LULC types(cropland, fo...Land use/land cover(LULC) is an important part of exploring the interaction between natural environment and human activities and achieving regional sustainable development. Based on the data of LULC types(cropland, forest land, grassland, built-up land, and unused land) from 1990 to 2015, we analysed the intensity and driving factors of land use/cover change(LUCC) in the Yarlung Zangbo River,Nyang Qu River, and Lhasa River(YNL) region, Qinghai-Tibet Plateau of China, using intensity analysis method, cross-linking table method, and spatial econometric model. The results showed that LUCC in the YNL region was nonstationary from 1990 to 2015, showing a change pattern with "fast-slow-fast" and "U-shaped". Built-up land showed a steady increase pattern, while cropland showed a steady decrease pattern. The gain of built-up land mainly came from the loss of cropland. The transition pattern of LUCC in the YNL region was relatively single and stable during 1990–2015. The transition pattern from cropland and forest land to built-up land was a systematic change process of tendency and the transition pattern from grassland and unused land to cropland was a systematic change process of avoidance. The transition process of LUCC was the result of the combined effect of natural environment and social economic development in the YNL region. This study reveals the impact of ecological environment problems caused by human activities on the land resource system and provides scientific support for the study of ecological environment change and sustainable development of the Qinghai-Tibet Plateau.展开更多
A riverhead is the demarcation point of continuous water channel and seasonal channel, which is characterized by a criti- cal flow that can support a continuous water body. In this study, the critical support dischar...A riverhead is the demarcation point of continuous water channel and seasonal channel, which is characterized by a criti- cal flow that can support a continuous water body. In this study, the critical support discharge （CSD） is defined as the critical steady flows required to form the origin of a stream. The CSD is used as the criterion to determine the beginning of the riverhead, which can be controlled by hydro-climate factors （e.g., annual precipitation, annual evaporation, or minimum stream flow in arid season）. The CSD has a close correlation with the critical support/source area （CSA） that largely affects the density of the river network and the division of sub-watersheds. In general, river density may vary with regional meteorological and hydrological conditions that have to be considered in the analysis. In this paper, a new model referring to the relationship of CSA and CSD is proposed, which is based on the physical mechanism for the origin of riverheads. The feasibility of the model was verified using two watersheds （Duilongqu Basin of the Lhasa River and Beishuiqu Basin of the Nyangqu River） in Tibet Autonomous Region to calculate the CSA and extract river networks. A series of CSAs based on different CSDs in derived equation were tested by comparing the extracted river networks with the reference network obtained from a digitized map of river network at large scales. Comparison results of river networks derived from digital elevation model with real ones indicate that the CSD （equal to criterion of flow quantity （Qc）） are 0.0028 m3/s in Duilongqu and 0.0085 m3/s in Beishuiqu. Results show that the Qc can vary with hydro-climate conditions. The Qc is high in humid region and low in arid region, and the optimal Qo of 0.0085 m3/s in Beishuiqu Basin （humid region） is higher than 0.0028 m3/s in Duilongqu Basin （semi-arid region）. The suggested method provides a new application approach that can be used to determine the Qo of a riverhead in complex geographical regions, which can also reflect the effect of hydro-climate change on rivers supply in different regions.展开更多
In Lhasa River Basin(LRB),land suitable for settlement or living is experiencing a shortage of resources.Alluvial fans have the potential to alleviate this problem.However,basic information,such as the distribution an...In Lhasa River Basin(LRB),land suitable for settlement or living is experiencing a shortage of resources.Alluvial fans have the potential to alleviate this problem.However,basic information,such as the distribution and land use types of alluvial fans,is rarely studied.In this study,Google Earth,ArcGIS and visual interpretation were used to obtain the outlines,areas,quantities and distribution of alluvial fans.Meanwhile,to show the utilisation potential of alluvial fans,we analysed the land use,their distance from the roads,places(town and village)and rivers.The results showed 826 alluvial fans exist in LRB,with a total area of 1166.03 km2.The number of alluvial fans with areas between 0.1 and 1 km2 is 517,accounting for 62.59%of the total number of alluvial fans.Grassland is the dominant land use type,accounting for 68.70%of the total area of alluvial fans.The cropland area accounted for 2.16%of alluvial fans and accounted for 18.98%of the total cropland area in LRB.Exactly 93.70%,53.63%and 61.86%of the total number of alluvial fans were located within 5 km from the tertiary road,village,and river,respectively.To sum up,our survey results showed that alluvial fans are important land resources in LRB and may have huge utilisation potential.展开更多
Alluvial fans are an important land resource in the Qinghai-Tibet Plateau with the expansion of human activities. However, the factors of alluvial fan development are poorly understood. According to our previous inves...Alluvial fans are an important land resource in the Qinghai-Tibet Plateau with the expansion of human activities. However, the factors of alluvial fan development are poorly understood. According to our previous investigation and research, approximately 826 alluvial fans exist in the Lhasa River Basin(LRB). The main purpose of this work is to identify the main influencing factors by using machine learning. A development index(Di) of alluvial fan was created by combining its area, perimeter, height and gradient. The 72% of data, including Di, 11 types of environmental parameters of the matching catchment of alluvial fan and 10 commonly used machine learning algorithms were used to train and build models.The 18% of data were used to validate models. The remaining 10% of data were used to test the model accuracy. The feature importance of the model was used to illustrate the significance of the 11 types of environmental parameters to Di. The primary modelling results showed that the accuracy of the ensemble models, including Gradient Boost Decision Tree,Random Forest and XGBoost, are not less than 0.5(R^(2)). The accuracy of the Gradient Boost Decision Tree and XGBoost improved after grid research, and their R^(2) values are 0.782 and 0.870, respectively. The XGBoost was selected as the final model due to its optimal accuracy and generalisation ability at the sites closest to the LRB. Morphology parameters are the main factors in alluvial fan development, with a cumulative value of relative feature importance of 74.60% in XGBoost. The final model will have better accuracy and generalisation ability after adding training samples in other regions.展开更多
By measuring and comparing δD, δ18O, and 3H values of different sections in Lhasa River, we can trace its water resource and water environment. We have concluded that the upper reaches of the Lhasa River are mainly ...By measuring and comparing δD, δ18O, and 3H values of different sections in Lhasa River, we can trace its water resource and water environment. We have concluded that the upper reaches of the Lhasa River are mainly supplied by melt-water (with lower 3H value and mineralization degree) and underground water (with lower 3H value and higher mineralization degree). The middle reaches are mainly supplied by rainwater (with higher 3H value and mineralization degree).展开更多
土地利用变化对生态文明建设产生强烈影响,进而威胁经济社会与生态环境的可持续发展。基于高精度土地利用数据,分析了拉萨河流域2000—2020年土地利用和生态系统服务价值(Ecosystem Service Value,ESV)时空演变特征,并借助PLUS模型和地...土地利用变化对生态文明建设产生强烈影响,进而威胁经济社会与生态环境的可持续发展。基于高精度土地利用数据,分析了拉萨河流域2000—2020年土地利用和生态系统服务价值(Ecosystem Service Value,ESV)时空演变特征,并借助PLUS模型和地理探测器分别探索了土地利用变化和ESV空间分异的驱动因素。结果表明:(1)2000—2020年拉萨河流域土地利用以草地为主,占流域总面积的85.23%。土地利用呈草地缩减,其余地类扩张的趋势。其中,草地减少2.45%,建设用地、水域和林地分别扩张199.72%、44.64%和21.97%。(2)流域土地利用变化受海拔、年均地温、距湖泊和水库距离等因素影响,其中,海拔对耕地、林地、水域和建设用地扩张的贡献度分别高达0.18、0.11、0.28和0.13,坡度和年均地温对草地和未利用地变化的贡献度分别为0.14和0.15。(3)2000—2020年流域ESV总体增加1.14%(14.96×108元),草地和气候调节分别为ESV贡献最突出的土地利用类型和生态系统服务类型,两者的贡献率分别为87.13%和25.50%。(4)流域ESV具有显著空间分异性,受NDVI、海拔、年均风速和年均气温等因子影响。其中,NDVI的解释力高达0.46,任意两两因子的交互均会增强ESV的分异性。研究结果可为拉萨河流域及类似区域国土空间规划和生态文明建设提供科学参考。展开更多
This paper presents a description of the river terrace at Tangjia Village in Lhasa, Tibet. Selected types of phytolith and pollen were used as proxies to study the paleoclimate in the study area. Ancient climate and v...This paper presents a description of the river terrace at Tangjia Village in Lhasa, Tibet. Selected types of phytolith and pollen were used as proxies to study the paleoclimate in the study area. Ancient climate and vegetation changes since 10 ka BP were examined. The results demonstrated that between 10.2 and 8.9 ka BP, the dominating phytolith was the cold type and the dominating vegetation type was grassland-forest. This indicated that the climate changed from cool-humid to cool-dry and later turned back into a cool-humid climate. Between 8.9 and 8.1 ka BP, the main types of phytoliths were tooth, dumbbell, and polyhedral. This suggests that the vegetation consisted of forest-grassland and the period＇s climate had become warmer. Between 8.1 and 6.7 ka BP, the warm index of phytolith assembelage gradually increased, whereas the spore and pollen assembelage revealed that the vegetation was forest with hardwood. This suggested that the paleoclimate was warmest in this period. The herbaceous vegetation increased gradually, indicating that the climate had become colder since 7.5 ka BP. Between 6.7 and 4.6 ka BP, cold type phytolith such as tooth and cap were found. Simultaneously, the pollen assembelage indicated that the vegetation shifted from grassland to forest and then turned back into grassland. This implies that the climate fluctuated from cold-dry to cool- humid. Between 4.6 and 1.9 ka BP, the dominate type of phytolith was cold type and its warm index was in the range 0.04-0.28, suggesting a herbaceous vegetation cover and indicating that the climate was cold. The phytolith warm index from 1.9 ka BP revealed that the climate was continuously decreasing, and most of the pollen assembelage consisted of Chenopodiaceae and Artemisia. This conclusion is in agreement with the phytolith result that indicates that the climate was becoming colder and colder.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.U20A20112)Construction of Talent Innovation Team and Laboratory Platform of Tibet University-Construction of Plateau Geothermal New Energy Innovation Team and Laboratory Platform(Grant No.2022ZDTD10)Central Support for Local Ministry and Regional Joint Construction/First-class Everest Construction Project-Construction of Geological Resources and Geological Engineering Characteristics(Grant No.Tibetan Finance Pre-indication[2022]No.1).
文摘The Lhasa River Basin forms an essential human settlement area in the southern part of the Qinghai-Tibet Plateau.This study employed ecosystem service value(ESV)evaluation model,terrain gradient grading,and Geodetector to analyze land use and ESV in the Lhasa River Basin from 1985 to 2020.The findings reveal that:(1)From 1985 to 2020,grassland was the dominant land use.There was a trend of grassland reduction and the expansion of other land types.(2)ESV has increased over the research period(with a total increase of 0.84%),with higher values in the southeast and lower values in the northwest.Grassland contributed the most to ESV,and climate regulation and hydrological regulation were the ecosystem services that contribute the most to ESV.(3)Natural factors like NDVI and altitude,as well as economic factors like population density and distance from roads,influenced the spatial differentiation of ESV,the explanatory power of NDVI reached up to 0.47.The interaction between factors had a greater impact than individual factors.These research results can provide theoretical support for national spatial planning and ecological environment protection in the Lhasa River Basin and other similar areas.
基金The National Key Technology Research and Development Program,No.2007BAC06B03National Basic Research Program of China,No.2005CB422000
文摘The Lhasa River Basin is one of the typical distribution regions of alpine wetlands on the Tibetan Plateau. It is very important to get a better understanding of the background and characteristics of alpine wetland for monitoring, protection and utilization. Wetland construction and distribution in the basin were analyzed based on multi-source data including field investigation data, CBERS remote sensing data and other thematic data provided by 3S technology. The results are （1） the total area of wetlands is 209,322.26 hm^2, accounting for 6.37% of the total land area of the basin. The wetlands are mainly dominated by natural wetland, with artificial wetland occupying only 1.09% of the wetland area; marsh wetland is the principal part of natural wetland, dominated by Kobresia littledalei swampy meadow which is distributed in the river source area and upstream of Chali, Damshung and Medro Gongkar counties. The ratio and type of wetlands in different counties differ significantly, which are widely distributed in Chali and Damshung counties （accounting for 62% of the total wetland area）. （2） The concentrated vertical distribution of wetlands is at an elevation of 3600-5100 m The wetlands are widely distributed throughout the Yarlung Zangbo River Valley from river source to river mouth into the Yarlung Zangbo River. Marsh wetland is dominant in the source area and upstream of the river, with the mosaic distribution of lakes, Kobresia litUedalei and Carex moorcroftii swampy meadow, shrubby swamp and river; as for the middle-down streams, the primary types are river wetland and flooded wetland. The distribution is in a mosaic pattern of river, Kobresia humilis and Carex moorcroftii swampy meadow, Phragmites australis and subordinate grass marsh, flooded wetland and artificial wetland.
基金National Basic Research Program of China, No.2005CB422006 National Natural Science Foundation of China, No.90202012 No.40561002
文摘Taking the Lhasa River Basin above Lhasa hydrological station in Tibetan Plateau as a study area, the characteristics of the annual and monthly mean runoff during 1956-2003 were analyzed, based on the hydro-data of the two hydrological stations （Lhasa and Tanggya） and the meteorological data of the three meteorological stations （Damxung, Lhasa and Tanggya）. The trends and the change points of runoff and climate from 1956 to 2003 were detected using the nonparametric Mann-Kendall test and Pettitt-Mann-Whitney change-point statistics. The correlations between runoff and climate change were analyzed using multiple linear regression. The major results could be summarized as follows： （1） The annual mean runoff during the last 50 years is characterized by a great fluctuation and a positive trend with two change points （around 1970 and the early 1980s）, after which the runoff tended to increase and was increasing intensively in the last 20 years. Besides, the monthly mean runoff with a positive trend is centralized in winter half-year （November to April） and some other months （May, July and September）. （2） The trends of the climate change in the study area are generally consistent with the trend of the runoff, but the leading climate factors which aroused the runoff variation are distinct. Precipitation is the dominant factor influencing the annual and monthly mean runoff in summer half year, while temperature is the primary factor in winter season.
基金jointly supported by the Second Tibetan Plateau Scientific Expedition and Research of China(2019QZKK0603)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20040200)Reconstruction of Historical Cultivated Land and Human Activities around the North Slope of Everest Area of China(42061023)。
文摘Land use/land cover(LULC) is an important part of exploring the interaction between natural environment and human activities and achieving regional sustainable development. Based on the data of LULC types(cropland, forest land, grassland, built-up land, and unused land) from 1990 to 2015, we analysed the intensity and driving factors of land use/cover change(LUCC) in the Yarlung Zangbo River,Nyang Qu River, and Lhasa River(YNL) region, Qinghai-Tibet Plateau of China, using intensity analysis method, cross-linking table method, and spatial econometric model. The results showed that LUCC in the YNL region was nonstationary from 1990 to 2015, showing a change pattern with "fast-slow-fast" and "U-shaped". Built-up land showed a steady increase pattern, while cropland showed a steady decrease pattern. The gain of built-up land mainly came from the loss of cropland. The transition pattern of LUCC in the YNL region was relatively single and stable during 1990–2015. The transition pattern from cropland and forest land to built-up land was a systematic change process of tendency and the transition pattern from grassland and unused land to cropland was a systematic change process of avoidance. The transition process of LUCC was the result of the combined effect of natural environment and social economic development in the YNL region. This study reveals the impact of ecological environment problems caused by human activities on the land resource system and provides scientific support for the study of ecological environment change and sustainable development of the Qinghai-Tibet Plateau.
基金Under the auspices of National Natural Science Foundation of China(No.31070405)Knowledge Innovation Programs of Chinese Academy of Sciences(No.KZCX2-XB3-08)
文摘A riverhead is the demarcation point of continuous water channel and seasonal channel, which is characterized by a criti- cal flow that can support a continuous water body. In this study, the critical support discharge （CSD） is defined as the critical steady flows required to form the origin of a stream. The CSD is used as the criterion to determine the beginning of the riverhead, which can be controlled by hydro-climate factors （e.g., annual precipitation, annual evaporation, or minimum stream flow in arid season）. The CSD has a close correlation with the critical support/source area （CSA） that largely affects the density of the river network and the division of sub-watersheds. In general, river density may vary with regional meteorological and hydrological conditions that have to be considered in the analysis. In this paper, a new model referring to the relationship of CSA and CSD is proposed, which is based on the physical mechanism for the origin of riverheads. The feasibility of the model was verified using two watersheds （Duilongqu Basin of the Lhasa River and Beishuiqu Basin of the Nyangqu River） in Tibet Autonomous Region to calculate the CSA and extract river networks. A series of CSAs based on different CSDs in derived equation were tested by comparing the extracted river networks with the reference network obtained from a digitized map of river network at large scales. Comparison results of river networks derived from digital elevation model with real ones indicate that the CSD （equal to criterion of flow quantity （Qc）） are 0.0028 m3/s in Duilongqu and 0.0085 m3/s in Beishuiqu. Results show that the Qc can vary with hydro-climate conditions. The Qc is high in humid region and low in arid region, and the optimal Qo of 0.0085 m3/s in Beishuiqu Basin （humid region） is higher than 0.0028 m3/s in Duilongqu Basin （semi-arid region）. The suggested method provides a new application approach that can be used to determine the Qo of a riverhead in complex geographical regions, which can also reflect the effect of hydro-climate change on rivers supply in different regions.
基金The Strategic Priority Research Program of Chinese Academy of Sciences,No.XDA20040202The Second Tibetan Plateau Scientific Expedition and Research Program(STEP),No.2019QZKK0603。
文摘In Lhasa River Basin(LRB),land suitable for settlement or living is experiencing a shortage of resources.Alluvial fans have the potential to alleviate this problem.However,basic information,such as the distribution and land use types of alluvial fans,is rarely studied.In this study,Google Earth,ArcGIS and visual interpretation were used to obtain the outlines,areas,quantities and distribution of alluvial fans.Meanwhile,to show the utilisation potential of alluvial fans,we analysed the land use,their distance from the roads,places(town and village)and rivers.The results showed 826 alluvial fans exist in LRB,with a total area of 1166.03 km2.The number of alluvial fans with areas between 0.1 and 1 km2 is 517,accounting for 62.59%of the total number of alluvial fans.Grassland is the dominant land use type,accounting for 68.70%of the total area of alluvial fans.The cropland area accounted for 2.16%of alluvial fans and accounted for 18.98%of the total cropland area in LRB.Exactly 93.70%,53.63%and 61.86%of the total number of alluvial fans were located within 5 km from the tertiary road,village,and river,respectively.To sum up,our survey results showed that alluvial fans are important land resources in LRB and may have huge utilisation potential.
基金The Strategic Priority Research Program of Chinese Academy of Sciences,No.XDA20040202The Second Tibetan Plateau Scientific Expedition and Research Program (STEP),No.2019QZKK0603。
文摘Alluvial fans are an important land resource in the Qinghai-Tibet Plateau with the expansion of human activities. However, the factors of alluvial fan development are poorly understood. According to our previous investigation and research, approximately 826 alluvial fans exist in the Lhasa River Basin(LRB). The main purpose of this work is to identify the main influencing factors by using machine learning. A development index(Di) of alluvial fan was created by combining its area, perimeter, height and gradient. The 72% of data, including Di, 11 types of environmental parameters of the matching catchment of alluvial fan and 10 commonly used machine learning algorithms were used to train and build models.The 18% of data were used to validate models. The remaining 10% of data were used to test the model accuracy. The feature importance of the model was used to illustrate the significance of the 11 types of environmental parameters to Di. The primary modelling results showed that the accuracy of the ensemble models, including Gradient Boost Decision Tree,Random Forest and XGBoost, are not less than 0.5(R^(2)). The accuracy of the Gradient Boost Decision Tree and XGBoost improved after grid research, and their R^(2) values are 0.782 and 0.870, respectively. The XGBoost was selected as the final model due to its optimal accuracy and generalisation ability at the sites closest to the LRB. Morphology parameters are the main factors in alluvial fan development, with a cumulative value of relative feature importance of 74.60% in XGBoost. The final model will have better accuracy and generalisation ability after adding training samples in other regions.
文摘By measuring and comparing δD, δ18O, and 3H values of different sections in Lhasa River, we can trace its water resource and water environment. We have concluded that the upper reaches of the Lhasa River are mainly supplied by melt-water (with lower 3H value and mineralization degree) and underground water (with lower 3H value and higher mineralization degree). The middle reaches are mainly supplied by rainwater (with higher 3H value and mineralization degree).
文摘土地利用变化对生态文明建设产生强烈影响,进而威胁经济社会与生态环境的可持续发展。基于高精度土地利用数据,分析了拉萨河流域2000—2020年土地利用和生态系统服务价值(Ecosystem Service Value,ESV)时空演变特征,并借助PLUS模型和地理探测器分别探索了土地利用变化和ESV空间分异的驱动因素。结果表明:(1)2000—2020年拉萨河流域土地利用以草地为主,占流域总面积的85.23%。土地利用呈草地缩减,其余地类扩张的趋势。其中,草地减少2.45%,建设用地、水域和林地分别扩张199.72%、44.64%和21.97%。(2)流域土地利用变化受海拔、年均地温、距湖泊和水库距离等因素影响,其中,海拔对耕地、林地、水域和建设用地扩张的贡献度分别高达0.18、0.11、0.28和0.13,坡度和年均地温对草地和未利用地变化的贡献度分别为0.14和0.15。(3)2000—2020年流域ESV总体增加1.14%(14.96×108元),草地和气候调节分别为ESV贡献最突出的土地利用类型和生态系统服务类型,两者的贡献率分别为87.13%和25.50%。(4)流域ESV具有显著空间分异性,受NDVI、海拔、年均风速和年均气温等因子影响。其中,NDVI的解释力高达0.46,任意两两因子的交互均会增强ESV的分异性。研究结果可为拉萨河流域及类似区域国土空间规划和生态文明建设提供科学参考。
基金funded by the National Science Foundation of China 40872002 and 41063001the Open Foundation of State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry(201004)+1 种基金the Youth Science Foundation of Jiangxi University of Science and Technology (JXXJBS12006)the China Geological Survey (No.1212010818085)
文摘This paper presents a description of the river terrace at Tangjia Village in Lhasa, Tibet. Selected types of phytolith and pollen were used as proxies to study the paleoclimate in the study area. Ancient climate and vegetation changes since 10 ka BP were examined. The results demonstrated that between 10.2 and 8.9 ka BP, the dominating phytolith was the cold type and the dominating vegetation type was grassland-forest. This indicated that the climate changed from cool-humid to cool-dry and later turned back into a cool-humid climate. Between 8.9 and 8.1 ka BP, the main types of phytoliths were tooth, dumbbell, and polyhedral. This suggests that the vegetation consisted of forest-grassland and the period＇s climate had become warmer. Between 8.1 and 6.7 ka BP, the warm index of phytolith assembelage gradually increased, whereas the spore and pollen assembelage revealed that the vegetation was forest with hardwood. This suggested that the paleoclimate was warmest in this period. The herbaceous vegetation increased gradually, indicating that the climate had become colder since 7.5 ka BP. Between 6.7 and 4.6 ka BP, cold type phytolith such as tooth and cap were found. Simultaneously, the pollen assembelage indicated that the vegetation shifted from grassland to forest and then turned back into grassland. This implies that the climate fluctuated from cold-dry to cool- humid. Between 4.6 and 1.9 ka BP, the dominate type of phytolith was cold type and its warm index was in the range 0.04-0.28, suggesting a herbaceous vegetation cover and indicating that the climate was cold. The phytolith warm index from 1.9 ka BP revealed that the climate was continuously decreasing, and most of the pollen assembelage consisted of Chenopodiaceae and Artemisia. This conclusion is in agreement with the phytolith result that indicates that the climate was becoming colder and colder.
