To explore air contamination resulting from special biomass combustion and suspended dust in Lhasa,the present study focused on the size distribution and chemical characteristics of particulate matter(PM)emission resu...To explore air contamination resulting from special biomass combustion and suspended dust in Lhasa,the present study focused on the size distribution and chemical characteristics of particulate matter(PM)emission resulting from 7 types of non-fossil pollution sources.We investigated the concentration and size distribution of trace elements from 7 pollution sources collected in Lhasa.Combining Lhasa’s atmospheric particulate matter data,enrichment factors(EFs)have been calculated to examine the potential impact of those pollution sources on the atmosphere quality of Lhasa.The highest mass concentration of total elements of biomass combustion appeared at PM_(0.4),and the second highest concentration existed in the size fraction 0.4-1μm;the higher proportion(12%)of toxicmetals was produced by biomass combustion.The elemental composition of suspended dust and atmospheric particulate matter was close(except for As and Cd);the highest concentration of elements was all noted in PM_(2.5-10)(PM_(3-10)).Potassium was found to be one of the main biomass markers.The proportion of Cu in suspended dust is significantly lower than that of atmospheric particulate matter(0.53%and 3.75%),which indicates that there are other anthropogenic sources.The EFs analysis showed that the Cr,Cu,Zn,and Pb produced by biomass combustion were highly enriched(EFs>100)in all particle sizes.The EFs of most trace elements increased with decreasing particle size,indicating the greater influence of humanfactors on smaller particles.展开更多
Multiple instances of the Late Cretaceous granodiorites within the Anglonggangri region of the northwestern Lhasa Block were identified,their petrogenesis were explored and mineralization potential were assessed.The z...Multiple instances of the Late Cretaceous granodiorites within the Anglonggangri region of the northwestern Lhasa Block were identified,their petrogenesis were explored and mineralization potential were assessed.The zircon U-Pb dating of the Anglonggangri granodiorites revealed ages of 82.8 and 80.8 Ma.Granodiorite samples have SiO2 contents of 64.36-68.33 wt%,with high Sr/Y(55-95)and A/CNK ratios(0.99-1.06).Zirconε_(Hf)(t)values range from−0.3 to+16.2.Two granodiorite samples have(^(87)Sr/^(86)Sr)i values of 0.7034 and 0.7043 and positiveɛNd(t)values of 3.51 and 3.83.These geochemical properties indicate that they are adakitic rocks formed by partial melting of the juvenile thickened lower crust,slightly contaminated with material from the mantle due to the small-scale delamination of the lower crust.The zircons in the granodiorites have moderate Ce/Nd(2.5-43),logfO2(−20.0 to−9.6),andΔFMQ(−1.28 to+4.00)values;low(Ce/Nd)/Y(0.001-0.049)ratios;and high Dy/Yb(0.17-1.16)ratios,which indicate that these granodiorites exhibit moderate oxygen fugacity and lower magma water content than the Miocene Gangdese porphyry copper deposits associated with high-Sr/Y granites.Their ability to create porphyry-type copper deposits could have been hampered by their low magma water content and moderate oxygen fugacity.展开更多
The high Ba-Sr rocks can provide significant clues about the evolution of the continent lithosphere,but their petrogenesis remains controversial.Identifying the Late Cretaceous high Ba-Sr granodiorites in the SE Lhasa...The high Ba-Sr rocks can provide significant clues about the evolution of the continent lithosphere,but their petrogenesis remains controversial.Identifying the Late Cretaceous high Ba-Sr granodiorites in the SE Lhasa Block could potentially provide valuable insights into the continent evolution of the Qinghai-Tibet Plateau.Zircon U-Pb ages suggest that the granodiorites were emplaced at 87.32±0.43 Ma.Geochemically,the high Ba-Sr granodiorites are characterized by elevated K_(2)O+Na_(2)O contents(8.18-8.73 wt%)and K_(2)O/Na_(2)O ratios(0.99-1.25,mostly>1),and belong to high-K calc-alkaline to shoshonitic series.The Yonglaga granodiorites show notably high Sr(653-783 ppm)and Ba(1346-1531 ppm)contents,plus high Sr/Y(30.92-38.18)and(La/Yb)_(N)(27.7-34.7)ratios,but low Y(20.0-22.8 ppm)and Yb(1.92-2.19 ppm)contents with absence of negative Eu anomalies(δEu=0.83-0.88),all similar to typical high Ba-Sr granitoids.The variable zirconεHf(t)values of-4.58 to+12.97,elevated initial^(87)Sr/^(86)Sr isotopic ratios of 0.707254 to 0.707322 and lowεNd(t)values of-2.8 to-3.6 with decoupling from the Hf system suggest that a metasomatized mantle source included significant recycled ancient materials.The occurrence of such high Ba-Sr intrusions indicates previous contributions of metasomatized mantle-derived juvenile material to the continents,which imply the growth of continental crust during the Late Cretaceous in the SE Lhasa.Together with regional data,we infer that the underplated mafic magma provides a significant amount of heat,which leads to partial melting of the juvenile crust.The melting of the metasomatized mantle could produce a juvenile mafic lower crust,from which the high Ba-Sr granitoids were derived from reworking of previous mafic crust during the Late Cretaceous(ca.100-80 Ma)in the SE Lhasa.展开更多
Lhasa,a city rich in history,is often celebrated as a fertile ground for the flourishing of museums.Among the museums in Lhasa,some chronicle the region's profound historical roots,some explore the wonders of natu...Lhasa,a city rich in history,is often celebrated as a fertile ground for the flourishing of museums.Among the museums in Lhasa,some chronicle the region's profound historical roots,some explore the wonders of nature,some preserve vibrant cultural heritage,and others capture the rhythms of everyday life.展开更多
On April 30,the 22nd China Xiza ng Mountai neering Conventi on in 2025 comme need.As its flagship eve nt,the Luodui Peak Mountaineering Expedition took place from May 2 to 3 in Yangbajain Town of Lhasa,attracting more...On April 30,the 22nd China Xiza ng Mountai neering Conventi on in 2025 comme need.As its flagship eve nt,the Luodui Peak Mountaineering Expedition took place from May 2 to 3 in Yangbajain Town of Lhasa,attracting more than 160 mountain climbing enthusiasts from all over the country.展开更多
Basalts from the Late Carboniferous to Early Permian are extensively developed in the central Lhasa subterrane,southern Xizang.Studying the petrogenesis of these rocks may have implications for the late Paleozoic arc ...Basalts from the Late Carboniferous to Early Permian are extensively developed in the central Lhasa subterrane,southern Xizang.Studying the petrogenesis of these rocks may have implications for the late Paleozoic arc magmatism along the central Lhasa subterrane uncovering more of the evolution of the Sumdo Paleo-Tethys Ocean and its dynamic mechanism.Basalt samples from the Luobadui Formation in the Leqingla area,NW of Linzhou City in the central Lhasa subterrane,southern Xizang exhibit arc-like geochemical signatures in a subduction-zone tectonic setting characterized by high Al_(2)O_(3)and low TiO_(2)contents,fractionated REE patterns with low Nb/La ratios and high LREE concentrations,and negative HFSE anomalies.Based on their higher Th/Ce,Nb/Zr,and lower Ba/Th,Pb/Nd ratios,slightly negative to positiveε_(Nd)(t)values,and the relatively high Sr-Pb isotopic compositions,these samples were probably derived from partial melting of a depleted mantle source of garnet+spinel lherzolite,metasomatized by subducted sediments around 297 Ma.Modeling of the trace elements indicates that these basalts experienced fractional crystallization of olivine,clinopyroxene and minor plagioclase during magma ascent and eruption.It is proposed that these Late Carboniferous–Early Permian basalts are associated with the northward subduction of the Sumdo Paleo-Tethys Ocean seafloor along the southern margin of the central Lhasa subterrane.展开更多
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 variation characteristics of ozone in Lhasa in recent years were analyzed by using Brewer spectrometer observation data. The results showed that ozone was mainly distributed in 15-35 km in atmosphere in Lhasa; the...The variation characteristics of ozone in Lhasa in recent years were analyzed by using Brewer spectrometer observation data. The results showed that ozone was mainly distributed in 15-35 km in atmosphere in Lhasa; the peak value by inversion was in 21-25 km; by comparison of ozone vertical distribution in Lhasa, it can be concluded that ozone differs insignificantly in middle-to-high layers in stratosphere and the distribution is similar over 36 km. The difference can be observed from the fact that ozone concentration is higher in winter and spring compared with summer and autumn from ground to the height at 21 km. In recent 4 years, annual average of total ozone in Lhasa was of little variations and extreme values of ozone appeared in winter and spring. Monthly averages were lower in August and September, and the lower value of ozone kept longer in 2008 for 23 d.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
A huge thrust system, the North Lhasa Thrust (NLT), was discovered in the northern Lhasa block of the Tibetan Plateau based on geological mapping of the Damxung region and its vicinity, the Deqen-Lunpola traverse and ...A huge thrust system, the North Lhasa Thrust (NLT), was discovered in the northern Lhasa block of the Tibetan Plateau based on geological mapping of the Damxung region and its vicinity, the Deqen-Lunpola traverse and the Amdo-Bam Co profile. The NLT consists of the Dongqiao-Lunpola thrust (DLT), the west Namco thrust (WNT) and the south Damxung thrust (SDT) and ductile shear zones, ophiolite slices and folds extending in a WNW direction. Major thrust faults of the NLT seem to merge into a single deep-seated detachment of the upper-crust and totally displaced southward as far as 100-120 km. Chronological analyses with 39Ar-40Ar of plagioclase and hornblende, Rb-Sr isochron of minerals and fission-tracks of apatite from mylonite within the WNT yield ages of 174-173 Ma, 109 Ma and 44 Ma, showing 3 periods of thrusting in the north Lhasa block caused by subduction of the Tethys oceanic plate and the India-Eurasia continental collision respectively.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
Recently, an over 100 km long MORB-type eclogite belt of Permian was discovered in the Sumdo （松多） region of the Lhasa block, Tibet. A critical question thus is： what is the tectonic setting of the eelogite belt a...Recently, an over 100 km long MORB-type eclogite belt of Permian was discovered in the Sumdo （松多） region of the Lhasa block, Tibet. A critical question thus is： what is the tectonic setting of the eelogite belt and is it related to an unrecognized suture in the region？ Further investigations show that there are some mafic and ultramafic rocks spacially associated with the eclogite belt in the region. Three ultramafic massifs were recognized in the Sumdo region, and called the Luomaling （罗马岭）, Gongbupala （贡布爬拉） and Qiazhasumdo （卡扎松多） massifs. All the massifs are fault-contacted with greenschist （Chasagang （岔萨岗） Formation） or muscovite-quartz schist （Mabuku （马布库） Formation）, and individuals are about 100 m×50 m in size extending in EW as the regional structure. All the ultramafic rocks have been entirely serpentinized, and the Gongbupala massif has been selected for study in geochemistry. Eleven chemical analyses of the rocks from the Gongbupala massif show a narrow range in contents： SiO2 （35.97-40.63） wt.%, MgO （37.02-38.60） wt.%, TiO2 （0.01-0.08） wt.%, Al2O3 （0.80-1.64） wt.%, （Na2O＋K2O） less than 0.1 wt.%, with high volatile contents （H2O＋CO2） （11.24-14.91） wt.%. After recalculation without H2O＋CO2, the mean values are SiO2 45.24 wt.%, MgO 43.54 wt.%, FeOT （7.45-9.97） wt.% （8.55 wt.% in average）, （MgO＋FeOT） 52.09 wt.%, Mg# （100×Mg/（Mg＋Fe＊）, where Fe＊ represents total Fe）=89.42-90.08, （m＋f）/Si （（atomicity Mg＋atomicity Fe） /atomicity Si）=1.53-1.75 （1.59 in average）, respectively. The mean M/F （atomicity Mg/atomicity Fe） ratio of the rocks is 9.05, which is classified as magnesium enriched-type of ultramafic rocks. The compositional features, depleted in K, Na, Ca, AI and Ti and enriched in Mg#, indicate the characteristics of peridotite originated from a depleted mantle. The rocks have low REE with ∑（1.60-2.68）×10^-6 similar to those of the primitive mantle. The chondrite-normalized REE patterns of all samples show slightly enrichment in LREE, with （Ce/Yb）N 1.03-2.46, but a little depleted in HREE. Most samples show a slight negative anomaly in Eu, a feature in REE from a relic mantle and common features in highly serpentinized ultramafic rocks in the Yarlung-Zangbo （雅鲁藏布） ophiolite and the Bangong （班公）-Nujiang （怒江） ophiolite in Tibet. The primitive mantle-normalized spiderdiagram of trace elements for Gongbupala ultramafic rocks yields uniform distributed pattern. They are relatively enriched in Rb, Ba, La, P element （LHSE） and depleted in Sm, Ti, Y, Yb element （HFSE）, a feature of metasomatic mantle peridotite. The geochemical features of the rocks suggest that the protolith of Gongbupala serpentinite in Sumdo region is harzburgite, a typical depleted mantle rock, and may represent a dismembered ophiolite unit in the region.展开更多
Based on a total of 519 images,the composite images with the lowest possible cloud cover were generated at pixel level with image synthesis method on Google Earth Engine(GEE)platform.The Remote Sensing Ecological Inde...Based on a total of 519 images,the composite images with the lowest possible cloud cover were generated at pixel level with image synthesis method on Google Earth Engine(GEE)platform.The Remote Sensing Ecological Index(RSEI)was adopted,and calculated in an efficient way with the assistance of parallel cloud computing of the GEE platform.The RSEI was used in this paper to evaluate and monitor the eco-environmental quality of the Lhasa Metropolitan Area.Results show that:(1)The ecological quality is better in the west than in the east of Lhasa Metropolitan Area,with Lhasa as an approximate dividing point.The ecological quality improved and then deteriorated dramatically before 2000,with the mean RSEI value dropping from 0.51 to 0.46;the trend was followed by a gradual increase up until 2017,with the mean RSEI value increased from 0.46 to 0.55.(2)The RSEI is weakly and positively correlated with socioeconomic indicators.This indicates that the population growth and economic development did not negatively influence the ecological quality,but actually boosted it.(3)The GEE can serve as an efficient computing platform for the assessment and monitoring of eco-environmental quality in vast regions.展开更多
The southern Lhasa Terrane is famous for its huge magmatic belt which records the magmatism during Mesozoic and Cenozoic. Although the Mesozoic continental-margin setting in the southern Lhasa Terrane has been identif...The southern Lhasa Terrane is famous for its huge magmatic belt which records the magmatism during Mesozoic and Cenozoic. Although the Mesozoic continental-margin setting in the southern Lhasa Terrane has been identified, details of this tectonic setting and the evolution history during the Late Cretaceous remain unclear. To further constrain these issues, we present zircon LA-ICP-MS U-Pb, Hf isotopic and geochemical data of the Gongbari dacites （of the Sangri Group） which intruded by Paleocene granodiorites from the eastern part of the southern Lhasa Terrane, Tibet. New age data indicate that the dacites were generated at -95.4 Ma, which suggests the Sangri Group volcanism may last to Late Cretaceous. The Gongbari dacites are characterized by high Sr （428-758 ppm） contents, low concentration of heavy rare earth elements and Y （e.g. Yb=0.78-1.14 ppm; Y=8.85-11.4 ppm） with high Sr/Y （41.91-67.59） and La/Yb （22.64-30.64） ratios, similar to those of adakite. The rocks are calc-alkaline, metaluminous, enriched in LILEs, depleted in HFSEs, and have positive tar（t） values （＋7.7 to ＋11.6）. The Gongbari dacites were probably produced by partial melting of young and hot subducted Neo- Tethyan oceanic crust under amphibolite to garnet amphibolite-facies conditions. Though the Gangdese Mountains may have formed before Indo-Asian collision, the southern margin of Lhasa Terrane might not go through obviously crustal thickening during the northward subduction of Neo-Tethyan oceanic lithosphere.展开更多
Muscovite 40 Ar-39 Ar dating of muscovite-quartz schist, eclogite and retrograde eclogite indicates an Indosinian orogenesis occurred at 220-240 Ma in the Lhasa terrane, which is caused by the closure of Paleo-Tethyan...Muscovite 40 Ar-39 Ar dating of muscovite-quartz schist, eclogite and retrograde eclogite indicates an Indosinian orogenesis occurred at 220-240 Ma in the Lhasa terrane, which is caused by the closure of Paleo-Tethyan ocean basin and the following collision of the northern Lhasa terrane and southern Gondwana land. This Indosinian orogenesis is further confirmed by the regional sedimentary characteristics, magmatic activity and ophiolite mélange. This evidence suggests that the Indosinian orogenic belt in the Lhasa terrane is widely distributed from the Coqen county in the west, and then extends eastward through the Ningzhong and Sumdo area, finally turning around the eastern Himalayan syntaxis into the Bomi county. Based on the evolutionary process, the geological development of Lhasa terrane from early Paleozoic to early Mesozoic can be divided into seven stages. All of the seven stages make up a whole Wilson circle and reveal a perfect evolutionary process of the Paleo-Tethys ocean between the northern Lhasa terrane and southern Gondwana land. The Indosinian orogenisis is a significant event for the evolution of the Lhasa terrane as well as the Tibetan Plateau.展开更多
the India and Eurasia plates. Knowledge of the stress state is critical to evaluate the crustal stability and the design of underground excavations. Because of the limitations imposed by natural conditions, little res...the India and Eurasia plates. Knowledge of the stress state is critical to evaluate the crustal stability and the design of underground excavations. Because of the limitations imposed by natural conditions, little research has been performed on the present crustal in situ stress in the Tibetan Plateau, and further study is imperative. In this study, hydraulic fracturing measurements were conducted in Nyching County （LZX） and Lang County （LX）, Lhasa terrane to characterize the shallow crustal stress state. The results indicate that the stress state in the LZX borehole is markedly different from that in the LX borehole, in both magnitude and orientation. At the same measurement depths, the magnitudes of horizontal principal stresses in the LX borehole are 1.5–3.0 times larger than those in the LZX borehole. The stress regime in the LX borehole favors reverse faulting characterized by SH〉Sh〉Sv, where SH, Sh, and Sv are maximum horizontal, minimum horizontal, and vertical principal stresses, respectively. The SH and Sh values are approximately three and two times greater than Sv. Fracture impression results reveal that SH in the LX borehole are predominantly N–S, while in the LZX borehole the maximum horizontal principal stress is mainly in the NNE-direction. The heterogeneity of the regional stress state might be a result of the population and distribution of local structures and seismic activities. The stress state in the LX borehole has exceeded the critical state of failure equilibrium, and there is an optimally orientated pre-existing fault near the borehole. It can be concluded that the optimally orientated fault is likely to be active when the stress has built up sufficiently to destroy the frictional equilibrium; it is suggested that research focus should be placed on this in future. The stress states in boreholes LZX and LX indicate uniformity of the regional stress field and diversity of the local stress fields resulting from the interactions among regional dynamic forces, tectonic stress field, and geological structures.展开更多
We present n-alkane distributions in the soil samples along a transect from Lhasa on the Tibetan Plateau to Bharatpur in Nepal, which covers a large geographical area and a wide range of climatic conditions. These dat...We present n-alkane distributions in the soil samples along a transect from Lhasa on the Tibetan Plateau to Bharatpur in Nepal, which covers a large geographical area and a wide range of climatic conditions. These data allow us to assess the significance of n-alkane distributions in different vegetation types and their relationships to temperature and precipitation. In the tropical rainforest and broadleaved forest zones, n-alkanes exhibit a bimodal distribution pattern with dominant homologues around n-C_（31） and n-C_（23）. The bimodal distribution of tropical rainforest n-alkanes may be a general pattern because of the presence of many lianas, epiphytic plants, algae and the strong microbial activity and degradation involved in the postdepositional process. In the warm-temperate mixed forest and needle-leaved forest zones, the long-chain alkanes have a pattern of n-C_（31） n-C_（33） n-C_（27）. In the alpine shrub and grassland zone, although the most abundant homologue is n-C_（31） , relatively high n-C_（23） concentrations have also been observed in some samples. The statistical results show a good correlation between n-alkane proxies and climatic factors. The average chain length（ACL） values are positively correlated with precipitation and temperature across the transect. The carbon preference index（CPI） values show a negative correlation with temperature and precipitation along a Lhasa–Bharatpur transect. Although there is a positive relationship between ACL and temperature, it is difficult to separate the two climatic variables（temperature and precipitation） because they are well coupled in the monsoon region.展开更多
Land use change is the result of the interplay between socioeconomic, institutional and environmental factors, and has important impacts on the functioning of socioeconomic and environmental systems with important tra...Land use change is the result of the interplay between socioeconomic, institutional and environmental factors, and has important impacts on the functioning of socioeconomic and environmental systems with important tradeoffs for sustainability, food security, biodiversity and the vulnerability of people and ecosystems to global change impacts. Based on the results of the First Land Use Survey in Tibet Autonomous Region carried out in the late 1980s land use map of Lhasa area in 1990 was compiled for the main agricultural area in Lhasa valley using aerial photos obtained in April, May and October 1991 and Landsat imagery in the late 1980s and 1991 as remotely sensed data sources. Using these remotely sensed data the land use status of Lhasa area in 1991, 1992, 1993, 1995, 1999 and 2000 were mapped through updating annual changes of cultivated land, artificial forest, grass planting, grassland restoration, and residential area and so on. Land use map for Lhasa area in 2007 was made using ALOS AVNIR-2 composite images acquired on October 24 and December 26, 2007 through updating changes of main land use types. According to land use status of Lhasa area in 1990, 1995, 2000 and 2007, the spatial and temporal land use dynamics in Lhasa area from 1990 to 2007 are further analyzed using GIS spatial models in this paper.展开更多
The area of land utilized for growing vegetables in greenhouses has expanded rapidly on the Tibetan Plateau over recent decades. However, the effects of greenhouses on soil fertility as well as variations in these eff...The area of land utilized for growing vegetables in greenhouses has expanded rapidly on the Tibetan Plateau over recent decades. However, the effects of greenhouses on soil fertility as well as variations in these effects between the plateau and plain remain unclear on the Tibetan Plateau. This study assessed the effects of vegetable greenhouses in the vicinity of Lhasa, using open field soil as a control. A total of 92 plough layer(0-20 cm depth) soil samples including 54 from greenhouses and 38 from open fields were taken, and soil pH, electrical conductivity(EC), total soluble salt(TS), soil organic matter(SOM), total nitrogen(TN), available phosphorus(AP), and available potassium(AK) were measured. The results reveal that, soil pH was lower 1.0 units in greenhouses than that in open field. TS was higher 82% and AP was higher 160% overall. Similarly, SOM and TN were higher 32% and 46%, respectively, while AK changed slightly at a higher 1% rate. Results also show that soil properties varied depending on cultivation time and vegetable types. Overall, pH continuously decreased with cultivation time while other soil fertility indicators reached a maximum value after nine years of cultivation before starting to decrease. The effect of leafy vegetable planting on soil was slight overall, while the impact of fruits on soil was more serious. Compared with changes in plain greenhouse soil fertility measured across the eastern China, the effects of greenhouses on soil in Lhasa remain relatively limited;and the change in the degree of soil fertility was lower and the extreme values of soil fertility occurred later in Lhasa.展开更多
基金supported by the Natural Science Foundation of China (No.11775180).
文摘To explore air contamination resulting from special biomass combustion and suspended dust in Lhasa,the present study focused on the size distribution and chemical characteristics of particulate matter(PM)emission resulting from 7 types of non-fossil pollution sources.We investigated the concentration and size distribution of trace elements from 7 pollution sources collected in Lhasa.Combining Lhasa’s atmospheric particulate matter data,enrichment factors(EFs)have been calculated to examine the potential impact of those pollution sources on the atmosphere quality of Lhasa.The highest mass concentration of total elements of biomass combustion appeared at PM_(0.4),and the second highest concentration existed in the size fraction 0.4-1μm;the higher proportion(12%)of toxicmetals was produced by biomass combustion.The elemental composition of suspended dust and atmospheric particulate matter was close(except for As and Cd);the highest concentration of elements was all noted in PM_(2.5-10)(PM_(3-10)).Potassium was found to be one of the main biomass markers.The proportion of Cu in suspended dust is significantly lower than that of atmospheric particulate matter(0.53%and 3.75%),which indicates that there are other anthropogenic sources.The EFs analysis showed that the Cr,Cu,Zn,and Pb produced by biomass combustion were highly enriched(EFs>100)in all particle sizes.The EFs of most trace elements increased with decreasing particle size,indicating the greater influence of humanfactors on smaller particles.
基金jointly supported by the National Key Research&Development Program of China(2021YFC2900100)the Basic Research Fund of the Chinese Academy of Geological Sciences(KK2306)+1 种基金the Geological Survey Project(DD20230360,DD20243483)the Sichuan Provincial Natural Science Foundation(2023NSFSC0798).
文摘Multiple instances of the Late Cretaceous granodiorites within the Anglonggangri region of the northwestern Lhasa Block were identified,their petrogenesis were explored and mineralization potential were assessed.The zircon U-Pb dating of the Anglonggangri granodiorites revealed ages of 82.8 and 80.8 Ma.Granodiorite samples have SiO2 contents of 64.36-68.33 wt%,with high Sr/Y(55-95)and A/CNK ratios(0.99-1.06).Zirconε_(Hf)(t)values range from−0.3 to+16.2.Two granodiorite samples have(^(87)Sr/^(86)Sr)i values of 0.7034 and 0.7043 and positiveɛNd(t)values of 3.51 and 3.83.These geochemical properties indicate that they are adakitic rocks formed by partial melting of the juvenile thickened lower crust,slightly contaminated with material from the mantle due to the small-scale delamination of the lower crust.The zircons in the granodiorites have moderate Ce/Nd(2.5-43),logfO2(−20.0 to−9.6),andΔFMQ(−1.28 to+4.00)values;low(Ce/Nd)/Y(0.001-0.049)ratios;and high Dy/Yb(0.17-1.16)ratios,which indicate that these granodiorites exhibit moderate oxygen fugacity and lower magma water content than the Miocene Gangdese porphyry copper deposits associated with high-Sr/Y granites.Their ability to create porphyry-type copper deposits could have been hampered by their low magma water content and moderate oxygen fugacity.
基金supported by the National Natural Science Foundation of China[Grants.41802054]supported by a Royal Society SinoBritish Fellowship Trust International Exchanges Award[Grant No.IESR3213093]。
文摘The high Ba-Sr rocks can provide significant clues about the evolution of the continent lithosphere,but their petrogenesis remains controversial.Identifying the Late Cretaceous high Ba-Sr granodiorites in the SE Lhasa Block could potentially provide valuable insights into the continent evolution of the Qinghai-Tibet Plateau.Zircon U-Pb ages suggest that the granodiorites were emplaced at 87.32±0.43 Ma.Geochemically,the high Ba-Sr granodiorites are characterized by elevated K_(2)O+Na_(2)O contents(8.18-8.73 wt%)and K_(2)O/Na_(2)O ratios(0.99-1.25,mostly>1),and belong to high-K calc-alkaline to shoshonitic series.The Yonglaga granodiorites show notably high Sr(653-783 ppm)and Ba(1346-1531 ppm)contents,plus high Sr/Y(30.92-38.18)and(La/Yb)_(N)(27.7-34.7)ratios,but low Y(20.0-22.8 ppm)and Yb(1.92-2.19 ppm)contents with absence of negative Eu anomalies(δEu=0.83-0.88),all similar to typical high Ba-Sr granitoids.The variable zirconεHf(t)values of-4.58 to+12.97,elevated initial^(87)Sr/^(86)Sr isotopic ratios of 0.707254 to 0.707322 and lowεNd(t)values of-2.8 to-3.6 with decoupling from the Hf system suggest that a metasomatized mantle source included significant recycled ancient materials.The occurrence of such high Ba-Sr intrusions indicates previous contributions of metasomatized mantle-derived juvenile material to the continents,which imply the growth of continental crust during the Late Cretaceous in the SE Lhasa.Together with regional data,we infer that the underplated mafic magma provides a significant amount of heat,which leads to partial melting of the juvenile crust.The melting of the metasomatized mantle could produce a juvenile mafic lower crust,from which the high Ba-Sr granitoids were derived from reworking of previous mafic crust during the Late Cretaceous(ca.100-80 Ma)in the SE Lhasa.
文摘Lhasa,a city rich in history,is often celebrated as a fertile ground for the flourishing of museums.Among the museums in Lhasa,some chronicle the region's profound historical roots,some explore the wonders of nature,some preserve vibrant cultural heritage,and others capture the rhythms of everyday life.
文摘On April 30,the 22nd China Xiza ng Mountai neering Conventi on in 2025 comme need.As its flagship eve nt,the Luodui Peak Mountaineering Expedition took place from May 2 to 3 in Yangbajain Town of Lhasa,attracting more than 160 mountain climbing enthusiasts from all over the country.
基金the National Key Research and Development Program of China(Grant No.2022YFF0800903)the National Natural Science Foundation of China(Grant Nos.42302107,92162322,42261144669,41922022,42003036)+4 种基金the China Geological Survey(Grant Nos.DD20243512,DD20230008)the National Postdoctoral Research Program of China(Grant No.GZC20232489)the Second Tibetan Plateau Scientific Expedition and Research(Grant No.2021QZKK0304)Xing Dian Youth Talent Plan of Yunnan Province(Grant No.XDYC-QNRC-2022-0136)the UNESCO:IUGS IGCP-662 Program。
文摘Basalts from the Late Carboniferous to Early Permian are extensively developed in the central Lhasa subterrane,southern Xizang.Studying the petrogenesis of these rocks may have implications for the late Paleozoic arc magmatism along the central Lhasa subterrane uncovering more of the evolution of the Sumdo Paleo-Tethys Ocean and its dynamic mechanism.Basalt samples from the Luobadui Formation in the Leqingla area,NW of Linzhou City in the central Lhasa subterrane,southern Xizang exhibit arc-like geochemical signatures in a subduction-zone tectonic setting characterized by high Al_(2)O_(3)and low TiO_(2)contents,fractionated REE patterns with low Nb/La ratios and high LREE concentrations,and negative HFSE anomalies.Based on their higher Th/Ce,Nb/Zr,and lower Ba/Th,Pb/Nd ratios,slightly negative to positiveε_(Nd)(t)values,and the relatively high Sr-Pb isotopic compositions,these samples were probably derived from partial melting of a depleted mantle source of garnet+spinel lherzolite,metasomatized by subducted sediments around 297 Ma.Modeling of the trace elements indicates that these basalts experienced fractional crystallization of olivine,clinopyroxene and minor plagioclase during magma ascent and eruption.It is proposed that these Late Carboniferous–Early Permian basalts are associated with the northward subduction of the Sumdo Paleo-Tethys Ocean seafloor along the southern margin of the central Lhasa subterrane.
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Supported by National Natural Science Foundation of China(41065001)~~
文摘The variation characteristics of ozone in Lhasa in recent years were analyzed by using Brewer spectrometer observation data. The results showed that ozone was mainly distributed in 15-35 km in atmosphere in Lhasa; the peak value by inversion was in 21-25 km; by comparison of ozone vertical distribution in Lhasa, it can be concluded that ozone differs insignificantly in middle-to-high layers in stratosphere and the distribution is similar over 36 km. The difference can be observed from the fact that ozone concentration is higher in winter and spring compared with summer and autumn from ground to the height at 21 km. In recent 4 years, annual average of total ozone in Lhasa was of little variations and extreme values of ozone appeared in winter and spring. Monthly averages were lower in August and September, and the lower value of ozone kept longer in 2008 for 23 d.
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.
文摘A huge thrust system, the North Lhasa Thrust (NLT), was discovered in the northern Lhasa block of the Tibetan Plateau based on geological mapping of the Damxung region and its vicinity, the Deqen-Lunpola traverse and the Amdo-Bam Co profile. The NLT consists of the Dongqiao-Lunpola thrust (DLT), the west Namco thrust (WNT) and the south Damxung thrust (SDT) and ductile shear zones, ophiolite slices and folds extending in a WNW direction. Major thrust faults of the NLT seem to merge into a single deep-seated detachment of the upper-crust and totally displaced southward as far as 100-120 km. Chronological analyses with 39Ar-40Ar of plagioclase and hornblende, Rb-Sr isochron of minerals and fission-tracks of apatite from mylonite within the WNT yield ages of 174-173 Ma, 109 Ma and 44 Ma, showing 3 periods of thrusting in the north Lhasa block caused by subduction of the Tethys oceanic plate and the India-Eurasia continental collision respectively.
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supported by China Geological Survey (Nos. 1212010610107 and 1212010610105)the Institute of Geology, Chinese Academy of Geological Sciences (No. J0701)
文摘Recently, an over 100 km long MORB-type eclogite belt of Permian was discovered in the Sumdo （松多） region of the Lhasa block, Tibet. A critical question thus is： what is the tectonic setting of the eelogite belt and is it related to an unrecognized suture in the region？ Further investigations show that there are some mafic and ultramafic rocks spacially associated with the eclogite belt in the region. Three ultramafic massifs were recognized in the Sumdo region, and called the Luomaling （罗马岭）, Gongbupala （贡布爬拉） and Qiazhasumdo （卡扎松多） massifs. All the massifs are fault-contacted with greenschist （Chasagang （岔萨岗） Formation） or muscovite-quartz schist （Mabuku （马布库） Formation）, and individuals are about 100 m×50 m in size extending in EW as the regional structure. All the ultramafic rocks have been entirely serpentinized, and the Gongbupala massif has been selected for study in geochemistry. Eleven chemical analyses of the rocks from the Gongbupala massif show a narrow range in contents： SiO2 （35.97-40.63） wt.%, MgO （37.02-38.60） wt.%, TiO2 （0.01-0.08） wt.%, Al2O3 （0.80-1.64） wt.%, （Na2O＋K2O） less than 0.1 wt.%, with high volatile contents （H2O＋CO2） （11.24-14.91） wt.%. After recalculation without H2O＋CO2, the mean values are SiO2 45.24 wt.%, MgO 43.54 wt.%, FeOT （7.45-9.97） wt.% （8.55 wt.% in average）, （MgO＋FeOT） 52.09 wt.%, Mg# （100×Mg/（Mg＋Fe＊）, where Fe＊ represents total Fe）=89.42-90.08, （m＋f）/Si （（atomicity Mg＋atomicity Fe） /atomicity Si）=1.53-1.75 （1.59 in average）, respectively. The mean M/F （atomicity Mg/atomicity Fe） ratio of the rocks is 9.05, which is classified as magnesium enriched-type of ultramafic rocks. The compositional features, depleted in K, Na, Ca, AI and Ti and enriched in Mg#, indicate the characteristics of peridotite originated from a depleted mantle. The rocks have low REE with ∑（1.60-2.68）×10^-6 similar to those of the primitive mantle. The chondrite-normalized REE patterns of all samples show slightly enrichment in LREE, with （Ce/Yb）N 1.03-2.46, but a little depleted in HREE. Most samples show a slight negative anomaly in Eu, a feature in REE from a relic mantle and common features in highly serpentinized ultramafic rocks in the Yarlung-Zangbo （雅鲁藏布） ophiolite and the Bangong （班公）-Nujiang （怒江） ophiolite in Tibet. The primitive mantle-normalized spiderdiagram of trace elements for Gongbupala ultramafic rocks yields uniform distributed pattern. They are relatively enriched in Rb, Ba, La, P element （LHSE） and depleted in Sm, Ti, Y, Yb element （HFSE）, a feature of metasomatic mantle peridotite. The geochemical features of the rocks suggest that the protolith of Gongbupala serpentinite in Sumdo region is harzburgite, a typical depleted mantle rock, and may represent a dismembered ophiolite unit in the region.
基金Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20040401)。
文摘Based on a total of 519 images,the composite images with the lowest possible cloud cover were generated at pixel level with image synthesis method on Google Earth Engine(GEE)platform.The Remote Sensing Ecological Index(RSEI)was adopted,and calculated in an efficient way with the assistance of parallel cloud computing of the GEE platform.The RSEI was used in this paper to evaluate and monitor the eco-environmental quality of the Lhasa Metropolitan Area.Results show that:(1)The ecological quality is better in the west than in the east of Lhasa Metropolitan Area,with Lhasa as an approximate dividing point.The ecological quality improved and then deteriorated dramatically before 2000,with the mean RSEI value dropping from 0.51 to 0.46;the trend was followed by a gradual increase up until 2017,with the mean RSEI value increased from 0.46 to 0.55.(2)The RSEI is weakly and positively correlated with socioeconomic indicators.This indicates that the population growth and economic development did not negatively influence the ecological quality,but actually boosted it.(3)The GEE can serve as an efficient computing platform for the assessment and monitoring of eco-environmental quality in vast regions.
基金funded by grants from the National Natural Science Foundation of China (No.40930313)the China Geological Survey (No.12120114057701,No.12120114061801 and No.12120114061501)
文摘The southern Lhasa Terrane is famous for its huge magmatic belt which records the magmatism during Mesozoic and Cenozoic. Although the Mesozoic continental-margin setting in the southern Lhasa Terrane has been identified, details of this tectonic setting and the evolution history during the Late Cretaceous remain unclear. To further constrain these issues, we present zircon LA-ICP-MS U-Pb, Hf isotopic and geochemical data of the Gongbari dacites （of the Sangri Group） which intruded by Paleocene granodiorites from the eastern part of the southern Lhasa Terrane, Tibet. New age data indicate that the dacites were generated at -95.4 Ma, which suggests the Sangri Group volcanism may last to Late Cretaceous. The Gongbari dacites are characterized by high Sr （428-758 ppm） contents, low concentration of heavy rare earth elements and Y （e.g. Yb=0.78-1.14 ppm; Y=8.85-11.4 ppm） with high Sr/Y （41.91-67.59） and La/Yb （22.64-30.64） ratios, similar to those of adakite. The rocks are calc-alkaline, metaluminous, enriched in LILEs, depleted in HFSEs, and have positive tar（t） values （＋7.7 to ＋11.6）. The Gongbari dacites were probably produced by partial melting of young and hot subducted Neo- Tethyan oceanic crust under amphibolite to garnet amphibolite-facies conditions. Though the Gangdese Mountains may have formed before Indo-Asian collision, the southern margin of Lhasa Terrane might not go through obviously crustal thickening during the northward subduction of Neo-Tethyan oceanic lithosphere.
基金Financial support was provided by Geological Survey Program of China Geological Survey (Grant No. 1212010610105)the Basic Foundation of Institute of Geology, Chinese Academy of Geological Sciences (Grant No. J0918)
文摘Muscovite 40 Ar-39 Ar dating of muscovite-quartz schist, eclogite and retrograde eclogite indicates an Indosinian orogenesis occurred at 220-240 Ma in the Lhasa terrane, which is caused by the closure of Paleo-Tethyan ocean basin and the following collision of the northern Lhasa terrane and southern Gondwana land. This Indosinian orogenesis is further confirmed by the regional sedimentary characteristics, magmatic activity and ophiolite mélange. This evidence suggests that the Indosinian orogenic belt in the Lhasa terrane is widely distributed from the Coqen county in the west, and then extends eastward through the Ningzhong and Sumdo area, finally turning around the eastern Himalayan syntaxis into the Bomi county. Based on the evolutionary process, the geological development of Lhasa terrane from early Paleozoic to early Mesozoic can be divided into seven stages. All of the seven stages make up a whole Wilson circle and reveal a perfect evolutionary process of the Paleo-Tethys ocean between the northern Lhasa terrane and southern Gondwana land. The Indosinian orogenisis is a significant event for the evolution of the Lhasa terrane as well as the Tibetan Plateau.
基金supported by the China Geological Survey Project(No.12120113038000)the National Science and Technology Major Project(2016ZX05034-003-2)the scientific research plan of the China Railway Eryuan Engineering Group CO.LTD(No.13164007)
文摘the India and Eurasia plates. Knowledge of the stress state is critical to evaluate the crustal stability and the design of underground excavations. Because of the limitations imposed by natural conditions, little research has been performed on the present crustal in situ stress in the Tibetan Plateau, and further study is imperative. In this study, hydraulic fracturing measurements were conducted in Nyching County （LZX） and Lang County （LX）, Lhasa terrane to characterize the shallow crustal stress state. The results indicate that the stress state in the LZX borehole is markedly different from that in the LX borehole, in both magnitude and orientation. At the same measurement depths, the magnitudes of horizontal principal stresses in the LX borehole are 1.5–3.0 times larger than those in the LZX borehole. The stress regime in the LX borehole favors reverse faulting characterized by SH〉Sh〉Sv, where SH, Sh, and Sv are maximum horizontal, minimum horizontal, and vertical principal stresses, respectively. The SH and Sh values are approximately three and two times greater than Sv. Fracture impression results reveal that SH in the LX borehole are predominantly N–S, while in the LZX borehole the maximum horizontal principal stress is mainly in the NNE-direction. The heterogeneity of the regional stress state might be a result of the population and distribution of local structures and seismic activities. The stress state in the LX borehole has exceeded the critical state of failure equilibrium, and there is an optimally orientated pre-existing fault near the borehole. It can be concluded that the optimally orientated fault is likely to be active when the stress has built up sufficiently to destroy the frictional equilibrium; it is suggested that research focus should be placed on this in future. The stress states in boreholes LZX and LX indicate uniformity of the regional stress field and diversity of the local stress fields resulting from the interactions among regional dynamic forces, tectonic stress field, and geological structures.
基金supported by the National Natural Science Foundation of China(Grant nos.41302141 and 41272198)the Geological Research Program of China Geological Survey(No.12120113015400)
文摘We present n-alkane distributions in the soil samples along a transect from Lhasa on the Tibetan Plateau to Bharatpur in Nepal, which covers a large geographical area and a wide range of climatic conditions. These data allow us to assess the significance of n-alkane distributions in different vegetation types and their relationships to temperature and precipitation. In the tropical rainforest and broadleaved forest zones, n-alkanes exhibit a bimodal distribution pattern with dominant homologues around n-C_（31） and n-C_（23）. The bimodal distribution of tropical rainforest n-alkanes may be a general pattern because of the presence of many lianas, epiphytic plants, algae and the strong microbial activity and degradation involved in the postdepositional process. In the warm-temperate mixed forest and needle-leaved forest zones, the long-chain alkanes have a pattern of n-C_（31） n-C_（33） n-C_（27）. In the alpine shrub and grassland zone, although the most abundant homologue is n-C_（31） , relatively high n-C_（23） concentrations have also been observed in some samples. The statistical results show a good correlation between n-alkane proxies and climatic factors. The average chain length（ACL） values are positively correlated with precipitation and temperature across the transect. The carbon preference index（CPI） values show a negative correlation with temperature and precipitation along a Lhasa–Bharatpur transect. Although there is a positive relationship between ACL and temperature, it is difficult to separate the two climatic variables（temperature and precipitation） because they are well coupled in the monsoon region.
基金National Key Technology Research and Development Program, No.2007BAC06B08 National Basic Research Program of China, No.2010CB951704 National Natural Science Foundation of China, No.40361001 Acknowledgements The authors would like to thank Prof. Zheng Du of Institute of Geographic Sciences and Natural Resources Research, CAS for the guidance and thoughtful suggestions about this study, Zhang Zengxiang, Wang Changyou, Zhao Xiaoli, Liu Bin, Peng Xulong of Institute of Remote Sensing Applications of CAS and Bian Duo, Li Lin, Yang Zhigang, Pubu Yangjin of Tibet Remote Sensing Center for field investigations and land use mapping during implementing project ＂the integrated environmental assessment and monitoring in the central Tibetan Plateau using GIS and remote sensing＂. We are grateful to Dr. Yan Jianzhong of Southwest University in China and reviewers for their thoughtful opinions of this manuscript.
文摘Land use change is the result of the interplay between socioeconomic, institutional and environmental factors, and has important impacts on the functioning of socioeconomic and environmental systems with important tradeoffs for sustainability, food security, biodiversity and the vulnerability of people and ecosystems to global change impacts. Based on the results of the First Land Use Survey in Tibet Autonomous Region carried out in the late 1980s land use map of Lhasa area in 1990 was compiled for the main agricultural area in Lhasa valley using aerial photos obtained in April, May and October 1991 and Landsat imagery in the late 1980s and 1991 as remotely sensed data sources. Using these remotely sensed data the land use status of Lhasa area in 1991, 1992, 1993, 1995, 1999 and 2000 were mapped through updating annual changes of cultivated land, artificial forest, grass planting, grassland restoration, and residential area and so on. Land use map for Lhasa area in 2007 was made using ALOS AVNIR-2 composite images acquired on October 24 and December 26, 2007 through updating changes of main land use types. According to land use status of Lhasa area in 1990, 1995, 2000 and 2007, the spatial and temporal land use dynamics in Lhasa area from 1990 to 2007 are further analyzed using GIS spatial models in this paper.
基金Under the auspices of the Second Tibetan Plateau Scientific Expedition and Research(No.2019QZKK0600)National Natural Science Foundation of China(No.41771113)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA20040201)。
文摘The area of land utilized for growing vegetables in greenhouses has expanded rapidly on the Tibetan Plateau over recent decades. However, the effects of greenhouses on soil fertility as well as variations in these effects between the plateau and plain remain unclear on the Tibetan Plateau. This study assessed the effects of vegetable greenhouses in the vicinity of Lhasa, using open field soil as a control. A total of 92 plough layer(0-20 cm depth) soil samples including 54 from greenhouses and 38 from open fields were taken, and soil pH, electrical conductivity(EC), total soluble salt(TS), soil organic matter(SOM), total nitrogen(TN), available phosphorus(AP), and available potassium(AK) were measured. The results reveal that, soil pH was lower 1.0 units in greenhouses than that in open field. TS was higher 82% and AP was higher 160% overall. Similarly, SOM and TN were higher 32% and 46%, respectively, while AK changed slightly at a higher 1% rate. Results also show that soil properties varied depending on cultivation time and vegetable types. Overall, pH continuously decreased with cultivation time while other soil fertility indicators reached a maximum value after nine years of cultivation before starting to decrease. The effect of leafy vegetable planting on soil was slight overall, while the impact of fruits on soil was more serious. Compared with changes in plain greenhouse soil fertility measured across the eastern China, the effects of greenhouses on soil in Lhasa remain relatively limited;and the change in the degree of soil fertility was lower and the extreme values of soil fertility occurred later in Lhasa.
