Discovery of Ophiolitic Mélange in the North Region of Geji County, Northwest Tibet and Its Zircon U-Pb Age

Objective The Bangong Co–Nujiang River suture zone is the great boundary between the Lhasa and Qiangtang terranes in the Tibetan Plateau.A series of major scientific issues are still controversial at present such as the subduction polarity and evolutionary process of this suture（Wei Shaogang et al.,2017）.

Sap Flow of Abies georgei var. smithii and Its Relationship with the Environment Factors in the Tibetan Subalpine Region, China

Abies georgei var. smithii is a dominant species playing an important role in protecting biodiversity and sustaining the forestry ecosystems in Southeastern Tibetan Plateau. Stem sap flows of five different diameters at the breast height(DBH) A. georgei var. smithii samples were monitored continuously with the thermal dissipation probe for the entire growing period in order to understand the water transportation mechanism and the effects of environmental factors on its transpiration and growth. Relative environment factors, temperature and humidity of air, photosynthetically active radiation, rainfall, and wind speed, soil moisture, etc. were measured by the automatic weather stations. Diurnal and seasonal variations in sap flow rate with the different stem diameters and their correlations with meteorological factors were analyzed. The diurnal change in sap flow velocity showed a single-peak curve at the daily time scale, whereas a lower sap flow velocity can be observed in the largest DBH sample tree at night. The maximum average velocity was observed in August, whereas the minimum velocity was observed in January, and a large amount of water evaporated in summer owing to the higher sap flow velocity. In addition, sap flow velocity was closely related to changes in the micrometeorological factors, with average sap flow velocity showing significant linear correlations with air temperature, photosynthetically active radiation, rainfall, and vapor pressure deficit of air and soil moisture. Therefore, some measures, improving the light and temperature conditions, should be taken for protecting A. georgei var. smithii population in the Tibetan Plateau.

Reconstruction of the Triassic Tectonic Lithofacies Paleogeography in Qiangtang Region, Northern Qinghai-Tibet Plateau, China

The Triassic petrostratigraphic system and chronologic stratigraphic sketch have been updated and perfected in the Qiangtang area, Qinghai-Tibet Plateau based on the integrated 1：250000 regional geological survey and the latest research progeny. The first finished 1：3000000 Triassic tectonic lithofacies paleogeographic maps in the Qiangtang area shows that the Triassic tectonic unit in the Qiangtang area can been divided into three parts from north to south： northern Qiangtang block; Longmucuo-Shuanghu suture zone; and southern Qiangtang block. The early-middle Triassic tectonic paleogeography in the Qiangtang area is divides into three sub- units： northern Qiangtang passive continental marginal basin （NQPB）, Longmucuo- Shuanghu residual basin （LSRB） and southern Qiangtang residual basin （SQRB）. The NQPB can be subdivided into four paleogeography units： The Tanggula-Zangxiahe shallow and bathyal sea; The Wangquanhe- Yingshuiquan carbonate platform; The Rejuechaka-Jiangaidarina littoral- shallow sea; and Qiangtang central uplift. The above units of The NQPB possess EW trend, geomorphology high in the south and low in the north, the seawater depth northward. The basinal paleo-current direction is unidirectional, and basinal tectonic subsidence center is in accord with the depo-center, located in the Tanggula-Zangxiahe belt, north of the basin. The sedimentation and tectonic evolution of the NQPB are characterized with passive continental marginal basin. The Qiangtang central orogenic denuded area （ancient land） may be as a sedimentary materials source of the NQPB. SQRB can be divided into two units： Duoma carbonate platform and southern Qiangtang neritic-deep sea. The late Triassic tectonic paleogeography in the Qiangtang area is the framework of the ＂archipelagic-sea＂ as a whole, and it may be divided into three sub-units： northern Qiangtang back- arc foreland basin（NQFB）, Longmucuo-Shuanghu residual basin（LSRB） and southern Qiangtang marginal-sea basin（SQMB）. Thereinto, NQFB can be divided into five paleogeography units： the Zangxiahe-Mingjinghu bathyal basin characterized with the flysch; the Tanggula shallow-sea shelf with the fine-clastics; the Juhuashang platform with carbonates; the Tumenggela-Shuanghu coastal- delta with coal-bearing clastics and the Nadigangri- Geladandong arc with volcanics and tuffs. In transverse section, the NQFB fills is wedge-shaped, and the sediments characterized with thicker in north and thinner in south, and with double materials derived from the Ruolagangri orogenic belt in north and the Shuanghu central orogenic belt in south. The late Triassic depocenter of NQFB is located in the middle of the basin, the Yakecuo-Bandaohu-Quemocuo belt, but the subsidence center in the north, the Zangxiahe- Mingjinghu belt, and basinal tectonic subsidence center not concordant with the depo-center. Late Triassic, the SQMB may be divided into three sub-units： Xiaochaka shallow-sea; Riganpeicuo platform~ and South Qiangtang southern bathyal basin. In transverse section, the basement of the SQMB is characterized with low in the northern and southern, but high in the middle; forming wedge shaped sediments with thicker in the north and thinner in the south; the sedimentary materials derived from the Qiangtang central uplift and Nadigangri arcs in north. The late Triassic subsidence centre of the SQMB is located in the northern （Xiaochaka area）, but the depocenter in the southern （Qixiancuo Suobucha area）. The sedimentation and tectonic evolution of the SQMB are characterized with marginal sea.

Analysis on the Status of Farmers, Agriculture and Countryside, and Development Strategies and Measures in Tibet Autonomous Region

Coordinated and sustainable development of farmers, agriculture and countryside (FAC) is key to realize the national objective of comprehensively developed well-off society. Since the peaceful liberation of Tibet, outstanding achievements have been made in FAC work. However, compared with East and Middle China, there still exists a big gap. The farmers’ net income per capita in 2001 was 1,404 yuan, 962 yuan lower than the nation’s average. In late 90’s the farmers’ income growth slowed down. Agricultural industrialization is at low level, technologies play a small role in agricultural development, rural infrastructure is weak, the rural grass root organization is much underdeveloped, and construction of towns is behind the other regions of China. Based on the problems of FAC development there, this paper proposes FAC development strategies and measures for accelerating rural development in Tibet.

Soil Taxonomy and Distribution Characteristics of the Permafrost Region in the Qinghai-Tibet Plateau, China

Understanding the soil taxonomy and distribution characteristics of the permafrost region in the Qinghai-Tibet Plateau(QTP) is very important. On the basis of extensive field surveys and experimental analysis, this study carries out soil taxonomic classification of the permafrost region in the QTP. According to Chinese Soil Taxonomy, the soil of the permafrost region in the QTP can be divided into 6 Orders(Histosols, Aridosols, Gleyosols, Isohumosols, Cambosols, Primosols), 11 Suborders, 19 Groups and 24 Subgroups. Cambosols are the dominant soil type in the permafrost region, followed by Aridosols. From the east to the west of the permafrost region in the QTP, the soil type gradually changes from Cambosols to Aridosols, showing a meridional zonality. The eastern region is dominated by Cambosols, with no obvious latitudinal zonality. From the south to the northwest of the western region, the dominance of Aridosols and Cambosols gradually transited to Aridosols, presenting a latitudinal zonality. The soil in the western region shows a poor vertical zonality, while the distribution of suborders of Cambosols in the eastern region shows a more obvious vertical zonality. The result indicates that precipitation and vegetation are the main factors that influence the zonal distribution of soil. The permafrost in the east has some effect on the vertical soil zonality, but the effect is weakened in the west.

Early Permian–Late Triassic Magmatism in the Tuotuohe Region of the Qinghai–Tibet Plateau: Constraints on the Tectonic evolution of the Western Segment of the Jinshajiang Suture

In this paper we present new zircon U-Pb ages,whole-rock major and trace element analyses,and zircon Hf isotopic data for magmatic rocks in the Tuotuohe region of the western segment of the Jinshajiang suture.Our aim is to constrain the Early Permian-Late Triassic tectonic evolution of the region.Zircons from the magmatic rocks of the Tuotuohe region are euhedralsubhedral in shape and display fine-scale oscillatory zoning as well as high Th/U ratios （0.4-4.6）,indicating a magmatic origin.The zircon U-Pb ages obtained using LA-ICP-MS are 281 ± 1 Ma,258 ± 1 Ma,244 ± 1 Ma,and 216 ± 1 Ma,which indicate magmatism in the Early Permian-Late Triassic.A diorite from Bashihubei （BSHN） has SiO2 =57.18-59.97 wt％,Al2O3=15.70-16.53 wt％,and total alkalis （Na2O ＋ K2O） =4.46-6.34 wt％,typical of calc-alkaline and metaluminous series.A gabbro from Bashibadaoban （BSBDB） belongs to the alkaline series,and is poor in SiO2 （45.46-54.03 wt％） but rich in Al2O3 （16.19-17.39 wt％） and total alkalis （Na2O ＋ K2O =5.48-6.26 wt％）.The BSHN diorite and the BSBDB gabbro both display an enrichment of LREEs and LILEs and depletion of HFSEs,and they have no obvious Eu anomaly; they have relatively low MgO contents （2.54-4.93 wt％）,Mg# values of 43 to 52,and low Cr and Ni contents （8.07-33.6 ppm and 4.41-14.2 ppm,respectively）,indicating they differentiated from primitive mantle magmas.They have low Nb/U,Ta/ U,and Ce/Pb ratios （1.3-9.6,0.2-0.8,and 0.1-18.1,respectively）,and their initial Hf isotopic ratios range from ＋9.6 to ＋16.9 （BSHN diorite） and ＋6.5 to ＋12.6 （BSBDB gabbro）,suggesting their primary magmas were derived mainly from the partial melting of a mantle wedge that had been metasomatized by subduction fluids.Taking all the new data together,we conclude that the western and eastern segment of the Jinshajiang suture regions underwent identical processes of evolution in the Early Permian-Late Triassic：oceanic crust subduction before the Early Permian,continental collision during the Early-Middle Triassic,and post-collisional extension from the Late Triassic.

Joint Inversion of the 3D P Wave Velocity Structure of the Crust and Upper Mantle under the Southeastern Margin of the Tibetan Plateau Using Regional Earthquake and Teleseismic Data

The special seismic tectonic environment and frequent seismicity in the southeastern margin of the Qinghai-Tibet Plateau show that this area is an ideal location to study the present tectonic movement and background of strong earthquakes in China's Mainland and to predict future strong earthquake risk zones. Studies of the structural environment and physical characteristics of the deep structure in this area are helpful to explore deep dynamic effects and deformation field characteristics, to strengthen our understanding of the roles of anisotropy and tectonic deformation and to study the deep tectonic background of the seismic origin of the block＇s interior. In this paper, the three-dimensional （3D） P-wave velocity structure of the crust and upper mantle under the southeastern margin of the Qinghai-Tibet Plateau is obtained via observational data from 224 permanent seismic stations in the regional digital seismic network of Yunnan and Sichuan Provinces and from 356 mobile China seismic arrays in the southern section of the north-south seismic belt using a joint inversion method of the regional earthquake and teleseismic data. The results indicate that the spatial distribution of the P-wave velocity anomalies in the shallow upper crust is closely related to the surface geological structure, terrain and lithology. Baoxing and Kangding, with their basic volcanic rocks and volcanic clastic rocks, present obvious high-velocity anomalies. The Chengdu Basin shows low-velocity anomalies associated with the Quaternary sediments. The Xichang Mesozoic Basin and the Butuo Basin are characterised by low- velocity anomalies related to very thick sedimentary layers. The upper and middle crust beneath the Chuan-Dian and Songpan-Ganzi Blocks has apparent lateral heterogeneities, including low-velocity zones of different sizes. There is a large range of low-velocity layers in the Songpan-Ganzi Block and the sub-block northwest of Sichuan Province, showing that the middle and lower crust is relatively weak. The Sichuan Basin, which is located in the western margin of the Yangtze platform, shows high-velocity characteristics. The results also reveal that there are continuous low-velocity layer distributions in the middle and lower crust of the Daliangshan Block and that the distribution direction of the low-velocity anomaly is nearly SN, which is consistent with the trend of the Daliangshan fault. The existence of the low-velocity layer in the crust also provides a deep source for the deep dynamic deformation and seismic activity of the Daliangshan Block and its boundary faults. The results of the 3D P-wave velocity structure show that an anomalous distribution of high-density, strong-magnetic and high-wave velocity exists inside the crust in the Panxi region. This is likely related to late Paleozoic mantle plume activity that led to a large number of mafic and ultra-mafic intrusions into the crust. In the crustal doming process, the massive intrusion of mantle-derived material enhanced the mechanical strength of the crustal medium. The P-wave velocity structure also revealed that the upper mantle contains a low-velocity layer at a depth of 80-120 km in the Panxi region. The existence of deep faults in the Panxi region, which provide conditions for transporting mantle thermal material into the crust, is the deep tectonic background for the area＇s strong earthquake activity.

Analysis of the Cooling Mechanism of a Crushed Rock Embankment in Warm and Lower Temperature Permafrost Regions along the Qinghai-Tibet Railway

Based on data monitored in situ and theoretical analysis,the characteristics of the temperature field and mechanism of thermal conduction of a crushed rock embankment were studied along the Qinghai-Tibet Railway.The results of experi-ments in the field revealed that the cooling effect of a crushed rock embankment is influenced mainly by the natural con-vection in winter and shield effect in summer,the ventilation of crushed rocks,and the ground temperature regime be-neath the embankment.Consequently,these three factors should be taken into account in numerical simulations,but it is as a result of natural convection only.

Dynamic Changes of the Farmers and Herdsmen’s Income Sources in the Tibet Autonomous Region

Based on the Tibet Autonomous Region's statistic yearbooks and the data fromthe two household surveys in 2002 and 2004, this paper has comprehensively analyzed the pattern ofchanges on the farmers and herdsmen's income sources in the Tibet Autonomous Region since 1990 withthe main findings as follows; (1) The change of income from the labor payment is the fastest; (2)There is no regular pattern of income variation for the household economic activities, the farmersand herdsmen's household incomegeneration projects are impacted by the elements like prices andreturns, and there is a lack of appropriate direction; (3) The income structure of labor paymentshows that the income from the farmers and herdsmen working outside grows fastest; (4) The incomefrom the farmers and herdsmen's labor payment correlate positively to their net income per capita;(5) From the perspective of the variation by region, labor payment income has changed fastest in thecounties of Rutok, Nyerong and Khangmar comparedthe data from the household survey in 2002 withthat of 2004.

Analysis of Income Structure of Farmer (Herdsman) of the Tibet Autonomous Region

Based on the sampling data this paper analyzes income structure of farmer (herdsman) of the Tibet Autonomous Region, including source, characteristics and cash. Situation of income structures and income sources of the farmers in different areas (agricultural, animal husbandry areas and half agricultural and half animal husbandry areas etc. ) was approached. The following features were found through an analysis of surveyed data: (1) In Tibetan peasant household goods and products instead of money. disposable income and cash are very little. (2) The variety index of income is higher in the out skirt than it in rural, the index has a direct bearing on net income. (3) The income ways are simplistic and out-date in the poor households, they have no ability to resist and guard a-gainst any risk, it is very difficult to increase their receipts. (4) The living standard in agricultural areas is better than in pastoral areas, it is the worst in half agriculture and half animal husbandry areas.

Status and Protection of National Wetland Parks in the Tibet Autonomous Region

This paper summarized the status, the brief history of the construction and development of national wetland parks in the Tibet Autonomous Region, and proposed corresponding measures for their later protection and development, in order to realize the sustainable development of national wetland parks.

Investigation and Analysis on the Management Standard of Blood Glucose Monitoring for Clinical Nurses in Nyingchi Region of Tibet

Background: In participating in the medical support work in the Nyingchi area of Tibet, the author found that the medical education resources in this area are scarce, and the clinical nurses in this area have relatively insufficient knowledge about blood glucose monitoring and management. Accurately understanding the knowledge-attitude/belief-practice (KAP) level of nurses in Nyingchi area on blood glucose management is of great significance to the development of blood glucose monitoring management guidance for nurses in this area. Therefore, this study investigated the current status of the management of blood glucose monitoring management standards for clinical nurses in Nyingchi, Tibet. Objective: To investigate and analyze the current situation of clinical nurses in Nyingchi region of Tibet to grasp the regulation of blood glucose monitoring and guide the implementation of the norm of blood glucose monitoring for clinical nurses. Methods: The research survey was carried out from March to April 2020. Random sampling method was used to select 134 clinical in-service nurses in Nyingchii, Tibet. The self-designed knowledge-attitude/belief-practice survey questionnaire for clinical nurses’ blood glucose monitoring and management in Tibet was used. Nurses’ blood glucose monitoring management “KAP” scores and related influencing factors are analyzed. Results: Blood sugar monitoring and management knowledge score is (36.78 ± 6.80), attitude dimension is (42.48 ± 6.42), practice dimension is (61.87 ± 10.24) and total score is (304.73 ± 36.24). The nurse’s department and whether to participate in diabetes training are the main influencing factors of the blood glucose monitoring management norms, knowledge and behavior (both P < 0.05). Conclusion: The standard knowledge of blood glucose monitoring and management of clinical nurses in Nyingchi region of Tibet is at the middle level, positive attitude and unsatisfactory behavior. Nursing managers should conduct standardized training for clinical nurses in blood glucose monitoring, develop the training mode of diabetes specialty nursing talents in Nyingchi area, and construct a complete management system of diabetes specialty nursing.

Applying the AHP-FUZZY method to evaluate the measure effect of rubble roadbed engineering in permafrost regions of Qinghai-Tibet Plateau: a case study of Chaidaer-Muli Railway

This article attempts to investigate the measure effect of rubble roadbed engineering in permafrost regions of Qinghai-Tibet Plateau. As a case study, Chaidaer-Muli Railway is used to evaluate the measure effect of rubble roadbed engineering in permafrost regions. The AHP(Analytic Hierarchy Process) method is thus employed to establish the evaluation indicator system. The evaluation factor is selected by analyzing the mutual relation between the permafrost environment and roadbed engineering. Thus, a hierarchical structure model is established based on the selected evaluation indices. Each factor is weighted to determine the status in the evaluation system, and grading standards are built for providing a basis for the evaluation. Then, the fuzzy mathematical method is introduced to evaluate the measure effect of rubble roadbed engineering in permafrost regions along the Chadaer-Muli Railway. Results show that most of the permafrost roadbed is in a preferable condition(b) along the Chaidaer-Muli Railway due to rubble engineering measures. This proportion reaches to 86.1%. The proportion in good(a), general(c) and poor states(d) are 0.0%, 7.5% and 6.4%, respectively, in all the evaluation sections along the Chaidaer-Muli Railway. Ground-temperature monitoring results are generally consistent with AHP-FUZZY evaluation results. This means that the AHP-FUZZY method can be applied to evaluate the effect of rubble roadbed engineering measures in permafrost regions. The effect evaluation of engineering measures will provide timely and effective feedback information for further engineering design. The series of engineering measures will more effectively protect permafrost stability.

Age of the Purported Zhanjin Formation in Gêrzê County, Tibet: A New Understanding and Its Significance

The Upper Carboniferous Zhanjin Formation has attracted much attention from geoscientists for containing glacial–marine diamictite and cold-water fauna typified by the bivalve Eurydesma.The presence of this Formation has provided important evidence for determining the northern border of Gondwana.Previous researchers have classified those strata north of Niangrong Co in the Gêrzê region as part of the Zhanjin Formation based on the presence of glacial–marine diamictite, although the absence of biological fossil evidence has defied clear age determination.Our field investigations first discovered large quantities of corals, sponges and bryozoans.All coral fossils were identified as belonging to the Hexacorallia subclass including 13 genera and 25 species, primarily including Conophyllia guiyangensis Deng et Kong, Coryphyllia regularis Cuif, Cuifia columnaris Roniewicz, Distichophyllia norica Frech, Distichophyllia gigas Vinassa de Regny, Pamiroseris rectilamellosa Winkler, Retiophyllia clathrata Emmrich, and Retiophyllia paraclathrata Roniewicz.Extensive biostratigraphic correlations show that the hexacorallia should belong to the Late Triassic, thereby negating the presence of the Zhanjin Formation in the study area.Based on analyses of sedimentary facies and detailed study of the glacial–marine diamictite as supposed by earlier researchers, the limestone blocks and gravels within the facies are slope facies olistostromes and waterway sediments from lime slurry debris flows in the submarine fan rather than primary sedimentary products.Among them, lenticular sandstone should be sequentially distributed waterway sand bodies, indicating that the strata have no glacial–marine diamictite.In addition, the rocks containing the mentioned fossils are just limestone blocks from olistostromes, and limestone gravels from waterways of submarine fans.Such a result further negates the presence of the Zhanjin Formation in the study area, and indicates that the age of the studied strata should be youner than the Late Triassic.Through regional stratigraphic comparisons and the study of tectonic settings of the strata, the sedimentary characteristics of the subject strata, including lithology, lithofacies and fossils, are confirmed to be similar to the widely distributed Sêwa Formation in this region.We thus infer that the strata belong to the Middle–Lower Jurassic Sêwa Formation.This finding is important for both studying paleogeography of Tibet and determining the northern boundary of Gondwana.

Changes of population growth in Tibet Autonomous Region

The population of the Tibet Autonomous Region which is thinly scattered, is almost entirely Tibetan. The unique high and cold climate, varied and changeable topography and social economic and human environment restrict population mobility in the region. Historically there were little statistic documents and the early data about population scale is poorly reliable. After the peaceful liberation of Tibet in 1951, its population went up continuously, and the growth rate has been higher than the national average level since 1964. The general tendency was that the pattern of population increase had changed within a short period. At first, the death rate was lowered quickly and the natural population increase speed was quickened, then, the death rate was lowered further, and the birth rate began to rise at a quick speed. After 1970, both the death rate and birth rate was generally stable, the level was relatively lower than before, the death rate slowed down at a quicker speed than the birth rate. The natural population increase rate rose extremely slowly, which formed the population development situation of fast but steady increase. The future population development tendency is that, the quick increase tendency characterized by young population will continue for quite a long time, and the pressure of future population increase upon resources environment will become increasingly great. The age structure and sex composition of population in Tibet, rather low since long time ago, became increasingly high upon entering the 1980s, but it was still the lowest one compared to other provinces or regions in China. The main reason is due to the low sex ratio of Tibetan infants and children caused by the low sex ratio of newly born infants and the high death rate of male infants, which will slow down the population increase in a limited way. There are few barren lands appropriate for farming and there exist many restricting factors for cultivation or utilization. With further increase in Tibetan population, it is inevitable that per capita available cultivated land will drop continuously. The problem of food supply in Tibet will still be the main issue in its regional development with the increase of population. It is impossible to support a quickly increasing population with the limited agricultural resources in Tibet. Therefore, the population development direction of Tibet can only be to tighten quantity control and to popularize family planning knowledge among Tibetan people. It is a fundamental strategic policy for the social and economic development in Tibet if family planning can be followed progressively on a voluntary basis.

Petrogenesis and Tectonic Implications of the Latest Cretaceous Intrusive Rocks from the Eastern Gangdese Belt,Southeast Tibet

The latest Cretaceous magmatic activity in the eastern segment of the Lhasa terrane provides important insights for tracking the magma source and geodynamic setting of the eastern Gangdese batholith,eastward of eastern Himalayan Syntaxis.Detailed petrological,geochemical and geochronological studies of the intrusive rocks(monzodiorites and granodiorites)of the eastern Gangdese batholith are presented with monzodiorites and granodiorites giving zircon U-Pb crystallization dates of 70-66 Ma and 71-66 Ma withεHf(t)values of−4.8 to+6.2 and−1.9 to+5.3,respectively.These rocks are metaluminous to weakly peraluminous I-type granites showing geochemically arc-related features of enrichment in LREEs and some LILEs,e.g.,Rb,Th,and U,and depletion in HREEs and some HFSEs,e.g.,Nb,Ta,and Ti.The rocks are interpreted to be derived from partial melting of mantle material and juvenile crust,respectively,which are proposed to be triggered by Neo-Tethyan slab rollback during northward subduction,with both experiencing ancient crustal contamination.The studied intrusive rocks formed in a transitional geodynamic setting caused by Neo-Tethyan oceanic flat subduction to slab rollback beneath the eastern Gangdese belt during the latest Cretaceous.

Estimation of Regional Evapotranspiration in Alpine Area and Its Response to Land Use Change:A Case Study in Three-River Headwaters Region of Qinghai-Tibet Plateau,China

Three-River Headwaters(TRH) region involved in this paper refers to the source region of the Changjiang(Yangtze) River,the Huanghe(Yellow) River and the Lancang River in China.Taking the TRH region of the Qinghai-Tibet Plateau as a case,the annual evapotranspiration(ET) model developed by Zhang et al.(2001) was applied to evaluate mean annual ET in the alpine area,and the response of annual ET to land use change was analyzed.The plant-available water coefficient(w) of Zhang's model was revised by using vegetation-temperature condition index(VTCI) before annual ET was calculated in alpine area.The future land use scenario,an input of ET model,was spatially simulated by using the conversion of land use and its effects at small regional extent(CLUE-S) to study the response of ET to land use change.Results show that the relative errors between the simulated ET and that calculated by using water balance equation were 3.81% and the index of agreement was 0.69.This indicates that Zhang's ET model based on revised plant-available water coefficient is a scientific and practical tool to estimate the annual ET in the alpine area.The annual ET in 2000 in the study area was 221.2 mm,11.6 mm more than that in 1980.Average annual ET decreased from southeast to northwest,but the change of annual ET between 1980 and 2000 increased from southeast to northwest.As a vast and sparsely populated area,the population in the TRH region was extremely unbalanced and land use change was concentrated in very small regions.Thus,land use change had little effect on total annual ET in the study area but a great impact on its spatial distribution,and the effect of land use change on ET decreased with increasing precipitation.ET was most sensitive to the interconversion between forest and unused land,and was least sensitive to the interconversion between cropland and low-covered grassland.

CRUSTAL STRUCTURE IN EASTERN REGION OF QINGHAI—TIBET PLATEAU

A geophysical survey including Magnetotelluric sounding(MT), gravity and geomagnetism was carried out in eastern region of Qinghai—Tibet plateau in 1998. It is to be known from tectonic map that study area was divided into four blocks by three large sutures, but we have very little information on deep\|seated structure which have close relationship with evolution of Tibet plateau, our purpose is to find some deep crustal structure evidences of the blocks and sutures for understanding deep tectonic feature in this region. The geophysical survey region is located in about 97～98°E and 35～26°N, the profile with the length of 760km runs through Bayanhar, Qingtang and Gandise block in NS direction, 349 gravity and geomagnetic data were acquired simultaneously, and 31 MT sites are be placed along the profile with about 18km\|interval to detect electrical conductive feature.