Glacier flow transports the mass obtained in the accumulation area to the ablation area， and controls the length， area， mass balance and thickness of a glacier， which is the key factor to control the advance and retreat of a glacier. In recent years， with the climate change， most of the glaciers in the world are retreating， but a glacier flow variation is more complex， which has attracted extensive attention of scholars. This paper systematically summarizes the extraction methods of glacier flow velocity， research progress on spatial distribution and change of glacier flow velocity， as well as its change with time and influencing factors in recent years， together with discussing the problems existing in the current glacier flow velocity research and the future development trend. The results show that the method based on the stakes can obtain the data with high accuracy， but it has limitations in time and space. At present， the method of automatic extracts glacier flow velocity based on remote sensing data has been widely used. However， the registration of images and the calculation of massive data are the main problems restricting the research of glacier flow velocity at the current stage. In recent years， unmanned aerial vehicles and ground-based synthetic aperture radar are increasingly applied to study on glaciology， providing high-precision data support for glacier flow velocity studies， but not widely enough. The spatial distribution of glacier flow velocity and its variation with time are different from space to space. The current results suggest that the change in thickness of glaciers is probably the main cause of flow velocity change in most glaciers around the world. However， the changes of glacier flow velocity are more complex on a single glacier system， and the reasons need further discussion. With the remote sensing data increasing and cloud computing platforms using， popularity of new technologies such as the Internet of things， unmanned aerial vehicles and ground-based synthetic aperture radar， as well as the emergence of coordinated satellite， air and earth observations， the study of glacier flow velocity will greatly promote in the future. In addition， the mechanism of glacier flow velocity and its dynamic process should be pay more attention to， as a hot topic in the future research of glaciology.
Based on topographic maps and Landsat TM/OLI remote sensing images and other data， visual interpretation and band ratio method were used to extract the spatial distribution data of glaciers in the Mount Namjagbarwa in 1980， 2000 and 2015， to analyze the glacier variation in the study area from 1980 to 2015， and to discuss the response of glaciers to climate change. The results show that from 1980 to 2015， the glacierized area in the Mount Namjagbarwa had continued to decrease and showed a trend of accelerated retreat. From 1980 to 2015 the total glacierized area had decreased by （75.23±4.67） km2， accounting for （25.2±1.6）% of the total glacierized area in 1980， with the annual mean decreasing rate of （0.73±0.05）%. The glacierized area changing rate on the southeast slopes of the study area was higher than that on the northwest slopes， with a glacierized area variation varying greatly in between different river basins， elevations and orientations. Debris was well developed in the Mount Namjagbarwa， and the change rate of debris covered glacierized area was less than that of non-debris covered glacierized area. Debris cover has an inhibitory effect on glacier ablation. Under the background of significantly rising temperature， although precipitation had increased also， the glacier was still more sensitive to the climate warming. The mass loss caused by the glacier ablation due to rising temperature exceeded the mass accumulation due to precipitation increase， leading to the general shrinking of the glaciers in the mount.
The glacial outburst flood of Lake Merzbacher is the serious disaster source of the Aksu River. In this study， utilizing the remote sensing data of Landsat， HJ-1A/B and GF-1 from 1998 to 2017， the lake’s area was abstracted with the method of Munsell HSV Transform. By analyzing and comparing the maximum lake area of different years， it was found that the area of Lake Merzbacher has shrank from 3.75 km2 to 2.87 km2 in recent 20 years. Lake Merzbacher contains two small lakes， Upper lake and Lower lake. Lower lake which dominates the storage of the whole lake has shrank from 3.3 km2 to 1.88 km2 during 1998 - 2017. On the contrary， Upper lake has expanded. As a consequence， the total water capacity has reduced. The relationship between the area of Lake Merzbacher and temperature was examined， and it is found that positive accumulated temperature affected by the lake’s outburst date has strong positive correlation with the area of Lower lake， which means that temperature can make a difference to the lake’s area through impacting meltwater to the lake and the stability of the dam.
Based on the ASI （ARTIST sea ice） algorithm， the pure water and pure ice point values of the FengYun-3C meteorological satellite （FY-3C） microwave radiometer （MWRI） data are obtained. The ASI sea ice concentration calculation formula based on FY-3 MWRI data is determined by interpolation method， and the weather filter threshold is obtained by Otsu method. Taking the January， 2016 data as an example， the inversion results of the Arctic sea ice concentration were obtained. It was compared with sea ice concentration products provided by National Snow and Ice Data Center （NSIDC）， USA， and University Bremen， Germany. The results show that the average sea ice area and average concentration in January based on MWRI data are between the two products， with a discrepancy of average concentration of only 1.310% different with Bremen products. The results are compared with those obtained from MERSI （medium resolution spectral imaging） data with 250 m spatial resolution of FengYun satellite. The results show that the outer line of sea ice is basically the same. The sea ice concentration and area obtained from optical data are 5.029% and 9.318% higher than those from MWRI data， respectively. Therefore， this method can effectively promote the inversion of Arctic sea ice concentration by MWRI data， and can be effectively used to monitor Arctic sea ice distribution and changes.
The CMA Global ReAnalysis product CRA Interim was released in 2017 by China Meteorological Administration. The accuracy of daily minimum， maximum and mean 2-m air temperatures （Tmin， Tmax， Tmean） in 2016 from CRA Interim was assessed against field observations and ECMWF Re-Analysis products （ERA Interim and ERA5）. The field observations were from Zhongshan Station， Eagle Station and Dome A that located in East Antarctica. It was found that CRA Interim can capture temporal temperature variations， with an explained variance more than 81.0%， and generally showed a negative bias of -0.5， -1.8， -1.3 ℃ for Tmin， Tmax and Tmean， respectively. Similar as ECMWF Re-Analysis products， CRA Interim showed a regional variability， and performed better at Zhongshan Station. CRA Interim and ERA5 performed better in summer， while ERA Interim performed better in autumn. CRA Interim can explain the temperature variance of more than 45.0% for extreme low temperature event， and close to 60.0% for extreme high temperature event. The cold event occurred during Sept. 3 to Sept. 13， which was mainly affected by stronger cold high pressure. The warm event occurred during Jul. 25 to Aug. 6， and was mainly affected by warm low pressure and warm tongue. An analysis on temperature and pressure fields indicated that CRA Interim can replicate the progress of temperature extremes developing， occurring and disappearing. However， it doesn’t work well in wind field， particularly at Zhongshan Station. ECMWF Re-Analysis products perform better than CRA Interim， and ERA5 is a more powerful tool for extreme weather and climate studies in East Antarctica.
Based on the soil hydrothermal and meteorological data on top as well as bottom of the shady slope and bottom of the sunny slope on a slope of the Fenghuoshan basin， Tibetan Plateau， the spatial and temporal variability of soil water content and temperature under different topographic conditions were analyzed. The results show that in the thaw period， below the depth of 5 cm， the starting date of soil thawing on bottom of the shady slope was earlier than that on top of the slope， but was lagged to that on bottom of the sunny slope. The soil water content on bottom of the shady slope was higher than that on top of the shady slope and bottom of the sunny slope. In the freezing period， the starting date of soil freezing at all depths on bottom of the shady slope was earlier than that on top of the slope， but lagged to that on bottom of the sunny slope. The soil water content on bottom of the shady slope was higher than that in the corresponding soil layer on top of the shady slope， and at depths of 20 cm， 100 cm and 160 cm it was higher than that in the corresponding soil layer on the sunny slope， but at depths of 5 cm and 50 cm， the difference between the two was small after stable freezing. In the whole freezing-thawing process， the response of soil temperature on bottom of the shady slope to temperature change was weaker than that on top of the shady slope and bottom of the sunny slope， but the response of water content to rainfall was stronger than that on top of the shady slope and bottom of the sunny slope. Since vegetation growth and development is dependent on soil water content and temperature condition， the spatial and temporal variability of soil water content and temperature under different topographic conditions will affect the spatial distribution characteristics of vegetation. In the case of future climate warming， the vegetation on slope top may degrade and desertification will be appeared due to water deficit. While soil water on bottom of a slope responds strongly to rainfall and the vegetation will not degrade significantly. Between different slope directions， the degree of vegetation degradation may be greater on the sunny slope than on the shady slope.
Based on daily temperature data from 68 national meteorological stations in northeastern Qinghai-Tibet Plateau from 1961 to 2015， the annual， seasonal and yearly frequency sequence of cold waves and the annual， seasonal and yearly mean frequency sequence of cold waves in the region were obtained. Then climate diagnostic method was adopted to analyze the characteristics of spatial and temporal changes of cold wave frequency. The results indicated that in terms of temporal changes， from the 1960s to the 2000s， the annual average frequency sequence of cold waves had presented an evolution process of “more-more-more-more-less”. The average value of annual cold wave frequency in northeastern Qinghai-Tibet Plateau was 2.6 times. Meanwhile， the frequency sequence appeared a significantly declining tendency， with a declining rate of 0.192 times in every ten years； the annual frequency of cold waves presented an obvious point of abrupt in 1981. From 2005 to 2015， the ten years had a significantly decreasing trend， while from 1961 to 2004， the decreasing tendency became insignificant. The average values of cold wave frequency in spring， autumn and winter in the whole region were， respectively， 0.7， 0.7 and 1.2 times， and the sequence in autumn shown an obviously declining tendency； the declining tendencies of average cold wave frequency in the whole region in February and November were more significant than those in other months. Spatially， the frequency sequence of cold waves in the 19 stations in the whole year， 44 stations in spring and 21 stations in autumn had shown significant declining tendency. The characteristics of above periodic changes and decreasing tendencies has been basically consistent with the tendency of temperature rise in the Qinghai-Tibet Plateau since the 1980s.
Based on the observation of seasonally frozen ground， snow cover and temperature during 2000 - 2014 from various representative meteorological stations in the Ili basin， using linear regression and correlation analysis， the variation of seasonally frozen ground along altitude and the influence of temperature and snow cover depth on seasonally frozen ground in the Ili basin were analyzed. The results showed that the ground starts freezing in November and thawed completely in April of the next year in the prefecture. The seasonally frozen duration and maximum frozen depth of the ground increases with the rates of 4 d·（100m）-1 and 3.9 cm·（100m）-1， respectively， with altitude. The seasonally frozen duration of the ground shows a significant negative correlation to the average temperature during soil freezing period （R=-0.98， P<0.05）. The frozen duration of the ground is positively correlated with the duration of snow cover， and the maximum frozen depth of the ground is negatively correlated with the maximum snow depth. The temperature decreases with the increase of altitude， which leads to the overall increase of maximum frozen depth of the ground and the frozen duration of the ground in the Ili basin. However， the maximum frozen depth of the ground shows decreases with the increase of altitude in the relatively high altitude region due to the influence of relatively thick snowpack. The results of the study will provide help for the research on the response of seasonally frozen ground distribution to climate change in the Ili basin， thus helping ecological planning， water resources management and agricultural development to formulate adaptive climate change countermeasures.
The ground ice in permafrost is meaningful for studying permafrost environment， ecology and frozen soil engineering. However， there is not detailed study of it in the Tibetan Plateau. Taking the source areas of the Datong River in the Qilian Mountains as an example， based on the geomorphic classification， permafrost distribution， borehole data and geological survey data， the ground ice reserve in the depth range of 2.5~10.0 m of the permafrost is estimated in both horizontal and vertical directions. The spatial distribution characteristics of the ground ice in the source areas of the Datong River also discuss. It is found that in the depth range of 2.5~10.0 m， the total volume of ground ice is about （11.70±7.24） km3， and the ground ice content per m3 soil is about （0.396±0.245） m3. In the horizontal direction， periglacial lacustrine plain and periglacial hill contain more ice， but erosional platform and alluvial-proluvial plain contain less ice. In vertical direction， the amount of ice is more near the permafrost table and decreases slowly downwards. The study of ground ice reserves is of great significance in ecological， hydrogeological， frozen ground construction， as well as useful for thawing settlement prediction and other geological hazard prediction.
A special interval zone called frozen fringe developed between the freezing front and ice lens during the freezing process of soil. Frozen fringe as the coupling result of temperature field， moisture field and stress field， which become a water source for ice segregation， the ice-water phase transition zone， and the only way for water migration during soil freezing. Frozen fringe becomes a basic factor to understand the mechanism of frost heave. Therefore， through literature reviewing， recent achievements and progress of the frozen fringe， including the formation of the frozen fringe， theories and experiments， microstructure， characteristic parameters， and the model construction of the frozen fringe， are presented. Furthermore， the development tendency of the frozen fringe is an experimental study. It is urgent to propose a new technique to observe the microstructure of the frozen fringe， and to build better a model with the change of characteristic parameters. Study of frozen fringe is reliable to provide theoretical support for the analysis of frost heave mechanism， and accurate to predict frozen soils.
The thermal disturbance caused by the construction of cast-in-place pile foundation in permafrost regions weakens the early thermal stability of the pile foundation and reduces the bearing capacity. This paper discusses the research of early thermal stability of cast-in-place pile foundation from three aspects： the influencing factors of early thermal stability， the influence of thermal stability on bearing capacity， and the improvement measures. Cast-in-place pile foundations in permafrost regions have the characteristics of large thermal disturbance range and long refreezing time. The heat of hydration and cementitious materials， casting temperature， and drilling methods are the main sources of thermal disturbances. Pile characteristics and geological conditions as indirect factors also have a secondary impact on the early thermal stability. The thermal disturbance significantly reduces the early bearing capacity of the cast-in-place pile foundation and delay the construction time of the superstructure. The cooling liquid and thermosyphons have been verified by actual engineering to have a significant effect of accelerating refreezing process. The future related research is prospected， and it is believed that the thermal disturbance process caused by different drilling methods， the low-hydration thermal cementing materials suitable for permafrost regions， and cost-effective temperature control measures should be further studied to improve early bearing capacity.
permafrost （frozen soil） and earthquake are two major challenges for the bridge construction in cold regions with high earthquake intensity in western China. Especially to the widely applied bridges with pile-foundation， the permafrost will significantly affect the pile-soil dynamic interaction process under the earthquake action， and bring difficulties to the seismic analysis. Previous studies have shown that the presence of permafrost had a significant impact on the seismic response of bridge structures， and it was unreasonable without considering the effect of permafrost in the seismic design of pile foundation bridges. It is reviewed that the effect on seismic response of bridges， frozen soil-pile interaction effect and its calculation model and so on. It is unreasonable that not to consider permafrost effect on seismic design of bridge with pile foundation. The problems in current researches are： （1） soil freezing effect has not been fully considered in the research of the bridge seismic response in frozen regions； （2） the existing pile-soil interaction model is rarely applied in permafrost； （3） the interaction mechanism and destroy characteristics of pile-soil system under earthquake are not clear. Based on these situations， some proposals are put forward for future researches.
In deep seasonally frozen ground regions， the interaction between freezing soil and pile may cause frost jacking or failure of pile. In the process of frost heave of soil surrounding the pile， the anchoring effect is mainly carried out through the frictional resistance of pile-thawing soil interface for a uniform-section pile. However， for a pile with enlarged end， whose base diameter is larger than its shaft diameter， will be subjected to the resistance of the overlying soil and play a role of anchoring or anti-frost jacking characteristic when the pile is tend to be pull up. By reviewing the domestic and foreign research literature， the paper briefly introduces the existing engineering background and application of the pile with enlarged end，and summarizes and analyses the mechanical properties of the pile foundation in the deep seasonally frozen ground regions. The main contents include the interaction between frost heave of soil and pile foundation， the experimental and theoretical research on tangential frost heave force， and the experimental and theoretical research on counter-frost heave force of pile foundation with enlarged end， and frictional resistance between pile and thawed soil under the action of tangential frost heave force， etc. In the end， the application and research of the pile foundation with enlarged end in the seasonal frozen ground regions are further prospected.
In order to study the influence of different freezing conditions on the dynamic parameters of aeolian sand in western Liaoning Province， taking the Fuxin Section of Beijing to Shenyang Passenger Line as the research background， the effects of temperature， water content， freeze-thaw cycles on dynamic elastic modulus and damping ratio of frozen soil were tested by using GDS dynamic triaxial testing system. The variations of dynamic modulus and damping ratio of soil were obtained， and the correction coefficient of aerodynamic parameters of aeolian sand was proposed. The changes of dynamic modulus and damping ratio of soil were obtained， and the correction coefficient of dynamic characteristic parameters of aeolian sand was given from the test. The results show that with decrease of ambient temperature， the dynamic modulus of soil increases gradually， and the damping ratio decreases gradually. The temperature is approximately linear changing with elastic modulus， and is exponentially related to damping ratio. With the increase of water content， the dynamic modulus of soil increases gradually； there is a sensitive interval of water content， in which the dynamic modulus of elasticity changes obviously. The relationship between water content and damping ratio is not very obvious， and the damping ratio decreases slightly with the increase of water content. With increase of freeze-thaw cycles， dynamic elastic modulus decreases gradually， and the damping ratio increases gradually. During the first five freeze-thaw cycles there is great influence on the dynamic parameters of soil， and then the influence decreases gradually. The correction coefficient of the dynamic parameters of the aeolian sand is worked out， which reflects the variation of the dynamic parameters of the soil under different freezing conditions， and would be useful for railway construction in seasonal frozen areas.
In order to obtain the effect of freezing-thawing cycles on the pore size distribution of loess， remolded loess was taken as the research object， the pore characteristics of loess specimens after different freeze-thaw cycles were tested by mercury intrusion porosimetory. In addition， quantitative characterization and comparative study of microscopic pore structure of loess were carried out by using three kinds of fractal models. The results showed that the pore distribution curve of loess without freezing-thawing action is unimodal， while the pore distribution curve in loess subjected to freezing-thawing is bimodal or even multimodal. The freezing-thawing cycle has a considerable influence on the pore size within the range of 0.1 - 10 μm in loess. The porosity of loess increases during the first ten freezing-thawing cycles， especially after six freezing-thawing cycles， the porosity increases by about 18.8%. As freezing-thawing cycle continuing， the porosity in loess decreased and stabilized. The pore size distribution of loess after various freezing-thawing cycles exhibits a good statistical fractal characteristics. Based on the thermodynamic model and capillary pressure curve method to characterize the pore structure of loess， the loess pores exhibit significant fractal characteristics and can give a unique and reasonable fractal dimension over the entire pore size scale. However， while the Menger sponge model is adopted， the fractal characteristics of loess pores exhibit multi-scale fractal， and there are different fractal dimensions in different scales. Combined with fractal theory， it can be concluded that freezing-thawing changes the porosity uniformity and complexity of loess.
The frost heave is obviously restrained by the load， but it still exists when the load is quite large. At present， there are few studies on the frost heave under high load. To evaluate high load effected frost heave， the frost heaving test of loess samples considering the effect of water content， density and load was carried out， which revealed the close relationship between the frost heaving rate of loess and soil water content， density and load. The tests indicated that， when the upper load of soil sample is small， the frost heave rate decreases greatly compared with that under the natural state. While the load continues to increase， the restraining effect of load increment on frost heave decreases. The frost heave rate decreases exponentially with the increase of load. The freeze-heaving rate of loess varies greatly with the dry density under free freeze-heaving condition. The frost heaving rate of loess samples has little change with the dry density after the load is applied. The greater the water content of soil sample， the greater the change of frost heave with dry density. The frost heave ratio increases linearly with the increase of water content. When the load level is high， the frost heaving rate increases with the increase of water content， but the increase amplitude is significantly lower than that of free frost heaving. Among the factors affecting frost heaving in loess area， the load has greatest influence on frost heaving， followed by the water content and the dry density. Moreover， by fitting the test results of soil samples with different water content and dry density under different loads， the frost heaving prediction model of unsaturated loess is obtained.
With the gradual development of high-speed railway in cold region， a large proportion of bridges were used to cross the complex terrain and roadbed-bridge transition sections were appeared. For the discontinuities changes of stiffness between bridge and roadbed， and the anti-frost properties difference of geomaterials， the uneven frost heave could be triggered and reduce the comfort and safety of the vehicle. In this paper， the equations of heat transfer about soil freezing and thawing were considered to analyze the freezing characteristics and changing process， with the parameters of model which derived from Harbin-Dalian high-speed railway. Then in the optimal design stage， three different models were analyzed for the four parameters of frozen area， perimeter， ratio of length and width， and transverse thermal disturbance distance. The results show that the model of insulation layer and non-cone slope provides a better effect for the roadbed-bridge transition section， as just considering thermal influence.
As a ballast material， the crushed rock is able to disperse train dynamic load， and it has a distinct characteristic of good convective heat transfer characteristics. Therefore， it was extensively used to cool the permafrost embankment in Qinghai-Tibet Railway. However， the crushed rock layer is compacted and even crushed under train load， so the cooling effect of the crushed rock layer decreases. For this reason， it is very important to study deformation process and mechanisms of the crushed rock layer. In this study， numerical simulations on triaxial tests of the crushed rock were carried out by the discrete element method （DEM）. A comparison between experimental and numerical results show they well agree with each other， which implies the DEM can simulate the deformation process of the crushed rock. Moreover， the numerical result indicates that the deviatoric stresses and shear strength values increase with confining pressure and block size. The mainly deformation of the crushed rocks is an X shear band formed by sliding and separating along the contact surface under the shear action. In addition， there are different degrees of expansion in the radial direction. The research idea and method of the crushed rock layer in this study will be useful for evaluating thermodynamic stability of the crushed rock embankment of the Qinghai-Tibet Railway.
Deformation and failure of coal rock is a complicated and gradual evolution process. In order to study the failure mechanisms of frozen cracked coal， a uniaxial compression model of frozen cracked coal was established based on CT machine images and using 3-D discrete element method. The numerical stress-strain curves were compared with experimental ones， which showed that there was in good agreement between the numerical and experimental results. Then， the micro-structure damage and failure processes of the cracked coal were analyzed. Simultaneously， the development law and mathematical relationship between the strength and elastic modulus of coal rock and temperature was obtained. Through above studies， a new idea is found to analyze damage failure of frozen cracked coal by discrete element method. The idea and method in this study may be useful for studying other discrete materials.
Muzati River is the most glacierized catchment on the southern slope of the Tianshan Mountains. As the high sensitivity of hydrological processes of the catchment to climate change， it is essential to quantify the impacts of climate change on hydrological processes for the scientific water resources planning， management and sustainable utilization. The VIC-CAS model was adopted as computing platform. The glacier inventory data and observed runoff were accounted for multi-objective calibration and validation to improve the “truth” of simulations. Then the runoff components， runoff variation characteristics and response mechanism of runoff to climate change were quantitatively analyzed using the simulations and observations. The following major conclusions are drawn： The runoff is concentrated in warm season （May to September）， accounting for 77.9% to the annual runoff. The contribution of glacier runoff， snowmelt runoff and rainfall runoff to the total runoff was 66.6%， 26.4% and 7.0%， respectively. Over the past 40 years （1971 - 2010）， the annual average air temperature and precipitation had shown a significant increasing trend. Due to increasing precipitation， the snowmelt runoff and rainfall runoff had shown increasing trends. But the annual runoff had shown a slight decreasing trend because of decreasing glacier runoff. Air temperature was projected to rise， while precipitation was projected to slightly decrease under RCP4.5 scenario. As air temperature rise， more precipitation will be in the form of rain. The rainfall runoff is predicted to obviously increase， while the snowfall and snowmelt runoff had been reached peak in 1990s， and significantly decline later. The glaciers are projected to retreat steadily， so the glacier runoff had reached a tipping point in 2010s. Annual runoff was projected to decrease significantly as a result of decreasing glacier runoff.
The future （2013 - 2100） monthly mean runoff and glacial melt water from the mountainous area of the Heihe River are estimated based the data in historical periods （1960 - 2012） and forecasted in represented concentration pathway （RCP） scenarios （RCP2.6， RCP4.5 and RCP8.5）， using the probability distribution method and the river water flow anomaly method. The results show that compared with the historical period， the future runoff from the mountainous area of the river will increase slightly in different scenarios， but it is not significant. The maximum monthly （July to August） mountain runoff will be greatly reduced， the uncertainty will be reduced too， as well as the monthly minimum mountain runoff （December to January of the next year）； the change in runoff in the mountain areas will be not obvious； in the future， the occurrence probability of dry years in mountainous areas under different RCPs scenarios will increase by 2 to 3 times， and the probability of occurrence of dry years in RCP2.6 and RCP4.5 scenarios will also increase； the Heihe mainstream will enter median water year， even more dry. In the future， the glacial melt water runoff and the monthly maximum glacial melt water runoff of the river will significantly reduce， so do the ability of supply and regulation of the Heihe River runoff.
Culturable yeast was recovered by using RDBC， DG， MYP and MYP5 media， and the taxonomic position of the strains was determined by Internal Transcribed Spacer （ITS） sequence analysis. Enzyme producing strains were screened by a multi-point contact method， and the physiological and biochemical characteristics of the strains were comparatively analyzed. A total of 317 culturable yeasts were isolated from the surface ice core of Urumqi Glacier No.1. The results of NCBI blast of ITS rRNA gene sequence and MSP-PCR fingerprinting showed that 45 Rhodotorula strains isolated phylogenetically belonged to five recognized species： R.glutinis， R.araucariae， R.mucilaginosa， R.kratochvilovae and R.diobovata. The relationship between Rhodotorula species and their extracellular enzyme activity was revealed by ANOVA and cluster analysis. All strains produced at least two extracellular enzymes. Particularly， strains YHB-9， YHB-15， YHB-39， and YHB-45 can produce 5 kinds of enzymes. Among all 45 Rhodotorula strains， 100%， 98%， 47%， 20% and 9% strains produced pectinase， cellulase， amylase and urease， protease and lipase， respectively. By contrast， no strains produced chitinase. Physiological assay showed that the optimum growth temperature of 19 strains of yeast strains was around 21 ℃， whereas that of the other 26 strains was 24 ℃， indicating they belonged to psychrotolerant yeasts. Also， Rhodotorula yeast of the supraglacial habitats of the Glacier No.1 at headwater of Urumqi river in the Tianshan Mountains did not exhibit species-specificity of enzyme-producing properties （no significantly differences between species）. However， the enzyme-producing flexibility of Rhodotorula species indicates that strains of part cryotolerant yeast has a great potential in biotechnology applications.
The Denitrification-Decomposition （DNDC） model is a biogeochemical model based on the concepts of element abundance， coupling， circulation and dynamics. As a tool of solving present environmental problems based on the theory of biogeochemistry， the DNDC simulates carbon and nitrogen cycles by calculating the decomposition of organic matter in denitrification process. The aim of DNDC is to calculate the greenhouse gas emission fluxes in different pools in the target ecosystem. During more than 20 years， DNDC has become one of the most successful biogeochemical models in the world. This paper mainly described the development， scientific structure， model verification and correction of DNDC， and pointed out the shortcomings of DNDC. We put forward the application prospect of DNDC in alpine ecosystem.
Mining area development will lead to dramatic changes in the surrounding land cover and landscape pattern， but at present there is a lack of dynamic monitoring of the long-term sequence changes of the typical mining area in the Qinghai-Tibet Plateau and its surrounding land cover， especially the lack of in-depth understanding of the response characteristics of the landscape pattern vulnerability. So it is impossible to provide effective scientific guidance on rational development and ecological restoration of mining areas. Based on the method of remote sensing technology and land change science， as well as the concept of landscape pattern vulnerability， the changes of land cover and the response of regional landscape pattern vulnerability of Muli coal mine in the northern Qinghai-Tibet Plateau were analysed from 1975 to 2016. The results showed that the mining area was increasing in size， especially after 2000， and this caused shrinkage of the surrounding lands， including alpine meadow wetland， other and alpine meadow. The indirect effect of the mining expansion on the surrounding ecosystem was increasing， which concluded from the decrease of water area， the degradation of alpine meadow wetland and the slight reserve of the mining area. The development of Muli mining area has led to the increase of the regional landscape pattern vulnerability， which might have a negative impact on the surrounding ecosystem service function. Therefore， the landscape pattern optimization should be considered in the ecological restoration and mining planning in order to reduce the vulnerability of landscape pattern. The research results of this paper can provide some reference for the rational development planning and ecological restoration of mining areas on the Qinghai-Tibet Plateau and other ecologically fragile areas.
The lake area of Zonag Lake has shrunk quickly after its outburst in September， 2011， which results in large area desertification disaster and has a major impact on the regional ecological environment. At the same time， the water level of Yanhu Lake has increased quickly after receiving the flood， which threats the safety of the Qinghai-Tibet Highway Engineering Corridor. Based on the field investigation data， this paper suggest that the outburst of Zonag Lake was caused by the overflow of the lake water. After the lakebed was partly exposed， the naked lakebed became the source of sandstorms. The lake bottom and the surrounding grassland formed a large area of desertification. As the water of Zonag Lake was continuously discharged in recent years， the exposed area of the lakebed has been further expanded， the desertification phenomenon in the lake area has been intensified， and the downstream river channel erosion has been deepened and widened. Comparing the topographical conditions and water balance characteristics in the regions of Zonag Lake and Yanhu Lake， this paper suggest that the possible outburst mode of Yanhu Lake will be similar to that of Zonag Lake. Because the Yanhu Lake discharge more water per year than the Zonag Lake did， when the Yanhu Lake is broken， the erosion effect of the flood on the river channel will be greater than that in the Zonag Lake region.
In this study， a model has developed for risk assessment of snow disaster in the pastoral area of Xilingol League based on BP （back propagation artificial neural network）， AHP （analytic hierarchy process） and fuzzy comprehensive evaluation method by using MATLAB， ArcGIS and SPSS. The indicator system of the snow disaster risk assessment is composed of disaster inducing indicators related with the snow depth； the disaster pregnant environment meteorological indicators are mainly constitute of temperature and wind speed indexes； disaster pregnant environment underlying surface indicators are formed by slope and vegetation coverage； vulnerability indicators of disaster bearing bodies are constituted by population density， herdsmen’s net income， GDP per capita， overload rate of livestock. The curve of the predicted hazard level and actual hazard level fits perfectly. Therefore， in this paper， using BP to do the risk assessment of the snow disaster by monthly from November to March of the following year from 1980 to 2015 for each county. Snow hazard is climatic disaster which is highly related with snow cover； It is the result of long-term effects of snow cover， low temperature and strong wind. Except the index that the rainfall during grass growth period， the other indexes are monthly scale， so it can enhance the accuracy of hazard assessment. The effect of risk assessment is comparably ideal， since it is possible to form product of the risk grade of white dzud based on BP method through gaining numerical prediction products and climate prediction products. Consequently， these products will be gradually applied to daily business and provided decision-making basis for party committee and government.
The resource， environment， ecology， society， economy etc.， which are the factors influence the plateau wetland ecological security， had been comprehensively considered； the driving force - pressure - state - impact - response - management （DPSIRM） evaluation index system of plateau wetland ecological security had been established with a framework model， the gray correlation method had been utilized to assign weight to each evaluation index， and an evaluation model had been built with set pair analysis method to evaluate and research the wetland ecological security of Caohai in Weining Town from 2011 to 2016. The results reviewed the natural population growth rate， waste water discharge of per unit industrial output value， domestic sewage discharge， fertilizer application intensity， pesticide application intensity， per capita water resources， species diversity， water and soil loss rate， material production， wetland area degradation rate， sewage treatment rate， material life index， environmental protection investment index， and policy and law enforcement are the main factors affecting the ecological security of the wetlands in Caohai of Weining Town. Ecological security of Caohai wetland had been gradually improved. From 2011 to 2012， the ecological security of Caohai wetland had been belonged to the unsafe level， and from 2013 to 2016， had been belonged to the critical safety level. From the situation of each subsystem， the driving force subsystems were relatively safe， the pressure， state， impact， response and management subsystem were in critical safety level. This study will be useful for the ecological security and environmental construction of Caohai wetland in Weining Town.
In-depth analysis of spatial difference and spatial effect of willingness to pay has important practical guiding significance for zoning decision making， precise implementation of ecological governance projects， improvement of ecological compensation practice performance and improvement of governance and protection effects. In this paper， on the basis of determining the main factors affecting the willingness to pay of farmers in the river basin， the influence of each factor on the willingness to pay of farmers in the river basin was analyzed with the help of multiple Logistic model， and the spatial effect of the willingness to pay of farmers in the river basin was compared， respectively， by introducing access distance and distance to the river. It was found that： Without considering the distance factor， the influence of education level and farmer type on farmers’ willingness to pay is significant. In the case of considering the distance factor， there is no necessary correlation between education level and the willingness to pay； the simulation results of Model 3 show that the occurrence ratio of high school students in higher willingness to pay is 1.044， while the occurrence ratio of junior college students in higher willingness to pay is only 0.363， that is， the willingness to pay will not increase with the improvement of education level. The reach distance and the willingness to pay show a negative correlation （distance attenuation） and then a positive correlation （distance increasing）. The effect of distance to the river presents an obvious "distance attenuation" to the payment willingness of farmers in the river basin.
Black carbon （BC） in the atmosphere is mainly produced by incomplete combustion of fossil fuels and biomass fuels. It can reach and deposit on the surface of snow and ice in remote areas through transmission and deposition processes. Compared with clean snow surface， darker BC can absorb more solar radiation， resulting in lower snow surface albedo， accelerating snow and ice melting， and thus has a great influence on regional climate and environment. The environment of Tibetan Plateau （TP） is fragile and sensitive. It is the driver and amplifier of global climate change. There are many mineral impurities in the snow and ice samples from the TP， and the concentration of BC varies a lot. According to the characteristics of such sample， a new BC analysis method based on SP2 was established， detailed experimental procedures were developed and the ways of storage， sampling method and influence of sample dilution were evaluated. The results showed that the BC concentration in the snow and ice of TP ranged from 0.21 ng·mL-1 to 47.96 ng·mL-1， with an average value of 6.69 ng·mL-1. The aquadag was continuously measured during the testing process， and the revised online recovery was higher than 75%. Therefore， it is of great significance to obtain accurate and reliable BC content information in snow and ice of TP to reconstruct the historical trend of BC， and then to accurately assess its impact on the climate and environment.
As one of the core elements in the cryosphere， glacier is the natural indicator of climate change. By monitoring the changes in glaciers， we can understand the local or global climate change， and the technology of Unmanned Aerial Vehicle （UAV） is an important method for monitoring and studying glaciers today. In this paper， we choose Baishui River Glacier No.1 in Yulong Snow Mountains as the study region. The orthographic image with the resolution of 0.09 m in the terminus of the glaciers and the digital surface model （DSM） were produced by utilizing low-flying of UAV. Comparing the orthophotos with Gaofen No.1 （GF-1） Image and Pléiade resampled image provided by Google Earth， the result presented that UAV orthophotos had a good match with the images of GF-1 and Pléiade product in space. The UAV image with high spatial resolution can accurately express the characteristics of glacier surface and some microtopography. At the same time， the digital surface model （DSM） derived from UAV survey was more exquisite and accurate in terms of the glacier surface topography， with the spatial resolution of 0.09 m. In addition， the front position of Baishui River Glacier No.1 retreated 646.27 m±12.04 m during the period of 1957 - 2018 based on this test of UAV survey and historical satellite remote sensing data. In general， UAV has significant advantages in the process of conducting photogrammetry in terms of those glacier environments， including complex terrain， cloud weather， and difficult manual observation. Besides， the on-the-spot verification of UAV survey at the end of the glacier will provide a reference for the next step in the monitoring and calculation of the mass balance of glaciers.
GF-1 satellite’s successful launch opens a high resolution satellite earth observation. To discuss the effectiveness based on GF-1 satellite in the absence of short-wave infrared and thermal infrared bands in mapping glacier， in this study， glaciers are mapped based on the object-oriented method using GF-1 images， band ratio of Band 1 and Band 4， digital elevation model and slope information. The segmentation and merge levels and rules of glacier mapping were defined by trial and error， then the boundary of glacier was obtained. Confusion matrix was used to test and verify the results based on the Second Glacier Inventory Dataset of China （Version 1.0）， with overall accuracy and Kappa confidence of 90.05% and 0.79. Meanwhile， comparing this result with the result by visual revision showed that this approach could distinguish glacier well， except for the glacier terminal， the rule for glacier indicated blue band and DEM could distinguish ice from its surrounding， and the band ratio， slope and texture characteristic were helpful for extracting glacier terminal. This study showed that GF-1 satellite could map the boundary of glacier effectively， and could provide reliable data and research foundation for glacier research.
Ring artifacts and beam hardening artifacts are unavoidable in CT image of frozen soil. In order to remove the two kinds of artifacts， in this paper the characteristics and formation mechanisms of the two kinds of artifacts are analyzed and a hardware optimization solution for reducing artifacts is proposed. Firstly， the ring artifacts are reduced by increasing the X-ray luminous flux to change the X-ray energy spectrum. Secondly， the low energy rays in X-rays are pre-filtered by the filter materials of different thickness， so that the X-ray energy spectrum range across the frozen soil specimen is narrowed to correct the beam hardening artifacts. The test results show that increasing the scanning voltage to 120 kV can not only effectively reduce the ring artifacts in CT images of frozen soil， but also ensure the quality of the images. At the same time， the aluminum material of 2A12 with 18 mm thickness can effectively correct the artifacts caused by the beam hardening under the scanning voltage of 120 kV and scanning current of 230 mA.
