Air temperature is an important indicator to analyze climate change in mountainous areas.ERA5 reanalysis air temperature data are important products that were widely used to analyze temperature change in mountainous a...Air temperature is an important indicator to analyze climate change in mountainous areas.ERA5 reanalysis air temperature data are important products that were widely used to analyze temperature change in mountainous areas.However,the reliability of ERA5 reanalysis air temperature over the Qilian Mountains(QLM)is unclear.In this study,we evaluated the reliability of ERA5 monthly averaged reanalysis 2 m air temperature data using the observations at 17 meteorological stations in the QLM from 1979 to 2017.The results showed that:ERA5 reanalysis monthly averaged air temperature data have a good applicability in the QLM in general(R2=0.99).ERA5 reanalysis temperature data overestimated the observed temperature in the QLM in general.Root mean square error(RMSE)increases with the increasing of elevation range,showing that the reliability of ERA5 reanalysis temperature data is worse in higher elevation than that in lower altitude.ERA5 reanalysis temperature can capture observational warming rates well.All the smallest warming rates of observational temperature and ERA5 reanalysis temperature are found in winter,with the warming rates of 0.393°C/10a and 0.360°C/10a,respectively.This study will provide a reference for the application of ERA5 reanalysis monthly averaged air temperature data at different elevation ranges in the Qilian Mountains.展开更多
The ice-phase microphysical characteristics of a stratiform cloud system over the Qilian Mountains in northwestern China on 15 September 2022 were analyzed via aircraft data.The stratiform cloud system developed under...The ice-phase microphysical characteristics of a stratiform cloud system over the Qilian Mountains in northwestern China on 15 September 2022 were analyzed via aircraft data.The stratiform cloud system developed under southwesterly flows at 500 hPa and was affected locally by topography.Synoptic features and aircraft observations revealed strengthened cloud development on the leeward slope.The ice particle habits and microphysical processes at heights of 6-8 km were investigated.The cloud system was characterized by extremely low supercooled liquid water content at temperatures between−4℃ and−17℃.The ice particle concentrations ranged predominantly from 10 to 30 L^(−1),corresponding to ice water content ranging from 0.01 to 0.05 g m^(−3).Active ice aggregation was observed at temperatures colder than−10°C.The windward side of the cloud system exhibited weaker development and two distinct cloud layers.Intense orographic uplift on the leeward slope enhanced ice particle aggregation.The clouds on the leeside presented lower ice particle concentrations but larger sizes than those on the windward side.The influence of aggregation on the ice particle size distribution was reflected in two main aspects.One aspect was the bimodal spectra at−16℃,with the first peak at 125μm and subpeak at 400-500μm;the other was the broadened size spectra at−13℃ due to significant aggregation of dendrites.展开更多
The research on the conversion efficiency of"Green Mountains into Clear Water"(Green)and"Gold and silver Mountains"(Gold)is of great significance to promote the coordination between natural resourc...The research on the conversion efficiency of"Green Mountains into Clear Water"(Green)and"Gold and silver Mountains"(Gold)is of great significance to promote the coordination between natural resource conservation in national park and the local economic and social development.This paper pays attention to the linking role of ecosystem services in different stages of the conversion process between the Green and Gold.Based on the twostage division,this paper constructs the accounting framework for conversion efficiency of Green and Gold.That is,the comprehensive conversion efficiency of Green and Gold is decomposed into the I-stage efficiency of ecological inputs conversion to Green and the II-stage efficiency of ecosystem services conversion to economic output.Furthermore,the Qilian Mountain National Park in China and its surrounding area Zhangye City,is taken as an example.Using a two-stage non-oriented super-efficiency network EBM model and panel data from 2007 to 2018 to empirically analysis the dynamic evolution characteristics of the conversion efficiency of Green and Gold.Based on this,the heterogeneity improvement strategy is proposed.The results show that:(1)the comprehensive efficiency of the Two Mountains conversion in Zhangye City decreased first and then increased.The highest was 1.715 in 2007;the lowest was 1.367 in 2012;since 2012,the development has gradually improved.The main reason for the decrease in the comprehensive efficiency from 2007 to 2012 is the lower conversion efficiency in IIstage.(2)Spatial difference analysis shows that the areas with low the comprehensive efficiency were concentrated in Sunan,Minle,and Shandan Counties along the Qilian Mountains.The comprehensive efficiency was 0.406,0.489 and 0.482 respectively.The key to improving the comprehensive efficiency of Sunan County and Minle County is II-stage,while the focus of improving Shandan County is I-stage.(3)Redundancy analysis found that the main factor affecting the comprehensive efficiency of the Two Mountains conversion is insufficient output.In the future,we should focus on expanding effective pathways for the Two Mountains conversion and innovating institutional mechanisms for realizing ecological value.展开更多
During the past five decades, fluctuations of glaciers were reconstructed from historical documents, aerial photographs, and remote sensing data. From 1956 to 2003, 910 glaciers investigated had reduced in area by 21....During the past five decades, fluctuations of glaciers were reconstructed from historical documents, aerial photographs, and remote sensing data. From 1956 to 2003, 910 glaciers investigated had reduced in area by 21.7% of the 1956 value, with a mean reduction for the individual glacier of 0.10 km2. The relative area reductions of small glaciers were usually higher than those of large ones, which exhibited larger absolute loss, indicating that the small glaciers were more sensitive to climate change than large ones. Over the past -50 years, glacier area decreased by 29.6% in the Heihe （黑河） River basin and 18.7% in the Beidahe （北大河） River basin, which were the two regions investigated in the Middle Qilian （祁连） Mountain region. Compared with other areas of the Qilian Mountain region, the most dramatic glacier shrinkage had occurred in the Middle Qilian Mountain region, mainly resuiting from rapid rising temperatures. Regional differences in glacier area changes are related to local climate conditions, the relative proportion of glaciers in different size classes, and other factors.展开更多
Qilian Mountain permafrost, with area about 10×10^4 km2, locates in the north of Qinghai- Tibet plateau. It equips with perfect conditions and has great prospecting potential for gas hydrate. The Scientific Drill...Qilian Mountain permafrost, with area about 10×10^4 km2, locates in the north of Qinghai- Tibet plateau. It equips with perfect conditions and has great prospecting potential for gas hydrate. The Scientific Drilling Project of Gas Hydrate in Qilian Mountain permafrost, which locates in Juhugeng of Muri Coalfield, Tianjun County, Qinghai Province, has been implemented by China Geological Survey in 2008-2009. Four scientific drilling wells have been completed with a total footage of 2059.13 m. Samples of gas hydrate are collected separately from holes DK-1, DK-2 and DK-3. Gas hydrate is hosted under permafrost zone in the 133-396 m interval. The sample is white crystal and easily burning. Anomaly low temperature has been identified by the infrared camera. The gas hydratebearing cores strongly bubble in the water. Gas-bubble and water-drop are emitted from the hydratebearing cores and then characteristic of honeycombed structure is left. The typical spectrum curve of gas hydrate is detected using Raman spectrometry. Furthermore, the logging profile also indicates high electrical resistivity and sonic velocity. Gas hydrate in Qilian Mountain is characterized by a thinner permafrost zone, shallower buried depth, more complex gas component and coal-bed methane origin etc.展开更多
To investigate the diurnal variation of summer precipitation in the Qilian Mountains in the northeast Tibetan Plateau, the hourly precipitation amount for this region during the summers of 2008-2014 are analyzed using...To investigate the diurnal variation of summer precipitation in the Qilian Mountains in the northeast Tibetan Plateau, the hourly precipitation amount for this region during the summers of 2008-2014 are analyzed using an hourly merged precipitation product at 0.1°×0.1 ° resolution. The main results are as follows. （1） The spatial distribution and temporal variation of mean hourly precipitation amount and frequency are generally similar and hourly precipitations in the eastern and middle portions are larger and more frequent than that in the western portion. The high value area of precipitation intensity is obviously different from that of precipitation amount and frequency. （2） The spatial distribution of daytime precipitation is generally similar to that of nighttime precipitation, and the daytime precipitation is heavier than the nighttime precipitation. （3） The change rate of precipitation has a maximum at 20：00 Beijing time, and a minimum at 12：00. The hourly precipitation amount significantly correlated with frequency, especially for the middle and eastern portions.展开更多
The Lajishan orogenic belt is one of the E-W-trending Caledonian orogenicbelts within the Qinling-Qilian orogenic system. It was formed upon the Jiningian basement byintensive taphrogenesis. Its major characteristics ...The Lajishan orogenic belt is one of the E-W-trending Caledonian orogenicbelts within the Qinling-Qilian orogenic system. It was formed upon the Jiningian basement byintensive taphrogenesis. Its major characteristics comprise the prominent faulting along the northand south boundaries, the highly complicated petrological and petro-geochemical features of thevolcanic rock series, and the development of a new type of ophiolite suite. In terms of tectonicanalysis and the sequential analysis of tectonic settings of magmatic rocks, it is suggested thatthe Lajishan orogenic belt has undergone a complete 'opening-closing' cycle, which can be furtherdivided into 3 second-order 'opening-closing' cycles. The composite characteristics of the'opening-closing' movement show that Laji Mountain is a typical fault orogenic belt. The faultorogenic belt is one of the most important types of intracontinental orogens. It is of criticaltheoretical and practical significance to summarize the characteristics and the diagnostic criteriaof this kind of orogenic belts, and study the mechanism of their formation and build models of theirevolution.展开更多
The purpose of the present study was to survey contents of trace elements of Cu, Mn, Fe, and Zn in the surface layer （0-20 cm） in the soil, pasture and serum of sheep in Huangcheng area of Qilian mountain grassland,...The purpose of the present study was to survey contents of trace elements of Cu, Mn, Fe, and Zn in the surface layer （0-20 cm） in the soil, pasture and serum of sheep in Huangcheng area of Qilian mountain grassland, China. Also the soil-plantanimal continuum was analyzed. Soil （n=300）, pasture （n=60）, and blood serum samples from sheep （n=480） were collected from Huangcheng area of Qilian mountain grassland, China. The contents of trace element in the samples were analyzed by atomic absorption spectrophotometer after digestion. The soil trace elements density distribution shows a ladder-like pattern distribution. Equations developed in the present study for prediction of Fe （R2=0.943） and Zn （R2=0.882） had significant R2 values.展开更多
The Ordovician Laohushan ophiolite, located in the eastern part of the North Qilian Mountains, is mainly composed of meta-peridotites, gabbros and basalts alternating with sediments. The sediments are mainly turbidite...The Ordovician Laohushan ophiolite, located in the eastern part of the North Qilian Mountains, is mainly composed of meta-peridotites, gabbros and basalts alternating with sediments. The sediments are mainly turbidites, including sandstones, siltstones, cherts etc. Major elements show that the basalts are subalkaline tholeiites and may be analogous to ocean-floor basalts. Except a few N-MORBs, most of the basalts are E-MORBs as indicated by incompatible element ratios such as (La/Ce)N, La/Sm, Ce/Zr, Zr/Y and Zr/Nb. Negative Nb anomaly is common but negative Zr, Hf and Ti anomalies are quite rare. Based on the geochemical characteristics, it is suggested that the Laohushan basalts were formed in a back-arc basin. ENd (t) of the basalts ranges between +3.0 and +8.9 and (87Sr/86Sr), ranges between 0.7030 and 0.7060, indicating a depleted mantle source which was mixed with more or less enriched mantle components. Furthermore, the petrography of the sandstones and geochemistry of the cherts suggest that the sediments were deposited near a continental margin.展开更多
The soil properties in arid ecosystems are important determinants of vegetation distribution patterns. Soil organic carbon （SOC） content, which is closely related to soil types and the holding capacities of soil wat...The soil properties in arid ecosystems are important determinants of vegetation distribution patterns. Soil organic carbon （SOC） content, which is closely related to soil types and the holding capacities of soil water and nutrients, exhibits complex variability in arid desert grasslands; thus, it is essentially an impact factor for the distri- bution pattern of desert grasslands. In the present study, an investigation was conducted to estimate the spatial pattern of SOC content in desert grasslands and the association with environmental factors in the diluvial-alluvial plains of northern Qilian Mountains. The results showed that the mean values of SOC ranged from 2.76 to 5.80 g/kg in the soil profiles, and decreased with soil depths. The coefficients of variation （CV） of the SOC were high （ranging from 48.83% to 94.67%）, which indicated a strong spatial variability. SOC in the desert grasslands of the study re- gion presented a regular spatial distribution, which increased gradually from the northwest to the southeast. The SOC distribution had a pattern linked to elevation, which may be related to the gradient of climate conditions. Soil type and plant community significantly affected the SOC. The SOC had a significant positive relationship with soil moisture （P〈0.05）; whereas, it had a more significant negative relationship with the soil bulk density （BD） （P〈0.01）. However, a number of the variations in the SOC could be explained not by the environmental factors involved in this analysis, but rather other factors （such as grazing activity and landscape）. The results provide important references for soil carbon storage estimation in this study region. In addition, the SOC association with environmental variables also provides a basis for a sustainable use of the limited grassland resources in the diluvial-alluvial plains of north- ern Qilian Mountains.展开更多
We present a composite tree-ring chronology from two sites of Qilian Juniper （Sabina przewalskii） in the northwestern Qilian Mountains （QM）, Northwestern China. Precipitation in June was found to be the main limit...We present a composite tree-ring chronology from two sites of Qilian Juniper （Sabina przewalskii） in the northwestern Qilian Mountains （QM）, Northwestern China. Precipitation in June was found to be the main limiting factor for tree-growth. The tree rings are also significantly and positively correlated with June precipitation over large areas of the northern Tibetan Plateau （TP）. The authors thus consider that the treering based drought reconstruction from 1803-2006 is representative of a large area drought history. During the reconstruction period, persistent and severe dry epochs occurred in the 1820s-1830s, 1870s-1880s, 1920s, and 1950s 1960s, and persistent wet periods were found from 1803-1810s, 1890s-1920s, and 1970s-1980s. The severe dry and wet periods are similar to those found over the northeastern TP, indicating the potential linkages of the drought regimes between them. Comparison with global SST indicates that the drought variability is closely related to the tropical Pacific and Arctic Ocean SSTs, suggesting the connection of regional moisture variations to the Asian monsoon and westerly belt circulations, respectively.展开更多
The Late Caledonian to Early Hercynian North Qilian orogenic belt in no rthwestern China is an elongate tectonic unit situated between the North China p late in the north and the Qaidam plate in the south. North Qili...The Late Caledonian to Early Hercynian North Qilian orogenic belt in no rthwestern China is an elongate tectonic unit situated between the North China p late in the north and the Qaidam plate in the south. North Qilian started in the latest Proterozoic to Cambrian as a rift basin on the southern margin of North China, and evolved later to an archipelagic ocean and active continental margin during the Ordovician and a foreland basin from Silurian to the Early and Middle Devonian. The Early Silurian flysch and submarine alluvial fan, the Middle to L ate Silurian shallow marine to tidal flat deposits and the Early and Middle Devo nian terrestrial molasse are developed along the corridor Nanshan. The shallowin g upward succession from subabyssal flysch, shallow marine, tidal flat to terre strial molasse and its gradually narrowed regional distribution demonstrate that the foreland basin experienced the transition from flysch stage to molasse stag e during the Silurian and Devonian time.展开更多
Shrublands serve as an important component of terrestrial ecosystems, and play an important role in structure and functions of alpine ecosystem.Accurate estimation of biomass is critical to examination of the producti...Shrublands serve as an important component of terrestrial ecosystems, and play an important role in structure and functions of alpine ecosystem.Accurate estimation of biomass is critical to examination of the productivity of alpine ecosystems, due to shrubification under climate change in past decades.In this study, 14 experimental plots and 42 quadrates of the shrubs Potentilla fruticosa and Caragana jubata were selected along altitudes gradients from 3220 to 3650 m a.s.l.(above sea level) on semi-sunny and semi-shady slope in Hulu watershed of Qilian Mountains, China.The foliage, woody component and total aboveground biomass per quadrate were examined using a selective destructive method, then the biomass were estimated via allometric equations based on measured parameters for two shrub species.The results showed that C.jubata accounted for 1–3 times more biomass(480.98 g/m2) than P.fruticosa(191.21 g/m2).The aboveground biomass of both the shrubs varied significantly with altitudinal gradient(P<0.05).Woody component accounted for the larger proportion than foliage component in the total aboveground biomass.The biomass on semi-sunnyslopes(200.27 g/m2 and 509.07 g/m2) was greater than on semi-shady slopes(182.14 g/m2 and 452.89g/m2) at the same altitude band for P.fruticosa and C.jubata.In contrast, the foliage biomass on semi-shady slopes(30.50 g/m2) was greater than on semi-sunny slopes(27.51 g/m2) for two shrubs.Biomass deceased with increasing altitude for P.fruticosa, whereas C.jubata showed a hump-shaped pattern with altitude.Allometric equations were obtained from the easily descriptive parameters of height(H), basal diameter(D) and crown area(C) for biomass of C.jubata and P.fruticosa.Although the equations type and variables comprising of the best model varied among the species, all equations related to biomass were significant(P < 0.005), with determination coefficients(R2) ranging from 0.81 to 0.96.The allometric equations satisfied the requirements of the model, and can be used to estimate the regional scale biomass of P.fruticosa and C.jubata in alpine ecosystems of the Qilian Mountains.展开更多
Abstract: This paper discusses in detail the deformation textures, glide system, petrofabrics and olivine dislocation microstructures of mantle peridotites at Yushigou in the North Qilian Mountains, northwestern China...Abstract: This paper discusses in detail the deformation textures, glide system, petrofabrics and olivine dislocation microstructures of mantle peridotites at Yushigou in the North Qilian Mountains, northwestern China. The peridotites have undergone high-pressure, high-temperature and low-strain rate plastic flow deformation. According to the dynamic recrystallized-grain size of olivine and the average spacing between the dislocation walls as well as the chemical composition of enstatite, the authors calculated the rheological parameters of the ancient upper mantle in the study area as follows: temperatures 1025–1093°C; pressures 3043–4278 MPa; depths 95–132 km; deviatoric stress 28–32 MPa; strain rates 0.2×10?14-2.13×10?14s?1 and equivalent viscosities 0.45×1020-4.65×1020 Pa ? s. These parameters suggest that the position where plastic flow took place was correspondent to the lowvelocity zone beneath the oceanic lithosphere and that oceanization characterized by middle-velocity (1–3 cm/a) sea-floor spreading took place in the North Qilian Mountains during the Early Palaeozoic.展开更多
The net accumulation record of ice core is one of the most reliable indicators for reconstructing precipitation changes in high mountains. A 20.12 m ice core was drilled in 2006 from the accumulation zone of Laohugou ...The net accumulation record of ice core is one of the most reliable indicators for reconstructing precipitation changes in high mountains. A 20.12 m ice core was drilled in 2006 from the accumulation zone of Laohugou Glacier No.12 in the northeastern Tibetan Plateau, China. We obtained the precipitation from the ice core net accumulation during 1960-2006, and found out the relationship between Laohugou ice core record and other data from surrounding sites of the northeastern Tibetan Plateau. Results showed that during 1960-2006, the precipitation in the high mountains showed firstly an increasing trend, while during 1980 to 2006 it showed an obvious decreasing trend. Reconstructed precipitation change in the Laohugou glacier basin was consistent with the measured data from the nearby weather stations in the lower mountain of Subei, and the correlation coefficient was 0.619 （P〈0.001）. However, the precipitation in the high mountain was about 3 times more than that of the lower mountain. The precipitation in Laohugou Glacier No.12 of the western Qilian Mountains corresponded well to the net accumulation of Dunde ice core during the same period, tree-ring reconstructed precipitation, the measured data of multiple meteorological stations in the northeastern Tibetan Plateau, and also the changes of adjacent PDSI drought index. Precipitation changes of the Laohugou glacier basin and other sites of the northeastern Tibetan Plateau had significantly positive correlation with ENSO, which implied that the regional alpine precipitation change was very likely to be influenced by ENSO.展开更多
In June 2006, samples were collected from a 90 cm snow-pit at an elevation of 5 040 m a.s.l, in the northern branch firn basin of the Glacier No. 12, Laohugou Valley, in the western part of Qilian Mountain, China. Oxy...In June 2006, samples were collected from a 90 cm snow-pit at an elevation of 5 040 m a.s.l, in the northern branch firn basin of the Glacier No. 12, Laohugou Valley, in the western part of Qilian Mountain, China. Oxygen isotopes （6180） and major soluble ions were measured. Results showed that Ca2＋ is the dominant cation, and SO42 is the dominant anion. All major ions have close positive correlations with eachother except NO3 and NH4＋. 6180 show positive correlation with air temperature. The method of correlation analysis, sea-salt ion tracer and trend analysis were used to determine the source of the chemical components. The correlation analysis and HYSPLIT backward trajectory analysis suggest that atmospheric soluble dust species dominate the chemical signature.展开更多
Based on a 0.5°×0.5° daily gridded precipitation dataset and observations in mete- orological stations released by the National Meteorological Information Center, the interan- nual variation of areal pr...Based on a 0.5°×0.5° daily gridded precipitation dataset and observations in mete- orological stations released by the National Meteorological Information Center, the interan- nual variation of areal precipitation in the Qilian Mountains during 1961-2012 is investigated using principal component analysis （PCA） and regression analysis, and the relationship be- tween areal precipitation and drought accumulation intensity is also analyzed. The results indicate that the spatial distribution of precipitation in the Qilian Mountains can be well re- flected by the gridded dataset. The gridded data-based precipitation in mountainous region is generally larger than that in plain region, and the eastern section of the mountain range usu- ally has more precipitation than the western section. The annual mean areal precipitation in the Qilian Mountains is 724.9×108 m3, and the seasonal means in spring, summer, autumn and winter are 118.9×108 m3, 469.4×108 m3, 122.5×108 m3 and 14.1×108 m3, respectively. Summer is a season with the largest areal precipitation among the four seasons, and the proportion in summer is approximately 64.76%. The areal precipitation in summer, autumn and winter shows increasing trends, but a decreasing trend is seen in spring. Among the four seasons, summer have the largest trend magnitude of 1.7×108 m3-a-1. The correlation be- tween areal precipitation in the mountainous region and dry-wet conditions in the mountains and the surroundings can be well exhibited. There is a negative correlation between drought accumulation intensity and the larger areal precipitation is consistent with the weaker drought intensity for this region.展开更多
The Qilian mountain area was examined for using the Logistic-CA-Markov coupling model combined with GIS spatial analyst technology to research the transformation of LUCC, driving force system and simulate future tende...The Qilian mountain area was examined for using the Logistic-CA-Markov coupling model combined with GIS spatial analyst technology to research the transformation of LUCC, driving force system and simulate future tendency of variation. Results show that： （1） Woodland area decreased by 12.55%, while grassland, cultivated land, and settlement areas increased by 0.22%, 7.92%, and 0.03%, respectively, from 1986 to 2014. During the period of 1986 to 2000, forest degradation in the middle section of the mountain area decreased by 1,501.69 km2. Vegetation cover area improved, with a net increase of grassland area of 38.12 km2 from 2000 to 2014. （2） For constructing the system driving force, the best simulation scale was 210m×210m. Based on logistic regression analysis, the contribution （weight） of composite driving forces to land use and cover change was obtained, and the weight value was more objectively compared with AHP and MCE method. （3） In the natural scenarios, it is predicted that land use and cover distribution maps of Qilian mountain area in 2028 and 2042, and the Lee-Sallee index test was adopted. Over the next 27 years （2015-2042）, farmland, woodland, grassland, settlement areas show an increasing trend, especially settlements with an obvious change of 0.56%. The area of bare land will decrease by 0.89%. Without environmental degradation, tremendous structural change of LUCC will not occur, and typical characteristic of the vertical zone of the mountain would remain. Farmland and settlement areas will increase, but only in the vicinity of Qilian and Sunan counties.展开更多
The objective of this study is to investigate pollen-vegetation relationship in the Qilian Mountains. The eastern Qilian Mountains are located in the transitional zone of the Tibetan Plateau, the Loess Plateau and the...The objective of this study is to investigate pollen-vegetation relationship in the Qilian Mountains. The eastern Qilian Mountains are located in the transitional zone of the Tibetan Plateau, the Loess Plateau and the arid region of Northwest China; which is one of the key areas of global environmental change. A total of 13 surface pollen samples from main vegetation have been collected. Pollen percentages were calculated in all samples. In order to reveal the relationship between pollen composition and the vegetation types from which the soil samples have been collected, Detrended Correspondence Analysis （DCA） ordination method was employed on the pollen data. The results show that dominating vegetation types can be recognized by their pollen spectra： Picea crassifolia forest, alpine shrub and alpine meadow as well. Altitude and temperature determine the distribution of the surface pollen and the vegetation. The good agreement between modern vegetation and surface samples across this area provides a measure of the reliability of using pollen data to reconstruct paleoenvironment and paleovegetation patterns in this or other similar regions. However the loss of Betula pollen in forest needs further investigation. Pollen oxidation is the most important factor contributing to the damage of modern pollen in the study area. Pollen concentrations decrease with the increase of pH values of soils, and decrease sharply when the pH exceeds 7.6.展开更多
Zircons from granodiorite and biotite granite in the Yeniutan granitic intrusion in the western North Qilian Mountains yielded a weighted mean 206Pb/238U apparent age of 460±3 Ma, suggesting that the intrusion or...Zircons from granodiorite and biotite granite in the Yeniutan granitic intrusion in the western North Qilian Mountains yielded a weighted mean 206Pb/238U apparent age of 460±3 Ma, suggesting that the intrusion originated during the late stage of plate subduction. Its related Ta'ergou and Xiaoliugou deposits are two of the few large tungsten deposits formed in the plate subduction environment in the world. The U-Pb dating of the zircons from the biotite granite gave a discordant lower intercept age of 183±4 Ma, which implies that the Yanshanian event was probably superimposed on the North Qilian region.展开更多
基金financially supported by the National Natural Science Foundation of China(No.41621001)。
文摘Air temperature is an important indicator to analyze climate change in mountainous areas.ERA5 reanalysis air temperature data are important products that were widely used to analyze temperature change in mountainous areas.However,the reliability of ERA5 reanalysis air temperature over the Qilian Mountains(QLM)is unclear.In this study,we evaluated the reliability of ERA5 monthly averaged reanalysis 2 m air temperature data using the observations at 17 meteorological stations in the QLM from 1979 to 2017.The results showed that:ERA5 reanalysis monthly averaged air temperature data have a good applicability in the QLM in general(R2=0.99).ERA5 reanalysis temperature data overestimated the observed temperature in the QLM in general.Root mean square error(RMSE)increases with the increasing of elevation range,showing that the reliability of ERA5 reanalysis temperature data is worse in higher elevation than that in lower altitude.ERA5 reanalysis temperature can capture observational warming rates well.All the smallest warming rates of observational temperature and ERA5 reanalysis temperature are found in winter,with the warming rates of 0.393°C/10a and 0.360°C/10a,respectively.This study will provide a reference for the application of ERA5 reanalysis monthly averaged air temperature data at different elevation ranges in the Qilian Mountains.
基金supported by the National Natural Science Foundation of China(Grant Nos.42475100 and 42405091)supported by the CMA Key Innovation Team(Grant No.CMA2022ZD10)+1 种基金the CMA Weather Modification Centre Innovation Team(Grant No.WMC2023IT02)the National Key R&D Program of China(Grant No.2019YFC1510305).
文摘The ice-phase microphysical characteristics of a stratiform cloud system over the Qilian Mountains in northwestern China on 15 September 2022 were analyzed via aircraft data.The stratiform cloud system developed under southwesterly flows at 500 hPa and was affected locally by topography.Synoptic features and aircraft observations revealed strengthened cloud development on the leeward slope.The ice particle habits and microphysical processes at heights of 6-8 km were investigated.The cloud system was characterized by extremely low supercooled liquid water content at temperatures between−4℃ and−17℃.The ice particle concentrations ranged predominantly from 10 to 30 L^(−1),corresponding to ice water content ranging from 0.01 to 0.05 g m^(−3).Active ice aggregation was observed at temperatures colder than−10°C.The windward side of the cloud system exhibited weaker development and two distinct cloud layers.Intense orographic uplift on the leeward slope enhanced ice particle aggregation.The clouds on the leeside presented lower ice particle concentrations but larger sizes than those on the windward side.The influence of aggregation on the ice particle size distribution was reflected in two main aspects.One aspect was the bimodal spectra at−16℃,with the first peak at 125μm and subpeak at 400-500μm;the other was the broadened size spectra at−13℃ due to significant aggregation of dendrites.
基金funded by National Natural Science Foundation of China(Grant No.:42461046)the Postdoctoral Science Foundation of China(Grant No.:2020M673641XB).
文摘The research on the conversion efficiency of"Green Mountains into Clear Water"(Green)and"Gold and silver Mountains"(Gold)is of great significance to promote the coordination between natural resource conservation in national park and the local economic and social development.This paper pays attention to the linking role of ecosystem services in different stages of the conversion process between the Green and Gold.Based on the twostage division,this paper constructs the accounting framework for conversion efficiency of Green and Gold.That is,the comprehensive conversion efficiency of Green and Gold is decomposed into the I-stage efficiency of ecological inputs conversion to Green and the II-stage efficiency of ecosystem services conversion to economic output.Furthermore,the Qilian Mountain National Park in China and its surrounding area Zhangye City,is taken as an example.Using a two-stage non-oriented super-efficiency network EBM model and panel data from 2007 to 2018 to empirically analysis the dynamic evolution characteristics of the conversion efficiency of Green and Gold.Based on this,the heterogeneity improvement strategy is proposed.The results show that:(1)the comprehensive efficiency of the Two Mountains conversion in Zhangye City decreased first and then increased.The highest was 1.715 in 2007;the lowest was 1.367 in 2012;since 2012,the development has gradually improved.The main reason for the decrease in the comprehensive efficiency from 2007 to 2012 is the lower conversion efficiency in IIstage.(2)Spatial difference analysis shows that the areas with low the comprehensive efficiency were concentrated in Sunan,Minle,and Shandan Counties along the Qilian Mountains.The comprehensive efficiency was 0.406,0.489 and 0.482 respectively.The key to improving the comprehensive efficiency of Sunan County and Minle County is II-stage,while the focus of improving Shandan County is I-stage.(3)Redundancy analysis found that the main factor affecting the comprehensive efficiency of the Two Mountains conversion is insufficient output.In the future,we should focus on expanding effective pathways for the Two Mountains conversion and innovating institutional mechanisms for realizing ecological value.
基金supported by the National Basic Research Program of China (Nos. 2010CB951003 and 2007CB411501)the National Natural Science Foundation of China (Nos. 91025012 and J0930003/J0109)
文摘During the past five decades, fluctuations of glaciers were reconstructed from historical documents, aerial photographs, and remote sensing data. From 1956 to 2003, 910 glaciers investigated had reduced in area by 21.7% of the 1956 value, with a mean reduction for the individual glacier of 0.10 km2. The relative area reductions of small glaciers were usually higher than those of large ones, which exhibited larger absolute loss, indicating that the small glaciers were more sensitive to climate change than large ones. Over the past -50 years, glacier area decreased by 29.6% in the Heihe （黑河） River basin and 18.7% in the Beidahe （北大河） River basin, which were the two regions investigated in the Middle Qilian （祁连） Mountain region. Compared with other areas of the Qilian Mountain region, the most dramatic glacier shrinkage had occurred in the Middle Qilian Mountain region, mainly resuiting from rapid rising temperatures. Regional differences in glacier area changes are related to local climate conditions, the relative proportion of glaciers in different size classes, and other factors.
文摘Qilian Mountain permafrost, with area about 10×10^4 km2, locates in the north of Qinghai- Tibet plateau. It equips with perfect conditions and has great prospecting potential for gas hydrate. The Scientific Drilling Project of Gas Hydrate in Qilian Mountain permafrost, which locates in Juhugeng of Muri Coalfield, Tianjun County, Qinghai Province, has been implemented by China Geological Survey in 2008-2009. Four scientific drilling wells have been completed with a total footage of 2059.13 m. Samples of gas hydrate are collected separately from holes DK-1, DK-2 and DK-3. Gas hydrate is hosted under permafrost zone in the 133-396 m interval. The sample is white crystal and easily burning. Anomaly low temperature has been identified by the infrared camera. The gas hydratebearing cores strongly bubble in the water. Gas-bubble and water-drop are emitted from the hydratebearing cores and then characteristic of honeycombed structure is left. The typical spectrum curve of gas hydrate is detected using Raman spectrometry. Furthermore, the logging profile also indicates high electrical resistivity and sonic velocity. Gas hydrate in Qilian Mountain is characterized by a thinner permafrost zone, shallower buried depth, more complex gas component and coal-bed methane origin etc.
基金National Natural Science Foundation of China, No.41461003 National Basic Research Program of China （973 Program）, No.2013CBA01801
文摘To investigate the diurnal variation of summer precipitation in the Qilian Mountains in the northeast Tibetan Plateau, the hourly precipitation amount for this region during the summers of 2008-2014 are analyzed using an hourly merged precipitation product at 0.1°×0.1 ° resolution. The main results are as follows. （1） The spatial distribution and temporal variation of mean hourly precipitation amount and frequency are generally similar and hourly precipitations in the eastern and middle portions are larger and more frequent than that in the western portion. The high value area of precipitation intensity is obviously different from that of precipitation amount and frequency. （2） The spatial distribution of daytime precipitation is generally similar to that of nighttime precipitation, and the daytime precipitation is heavier than the nighttime precipitation. （3） The change rate of precipitation has a maximum at 20：00 Beijing time, and a minimum at 12：00. The hourly precipitation amount significantly correlated with frequency, especially for the middle and eastern portions.
基金the Doctoral Programme of Higher Education 97049119 the National Natural Science Foundation of China grant 40072062.
文摘The Lajishan orogenic belt is one of the E-W-trending Caledonian orogenicbelts within the Qinling-Qilian orogenic system. It was formed upon the Jiningian basement byintensive taphrogenesis. Its major characteristics comprise the prominent faulting along the northand south boundaries, the highly complicated petrological and petro-geochemical features of thevolcanic rock series, and the development of a new type of ophiolite suite. In terms of tectonicanalysis and the sequential analysis of tectonic settings of magmatic rocks, it is suggested thatthe Lajishan orogenic belt has undergone a complete 'opening-closing' cycle, which can be furtherdivided into 3 second-order 'opening-closing' cycles. The composite characteristics of the'opening-closing' movement show that Laji Mountain is a typical fault orogenic belt. The faultorogenic belt is one of the most important types of intracontinental orogens. It is of criticaltheoretical and practical significance to summarize the characteristics and the diagnostic criteriaof this kind of orogenic belts, and study the mechanism of their formation and build models of theirevolution.
基金The financial supports are greatly appreciated from the Central Public-interest Scientific Institution Basal Research Fund of China(1610322013003)the Agriculture Achievements Transformation Fund Project of the Ministry of Science and Technology of China(2010GB23260564)
文摘The purpose of the present study was to survey contents of trace elements of Cu, Mn, Fe, and Zn in the surface layer （0-20 cm） in the soil, pasture and serum of sheep in Huangcheng area of Qilian mountain grassland, China. Also the soil-plantanimal continuum was analyzed. Soil （n=300）, pasture （n=60）, and blood serum samples from sheep （n=480） were collected from Huangcheng area of Qilian mountain grassland, China. The contents of trace element in the samples were analyzed by atomic absorption spectrophotometer after digestion. The soil trace elements density distribution shows a ladder-like pattern distribution. Equations developed in the present study for prediction of Fe （R2=0.943） and Zn （R2=0.882） had significant R2 values.
文摘The Ordovician Laohushan ophiolite, located in the eastern part of the North Qilian Mountains, is mainly composed of meta-peridotites, gabbros and basalts alternating with sediments. The sediments are mainly turbidites, including sandstones, siltstones, cherts etc. Major elements show that the basalts are subalkaline tholeiites and may be analogous to ocean-floor basalts. Except a few N-MORBs, most of the basalts are E-MORBs as indicated by incompatible element ratios such as (La/Ce)N, La/Sm, Ce/Zr, Zr/Y and Zr/Nb. Negative Nb anomaly is common but negative Zr, Hf and Ti anomalies are quite rare. Based on the geochemical characteristics, it is suggested that the Laohushan basalts were formed in a back-arc basin. ENd (t) of the basalts ranges between +3.0 and +8.9 and (87Sr/86Sr), ranges between 0.7030 and 0.7060, indicating a depleted mantle source which was mixed with more or less enriched mantle components. Furthermore, the petrography of the sandstones and geochemistry of the cherts suggest that the sediments were deposited near a continental margin.
基金Strategic Priority Research Program of the Chinese Academy of Sciences (XDA05050406-3)National Natural Science Foundation of China (41201284 and 91125022)
文摘The soil properties in arid ecosystems are important determinants of vegetation distribution patterns. Soil organic carbon （SOC） content, which is closely related to soil types and the holding capacities of soil water and nutrients, exhibits complex variability in arid desert grasslands; thus, it is essentially an impact factor for the distri- bution pattern of desert grasslands. In the present study, an investigation was conducted to estimate the spatial pattern of SOC content in desert grasslands and the association with environmental factors in the diluvial-alluvial plains of northern Qilian Mountains. The results showed that the mean values of SOC ranged from 2.76 to 5.80 g/kg in the soil profiles, and decreased with soil depths. The coefficients of variation （CV） of the SOC were high （ranging from 48.83% to 94.67%）, which indicated a strong spatial variability. SOC in the desert grasslands of the study re- gion presented a regular spatial distribution, which increased gradually from the northwest to the southeast. The SOC distribution had a pattern linked to elevation, which may be related to the gradient of climate conditions. Soil type and plant community significantly affected the SOC. The SOC had a significant positive relationship with soil moisture （P〈0.05）; whereas, it had a more significant negative relationship with the soil bulk density （BD） （P〈0.01）. However, a number of the variations in the SOC could be explained not by the environmental factors involved in this analysis, but rather other factors （such as grazing activity and landscape）. The results provide important references for soil carbon storage estimation in this study region. In addition, the SOC association with environmental variables also provides a basis for a sustainable use of the limited grassland resources in the diluvial-alluvial plains of north- ern Qilian Mountains.
基金supported by the National Natural Science Foundation of China In-novation Team Project(Grant No.40721061)the Na-tional Natural Science Foundation of China(Grant Nos.40671191 and 90502008)+1 种基金the Chinese 111 Project(Grant No.B06026)the One Hundred Talents Program of CAS(Grant No.29O827B11)
文摘We present a composite tree-ring chronology from two sites of Qilian Juniper （Sabina przewalskii） in the northwestern Qilian Mountains （QM）, Northwestern China. Precipitation in June was found to be the main limiting factor for tree-growth. The tree rings are also significantly and positively correlated with June precipitation over large areas of the northern Tibetan Plateau （TP）. The authors thus consider that the treering based drought reconstruction from 1803-2006 is representative of a large area drought history. During the reconstruction period, persistent and severe dry epochs occurred in the 1820s-1830s, 1870s-1880s, 1920s, and 1950s 1960s, and persistent wet periods were found from 1803-1810s, 1890s-1920s, and 1970s-1980s. The severe dry and wet periods are similar to those found over the northeastern TP, indicating the potential linkages of the drought regimes between them. Comparison with global SST indicates that the drought variability is closely related to the tropical Pacific and Arctic Ocean SSTs, suggesting the connection of regional moisture variations to the Asian monsoon and westerly belt circulations, respectively.
基金TheresearchissponsoredbytheNationalNaturalScienceFoundationofChina (No .4 9972 0 78)
文摘The Late Caledonian to Early Hercynian North Qilian orogenic belt in no rthwestern China is an elongate tectonic unit situated between the North China p late in the north and the Qaidam plate in the south. North Qilian started in the latest Proterozoic to Cambrian as a rift basin on the southern margin of North China, and evolved later to an archipelagic ocean and active continental margin during the Ordovician and a foreland basin from Silurian to the Early and Middle Devonian. The Early Silurian flysch and submarine alluvial fan, the Middle to L ate Silurian shallow marine to tidal flat deposits and the Early and Middle Devo nian terrestrial molasse are developed along the corridor Nanshan. The shallowin g upward succession from subabyssal flysch, shallow marine, tidal flat to terre strial molasse and its gradually narrowed regional distribution demonstrate that the foreland basin experienced the transition from flysch stage to molasse stag e during the Silurian and Devonian time.
基金funded by the National Natural Science Foundation of China(Grant Nos.91025011,91125013,41222001)the Project for Incubation of Specialists in Glaciology and Geocryology of National Natural Science Foundation of China(J1210003/J0109)
文摘Shrublands serve as an important component of terrestrial ecosystems, and play an important role in structure and functions of alpine ecosystem.Accurate estimation of biomass is critical to examination of the productivity of alpine ecosystems, due to shrubification under climate change in past decades.In this study, 14 experimental plots and 42 quadrates of the shrubs Potentilla fruticosa and Caragana jubata were selected along altitudes gradients from 3220 to 3650 m a.s.l.(above sea level) on semi-sunny and semi-shady slope in Hulu watershed of Qilian Mountains, China.The foliage, woody component and total aboveground biomass per quadrate were examined using a selective destructive method, then the biomass were estimated via allometric equations based on measured parameters for two shrub species.The results showed that C.jubata accounted for 1–3 times more biomass(480.98 g/m2) than P.fruticosa(191.21 g/m2).The aboveground biomass of both the shrubs varied significantly with altitudinal gradient(P<0.05).Woody component accounted for the larger proportion than foliage component in the total aboveground biomass.The biomass on semi-sunnyslopes(200.27 g/m2 and 509.07 g/m2) was greater than on semi-shady slopes(182.14 g/m2 and 452.89g/m2) at the same altitude band for P.fruticosa and C.jubata.In contrast, the foliage biomass on semi-shady slopes(30.50 g/m2) was greater than on semi-sunny slopes(27.51 g/m2) for two shrubs.Biomass deceased with increasing altitude for P.fruticosa, whereas C.jubata showed a hump-shaped pattern with altitude.Allometric equations were obtained from the easily descriptive parameters of height(H), basal diameter(D) and crown area(C) for biomass of C.jubata and P.fruticosa.Although the equations type and variables comprising of the best model varied among the species, all equations related to biomass were significant(P < 0.005), with determination coefficients(R2) ranging from 0.81 to 0.96.The allometric equations satisfied the requirements of the model, and can be used to estimate the regional scale biomass of P.fruticosa and C.jubata in alpine ecosystems of the Qilian Mountains.
基金This research was supported by the National Natural Science Foundation of China grant 49372136.
文摘Abstract: This paper discusses in detail the deformation textures, glide system, petrofabrics and olivine dislocation microstructures of mantle peridotites at Yushigou in the North Qilian Mountains, northwestern China. The peridotites have undergone high-pressure, high-temperature and low-strain rate plastic flow deformation. According to the dynamic recrystallized-grain size of olivine and the average spacing between the dislocation walls as well as the chemical composition of enstatite, the authors calculated the rheological parameters of the ancient upper mantle in the study area as follows: temperatures 1025–1093°C; pressures 3043–4278 MPa; depths 95–132 km; deviatoric stress 28–32 MPa; strain rates 0.2×10?14-2.13×10?14s?1 and equivalent viscosities 0.45×1020-4.65×1020 Pa ? s. These parameters suggest that the position where plastic flow took place was correspondent to the lowvelocity zone beneath the oceanic lithosphere and that oceanization characterized by middle-velocity (1–3 cm/a) sea-floor spreading took place in the North Qilian Mountains during the Early Palaeozoic.
基金National Natural Science Foundation of China, No.41371091 No.41201067+1 种基金 No.41301064 National Basic Research Program of China, No.2013CBA01801
文摘The net accumulation record of ice core is one of the most reliable indicators for reconstructing precipitation changes in high mountains. A 20.12 m ice core was drilled in 2006 from the accumulation zone of Laohugou Glacier No.12 in the northeastern Tibetan Plateau, China. We obtained the precipitation from the ice core net accumulation during 1960-2006, and found out the relationship between Laohugou ice core record and other data from surrounding sites of the northeastern Tibetan Plateau. Results showed that during 1960-2006, the precipitation in the high mountains showed firstly an increasing trend, while during 1980 to 2006 it showed an obvious decreasing trend. Reconstructed precipitation change in the Laohugou glacier basin was consistent with the measured data from the nearby weather stations in the lower mountain of Subei, and the correlation coefficient was 0.619 （P〈0.001）. However, the precipitation in the high mountain was about 3 times more than that of the lower mountain. The precipitation in Laohugou Glacier No.12 of the western Qilian Mountains corresponded well to the net accumulation of Dunde ice core during the same period, tree-ring reconstructed precipitation, the measured data of multiple meteorological stations in the northeastern Tibetan Plateau, and also the changes of adjacent PDSI drought index. Precipitation changes of the Laohugou glacier basin and other sites of the northeastern Tibetan Plateau had significantly positive correlation with ENSO, which implied that the regional alpine precipitation change was very likely to be influenced by ENSO.
基金supported by the Foundation for Excellent Youth Scholars of CAREERI, CAS (No. 51Y25B01)the National Natural Science Foundation of China (No. 41301064)the National Basic Research Program of China (No. 2007CB411501)
文摘In June 2006, samples were collected from a 90 cm snow-pit at an elevation of 5 040 m a.s.l, in the northern branch firn basin of the Glacier No. 12, Laohugou Valley, in the western part of Qilian Mountain, China. Oxygen isotopes （6180） and major soluble ions were measured. Results showed that Ca2＋ is the dominant cation, and SO42 is the dominant anion. All major ions have close positive correlations with eachother except NO3 and NH4＋. 6180 show positive correlation with air temperature. The method of correlation analysis, sea-salt ion tracer and trend analysis were used to determine the source of the chemical components. The correlation analysis and HYSPLIT backward trajectory analysis suggest that atmospheric soluble dust species dominate the chemical signature.
基金National Natural Science Foundation of China,No.41461003National Basic Research Program of China(973Program),No.2013CBA01801
文摘Based on a 0.5°×0.5° daily gridded precipitation dataset and observations in mete- orological stations released by the National Meteorological Information Center, the interan- nual variation of areal precipitation in the Qilian Mountains during 1961-2012 is investigated using principal component analysis （PCA） and regression analysis, and the relationship be- tween areal precipitation and drought accumulation intensity is also analyzed. The results indicate that the spatial distribution of precipitation in the Qilian Mountains can be well re- flected by the gridded dataset. The gridded data-based precipitation in mountainous region is generally larger than that in plain region, and the eastern section of the mountain range usu- ally has more precipitation than the western section. The annual mean areal precipitation in the Qilian Mountains is 724.9×108 m3, and the seasonal means in spring, summer, autumn and winter are 118.9×108 m3, 469.4×108 m3, 122.5×108 m3 and 14.1×108 m3, respectively. Summer is a season with the largest areal precipitation among the four seasons, and the proportion in summer is approximately 64.76%. The areal precipitation in summer, autumn and winter shows increasing trends, but a decreasing trend is seen in spring. Among the four seasons, summer have the largest trend magnitude of 1.7×108 m3-a-1. The correlation be- tween areal precipitation in the mountainous region and dry-wet conditions in the mountains and the surroundings can be well exhibited. There is a negative correlation between drought accumulation intensity and the larger areal precipitation is consistent with the weaker drought intensity for this region.
基金supported by National Natural Science Foundation of China (No. 4961038)Natural Science Foundation of Sichuan Province Education Department (No. 16ZB0402)+1 种基金Engineering and Technical College of Chengdu University of Technology Foundation (No. C122014014)the key research projects of Science and Technology Bureau of Leshan Town
文摘The Qilian mountain area was examined for using the Logistic-CA-Markov coupling model combined with GIS spatial analyst technology to research the transformation of LUCC, driving force system and simulate future tendency of variation. Results show that： （1） Woodland area decreased by 12.55%, while grassland, cultivated land, and settlement areas increased by 0.22%, 7.92%, and 0.03%, respectively, from 1986 to 2014. During the period of 1986 to 2000, forest degradation in the middle section of the mountain area decreased by 1,501.69 km2. Vegetation cover area improved, with a net increase of grassland area of 38.12 km2 from 2000 to 2014. （2） For constructing the system driving force, the best simulation scale was 210m×210m. Based on logistic regression analysis, the contribution （weight） of composite driving forces to land use and cover change was obtained, and the weight value was more objectively compared with AHP and MCE method. （3） In the natural scenarios, it is predicted that land use and cover distribution maps of Qilian mountain area in 2028 and 2042, and the Lee-Sallee index test was adopted. Over the next 27 years （2015-2042）, farmland, woodland, grassland, settlement areas show an increasing trend, especially settlements with an obvious change of 0.56%. The area of bare land will decrease by 0.89%. Without environmental degradation, tremendous structural change of LUCC will not occur, and typical characteristic of the vertical zone of the mountain would remain. Farmland and settlement areas will increase, but only in the vicinity of Qilian and Sunan counties.
基金National Key Project for Basic Research on Tibetan Plateau, No.2005CB422004 Knowledge Innovation Project of CAS, No.KZCX3-SW-339
文摘The objective of this study is to investigate pollen-vegetation relationship in the Qilian Mountains. The eastern Qilian Mountains are located in the transitional zone of the Tibetan Plateau, the Loess Plateau and the arid region of Northwest China; which is one of the key areas of global environmental change. A total of 13 surface pollen samples from main vegetation have been collected. Pollen percentages were calculated in all samples. In order to reveal the relationship between pollen composition and the vegetation types from which the soil samples have been collected, Detrended Correspondence Analysis （DCA） ordination method was employed on the pollen data. The results show that dominating vegetation types can be recognized by their pollen spectra： Picea crassifolia forest, alpine shrub and alpine meadow as well. Altitude and temperature determine the distribution of the surface pollen and the vegetation. The good agreement between modern vegetation and surface samples across this area provides a measure of the reliability of using pollen data to reconstruct paleoenvironment and paleovegetation patterns in this or other similar regions. However the loss of Betula pollen in forest needs further investigation. Pollen oxidation is the most important factor contributing to the damage of modern pollen in the study area. Pollen concentrations decrease with the increase of pH values of soils, and decrease sharply when the pH exceeds 7.6.
基金a part of research results of a state key research project(No.G1999043200)
文摘Zircons from granodiorite and biotite granite in the Yeniutan granitic intrusion in the western North Qilian Mountains yielded a weighted mean 206Pb/238U apparent age of 460±3 Ma, suggesting that the intrusion originated during the late stage of plate subduction. Its related Ta'ergou and Xiaoliugou deposits are two of the few large tungsten deposits formed in the plate subduction environment in the world. The U-Pb dating of the zircons from the biotite granite gave a discordant lower intercept age of 183±4 Ma, which implies that the Yanshanian event was probably superimposed on the North Qilian region.
