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Qilian Mountains, is an important ecological function area, an important ecological security barrier, the river runoff region in Northwest China, as well as a sensitive area to global climate change and fragile area of ecological environment. The ecological environment in this area played an important role in the economic development of Northwest China. Based on the observation data of temperature and precipitation in Qilian Mountains, MOD10A2 snow products and the flow data of Shiyang River, Heihe River and Shule River, we systematically analyzed the characteristics of climate change from 1961 to 2020, and the impacts of climate change on water resources under the scenario of climate warming. The results showed that, from 1961 to 2020, the annual average temperature increased significantly, with the rate reaching 0.39 ℃·(10 a) -1 . The warming rate was the highest in the western part of Qilian Mountains, followed by the middle and eastern regions. The warming trend was the strongest in winter and the lowest in spring. The average temperature changed abruptly in 1997. The annual average precipitation increased with flucturation, with a rate of 10 mm·(10 a) -1 , which increased most obviously in the middle of Qilian Mountains. After 2004, it entered a rainy period, with a warm and humid trend. The precipitation in the four seasons showed an increasing trend and the increase of precipitation in summer contributed the most to the annual precipitation. Annual precipitation was dominated by interannual scale change, and the contribution rate of 2.8-year was approximately 64.3%. The snow cover of Qilian Mountains was obviously affected by temperature and snowfall, which was negatively correlated with summer temperature and positively correlated with snowfall. From 2016 to 2020, the temperature increase had slowed down in Qilian Mountains, the snowfall had increased, and the snow cover tended to increase. After 2000, the temperature and precipitation increased more obviously, the meltwater from glacier and snow increased, the mountainous runoff of Shiyang River, Heihe River and Shule River had an increasing trend. Our findings are of great significance to the construction of ecological civilization and coping with climate change in Qilian Mountains.

Terrestrial evapotranspiration (ET a ) reflects the complex interactions of climate, vegetation, soil and terrain and is a critical component in water and energy cycles. However, the manner in which climate change and vegetation greening influence ET a remains poorly understood, especially in alpine regions. Drawing on the Global Land Evaporation Amsterdam Model (GLEAM) ET a data, the interannual variability of ET a and its ties to precipitation (P), potential evaporation (ET p ) and vegetation (NDVI) were analysed. The Budyko framework was implemented over the period of 1982 to 2015 to quantify the response of ET a to climate change's direct (P and ET p ) and indirect (NDVI) impacts. The ET a , P, ET p and NDVI all showed significant increasing trends from 1981 to 2015 with rates of 1.52 mm yr -1 , 3.18 mm yr -1 , 0.89 mm yr -1 and 4.0 × 10 -4  yr -1 , respectively. At the regional level, the positive contribution of increases in P and NDVI offset the negative contribution of ET p to the change in ET a (∆ET a ). The positive ∆ET a between 1982 and 2001 was strongly linked with the concomitant increase in NDVI. Increases in vegetation contributing to a positive ∆ET a differed among landscape types: for shrub, meadow and steppe they occurred during both periods, for alpine vegetation between 1982 and 2001, and for desert between 2002 and 2015. Climate change directly contributed to a rise in ET a, with P as the dominant factor affecting forested lands during both periods, and alpine vegetation between 2002 and 2015. Moreover, ET p was a dominant factor for the desert between 1982 and 2001, where the variation of P was not significant. The contributions of factors having an impact on ∆ET a are modulated by both the sensitivity of impact factors acting on ET a as well as the magnitudes of factor changes. The greening of vegetation can influence ET a by increasing vegetation transpiration and rainfall interception in forest, brush and meadow landscapes. These findings can help in developing a better understanding of the interaction of ecosystems and hydrology in alpine regions., Competing Interests: Declaration of competing interest The authors declare no competing financial interests., (Crown Copyright © 2020. Published by Elsevier B.V. All rights reserved.)

Over the past few decades, natural reserves have been affected by both climate change and human activities, and their land cover has changed dramatically, especially in mountain reserves, which are more sensitive to climate change and human activities. This paper used long-term Landsat and MODIS NDVI remote sensing data to monitor the changes of land cover and vegetation conditions in the Qilian Mountain National Nature Reserve (QMNNR) in China from 1975 to 2015, and analysed the impacts of climate change and human activities in combination with meteorological and socioeconomic data. The results show that the land cover structure of the QMNNR has remained stable over the past 40 years, but the total area of natural vegetation has decreased by 49.55 km 2 , the artificial surface and cropland has expanded by 13.68 and 32.57 km 2 in some areas, respectively, and the glacier has retreated by 33.34 km 2 as a whole. The warming and humidification trend of the climate is the leading factor for glacial retreat and the improvement of the overall vegetation condition, while population growth and economic benefits lead to the expansion of cropland and artificial surfaces in some areas, thus causing the reduction of 18.80 and 28.30 km 2 in shrubland and grassland. This study proves that the system of protected areas plays a key role in maintaining the stability of the ecosystem structure and that reducing the population density around the protected areas and changing the mode of economic development can effectively reduce the intensity of human interference. Under the background of climate warming, the change of the ecosystem function in mountain protected areas is full of uncertainty, so management and protection strategies need to be studied in depth.

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The mining of limestone mines plays a crucial role in societal and economic advancement. However, mining activities have led to destructive variations in grassland ecology and soil, causing numerous environmental problems, and effective artificial restoration measures have been used to restore grasslands in the Shimenhe mining areas to different degrees. In this study, we investigated, examined and analyzed plant community structure and its correlation with soil properties across varying degrees of alpine grassland restoration in Qilian Mountains Shimenhe restoration mines using the sample method, and studied the changes in species diversity using five diversity indexes (Simpson index, Shannon index, Margalef index, Dominance index and Evenness index). This study showed that the plant community characteristics with high recovered degree (HRD)> middle recovered degree (MRD)> low recovered degree (LRD)> very low recovered degree (VLRD), 11 plant genera comprising 11 species across 10 families were identified. Dominant families with robust ecological adaptability included Leguminosae, Rosaceae, Gramineae, Asteraceae, and Salicaceae. The highest Simpson, Shannon, Margalef and Evenness index of HRD grassland community species were 0.82, 1.96, 1.66 and 0.89, respectively. The highest Dominance index of VLRD grassland community species was 0.34, which required several restoration methods such as spraying and mulching. Soil pH and EC tended to decrease with increasing restoration, SOC, SMC, TP, AP, NH4-N, TN, AN and NO3-N tended to increase and the content of soil environmental factors contributed to vegetation growth across various restoration levels the mine grassland. In conclusion, our study indicated that the community structure gradually diversified and soil properties changed positively with the increase of restoration degrees in the Qilian Mountains Shimenhe mine, and the best results of HRD restoration were obtained. This study provides the theoretical basis for the restoration and conservation of grasslands in mining areas by demonstrating examined the correlation between plant characteristics and soil properties in restored grasslands in alpine mining areas. [ABSTRACT FROM AUTHOR]

Understanding runoff dynamics is vital for effective water management in climate-affected areas. This study focuses on the Dayekou basin in China's Qilian Mountains, known for their high climate variability. Using 25 years of data (1994–2018) on river runoff, precipitation, and temperature, statistical methods were applied to explore the annual variations and climate change impacts on these parameters. Results reveal a significant variability in the river runoff (132.27 to 225.03 mm), precipitation (340.19 to 433.29 mm), and average temperature (1.38 to 2.08 °C) over the period. Decadal rising rates average 17 mm for runoff, 17 mm for precipitation, and 0.25 °C for temperature, with the peak precipitation and runoff occurring in 1998–2000, 2008, and 2016. The annual runoff distribution also exhibited a unimodal pattern, peaking at 39.68 mm in July. The cumulative runoff during low periods constituted only 13.84% of the annual total, concentrated in the second half of the year, particularly during the June-October flood season. The correlation analysis underscored a strong relationship between river runoff and precipitation (correlation coefficient > 0.80), while the temperature correlation was weaker (correlation coefficient < 0.80). This 25-year analysis provides valuable insights into runoff variation, elucidating the interconnected effects of temperature and precipitation in the Dayekou basin, with substantial implications for sustainable development amid climate challenges. [ABSTRACT FROM AUTHOR]

Tree radial growth can have significantly different responses to climate change depending on the environment. To elucidate the effects of climate on radial growth and stable carbon isotope (δ13C) fractionation of Qinghai spruce (Picea crassifolia), a widely distributed native conifer in northwestern China in different environments, we developed chronologies for tree-ring widths and δ13C in trees on the southern and northern slopes of the Qilian Mountains, and analysed the relationship between these tree-ring variables and major climatic factors. Tree-ring widths were strongly influenced by climatic factors early in the growing season, and the radial growth in trees on the northern slopes was more sensitive to climate than in trees on the southern. Tree-ring δ13C was more sensitive to climate than radial growth. δ13C fractionation was mainly influenced by summer temperature and precipitation early in the growing season. Stomatal conductance more strongly limited stable carbon isotope fractionation in tree rings than photosynthetic rate did. The response between tree rings and climate in mountains gradually weakened as climate warmed. Changes in radial growth and stable carbon isotope fractionation of P. crassifolia in response to climate in the Qilian Mountains may be further complicated by continued climate change. [ABSTRACT FROM AUTHOR]

Understanding temperature variability especially elevation dependent warming (EDW) in high-elevation mountain regions is critical for assessing the impacts of climate change on water resources including glacier melt, degradation of soils, and active layer thickness. EDW means that temperature is warming faster with the increase of altitude. In this study, we used observed temperature data during 1979–2017 from 23 meteorological stations in the Qilian Mountains (QLM) to analyze temperature trend with Mann-Kendall (MK) test and Sen's slope approach. Results showed that the warming trends for the annual temperature followed the order of T_min > T_mean > T_max and with a shift both occurred in 1997. Spring and summer temperature have a higher increasing trend than that in autumn and winter. T_mean shifts occurred in 1996 for spring and summer, in 1997 for autumn and winter. T_max shifts occurred in 1997 for spring and 1996 for summer. T_min shifts occurred in 1997 for spring, summer and winter as well as in 1999 for autumn. Annual mean diurnal temperature range (DTR) shows a significant decreasing trend (−0.18°C/10a) from 1979 to 2017. Summer mean DTR shows a significant decreasing trend (−0.26°C/10a) from 1979 to 2017 with a shift occurred in 2010. After removing longitude and latitude factors, we can learn that the warming enhancement rate of average annual temperature is 0.0673°C/km/10a, indicating that the temperature warming trend is accelerating with the continuous increase of altitude. The increase rate of elevation temperature is 0.0371°C/km/10a in spring, 0.0457°C/km/10a in summer, 0.0707°C/km/10a in autumn, and 0.0606°C/km/10a in winter, which indicates that there is a clear EDW in the QLM. The main causes of warming in the Qilian Mountains are human activities, cloudiness, ice-snow feedback and El Nino phenomenon. [ABSTRACT FROM AUTHOR]

Study region: The Xiying River Basin is a typical inland mountainous watershed located in the Qilian Mountains. Study focus: This article reveals the change of runoff stable isotopes and their control mechanisms based on isotope data of different water bodies (precipitation, runoff, groundwater, and glacial snowmelt) in the Xiying River Basin from 2016 to 2021, combined with relevant meteorological observation data and the Normalized Vegetation Index (NDVI). New hydrological insights for the region: The results show that (1) meteorological factors control runoff isotope variations through controlling the evaporation process of runoff and the isotopic characteristics of recharge sources. (2) In areas with low vegetation cover, surface landscape features influence runoff isotopic composition by altering the isotopic characteristics of recharge sources. (3) In areas with high vegetation cover, surface vegetation cover affects runoff stable isotopes by controlling evapotranspiration processes. This study connects vegetation cover and runoff isotopes to explain the surface landscape control of runoff stable isotopes. It offers a more powerful reference for elucidating the factors influencing runoff isotopes in inland mountain watersheds.

Tibet's Qilian Mountains (QM) include critical water conservation areas and important ecological barriers, which help maintain downstream inland river oasis stability. For decades, contemporaneous climatic and cryospheric variation has severely impacted QM's hydrological processes, challenging local water resource management and sustainable development. However, due to prevalent data and methodological limitations, QM research has primarily focused on runoff change at a basin scale. Spatial distributions and temporal changes in runoff subsequently remain unclear. Based on multi‐source data and the literature, we estimated that QM's mountain outlets generate approximately 15.671 km3 in total annual runoff, exhibiting a spatially decreasing pattern from northeast to southwest. Moreover, runoff distribution and trend variation at seasonal and annual scales depend upon the river replenishment source type. Beginning in the 1950s and 1960s, eastern rain‐fed rivers experienced a downward trend while those dominated by meltwater or simultaneously fed by multiple sources in its central and western regions experienced an upward trend. As an integrated product of mixed multi‐factor effects, runoff is regulated by temperature, precipitation, and cryospheric meltwater. Moreover, the main controlling runoff factors varied seasonally under different water source concentrations. Annually, precipitation was the main driver for runoff change in the eastern region while, correspondingly, temperature was in the western region where glaciers and the snow line boundary predominant. Besides, this study highlighted that the existing literature has significant limitations in understanding interactions among different cryospheric components and hydrologic process mechanisms when exploring the reasons for runoff variations, which needs further exploration in the future. Plain Language Summary: As a critical water conservation area and ecological security barrier in western China, the Qilian Mountains (QM) is a core region within the Silk Road Economic Belt. It is regarded as the "water tower" to inland rivers in the Hexi Corridor, the eastern margin of the Qaidam Basin desert, and upstream areas of the Yellow River, nurturing more than 5 million people. However, spatiotemporal patterns and driving factors of runoff variations under climate change conditions remain unclear. Based on multi‐source data and published literature, this study estimated that 15.671 km3 of total annual runoff was generated on the QM, which generally decreased from northeast to southwest. Although seasonal distributions of runoff in major rivers were similar, their annual runoff trends showed a substantial difference between the eastern (i.e., downward trend) and western (i.e., upward trend) regions. From east to center to west, river replenishment types changed from rainfall dominant to mixed replenishment/groundwater dominant to meltwater dominant, causing different sensitivities to temperature and precipitation among rivers. Currently, the main approaches exploring physical mechanisms of QM runoff are qualitative analyses. Comprehensive quantitative research that encompasses various cryospheric components is needed to enhance scientific understanding of hydrological processes in this region. Key Points: Average annual total river runoff on the Qilian Mountains was estimated at approximately 15.671 km3, decreasing from northeast to southwestA downward trend in annual runoff was observed in the eastern region, while an upward trend was observed in its central and western regionsRiver replenishment types changed from rainfall dominant (eastern) to mixed replenishment (central) to meltwater dominant (western) [ABSTRACT FROM AUTHOR]

Quantitative assessments of the impacts of climate change and anthropogenic activities on runoff help us to better understand the mechanisms of hydrological processes. This study analyzed the dynamics of mountainous runoff in the upper reaches of the Shiyang River Basin (USRB) and its sub-catchments, and quantified the impacts of climate change and human activities on runoff using the improved double mass curve (IDMC) method, which comprehensively considers the effects of precipitation and evapotranspiration on runoff, instead of only considering precipitation as before. The results indicated that the annual runoff depth in the USRB showed a slightly increased trend from 1961 to 2018, and sub-catchments were increased in the west and decreased in the east. The seasonal distribution pattern of runoff depth in the USRB and its eight sub-catchments all showed the largest in summer, followed by autumn and spring, and the smallest in winter with an increasing trend. Quantitative assessment results using the IDMC method showed that the runoff change in the USRB is more significantly affected by climate change, however, considerable differences are evident in sub-catchments. This study further developed and improved the method of runoff attribution analysis conducted at watershed scale, and these results will contribute to the ecological protection and sustainable utilization of water resources in the USRB and similar regions. [ABSTRACT FROM AUTHOR]

Scientifically evaluating the influence of ecological restoration projects on the water conservation function (WCF) of regional ecosystems is the foundation for formulating regional ecological restoration policies and optimizing and adjusting ecological restoration projects. In this paper, we considered fully the runoff generation and confluence process in the Qilian Mountains with the actual situation of the basin and re-rated the parameter Z to improve the simulation accuracy of InVEST model. On this basis, the impact of ecological restoration project on the WCF in the upper reaches of Shiyang River Basin (SRB) in the eastern part of Qilian Mountains was quantified. The results showed that, on the whole, the water conservation depth (WCD) of forest land was the largest (138.5 mm) and that of cultivated land was the smallest (24.78 mm), while the water conservation coefficient of forest land was also the largest (93.36%) and that of unused land was the smallest (16.67%). From 1986 to 2018, the WCD showed an increasing trend in the upper reaches of SRB, among them, the WCD in the western tributaries increased faster than that in the eastern tributaries from 1986 to 2000. The significantly increased areas were mainly distributed in the middle reaches of the western tributaries and the river source areas of the eastern tributaries, while the significantly decreased areas were mainly distributed in the river source areas of the western tributaries and the cultivated land expansion area in the middle reaches of the eastern tributaries. From 2000 to 2018, the WCD of the eastern tributaries increased more than that of the western tributaries. The significantly increased areas were mainly distributed in the four eastern tributaries, and the significantly decreased areas were scattered in the middle and lower reaches of each tributary. From 1986 to 2000, the overall influence of land use change on the increase in WCD was negative, while the influence of climate and land use change on the increase in water conservation were both positive from 2000 to 2018. The influence of land use change on WCD was different in different tributaries. Among them, that of the western tributaries (except the Dongda River) was positive in two different periods, while that of the eastern tributaries (except the Xiying River) was changed from negative to positive. The implementation of ecological restoration project was one of the main reasons for the improvement of WCF in Qilian Mountains from 2000 to 2018, with a contribution of 9.04%. In the future, the protection and restoration of decreased areas of WCF should be strengthened, and the Z value determined in this paper is expected to be applied in the arid inland river basins of northwest China. [ABSTRACT FROM AUTHOR]

Accelerating glacier shrinkage is one of the most consequential of global warming. Yet, projections for the region remain ambiguous because of the tremendous spatial heterogeneity, especially in the Qilian Mountains, where glacier melt runoff is a vital water resource for the arid downstream area. To better understand glacier changes in this region, this study took regional representative Qiyi Glacier as an example and applied an enhanced distributed surface mass balance (SMB) model to glimpse the SMB variation and possible impacts on melt runoff under the RCP 4.5 and RCP 8.5 scenarios. Further, we combined a modified volume-scaling method to update the glacier geometry gradually to enhance long-term reliability. When forced with observed daily temperature and precipitation, the reconstructed glacier SMB, from 1957 through 2013, agrees well with the in situ observations. The result indicates an abrupt change for SMB from positive to negative in 1992 and subsequent mass accelerated loss after 2000. The increased summer air temperature and the pattern of large-scale atmospheric circulation shifts might both cause these changes. Using projected climate forcing from as many as 31 coupled GCMs from the CMIP 5 ensemble, the Qiyi Glacier is projected to undergo sustained SMB loss throughout the 21st century for both RCPs. By 2100, the Qiyi Glacier will lose ~25 m water equivalent (w.e.) for RCP 4.5 and ~37 m w.e. for RCP 8.5. Whereas the glacier area will shrink by 43% for RCP 4.5 and 54% for RCP 8.5 relative to 2013 glacier content, corresponding to the volume of the Qiyi Glacier will lose by 54% for RCP 4.5 and by 65% for RCP 8.5, accordingly. Simultaneously, the glacier terminus will experience extreme melts. The terminus elevation of the Qiyi Glacier will retreat from 4310 m a.s.l. in 2013 to 4810 m a.s.l. (RCP 4.5) and 4838 m a.s.l. (RCP 8.5) by the end of 2100, which will exceed the multi-year average ELA (4749 m) from 1957 to 2013. If the warming trends keep and glaciers melt like the Qiyi Glacier with this 'shocking' rate, it will raise the possibility of crippling, long-term water shortages for Hexi corridors. [ABSTRACT FROM AUTHOR]

Analyzing trends in flood magnitude changes, and their underlying causes, under climate change, is a key challenge for the effective management of water resources in arid and semi-arid regions, particularly for inland rivers originating in the Qilian Mountains (QMs). Sen's slope estimator and the Mann–Kendall test were used to investigate the spatial and temporal trends in flood magnitude, based on the annual maximum peak discharge (AMPD) and Peaks Over Threshold magnitude (POT3M) flood series, of twelve typical rivers, from 1970 to 2021. The results showed that, in the AMPD series, 42% of the rivers had significantly decreasing trends, while 8% had significantly increasing trends; in the POT3M series, 25% of the rivers had significantly decreasing trends, while 8% had significantly increasing trends. The regional differences in the QMs from east to west were that, rivers in the eastern region (e.g., Gulang, Zamu, and Xiying rivers) showed significantly decreasing trends in the AMPD and POT3M series; most rivers in the central region had non-significant trends, while the Shule river in the western region showed a significantly increasing trend. Temperatures and precipitation showed a fluctuating increasing trend after 1987, which were the main factors contributing to the change in flood magnitude trends of the AMPD and POT3M flood series in the QMs. Regional differences in precipitation, precipitation intensity, and the ratio of glacial meltwater in the eastern, central and western regions, resulted in the differences in flood magnitude trends between the east and west. [ABSTRACT FROM AUTHOR]

Qilian Mountain as an important ecological security barrier and water connotation area in China, Research on its vegetation NPP driving mechanism can provide reference for ecological security protection in northwest China. Based on Qilian Mountain MOD17A3 remote sensing data from 2000-2019, using one-dimensional linear regression, partial correlation analysis, multiple linear regression, residual analysis and land transfer matrix. The spatial and temporal dynamics of vegetation NPP in the Qilian Mountain and its correlation with precipitation, temperature and human activities were analyzed, and quantified the effects of climate change and human activities on vegetation NPP. The results show that: 1) from 2000 to 2019 vegetation NPP in Qilian Mountains had an overall fluctuating upward trend and decreased from east to west, with a multi-year average of 138.54 g C·m−2·a−1 and an average annual increase of 1.67 g C·m−2·a−1; 2) vegetation NPP was positively correlated with precipitation and temperature, with precipitation having a more significant effect on it; 3) the area of grassland in LUCC increased the most and contributed 183.12% to vegetation NPP, while the area of unused land decreased the most and its contribution to vegetation NPP was −119.6%; 4) In the vegetation recovery area, climate change and human activities explained 89% and 11% of the vegetation recovery, respectively. While in the vegetation degradation area, they explained 22% and 78% of the vegetation degradation, respectively. [ABSTRACT FROM AUTHOR]

To better understand the temporal and spatial characteristics of climate change over the past 2000 years, reliable, high-resolution paleoclimatic proxies are required. In this study, we established a 1919 year-long ring-width chronology using Juniperus przewalskii from the southern slopes of the Qilian Mountains on the Tibetan Plateau. This chronology was used to reconstruct annual minimum temperature variations from September to August. The reconstruction model explains 57.3% of the temperature variations during the calibration period (1960–2018 CE). The reconstructed temperature series reveals many clear multidecadal fluctuations, with the past 50 years being the warmest since 255 CE. Additionally, we compared our reconstruction with others from Eurasia and found that all records show greater temperature consistency during cold events on annual to multidecadal scales compared to warm events, with cold events apparently linked to volcanic activity. • We developed the longest annual minimum temperature reconstruction in China. • The last 50 years have been the warmest of the past 1764 years. • Temperature consistency among different regions is more obvious during cold epochs. [ABSTRACT FROM AUTHOR]

An increase in extreme temperature events could have a significant impact on terrestrial ecosystems. Reanalysis temperature data are an important data set for extreme temperature estimation in mountainous areas with few meteorological stations. The ability of ERA5-Land reanalysis data to capture the extreme temperature index published by the Expert Team on Climate Change Detection and Indices (ETCCDI) was evaluated by using the observational data from 17 meteorological stations in the Qilian Mountains (QLM) during 1979–2017. The results show that the ERA5-Land reanalysis temperature data can capture well for the daily maximum temperature, two warm extremes (TXx and TX90p) and one cold extreme (FD0) in the QLM. ERA5-Land’s ability to capture temperature extremes is best in summer and worst in spring and winter. In addition, ERA5-Land can capture trends in all extreme temperature indices except the daily temperature range (DTR). The main bias of ERA5-Land is due to the difference in elevation between the ground observation station and the ERA5-Land grid point. The simulation accuracy of ERA5-Land increases with the decrease of elevation difference. The results can provide a reference for the study of local extreme temperature by using reanalysis data.

In the context of continued global climate change, the intensity and frequency of droughts have increased to varying degrees in many places. Due to the complexity of drought events, the mechanisms by which trees respond to drought are not well understood. In this study, we analyzed the growth trends of Qinghai spruce (Picea crassifolia) at different elevations in the western part of Qilian Mountains and the dynamic response to climate change. We also compared the differences in radial growth of trees at different elevations in response to drought events in the growing and non-growing seasons based on resistance (Rt), recovery (Rc), and resilience (Rs). The results showed that (1) trees at all three elevations were limited by drought stress and the lower the elevation the more sensitive the trees were to drought. (2) The response of middle- and low-elevation trees to the standardized precipitation evaporation index in June of that year was stable. (3) Growing season drought limits radial growth of trees more than non-growing season drought, and Rt is smaller and Rc is larger at low elevations. With increasing drought severity, trees at all three elevations exhibited a trend of decreasing Rt and Rs and increasing Rc. (4) There were significant differences in the growth trends of trees at the three elevations. Therefore, we should continuously pay attention to the dynamics of the forest ecosystem in the western part of Qilian Mountains and take improved measures to cope with the adverse effects of drought on Qinghai spruce. [ABSTRACT FROM AUTHOR]

Understanding the spatial–temporal changes in glacier mass balance and associated drivers on the Tibetan Plateau (TP) is important for predicting future water supplies and glacier-related hazards. However, the comparative study of changes in glacier mass balance in different regions of the same glacierized massif on the TP remains scarce. Combining the reconstructed detailed mass balance time-series from 1970 to 2015 for Ningchan No.1 Glacier in the eastern Qilian Mountains and Qiyi Glacier in the western Qilian Mountains using the energy and mass balance model in this work with the published mass balance data from different glaciers, we find that interannual changes in glacier mass balance are broadly similar in different regions of the Qilian Mountains. These interannual changes are primarily driven by variations in ablation-season (June–September) air temperature (Ta), which impact albedo and melt by changing snowfall and incoming longwave radiation (Lin). We link such interannual mass balance variability to the combination of changes in atmospheric circulation over Europe and changes in sea surface temperature (SST) in the Northwest Pacific during the ablation season which can cause the changes in Ta across the Qilian Mountains. In addition, we find a trend of increasingly negative glacier mass balance across the Qilian Mountains from 1970–1994 compared to 1995–2015. This interdecadal trend is driven by higher ablation-season Ta through increasing Lin and through increasing precipitation falling as rain. Lastly, higher glacier mass loss in the east than in the west Qilian Mountains from 1970–1994 and 1995–2015 was mainly caused by lower glacier area-altitude distribution, as well as a reduction in ablation-season precipitation in the eastern Qilian Mountains. [ABSTRACT FROM AUTHOR]

Key message: Qinghai spruce at different elevations showed inconsistent growth trends and responses to climate change. Under global warming, mountains in arid and semi-arid regions have become the main ecologically vulnerable areas affected by climate change. Northwest China has experienced intermittent climate change in recent decades that can be divided into three periods: steady change (T1), a rapid temperature increase (T2) and a warming hiatus (T3). How this unsteady change in climate has affected the growth and response of trees at different elevations in the region remains unclear. Therefore, we established three standard chronologies of Qinghai spruce (Picea crassifolia) at high, middle and low elevations in the central Qilian Mountains to investigate its responses during different periods. We drew three primary conclusions. First, trees at high elevations are primarily impacted by higher temperatures, while trees at middle and low elevations are mainly impacted by water stress due to drought. Second, trees at the three elevations showed unstable responses to all temperature factors, while those at the middle and low elevations showed relatively stable responses to total precipitation in the late growing season of the previous year. Third, different interannual growth variations were observed at the three elevations, indicating a nonsignificant change at high elevations and significant declines at middle and low elevations. At the same time, growth patterns were different for the three climatic periods. Therefore, the dominant conifers at different elevations of the Qilian Mountains showed inconsistent responses during different periods. It is necessary to take effective measures to manage forest ecosystems according to spatial and temporal adaptation strategies for climate change. [ABSTRACT FROM AUTHOR]

Understanding how vegetation growth responds to climate change is a critical requirement for predicting future ecosystem dynamics. Global warming causes significant changes in the vegetation characteristics of mountain ecosystems, particularly affecting vegetation phenology and net primary productivity (NPP). The Qilian Mountains are located in an arid and semiarid region, and the mechanisms of vegetation phenology in response to climate change still need to be further explored. We used MODIS data (2001–2020) to extract vegetation phenology and NPP, quantitatively evaluated their spatial–temporal dynamics, and analyzed the response mechanism of vegetation phenology–climate and vegetation phenology–NPP combined with meteorological data. The results showed that from southeast to northwest, the vegetation phenology changes significantly with the change in vegetation type, with SOS (start of the growing season) advancing at a rate of −0.415 d/year, EOS (end of the growing season) and LOS (length of the growing season) delaying at a rate of 0.20 d/year and 0.374 d/year, respectively, and NPP continues to increase. There was also an elevation gradient effect, with SOS delayed by 15.6 d/km, EOS advanced by 12.02 d/km and LOS shortened by 19.24 d/km. We found that the preseason temperature and SPEI (standardized precipitation evapotranspiration index) have a strong influence on the SOS and EOS, with the mean minimum temperature being the most significant and requiring attention, while the influence of precipitation cannot be ignored. We also found that the vegetation phenology is closely related to NPP, and SOS has the most significant effect. This study will provide a scientific basis for the response mechanisms of vegetation phenology in arid and semiarid regions under climate change. It will provide a reference for the implementation of effective ecosystem management. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Temperature‐dependent frost cracking is a major weathering process that dominates sediment supply and hillslope erosion by reducing shear strength and conditioning slopes to be more failure‐prone in cold mountain regions. Landslides are a common erosional process in such landscapes. The linkage between these two processes has been proposed but many of the mechanisms remain to be investigated. In this study we compile a landslide inventory in the Eastern Qilian Mountains including 2482 rockfalls and 5373 elongate transport zone footprints. We use a widely accepted frost cracking model to explore this weathering process as a mechanism of paleoclimate control on the modern landslide distribution. The results show that landslides concentrate in a narrow altitudinal range and that this elevation dependence varies with slope aspect. Based on the paleoclimate record, we calculate the time‐averaged frost cracking intensity (Fci) since Last Glacial Maximum (LGM) and adopt different parameters for two slope aspects. We find that time averaged Fci is a good predictor of the landslide elevation distribution for both aspects. We then introduce two slope‐based landslide initiation and runout models (i.e., SHALRUN and FCIRUN) to examine the relative roles of slope versus temperature in determining the landslide probability in space. The FCIRUN model, which incorporates Fci as a measure of sediment supply, consistently outperforms the SHALRUN model. This result suggests that frost cracking determines the pattern of landslide initiation, although topography still controls their runout path. Our study highlights the potential of introducing Fci into slope‐based landslide prediction models to improve model skill in identifying hazardous areas (e.g., rockfall) across weathering‐limited landscapes like the Qilian Mountains. [ABSTRACT FROM AUTHOR]

Air temperature is the primary indicator of climate change. Reanalysis temperature products are important datasets for temperature estimates over high-elevation areas with few meteorological stations. However, they contain biases in observations, so a bias correction is required to enhance the accuracy of modeling predictions. In this study, we used the temperature lapse-rate method to correct ERA-Interim reanalysis-temperature data in the Qilian Mountains of China from 1979 to 2017. These temperature lapse rates were based on observations (ΓObs) and on model internal vertical lapse rates derived from different ERA-Interim pressure levels (ΓERA). The results showed that the temperature lapse rates in warm periods were larger than those in cold periods. Both the original and corrected ERA-Interim temperature can significantly capture the warming trend exhibited by observations. In general, the temperature lapse rate method was reliable for correcting ERA-interim reanalysis-temperature data. Although ΓObs performed best in bias correction, it depends heavily on the density of ground observation stations and is not appropriate for remote areas with a low data coverage. Correction methods based on ΓERA were shown to be reliable for bias correction, and will be especially applicable to mountainous areas with few observation stations. Our results contribute to the improvement of quality of data products and enhance the accuracy of modeling of climate change effects and risks to the environment and human health.

Scientifically evaluating the influence of ecological restoration projects on the water conservation function (WCF) of regional ecosystems is the foundation for formulating regional ecological restoration policies and optimizing and adjusting ecological restoration projects. In this paper, we considered fully the runoff generation and confluence process in the Qilian Mountains with the actual situation of the basin and re-rated the parameter Z to improve the simulation accuracy of InVEST model. On this basis, the impact of ecological restoration project on the WCF in the upper reaches of Shiyang River Basin (SRB) in the eastern part of Qilian Mountains was quantified. The results showed that, on the whole, the water conservation depth (WCD) of forest land was the largest (138.5 mm) and that of cultivated land was the smallest (24.78 mm), while the water conservation coefficient of forest land was also the largest (93.36%) and that of unused land was the smallest (16.67%). From 1986 to 2018, the WCD showed an increasing trend in the upper reaches of SRB, among them, the WCD in the western tributaries increased faster than that in the eastern tributaries from 1986 to 2000. The significantly increased areas were mainly distributed in the middle reaches of the western tributaries and the river source areas of the eastern tributaries, while the significantly decreased areas were mainly distributed in the river source areas of the western tributaries and the cultivated land expansion area in the middle reaches of the eastern tributaries. From 2000 to 2018, the WCD of the eastern tributaries increased more than that of the western tributaries. The significantly increased areas were mainly distributed in the four eastern tributaries, and the significantly decreased areas were scattered in the middle and lower reaches of each tributary. From 1986 to 2000, the overall influence of land use change on the increase in WCD was negative, while the influence of climate and land use change on the increase in water conservation were both positive from 2000 to 2018. The influence of land use change on WCD was different in different tributaries. Among them, that of the western tributaries (except the Dongda River) was positive in two different periods, while that of the eastern tributaries (except the Xiying River) was changed from negative to positive. The implementation of ecological restoration project was one of the main reasons for the improvement of WCF in Qilian Mountains from 2000 to 2018, with a contribution of 9.04%. In the future, the protection and restoration of decreased areas of WCF should be strengthened, and the Z value determined in this paper is expected to be applied in the arid inland river basins of northwest China.

Copyright of Plateau Meteorology is the property of Plateau Meteorology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Study region: The Qilian Mountains, Northwest China Study focus: Trends in flood frequency and their driving factors must be analyzed to enable the effective management of water resources in the inland rivers originating in the Qilian mountains (QMs). Based on hydrological station datasets from 12 typical rivers with annual maximum peak discharge and peaks-over-threshold (POT) flood series for the period 1970–2019, the spatial and temporal variations of flooding in 12 rivers were detected using a linear regression estimator and Mann–Kendall trend tests. New hydrological insights: The results indicate that the frequency of POT floods in 12 rivers during 1970–2019 showed an increasing trend at the 90% significance level, with an increasing trend for small floods and decreasing trends for medium and large floods. Flood levels varied from east to west across the region, with an overall decreasing trend in the east, an increase in small floods in the central rivers, and significant increases in both small and medium floods in the west. Both temperature and precipitation increased after 1987, and summer precipitation was a significantly increased; as a result, POT floods in most rivers increased after the 1980 s, and trends in flood frequency showed decreases in spring and autumn and an increase in summer. The main causes of the changes in flood frequency were found to be heavy rainfall, abnormal warming, and accelerated glacial melting.

Accelerating glacier shrinkage is one of the most consequential of global warming. Yet, projections for the region remain ambiguous because of the tremendous spatial heterogeneity, especially in the Qilian Mountains, where glacier melt runoff is a vital water resource for the arid downstream area. To better understand glacier changes in this region, this study took regional representative Qiyi Glacier as an example and applied an enhanced distributed surface mass balance (SMB) model to glimpse the SMB variation and possible impacts on melt runoff under the RCP 4.5 and RCP 8.5 scenarios. Further, we combined a modified volume-scaling method to update the glacier geometry gradually to enhance long-term reliability. When forced with observed daily temperature and precipitation, the reconstructed glacier SMB, from 1957 through 2013, agrees well with the in situ observations. The result indicates an abrupt change for SMB from positive to negative in 1992 and subsequent mass accelerated loss after 2000. The increased summer air temperature and the pattern of large-scale atmospheric circulation shifts might both cause these changes. Using projected climate forcing from as many as 31 coupled GCMs from the CMIP 5 ensemble, the Qiyi Glacier is projected to undergo sustained SMB loss throughout the 21st century for both RCPs. By 2100, the Qiyi Glacier will lose ~25 m water equivalent (w.e.) for RCP 4.5 and ~37 m w.e. for RCP 8.5. Whereas the glacier area will shrink by 43% for RCP 4.5 and 54% for RCP 8.5 relative to 2013 glacier content, corresponding to the volume of the Qiyi Glacier will lose by 54% for RCP 4.5 and by 65% for RCP 8.5, accordingly. Simultaneously, the glacier terminus will experience extreme melts. The terminus elevation of the Qiyi Glacier will retreat from 4310 m a.s.l. in 2013 to 4810 m a.s.l. (RCP 4.5) and 4838 m a.s.l. (RCP 8.5) by the end of 2100, which will exceed the multi-year average ELA (4749 m) from 1957 to 2013. If the warming trends keep and glaciers melt like the Qiyi Glacier with this ‘shocking’ rate, it will raise the possibility of crippling, long-term water shortages for Hexi corridors.

Land surface albedo directly determines the distribution of radiant energy between the surface and the atmosphere, and it is a key parameter affecting the energy balance on the land surface. However, the spatiotemporal dynamics of land surface albedo and associated influencing factors in the Qilian Mountains (QM) have been rarely reported. By using the long-time series data products of MODIS shortwave albedo, normalized difference vegetation index (NDVI), and snow cover with a spatial resolution of 0.05° from 2001 to 2020, this paper analyzes the temporal and spatial variations of land surface albedo in the QM over the past 20 years and its influencing factors. The analysis results show that the multi-year average surface albedo in the QM has obvious differences in spatial distribution: it increases with the altitude, and it is high in the west (at the west of 98° E) and low in the east. Meanwhile, the surface albedo has different distribution characteristics in different seasons: the spatial distribution of surface albedo is similar in spring and autumn; the areas with a high surface albedo in summer are significantly fewer than those in other seasons. Besides, in the past 20 years, the annual average surface albedo has shown a weak growth trend in the QM, with a change rate of 5 × 10−3/10a, and the minimum and maximum values were reached in 2001 and 2019, respectively. In addition, the annual variation of the surface albedo in the QM showed a "U" shape, with the largest variation in January and the smallest variation in August. The annual variation of surface albedo is significantly positively correlated with snow cover (r = 0.96) and significantly negatively correlated with NDVI (r = −0.91). Moreover, the interannual variation of the surface albedo in the QM is closely related to land surface cover and is greatly affected by snow cover. Spatially, the annual variation of surface albedo in most areas of the QM is dominated by the change of snow cover, and the increase of surface albedo in the middle area is consistent with the increase of snow cover, while the decrease of albedo in the edge area is related to the improvement of vegetation cover. The results of this study provide a scientific basis for studying the climate and environmental changes caused by changes in the surface of the QM and making ecological environment restoration strategies. [ABSTRACT FROM AUTHOR]

Analyzing trends in flood magnitude changes, and their underlying causes, under climate change, is a key challenge for the effective management of water resources in arid and semi-arid regions, particularly for inland rivers originating in the Qilian Mountains (QMs). Sen’s slope estimator and the Mann–Kendall test were used to investigate the spatial and temporal trends in flood magnitude, based on the annual maximum peak discharge (AMPD) and Peaks Over Threshold magnitude (POT3M) flood series, of twelve typical rivers, from 1970 to 2021. The results showed that, in the AMPD series, 42% of the rivers had significantly decreasing trends, while 8% had significantly increasing trends; in the POT3M series, 25% of the rivers had significantly decreasing trends, while 8% had significantly increasing trends. The regional differences in the QMs from east to west were that, rivers in the eastern region (e.g., Gulang, Zamu, and Xiying rivers) showed significantly decreasing trends in the AMPD and POT3M series; most rivers in the central region had non-significant trends, while the Shule river in the western region showed a significantly increasing trend. Temperatures and precipitation showed a fluctuating increasing trend after 1987, which were the main factors contributing to the change in flood magnitude trends of the AMPD and POT3M flood series in the QMs. Regional differences in precipitation, precipitation intensity, and the ratio of glacial meltwater in the eastern, central and western regions, resulted in the differences in flood magnitude trends between the east and west.

As an important indicator of climate change, precipitation variability is critical to the ecological environment in arid and semi-arid mountains. This study examined the variability and trends of precipitation and rain days in the Qilian Mountains based on meteorological station data during the rainy seasons of 1960–2017 using a non-parametric method. The results revealed the following. (1) Many major precipitation events occurred during the rainy season (precipitation amount and number of rain days accounted for > 80% and > 70% of the annual total, respectively) and the proportion of precipitation increased significantly with altitude. (2) The distribution of different intensity classes of precipitation was complex in different months and at different altitudes. The distribution of rain days of different intensity classes was similar to that of precipitation. Variation of precipitation and rain days was significant (not significant) in central and eastern parts (western parts and in the Hexi Corridor on the northern slopes) of the Qilian Mountains. Regions with significant (non-significant) increasing trends for both light and moderate rain were distributed above the upper portion, i.e., 2600–3200 m (in the Hexi Corridor on the northern slopes) of the Qilian Mountains. (3) Mutations of light rain and rain days occurred before the mid-1980s above the upper portion but late in the first decade of the twenty-first century in the lower portion (2000–2600 m). Mutations of moderate rain and moderate rain days occurred earlier than for light rain and light rain days; the abrupt change points occurred later with decreasing altitude. [ABSTRACT FROM AUTHOR]

The combined effects of climate change and human activities pose threat to the sustainable development of ecosystems. Human appropriation of net primary production (HANPP) has been extensively used as an important indicator for evaluating the sustainable development of the ecosystem. However, few studies quantitatively assessed the driving factors of HANPP. Based on Moderate-Resolution Imaging Spectroradiometer (MODIS) data, methods of net primary production (NPP) model and regression analysis, the spatial and temporal distribution of HANPP and its driving factors in the Qilian Mountains from 2005 to 2015 were illustrated. The results showed that the HANPP in the Qilian Mountains decreased gradually from both east to west and from south to north, showing a slight upward overall. The regions affected by human activities and climate change accounted for 26.8% and 73.2% respectively. Moreover, there was a significant negative impact between grain yield and HANPP, and a significant positive impact of either the annual sunshine duration, or livestock amount to HANPP.

The effects of climate warming are widely recognized; however, some studies have suggested that the rate of warming has slowed since the end of the twentieth century. However, the relationships between climate and the radial growth of trees during different periods of climate change have yet to be investigated fully. In the present study, tree-ring core samples were collected from Picea crassifolia and Juniperus przewalskii in the Qilian Mountains of northwest China to study the relationships between climate and radial growth. The core samples were divided into two groups: one with significant tree-growth reduction and another with insignificant reduction. Trees showing with significant growth reduction were more sensitive to climate change than trees showing insignificant growth reduction during the period of climate warming. P. crassifolia exhibited a stronger response to precipitation during May–June of the current year and from August of the previous year to June of the current year, both before and after climate warming. P. crassifolia exhibited a positive coherence with precipitation from August–September of the previous year and a negative coherence with the temperature of the current June during climate warming. After climate warming, J. przewalskii responded positively to precipitation in the current May and from the previous August to the current May. J. przewalskii also responded positively to temperature during January–February of the current year after warming. P. crassifolia responded to precipitation more strongly than J. przewalskii, whereas J. przewalskii showed a closer relationship to temperature than P. crassifolia. [ABSTRACT FROM AUTHOR]

Located at the junction between the continental climate region and marine climate region, the Qilian Mountains have experienced significant climate change. Vegetation phenology in the Qilian Mountains is sensitive to climate change. However, the response of vegetation phenology to temperature and precipitation change is still unclear, and the same is true for their interactions. First, we extracted grassland phenological parameters such as SOS (the start of the growing season), EOS (the end of the growing season), and LOS (the length of the growing season) from revised MODIS-NDVI data in the Qilian Mountains during the period from 2000 to 2019. Second, we analyzed change trends of the phenological parameters, temperature, and precipitation. Furthermore, the effects of each meteorological element changes and their interaction on multiple phenological parameters were detected using the GeoDetector method. The result implied that (1) the SOS in most areas except the northwestern mountain region showed an advanced trend (10 d/10a); the EOS showed a delayed trend in the southeast (5 d/10a), and an advanced trend (5 d/10a) in the northwest; the LOS showed an extended trend (10 d/10a) in the southeast, and a shortened trend (5 d/10a) in the northwest. (2) Compared with a single meteorological element in a single period, the interaction of temperature and precipitation in different periods had a higher impact on grassland phenology, with the maximum q-value increasing by about 0.4 for each phenological parameter. (3) The change in the grassland phenology in the Qilian Mountains was inconsistently complete with climate change in the spatial distribution. Our research reveals the response of grassland phenology to the interaction of different meteorological elements in different periods. Compared with a single element, this can reflect the response of vegetation phenology to climate change more comprehensively.

As a sensitive indicator of climate change, frozen ground (including permafrost and seasonally frozen ground (SFG)) has changed obviously due to climate warming during the past few decades. Simulated permafrost area in the Qilian Mountains has decreased about 2.63 × 104 km2 from 1960s to 2000s, with an average decreased rate of −6.1%/decade. Simulated unchanged permafrost (which did not degrade to SFG) mainly distributed in the high altitude parts of Qilian Mountains, and decreased permafrost mainly distributed at the edge of permafrost. The spatial distribution of the SFG freeze state in the Qilian Mountains can be explained primarily by altitude and longitude, not by latitude. From September 1, 1961 to August 31, 2015, the SFG freeze state has changed obviously in the Qilian Mountains, which was affected mainly by air temperature, air freezing index and air thawing index, less by precipitation. The first date of freezing was delayed by about 12 ± 2 days with a rate of 0.21 ± 0.04 days/year, whereas the last date advanced obviously by about 13 ± 3 days with a rate of 0.24 ± 0.06 days/year. Accordingly, the duration and actual number of freeze days experienced a significant decrease by 24 ± 3 and 34 ± 3 days with rates of 0.45 ± 0.06 and 0.62 ± 0.06 days/year, respectively. The maximum seasonally frozen depth decreased by 25 ± 5 cm with a rate of 0.46 ± 0.09 cm/year. [ABSTRACT FROM AUTHOR]

The permafrost in the Qilian Mountains (QLMs), the northeastern margin of the Qinghai–Tibet Plateau, changed dramatically in the context of climate warming and increasing anthropogenic activities, which poses significant influences on the stability of the ecosystem, water resources, and greenhouse gas cycles. Yet, the characteristics of the frozen ground in the QLMs are largely unclear regarding the spatial distribution of active layer thickness (ALT), the maximum frozen soil depth (MFSD), and the temperature at the top of the permafrost or the bottom of the MFSD (TTOP). In this study, we simulated the dynamics of the ALT, TTOP, and MFSD in the QLMs in 2004–2019 in the Google Earth Engine (GEE) platform. The widely-adopted Stefan Equation and TTOP model were modified to integrate with the moderate-resolution imaging spectroradiometer (MODIS) land surface temperature (LST) in GEE. The N-factors, the ratio of near-surface air to ground surface freezing and thawing indices, were assigned to the freezing and thawing indices derived with MODIS LST in considerations of the fractional vegetation cover derived from MODIS normalized difference vegetation index (NDVI). The results showed that the GEE platform and remote sensing imagery stored in Google cloud could be quickly and effectively applied to obtain the spatial and temporal variation of permafrost distribution. The area with TTOP < 0 °C is 8.4 × 104 km2 (excluding glaciers and lakes) and accounts for 46.6% of the whole QLMs, the regional mean ALT is 2.43 ± 0.44 m, while the regional mean MFSD is 2.54 ± 0.45 m. The TTOP and ALT increase with the decrease of elevation from the sources of the sub-watersheds to middle and lower reaches. There is a strong correlation between TTOP and elevation (slope = −1.76 °C km−1, p < 0.001). During 2004–2019, the area of permafrost decreased by 20% at an average rate of 0.074 × 104 km2·yr−1. The regional mean MFSD decreased by 0.1 m at a rate of 0.63 cm·yr−1, while the regional mean ALT showed an exception of a decreasing trend from 2.61 ± 0.45 m during 2004–2005 to 2.49 ± 0.4 m during 2011–2015. Permafrost loss in the QLMs in 2004–2019 was accelerated in comparison with that in the past several decades. Compared with published permafrost maps, this study shows better calculation results of frozen ground in the QLMs.

The vulnerability of vegetation ecosystems and hydrological systems in high-altitude areas makes their phenology more sensitive and their response to climate change more intense. The Qilian Mountains, an important geographic unit located in the northeastern Tibetan Plateau (TP), has experienced the more significant increases in temperature and precipitation in the past few decades than most areas of the TP. However, under such intense climate change, the temporal and spatial differences in phenology in the Qilian Mountains are not clear. This study explored the spatial and temporal heterogeneity of phenology in the Qilian Mountains from 1982 to 2014 and its response to three temperature indicators, including the mean daily temperature (Tmean), mean daily daytime temperature (Tmax), and mean daily nighttime temperature (Tmin). The results showed that (1) as the altitude rose from southeast to northwest, the multiyear mean of the start of the growing season (SOS) was gradually delayed mainly from 120 to 190 days, the multiyear mean of the end of the growing season (EOS) as a whole was advanced (from 290 to 260 days), and the multiyear mean of the length of the growing season (LGS) was gradually shortened (from 150 to 80 days). (2) In general, there was an advanced trend in the annual average SOS (0.2 days per decade), a delayed trend in the annual average EOS (0.15 days per decade), and an extended trend in the annual average LGS (0.36 days per decade) over the study period. However, there has been no significant phenological trend in recent years, especially for the SOS after 2000 and the EOS and LGS after 2003. (3) Higher preseason temperatures led to an advanced SOS and a delayed EOS at the regional scale. Moreover, the SOS and EOS were more triggered by Tmax than Tmin and Tmean. The LGS was significantly positively correlated with annual mean temperature (r = −0.82, p < 0.01).

• The distinct patterns of grassland NDVI changes in different sub-basins within the Qilian Mountains were identified. • The key factors affecting grassland NDVI varied among basins. • In the western Qilian Mountains, sunshine duration and relative humidity emerged as the predominant driving factors, whereas altitude and temperature played a more significant role in the eastern Qilian Mountains. • Grassland NDVI exhibited a response that depended on specific threshold levels when multiple factors interacted. The Qilian Mountains (QLMs) encompass a diverse alpine grassland ecosystem undergoing notable changes due to global climate change. Understanding the driving forces behind these changes is crucial for effective regional vegetation restoration and management, particularly given the contrasting climatic conditions between the eastern and western regions of the QLMs. This study investigated the spatiotemporal evolution of grassland NDVI and the influence of 13 variables on NDVI changes in six distinct QLM sub-basins from 1990 to 2019 using Landsat data and the Geodetector model, respectively. Results revealed a consistent greening trend in all sub-basins, albeit with varying slopes. Notably, the Qinghai Lake basin exhibited a recent slowdown in NDVI, highlighting the need for enhanced vegetation restoration efforts, especially in permafrost-covered areas. Environmental factors affecting NDVI differed among basins. In the western QLMs, sunshine duration and relative humidity emerged as key factors influencing NDVI distribution, while in the eastern basins, altitude and air temperature played significant roles. This study underscored the importance of hydrothermal conditions, both horizontally and vertically, in shaping grassland NDVI. Other factors, such as vegetation types, soil characteristics, and permafrost degradation, also influenced NDVI, while slope and slope aspects had a limited impact. Furthermore, the research identified threshold-dependent responses of NDVI to the interaction of these factors. These findings emphasized the need to customize vegetation restoration strategies based on the specific environmental conditions of each basin within the QLMs. This nuanced understanding of the distinct driving characteristics between the eastern and western QLMs enables more effective and targeted approaches to restoring and managing grassland ecosystems in this region. [ABSTRACT FROM AUTHOR]

Based on MODIS data, we analyzed the spatial distribution and the intra- and inter-annual variations of the snow cover in the Qilian Mountains. In addition to discussing regional climate, we discussed the reasons for the snow cover pattern variations. The spatial distribution of the snow cover in the Qilian Mountains is uneven, and the snow cover in the west is significantly greater than that in the east. The difference in the intra-annual variations of the snow cover at different altitudes is large, and the general seasonal cycle exhibits two maxima and one minimum. The snow cover and precipitation in the Qilian Mountains were consistently increasing from 2000 to 2005, but they generally decreased from 2008 to 2013. The influences of temperature, wind speeds and precipitations on snow cover variation at different altitudes vary greatly, with the snow cover being more sensitive to precipitation in the winter, while temperature and precipitation are the major factors that affect the snow cover in the spring.

Precipitation plays an essential role in hydrological cycle, water resource availability, and ecological economics sustainable development both within the Qilian Mountains (QM) and its surrounding. On the basis of meteorological station records and reanalysis data sets, we investigate the variations of precipitation in the QM during 1960–2014 and their connection to the shifts of regional atmospheric water vapour. Results show that precipitation in the QM as a whole has experienced pronounced wetting at an annual rate of 6.95 mm/decade. Significant (at 95% confidence level) precipitation increase mainly occurs in JJA (June–August) and slightly in DJF (December–February). The evident increase of precipitation appears in the mid‐east of the QM. Furthermore, the increasing rates of annual, JJA, and SON (September–November) precipitation increase with elevation, indicating obvious elevation‐dependent precipitation increase in the QM. The atmospheric precipitable water (PW) for annual, JJA, and SON time series over the targeted region generally shows significant increasing trends, especially during 1979–2014. The meridional and zonal water vapour budgets positively and negatively contribute to the regional net water vapour budget, respectively. Moreover, we demonstrate that the zonal water vapour budgets are strongly intensified and meanwhile the meridional ones except in transitional seasons are weakened. Thus, regional net water vapour budgets for annual and seasonal time series are increased. All in all, the shifts of the regional atmospheric water vapour, such as the increases of PW and water vapour budget (referring to the zonal and regional net water vapour budgets), agree with the result that the QM precipitation increases from 1960 to 2014, which suggests the QM wetting trend is in connection with the changes of the atmospheric water vapour. [ABSTRACT FROM AUTHOR]

The sparsity of long-term reliable climatic records hampers our understanding of human-environment interactions in the semi-arid Hexi Corridor, NW China. Here, we present a late-Holocene pollen record from a small alpine lake, Tian'E, in the western Qilian Mountains. The chronology is provided by nine accelerator mass spectrometry (AMS) 14C dates from terrestrial plant remains. The ratios of Artemisia and Amaranthaceae (A/C) are used to reconstruct the history of regional humidity: An unstable climate occurred during 1530-1270 BC; there were three relatively wet periods, at 1270 BC-AD 400, AD 1200-1350, and AD 1600-present; and there were two dry periods, from AD 400 to 1200 and from AD 1350 to 1600. Comparison with tree-ring data indicates that continuous droughts were responsible for the abandonment of several archaeological sites and ancient cities in the region, including the major city of Dunhuang, which was abandoned in AD 1372 and AD 1524 for nearly 200 years. [ABSTRACT FROM AUTHOR]

Elevation is one of key factors to affect changes in the environment, particularly changes in conditions of light, water and heat. Studying the soil physicochemical properties and vegetation structure along an elevation gradient is important for understanding the responses of alpine plants and their growing environment to climate change. In this study, we studied plant coverage, plant height, species richness, soil water-holding capacity, soil organic carbon (SOC) and total nitrogen (N) on the northern slopes of the Qilian Mountains at elevations from 2124 to 3665 m. The following conclusions were drawn: (1) With the increase of elevation, plant coverage and species richness first increased and then decreased, with the maximum values being at 3177 m. Plant height was significantly and negatively correlated with elevation (r=-0.97, P<0.01), and the ratio of decrease with elevation was 0.82 cm·100 m-1. (2) Both soil water-holding capacity and soil porosity increased on the northern slopes of the Qilian Mountains with the increase of elevation. The soil saturated water content at the 0-40 cm depth first increased and then stabilized with a further increase of elevation, and the average ratio of increase was 2.44 mm·100 m-1. With the increase of elevation, the average bulk density at the 0-40 cm depth first decreased and then stabilized at 0.89 g/cm3. (3) With the increase of elevation, the average SOC content at the 0-40 cm depths first increased and then decreased, and the average total N content at the 0-40 cm depth first increased and then stabilized. The correlation between average SOC content and average total N content reached significant level. According to the results of this study, the distribution of plants showed a mono-peak curve with increasing elevation on the northern slopes of the Qilian Mountains. The limiting factor for plant growth at the high elevation areas was not soil physicochemical properties, and therefore, global warming will likely facilitate the development of plant at high elevation areas in the Qilian Mountains. [ABSTRACT FROM AUTHOR]

Glaciers are the most important fresh-water resources in arid and semi-arid regions of western China. According to the Second Chinese Glacier Inventory (SCGI), primarily compiled from Landsat TM/ETM+ images, the Qilian Mountains had 2684 glaciers covering an area of 1597.81±70.30 km² and an ice volume of ~84.48 km³ from 2005 to 2010. While most glaciers are small (85.66% are <1.0 km2), some larger ones (12.74% in the range 1.0-5.0 km²) cover 42.44% of the total glacier area. The Laohugou Glacier No.12 (20.42 km2) located on the north slope of the Daxue Range is the only glacier >20 km² in the Qilian Mountains. Median glacier elevation was 4972.7 m and gradually increased from east to west. Glaciers in the Qilian Mountains are distributed in Gansu and Qinghai provinces, which have 1492 glaciers (760.96 km²) and 1192 glaciers (836.85 km²), respectively. The Shule River basin contains the most glaciers in both area and volume. However, the Heihe River, the second largest inland river in China, has the minimum average glacier area. A comparison of glaciers from the SCGI and revised glacier inventory based on topographic maps and aerial photos taken from 1956 to 1983 indicate that all glaciers have receded, which is consistent with other mountain and plateau areas in western China. In the past half-century, the area and volume of glaciers decreased by 420.81 km² (-20.88%) and 21.63 km³ (-20.26%), respectively. Glaciers with areas <1.0 km² decreased the most in number and area recession. Due to glacier shrinkage, glaciers below 4000 m completely disappeared. Glacier changes in the Qilian Mountains presented a clear longitudinal zonality, i.e., the glaciers rapidly shrank in the east but slowly in the central-west. The primary cause of glacier recession was warming temperatures, which was slightly mitigated with increased precipitation. [ABSTRACT FROM AUTHOR]

Based on daily maximum and minimum temperatures at 18 meteorological stations in the Qilian Mountains and Hexi Corridor between 1960 and 2013, temporal and spatial variations in extreme temperatures were analysed using linear trends, ten-point moving averages and the Mann-Kendall test. The results are as follows: The trends in the majority of the extreme temperature indices were statistically significant, and the changes in the extreme temperatures were more obvious than the changes in the extreme values. The trends were different for each season, and the changes in rates and intensities in summer and autumn were larger than those in spring and winter. Unlike the cold indices, the magnitudes and trends of the changes in the warm indices were larger and more significant in the Hexi Corridor than in the Qilian Mountains. Abrupt changes were detected in the majority of the extreme temperature indices, and the extreme cold indices usually occurred earlier than the changes in the extreme warm indices. The abrupt changes in the extreme temperatures in winter were the earliest among the four seasons, indicating that these temperature changes were the most sensitive to global climate change. The timing of the abrupt changes in certain indices was consistent throughout the study area, but the changes in the cold indices in the Hexi Corridor occurred approximately four years before those in the Qilian Mountains. Similarly, the changes in the warm indices in the western Hexi Corridor preceded those of the other regions. [ABSTRACT FROM AUTHOR]

Based on MODIS data, we analyzed the spatial distribution and the intra- and inter-annual variations of the snow cover in the Qilian Mountains. In addition to discussing regional climate, we discussed the reasons for the snow cover pattern variations. The spatial distribution of the snow cover in the Qilian Mountains is uneven, and the snow cover in the west is significantly greater than that in the east. The difference in the intra-annual variations of the snow cover at different altitudes is large, and the general seasonal cycle exhibits two maxima and one minimum. The snow cover and precipitation in the Qilian Mountains were consistently increasing from 2000 to 2005, but they generally decreased from 2008 to 2013. The influences of temperature, wind speeds and precipitations on snow cover variation at different altitudes vary greatly, with the snow cover being more sensitive to precipitation in the winter, while temperature and precipitation are the major factors that affect the snow cover in the spring. [ABSTRACT FROM AUTHOR]