As one of the most destructive and costly natural disasters, drought has far-reaching negative effects on agriculture, water resources, the environment, and human life. Scientific understanding of propagation from meteorological to hydrological drought is of great significance for accurate forecasting of hydrological drought and preventing and mitigating drought disasters. The objective of this study is to analyze the spatio-temporal variational characteristics of propagation from meteorological drought to hydrological drought and the associated driving mechanisms in the eastern Qilian Mountains using the standard precipitation index (SPI), standardized runoff index (SRI), and drought propagation intensity index (DPI). The results show that there has been meteorological humidification and hydrological aridification in the upper reaches of the Shiyang River Basin over the last 56 years; especially in the 2000s, the intensity of hydrological drought was the strongest and the intensity of meteorological drought was the weakest, indicating the propagation intensity of meteorological drought to hydrological drought was extremely strong during this period. The changes of meteorological and hydrological dry–wet are different, both on seasonal and monthly scales. The meteorological dry–wet is shown to have had a significant effect both on the current and month-ahead hydrological dry–wet, where the one-month lag effect was most obvious. The relationship between meteorological and hydrological droughts also vary in space: Hydrological aridification in the Huangyang River, and the rivers east of it, was greater than that in the western tributaries. The drought propagation intensities from west to east showed a decreasing trend, excluding the Huangyang River. Climate and land-use changes are the main factors affecting the propagation from meteorological drought to hydrological drought. When the natural vegetation area accounted for between 76.3–78%, the cultivated land area between 0.55–3.6% and the construction area between 0.08–0.22% were a peer-to-peer propagation process from meteorological drought to hydrological drought in the upper reaches of the Shiyang River.

Soil, as the largest organic carbon pool of terrestrial ecosystem, plays a significant role in regulating the global carbon cycle, atmospheric carbon dioxide (CO₂) levels, and global climate change. It is of great significance to scientifically understand the change rule and influence mechanism of soil organic carbon (SOC) to further understand the "source–sink" transformation of SOC and its influence on climate change. In this paper, the spatiotemporal distribution characteristics and influencing mechanism of SOC were analyzed by means of field investigation and laboratory analysis and the measured data in the Eastern Qilian Mountains. The results showed that the average SOC content of 0–50 cm was 35.74 ± 4.15 g/kg and the range of coefficients of variation (CV) between 48.84% and 75.84%, which suggested that the SOC content exhibited moderate heterogeneity at each soil layer of the Eastern Qilian Mountains. In four land cover types, the SOC content of forestland was the highest, followed by alpine meadow, grassland, and wilderness, which presented surface enrichment, and there was a decreasing trend with the soil depth. From the perspective of seasonal dynamics, there was a uniform pattern of SOC content in different land cover types, shown to be the highest in winter, followed by autumn, spring, and summer, and with the biggest difference between winter and summer appearing in the surface layer. At the same time, our study suggested that the SOC content of different land cover types was closely related to aboveground biomass and negatively related to both the mean monthly temperature and the mean monthly precipitation. Therefore, the distribution and variation of SOC was the result of a combination of climate, vegetation, and other factors.

Groundwater chemistry has an important impact on the vegetation distribution in inland areas. An in-depth understanding of the impact of groundwater chemistry on vegetation can help in developing an effective management strategy to protect the inland ecosystem. The aim of this study was to identify the influence of groundwater chemicals on species diversity and the distribution characteristics of wetland plants at multiple scales based on the groundwater chemical data from 15 sampling points and the distribution data of 13 plants in the Sugan Lake Wetland in 2016. The results show that the groundwater of the Sugan Lake Wetland is weakly alkaline, with high salinity and hardness; the water chemical type is Na-SO₄-Cl; the concentration of the major water chemical parameters is significantly different and is the highest in the northwest, followed by the southwest, and is the lowest in the east; with an increase in the groundwater depth, the concentration of major water chemical parameters first showed an increasing trend followed by a decreasing trend; Artemisia frigida Willd, Poa annua L. and Triglochin maritimum L. were adapted to the environment with a higher ion concentration of the groundwater, and their salt resistance was the strongest; Blysmus sinocompressus and Polygonum are more adapted to the environment with lower salinity and hardness of groundwater; Thermopsis lanceolata has stronger adaptability to the ion concentration, salinity, and hardness of groundwater; other plants are adapted to environments where the ion concentration, salinity, and hardness of the groundwater are moderate.

The Binggou River Basin in the eastern part of the Qilian Mountains, located at the edge of a monsoon region, is the research object of this paper. The isotope technique and HYSPLIT 4.9 model were used to study the variation characteristics of the stable isotopes of precipitation and the source of water vapor in this area. The results show that the slope and intercept of the meteoric water line in the Binggou River Basin are significantly lower than those of the global meteoric water line and slightly lower than those of the meteoric water line in northwest China, and the slope and intercept of the meteoric water line in summer and autumn are obviously smaller than they are in winter and spring. The δ¹⁸O of precipitation is enriched in the warm season, and this obvious temperature effect (greater than 0ºC) masked the embodiment of the precipitation effect to some extent. There are great differences in the circulation systems that control the water vapor sources of precipitation in different seasons, and the westerly circulation that carries the water vapor has the greatest impact on Binggou River Basin precipitation, with an average proportion of 53%. The southwestern monsoon and southeastern monsoon also influence the summer precipitation. When the water vapor from the surrounding oceans and lakes reaches the monsoon marginal area in different seasons, the properties of the air mass change significantly, showing a significant seasonal effect on the precipitation value of δ18O and the δD. The seasonal fluctuation characteristics of the stable isotopes of precipitation and their relationship with the temperature, as well as the complex water vapor recharge sources in the Binggou River Basin, show the characteristics of a transition from the eastern monsoon region to the northwestern arid region.

The headwater region of inland China is immensely important for sustaining livelihoods and maintaining ecological balance, highlighting the need to characterize and assess water quality in this region. The aim of this study is to acquire a comprehensive understanding of the spatiotemporal variation characteristics of river water chemistry and to identify the sources of major ions in the Binggou River Basin, Northwest China. The results show that the water of the Binggou River is neutral freshwater. SO₄²⁻ is the major anion, Ca²⁺ is the major cation and the river type is Ca–Na–SO₄–HCO₃. The concentrations of Na⁺, Mg²⁺, SO₄²⁻, NO₃⁻, and total dissolved solid are slightly higher than the global average. The seasonal variations of major ion concentrations in the river are highest in winter but lowest in autumn, whereas the spatial variations are greater in the east branch than in the west branch and upstream compared with downstream. Source analysis of the ions indicates that rock weathering is the main source of ions, followed by human activities such as farmland fertilization and coal burning. Water quality analysis shows that the river water is suitable for drinking and irrigation, but the water quality is relatively poor in areas with more human activity, which indicates that human activity greatly influences water quality.