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.

To examine the influence of hydrometeorological factors on forest ecosystems, this study focused on the growth response of the Qinghai spruce (Picea crassifolia Kom.) to hydrometeorological factors, such as soil moisture, relative humidity, vapor pressure deficit, temperature, precipitation and wind speed, in a mountainous watershed. The Dayekou watershed, which is situated in the Qilian Mountains, was used to study the increase in stem diameter based on the daily-monthly fluctuations, cumulative growth, and stem diameter expansion in response to hydrometeorological parameters. The stem diameters of six dominant trees (categorized in three classes) were recorded using the Dendrometer DRL26 tree stem diameter growth monitor and combined with hydrometeorological monitoring data. The influence of hydrometeorological factors on stem diameter growth was statistically analyzed. The results indicated that the daily fluctuation of stem diameter growth of Qinghai spruce exhibited a parabolic pattern, which could be divided into three stages: contraction (from 10:00 to 21:00), expanding (from 21:00 to 5:00 the following day), and growth (from 5:00 to 11:00 the following day). The monthly stem diameter growth also exhibited a trend, which could be divided into three stages: initial growth (May), rapid expansion (June-July) and slow growth (August–October). At a 40 cm depth, soil water content, air humidity, and atmospheric pressure all showed positive correlations with stem diameter growth (P < 0.01), while saturated water pressure differential, wind speed, and photosynthetically active radiation showed negative correlations (P < 0.01). Our results demonstrated that relative air humidity, soil moisture, air temperature, and atmospheric pressure at a 40 cm depth had the highest impact on the Qinghai spruce’s growth in stem diameter. Changes in these hydrometeorological factors due to potential climate change will affect forest growth in the future.

Surface runoff is a major component of the hydrological cycle, and it is essential for supporting the ecosystem services provided by grassland and forest ecosystems. It is of practical importance to understand the mechanisms and the dynamic processes of runoff in a river’s basin, and in this study, we focused on the restored montane Pailugou Basin in the Qilian Mountains, Gansu Province, China, since its water status is extremely important for the large arid area and local economies therein. Our purpose was to determine the annual variation in the surface runoff in the Pailugou Basin because it is important to understand the influence of climate fluctuations on surface water resources and the economy of the basin. In addition, little is known about the annual variations in precipitation and runoff in this region of the world. Daily atmospheric precipitation, air temperature and runoff data from 2000 to 2019 were analyzed by the calculation of the uneven annual distribution of surface runoff, the calculation of the complete adjustment coefficient, and the vector accumulation expressed by the concentration degree. We also used the cumulative anomaly approach to determine the interannual variation trend of runoff, while the change trend was quantified by the sliding average method. Finally, we used the Mann–Kendall mutation test method and regression analysis to establish the time-series trend for precipitation and runoff and to determine the period of abrupt runoff changes. The results indicated concentrated and positive distributions of surface runoff on an annual basis, with a small degree of dispersion, and an explicit concentration of extreme flows. The relative variation ranges exhibited a decreasing trend, and the distribution of the surface runoff gradually was uniform over the year. The runoff was highest from July to September (85% of the annual total). We also determined that annual surface runoff in the basin fluctuated over the 20-year period but showed an overall increasing trend, increasing by 3.94 × 10⁵ m³, with an average increase rate of 0.42 × 10⁵ m³ every ten years. From 2005 to 2014, the annual runoff and the proportion of runoff in the flood season (July to September) to the annual runoff fluctuated greatly. The correlation between the runoff and precipitation was significant (r = 0.839, p < 0.05), whereas the correlation between air temperature and surface runoff was low (r = 0.421, p < 0.05).

Qinghai spruce forests, found in the Qilian mountains, are a typical type of water conservation forest and play an important role in regulating the regional water balance and quantifying the changes and controlling factors for evapotranspiration (ET) and its components, namely, transpiration (T), evaporation (E_s) and canopy interceptions (E_i), of the Qinghai spruce, which may provide rich information for improving water resource management. In this study, we partitioned ET based on the assumption that total ET equals the sum of T, E_s and E_i, and then we analyzed the environmental controls on ET, T and E_s. The results show that, during the main growing seasons of the Qinghai spruce (from May to September) in the Qilian mountains, the total ET values were 353.7 and 325.1 mm in 2019 and 2020, respectively. The monthly dynamics in the daily variations in T/ET and E_s/ET showed that T/ET increased until July and gradually decreased afterwards, while E_s/ET showed opposite trends and was mainly controlled by the amount of precipitation. Among all the ET components, T always occupied the largest part, while the contribution of E_s to ET was minimal. Meanwhile, E_i must be considered when partitioning ET, as it accounts for a certain percentage (greater than one-third) of the total ET values. Combining Pearson’s correlation analysis and the boosted regression trees method, we concluded that net radiation (R_n), soil temperature (T_s) and soil water content (SWC) were the main controlling factors for ET. T was mainly determined by the radiation and soil hydrothermic factors (R_n, photosynthetic active radiation (PAR) and T_S30), while E_s was mostly controlled by the vapor pressure deficit (VPD), atmospheric precipitation (P_a), throughfall (P_t) and air temperature (T_a). Our study may provide further theoretical support to improve our understanding of the responses of ET and its components to surrounding environments.

The high-elevation ecosystems of the Tibetan Plateau provide crucial ecosystem services including watershed protection and water provision for downstream human and wildlife communities. Thus, understanding the relationship between soil properties and vegetation under different management regimes is important as a warming climate alters these systems. This study assessed vegetation cover, quantified the distribution of soil nutrients, and examined the relationships among soil chemical properties and plant cover in the high-elevation shrublands (3300 to 3700 m) in the Qilian Mountains on the northeastern Tibetan Plateau of China. These vegetation surveys and soil sample collections were conducted on 15 shrubland plots at different soil depths and soil chemical properties were investigated at each elevation. The content of soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), and available potassium (AK) fluctuated along the elevational gradient, while soil pH was close to neutral (pH 7.4). At our sites, SOM and TN contents generally increased with elevation, and AK was positively correlated with Salix plant cover. Using PCA, we determined that PC1 captured 43% of the total variance, and SOM and TN were the top contributing features. As climate in the region warms and precipitation becomes more variable, understanding the current soil–vegetation equilibria and how vegetation may migrate in future years is important to predicting changes in this region, especially at high elevations. From a managerial perspective, our goal was to provide additional information for restoring and managing subalpine and alpine shrubland vegetation in the Qilian Mountains to ensure the future sustainable use of these systems.

Qinghai spruce (Picea crassifolia Kom.) secondary forests in the Qilian Mountains are pivotal for water conservation and biodiversity maintenance in arid northwest China. Based on a 10.2 ha permanent monitoring plot, we employed piecewise structural equation modeling (piecewise SEM) to analyze 47 indicators covering topography, stand structure, ground cover, and soil properties. Canopy openness (CO), moss–litter thickness (MLT), and herbaceous biomass (HB) exerted significant positive effects on the regeneration density (RD) in Qinghai spruce secondary forests, while crown width (CW) exerted a negative regulatory effect on this indicator. HB, altitude (AL), and leaf area index (LAI) exerted positive promoting effects on the regeneration morphometric diversity, whereas soil organic carbon (SOC) imposed strong inhibitory effects on this diversity metric. MLT, AL, SOC, and CW were identified as four shared regulatory factors that simultaneously shape regeneration density and seedling morphometric diversity in these alpine forest ecosystems, verifying the third research hypothesis. Maintaining CO at 0.5–0.6 and retaining 5–6 cm MLT can effectively facilitate natural regeneration. This study provides quantitative threshold references for ecological restoration and refined sustainable management of alpine coniferous spruce forests in arid mountainous regions.