Qinghai spruce (Picea crassifolia Kom.) is an ecologically important species in the forest ecosystem of the Qilian Mountains region in China. Natural regeneration of this species is critical to maintaining forest ecosystem function. Here, we analyzed several biological indicators among naturally regenerating Qinghai spruce across several elevations in the Pailugou watershed. Specifically, seedling density, basal diameter (BD), and plant height were measured, as were soil physicochemical parameters, at 2700 m, 3000 m, and 3300 m above sea level. Differences in the regeneration indicators and correlations between the indicators and soil parameters were then assessed across elevations. The results showed that soil stoichiometry was more sensitive to changes in elevation than seedling indicators were. Furthermore, seedling density was positively correlated with soil pH, whereas BD was positively correlated with the carbon-to-nitrogen ratio (C/N), the carbon-to-phosphorus ratio (C/P), and soil organic carbon (SOC) contents. None of the analyzed soil stoichiometry parameters had a significant impact on elevation-specific differences in seedling density. However, soil pH, SOC, and C/N significantly affected variations in seedling basal diameter at different elevations. Finally, soil pH, SOC, C/N, and the carbon-to-phosphorus ratio significantly affected variations in seedlings’ heights at different elevations. This study provides a strong theoretical basis for further understanding of the mechanisms associated with Qinghai spruce regeneration, ultimately contributing to rational protection and management strategies for this important natural resource.

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.

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.