Abstract: Aims The growth of trees is highly dependent on variations in the combination of external environmental factors such as precipitation and temperature. As a dominant coniferous species in the Qilian Mountains, Juniperus przewalskii’s growth dynamics response to temperature and precipitation changes is crucial for the development of the forest ecosystem in the Qilian Mountains. Our objective is to identify the seasonal patterns of xylem formation of Juniperus przewalskii and to clarify the characteristics of its intra-annual radial growth rate in response to variations in precipitation and temperature. Methods This study selected five trees at altitude 3000 m in the Qilian Mountains, collecting microcores from each tree every five days, and employed the microcoring method to complete laboratory experiments. Important findings The results showed that: (1) The growth of Juniperus przewalskii began around May 10 (day of the year (DOY) 131 ± 3) and ended around August 10 (DOY 223 ± 3), with a total growing season of (92 ± 2) days. (2) The dynamics of xylem cell number exhibited an S-shaped intra-annual trend, while the growth rate showed a Bell-shaped intra-annual trend, with a maximum growth rate of 0.32 units·column⁻¹·day⁻¹. The maximum growth rate occurred 12 days earlier than the summer solstice. (3) Hydrothermal variations emerge as primary drivers of intra-annual radial growth, with both temperature and precipitation demonstrating significant positive effects on growth rates. Notably, precipitation shows a more pronounced lagged effect on the growth of Juniperus przewalskii. The findings of this study contribute to predicting future growth trends of Juniperus przewalskii and provide theoretical support for understanding and protecting the sustainable development of the Qilian Mountains forest ecosystem.

Key words: xylem differentiation, hydrothermal variations, microcoring, radial growth, the Qilian Mountains