Abstract: Aims Abies beshanzuensis is classified as a first-class national protected plant in China, with only three remaining trees located in mixed evergreen-deciduous broad-leaved forest at approximately 1 750 m above sea level on the southwest slope of Baishanzu, Qingyuan County, Zhejiang Province. This study aims to gain a comprehensive understanding of the impact of environmental factors on the growth of A. beshanzuensis seedlings at different altitudes. Methods we established 11 experimental sites at varying altitudes (ranging from 500 to 1 500 m) in the Qingyuan mountain region to monitor the growth of transplanted A. beshanzuensis seedlings. By examining changes in environmental factors such as temperature, humidity, soil microorganisms, and physical and chemical properties of soil, we investigated how A. beshanzuensis seedlings responded to altitude change. Important findings The results showed that: (1) the seedling survival rate of A. beshanzuensis decreased by 50% due to the low altitude (500 m). The height, crown width, base diameter their corresponding growth rate of seedlings increased first and then decreased with the increase of altitude, and the seedlings grew best at 700–1 100 m altitude. (2) An increase of Simpson diversity had a significant positive effect on the base diameter growth rate of seedlings. (3) The growth of seedlings shows a significant positive correlation with air and soil temperature, and a significant negative correlation with air and soil moisture. Specifically, an increase in air and soil temperature within the range of 11–19 ℃ and a decrease of air and soil humidity within the range of 10%–25% promoted seedling growth. (4) Soil nutrient content, including ammonium nitrogen content and carbon-to-nitrogen ratio, had significant positive effects on the growth rates of seedling height, base diameter and crown width. In conclusion, altitude, fungal diversity, soil and air temperature, humidity, and soil nutrients are key environmental factors influencing the growth of A. beshanzuensis seedlings and should be considered critical factors in their ex situ conservation.

Key words: Abies beshanzuensis seedlings, altitude, soil microorganisms, physical and chemical properties of soil, temperature and humidity, seedling growth detection