Objective This study aimed to explore the differences in the response of the radial growth of Pinus tabulaeformis in Beijing's Miyun and Mentougou regions to climate change, and to reveal the climate regulation mechanisms of their growth process and phenological period, i providing scientific basis for the sustainable management of coniferous artificial forests in North China under the background of climate warming.

Methods The Vaganov-Shashkin model was calibrated and verified using observed data, and the optimized parameters were applied to simulate the daily radial growth of P. tabulaeformis in Miyun and Mentougou. Growth rate dynamics were analyzed, and long-term variations in the start of the growth season (SOS), end of the growth season (EOS), and length of the growth season (LOS) were quantified.

Results The correlation coefficients between simulated and observed tree-ring widths exceeded 0.44 (p<0.05), confirming the reliability of the model. In Miyun, the growth rate (Gr) and growth rate dependent on soil moisture W (GrW) of P. tabulaeformis exhibited a unimodal curve, whereas the growth rate dependent on temperature T (GrT) in Miyun, as well as Gr, GrW, and GrT in Mentougou, displayed a bimodal pattern. Correlation analysis revealed that the radial growth of P. tabulaeformis at both sites was mainly influenced by temperature at the beginning and end of the growing season, and by soil moisture during the mid- growing season. The average GrW in extremely wide-ring years was 17.20% higher in Miyun and 122.20% higher in Mentougou compared with extremely narrow-ring years, with highly significant differences. Over the past 30 years, SOS advanced by 10.73 days in Miyun and 8.12 days in Mentougou. Meanwhile, EOS advanced by 0.58 days in Miyun and was delayed by 5.22 days in Mentougou, resulting in an increase in LOS by 10.44 days and 13.63 days, respectively. An earlier SOS significantly promoted radial growth in Mentougou, but had no significant effect on growth in Miyun.

Conclusions The radial growth of P. tabulaeformis in Beijing is alternately regulated by temperature and water stress, with clear regional differences. During the early stage of the growing season and under the background of warming and drying, the growth of P. tabulaeformis in Mentougou is more susceptible to heat inhibition; while in the middle stage of the growing season, the growth of P. tabulaeformis in both areas is primarily constrained by soil moisture. These findings provide a scientific reference for precise forest management and drought-resistant strategy formulation at the regional scale.