Abstract: Taking seven stands of Pinus sylvestris var. mongolica plantations with different stand densities (255, 372, 700, 833, 1667, 3333, and 6667 trees·hm^-2) in the Horqin Sandy Land as objects, we monitored intra-annual growth dynamics during the 2022 and 2023 growing seasons by using high-resolution radial dendrometers, and analyzed the seasonal variation and environmental drivers of radial growth. The results showed that the annual radial increment averaged 0.441±0.105 cm. The radial growth predominantly occurred from May to July, accounting for 95.8%±2.7% of total annual growth. Peak growth rates typically occurred between late May and early June. For an increase of 1000 trees·hm^-2 in stand density, annual radial growth declined by 0.043 cm, the cessation of growth occurred 3.50 days earlier, and the growing period shortened by 3.95 days on average. Linear mixed-effects modeling revealed that radial growth was influenced by stand density, the interaction between temperature and phenological stage, diameter at breast height (DBH), competition intensity, precipitation, groundwater level, and the interaction between competition and vapor pressure deficit (VPD). Notably, the interaction between temperature and phenology accounted for 56.2% of the relative contribution to radial growth. To achieve sustainable managemen, controlling stand density below 833 trees·hm^-2 would significantly enhance stand growth and carbon sequestration capacity.

Key words: Pinus sylvestris var. mongolica, plantation, radial growth, stand density, environmental factor