Dynamic characteristics of radial growth in Abies georgei var. Smithii in cold regions based on dendrometer monitoring

Abstract

This study examined the seasonal and diurnal dynamics and the radial growth’s environmental response mechanisms of Abies georgei var. Smithii on the Sygera Mountain, southeastern Xizang. Continuous dendrometer monitoring (November 2023–November 2024) and concurrent meteorological data from automated weather stations were analyzed using the zero-growth method to quantify stem radial variation. Key findings include:(1) Diurnal radial variations during the growing season displayed a circadian rhythm characterized by daytime contraction and nocturnal expansion.(2) Seasonal growth dynamics comprised of four phases: dormant period (November–February), initiation period (March–April), rapid growth period (May–August), and decline period (September–October). Annual cumulative growth attained 8–12 mm, with peak rates (0.035 mm/d) observed in June.(3) At diurnal scales, soil temperature and moisture content showed dominant positive correlations with radial growth during the early growing season, while vapor pressure deficit (VPD) became the primary moisture stress factor during rapid growth, exhibiting significant positive correlations with radial expansion. Seasonal-scale growth exhibited greater sensitivity to temperature fluctuations than to other environmental variables. This work reveals the adaptive strategy of Abies georgei var. Smithii to alpine environments through daily-scale water regulation and seasonal-scale resource allocation, providing essential scientific evidence for refining carbon sink models and evaluating ecological barrier functions on the Qinghai-Xizang Plateau