Tree‐Ring Latewood Mass Increment Records a Stronger Temperature Signal Than Latewood Width and Density in the Eastern Qinghai–Tibet Plateau

The Qinghai–Tibet Plateau is highly sensitive to global warming; however, the availability of instrumental climate records is limited, highlighting the urgent need for reliable, high‐resolution climate proxies. In this study, Picea purpurea trees growing near the treeline in the eastern Qinghai–Tibet Plateau were investigated and chronologies of latewood width (1927–2023), latewood density (1937–2023) and latewood mass increment (LMI) (1951–2023) were developed and compared to evaluate their responses to climatic factors. The results indicate that latewood formation in the study area is primarily controlled by temperature, whereas the influence of precipitation is relatively weak. Among the three parameters, LMI exhibits the strongest response to seasonal temperature, with a correlation coefficient of up to 0.73 ( p < 0.001) with the mean temperature from April to September of the current year, which is substantially higher than those for latewood width and latewood density. Differential analysis and spatial correlation analysis further confirm the robustness of this temperature signal. These findings demonstrate that LMI integrates the synergistic variations of latewood width and density and serves as an excellent indicator of seasonal temperature variability in high‐elevation regions, providing a promising new tree‐ring index for temperature reconstruction on the Qinghai–Tibet Plateau.