[Seasonal dynamics in photosynthetic characteristics and growth of saplings and their response to soil warming].

In order to understand the response and adaptation mechanisms of photosynthetic characteristics and growth for saplings in the subtropical region to global warming, we conducted the root-box warming experiment (ambient, ambient+4 ℃) at the Sanming Forest Ecosystem National Observation and Research Station in Fujian Province to investigate the effects of soil warming on the photosynthetic characteristics and growth of saplings in different seasons. The results showed that the net photosynthetic rate () and stomatal conductance () of significantly decreased in summer compared with in spring and autumn. Soil warming had no effect on the and of . However, the interaction between warming and season significantly impacted the leaf water use efficiency (WUE). The tree height and ground diameter growth of significantly increased in spring compared with in summer and autumn. Warming significantly reduced ground diameter growth, and it diminished the net diameter growth by 48.1% in autumn. However, warming had no impact on the tree height growth of in each season. The specific leaf area, soluble sugar, and non-structural carbohydrates contents of significantly improved in summer and autumn compared with in spring. Warming had rarely influence on leaf functional traits in each season. In conclusion, the response of photosynthesis for to soil warming was insignificant. The photosynthesis of exhibited significant seasonal dynamics, primarily controlled by . adapted to soil warming by adjusting WUE, and it adjusted to high temperatures and drought stress in summer by increasing soluble sugar content and specific leaf area. The effect of warming on ground diameter growth of was primarily driven by soil moisture. The seasonal difference in the growth of was influenced by the photosynthesis of and the trade-off between the utilization and storage of photosynthetic products.