Study on the adaptation characteristics of two evergreen tree species to seasonal changes

To investigate the seasonal adaptation mechanisms of key urban landscaping species, this study focused on Euonymus japonicus and Buxus sinica, two typical evergreen species naturally growing in Beijing. We systematically measured a range of indicators related to leaf morphology, physiology, and biochemistry, and employed principal component analysis (PCA) to reveal their seasonal response strategies. The results showed that the two species have significantly different adaptation mechanisms. Euonymus japonicus adopts a "passive" tolerance strategy to cope with seasonal changes, characterized by low photosynthesis and transpiration, which is achieved by regulating six key indicators including chlorophyll (Chl) content, P/S ratio, and water use efficiency (WUE). In contrast, Buxus sinica exhibits an "active" adaptation strategy, maintaining high photosynthesis and transpiration through the dynamic regulation of fourteen indicators, such as leaf thickness (LT), net photosynthetic rate (P_n), transpiration rate (T_r), and soluble sugar (SS) content. This study confirms that despite their divergent strategies, both species maintain effective photosynthetic capacity year-round, making them excellent landscaping species suitable for cultivation in northern China.