Differences in leaf photoprotection strategies of tree species at different successional stages in subtropical forests under seasonal climate change and their relationship to construction cost strategies

Differences in response patterns to spatio-temporal changes in environmental stressors mediated by seasonal climatic differences reflect the underlying adaptation strategies of plants, and can provide key information how tree species respond to seasonal climatic changes at different successional stages. However, in forests dominated by subtropical broadleaf evergreen species, the relationship between leaf photoprotection strategies and their construction cost strategies in different seasons remains unclear. It limits the assessment of the impact of seasonal climate change on community growth and exploration of potential drivers of community succession. In this study, we measured photoprotective substances, chlorophyll fluorescence, photosynthetic pigments and leaf construction cost (CC) in leaves of three mid-successional and three late-successional tree species in subtropical broadleaf evergreen forest in different seasons. Our data showed that the young leaves of mid successional trees had higher photoprotection ability in summer compared to winter, and were therefore bet-ter adapted to high temperature and high light conditions in summer, but not to low temperature and high light conditions in winter. The young leaves of late-successional trees had strong and flexible photoprotection in both summer and winter, which ensured normal growth of the young leaves under high temperature and high light summer, and under low temperature and high light in winter. In addition, the photoprotection of the leaves was positively correlated with CC, suggesting that an increase in photoprotective capacity of plants was accompanied by an increase in its investment in CC. This was a response of the plants to environmental stress and the sacrifices it needed to make to maintain its survival. The differential growth patterns of late-successional species, which could grow normally in summer and winter, and mid-successional species, which were adapted to grow summer but not in winter, may be key clues to the gradual replacement of mid-successional species by late successional species.