Abstract: As an essential parameter in carbon cycle models, the photosynthetic optimal temperature plays a key role in determining the model accuracy. Thus, it is of great importance to study the response of photosynthetic optimal temperature to changes in environmental temperature. In this study, photosynthetic temperature responses in leaves of Cinnamomum camphora and Osmanthus fragrans were examined by using the Li6400XT photosynthetic analyzer (Li-Cor, Inc., Lincoln, Nebraska, USA) at 10-20 days intervals. Photosynthetic temperature response curves were fitted with an unsymmetrical parabolic curve, and the photosynthetic optimal temperature and maximum photosynthetic rate were calculated from the parameters of the fitted curves. Results showed that photosynthetic temperature response curves of both C. camphora and O. fragrans exhibited a pattern of parabolic curve, and the breadth of the curves had positive correlations with the ambient temperature. For the two species, the relationships between optimal temperature and ambient temperature showed significant linear correlations within a certain temperature range and the optimal temperature increased with the increase of ambient temperature, with C. camphora being more sensitive to changes in the ambient temperature than O. fragrans. The maximum photosynthetic rate was linearly correlated with optimal photosynthetic temperature. Similarly, the maximum photosynthesis rate of C. camphora was more sensitive to changes in the optimum photosynthetic temperature than that of O. fragrans. We concluded that C. camphora had a greater photosynthetic capacity than O. fragrans in terms of their abilities in response to change in ambient temperature.

Key words: built-up land expansion, remote sensing based ecological index (RSEI), ecology, remote sensing, Jinjiang, index-based built-up index (IBI)