Abstract:Aims This study aimed at better understanding the physiological mechanisms involved in the moderately high temperature treatment, particularly those relating to partitioning of absorbed light energy in some dominant tree species of low subtropical broad-leaf forest in South China, which would affect vegetation succession. Methods Two-year old saplings of three tree species, Schima superba , Castanopsis hystrix and Cryptocarya concinna, which represent different successional stages in subtropical broad-leaf forest were treated with moderately high temperature (38 ℃ ). Their photosynthetic rate and chlorophyll fluorescence parameters were measured using a photosynthesis measurement system (Li-COR 6400 and leaf chamber fluorometer) in order to evaluate the effects of moderately high temperature on photosynthesis and partitioning of absorbed light energy under subsequent irradiance. Important findings Exposure to moderately high temperature caused decrease of photosynthetic capacity of all experimented tree species under the subsequent irradiance, and such decrease was more obvious in sun plant, S. superba and mesophytic plant, C. hystrix than in shade-adapted plant, C. concinna. The fraction of energy consumed by photochemical reaction decreased in the exposed leaves of S. superba, in comparison with those in control at 25 ℃, and a similar response was al so found in C. hystrix and C. concinna. The results showed that moderately high temperature could restrict the fraction of absorbed energy utilized in photochemical reaction in leaves treated with moderately high temperature under the subsequent irradiance. The portion of total absorbed light energy that was excessive and the fraction of energy absorbed by the inactive PSⅡ also increased in the exposed leaves at 38 ℃ irrespective of species difference, and the increments were more remarkable in C. concinna than in C. hystrix and S. superba. Different responses to moderately high temperature were dependent on tree species in subtropical broad-leaf forest. The results may mean that the increase of ambient temperature by changing climate would more severely restrict photosynthetic process in the late-successional species, C. concinnia than in the early- or mesophytic species，S. superb and C. hystrix.