Abstract:

The ICT-2000TE meteorological measurement system was used to determine the transpiration rate of Cinnamomum camphora and the variation of main ecological factors around canopy layer.The results indicated that under full light condition in sunny days, a single peak curve was found in the daily variation of radiation and temperature around canopy layer. The radiation started to increase at 6:00 am and reached the peak of 150～800 μmol·m^-2 s^-1 at 12:00 , then declined to 0 at 18:00—0:00pm. The summer had the high variation and long time of radiation. Temperature reached the peak at 15:00—17:00. However, the daily change of humidity showed a reverse tendency in comparison with that of radiation and temperature. The humidity began to decrease at 6:00 and slumped to the lowest at 15:00 and then increased. The daily change of transpiration rate of C. camphora was found in the form of single peak curve and the highest value occurred at 14:00. The highest transpiration rate of 0.503 1 L·kg^-1 DW h^-1 appeared in the flourishing period of leaf, the intermediate of 0.2054L·kg^-1 DW h^-1 appeared in the senescent period, and the lowest of 0.165 1L·kg^-1 DW h^-1 appeared in the defoliating period. The rank of transpiration rate under different weather condition was in the order of sunny day > changeable day > rainy day. Annually, the lowest transpiration rate of 0.0436L·kg^-1 DW h^-1 occurred in March and the zenith of 0.1793L·kg^-1 DW h^-1 appeared in June. Radiation and temperature had great influence on the transpiration rate of C. camphora.

Key words: Cinnamomum camphora, Transpiration rate, Around canopy layer, Ecological factors