Abstract: Based on the data collected from 45 meteorological stations of Jilin Province from 1970 to 2014, the paper reviews the change trend of pan evaporation and lays emphasis on the analysis over the distribution patterns and the causes of the “evaporation paradox” in Jilin Province. The results show that in the past 45 years, the temperature in Jilin Province has increased significantly and there is a noticeable decrease trend of pan evaporation, indicating the occurrence of “evaporation paradox”. In the four seasons, the evaporation in spring decreased significantly, while the evaporation in the other three seasons increased slightly, but the difference is not obvious. Averagely the “evaporation paradox” occurred at 30 meteorological stations in total and the places of occurrence varied from west to east in an increasing manner. The “evaporation paradox” occurred more in spring than in the other seasons; in the other seasons the occurrence of “evaporation paradox” was only found at a very few stations in western and eastern regions of Jilin Province. The degree of influence of relevant meteorological factors on evaporation is: wind speed > vapor pressure difference > temperature > sunshine hours. The main factor affecting the change of evaporation in spring is wind speed, while the main factor affecting the change of evaporation in the other three seasons of summer, autumn and winter is the vapor pressure difference. The main factors affecting the annual evaporation of the western and central regions of Jilin Province are wind speed and sunshine hours, while in the south, it is the vapor pressure difference.

Key words: citrus seedling, root architecture, chlorophyll fluorescence, drought, photosynthesis