Abstract: The hourly reflectivity of broad-leaved Korean pine forest on Changbai Mountain from 22 May to 14 October 2001 was calculated based on total solar radiation and reflect radiation. The results showed that: the reflectivity of the forest was related to solar altitude. It was generally high just after sunrise or before sunset,but was relatively stable as solar altitude was higher than 30?. The diurnal curves of reflectivity took Ushape. The reflectivity of the forest was also related to sky conditions. In clear days,the Ushape was quite clear. In scattered days,the reflectivity just after sunrise and before sunset was not as high as in the clear days,and the Ushaped curve was shallow. In overcast days, the reflectivity fluctuated. In terms of dynamic variation in the measured period,the reflectivity was relatively high in early June,decreased a little in late June,kept stable from July to September,and dropped gradually in the first half of October. The variation was related to the phenology of the forest canopy.

Key words: Reflectivity, Broad-leaved Korean pine forest, Diurnal variation, Seasonal variation, Northwestern Yunnan Plateau, temperature, precipitation, altitude gradient, dendrochronology