Abstract: The diurnal course of net photosynthesis of Korean pine and related environmental factors are measured in situ, using an improved gas exchange system. An introduction is also given for the improved measurement device and the technique of boundary-line analysis for analysing data. The diurnal course of photosynthesis is shown to be dependent largely on weather conditions, such as light, temperature and relative air humidity, Boundary-line analysis for the response of photosynthesis to light indicate that, the photosynthetic rate of Korean pine is 6.27μmol·100g^-1·s^-1: light saturation point is 800μE·m^-2·s^-1, and when effective radiation is below 800μE·m^-2·s^-1, light becomes a limiting factor for photosynthesis. The depression of photosynthesis at midday is mainly caused by high air temperature and low relative humidity.

Key words: freeze-thaw season, Betula albosinensis leaf litter, soil fauna, mass loss rate, subalpine primary forest