Abstract
In order to examine the measuring method of photosynthesis in forage plant popultions, this experiment was carried out with chamber method. Forage plants used in this experiment were tall fescue (Festuca arundinacea Schreb.) and red clover (Trifolium pratense L.) which were grown under community condition during the experimental period of 8 days (tall fescue) and of 7 days (red clover). Comparisons between the amount of dry matter calculated from C0_2 balance and one obtained by direct field measurement were made in both forage plant pupulations. The results are as follows ; 1. The results of this experiment showed that calculated values agreed approximately with observed values of dry matter in both forage plant populations. 2. As the reason why calculated and observed values of dry matter production were approximately the same, the following factors may be considered ; a) There were not great differnces in both air and soil temperature between the inside and outside of the assimilation chamber. b) In measurement of photosynthesis in both forage plant populations, the reduction of CO_2 concentration in chamber was maintained within 20% of ordinary atmospheric concentration of CO_2. c) Photosynthetic activity (20-30mg/, dm^2hr) for temperate type forage plants was maintained at higher level by the factors of a) and b) during this experimental period. 3. The results mentioned above indicate that the chamber method will be appropriate for measurement of photosynthesis of forage plant communities, if the condition of temperature and CO_2 concentration in chamber is maintained near the field condition.
