CANOPY PHOTOSYNTHETIC PRODUCTION IN A JAPANESE LARCH FOREST .2. ESTIMATION OF THE CANOPY PHOTOSYNTHETIC PRODUCTION

Seasonal changes and yearly gross canopy photosynthetic production wer e estimated for an 18 year old Japanese larch (Larix leptolepis) fores t between 1982 and 1984. A canopy photosynthesis model was applied for the estimation, which took into account the effect of light intercept ion by the non-photosynthetic organs. Seasonal changes in photosynthet ic ability, amount of canopy leaf area and light environment within th e canopy were also taken into account. Amount of leaf area was estimat ed by the leaf area growth of a single leaf. The change of light envir onment within the canopy during the growing season was estimated with a light penetration model and the leaf increment within the canopy. Ca nopy respiration and surplus production were calculated as seasonal an d yearly values for the three years studied. Mean yearly estimates of canopy photosynthesis, canopy respiration and surplus production were 37, 13 and 23 tCO(2) ha(-1) year(-1) respectively. Vertical trend, sea sonal changes and yearly values of the estimates were analyzed in rela tion to environmental and stand factors.