Automated foliage chamber method for long-term measurement of CO_2 flux in the uppermost canopy

摘要

Direct monitoring of CO_2 exchange in forest ecosystems is necessary for evaluation of the annual net CO_2 flux. We developed an automated foliage chamber system for long-term in situ measurement of the CO_2 flux in foliage. The chamber closes automatically for 5 min in every 30. We found a high correlation between the photosynthesis rates measured by this system and by a portable H_2O/CO_2 analyzer (LCA-3, ADC). We used the new system to continuously monitor the CO_2 flux in foliage of Quercus serrata. There was a positive correlation between CO_2 flux and short-wave radiation. The daily photosynthesis rate varied widely depending on the environmental conditions. It increased from May to July and decreased temporarily in August. The seasonal pattern of photosynthesis was almost the same as that measured by the eddy covariance method. These results suggest that the new system is effective for tracking long-term seasonal change of the CO_2 flux in foliage.