Characteristics of CO2 exchange at leaf and canopy levels in tropical seasonal rain forest of Xishuangbanna

By the methods of chamber-based and eddy covariance measurements,the CO2 exchange of dominant tree species Pometia tomentosa and Gironniera subaequalis at leaf and canopy levels in the tropical seasonal rain forest of Xishuangbanna was measured in different seasons of 2004.The results showed that for the two tree species,the maximum net photosynthesis(PmaxA) of canopy based on chamber-based measurement ranked in the order of rainy season(RS) end of rainy season(ERS)foggy-cool season(FS)dry-hot season(DS),and the dark respiration rate(Rd) of leaf was RSERSDSFS.The PmaxB based on eddy covariance measurement was in the same order as that based on chamber-based measurement,while the canopy respiration rate(Re) was RSDSFSERS.The maximum net photosynthetic rate of canopy in different seasons measured by the two methods had a comparatively small difference,ranging from 0.9 to 2.0 μmol·m-2·s-1.