A Study On The Characteristics Of Leaves And Canopies Carbon Dioxide Exchange And Their Relationship In A Tropical Seasonal Rainforest Of Xishuangbanna, SW China

The tropical forests are among the important and least monitored of terrestrial ecosystems. For discussing the characteristics of dominant uppermost canopy trees photosynthesis and its effects on diurnal change of canopy carbon flux in tropical seasonal rain forest, we measured canopy tree photosynthesis in the three seasons from 2003 to 2004 in Xishuangbanna tropical rain forest. The results indicated that:1. The wind speed above crown canopy was stronger than that under canopy, and the diurnal and vertical change under the canopy was not obvious. The wind speed at daytime was stronger than that at nighttime. Wind direction had obvious diurnal characteristics, i.e., leaning southeast wind at daytime and leaning west wind at nighttime. At daytime, the change trend of zero-plane displacement (d) was in the order of morning>noon> afternoon, and the annual change range in the afternoon was wider and lower than that in the morning and at noon.2. In daytime, the diurnal patterns of Pometia Tomentosa photosynthesis were almost: morning>noon>afternoon. PAR was the main factor of the diurnal changes of net photosynthesis. The short-term response of Pometia tomentosa to enriched CO2 concentration could evidently increased the photosynthesis.3. The net photosynthesis of five plant species increased by 25~118% with the...