Thesis (M.Sc.)--Chulalongkorn University, 2012

This paper studies how major environmental factors affect carbon dioxide absorption rates of common trees in Chulalongkorn University (Thailand). The carbon dioxide (CO2) absorption capacity among the 4 most abundant tree species -- Pterocarpus indicus, Samanea Saman, Peltophorum pterocarpum, and Terminalia Catappa were compared. Measuring CO2 absorption was done by chamber analysis approach, using Li-6400 Portable Photosynthesis System (LI-COR Inc., USA). Two kinds of measurements that are 1-leaf measurement, gauging the same leaf many times, and multiple leaf measurement, gauging many leaves many times were carried out. Multiple leaf measurement results were used to form models explaining relations between external factors and CO2 absorption. Based on all-day 1-leaf data, CO2 assimilation rates of each species were fluctuated all day in different patterns. The fluctuation was due to unstable weather. According to the models, it is obvious that light intensity (Photosynthetically Active Radiation) is the most influential factor to CO2 absorption for all studied species. P. pterocarpum and S. saman reach their maximum CO2 uptake rate of 24.5 µmol m-2s-1 and 20.5 µmol m-2s-1 when the photoactive radiation is 1100 µmol m-2s-1 and 1650 µmol m-2s-1 respectively. The others do not reach their maximum rate within model data range. On account of studied light intensity and plant species, it is concluded that P. pterocarpum gave the highest CO2 absorption in Chulalongkorn University during rainy season.