Growth analysis of Shorea platycarpa in response to elevated atmospheric carbon dioxide

Tropical plants responses to elevated CO2 have been poorly studied compared to temperate plants, even though they are predicted to be more perceptible in a warmer climate. This paper investigates the effect of elevated atmospheric CO2 on the growth rate of Shorea platycarpa seedlings. Shorea platycarpa seedlings of 18 months old were grown for 28 weeks in the open roof chamber supplied with elevated CO2 concentration (800 ± 50 µmol mol−1) and in the greenhouse with ambient CO2 concentration (400 ± 50 µmol mol−1). Measurements of height and stem diameter growth, absolute and relative growth rates were made at frequent intervals (once a week) throughout the 28-week treatment. Elevated CO2 significantly advanced the growth of stem diameter. The height of S. platycarpa increased by 52% and 50% in the ambient and elevated CO2, respectively, whereas stem diameter increased by 131% and 146% in the ambient and elevated CO2, respectively. Absolute growth rate (AGR) and relative growth rate (RGR) of height and stem diameter showed that both were not significantly affected by elevated CO2. The RGR and AGR for both parameters in both ambient and elevated CO2 mostly fluctuated throughout the treatment, though only one or two weeks that strikingly higher than others. This result indicates that S. platycarpa growth was mostly influenced by the variation of individual growth performance in response to the elevated CO2.