Growth Analysis of Shorea platycarpa in Response to Elevated Atmospheric Carbon Dioxide

摘要

Tropical plants responses to elevated CO_2 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 CO_2 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 CO_2 concentration (800 ± 50 μmol mol~(-1)) and in the greenhouse with ambient CO_2 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 CO_2 significantly advanced the growth of stem diameter. The height of S. platycarpa increased by 52% and 50% in the ambient and elevated CO_2, respectively, whereas stem diameter increased by 131% and 146% in the ambient and elevated CO_2, respectively. Absolute growth rate (AGR) and relative growth rate (RGR) of height and stem diameter showed that both were not significantly affected by elevated CO_2. The RGR and AGR for both parameters in both ambient and elevated CO_2 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 perfornance in response to the elevated CO_2.