Three-Year Study on Diurnal and Seasonal CO2 Sequestration of a Young Fraxinus griffithii Plantation in Southern Taiwan

This study examined monthly carbon sequestration of the Himalayan ash (Fraxinus griffithii C. B. Clarke), an important plantation species in Taiwan. From January 2010 to December 2012, data were collected from an F. griffithii plantation in southern Taiwan, which experiences a typical Southeast Asia monsoon climate. To estimate CO2 sequestration rate, we conducted diurnal measurements of photosynthetic rates and seasonal measurements of photosynthetic light response curves. We also calculated leaf area index to estimate the total leaf area of individual trees. The diurnal variation in photosynthetic rate, stomatal conductance, and transpiration exhibited seasonal and annual differences. The range of net CO2 assimilation rates was 1.34-8.68 mu mol.m(-2).s(-1) in 2010, 1.02-6.60 mu mol.m(-2).s(-1) in 2011, and 1.13-4.45 mu mol.m(-2).s(-1) in 2012. A single F. griffithii tree sequestrated 12.21 kg.year(-1) CO2 on average. Annual CO2 sequestration occurred primarily during the summer for all years, averaging 14.89 Mg.ha(-1).year(-1) for three years. Correlation analyses between various environmental variables and CO2 sequestration rates indicated that air temperature and soil water content were likely the main factors influencing carbon sequestration of F. griffithii at this study site.