Development of carbon fixation technology by afforestation of fast-growing paulownia trees: An example in Fukushima prefecture, Japan

抄録

Since the Industrial Revolution, the concentration of carbon dioxide (CO₂) in the Earth’s atmosphere has risen rapidly. CO₂ is known as a type of greenhouse gas, thus global efforts are being made to reduce CO₂ emissions. In this study, we conducted a field experiment to verify the amount of CO₂ fixed in biomass by afforestation with fast-growing paulownia. The experimental sites were located in Fukushima Prefecture, Japan. 7.5-year-old fast-growing paulownia trees were surveyed in two sites (site H, located valley and originally farmland; and site INA, located lake side and originally wasteland.). The survey included tree height, girth at breast height (GBH), and measurement of essential plant elements concentration in the soil. In addition, trees were harvested, and biomass weight was measured in the site H. The average tree height was about 16 m at site H, and only about 11.4 m at INA. The average GBH was over 70 cm at site H, and about 56 cm at INA. Among the elemental concentrations in the soil, P and N concentrations decreased significantly during the growth of Paulownia. The biomass weight of cut down trees at site H was about 560 kg on average, and the correlation between the biomass weight and tree height and GBH was examined, and it showed a strong correlation with GBH. Based on this relationship, an allometric equation was derived and CO₂ absorption by fast-growing paulownia trees was estimated to be 46.8 t-CO₂/ha/year, which is much higher than that of afforestation species such as Japanese cedar and eucalyptus.