<p>Since the Industrial Revolution, the concentration of carbon dioxide (CO₂) in the Earth’s atmosphere has risen rapidly and, has exceeded 400 ppm in recent years. CO₂ is known as a type of greenhouse gas, and because of the large amount of emissions from human industrial activities, it is considered to be a causative agent of large-scale climate change on Earth. For this reason, 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 and compared CO₂ fixation with the other tree species. The experimental sites were located in Koriyama City, Fukushima Prefecture, Japan and seven-year-old fast-growing paulownia trees were surveyed in three sites (named H, HM, and INA). The survey included tree height, girth at breast height (GBH), and measurement of essential plant elements concentration in the soil underneath the trees. In addition, trees were cut down and biomass weight was measured in the Site H. The average tree height was about 16 m at Site H, HM, and only about 11.4 m at INA. The average GBH was about 70 cm at Site H and HM, and about 56 cm at INA. A positive correlation between phosphorus concentration in soil and annual growth of tree height and GBH was also observed. The reason for the large difference in growth between Site H, HM and INA may be the effect of the location of the field as well as the concentration of elements in the soil. Site H and HM are common farmland, while INA was located on the shore of a lake and may have been affected by different factors such as groundwater levels. The biomass weight of 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 fixation 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.</p>