Estimation of CO₂ Sequestration by the Forests in Japan by Discriminating Precise Tree Age Category using Remote Sensing Techniques

This study estimates CO₂ sequestration by forests in Japan using Land Remote Sensing Satellite (Landsat) Operational Land Imager (OLI) and the Advanced Land Observing Satellite (ALOS) Phased Array L-band Synthetic Aperture Radar (PALSAR) remote sensing data for the in-depth retrieval of forest growth stages (tree age). Landsat imagery was used to develop a detailed forest cover map, while the PALSAR data were used to estimate the volume information. The volume was converted to tree age information for each of the three forest types in Japan. An estimation of CO₂ sequestration values for each forest type and for each tree age from the forest inventory data was made. The forest cover map results in four classes, and the overall accuracy yields approximately 74%. For the volume estimation, Root Mean Square Error (RMSE) was computed with the ground reference information resulting in 105.58 m³/ha. The final result showed that total CO₂ sequestration in Japan based on tree age forest subclasses yields 85.0 Mt∙CO₂ (coniferous), 4.76 Mt∙CO₂ (evergreen broadleaf) and 21.61 Mt∙CO₂ (deciduous broadleaf), which in total is 111.27 Mt∙CO₂. Using remote sensing techniques to quantitatively estimate CO₂ sequestration in Japanese forests has been shown both to have advantages and to offer further possibilities.