## 1 Introduction
For example, one popular product by the former method is the Moderate Resolution Imaging Spectroradiometer (MODIS) NPP [13], which can be collected globally with a fine temporal resolution. Depending on the need, such products can be unsatisfying because the spatial resolution of 1 km by 1 km is too coarse; when we want to focus more on a regional-scale analysis, a spatial resolution of 1 km cannot delineate the actual local environment accurately. The latter method is usually implemented in a regional scale analysis using fine resolution imagery, such as Landsat, to discriminate details in land cover/land use types to estimate accurate values for C/CO\({}_{2}\) content. This can also be conducted by indirectly estimating modeling parameters, but it is often performed with the associated forest inventory data collected from other ground observation sources and then integrated with the land cover information for the estimation. In comparison with MODIS, Landsat provides a much finer spatial resolution (30 m), making it possible to allocate the heterogeneity of the natural environment; however, there are again issues that must always be faced, such as the fundamental problem of utilizing optical imagery due to cloud cover. Fine resolution imagery has lower temporal resolution, and it is sometimes difficult to collect cloud free imagery through only a few observations. [PERSON] _et al._[5] has utilized synthetic aperture radar (SAR) data to extract the forest parameters related to CO\({}_{2}\) sequestration. This method has shown the usefulness of implementing SAR to observe forest extent, which could be broadly usable in conditions where there is frequent cloud cover over the area of interest. This method made it clear that not only land cover type discrimination, but also tree age, or the growth stages of the forests, plays an important role. Taking these variables into account provides more accurate estimations for the overall result, because each forest growth stage differs in its sequestration rate [5,14]. Utilizing both optical and microwave satellite imagery makes this possible. Most forest carbon sequestration capacity estimates within Japan are performed at a national scale, and detailed analyses at a regional scale are still rare; therefore, such estimates are either rough estimations on a national scale or detailed analysis on a local scale. Unfortunately, local-scale studies cannot be expanded to a national scale; they are only for smaller regions and do not apply to the country as a whole. The studies mentioned usually use a methodology involving a modeling base, site observation and statistics. However, detecting and locating forest resources does not take place. Locating precise forest resources of both forest types and their growth stages requires not only consideration of realistic estimation of sequestration [5,10,14,15,16] but also an understanding of the current status of the forest resources, which may be the most important information to gather for long-term sustainable plans to manage forests in a strategic way. Consequently, the objective of this research is to reassess the estimation of CO\({}_{2}\) sequestration (_i.e._, NPP) by forest cover in Japan based on a precise evaluation of forest extent by both forest type and age, together with the use of remote sensing data, to quantitatively estimate the CO\({}_{2}\) sequestration potential.