## 3 Results
### Comparing with the Literature  
The estimated GSV and NPP values from the self-initialized model were compared with the previous literature. Many field studies, as well as modeling results for GSV and NPP, were available for some of our study sites, so we could compare our results with them directly. We obtained GSV and NPP values from previous reports if the data were available, however, we also assumed the values from diameter at breast height (DBH), gross primary productivity (GPP), and stand height in order to overcome the data limitation. For the oak forests, the forest volume of Kasuya (Japan) was estimated at around 109-516 m\({}^{3}\) ha\({}^{-1}\), when considering some old forest stands. To estimate the value, we obtained the DBH and stand density from [PERSON] and [PERSON] et al. (2008) [(35; 69)], and applied the biomass expansion equation from the National Institute of Forest Science (NIFoS), Republic of Korea [(70)]. The tree volume of oak forests in Gwangneung (South Korea) was around 550 m\({}^{3}\) ha\({}^{-1}\)[(36)], and estimated annual NPP was 4.30-6.70 Mg C ha\({}^{-1}\)[(42; 71)]. In Seolmacheon (South Korea), we could estimate the tree volume from the DBH on National Forest Inventory (NFI) data, which was around 78-159 m\({}^{3}\) ha\({}^{-1}\)[(43)]. In addition, using the hydrology model named RHESys (Regional Hydro-Ecological Simulation System), we calculated GPP as 11.93-13.96 Mg C ha\({}^{-1}\)[(72)]. Sohung (North Korea) is one of the  
Figure 4: Net primary productivity (NPP) estimation through BGC-MAN from 1960 to 2005.  
reforestation areas in North Korea, and a previous study assumed some forest characteristics, however, it estimated a forest volume of around 56-66 m\({}^{3}\) ha\({}^{-1}\) during 1989-2013 [45]. Bikinsky (Russia) is located in Far East Russia near the Chinese border. The forest volume here was estimated at around 154 m\({}^{3}\) ha\({}^{-1}\), and annual NPP at 5.05 Mg C ha\({}^{-1}\). The tree volume of the Gwangneung (South Korea) pine forest was estimated from a previous DBH survey at around 378-645 m\({}^{3}\) ha\({}^{-1}\), and a National forest inventory (NFI) plot located near the site indicated 270 m\({}^{3}\) ha\({}^{-1}\)[38]. The predicted annual NPP was 5.37-7.20 Mg C ha\({}^{-1}\)[48]. Wonsan (North Korea), which was deforested and subsequently referested, has an annual NPP range of 4.30-6.03 Mg C ha\({}^{-1}\) based on the VISIT model simulation [16]. The forest volume of Honghuaerji (China) was estimated as 117-173 m\({}^{3}\) ha\({}^{-1}\)[50]. In the case of Oblast (Russia), the forest volume was estimated at around 282 m\({}^{3}\) ha\({}^{-1}\), and annual NPP was estimated at around 3.06 Mg C ha\({}^{-1}\). The GSV of forests in Pribaykalsky (Russia) was reported to be around 102 m\({}^{3}\) ha\({}^{-1}\), and this forest's NPP was predicted to be 2.72 Mg C ha\({}^{-1}\). For the larch trees of Laoshan (China), which are part of an experimental forest, GSV was estimated at around 117.86 m\({}^{3}\) ha\({}^{-1}\) in 2001, therefore a GSV value exceeding 133.36 m\({}^{3}\) ha\({}^{-1}\) would be expected in 2005 [73]. Other model simulations estimated the 300-year cumulated NPP to be 215.4-236.6 kg m\({}^{-2}\), which can be converted to 7.18-7.89 Mg C ha\({}^{-1}\)[26], but these estimations have big variations, as these were young forest stands. The GPP of the forest in Khentei (Mongolia) was reported to be around 5.62-6.10 Mg C ha\({}^{-1}\)[24], and the GSV was estimated to be 64-146 m\({}^{3}\) ha\({}^{-1}\) via tree ring survey [52; 53]. The forest volume of Yeravninsky was reported to be 227 m\({}^{3}\) ha\({}^{-1}\), and annual GPP as 3.38 Mg C ha\({}^{-1}\). In Buryatia (Russia), the forest volume was estimated to be 117 m\({}^{3}\) ha\({}^{-1}\), and annual GPP as 2.81 Mg C ha\({}^{-1}\) (Table 3).