Assessing net primary productivity in tree nursery points of North Korea using biogeochemistry model

Forests of North Korea are important ecological corridors of the east side of the Mid-Latitude Ecotone (MLE) connecting to South Korea, but they have been degraded in the 1990s-2000s. Although recent increasing trends in forest areas were reported by quantitative land cover classification using remote sensing data, the quality of the forest ecosystem such as net primary productivity (NPP) was not evaluated appropriately because of limited field surveys, forest management, and reforestation activities under the complex political situation in North Korea. Therefore, process-based modeling can contribute to understanding the qualitative changes in the North Korean forest. This study selected 14 tree nursery points close to deforestation, considering land cover maps from the Korean Ministry of Environment and recent AI-based forest degradation classification. The tree species of each point were checked by the 2008 North Korean vegetation map and grouped by Maple (Acer mono), Oak (Quercus mongolica), Fir (Abies nephrolepis), and Pine (Pinus densiflora) trees. This study configured current climate data (1960-2010), RCP 4.5, and 8.5 climate scenarios (2011-2100). In addition, vegetation characteristics, soil properties, deforestation information, and reforestation assumptions were selected and fit the Biogeochemistry Management (BGC-MAN) model. In the results, the NPP values were around 3.879-7.169 Mg C ha^-1 in 2020, and they changed to 4.774-9.595 in 2100 in both RCP scenarios at each point. The annual average NPP values of 2020 were evaluated at 5.174 and 5.179 Mg C ha^-1 in RCP 4.5 and 8.5 scenarios, and the values of 2100 were evaluated at 6.135 and 6.148 in each scenario. Considering the NPP values from the satellite, the overall values were in the range of the NPP data from the satellite-based assessment. The potential net primary productivities were as good as South Korea, which had successful reforestation history. Therefore, proper ecological management planning was necessary using the process-based model, and more in-depth research would be required for North Korean forest management.