Development of an Integrated DBH Estimation Model Based on Stand and Climatic Conditions

Application of integrated Korean forest growth dynamics model to meet NDC target by considering forest management scenarios and budget

BACKGROUND

Forests are atmospheric carbon sinks, whose natural growth can contribute to climate change mitigation. However, they are also affected by climate change and various other phenomena, for example, the low growth of coniferous forests currently reported globally, including in the Republic of Korea. In response to the implementation of the Paris Agreement, the Korean government has proposed 2030 greenhouse gas roadmap to achieve a Nationally Determined Contribution (NDC), and the forest sector set a sequestration target of 26 million tons by 2030. In this study, the Korean forest growth model (KO-G-Dynamic model) was used to analyze various climate change and forest management scenarios and their capacity to address the NDC targets. A 2050 climate change adaptation strategy is suggested based on forest growth and CO₂ sequestration.

RESULTS

Forest growth was predicted to gradually decline, and CO₂ sequestration was predicted to reach 23 million tons per year in 2050 if current climate and conditions are maintained. According to the model, sequestrations of 33 million tCO₂ year^-1 in 2030 and 27 million tCO₂ year^-1 in 2050 can be achieved if ideal forest management is implemented. It was also estimated that the current forest management budget of 317 billion KRW (264 million USD) should be twice as large at 722 billion KRW (602 million USD) in the 2030s and 618 billion KRW (516 million USD) in the 2050s to achieve NDC targets.

CONCLUSIONS

The growth trend in Korea's forests transitions from young-matured stands to over-mature forests. The presented model-based forest management plans are an appropriate response and can increase the capacity of Korea to achieve its NDC targets. Such a modeling can help the forestry sector develop plans and policies for climate change adaptation.

Developing Growth Models of Stand Volume for Subtropical Forests in Karst Areas: A Case Study in the Guizhou Plateau

Forest stand volume is one of the key forest structural attributes in estimating and forecasting ecosystem productivity and carbon stock. However, studies on growth modeling and environmental influences on stand volume are still rare to date, especially in subtropical forests in karst areas, which are characterized by a complex species composition and are important in the global carbon budget. In this paper, we developed growth models of stand volume for all the dominant tree species (groups) (DTSG) in a subtropical karst area, the Guizhou Plateau based on an investigation of the effects of various environmental factors on stand volume. The Richards growth function, space-for-time substitution and zonal-hierarchical modeling method were applied in the model fitting, and multiple indices were used in the model evaluation. The results showed that the climatic factors of annual temperature and precipitation, as well as the site factors of stand origin, elevation, slope gradient, topsoil thickness, site quality degree, rocky desertification type and rocky desertification degree, have significant influences on stand volume, and the topsoil thickness and site quality degree have the strongest positive effect. A total of 959 growth equations of stand volume were fitted with a five-level stand classifier (DTSG–climatic zone–site quality degree–stand origin–rocky desertification type). All the growth equations were qualified, because all passed the TRE test (≤30%), and the majority of the R2 ≥ 0.50, above 70% of the RMSE were between 5.0 and 20.0, and above 80% of the P ≥ 75%. These findings provide updated knowledge about the environmental effect on the stand volume growth of subtropical forests in karst areas, and the developed stand volume growth models are convenient for forest management and planning, further contributing to the study of forest carbon storage assessments and global carbon cycling.

Quantifying Impacts of National-Scale Afforestation on Carbon Budgets in South Korea from 1961 to 2014

Forests play an important role in regulating the carbon (C) cycle. The main objective of this study was to quantify the effects of South Korean national reforestation programs on carbon budgets. We estimated the changes in C stocks and annual C sequestration in the years 1961–2014 using Korea-specific models, a forest cover map (FCM), national forest inventory (NFI) data, and climate data. Furthermore, we examined the differences in C budgets between Cool forests (forests at elevations above 700 m) and forests in lower-altitude areas. Simulations including the effects of climate conditions on forest dynamics showed that the C stocks of the total forest area increased from 6.65 Tg C in 1961 to 476.21 Tg C in 2014. The model developed here showed a high degree of spatiotemporal reliability. The mean C stocks of the Cool forests and other forests increased from 4.03 and 0.43 Mg C ha−1, respectively, to 102.43 and 73.76 Mg C ha−1 at a rate of 1.82 and 1.36 Mg C ha−1 yr−1 during the same period. These results imply that, although the total Cool forest area of South Korea occupied only about 12.3% (772,788 ha) of the total forest area, the Cool forests play important roles in C balances and forest ecosystems in South Korea. Annual C sequestration totals are projected to decrease at a low rate in the near future because the overall growth rate of a mature forest decreases as the stand ages. Our results quantified forest C dynamics in South Korean forests before and after national reforestation programs. Furthermore, our results can help in development of regional and national forest management strategies to allow for sustainable development of society and to cope with climate change in South Korea.

A Holistic View of Soils in Delivering Ecosystem Services in Forests: A Case Study in South Korea

In 1955, after the Korean War, only 35% of the national land area in South Korea was covered by forests. In the 1960s, the Korean Government implemented the national forestation program in order to increase the extent of the forest surface and thereby counteract the negative ecological consequences from deforestation, such as erosion and ground instability. According to previous studies, this led to an increase in carbon (C) accumulated in the forest biomass of 1.48 Gt CO2 (0.40 Gt C) in the period 1954–2012. However, these studies did not take into account the amount of soil organic carbon (SOC) that was accumulated during that period and the influence of management practices on soil ecosystem services. Currently, South Korean authorities are considering the idea of implementing some forest management practices in order to increase timber extraction (e.g., by reducing the cutting age of the trees or by applying thinning and tending measures). In this study, we assess the influence of these management regimes on SOC dynamics and propose a theoretical framework to assess the influence of forest management practices on three ecosystem services, namely, C sequestration, water supply, and biomass production, while considering soil functioning, and especially SOC, as a group of supporting services underpinning the three named ecosystem services. We find that, in terms of SOC sequestration, reducing the cutting age from 80 to 40 years would be suitable only in the case of high biomass production forests, whereas in the case of lower biomass production forests reducing the cutting age would achieve very low SOC levels. However, we propose that increasing tree species diversity, even though it would not lead to a direct increase in the SOC content, could help to lessen the negative effects of reducing the cutting age by improving other soil properties, which in turn positively affect soil functioning (e.g., soil biodiversity, nutrient availability) and the resilience of the forest ecosystem. Finally, we discuss potential policy approaches to incentivize sustainable management practices in South Korean forests from a soil protection perspective.