Hyun-Jun Kim

Inland wetlands store disproportionate soil organic carbon (SOC), yet spatially explicit information is scarce for temperate monsoon riverine wetlands, where recurrent erosive flooding shapes carbon accumulation. To map depth-resolved SOC stocks (kg C m⁻²) and evaluate satellite covariates, we combined stocks measured at 494 sites in the Han, Geum, and Yeongsan–Seomjin river basins, South Korea, with multi-temporal Sentinel-2 and terrain covariates in random forest models at 20 m for the organic layer, 0–30 cm, and 0–100 cm. Cross-validated R² (squared correlation) was low (0.21, 0.18, and 0.15, respectively) but within the range reported for wetland SOC mapping. Satellite covariates raised R² by 0.02–0.07 and reduced the root mean square error (RMSE) relative to a non-satellite baseline; dormant-season reflectance added no information. The April normalized difference vegetation index (NDVI) ranked highest for both mineral-soil layers, while hydrology and parent material gained importance at 0–100 cm. NDVI showed a threshold-type partial-dependence response despite weak rank correlations; one plausible interpretation is that vegetation cover indicates the geomorphic stability of the ground surface. The model-based regional stocks are 3.11 and 6.08 Mt C at 0–30 and 0–100 cm (27.7 and 54.1 t C ha⁻¹), at the low end of published values for Asian monsoon riverine wetlands. The maps provide a baseline for carbon assessment.

This study was conducted to develop nectar yield models and quantify potential honey production in Robinia pseudoacacia (black locust) stands, a major melliferous tree species in temperate regions. Growth, flowering, and nectar characteristics were measured for 21 R. pseudoacacia trees in Hwasun and Gwangju, Republic of Korea. Nectar yield models were constructed using diameter at breast height (DBH), root collar diameter (RCD), tree height (H), and tree age as predictors. Mean nectar volume per flower was 1.57 µL in Gwangju and 1.09 µL in Hwasun, whereas nectar sugar content per flower was 0.65 mg and 0.71 mg in Gwangju and Hwasun, respectively. Nectar yield per tree was significantly and positively correlated with all growth variables, with DBH showing the strongest correlation. The DBH-based model was developed as Y = 137.914(e^{−0.202(DBH)})^6.808, and the height-, RCD-, and age-based models followed logistic functions with coefficients of determination (R²) ranging from 0.77 to 0.90. By integrating the DBH-based model with an existing stand yield table, honey production was predicted ranging from 13.4 to 74.8 g per tree and 23.6 to 57.8 kg per hectare across stand ages of 10–60 years. These models provide a quantitative framework for assessing honey production potential of R. pseudoacacia stands and support decision-making in apiculture and melliferous resource management under changing climatic conditions.

Climate change drives shifts in forest vegetation zones, and the major tree species of warm–temperate evergreen broad-leaved forests in South Korea are also expected to undergo changes in their potential distributions under future climate conditions. This study applied a Committee Averaging (CA) ensemble species distribution model to Quercus acuta, Machilus thunbergii, Quercus glauca, and Castanopsis sieboldii to project changes in their potential distributions under four Shared Socioeconomic Pathway (SSP) scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) across two future periods (2050s and 2090s). To compare interspecific differences in response more clearly, we applied a two-tier threshold scheme that distinguished potential habitat (agreement ≥0.6) from highly suitable habitat (>0.8), and we concurrently conducted a Multivariate Environmental Similarity Surface (MESS) analysis to assess predictive uncertainty arising from extrapolation into future climates. The CA ensemble models showed excellent predictive performance (AUC 0.947–0.989; TSS 0.837–0.943). For Q. acuta, M. thunbergii, and Q. glauca, potential habitat expanded consistently across all SSP scenarios, and highly suitable habitat shifted northward into parts of the central and Gangwon regions. In contrast, both the potential habitat and the highly suitable habitat of C. sieboldii contracted under most future scenarios. These results demonstrate that even species belonging to the same warm–temperate evergreen broad-leaved forest community can respond differently to future climate. The two-tier threshold scheme applied in this study was effective not only for assessing whether distributions expand but also for delineating and evaluating climatically stable core habitats. Although our findings need to be interpreted in light of the uncertainty associated with extrapolation into future climates, they can serve as useful baseline data for establishing climate-change-adaptive forest conservation and species-specific management strategies.

This study aimed to develop a stand yield table for Acacia mangium plantations in Vietnam and to analyze their economic feasibility. Field measurements were conducted across 12 temporary sample plots established in A. mangium plantations aged 1–7 years in northeastern Vietnam, using a chronosequence sampling design. Based on this, regression analyses were performed to develop stand growth models for DBH, H, SD, BA, and V. NPV measures the absolute value of the investment at a specified discount rate (4.0%, 5.5%, and 7.0%), while IRR identifies the break-even discount rate. At rotation ages of 5–7 years, IRR values are negative—a mathematically valid result arising from non-conventional cash flow structures in which Norstrom’s sign-change criterion is not satisfied; positive IRR values (~4%) are obtained from rotation age 8 onward. A sensitivity analysis confirmed that increasing yields is the most effective strategy for increasing plantation viability. This study serves as a fundamental resource for plantation projects in Vietnam and emphasizes the necessity of management improvements to create sustainable plantation operations.

Climate change has been transforming forest ecosystems globally, affecting the sustainability of conventional forest management practices. This study investigates the suitable forestation area (SFA) for Larix kaempferi and Chamaecyparis obtusa and their growth potential in South Korea under various climate change scenarios. Using species distribution models (SDMs) based on machine learning ensembles, we analyzed potential spatial shifts in the climatic suitability for these species. Growth models based on field data were also developed to evaluate growth variation between Köppen–Geiger climatic zones. The results indicate a substantial reduction in the SFA for L. kaempferi, with its habitat range confined to high-altitude regions due to rising temperatures. In contrast, the forestation potential for C. obtusa is predicted to expand nationwide, particularly in inland areas, under climate change scenarios. However, extreme increases in temperature and atmospheric CO₂ concentrations exceeding 600 ppm may inhibit growth, highlighting the need for the development of adaptive management strategies. This study provides useful information for climate-resilient forestation planning by combining growth-weighted suitability indices with projected habitat shifts. These findings emphasize the importance of prioritizing high-altitude conservation zones for L. kaempferi and employing C. obtusa for inland afforestation as a means to ensure sustainable forest management and carbon neutrality objectives.

The concurrent environmental challenges of invasive species and soil microplastic contamination increasingly affect agricultural ecosystems, yet their combined effects remain underexplored. This study investigates the interactive impact of the legacy effects of Canada goldenrod (Solidago canadensis L.) invasion and soil microplastic contamination on wheat (Triticum aestivum L.) seed germination and root development. We measured wheat seed germination and root growth parameters by utilizing a controlled potted experiment with four treatments (control, S. canadensis legacy, microplastics, and combined treatment). The results revealed that the legacy effects of S. canadensis and microplastic contamination affected wheat seed germination. The effects of different treatments on wheat seedling properties generally followed an “individual treatment enhances, and combined treatment suppresses” pattern, except for root biomass. Specifically, the individual treatment promoted wheat seedling development. However, combined treatment significantly suppressed root development, decreasing total root length and surface area by 23.85% and 31.86%, respectively. These findings demonstrate that while individual treatments may promote root development, their combined effects are detrimental, indicating a complex interaction between these two environmental stressors. The study highlights the need for integrated soil management strategies to mitigate the combined impacts of invasive species and microplastic contamination on crop productivity and ecosystem health.

In 2021, a seedling rot disease was observed on Hinoki cypress (Chamaecyparis obtusa) seedlings in a bareroot forest nursery in Naju‐si, Jeollanam‐do Province, South Korea. Infected seedlings were yellowing at the disease outset but became black after severe infection. At onset of disease, seedlings began yellowing. As disease progressed, black rot of the leaves and roots was common and eventually wilt and seedling death was observed. Seedling mortality was about 30%. The causal organism was isolated from the seedlings on potato dextrose agar media. A total of nine isolates were recovered and two representative isolates were identified as Fusarium asiaticum based on morphological characterization and phylogenetic analysis of the internal transcribed spacer (ITS) region, translation elongation factor (EF1–α) and RNA polymerase II (RPB2) genes. Pathogenicity and fungicide sensitivity were tested to confirm pathogen viability and control efficacy of the disease. The fungal isolate caused severe disease in the inoculated Hinoki cypress seedlings. Also, the isolates were sensitive to benomyl, hexaconazole and pyraclostrobin and showed reduced sensitivity to penthiopyrad. In planta assays showed 98.81 and 100% disease control by the application of pyraclostrobin and hexaconazole, respectively. The pathogen was re‐isolated from the inoculated seedlings and its identity was confirmed by morphological analysis fulfilling Koch's postulates. The pathogen‐causing disease in the Hinoki cypress is the first reported in the host worldwide.