Temperate forest ecosystems in Korea are currently undergoing a successional transition from Pinus densiflora Siebold & Zucc. (evergreen conifer) communities to Quercus mongolica Fisch. ex Ledeb. (deciduous broadleaf) communities. This study aimed to assess interspecific differences in ecological responses to climate change [Representative Concentration Pathway (RCP) 4.5] by evaluating changes in ecological niche characteristics and species distribution. Controlled-environment experiments, principal component analysis (PCA), and MaxEnt species distribution modeling were employed to quantify and predict ecological shifts in the two dominant species under climate change scenarios. Both species exhibited increases in niche breadth and interspecific overlap under climate change conditions. However, Q. mongolica showed a more pronounced increase in niche breadth compared to P. densiflora, indicating greater ecological flexibility and adaptive potential to warming conditions. According to the MaxEnt model projections, climate change is expected to result in an approximate 30% reduction in suitable habitat for P. densiflora in lowland areas. In contrast, Q. mongolica is projected to expand its suitable habitat by over 80%, notably in both low-elevation (below 800 m) and high-elevation (above 1400 m) zones, without being restricted to any specific altitudinal range. Our findings suggest that climate change may increase ecological similarity between P. densiflora and Q. mongolica, thereby raising the potential for interspecific competition. This convergence in niche traits could contribute to an accelerated successional transition, although actual competitive interactions in natural ecosystems require further empirical validation. Consequently, Korean forests are likely to transform into predominantly deciduous forest ecosystems under future climate conditions.

Managed plantation forests are important for timber production and carbon sequestration, but their biodiversity value compared with unmanaged secondary forests remains debated. We compared vascular plant diversity between a managed Japanese larch (Larix kaempferi) planted forest (MPF) and a nearby unmanaged secondary Mongolian oak (Quercus mongolica) forest (USF) in the Garisan Leading Forest Management Complex, Hongcheon-gun, Republic of Korea, where stand age and site conditions were broadly comparable. Using Modified-Whittaker plots across 1–1,000 m² at five sites per forest type, we analyzed pooled species richness of total vascular plants, spring-active herbs, native species, and alien species, and estimated species accumulation using species–area slopes. We also examined taxonomic structure with hierarchical diversity partitioning and dominance patterns using rank–abundance curves. Total species richness was significantly higher in the MPF across all plot sizes, and species accumulated more rapidly with area than in the USF (b = 14.14 vs. 4.48). Spring-active herbs and native species were also richer in the MPF, with steeper species–area slopes. Alien species occurred slightly more often in the MPF but remained scarce in both forest types. The MPF had significantly higher within-family genus diversity, whereas within-genus species diversity did not differ. These results suggest that early understory control, periodic thinning, microsite heterogeneity, and the spring light window under deciduous larch can promote understory plant diversity in mid-aged managed plantations.

Tidal flats contain large sediment carbon reservoirs, but blue-carbon accounting has generally focused on soil organic carbon (SOC), whereas shell-derived particulate inorganic carbon (PIC) has rarely been quantified in unvegetated tidal flats. Here, we quantified SOC, PIC, and total carbon (TC) stocks in 0-50 cm sediment cores collected from three sediment facies (mud, mixed, and sand flats) in the Shinan tidal flats along the southwestern coast of Korea. Sediment facies strongly controlled carbon storage, with mean SOC stocks of 159.84, 72.06, and 28.31 Mg C ha−1 and mean PIC stocks of 26.46, 9.10, and 4.53 Mg C ha−1 in mud, mixed, and sand flats, respectively. PIC contributed 11-14% of TC across all facies. Factorial ANOVA showed significant sediment-facies effects on SOC, PIC, and TC, whereas depth (0-50 cm) was not significant. The sediment facies x depth interaction was significant for SOC and TC but not for PIC, suggesting that the vertical distribution of organic carbon varied among sediment types. These results demonstrate strong spatial heterogeneity in sediment carbon storage across tidal-flat facies and indicate that PIC can represent a durable, non-negligible component of sediment carbon inventories. In this study, PIC is interpreted as a sediment carbon stock rather than a net atmospheric CO2 sequestration flux.

Korean tidal flats are gaining attention for their high potential as blue carbon storages, but research on vegetated areas remains limited. To address this gap, this study examined the vertical distribution of soil organic carbon (SOC) in halophyte-vegetated tidal flats on Korea's west coast and investigated how plant life form, biomass allocation, and belowground structure are associated with SOC accumulation and stabilization, using measurements of plant organ biomass and SOC at multiple depths. The results showed clear differences in SOC distribution among vegetation types. SOC in perennial herbaceous plant communities was 1.2 times higher than that in annual herbaceous plant communities. Furthermore, in tidal flats dominated by perennial vegetation, the contribution of belowground halophyte-derived organic carbon to soil organic carbon increased in proportion to belowground biomass organic carbon (p < 0.001). In vegetated areas, belowground carbon (BGC) showed the strongest association with SOC accumulation among the vegetation-related variables examined, and differences in SOC distribution among plant communities reflected variation in belowground biomass allocation and structure. These findings demonstrate that the vertical distribution and stabilization of SOC in vegetated tidal flats are closely linked to halophyte belowground productivity and highlight the potential for targeted restoration and management of perennial herbaceous vegetation to enhance blue carbon storage, thereby contributing to climate change mitigation and the long-term resilience of coastal ecosystems.