Does forest management reduce wildfire severity? Evidence from 1050 plots in a South Korean Megafire

Increases in large wildfires are commonly attributed to climate change, an attribution well supported in summer-dry regions such as western North America. In the East Asian monsoon region, however, national fire trends have diverged under broadly similar warming: forest fire activity has declined in China and Japan over recent decades, whereas in the Republic of Korea the risk of large fires has increased and the largest fires on record have all occurred since 2000. This divergence suggests that warming alone does not account for regional trends and that country-specific factors, including the composition and management of forest fuels, may also be involved. In Korea, decades of forest tending ( sup-gakkugi ) have removed broadleaf regeneration from beneath pine canopies. We examined whether this practice is associated with fire severity within a single large fire—the 2025 Gyeongbuk wildfire—by surveying 1050 plots in 34 spatial clusters selected from Sentinel-2 burn-severity maps to provide locally comparable site conditions, so that plots shared the regional climate and fire weather. Tended stands burned more severely than untended stands. Crown fire occurred in 54.2% of tended conifer plots versus 4.9% of untended conifer plots. In a cumulative-link mixed model with a random intercept for cluster, adjusted for forest type, elevation and topographic position, the odds of a more severe fire state were about 15 times higher in tended stands (OR = 15.2, 95% CI 8.0–29.1); cluster-robust and bootstrap estimates were similar with wider intervals, and the association persisted, at smaller magnitude, in within-cluster contrasts (crown fire OR = 8.7, 95% CI 1.7–43.4; canopy-tree mortality +17.4 %age points, 95% CI 6.4–28.4). Crown-fire occurrence increased with conifer proportion (OR = 5.3 per SD) and decreased with the cover of the broadleaf sub-canopy (OR = 0.32 per SD). Field assessments agreed with satellite dNBR (Spearman ρ = 0.71). Tending was also associated with higher mortality in broadleaf stands where crown fire was rare, suggesting an additional pathway, possibly through altered stand microclimate. These results are consistent with the hypothesis that a living broadleaf sub-canopy impedes the transition from surface to crown fire, and indicate that tending that removes this layer may increase fire severity in Korean pine forests. Because tending was not randomly assigned and untended stands were scarce and spatially clustered, the estimates should be read as strong associations rather than causal effects, and the study does not test whether tending has contributed to national fire trends.