Nationwide Assessment of Environmental Drivers of Vegetation Restoration Across Disturbance Types and Recovery Phases for Adaptive Forest Restoration and Management

Understanding the mechanisms of vegetation recovery following severe ecological disturbances is essential for effective forest management. The relative importance of environmental predictors across different disturbance types and temporal phases remains poorly quantified. We utilized a comprehensive nationwide dataset of 194 restoration plots in South Korea to evaluate the factors influencing total vegetation cover. We employed random forest regression models to analyze topographic, soil, and stand structural variables across four disturbance types and two recovery periods. Model performance revealed that short-term recovery and mechanically unstable roadside slopes are highly stochastic and strictly limited by physical terrain features, including elevation and slope. Conversely, the long-term recovery phase and severely degraded environments, such as mined sites, are strongly associated with biological structural traits and soil nutrient dynamics. Partial dependence plots demonstrated severe non-linear threshold mechanisms where total cover exhibited a sharp positive response to canopy height in quarries and an abrupt negative response to high soil carbon-to-nitrogen ratios during long-term recovery. These results indicate that structural canopy facilitation and microbial nutrient immobilization co-develop with advanced community expansion rather than acting as independent drivers. Ecological restoration strategies must therefore transition from immediate physical site stabilization to proactive soil nutrient management and canopy facilitation as succession advances.