Fire Chronology Drives Understorey Diversity but Not Regeneration Dynamics in Himalayan Chir Pine Forests

Fire is reshaping forest composition across the Himalayan region, yet post-fire regeneration mechanisms remain poorly understood in the global South. Chir pine ( Pinus roxburghii ) forests account for 95.56% of Bhutan's recent fire-burned area, making them a critical test case for fire-adapted regeneration in resource-limited mountain ecosystems. This study identified a fundamental decoupling between soil recovery and vegetation succession across contrasting fire chronologies. We surveyed 60 nested plots across two sites in Wangdue Phodrang: one burned in 2019 (five-year recovery), and one burned in 2025 (recent burn). Non-metric multidimensional scaling revealed significant compositional differences between sites (PERMANOVA: shrubs F  = 3.78, p  = 0.001; herbs F  = 5.94, p  = 0.001), with the older burn site exhibiting greater herb diversity (H' = 2.04 vs 1.74). Recently burned areas showed significantly elevated pH (6.13 vs 5.84), electrical conductivity (0.07 vs 0.05 dS/m), and available potassium (248.21 vs 9.29 mg/kg), reflecting ash deposition. Critically, Spearman correlation analysis revealed weak, non-significant relationships between regeneration density and all soil properties at both sites ( p  > 0.05). Pinus roxburghii seedling and sapling densities were statistically equivalent across sites ( p  > 0.05), demonstrating remarkable regenerative resilience regardless of soil nutrient variation. This study provides the first integrated assessment of post-fire regeneration mechanisms in Bhutanese forests and reveals that natural regeneration operates independently of soil chemistry. These findings fundamentally challenge the global assumption that soil remediation is a prerequisite for forest recovery. In resource-limited mountain regions facing climate-driven fire intensification, this evidence that early regeneration success depends on microsite conditions and seed availability rather than edaphic restoration has transformative implications: managers must abandon costly, disruptive soil rehabilitation programs and instead protect the non-edaphic drivers of recovery, microhabitat complexity, natural seed dispersal, and minimal soil disturbance. By privileging nature-based recovery over engineered intervention, mountain forest management across the Himalayan region can achieve better ecological outcomes with far fewer resources, offering a scalable recovery pathway for the millions of hectares of fire-impacted forests facing unprecedented climate pressure globally.