Early plant community assembly in post-fire karst forests: Species-independent drivers and environmental adaptation rather than biotic interaction

Severe and recurrent forest fires threaten the structure, functioning, and stability of forest ecosystems globally. The early post-fire succession stage is critical for community assembly and vegetation reestablishment, yet the temporal dynamics of species interactions and community stability remain poorly understood, particularly in fragile karst forests. We investigated plant communities in severely burned karst forests in southwestern China across six early succession years (0.5–5 years post-fire), using unburned forest as controls(CK). We examined species composition, niche, interspecific associations, and community stability. Results showed that: (1) Species composition and richness changed dramatically, richness exhibited a unimodal temporal pattern that peaked at 1 year post-fire (123 species). (2) During early succession, species niches fluctuated, while mean niche breadth and overlap in the herbaceous and shrub layers slightly increased with succession time. (3) Interspecific associations were predominantly weak, with more than 90% of species pairs showing non–significant associations; over 81% of community-level connectivity indices across vegetation layers were non–significan. (4) Community stability was initially low but increased progressively, showing a directional trajectory toward a stable state. The findings suggest that early post-fire community stability in karst forests is primarily driven by species-specific responses to environmental conditions and their relative ecological independence, rather than complex biotic interaction networks. This study advances the understanding of post-fire ecosystem succession and highlights the potential of targeted restoration during the critical succession period to shorten succession time. Protecting and introducing ecologically valuable, resilient species with low potential for strong interspecific competition may facilitate positive succession.