Adult longevity and a persistent seedling bank in Araucaria angustifolia: Evidence from historically logged forests

Protecting threatened tree species is essential, but long-term persistence also depends on the demographic processes that sustain population replacement. For long-lived species, sparse juveniles may signal recruitment failure or a life cycle spanning centuries. We investigated the demographic processes shaping population persistence in Araucaria angustifolia , a Critically Endangered conifer historically logged and now protected by cutting restrictions. We used adult (2008–2021) and regeneration (2011–2014) data in a Bayesian annual stage-structured model for one focal population, estimating survival, stage transitions, and recruitment. We compared adult density and basal area across eight Araucaria Forest remnants in southern Brazil. The focal population was close to stability (λ = 1.021 [1.001–1.055]; P(λ ≥ 1) = 0.98). Seedlings were abundant (1120–1480 ind ha⁻¹), but most remained in the same stage; estimated annual advancement was 3.3% and mortality 13.6%, locating the bottleneck after establishment. Population growth was most responsive to proportional changes in adult survival (elasticity 0.67), whereas equivalent changes in recruitment and stage advancement had smaller effects. The net reproductive rate exceeded one in most posterior draws but remained highly uncertain (R₀ = 7.3 [1.1–44.2]), and generation time was 95 years [61–184]. Adult araucaria basal area increased across all remnants, although density trajectories varied. The focal population retained long-lived adults and a persistent seedling bank, while regional adult populations showed no immediate evidence of structural decline. These findings reconcile slow juvenile advancement with population persistence: adult survival underpins current stability, whereas episodic juvenile advancement remains essential for long-term replacement.