Population structure of Araucaria angustifolia under distinct forest protection status: implications for management and conservation

Araucaria angustifolia is the dominant coniferous species in Brazil, a long-lived pioneer species and a supplier of valuable timber and non-timber products, which gives it key-species status. This study examines how A. angustifolia population structure affects the stand structure, and whether these relationships differ between protected and unprotected areas. The study was carried out on two protection status forests (national forest and urban forest) in a region of Atlantic mixed forest in Paraná State, southern Brazil. Skewness coefficient and the Weibull shape parameter described the population structure and its effects on species diversity and biomass stock. Population diameter distribution differed significantly between forests, with unbalanced structure in both, although regeneration was more abundant in the protected area. Skewness positively affected aboveground biomass whereas shape negatively affected it and species diversity. These relationships differed between protected and unprotected stands. The effect of A. angustifolia populations on stand structure was conditioned on protection status. Old-growth populations may have lower diversity and biomass stock even supporting large trees. Consequently, old-growth forests, can lead to wood loss through mortality, senescence, and declining populations, representing the waste of a valuable timber resource. These findings provide useful knowledge for forest management, species conservation, and the carbon market.