Regeneration of Araucaria angustifolia in pine plantations in the South of Brazil – a silvicultural approach

Abstract

The formerly wide-spread Araucaria angustifolia forests in S-Brazil have been cut during the whole of the 20th century and were converted into pastures, agricultural fields and forest plantations of pine and eucalyptus species. Araucarias only remained in small woodlots, groups or as single trees. Therefore, they were legally protected. The objectives of this study were to investigate the distribution of Araucaria seedlings in pine stands in order to consider whether Araucaria seedlings can be used for transforming pine plantations into mixed stands. Seedlings and saplings were detected in loblolly pine (Pinus taeda) plantations of a medium sized enterprise by means of a systematic large-scale inventory. Although the seedlings and saplings were heterogeneously distributed, they could be used for mixtures of up to one third of the area. The numbers of Araucaria seedlings and saplings were highly correlated with the distance to secondary forests containing old Araucarias as seed-bearing trees, with the age and also the number of thinnings of the sheltering pines. Nevertheless, the dataset was zero inflated, being the basal area of the pine stands a significant factor in this context. From the ecological point of view, it would be advisable to reconsider the strict Araucaria protection rules in order to encourage land owners to make use of the natural regrowth for mixtures with pines. However, this would also need a revision of the management standards for pine plantations, including longer rotation periods and early as well as intensive thinnings.