Establishment and competition of native forest species in Araucaria angustifolia stands with different coverage degrees in Misiones Argentina

Mixed plantations with native species are a viable tool to meet current wood production and conservation demands that can contribute to the restoration of degraded forests. In Misiones, Argentina, 30000 ha are destined to mono-specific plantations of the native Araucaria angustifolia (Bertol.) Kuntze, for timber purposes. The mixes with other native timber species in uneven-aged plantations have ecological advantages over monospecific stands because they increase biodiversity and complexity. In mixed plantations, competition depends on the availability of resources, but also on the requirements and ages of the trees. Different ages of A.angustifolia plantations represent different coverage intensities, environmental conditions and understory structures, and can be used to protect the seedling of coverage-demanding species during the establishment. Six A.angustifolia stands of different ages, from 2y (1200 trees/ha) to 25y (220 trees/ha), were enriched with native forest species. In each stand, one 100m2 plot for each species was installed. Fifty seedlings of Cabralea canjerana, Peltoforum dubium, Bastardiopsis densiflora or Cordia trichotoma were planted per plot within the planting rows. One year after planting, survival was higher than 70% in all the species and mortality was not associated with the age of the stand. Survivals were not affected by frost although plants have been classified as frost-susceptible. However, growth was lower in the stand where the lower temperatures in winter were recorded. In the older stand, competition did not affect the survival and growth of the species with higher phenotypic plasticity, while it affected the growth of those that have lower plasticity. Results suggest that it is possible to enrich the mono-specific stands of different ages with native timber trees. Therefore mixed plantations of A.angustifolia with other native species can be considered for wood production and conservation purposes in their natural area of distribution, as they increase the connectivity between the remaining rainforests.