Seed predation affecting the distribution of Araucaria angustifolia along an edge between forest and field

Authors

  • Izolete Guglielme
  • Gislene Ganade

Abstract

We investigated how the spatial distribution and the chances of establishment, growth and survival of Araucaria angustifolia (Araucareaceae) could be altered along an edge between an Araucaria forest and an old pasture in the National Forest of São Francisco de Paula, RS, Brazil. The study was performed in seven distances: 0, 25, 50, 100, and 250 m from the edge to the forest interior and 5 and 50 m from the edge to the old pasture interior. In each of the distances studied we performed: 1) a survey of adult trees, juveniles and seedlings in ten 5x5 m plots, 70 plots in total; 2) two seed predation experiments in April and July 2001 where groups of 15 seeds of A. angustifolia were randomly placed in each of the studied distances, using a total of 1050 seeds to monitored their seed predation rates; 3) seedling transplant experiment where 20 seedlings were transplanted in random points inside each studied distance, with a total of 140 transplants. Seedlings and juveniles were more frequent at the distances 0 m and 50 m from the edge towards the forest interior with an absence of these individuals at the old pasture. There was a significant decrease in seed predation rates at the distances 0 m and 50 m from the edge towards the forest interior. Transplanted seedlings have shown a lower percentage of mortality and higher growth at the edge zone, probably due to a higher occurrence of herbivory at the forest and old field interior. In conclusion, A. angustifolia performance was improved by the presence of a forest edge where it occurred more abundantly, and its seed predators and herbivores were less active. Although many works suggest that light may be a crucial factor defining A. angustifolia spatial distribution, this work indicated that natural enemies seem to be capable of defining the spatial distribution of A. angustiolia at the edge gradient studied.

Key words: edge effects, araucaria forest, seed predation.

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Published

2021-06-15

Issue

Vol. 1 No. 2 (2006): September/December

Section

Articles

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