Estrutura etária e crescimento de Araucaria angustifolia (Bertol.) O. kuntze num gradiente floresta-campo em São Francisco de Paula, RS

Abstract

This work was developed at the Centro de Pesquisas e Conservação da Natureza (Pró-Mata), located in the municipality of São Francisco de Paula (29º28’S; 50º13’W), the northeastern of Estado Rio Grande do Sul, in a forest-grassland mosaic habitat. Vê of this study was to evaluate for signs of historical advancement of Forest based on age structure and growth performance of Araucaria angustifolia in a forest-grassland gradient. The Araucaria angustifolia is a species to present annual growth rings well defined is indicated for dendrochronological studies. In this sense, we selected 21 sample points in area of approximately 25 ha, randomly selected from three levels of distances. (1) points in the forest more than 50 m away from the nearest edge, (2) points in the forest or grassland up 50 m away from the nearest adge and (3) points on the grassland with more than 50 m away edge. To dendrochronological analyzes, at each point was selected for individual class diameter at breast height to collect two to four samples of wood with increment borer. Age had influence on tree size, explaining 43% of the variation of stem diameter (P= 0.001) and 12 % of the variation in height (P= 0.114). It was concluded that the structure age and height growth of A. angustifolia vary in forest-grassland gradient. In the laboratorio samples were fixed on a Wood France and polished with a series of sandpapers, and analyzed with help of a stereomicroscope. Later, we performed linear regression analyzes and randomization to assess how the age and growth (height and diameter) individuals vary in distance from the forest-grassland edge. The results showed that the age structure and growth performance of A. angustifolia varied along the gradient forest-grassland. Age of A. angustifolia ranged from 12 to 106 years, decresing from the interior of the forest for the interior grassland, the position of the trees 15 % of variance explained group (P= 0.0823). Age had influence on tree size, explaining 43% of the variation of stem diameter (P= 0.001) and 12 % of the x variation in height (P= 0.114). It was concluded that the structure age and height growth of A. angustifolia vary in forest-grassland gradient.