Avaliação florística e estrutural de uma Floresta Ombrófila Mista e de uma vegetação arbórea estabelecida sob um povoamento de Araucaria angustifolia de 60 anos

Abstract

This research had as objective evaluation the floristic and structural of a Mixed Rain Forest and arboreal vegetation under an Araucaria angustifolia stand of 60 years, located in the National Forest of Irati, Paraná State - Brazil. A research area (A) of 10 ha was installed in an araucária stand, and other (B) of 25 ha in a forest. This areas was structured in continuous blocks of 1 ha (100 x 100 m) divided in plots of 0,25 ha (50 x 50 m). Using control strips of 10 x 50 m in the plots, each arboreal individual was numbered, identified, mapped, and measured DBH above 10 cm. They were found 124 species in the total, 79 in the area A and 108 in the area B, of which 63 species in common. Ilex paraguariensis, Ocotea odorifera and Araucaria angustifolia were the species of larger occurrence in the area B, while the area A presented Myrsine umbellata, Psychotria vellosiana and Casearia sylvestris. The Shannon’s indices calculated for the 10 blocks in the area A were statistically equals, and for the 25 blocks in the area B, presented significant differences, tested by analysis of variance. The Hutcheson test showed statistical difference among the Shannon’s indice of area A (H'=3.17) and of area B (H’=3.55). The diametric distribution from arboreal individuals under the araucária stand (A) was shown less variable than individuals of Mixed Rain Forest (B), being more concentrated in first diameter class (10 to 15 cm). Appling the Kolmogorov-Smirnov test, it was verify statistically that the 10 blocks in area A presented none similar diametric distribution to the 25 blocks of area B. The araucária planting had unimodal distribution, typical of even age forest, with 297 trees/ha with basal area of 30.2 m²/ha, while in natural environment (area B) the specie did not possess define distribution, being the frequency smaller than the area A (42.1 trees/ha) and as consequence basal area 7.68 m²/ha. With clustering analysis 6 groups with similar covering values were constituted. With discriminant analysis it was selected by stepwise 12 variables (species) being able to discriminate the ambient (formed groups). Accomplishing the fitossociological analyses of the formed groups the following associations were identify: association with Araucaria angustifolia stand I and II, association Nectandra grandiflora, association Ocotea porosa, association Ocotea odorifera and association Matayba elaeagnoides. In each group a block was selected for spatial structure analysis using Ripley’s K function. The groups of the area A had spatial random when appraised all the individuals, while the clustering pattern was identified in the groups of the Forest. It was identified a regular pattern of the araucárias in the two groups of the research area A, in a scale of up to 10 m. In the area B, the appraised species accompanied the pattern of distribution of the groups in general. The spatial dependence was revealed in some cases showing tendencies to attraction between two species and repulse for others.