Estrutura e relações ambientais de grupos florísticos em fragmento de floresta estacional subtropical

Abstract

The objective of this study was to determine floristic groups of the shrub-tree vegetation strata of an excerpt from Forest Subtropical Deciduous slope in Parque Estadual Quarta Colônia, Rio Grande do Soul, Brazil, to analyze their structure and to determine key environmental factors for plant species occurrence, in order to provide restoration programs of degraded areas as reference ecosystem. A phytosociological survey was carried out for vegetation analysis on 12 plots of 200 m2 (10 x 20 m), systematically distributed on a topography gradient at 20 m interval, systematically distributed on four tracks of 100 m between them, following the gradient of topography. In each plot, it species was identified and it was measured circumference at breast height (CAP) and overall height of tree individuals, represented by those with CAP 115 cm, named upper stratum. Understory strata information was obtained on circular plots of a radius of 1.78 m, set up in the center of 10 x 20 m plots, from individuals with height 30 and CAP<15 cm. Environmental variables were steepness, light intensity and soil chemistry and texture. Data analyses of vegetation structure and diversity were evaluated by using TWINSPAN and environmental correlations of floristic composition by using CCA (Canonical Correspondence Analysis). It was identified two groups, with species composition belonging to different stages of natural succession, suggesting differences of agricultural land use history and soil chemical characteristics. For that, some species may be indicated in forest restoration programs.