Estrutura do componente arbóreo de um fragmento de Floresta Estacional Decidual e o vigor de sementes de espécies de diferentes categorias fitossociológicas

Abstract

The deciduous seasonal forests are poorly studied, yet no standards for their phytosociological structures, recruitment, establishment and dispersal of individuals. For the few studies in these forests do not show the results for the communities considered in areas of major climate change, as the northern state of Minas Gerais. The objective was to find relationships between community structure and rates of germination, germination speed and average time of germination, and test methodologies of experiments that can be important tools for further studies of the structure of deciduous seasonal forests, contributing to the standardization of procedures and comparison of results. This survey was conducted in the municipality of Januária/MG, which were sampled 1.2 hectares of deciduous seasonal forest and recorded 1083 individuals, distributed in 107 species and 80 genera belonging to 35 families. The analysis showed a total basal area of 27.85 m 2 /ha and individuals with height variations between 3.0 and 30.0 m. The most abundant family was the Fabaceae and genera with many species of Machaerium and Tabebuia. The floristic surveys associated with other techniques of analysis, like the tests of germination, may enable a breakthrough in understanding the behavior of ecosystems, helping to understand the adaptive success of species and allowing the understanding of the interactions of plants with microorganisms, with herbivores and other plants. Were selected among the 12 species surveyed, which were divided into two classes based on distinct phytosociological Value of Importance (VI) found in the phytosociological survey, namely: 1st class phytosociological with VI> 30.0 (M. urundeuva, C. Oligandrus, A. fraxinifolium, M. acutifolium, D. bipinnatum and A. colubrina) and 2nd class fitosociológica with VI <30.0 (M. pubescens, A. cearensis, T. aurea, C. americana, C. glabrata and P. Blanchet). These species were collected 1.000 seeds, according to availability at the time of the study. These seeds were tested for germination in complete randomized design with four treatments and five replications, under regulated conditions of 30° C day and 20º C night, with a photoperiod of 12 hours. In general the species in each class did not show similar behavior, which have not occurred for family groups. The species of the family Anacardiaceae (M. urundeuva and A. fraxinifolium) 3 showed the largest IVG’s, with peaks of germination in the first three days of the experiment, with positive effect of immersion between treatments. The seeds of A. cearensis and P. Blanchet (Fabaceae) showed positive effect of water on germination original, not affecting the viability of these during the time of the experiment. The species A. colubrina and M. acutifolium (Fabaceae) had a positive effect of water on germination, but showed a decrease of peak germination for treatments of imbibition. In the family Sapindaceae species D. bipinnatum and M. pubescens showed different behavior are not observed the influence of imbibition to the first. The behavior of other species belonging to the families Boraginaceae, Euphorbiaceae Dilleniaceae and proved to be different, with the formation of distinct groups. The T. aurea (Bignoniaceae) showed similar behavior to the species of the family Anacardiaceae. In general, we find two distinct effects of water on the seeds, (i) the initial stimulus to germination and (ii) the decrease in germination with increasing time of imbibition, probably due to the destruction of the seed. The highest rates of germination of the species of the families Fabaceae and Anacardiaceae seem to be influencing the size of populations, but without detriment to other factors that influence the establishment of these. The phytosociological classes do not have a pattern of similarity to justify the structural arrangement of the population for this study.