Dinâmica da regeneração natural de uma floresta secundária, submetida a tratamentos silviculturais em Bragança-Pa, Brasil.

Abstract

Studies that contribute for the knowledge and improvement of techniques for vegetal resources use and sustainable management in secondary forests are still very scarce in Amazon region. To get technical subsidies that can contribute in solving this matter, management techniques were tested in a secondary forest arca, with the objective of evaluating the influence of silvicultural treatments over natural regeneration, in an experimental arca in the municipal district of Bragança, Pará state, Brazil. For the analysis of natural regeneration, within each arboreal monitoring allotment (50 x 50m), 4 sub-allotments of 5m x 5m were installed (0,0025 ha) for sticks measuring and rods counting. Within each sub-allotment a range of Im x 5m (0,0005 ha) was drawn for seedling counting. Two allotments, named TI, or treated arca, were submitted to silvicultural treatment, consisting of: vine cutting, tree thinning by girdling and killing, and two didn't receive silvicultural intervention, named TO, or control arca. Used categories were named seedlings, rods and sticks. Individuais with DAP equal or bigger than 2,5 cm and smaller than 5,0 cm were considered sticks, which were labeled and numbered. Ali individuais with DAP equal or smaller than 2,5 cm and height bigger than 1,5 m were rods. Ali individuais with height equal or higher than 30 cm and equal or lower than 1,5 m were seedlings. Fabaceae was the family with larger number of species during the observed period, and Eschweilera coriaceae was the species with larger density. In relation to the ecological group, it was observed that the pioneers species were dominant over the climáxicas species, both in TO and TI plots. The values of floristic diversity found in this paper were considered low, where the category that showed higher diversity was seedling. In TO, Eschweilera coriaceae presented higher ingrowths and Myrcia silvatica and Talisia sp. higher mortality. Altough in TI, Cupania scrobiculata obtained higher ingrowths and Doliocarpus sp. higher number of the dead individuais. Eschweilera coriaceae and Ambelania acida stood out for presenting higher basal arca at the end of the study. In relation to the annual diameter increment average, Psidium guianensis, Tabebuia serratifolia (TO), Talisia longifolia, Myrcia silvatica (TI) had the highest values. The results found in this study made possible to conclude that silvicultural treatments did not influence relevantly in the dynamics of natural regeneration.