Comportamento de árvores potenciais para futuras colheitas em uma floresta ombrófila densa submetida à exploração de impacto reduzido e tratamentos silviculturais no município de Paragominas, Pará, Brasil.

Abstract

The abundance, basal area, mortality and growth rate oftrees (DBH >35 cm) selected (good shape and healthful) and treated for the next harvests (Potential Crop Trees - PCT) was evaluated, aiming to understand the effects of logging and silvicultural treatments on those selected trees performance. The study was carried out in a 700 ha sample area ofnatural forest in the Rio Capim Forest Management Unit, in the municipality of Paragominas, state of Para. The area was logged in 2004 using techniques for reducing logging impacts; it was treated (girdling trees and climber cutting) in 2005 and it was monitored until 2011. It was evident by the analysis of the results íhat the numbers of PCT were kept similar during the entire study period in the logged samples where the trees were treated. It can be suggested that the PCT, even having mortality, constitute a growing stock for the next harvests. In the entire study period the higher growth rate of PCT occurred in the logged and treated samples with no significantly difference between them. The trees treated by crown liberation thinning (tree girdling or climber cutting) grew more than those that were not treated, then one can conclude that the period ofthe next cut cycle can be reduced. This also is true for the PCT from those species that were logged seven years ago. The growth rate of big trees was significantly different from the growth rate ofthe small trees, ensuring a stock with big trees for the next harvests. The shape and distribution of the crown of PCT, as well as it exposition for solar radiation, increased significantly the diameter increment ofthese trees in relation to that with irregular and shaded crown with climbers. Therefore some silvicultural activities as climber cutting are needed to boost the growth rate ofthose trees that constitute the stock for the next harvests, reducing the cut cycle that was previously established.