Dinâmica da regeneração natural em uma floresta ombrófila densa após a exploração florestal de impacto reduzido na Amazônia Oriental.

Abstract

The knowledge of the natural regeneration mechanisms in logged forests is little yet, becoming a limit factor for application of forest management in those areas. The present study aiming to contribute for increasing the knowledge on dynamics of natural regeneration in a terra firme forest in Amazon, that was logged applying reduced impact logging techniques, considering two harvest intensities. The study area comprises 108 ha and it is located in the Rio Capim Forest Management Unit, which belongs to Cikel Brasil Verde Madeiras. In the 108ha, 36 0.25 ha (50m x 50m) permanent sample plots were randomly established, totaling a 9 ha sample. Three treatments were considered: T0 – unlogged samples; T1 – logged samples where the commercial boles were harvested; and T2 – logged samples where the commercial boles and the coarse woody debris (diameter > 10 cm) were harvested. From the 36 permanent sample plots, 12 were chosen at random to constitute T0; 12 to constitute T1 and 12 to T2. Each 0.25 ha plot were divided in 25 (10 m x 10 m) subplots, of which 5 were randomly chosen to evaluate the natural regeneration. In each of those 5 (10m x 10m) subplots, the small trees (5,0 cm < DBH < 10 cm) were measured; 5 cm x 5cm subplots were established in the center of those 10 m x 10 m subplots for measuring saplings (2.5 cm < DBH < 5.0 cm); and each 5 m x 5 m sample was divided in four triangles (each 6.25m 2 ), of which one was chosen at random for counting the seedlings (height > 30.0 cm and DBH < 2.5 cm). Data were collected in six occasions (2003 – before logging; and 2004, 2005, 2007, 2008 and 2001 – after logging) in an eight-year period. We analyzed the floristic composition, species diversity, floristic similarity, abundance and frequency of individuals with height > 30 cm and diameter < 10 cm. According to the results, we can conclude that the techniques of reduced impact logging are practicable for the sustainable management of the study forest and similar forests, considering that the timber harvested, as well as the coarse woody debris harvested or both of them did not change significantly the floristic composition, species diversity, floristic similarity, abundance and frequency of tree species in the natural regeneration, keeping the forest conserved.