Resposta inicial de uma floresta natural de terra firme na Amazônia Oriental brasileira após exploração de impacto reduzido e tratamentos silviculturais.

Abstract

We evaluated the effects of silvicultural treatments on the growth of a natural upland forest exploited using low impact techniques. The study was conducted at the Forest Management Area (MPA) in Rio Capim, owned by Green Timbers Cikel Brazil Ltda. Located in the municipality of Paragominas, state of Pará. The experiment was established in 2005 after holding the Reduced Impact (EIR) completed in 2004. We selected Work Units (WU), which were divided into four square plots of 25 hectares, making the repetition of experimental treatments. The experimental area amounted to 500 hectares, five treatments were established (100 ha each) with four replications. The statistical design was completely randomized. We tested the foliowing treatments: T1: thinning release classic and cutting vines, T2: modified release thinning and vine cutting, T3: only cutting vines, T4: only holding; T5: non-exploited forest. We determined the growth of trees through IPADAP (annual periodic increment in dbh) in four periods: 2005-2006, 2006-2007, 2007-2009 and 2005-2009. Protium subserratum was the species with the highest growth rate in diameter, throughout the monitoring period, ranging from 0.46 cm yr-1 (T5) to 0.69 cm yr-1 (T3). Pouteria bilocularis Eschweilera and Amazon had the lowest IPADAP, ranging from 0.10 em yr-1 (T5) to 0.25 em yr-1 (T4) and 0.12 cm year-1 (T5) to 0.25 cm year -1 (T3), respectively. In trees with crowns fully exposed to solar radiation, were recorded IPADAP larger than those partially and fully shaded in all experimental treatments in four periods. Trees that received scattered light had rates similar to those IPADAP fully shaded. Trees with crowns had normal complete IPADAP significantly higher in all experimental treatments, the four evaluation periods, trees with full crowns irregular or incomplete. Trees free of vines had higher IPADAP in five treatments and four experimental periods, than individuals with vines without causing damage or growth restriction. The growth in dbh of trees with lianas, however, without causing any apparent damage had IPADAP rates similar to trees with vines constraining growth. In the four years of monitoring forest after harvesting and application of silvicultural treatments, T2 (modified release thinning and cutting of lianas) and T3 (only cutting vines) had the highest growth rates in diameter. However, the period of four years is not enough to indicate treatment "most appropriate", based on diameter growth in response to girdling trees and vine cutting.