The usage of species abundance distribution to evaluate changes in the diversity of managed tropical forests

Abstract

Amazon tropical forests have high biodiversity and have been managed for the purposes of timber supply. Traditionally, conventional logging (CL) has been used as the main exploration system, but since 1980's, the reduced impact logging (RIL) practices have been adopted. The impacts of management can be evaluated by measuring permanent plots. Some variables related to the impacts of forest management are already well described, but changes in biodiversity not. The majority of studies evaluating RIL and CL impacts on tree community diversity have performed diversity indices and florist composition. These comparisons have constraints when the objective is to compare the two exploration methods or verify tree community dynamics over time. Species abundance distribution (SAD) is receiving increasing attention again, because it is a pattern that is maintained by all biological communities. As a pattern, it can be described by a probability function with parameters. In this study we analyse the curve shape change of SAD comparing two types of forest exploration techniques (RIL and CL). The analysis of data will be obtained from of an experiment conducted in a tropical forest in Brazil. In 1993 three permanent plots were established and all tree individuals with diameter at breast height (dbh) greater than or equal to 25 cm were measured and identified. In 1994, in the first plot was harvested through CL, and the second plot by RIL and the last plot was maintained as a control without exploration. The plots were then measured again in 1994, 1998, 2000, 2003, 2006, 2009 and 2014, recording the presence of any new individuals according to inclusion limit. For the present study, bivariate poisson lognormal distribution will be considered to describe pairs of observation in different times. This distribution has sigma_1 and sigma_2 which can be used as measure of diversity and rho, which represents similarity between communities. (AU)