The effects of reduce-impact logging on fruit-feeding butterflies in Central Amazon, Brazil

Author(s)

Danilo Bandini Ribeiro

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2011-08-07

Examining board members

André Victor Lucci Freitas; Thomas Michael Lewinsohn; Helena Romanowski; Ronaldo Bastos Francini; Flavio Nunes Ramos

• Advisor: André Victor Lucci Freitas

Abstract

The Amazon region represents more than half of the area of all tropical forests in the world, and has been threatened by many anthropogenic activities, including several kinds of timber harvesting. Reduced-Impact Logging (RIL) is considered a less destructive method of timber harvesting that promotes a smaller change in forest structure than conventional logging. However, there is a general lack of information about the effects of RIL on Amazonian invertebrates, including butterflies. We therefore investigated the effect of RIL on forest vegetation structure and on fruit-feeding butterflies by comparing their distribution on canopy and understory between an area under RIL and a control area without RIL. Because of the relative lack of information about sampling protocols for tropical butterflies, some methodological aspects of fruit-feeding Nymphalidae sampling were investigated. We analyzed the variation in detectability among species, habitats (Amazon x Atlantic Forest), layers and the adequate sampling effort need for detect an specific amount of species in a given area were analyzed in this thesis, in the present study this amount was established as 25% of the total estimated species richness. Biological implications An unlogged forest has bigger juveniles and adult trees, and less seedlings and saplings than a RIL forest, and the Size Frequency Distribution (SDF) slope was not different from those of logged (-2.61) and unlogged (-2.31) areas. The canopy openness was greater in the unlogged forest, probably due to an increase of understory plants in the RIL forest. The basal area was wider and the height was taller in unlogged forest trees. In relation to the fruit-feeding butterflies, the canopy fauna is different and significantly richer than the understory fauna, showing that sampling only the lower strata underestimates the diversity of fruit-feeding butterflies. The effects of RIL were mainly detected in the understory butterfly assemblage, as significant differences were observed in species composition within this stratum. Effects of the RIL regime, which include tree cutting, skid trails and road openings, are stronger in the understory than in the canopy, explaining the reported differences. Despite the detectable effects of RIL on the composition of fruit-feeding butterfly's assemblages the overall diversity was not affected, this pattern is very similar for many other taxa indicating that a noticeable part of the diversity of many taxa could be preserved in areas under RIL management. Given the problems of creating protected areas in the Amazon, RIL is a good alternatives to preserve fruit-feeding butterflies and surely many other taxa, and it might be a desirable economic alternative for the region. Methodological implications Almost all butterflies and moths sampled in the present study were more readily trapped in one specific stratum. Indeed, in the present study, even the most common canopy species were rarely sampled in the understory. Thus, using a sampling protocol that does not locate traps in both layers will increase the imperfect detection of many butterflies and could lead to incorrect inferences about the richness and diversity in a given area. The differences in detectability between months in the Amazon dataset showed that even with an experimental design planned for sampling butterflies during the period that enhances capture probability, there are important differences in butterfly detectability across months. The low detectability and great variation among strata and months in fruit-feeding butterflies lead us to assume that sampling designs must address sampling effort to the correct season and strata reducing imperfect detections and biases in the results. The minimal sampling effort for detecting 25% of the species present in tropical forests is 130 trap/days in Atlantic Forest and 510 days in Central Amazon. Additionally, such sampling should use temporal replication over a short period to improve the interpretability of the data collected (AU)