Entomofauna associada aos sistemas de pastagem convencional e silvipastoril

Abstract

A major challenge in global agriculture is the reduction of the environmental impacts caused by meat and dairy production. During the last few years, the conversion of monocultural pastures to silvopastoral systems has emerged as an important ally in this process, with the aim of increasing the sustainability of cultivated and natural pastures.In order to understand the effects of this conversion it is essential to understand how the change affects the insect fauna in the different systems. In this study we characterised the insect fauna associated with a conventional Brachiariadecumbens pasture and a silvopastoral system consisting of 30 m strips of B. decumbens alternated with the tree species Acacia mangiumWilld and Eucalyptus grandisW. Hill ex Maiden, planted in 3 m spacing in 10 m strips. The study was carried out in Coronel Pacheco, Minas Gerais, Brazil, between January 2010 and December 2013, giving a four year sampling period. The aim of this study was to determine whether the changes caused by the conversion from a B. decumbens monoculture to a silvopastoral system affect the abundance, richness and diversity of the insect orders found in the two systems. In order to understand how the families within different orders respond, the two most abundant orders in the silvopastoral system (Hymenoptera and Hemiptera) were studied separately. We detected important differences in the insect fauna at the order level, indicating significant changes in community structure. For Hymenoptera, our results show that the changes due to conversion from monoculture to a silvopastoral system changes species composition. In particular Formicidae and Pompilidae are good candidates as biological indicators, since they clearly responded to the system changes. In Hemiptera, there were differences in the richness and abundance of some families, but there were no changes in species composition, and no differences between the systems were found in total abundance and diversity. Therefore, Hemiptera should not be considered a promising biological indicator. In conclusion, the insect fauna showed clear differences after conversion of B. decumbensmonoculture to a silvopastoral system. Some groups showed important changes, and can be considered candidates for biological indicators, while other groups did not respond to conversion.