Influência da exploração madeireira na estrutura do hábitat e diversidade das assembleias de peixes de riachos na amazônia oriental

Abstract

Logging is one of the main activities responsible for the deforestation in the Amazon and is considered an important threat to biodiversity in this region. However, the international market demand for sustainable forest products has resulted in a partial substitution of the conventional exploration method (CE) with the reduced impact exploration (EIR) technique, also considered an important strategy to minimize damages to the Amazon forest and its biodiversity. However, little is known about the effect of these activities on the structure and functioning of riparian ecosystems and their biological communities. In this sense, the present study aimed to evaluate the effect of different methods of logging on the structure of the physical habitat of streams and taxonomic and functional diversity of the fish assemblages of these environments, as well as the elaboration of multimetric indices that allow a rapid and robust evaluation of the ecological integrity of these environments. A total of 47 streams were sampled in the Rio Capim basin, 13 of which were in unexplored areas, 11 in EC areas and 23 in RIL areas. The habitat structure was characterized based on 19 environmental variables, later compared between the different exploration methods. The fish assemblages were sampled using hand net, with a standardized effort, and evaluated as to the composition and different components of the functional diversity. Both methods of logging resulted in changes in the structure of the physical habitat of the streams, however only in areas of CD these changes influenced the taxonomic composition of fish species. In RIL areas only variations in the relative abundance of fish species were observed in relation to the temporal exploitation gradient. Despite the above results, the presence of logging, be it EC or EIR did not affect components of the functional diversity of fish assemblages. However, changes in the habitat of rachis associated with the presence of logging had been directly related to the functional attributes commonly associated with generalist strategies of the species, which are common associated with altered environments. According to the multimetric indexes, streams in RIL areas presented better habitat integrity when compared to streams in CD areas, but still lower than habitat integrity in unexplored streams. On average, EIR areas also presented intermediate values ​​of biotic integrity, however, this differed only in areas of CD. In the studied region, RIL showed to be an interesting strategy to minimize alterations in riach ecosystems resulting from logging. However, the present study was conducted only on a local spatial scale, and considering areas that went through a single exploration cycle. However, changes in physical habitat show that EIR also influence the structure and consequently the ecological integrity of these environments, reinforcing the need for a greater number of studies to understand the real effect of this activity in these environments.