Relações entre assembleias de insetos aquáticos e o uso e cobertura do solo em riachos inseridos em matriz agrícola na região Centro-Oeste do Brasil

Abstract

This work investigated both the composition and the effects of land use and cover in assemblies of aquatic insects in streams in the Dourados river basin. The hypothesis of this work is that the use and cover of the soil (whatersheds and riparian zones) influences the morphology of the channels, the physicochemical variables of the water and the composition of the aquatic insect assemblages in streams inserted in the agricultural matrix (sugarcane). Organisms and environmental variables (structural and physical-chemical) were collected in nine low-order streams subdivided into three groups of land use and cover, with three streams inserted in Forest Fragments (REF); three inserted in whatersheds with use and cover of the soil predominantly of the culture of sugar cane, and with low percentage of riparian forest (LFSC = Low Forest + Sugar Cane); and three streams inserted in agricultural areas with predominance of sugar cane and without the presence of riparian forest (NFSC = No forest + Sugar Cane). The structural variables showed a significant difference between the groups of land use and coverage, but there were no significant differences in relation to the physical-chemical variables. In relation to aquatic insect assemblages, streams inserted in areas with use and coverage of agricultural soil showed lower taxonomic richness, abundance and EPT indexes. Significant differences were found for both wealth and abundance between groups of land use. There was also a correlation between aquatic insect composition and land use and cover, and between insect composition and structural variables. Therefore, we conclude that the use and cover of the soil, mainly for the cultivation of sugar cane, influences the structural variables and consequently in the composition of the aquatic insect assembly in streams of the Dourados River basin.Furthemore, the low percentage of forest in riparian zones is not sufficient to maintain ecological conditions conducive to insect communities in these streams, which is reflected in their taxonomic richness.