Influência da monocultura de eucalipto sobre a vegetação campestre em área de Pampa no sul do Brasil

Abstract

The establishment of monocultures of eucalyptus is criticized and regarded as responsible for soil degradation and significant biological changes. In Rio Grande do Sul, south Brazil, the conservation of grasslands is confined to areas of permanent preservation - APP's, defined by current legislation as the riparian vegetation extending 30 m from both sides of watercourses. This study investigates the possible changes induced by eucalyptus plantations on adjacent grassland APPs. The study was conducted in Formosa ranch, located in the municipality of São Gabriel, RS. Three areas with the interface between eucalyptus plantations and grassland APPs, and three other areas without eucalyptus plantations (control areas) were chosen for the study. A total of 120 1 m2 plots were randomized along linear transects established at 5 and 30 m from the edge of the APP both to the APP itself and towards the plantation interior (in areas with plantations) or towards grasslands outside APPs (in control areas). A grid of 10 by 10 cm was used to assess the cover-abundance of all vascular species present at each plot revealing a total of 145 plant species. The richness and diversity of species showed the same trend for areas with eucalyptus: inside plantations species richness was greater in the edge, while in the adjacent APP species richness did not present a clear distance gradient. Such a distinction between APPs and areas distant from APPs was not detected in control areas. In conjunction these results suggest a possible effect of the plantation upon the species richness of adjacent APPs. The composition and coverage-abundance varied significantly among the areas studied . Environmental factors such as soil humidity and compaction, and relief slope were important in determining the composition and abundance of species in APPs. This study shows that the maintenance of APPs do not suffice to preserve the integrity of grassland vegetation.