Avaliação do potencial invasivo de espécies não-nativas utilizadas em plantio de restauração de matas ciliares

Abstract

The restoration of the ecosystems has been increasing worldwide. The most widely used model in Brazil has been the planting of the high diversity tree species. Although the recommendation it is planting only native species during restoration, the difficulty to identify them and to find seedlings available, result in many planting are found non-native species, which offer the potential threat of biological invasion. The purpose of this study was to analyze the potential of invasive non-native tree species that have been planted to riparian forests restoration in the region of semideciduous forest, based on the structure of their populations in regeneration. We selected 25 areas in restoration, of the aged between 4 and 53 years after planting. At each site we carried out the floristic inventory in the total area of 1.000 m2, divided into ten plots randomly distributed, within the range of 0 to 50 m away from the edge of the water body. Identify and account for individuals of all tree and shrub species present in the understory, from 50 cm tall, grouped into three size classes by diameter at breast height (DBH < 1 cm, 1 cm < DBH < 5 cm and DBH > 5 cm) . We classify the species planted and regenerating based on the alignment of planting, evident even in the oldest plantation. In total, 18.421 individuals sampled, belonging to 320 species. Regarding the origin of the species in plantations, 65% are native FES, 19% are of other native vegetation formations in Brazil and 16% are from other countries. Only three areas were not planted non- native species. In other areas, non-native species were used in varying proportions, to a maximum of 54% of all species sampled from planted trees in a community restoration. The proportion of individuals of non-native species from regenerating plants (12%) was lower than the proportion in which the non-native trees were planted (17%). We found that the proportion of regenerating non-native communities in restoration tends to decrease with time, especially due to the increasing inflow of native immigrants (not planted). Analyzing the contribution of each species in structuring the community, 78% of total non-native plants let a very small number of offspring, relative density less than 1% of individuals in regeneration. Only 22% (17 species) of non-native had a relative density higher than the density of regenerants that were planted. Thus, only these species have potential for biological invasion, should be avoided your inclusion in ecological restoration projects in areas of FES. Only two among the 83 sampled non-native species (Acacia tenuifolia and Clausena excavata) formed large populations, with tendency to dominate the communities in which they are. Based on the results we consider that for the vast majority of non-native species, their inclusion in projects of the restoration does not pose a risk to native biodiversity. However, there are exceptions that deserve immediate restrictions of cultivation and management until experimentation for the control of their populations.