Monitoramento de uma encosta reflorestada com leguminosas arbóreas na Mata Atlântica após 17 anos do plantio

Abstract

The direction of the Portogalo condominium and the researchers of the Brazilian Agricultural Research Corporation carried out the revegetation of deforested slope in 1992, aiming to decrease erosion, restore the scenic beauty and provide value to the condominium's landscape. Ten species of legume trees were inoculated with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi and introduced in the slope. A study aiming to evaluate the performance of the revegetation initiative was carried out in 2000. The biometric parameters of the plants, soil and litter chemical attributes, and biological indicators were measured. This second study aimed to re-evaluate the revegetated site after 17 years based on the plant successional process, seed bank, soil fertility, nutrients in the litter and soil fauna. An area with the grasses Melinis minutiflora P. Beauv. and Imperata brasiliensis Trin., which represents how the revegetated site would be if human intervention had not been done, and a secondary forest site nearby, were used for comparison with the revegetated site. The secondary forest site might have been a source of plant propagules. The introduction of legume trees was efficient in promoting the plant succession in the sites since the evaluated parameters were similar to those measured in the secondary forest site. The floristic composition presented a low similarity to the revegetated portion and to the secondary forest portion, as measured by the index of Jaccard. Guarea guidonia and Nectandra membranaceae were the only species found in the regenerative stratum in 2000 that were also found in the mature stratum in 2010 in all revegetated parcels. The seed bank indicated that the community is able to selfregenerate in case of disturbance. Cecropia pachystachya was the most abundant species in all parcels, except in the parcel with grasses. The introduction of legumes was an efficient conditioner of the substrate as indicated by the fertility levels similar to those found in the secondary forest. The highest biomass and nutrient stocks in the litter were generally found in the revegetated site. The highest diversity of soil fauna was found in areas covered with forest, and it was similar between the secondary forest and the revegetated sites, indicating that to use legumes was an efficient way to promote the recolonization of the revegetated area. The soil fauna community was consolidated with the increase in the diversity and richness during the last 10 years. The decrease in the Collembola group was a good indicator of plant diversity increase, which was mirrored in a higher uniformity of the groups of soil fauna.