Indicadores da restauração de áreas degradadas na Reserva Biológica de Poço das Antas, RJ

Abstract

Mixed plantations of indigenous tree species have been widely used in the restoration of degraded Atlantic forests which had been converted to pastures. This study used ecological indicators to evaluate the status of restoration in mixed plantations at the Poço das Antas Biological Reserve, Southeastern Brazil. Study sites involved mature forests (F), 8-year-old mixed plantations of indigenous tree species (P), and abandoned pastures (G), at both the flooding areas (V) and the sloping (M) of the Reserve. Soil analysis were collected at the layers 0-2.5cm; 2-5-7.5cm; and 7.5-20cm to evaluate soil pH, and the contents of Al, Ca, Mg, P, K, C and N. The PV treatment showed higher values for soil Ca, Mg, K, C and soil organic matter (SOM), indicating high cycling rates and biological activity. Soil stability was found to be high in all treatments, since C:N ratio was lower than 12:1. Organic matter fragmentation showed a higher amount of fulvic acids (FA), humic acids (HA) and humins (HU) in the PV treatment, for the three soil layers. The plantation on the hillside (PM) had the highest values of (FA+HA)/HU ratio, suggesting a lower stability condition. The extraction-fumigation method was used to estimate C and N contents in the soil microbial biomass (MB), as well as the soil respiration rate, only for the 0-2.5cm layer. There was no difference in C-MB (Cmicr.) and N-BM (Nmicr.) values among the treatments, but both metabolic quotient (qCO2) and Cmicr.:Nmicr. ratio was higher for the PM, which may suggest a less stable site than those on the flooding areas. The structure of edaphic fauna indicated higher fauna density in the flooding area Forest (FV), but PV showed an average group richness similar to those of Forest sites, despite PM groups richness was similar to those of pastures. In order to evaluate forest regeneration mechanisms, soil seed bank and seed rain were monitored. The PV treatment showed more seedlings (381) and more species (25) emerging from the soil samples, and the hillside plantation (PM) trapped the highest amount of seeds, mostly from Gochnatia polymorpha, a typical pioneer tree species. Results suggest that restoration techniques to be adopted must be specific for either the sloping sites or the flooding areas. The establishment of Forest connectivity may enhance the participation of tree species in seeds and fruits dispersal events.