Avaliação da funcionalidade do solo em sistemas florestais enriquecidos com leguminosas

Abstract

The study was conducted in an area of abandoned pasture, originally under the cover of the Atlantic Forest, to evaluate the process of succession and restoration of degraded areas. The area was located in Valença municipality, State of Rio de Janeiro Brazil. In 2001 it was conducted a planting of nitrogen fixing leguminous trees in different proportions: 0% (0L), 25% (25L), 50% (50L), and 75% (75L). Sampling for evaluation of soil biota occurred in two periods, one at the end of the dry season (August/2007) and another in the rainy season (February/2008). Other samples were taken in a secondary forest; and in two pasture areas, one without usage (Pasture B), with spontaneous vegetation of grasses and some shrubs, and another regularly grazed by animals with dominant vegetation of Brachiaria (Pasture A). To evaluate the biomass production by the plant species introduced, the input and storage of litter in the revegetated areas and the forest area were measured. For the litter input, in general, it was observed that the revegetated areas did not differ from the forest. Although the treatment 25L presented litter quantities greater than that in all other fractions evaluated. As for the accumulation of material on the soil it was higher in the forest, and most of the material consisted of tree branches, which may justify the increased time required for residue decomposition. In general, the reforestation process increased the soil fauna diversity. However, this change was more significant when compared the sampling seasons. The fauna group Formicidae had more prominence, showing high quantities in all treatments, for the two sampling periods. In the rainy season, there was a considerable increase in the amount of invertebrates in the litter layer of the treatments 0L, 25L, 50L, 75L, and in the forest. In the dry period this behavior was observed in the 0-10 cm layer. The results of the indexes richness and density of spores of AMFs were higher in the rainy season, and the highest values were verified in the pasture areas, which is the earliest stage of succession. The genus Acaulospora and Glomus were the most abundant in all treatments, in both sampling periods, and the specie Glomus macrocarpum was identified in all samples.