Banco de sementes, chuva de sementes e o uso de técnicas de nucleação na restauração ecológica de uma clareira dominada por Melinis minutiflora P. Beauv

Abstract

Melinis minutiflora (Poaceae) is an African species that has been a big problem in natural environments in Brazil. It is an invader exotic species that is very aggressive and its control is difficult. In Juiz de Fora, MG, it dominates an anthropic gap area in the Biological Reserve Santa Cândida. The objectives of this work were to evaluate the natural regeneration by characterization of the seed bank and seed rain of this gap and evaluate the potential of different restoration ecology methods based on nucleation. The seed bank was quantified in 12 samples under trees (SP) and 12 ones in opened places, under grass (SC), with dimensions of 25x25x3cm. The seeds quantification was made through germination, monitored during 4 months in green house. Inside of the gap were weeded 10 transects of 2,5x15m, where were installed 10 parcels with the following treatments: control (without weeding), weeding (autochthonous regeneration), seed rain monitoring (traps of 1m²) and the planting, all monitored during 12 months. The soil transposition samples were collected under around vegetation of the gap in 10 parcels of 1,0x0,5x0,1m allocated randomly, these were spread in 10 parcels of 1,0x1,0m. Schinus therebinthifolius, Trema micrantha and Virola bicuhyba plants were planted in 3 different treatments with 5 repetitions compounding parcels with only one plant (P1); parcels with 3 plants of the same species (P2) and parcels with 3 plants with one of each species (P3). The seed bank showed a density of 12.646,67 ± 9.428,06 seeds/m2 that 93% of the plants were of Poaceae family. There was not significant difference in seed bank density of SP and SC samples. SP presented less diversity (H’ = 0,22) than SC (H’ = 0,39). In both conditions there was herbaceous species predominance. In the seed rain were sampled 140.701 seeds with anemochorous and herbaceous predominance, being that 93% of the seeds belong to M. minutiflora. In the autochthonous regeneration was sampled, in the last monitored month, a density of 57,2 ± 52,4 plants/m², were identified 39 species with herbaceous predominance, being that the most abundant, after M. minutiflora, were Borreria alata, Sida glaziovii and Crotalaria pterocaula. In the soil transposition, the last monitored month density was 46,7 ± 41,8 plants/m², being recognized 66 species with herbaceous predominance and a few representative tree species like Apuleia leiocarpa, Cecropia sp, Croton urucurana, and Trema micrantha. S. therebinthifolius and T. micrantha plants showed a good height and diameter growth that had not a statistical difference between P1, P2 and P3. The mortality rate was null to S. therebinthifolius, of 20% to T. micrantha, especially in the P2 treatment, and of 88% to V. bicuhyba. All treatments, except planting, presented the herbaceous species domain and the strong presence of M. minutiflora, showing that the molasses grass management is necessary to accelerate the gap regeneration.