Regeneração natural e banco de sementes do solo sob efeito de borda em um fragmento de Floresta Ombrófila Densa das Terras Baixas

Abstract

The natural regeneration stratum and the soil seed bank are important mechanisms of forest regeneration. Understading how these mechanisms are being influened by environmental changes at the forest edge, can be used as the process of refining and conditioning of process of succession. This study aimed to verify the influence of the effect on natural regeneration and the soil seed bank in a lowland Forest Ombrophilous Dense fragment in the northern state of Espírito Santo. For the natural regeneration and soil seed bank sampling, 36 plots of 5 m x 10 m were allocated, divided into four plots, as demarcation lines on two edges and without the interior of the Córrego Grande Biological Reserve, located in the municipality of Conceição da Barra, ES. All individuals with a minimum height of 50 cm and a diameter at breat height (DBH) of less than 2,5 cm were considered as belonging to the natural regeneration stratum. The soil samples were collected in the first 8 cm of the soil, being taken to a nursery where the germinated seeds were evaluated. Measurements of moisture, density, canopy opening and physical-chemical analysis of the soil were performed. Species composition and series data similarity was made between the border gradient and the interior between the edges and the interior of the Bray-Curtis index-based fragment using the Unweighted Media Pooling (UPGMA) method. The data of the reporting tests were carried out in Redundancy Analysis (RDA), to verify the environmental and spatial influence on the vegetation of the regenerating stratum. The analysis of the cluster allowed to verify if the roadway is more distinct than the recovery area, as far as natural regeneration for the seed bank, for a natural regeneration is important for the first 10 years for the seed bank was sustainable up to 30 m. The main environmental variables that contribute to explain the distribution of the species were soil moisture, canopy opening and resistance to soil penetration, in relation to space, 8 spatial variables were generated by Moran's Eigenvector Maps, with the first three axes explaining 45, 16% of the variation in the floristic composition of the regenerating stratum. The floristics of natural regeneration and the seed bank allow them to be the two main mechanisms of resilience. This study verified that the edge effect occurs mainly on the composition of the species, and among the studied areas it was observed to be more effective in the first meters of the border with road for natural regeneration (0-10 m) and seed bank of the soil (0-30 m).