Estrutura e dinâmica da comunidade de plântulas em três formações vegetais no Norte de Minas Gerais

Abstract

This study aimed to test two hypothesis 1) Hypothesis of similar composition, which predicts that the composition of the regeneration plant is similar to the composition of tree stratum in the same vegetation type. 2) environmental stress hypothesis, which predicts that vegetation with a lower canopy covery have higher seedling growth, reduced herbivory and increased survival. The floristic composition of the regenerating stratum was described and 45 plots, 15 in cerrado, dry forest and riparian forest in the Area of Environmental Protection Bacia do Rio Pandeiros north of the state of Minas Gerais. Between February (2008) and April (2009) data were collected on height and leaf number of seedlings, herbivory rate and indicated the mortality among a sample and another. We measured the canopy opening in the dry and rainy season through hemispherical photographs. 587 seedlings were monitored. The seedlings richness varied among environments. Growth differed between the months of sampling and was higher in the rainy season. The canopy cover varied between environments and between the months of sampling, reducing in the dry season. The seedling number of leaves differed between months and between environments. The abundance and density of seedlings did not vary between environments, height and seedling growth did not differ between the three environments. There was no relationship between canopy openness and seedling growth. The cerrado had lower canopy cover, seedlings with more leaves, less leaf area and lower mortality. The dry forest showed the lowest seedling richness and greater canopy cover. The riparian forest showed higher seedling mortality and lower mean time to death. The seedling community and the arboreal community varied between environments and each other in the same environment. The first hypothesis was not confirmed, there was a high turnover of species between the two stratum in the study sites, indicating that there may be variation in species composition among the groups. This variation can be affected by local conditions and the degree of human disturbance. The second hypothesis was confirmed, and the environment more subject to environmental stress, with less vegetation cover, had higher seedlings survived, probably due to the herbivory. Herbivory was the determining factor in seedlings mortality. The higher seedlings mortality in riparian forest is also linked with greater fragility of this environment. Thus, previous studies of dynamics, structure and succession, should be performed prior to initiating recovery programs