Estrutura, diversidade e regeneração arbórea de uma floresta atlântica secundária submetida à supressão do sub-bosque

Abstract

This study aimed to analyze and describe the composition and diversity of woody species in different forest strata component of a stretch of lowland forest belonging to the Botanical Garden of the Universidade Federal de Juiz de Fora, Juiz de Fora, MG, Brazil. The total area of forest stretch that suffered slash past (~3 ha), was defined as the sampling universe. 25 random plots of 20 x 20 m for the analysis of the tree stratum were allocated a total sample size of 1.0 ha and their subplots of 5 x 5 m for the analysis of regenerating stratum. In the tree component were sampled 651 ind.ha-1, over 53 species belonging to 31 botanical families, with a predominance of Fabaceae (08 species) and Myrtaceae (04). There was a community with strong species dominance, with a large concentration of Importance Values (VI) in the first three species (Piptadenia gonoacantha (Mart.) JF Macbr, Piptocarpha macropoda (DC.) Baker and Xylopia sericea A.St.Hil) which amounted 43.74% of total VI. In regenerating stratum 901 individuals were sampled (equivalent to 14,416 ind.ha-1), distributed in 29 families and 62 species. Fabaceae (07 species), Sapindaceae (05) and Asteraceae (05) are the richest families. The species that stood out according to VI were Piptocarpha macropoda (DC.) Baker (35.61%) and Anadenanthera colubrina (Vell). Brenan (6.87%). Reflecting the strong ecological dominance, the value of the index of species diversity (Shannon H '= 2.92 nats.ind-1 for the canopy layer and H' = 2.72 nats.ind-1 for regenerating stratum) was low compared with secondary forests of similar vegetation type in the region. The diameter distribution analysis revealed distinct division of the forest into two strata: the upper stratum, formed by large trees with large canopy; and a lower stratum, formed by regenerating individuals, small trees, in competition to colonize the environment. The analysis of ecological groups showed a predominance of species from early successional stages (pioneer and early secondary) with most species having dispersal zoochoric type. The Canonical Correspondence Analysis (CCA) was able to detect four blocks of species, demonstrating that the relationship between species and environment are sensitive to environmental variables in an interactive way and not isolated.