Dinâmica da comunidade arbórea de um fragmento florestal urbano dominado por espécies exóticas

Abstract

The dominance of exotic species is a major feature of secondary forests and socalled Novel Ecosystems. Although studies assess the patterns of these communities in tropical rainforests, little is known about these patterns in tropical forests. The species Pinus elliotti have high invasive potential in neotropical forests, and are found in secondary forests of the Zona da Mata at Minas Gerais State. The aim of this study was to analyze the dynamics (5 years) of the tree community of an urban secondary forest dominated by P. elliotti. Floristic and structural changes were analyzed from comparisons between two inventories in permanent plots (15 plots of 20 x 20 m randomly allocated in the forest) in the years 2011 and 2016. All tree individuals with DBH ≥ 5 cm were sampled, measured, and calculated the structural, phytosociological and species diversity parameters. Dynamic rates (recruitment, mortality, gain and loss of basal area) were calculated, being sampled 943 individuals, 168 recruits and 151 deaths. The community showed a strong specific dominance, with a high concentration of importance values (VI) distributed in the first seven species (Pinus elliottii; Miconia artemisiana; Mimosa artemisiana; Myrcia splendens; Pleroma mutabilis; Piptadenia gonoacantha; Miconia urophyla), which accounted for 52.2% of the total VI. Between the two measurements, the mortality rate of 3.50% .year-1 was slightly lower than that of recruitment of 3.85% .year-1. The rate of gain in basal area of 5.98% .year-1 exceeded that of loss of 2.90% .year-1. Despite the presence of invasive species and accelerated dynamics, there were no major structural changes in the fragment, believing that the community is able to remain floristically stable in the short and medium term, due to the resistance of the main populations.