Brenha ou estágio sucessional de floresta? análise comparativa da composição florística e estrutura da brenha e floresta de Licuáti e áreas adjacentes

Abstract

Biodiversity is essential for the maintenance of ecosystems and the provision of ecological services, however, it has been impacted by human action. Human action is primarily responsible for the conversion of natural habitats, which affects the structure and dynamics of plant communities, impacting patterns of ecological succession. In southern Mozambique, the Licuáti thicket stands out as a unique ecosystem in the Maputaland Center of Endemism, despite little known about its successional status. This study aims to investigate whether the thicket represents an intermediate successional stage of the forest or a distinct vegetation type of Licuáti and adjacent areas. Indeed, 50 x 20 m sample plots were used. In each plot, all plant individuals with a diameter at breast height (DBH) equal to or greater than 5 cm were identified, counted, and measured, measured at 1.30 m above the ground with a measuring tape. Ecological metrics such as the Importance Value Index (IVI), Shannon-Weaver diversity, and Pielou's Evenness Index were calculated, along with multivariate analyses (NMDS, ANOSIM, and SIMPER) to assess similarities/dissimilarities in floristic composition between thicket and forest. Species diameter distribution and physiognomy (height-to-diameter relationship) of trees in the thicket and forest were the vegetation structure variables analyzed. Granularity models for thicket and forest were used to distinguish the successional stage of the two habitats. The results indicate that forest and thicket are similar in terms of floristic composition. The forest presents greater species diversity and evenness compared to the thicket. Species diameter distribution patterns in both habitats varied between inverted-J, unimodal, and multimodal, demonstrating different population dynamics. Tree physiognomy showed a moderate correlation in the thicket, suggesting balanced growth between height and diameter. In the forest, this relationship was weaker, reflecting a more heterogeneous and complex structure. The graining models indicated that the thicket presents a coarse-grain pattern, with dissimilar upper and lower strata, while the forest exhibits fine-grain pattern, with similar upper and lower strata. The coarse-grain pattern in the Licuáti thicket indicates that it is a distinct vegetation type from the forest. Human action may be influencing the dynamics of the thicket, making it essential to assess its ecological resilience, the influence of environmental factors, and develop effective conservation strategies.