Dinâmica de fragmentos florestais urbanos com diferentes históricos de uso de solo na Zona da Mata Mineira

Abstract

Urban forests play a crucial role in conserving natural resources and are formed as a consequence of anthropogenic disturbances. These urban fragments with different land use histories can result in different diversity, structure, richness and composition, even in forests of the same age. In tropical regions, “novel ecosystems” are distinguished by a high dominance of non-native and invasive tree species. As a hypothesis: (i) Urban forests will be dynamic and tend to be homogeneous in the long term, and recruitment and mortality rates will be affected by different land uses; (ii) the forest classificated how “Novel ecosystems” will be dynamic, but will maintain the population stability of the dominant species, however the presence of these species will not change significantly in the species composition and structural dynamics throughout the studied period. Four small urban forest fragments were studied (two “novel ecosystems” and two secondary urban forests) with different land uses in the urban landscape of the Municipality of Juiz de Fora, in the Atlantic Forest domain in Southeast Brazil. We measured all trees with diameter at breast height (DBH) ≥ 5 cm in a sample of 40 permanent plots (20 x 20 m) between 7 and 11 years old and calculated changes in rates of recruitment dynamics, individual mortality, loss and gain in basal area. We calculated diversity, composition and species richness for each period. We recorded significant changes in the composition, richness and diversity of communities. We found high mortality rates in the four fragments (>2%.year-1) and high recruitment rates (>3%.year-1). “Novel ecosystems” showed the persistence of dominant species in communities and urban forests showed high dynamics of pioneer and secondary species. The species diversity indices (H') (p < 0.01), and the multivariate similarity analysis (ANOSIM) (H' t-test, p > 0.05) showed significant differences between the communities, but did not present significant differences over time. The analysis indicates that communities tend to remain stable in the coming decades due to the stability of the main populations. The results showed accelerated dynamics and that communities with a history of severe disturbances have difficulty continuing to advance ecological dynamics. To our knowledge, this is the first comparative analysis of the dynamics of “novel ecosystems” with secondary forests in a Neotropical urban landscape, providing valuable information for a better understanding of their functioning for future management and conservation efforts. Finally, taking global climate change into account, this study is necessary to verify anthropogenic impacts on various aspects of plant communities, an extremely important fact due to concerns about the future of urban forests, essential for maintaining ecosystem services.