Floristic and structural changes in a neotropical urban novel forest over 13 years

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The ecological importance of non-native species is the main characteristic of novel ecosystems. Pinus elliottii species is highly invasive in tropical forests and is commonly found in secondary forests in Brazil. We investigated the floristic and structural changes in an urban novel forest dominated by P. elliottii over a 13-year period (2011–2023). Based on the knowledge about novel forests ecology, we hypothesised that the community will remain stable without significant changes in tree structure and composition over the study period. We studied a small urban forest fragment (2 ha) in Juiz de Fora municipality, south-eastern Brazil. We measured all trees with diameter at breast height (DBH) ≥ 50 mm in a sample of 15 permanent plots (20 × 20 m) in 2011, 2016 and 2023, and calculated the changes in phytosociological and species diversity parameters for each period. As hypothesised, we did not observe significant changes in community structure and composition. Species richness increased from 63 to 80 over the period, but without changes in the phytosociological hierarchy. The non-native species P. elliottii remained as the most important species (importance value, IV) in 2011 (15.1%), 2016 (14.9%) and 2023 (14.2%). The following 12 hyperdominant species in the phytosociological hierarchy, which accounted for more than 70% of IV over the periods, remained dominant with no or small changes in the species hierarchy. The species diversity indices (H’) and multivariate analysis (ANOSIM) did not show significant differences over the periods. We concluded that the community is likely to remain with no significant changes in the coming decades due of the self-regenerating structure of the main populations. To the best of our knowledge, this is the first dynamic analysis of an urban novel forest in the neotropics, providing valuable insights for a better understanding of its ecology and functioning.