The urban forest of Mexico City: structure and diversity across land use and boroughs

The variation of structural and compositional characteristics of urban forests is influenced by the urban landscape heterogeneity and several biotic, abiotic, and human factors. Urban forests provide numerous ecosystem and social benefits key to the wellbeing of citizens and to enhance environmental conditions in cities. However, the quantity and quality of these services are determined by the urban forest structure, composition, and spatial variation. There has been little research on the heterogeneity in the urban forest structure and composition across the entire urbanized area of Mexico City, one of the largest and most populated cities in North America. This study explores urban forest composition, diversity and structure across the entire urbanized area and within six urban land uses and the 16 boroughs of Mexico City using tree data from 500 fixed-area plots of 400 m2 distributed across the city. Alfa and beta diversity analysis, and analysis of variance revealed differences in tree diversity and structure within land uses and boroughs. Green areas had higher basal area but less species richness than the residential and the commercial-residential land-use types. The lower values of basal area and canopy cover were found in the boroughs in the east part of the city, and the highest species richness was in boroughs in the south. Land use types and boroughs are ecologically heterogeneous units (β = 0.5, β = 0.6, respectively) and urban forest planning needs to consider their specific conditions. The higher proportion of non-native species found in this study highlights the need to diversify prioritizing native species.