Biophysical drivers of tropical tree diversity and carbon stocks across an urban gradient in Mexico

Abstract

Urban and peri-urban green spaces are shaped by a complex interaction between anthropogenic management and underlying biophysical heterogeneity, which gives them particular community attributes (structure and diversity) and soil functions. Consequently, vegetation-based assessments alone often fail to capture the multidimensionality of these socioecological systems. Here, we examined the extent to which biophysical constraints, such as precipitation, topography, soil properties, and the structure of urban forests, differentially affect terrestrial carbon (C) stocks within tropical urban and peri-urban green spaces. We tested hypotheses regarding the importance of diversity in native and non-native plant species, as well as the effect of soil variation among sites. We compared woody species richness (⁰D), dominance (²D), composition, structure, and tree aboveground biomass (AGB), as well as soil organic carbon, across a mosaic of green spaces in the mid-sized city of Morelia, Michoacán state, Mexico. Using principal components analysis (PCA) and analysis of similarities (ANOSIM), we identified significant correlations between biophysical heterogeneity and community-level patterns. Elevated carbon density in urban areas is related to the presence of larger individuals of non-native species. Instead, native species shaped the peri-urban carbon stock through a greater number of individuals. Soil organic carbon stocks showed no significant differences between urban and peri-urban sites. This study advances the understanding of urban ecosystems, highlighting the need for integrative indicators that account for tropical environmental quality. Our findings contribute to a framework for assessing the performance of green infrastructure, with implications for climate adaptation, biodiversity conservation, and urban landscapes.