Diversity, structure, and carbon sequestration potential of the woody flora of urban squares in the Brazilian semiarid region

The population and economic growth in cities significantly contribute to greenhouse gas (GHG) emissions, making them potential protagonists in mitigating these emissions. However, there is a lack of research on carbon potential in these areas in the Brazilian northeastern interior. In this context, this study analyzed urban squares as elements for climate change mitigation and global warming, highlighting the importance of these spaces for local biodiversity and sustainability in cities, providing a basis for future research related to the theme in the region. Six squares were selected in three conurbated municipalities (Barbalha, Crato and Juazeiro do Norte, Ceará State) in the Brazilian semiarid zone, encompassing all individuals with a diameter at breast height (DBH) ≥ 5cm. Carbon quantification occurred through direct means (analysis of leaf, fine branch, and stem samples) and indirect means, using DBH to calculate biomass and carbon. A total of 554 individuals from 39 species and 18 families were recorded, with Fabaceae, Arecaceae, and Bignoniaceae being prominent. The Shannon index (H') ranged from 0.85 to 2.45, the Simpson index (C') from 0.35 to 0.88, and the Pielou evenness index (J') from 0.38 to 0.86. Mean carbon contents varied from 47.5% to 57.2% in different tree compartments, with Schinus terebinthifolia Raddi standing out for high organic matter values (96.2%) and carbon content (55.9%) in leaves. Praça da Sé (Crato) presented the highest concentrations of plant biomass and stored carbon and a significant amount of sequestered carbon (709.24t). Over one year, an increase of 0.29 t/ha−1 in total biomass carbon and 1.04 t/ha−1 of sequestered CO2 was observed. The results highlight the fundamental importance of urban square flora, identifying them as crucial allies in carbon capture and storage and in reducing GHG emissions.