Carbon stock in an urban area afforested 50 years ago

Climate change is a growing concern, driven by the accelerated emission of carbon dioxide resulting from human activities. Recent studies have indicated that urban trees contribute to mitigating these changes. Given that legal frameworks supporting the implementation of this landscape feature are already in place, this study aimed to evaluate the carbon stock and identify the species that contribute the most to it within the oldest area of the Main Campus of the State University of Maringá, in northern Paraná, which was established 50 years ago. The study area comprises 11.5 hectares. Based on the floristic survey of trees and large palms, measurement of the diameter at breast height (1.30 m), total height, and wood density values obtained from specialized literature, local biomass and carbon stock were estimated using three allometric models available in the literature. The area contains 998 specimens belonging to 27 botanical families, 68 genera, and 83 species, 49.40% of which are native to the northern region of Paraná. The estimated carbon stock was 402.76 Mg C or 35.25 Mg C ha-1, a value considered significant when compared to other Brazilian urban areas. Fabaceae accounted for 65.72% of the total carbon stock, followed by Bignoniaceae (10.23%) and Arecaceae (9.85%). The species that contributed the most to carbon storage were Cenostigma pluviosum, Tipuana tipu, Delonix regia, and Dypsis lutescens (exotic); and Handroanthus heptaphyllus, Cordia trichotoma, and Holocalyx balansae (native), in terms of both specimen count and DBH. Only D. regia exhibited high wood density, while the others presented intermediate values. These findings underscore the importance of urban forestry as a carbon sink and reinforce its contribution to the provision of ecosystem services to society.