Floristic Diversity and Composition of Urban Forest Trees in Kano Metropolis, Nigeria

Abstract

Urban forests play a vital role in maintaining ecological balance, enhancing environmental quality, and supporting biodiversity, particularly in rapidly urbanizing regions. However, limited information on floristic diversity and species composition in cities like Kano Metropolis hinders effective urban forest management and biodiversity conservation planning. This study evaluates the species composition and diversity of urban trees in Kano Metropolis, Northern Nigeria, with emphasis on their ecological structure and distribution. A systematic vegetation survey was conducted across 15 representative urban sites using quadrats and transect sampling techniques. All trees with a diameter at breast height (DBH) ≥10 cm were identified to species level, and their abundance, frequency, and dominance were recorded. Diversity indices, including Shannon–Wiener, Simpson, and Evenness indices, were computed to evaluate floristic diversity, while species composition patterns were analyzed using importance value indices (IVI). A field inventory of all trees with diameter at breast height (DBH) ≥ 10 cm was conducted across selected urban locations. Tree species were identified and measured, and diversity was assessed using Shannon–Wiener and Simpson indices. A total of 1,144 individual trees belonging to 15 families were recorded, comprising both native and exotic species. Shannon–Wiener diversity values ranged from 1.07–2.36, indicating moderate species diversity across sites, while species evenness was generally low, reflecting dominance by a few cultivated or exotic species. The results revealed variations in species abundance and distribution, with Azadirachta indica being the most dominant species, while Ficus platyphylla, Balanites aegyptiaca, and Acacia seyal were among the least represented. Diversity indices indicated moderate species diversity within the study area. The study highlights the heterogeneity of urban forest structure in Kano Metropolis and emphasizes the need for strategic planning and conservation of indigenous species to enhance urban biodiversity and resilience. Findings provide a baseline for urban forestry planning and management, contributing to sustainable urban green space development in rapidly expanding Nigerian cities.