Avenue Tree Species Diversity, Stand Volume and Natural Regeneration Status Along the Faculty of Agriculture Road to NUGA Gate, Kenya

Abstract

Forest trees species growing in and around forest estates required information to ensure sustainable management especially avenue trees in our tertiary educational institutions in Nigeria, which provided many ecosystem services such as species conservation, preservation of habitat for plants and animals, reservoirs for biodiversity, habitat to diverse animal species, sources of timber, medicinal plants, recreation activities, carbon sequestration, watershed protection and also form the livelihood for many different human settlements. This study assessed avenue tree species diversity, stand volume, and regeneration status of avenue trees planted along Faculty of Agriculture Road, from East-West Seed Site Roundabout to NUGA Gate, Ahmadu Bello University Main Campus, Zaria. A total enumeration approach was used, covering all avenue trees along a 18,750 m² stretch on both sides of the road. Tree height was measured using a Haga altimeter, DBH was also measured using a diameter tape, and the number of wildlings counted and recorded (≤ 30 cm height) within 2 m of each mature tree. Biodiversity indices were analyzed using the Shannon–Wiener and Pielou’s Evenness formulas. Results revealed 14 species from 8 families, dominated by Meliaceae. The mean tree volume ranges from a minimum of 2.60m³ for the Malvaceae family to a maximum of 56.99m³ in the Meliaceae family. Khaya senegalensis and Azadirachta indica of Meliaceae had the highest mean volume (56.99m³), while the lowest was recorded in Adansonia digitata (2.60m³) of the Malvaceae family. The family of Meliaceae was regarded as the dominant family in the avenue with 48 tree species. Shannon-Weiner diversity index and species equitability index according to Pielou are 1.80 and 0.68, respectively, obtained for the study. This shows that the avenue tree species is biologically diverse. The regeneration potentials of most species are zero, owing to anthropogenic pressure on the mother trees, which would have produced the wildlings within the avenue, apart from a few species like Albizia lebbeck, with moderately high regeneration potential, and Khaya senegalensis, with low regeneration potential. It is recommended that fast-growing, disease-tolerant, and shade avenue trees should be raised and planted by the University authorities to fill the gaps to obtain maximum productivity and a conducive learning environment for students and to improve the aesthetic view of the entire campus landscape. Also, frequent surveys and inventories of trees on campus should be conducted by relevant stakeholders to assess their abundance, distribution, and density, as well as structural and physical changes necessary for sustainable management practices.