Abstract

The research was undertaken to investigate diversity, important value indices (IVI) and carbon storage of trees located in various parks of Joseph Sarwuan Tarka University Makurdi, Nigeria between 2019 and 2020. Species diversity was determined using Shanon index while tree biomass was determined using the allometric model (AGB = exp (−2.977 + Ln (ρD2H)) = 0.0509 × ρD2H). Total sequestered carbon in trees was determined as 50% of tree biomass. Results revealed a total of 298 trees, belonging to 30 species and 16 families in the study area, with Daniellia oliveri having the highest number of plants (76) and percentage occurrence (26%). Plant height and DBH varied among the species with Daniellia oliveri recording the highest values (19.77 m and 240.80 cm) respectively. The species Height and, Diameter at Breast Height (DBH) was grouped with class >11 m to 15 m (13) and class >51 cm to 100 cm (12) dominating the parks. The species diversity (Shannon Index) in the individual parks varied, with Food Science and Technology, and Nubess parks having the highest (2.138) and lowest (0.652) diversity indices, respectively. Frequency, basal area, relative frequency (RF), relative density (RDe), cover value index (CVI) and IVI varied with species. Daniella oliveri had the highest frequency (76), Delonix regia had the highest basal area (4.55), RF (143.33), RDe (14.43) and RDo (9.90). Family value index (FVI), was highest in the family Fabaceae (684.39). Above ground biomass (AGB) ranged from (24021.48) in Delonix regia to 238.47 in Psidium guajava, while below-ground biomass (BGB) ranged from 4804.30 in D. regia to 47.69 in P. guajava. Total Plant biomass (AGB + BGB) varied between Delonix regia (28825.78) and P. guajava (286.17), respectively. Carbon storage varied with species and parks, with Veterinary Park having the highest total sequestered carbon (105.65 tonnes) and sequestered carbon dioxide equivalent (387.74 tonnes). D. regia had the highest total sequestered carbon (14412.89 tonnes/tree) followed by Daniella oliveri (1148.24 tonnes/tree), with B. ferruginea (201.16) and P. guajava (143.08) having the least total sequestered carbon. D. regia had the highest sequestered CO2 equivalent (SCO2 E) (52.90) followed by D. oliveri (42.09) and P. africana (34.60), while P. guajava, B. ferruginea and Terminalia mentalis had the least SCO2 E (0.53, 0.74 and 1.2), respectively. Moreover, Plant height correlated moderately with AGB (R = 0.597; p = 0.000) and DBH (R = 0.529; p = 0.003), with a positive relationship between AGB and DBH (R = 0.859; p = 0.000), suggesting that AGB increases with increasing DBH and plant height. Extensive assessment of urban parks and garden for carbon storage is hereby advocated.

Keywords: Species diversity; Importance value indices; Carbon sequestration; Total biomass