Assessment of Leaf Chlorophyll Concentration of Tree Species Used for Greenbelt Development in Kazaure Metropolis, Jigawa State Nigeria

Air pollution in semi-arid Kazaure, Nigeria, is made worse by rapid urbanization, endangering both ecological stability and public health. Evidence-based urban forestry is hampered by data gaps, so choosing resilient tree species for greenbelts requires empirical evidence of pollution tolerance in Sudan Savanna ecosystems. Ten dominant tree species were studied across four sites along a pollution gradient (high-traffic, commercial, residential, and low-pollution control sites) to determine the concentration of leaf chlorophyll, a crucial bio-indicator of plant stress. Chlorophyll levels significantly decreased along pollution gradients, according to spectrophotometric analysis of 120 leaf samples. High-traffic Kanti had lower concentrations (2.33 ± 0.66 mg/g) than the control site (3.25 ± 0.62 mg/g; Tukey’s HSD, p < 0.001). The highest chlorophyll levels were consistently maintained by Azadirachta indica (3.68 ± 0.42 mg/g) and Gmelina arborea (3.49 ± 0.41 mg/g), indicating their superior pollution tolerance, while Eucalyptus camaldulensis (1.83 ± 0.45 mg/g; Tukey’s HSD, p < 0.001) showed the lowest concentrations, indicating that it is a sensitive receptor. Species rankings were consistent across sites (no significant species × site interaction, p= 0.275), demonstrating intrinsic physiological tolerance. Therefore, in order to improve the resilience of urban ecosystems, we strongly recommend that municipal authorities incorporate chlorophyll thresholds (>3.2 mg/g) into species selection protocols, prioritize A. indica and G. arborea in greenbelt designs, and limit E. camaldulensis to low-pollution zones.