Abstract

Rationale: The proliferation of old vehicles adds pollution to sub-Saharan cities. The pollution extent remains unknown, due to lacking the will or equipment to measure or monitor it. Observing plants exposed to pollution could provide missing information. Goal: This study aims to explore the morphological behavior of trees exposed to varied road traffic intensity. Methods: We investigated the impact of vehicle air pollutants on selected roadside tree species in Douala, Cameroon. Physiological and health parameters of trees were measured and their GPS coordinates mapped. The systematic method was used to select 341 trees for data collection. Depends of the traffic intensity, three classification of the level of pollution were considered and grouped as polluted and non-polluted sites. Trees located along high traffic roads (Case) were compared to those with low/absence traffic (Control) using factorial analysis, ANOVA, Fisher, and chi-square tests. Results and recommendations: Depends on the species of trees, the reaction to pollution were visible through the presence of lichens, the proportion of exudates, flowering, fruit production, foliage, aspect of bark and the presence of bark cracks. Tree height and crown volume were associated with the reduction of the level of pollution. The observable morphology changes toward pollution level of the three species: Polyalthia longifolia, Ficus benjamina and Terminalia mantaly made them potential bio-indicator of air pollution.