Health Status of Street Trees Along the Urban–Rural Gradient in the Garden City of Bengaluru, India

Urban forestry involves the strategic management of trees within urban landscapes to enhance ecosystem services, improve biodiversity, mitigate climate change, and reduce the urban heat island effect. In addition to their ecological value, urban trees contribute aesthetic, economic, and functional benefits—such as increasing property value and attracting tourism. This study aimed to assess the health of urban trees exposed to various anthropogenic pressures in Bengaluru city. A total of 48 one-hectare plots were established—23 in the northern and 25 in the southern transects of the city. Trees with a diameter at breast height (DBH) of ≥10 cm were selected for analysis. Based on the extent of tree cover and built-up area, plots were categorized into urban, transition, and rural zones. Common tree species from each zone were evaluated for their Air Pollution Tolerance Index (APTI) in both transects. Fresh leaf samples were collected and analyzed for four key biochemical parameters: leaf pH, ascorbic acid content, relative water content, and total chlorophyll content. The results revealed that some species exhibited greater tolerance to air pollution. In the northern transect, Mangifera indica , Psidium guajava , Ficus glomerata , and Pongamia pinnata demonstrated higher APTI values, indicating greater tolerance. In the southern transect, Mangifera indica , Ficus tinctoria , Commiphora caudata , and Alangium salviifolium were identified as more tolerant. This study underscores the adaptive capacity of specific tree species to varying pollution levels and offers valuable insights for urban greening initiatives, species selection, and sustainable city planning aimed at enhancing ecological resilience and air quality in metropolitan areas.