Abstract

This comprehensive study investigated the patterns of distribution, diversity, growth attributes and carbon sequestration by trees in a district of Karachi. The Defence Housing Authority (DHA) was chosen as one of the few developed urban green spaces. As a result, 15,055 trees were estimated to have been planted along roads by the roadside, graveyards and parks. The ecological assessment with reference to relative density, frequency, abundance, dominance and Importance Value Index (IVI) were made. Data suggested that Conocarpus sp., Lignum vitae and Azadirachta indica were the major plants in DHA Karachi, Pakistan. These species have shown an impressive adaptability to the harsh environmental conditions of the DHA area, thus being able to assist well in the growth of the urban ecosystem. Different values were noted for the Shannon Diversity Index (H) along varying locations indicating a species richness level in roadside areas. The following values were recorded: 1.60 for roadsides, 1.59 for graveyards, and 1.60 for parks. The Simpson Diversity Index was higher in graveyards (0.74) signifying a more homogeneous species distribution. Growth variations of each species were tested against incremental diameter, height, DBH, and basal area. The projecting species with growth correlating to roadways was Conocarpus sp. where, across sites, heights differed between a range of 250 to 1,500 cm, and average basal area was 7,140.13 cm². The study also revealed that urban agro-forests have a potential in carbon sequestration in which the mean carbon stock of all areas was 4.74 tons. The highest amount of carbon stock, that is, 5.61 tons on average, is found along roadsides followed by parks (5.09 tons) and graveyards (3.53 tons). Conocarpus sp. along roadsides recorded the highest IVI values (51.01), and L. vitae recorded the highest IVI of 55.51 in graveyards. These findings highlight the ecological roles of urban green spaces in contributing to environmental sustainability in DHA Karachi, Pakistan.