STRUCTURE AND COMPOSITION OF URBAN GREENERIES IN DHAKA SOUTH CITY CORPORATION

Abstract

Plants are the important feature of urban ecosystems and provide different environmental and socio-economic benefits. Different habitats like roadsides, parks, gardens and playgrounds in Dhaka South City Corporation were surveyed for the assessment of structure and composition of urban plants. Stratified random sampling method was used in this study. A total of 347 plant species (Tree=144, Shrub=77 & Herb=126) belonging to 113 families were recorded. Among trees and shrubs, Swietenia macrophylla, Polyalthia longifolia, Cocos nucifera, Combrectum indicum and Tabernaemonlana divaricata were recorded as the most dominant plant species. In case of tree and shrub, Fabaceae family (species % = 16.62) and in case of herbs, Poaceae family (species% = 13.49) were found dominant. Distribution of plants is highly uneven as only six species showed >40% frequency and eight species had greater than 25% frequency. Among all the study areas, highest tree and shrub population were represented by parks (44%) followed by gardens (26%), roadsides (26%) and playgrounds (4%), respectively. Majority of herb species was represented by parks (74.6%), followed by gardens (46.83%), roadsides (18.25%) and playgrounds (4.76%), respectively. Most of the tree populations were found in between 6-9 m height class whereas majority of shrub population were found in between 1-3 m height class. In case of DBH, maximum numbers of tree and shrub population were found in between 10-15 cm DBH class. Highest IVI value was found for Polyalthia longifolia (IVI= 103.39%) followed by Swietenia macrophylla (IVI= 85.61%) Samanea saman (IVI= 83.44%) and Combrectum indicum (IVI= 25.29%). Average density, mean DBH, mean basal area were 1785.62 (tree/ha), 458.59 (cm/ha), 182.79 (m²/ha), respectively. This study reveals that species composition in Dhaka South City Corporation is significant whereas the structural attributes of plant population represent quite young and still developing vegetation. Findings of this research will help to manage and plan for future green infrastructure which will maintain ecosystem function, therefore, providing long term benefits for the city dwellers.