Ecological surveys of certain plant communities around urban areas of Karachi

A phytosociological study was conducted as an initial assessment of the vegetation on different sites to determine the community structure and how the communities were related based on their species composition and edaphic characteristics. The communities were distinct types ranging from halophytes to xerophytes with disturbed in nature. Plant communities based on first leading dominant species (Prosopis, Avicennia, Gynandropis, Salvadora, Ipomea, Halopyrum, Limonium, Abutilon and Calotropis) were explored in the study area. Out of thirty-nine plant species, Prosopis juliflora attained the highest total importance value index (I.V.I.) followed by Avicennia marina, Suaeda fruticosa and Gynandropsis gynandra. Nine species attained first leading position. Thirteen species attained second dominant position. However, twelve species attained third dominant position in all stands. P. juliflora was the only species that was found six times as a first dominant, three times as second and one time as a third dominates species. None of the other species was in a position to get first, second and third position as a leading dominant in all stands. The communities were of heterogeneous type, with low species diversity and ranged from 1.36 to 4.54. Most of the plant communities showed less than 50% CMI values. However, Prosopis in association with Pasplidium and Cenchrus community showed highest CMI value (70.00). The soils of the study areas were sandy loam, loamy sand, loamy silt, sandy and silty. The soils are alkaline in nature. An appreciable amount of calcium carbonate (13-26%) with moderate percentage of maximum water holding capacity (19-41%) and high soil EC (593 s/cmμ) were recorded. It was also observed that certain edaphic and human activity, discharge of pollutants with out any pretreatment was found responsible for variation in the nature, structure and composition of vegetation. The plant growth and their continuity was in danger in many disturb areas, especially in some coastal areas where salinity and the incident of Tasman spirit oil spillage was occurred just few months before the survey carried out. Construction of flyover, expansion of the roads and cut down of the natural vegetation producing additional losses to flora of the region.