Abstract
It was hypothesized that different plant species vary in response to the oil and gas pollution in terms of composition and distribution pattern as well. Some of the plants have more tolerance to heavy metals accumulation in polluted ecosystem than others. Quantitative ecological techniques using quadrat methods were applied in a stratified random design around the Nashpa Oil and Gas Plant District Karak to check specific plant indicators that can grow, survive and show more tolerance against Oil and Gas pollution. In four directions from Gas Plant 10 stations were established at a distance of one Km from each other. Different size of quadrats i.e. 1x1 m(2), 5x5 m(2) and 10x10 m(2) for herbs, shrubs and trees were used respectively. The phyto-sociological attributes of each species (density, relative density, frequency, relative frequency, cover, relative cover and Importance Values Index) were measured at each station. Furthermore, Calotropis procera was investigated for Pb, Cr and Cu heavy metals accumulation usIng atomic absorption spectrophotometer. All the collected data matrices were analyzed via Cluster analysis and Canonical Correspondence Analysis (CCA) using PC-ORD version 5 and CANOCO software. A total of 113 plant species were recorded belonging to 44 families from the Nashpa Oil and Gas Plant. Dominant and rare plants of heavy, moderate and less-polluted regions were identified and assessed. Result showed that Calotropis procera has more tolerant against pollution. It was concluded that the Oil & Gas Plant has significant effect on surrounding habitat plants for heavy metal accumulation. Higher concentration of K, pH and organic matter has significant effects (p <= 0.002) on plant species diversity and its distribution pattern. Result of Pb and Cu accumulation in C. procera showed heavy metals accumulation increased from less polluted sites towards moderate and more polluted regions gradually. It is recommended that further study needed to examine other dominant species as well.