B. Papp szerk.: Studia Botanica Hungarica 29. 1998 (Budapest, 1999)

Iqbal, M. Z., Sherwani, A. K.; Shafiq, M.: Vegetation characteristics and trace metals (Cu, Zn and Pb) in soils along the super highways near Karachi, Pakistan

Table 2. Range and mean values for the most dominant species along the Super Highways. Dominant species NSD IVI Cu (pg

; Zn (pi sg1

) Pb (pi Range Mean Range Mean Range Mean Range Mean Senna holosericea 10 32.11-76.60 55.07 118-315 190 8-225 94 5-43 21 Prosopis juliflora 07 35.57-81.99 53.48 23-330 134 5-268 112 13-48 31 Abutilon indicum 01 35.24 120 105 23 Fagonia indica ill 34.89 135 100 25 Blepharis sindica 01 27.52 305 35 15 Abbreviations: IVI = Importance Value Index, NSD = Number of stands dominant Pb were the highest. Salsola baryosma stand also showed higher values for Zn and Pb, but for Cu, the level was low. On the other hand, the stand in which Indigofera cordifolia was the least dominant showed low concentration of Zn and Pb but for Cu, the concentration was much higher. One stand where, Haloxylon recurvum showed 15.89% importance value, the concentrations of Cu, Zn and Pb was low. The effects of metals on vegetation are varied and could involve in the extinction of some species. Extinction of some rare species would result in the increase of the prevalence of relatively stable species, such as Prosopis juliflora and Senna holosericea. Table 3. Mean values for the rare species along the Super Highways. Nos of stands IVI Concentration (pg g ') for rare species Cu Zn Pb Suaeda fmucosa 1 3.72 330 268 48 Fagonia indica 2 6.58 308 125 26 Indigofera cordifolia 1 2.26 305 35 15 Rhyncosia minima 1 2.69 200 5 18 Aerva javanica 3 10.61 191 86 14 Zizyphus nummularia 2 5.44 137 27 21 Calotropis procera 3 3.48 133 78 18 Salsola baryosma 1 6.17 1 10 200 45 Salvia santolinifolia 4 4.27 77 127 32 Haloxylon recurvum 1 15.89 30 36 13 Abbreviation: IVI = Importance Value Index