2.1. Sampling of Soil
Khewra Salt Mine is the world second largest salt mine, located near Pind Dadan Khan Tehsil of Jhelum District, Punjab, Pakistan. Geographically, it is located about 32° 38´ North latitude, 73°10´ East longitude and an elevation of 313-360 meters above the sea level about 200 km from Islamabad. It has Na+ and Cl- dominating ions and the pH is near neutral to slightly alkaline. The sampling area was selected according to land use and vegetation cover. Vegetation of this area is classified as sub-tropical dry evergreen forest. Rhizospheric soil samples were collected by gently removing the plants and obtaining the soil attached to the roots. For non-rhizospheric saline soil samples, the upper 8-10 cm of mineral soil was collected. At each site, soil samples of approximately 500 g each from four different locations were collected in black sterile polythene bags. These samples were stored at 4 ℃ for further analysis.