Vegetation composition and assessment of phytotoxicity in a paper mill dumpsite

The solid waste dumpsites of pulp and paper industries are prone to be turned into degraded lands due to the loss of vegetation cover. Such sites often possess drought, salinity and pH stresses as well as heavy metal contamination. Restoration of top soil by creating vegetation cover has proved to be the most sustainable approach to check land degradation. Therefore, to find some stress-tolerant species capable of creating vegetation cover in paper mill dumpsites, a vegetation composition study was conducted in a paper mill dumpsite. A total of seven plant species viz., Calotropis gigantea (L.) Dryand., Chromolaena odorata (L.) R.M. King & H. Rob, Mikania scandens (L.) Willd., R. communis L., Rotheca serrata (L.) Steane & Mabb., Senna sophera (L.) Roxb. and Solanum myriacanthum Dunal were found. To correlate the existence of these plants with stress condition of soil, the level of phytotoxicity in the dumpsite was assessed by studying seed germination status, proline accumulation, leaf relative water content (RWC), leaf pH, total chlorophyll content and ascorbic acid level of Ricinus communis as bioassay indices. The significantly lower percentage of seed germination in dumpsite soil, compared to control, revealed the phytotoxic nature of the soil of the dumpsite. The significantly higher level of proline, RWC, total chlorophyll and ascorbic acid in plant leaves from dumpsites than from the control soils indicated considerable stress in the dumpsite. Soil physicochemical and nutrient status analyses substantiated with the bioassay results. Despite apparent phytotoxicity, the presence of certain plant species in the dumpsite indicated their inherent stress tolerance capability to be prospected.