Resistance to and uptake of heavy metals by Vetiveria zizanioides and Paspalum notatum from lead/zinc mine tailings ECOLOGICAL EFFECTS OF PLANTING VETIVER GRASS IN CITRUS GROVES ON SLOPING RED SOIL FIELDS Effects of Grasses of Vetiveria and Pennisetum on Trophic Groups of Soil Nematodes Effects of straw mulching and Vetiver grass hedgerows on the size distribution of the soil water stable aggregates and aggregate-associated organic carbon in red soil