SOIL CHARACTERISTICS OF REHABILITATING AND UNMINED COASTAL DUNES AT RICHARDS BAY, KWAZULU-NATAL, SOUTH-AFRICA

The postmining rehabilitation of coastal sand dunes north of Richards Bay (28 degrees 43'S, 32 degrees 12'E), South Africa, is resulting in the development of a series of known-aged stands of vegetation dominat ed by Acacia karroo (sweet thorn). Other broad-leaved species are esta blishing themselves in rehabilitating areas more than 12 years of age. Soils from rehabilitating stands 3-5, 9-12, 13-15, and 16-18 years of age, from two disturbed, unmined stands 30 and 58 years of age, and f rom a mature unmined stand were examined to assess age-related trends in selected soil properties. Individually, these stands represent a se ries of different developmental stages of a coastal dune successional sere. Soil organic material, percentage organic carbon and concentrati ons of sodium, potassium, magnesium, calcium, and nitrogen increased w ith an increase in habitat regeneration age. Concentrations of most of these elements were lower than those recorded on the 58-year-old unmi ned and mature unmined stands. Multivariate analyses suggest, however, that the similarity of these values for rehabilitating stands to thos e for the unmined stands increased with an increase in regeneration ag e. The growth response of Raphanus sativus (radish) plants, based on m ass attained under experimental growing conditions in soil collected f rom these stands, suggests an increase in soil fertility with an incre ase in regeneration age.