THE RELATIONSHIP IN THE DISTRIBUTION OF TROPICAL PEAT SWAMP FORESTS AND FRESH WATER LAKES OF MAPUTALAND, SOUTH AFRICA

摘要

Maputaland is the largest peatland eco-region in South Africa and it contains 60 % of the known peat resources in South Africa. The associated tropical peat swamp forests of Maputaland forms about a third of the number of peatlands in Maputaland and are one of the most unique and rare wetland types in southern African. Fifty-five percent of the peatlands in Maputaland occur in association with the coastal lakes. It was found to be significant that 60% of the lakes were linked to swamp forests. Most of the lakes along Maputaland result from damming up and diversion of river systems by belts of sand dunes. The original rivers flowed from west to east, i.e. approximately at right angles to the present coastline. Most had estuaries, controlled partly by coastal sand bars, partly by a rise in sea level. This situation has subsequently been modified by coast-parallel dune bars. These dunes originate from beach deflation. This dune topography results in elongated interdune valleys, usually orientated parallel to the present coastline. Periods of transgression has resulted in the the drowning of the coast-parallel dune valleys allowing quiet low energy, low-sedimentation regimes to prevail. It is in this topography of drowned dune landscape in which swamp forest developed in association with the lakes, especially where some drainage into the lakes are evident. Various land use practices impacts negatively on the peatlands in Maputalan, amongst other cultivation.