The Biodiversity Observatory is situated in the central part of the Knersvlakte, the southern Namaqualand which forms the western Succulent Karoo Biome. The Knersvlakte is characterised by a gently undulated landscape, is underlain by shales, phyllites and limestones of the Nama Group and is streaked by numerous quartz veins. The quartz veins are weathering more slowly than the surrounding softer bedrock like shale or phyllites and the resulting quartz gravel is covering large parts of the area, forming distinct quartz field islands. More than 65 seed plant species are endemics to quartz fields in the Knersvlakte. They represent a unique flora and vegetation.The long-term annual rainfall average of the closest weather station of the South African Weather Bureau in Vanrhynsdorp is 150 mm with maxima from May to September. However, own rainfall data for Ratelgat Observatory show that the average rainfall amount at Ratelgat is about 20 % lower than in Vanrhynsdorp. Fog from the coastal Benguela Current and dew play an important role for additional water supply for flora and fauna. Mean annual temperature is about 19 °C, frost events are rare and light.Most parts of the Observatory are characterised by quartz fields and shale outcrops. The Observatory is dominated by leaf succulent dwarf shrubs and very rich in plant species among which leaf succulent Aizoaceae and Asteraceae species are most species rich.Since 1999, the farm belongs to the Griqua Development Trust. The Griqua Community, which is based in Vredendal, uses the farm for cultural, educational and economic (i.e. small stock farming and ecotourism) purposes. After having been used for moderate commercial small stock farming for several decades, the farm is now subject to a low grazing intensity.The main focus of research at this site are the phytodiversity patterns which are driven by small scale soil patterns as well the effects of climate change on biodiversity which are also investigated by experimental approaches (passive warming by open top chambers). Major research activities are presently conducted by botanists (seed plants and biological soil crusts) and soil scientist. |
Daily averages up to this date available
