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Biodiversity of an interface zone of a nutrient‐deficient lake (Nabugabo) in Uganda: macrophytes
Author(s) -
Kateyo Eliezer M.
Publication year - 2007
Publication title -
african journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.499
H-Index - 54
eISSN - 1365-2028
pISSN - 0141-6707
DOI - 10.1111/j.1365-2028.2006.00490.x
Subject(s) - swamp , scirpus , macrophyte , peat , sphagnum , cyperus , bay , wetland , geology , ecology , geography , botany , oceanography , biology
Lake Nabugabo was a big bay of Lake Victoria before being separated from the latter by a sand bar about 4000 years ago. Whereas conductivity of Lake Victoria is 100 μ Scm −1 that of Nabugabo has been less than 30 μ cm −2 since the Cambridge Scientific Expedition, 1962. Dissolved calcium carbonate is below detectable levels although nitrate and phosphate are not significantly different from those of Lake Victoria. However, the total cations and anions are five times more in Lake Victoria than Nabugabo. Along the eastern, southern and south‐western margins of the lake is an emergent swamp composed of different types of plants. In most places, Miscanthidium violaceum forms a floating platform of matted roots and rhizomes which border the open lake; it is associated with Sphagnum , a type of moss which normally grows in acidic and low‐temperature conditions at very high altitudes and latitudes. Because of the presence of this moss, the Nabugabo swamps are sometimes called ‘ Sphagnum swamps’. Vossia cuspidata (hippo grass) is yet another emergent swamp plant in Lake Nabugabo, occurring in a number of isolated narrow mats stretching from a few metres to 0.5 km or longer along the edge of the emergent swamp. These floating mats are firmly anchored to the Micanthidium platform. Cyperus latifolia is another emergent‐floating plant in Lake Nabugabo firmly anchored on to the Miscanthidium platform. Cyperus latifolia and V. cuspidata tend to grow side by side but in completely sheltered bays the former plant grows alone. Cyperus papyrus L. occurs in very few patches within the emergent swamp. In the interface zone along the emergent swamp, there are a number of euhydrophyte plant species: Nymphaea caerulea is the most dominant and widespread euhydrophyte species except in the eastern tip of the lake where it is replaced by Nymphaea lotus ; interspersed among these lilies is Ceratophyllum demersum in certain bays which could either be water inlets or out‐flows; Utricularia and Nymphoides indica are associated with monospecific stand of N. caerulea in the south‐western end of the zone.