Vegetation communities of five Magela Creek billabongs, Alligator Rivers Region, Northern Territory
Technical Memorandum 46
Finlayson CM, Thompson K, von Oertzen I and Cowie ID
About the report
The major vegetation communities in three backflow (Coonjimba, Djalkmara and Georgetown) and two floodplain (Jabiluka and Leichhardt) billabongs are described. The descriptions are aided by the presentation of vegetation maps prepared during the 1987-88 Wet season. All macrophytic plant species known to occur in each billabong are listed and categorised into growth-strategy and growth-form types. The plant biomass (assessed qualitatively) in the backflow billabongs was dominated by the fringing perennial Melaleuca spp trees and the geophytic perennial Eleocharis spp sedges. The floodplain billabongs are deeper, have steeper banks than the backflow billabongs and have a narrower woodland fringe. A feature of the floodplain billabongs over the study period was the presence of floating mats of grass, sedge and herb species, that also contained the introduced floating fern Salvinia molesta. Forty-five plant species were recorded in Coonjimba Billabong, forty-three in Djalkmara, Georgetown thirty-six, Jabiluka forty-four and Leichhardt forty. The vegetation in the backflow billabongs has changed since buffalo numbers were reduced, with sedges becoming more widespread. This in turn appears to have led to an increase in silt deposition in these billabongs. At times, mats of Salvinia molesta have completely covered the surface of the floodplain billabongs.