A study of the ecology of Acacia mellifera, A. seyal, and Balanites aegyptiaca in relation to land clearing.
Land clearing for irrigated agriculture in the Sudan clay plains is urgently needed because the Roseires Dam is to be completed in 1967. Two different vegetation communities are present in the areas to be developed: (a) Acacia mellifera bushland and associated short grassland in a drier, more northerly zone, and (b) A. seyal/Balanites aegyptiaca tall-grass woodland in the wetter southerly zone. Different problems arise in the clearing of the three species; fire tolerance, depth and type of rooting, and suitability for girdling, chemical poisoning, mechanical raking, uprooting and chain-felling, are different in each case. Timed raking trials in four areas of (a) of different densities provided data concerning times of operation. From aerial photos a crown-density scale was developed that enabled the density of the vegetation to be assessed and so made it possible to estimate the total tractor hours needed to clear the bushland in the project area. A second trial in (b) tested chain-felling, tree-pushing and raking equipment, and established that it would cost three times as much to clear land by raking chain-felled timber into rows for burning, as to clear by burning felled timber in situ. Using data from these trials, a second density scale was designed for estimates of the total tractor hours required in each phase of clearing in (b) of the project area. The fewer the seasons available for land clearing in (b), the less fire and other processes of decay can help in reducing costs. This does not necessarily apply to (a). KEYWORDS: Acacia mellifera \ Acacia seyal \ Balanites aegyptiaca \ Land clearing \ Logging \ woody weeds \ control