Bush-control studies in the drier areas of Kenya. 5. Effects of controlled burning and grazing management on Tarchonanthus /Acacia thicket.
Abstract
Treatments were appropriate to traditional cattle husbandry and consisted of two 4-year rotations involving burning, grazing by goats and preliminary slashing, and ran for 5 years. Burning soon opened the thicket canopy and increased the contribution of grass. The first 2 fires killed over half the original population of Dichrostachys cinerea and appreciable numbers of Acacia trees, but populations of woody plants tended to increase through seedling establishment and no significant kill of the dominant species Tarchonanthus camphoratus or Acacia brevispica was obtained. The 3rd burn killed a few A. brevispica and much reduced the vigour of T. camphoratus. At the end of the experiment, areas given 3 burns yielded 3000 Ib grass DM/ ac compared with 940 Ib/ac on unburnt areas. All perennial grass species, including Themeda triandra and Panicum maximum) increased in frequency. Including goats in the grazing regime helped to check the increase in woody plant population (but increased that of D. cinerea) and led to significantly higher fire temperatures. Feeding habits of the goats used varied greatly according to area of their origin, and browsing was more effective in slashed than unslashed areas. Slashing also facilitated even burning. It was considered that continuing the burning regime would bring out a change to wooded grassland or could be used to reduce the vigour of thicket preparatory to using arboricides. Effective burning depended on low air humidity.-R.B.