Determinants of vegetation type patch dieback in a semi-arid area, Tutume Sub-District, Botswana

Patch dieback of Colophospermum mopane (Kirk ex Benth.) Kirk ex J. Leonard, which was attributed to drought, soil surface condition and soil chemistry has been reported in South Africa. In Botswana, dieback of C. mopane and other species were noticed in 2012 in the North east part of the country (North West of Francistown). The causes of the noticed dieback were not known. The objective of this study was to determine the status and causes of that dieback. The study was based on field survey to determine species with dieback, the percentage number of dieback affected individual plants of each species and the areas affected. A questionnaire was also administered to get views from people living in the study area on what they thought caused the dieback. Rainfall and temperature data were obtained from Department of Meteorological Services. It was found that it was not only C. mopane that was affected but even other species such as Dichrostachys cinerea, Combretum hereroense and Terminalia prunioides. It appears that low temperatures combined with soils type are the major causes of the dieback. Dieback was mostly on tree individuals on heavy clay soils than those on loamy soils. Key words: Francistown, plant dieback, vertisols, loamy soils, temperature, rainfall.