Effects of anthropogenic fires on some soil properties and the implications of fire frequency for the Guinea savanna ecological zone, Ghana

Abstract

Fire is an important factor influencing the structure and function of tropical savannas. In spite of the extensive studies conducted on the effects of fire on soils in savannas, there are relatively few studies focusing on the Sudano-Guinean savanna of West Africa which experiences recurring fires in the dry season. The fires are anthropogenic and mainly caused by hunters and farmers to flush out animals, remove debris from crop fields and to improve soil fertility. We investigated how bush fires influence some soil properties in four land use types in six districts in the Guinea savanna of Ghana. Data on fire counts were obtained from the CSIR Meraka Institute, South Africa and fire densities calculated for each district. Soils were sampled in burned and unburned woodlands and crop fields and analysed for pH, available P, Total N, SOC, exchangeable Ca and Mg, CEC, EC and texture. The fire densities varied amongst the selected districts. Of the six districts, the East Gonja district recorded the highest fire density (1.0 fire km −2 ). Tamale recorded the lowest density (0.3 fires km −2 ). Total N, OC, pH and exchangeable Ca differed significantly across the different land use types. A principal component analysis showed a stronger association and more positive gradient in woodlands than in crop fields. Total N and OC, showed a positive association. High fire frequencies were recorded in districts with high grass fuel loads and abundant wildlife. Fire aided the mineralisation of TN, SOC and exchangeable Ca as burned fields had higher mean values of these nutrients than unburned fields. Further studies are needed to fully understand the importance of fire regimes on soils in the Guinea savanna. Traditional ecological knowledge on the use of fire could be harnessed to reduce indiscriminate vegetation burning in the region.