Effects of anthropogenic fires on 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 are mainly caused by hunters and farmers to flush out animals, remove debris from crop fields and to improve soil fertility. We investigated how the bush fires influence 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 fires densities calculated for each district. Soils were sampled in burned and unburned woodlands and crop fields and analysed for pH, available P, Total N, OC, Ca, 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 (0.82 fires km−2). Tamale recorded the lowest density (0.32 fires km−2). Total N, OC, pH and 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, whereas silt showed a negative association to sand and clay. High fire frequencies were recorded in districts with high grass fuel loads and abundant wildlife. Fire aided the mineralisation of nutrients as burned fields had higher mean values of 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. Keywords: Bush burning, Land use, Soil properties, Fire counts, Guinea savanna