Impacts of early and repeated fires on nutrients in the wooded savannahs of Burkina Faso

Bush fires, considered to be a major ecological disturbance in savannah ecosystems, are also rife in large parts of Burkina Faso. The objectives of this research were to understand nutrient dynamics by early and repeated fires. The study was conducted on a factorial set-up installed on two (02) sites, namely the Dindéresso classified forest located in the west (where the first fires started in 2010) and the Tiogo classified forest located in the centre-west of the country (since 1992, for the first fires). Measurements were taken before and after the fire and ashes were also evaluated. The results showed that the epigeous biomass was approximately the same on both sites (around 4 t.ha-1). With regard to biomass dynamics and ash levels, analysis of the results showed that the control plots had the highest herbaceous biomass levels (320 and 350 m.g-2), while ash levels were much higher at the Tiogo site (65.3 g.m-2) than at Dindéresso (12.19 g.m-2). Assessment of the nutrient pool showed that before the fire, the carbon present in the biomass was high at both sites (168±19 g m-2 at the Dindéresso site and 178±0.6 g m-2 at the Tiogo site). After the fire, nutrient losses at the different sites were observed for C (82% at Dindéresso compared with only 45% at Tiogo), N (91% at Dindéresso compared with only 69% at Tiogo) and P (79% at Dindéresso compared with only 63% at Tiogo). In general, nutrient losses are higher in Dindéresso than in Tiogo, with an estimated difference of more than 45% for C, 24% for N and 20% for P.