The effect of fire history on soil nutrients and soil organic carbon in a semi-arid savanna woodland, central Namibia

Fire is an integral part of savanna ecosystems that has shaped these systems since the Miocene. Substantial uncertainty about fire effects in semi-arid ecosystems exists. Fire may affect ecosystem productivity directly through nutrient volatilisation, increased mineralisation and altering organic matter quantity, and indirectly through altering vegetation structure. We explored the effects of fire history and vegetation patch types (tree canopy vs inter-canopy) on soil nutrients and soil organic carbon (SOC) in a semi-arid ecosystem. We collected soil samples along transects in four treatments with different fire histories (1 to 24 years since the last burn). In the statistical analyses, tree canopy and inter-canopy samples along transects were differentiated. Fire showed an inconsistent effect on soil nutrients and SOC. There was a short-term negative influence on total nitrogen, whereas phosphorus, potassium and magnesium increased in the 1-year treatment. Sodium consistently decreased with increasing t...