Effects of deforestation on grass biomass and soil nutrient status in miombo woodland, Zambia

There is a growing concern in central and southern Africa about the negative effects of deforestation caused by shifting cultivation and charcoal production. In the absence of long-term studies that document and assess impacts of tropical deforestation, it is difficult to evaluate the relevance of current policy interventions that address the negative effects of deforestation. To contribute to the knowledge about impacts of tropical deforestation, the effects of clearing Brachystegia–Julbernardia (miombo) woodland on grass biomass and soil nutrient status were assessed at four sites over a 10-years period, from 1991 to 2000 in central Zambia. Woodland clearing increased grass biomass by 20–50% and although its impacts on topsoil organic matter and available phosphorus were apparent, these were not statistically significant. Site and year had the most significant effects on soil nutrient stocks, regardless of the woodland clearing treatment. Generally, fire did not affect grass production but reduced topsoil organic matter and nitrogen at three of the study sites. Deforestation followed by cultivation significantly reduced soil organic matter in the study area. Based on these results, it is recommended that local cultivation practices should incorporate measures that minimize loss of soil organic matter in order to sustain long-term soil fertility.