Soil seed bank dynamics and fertility on a seasonal wetland invaded by Lantana camara in a savanna ecosystem

Abstract

Knowledge of seed bank status and dynamics is crucial for effective management of desirable and undesirable plant species in natural ecosystems. We studied the soil seed bank dynamics and soil nutrient concentrations in Lantana camara invaded and uninvaded patches at New Gada wetland in Harare, Zimbabwe. Soils were tested for pH, ammonium (NH4+), nitrate (NO3−), phosphorus (P), calcium (Ca), magnesium (Mg), sodium (Na) and potassium (K). We also assessed the soil seed bank density to a depth of 15cm over varied altitudinal zones. Soil nutrient concentrations increased by a factor of 2.5 for Na, 3.1 for NH4+, 4.8 for Mg up to 8.5 for Ca with L. camara invasion. In contrast, L. camara invaded patches had a lower concentration of NO3− and P than uninvaded patches. Seed density significantly declined with both soil depth and slope with high seed density in the upper surface soil of the lower slopes of the wetland. The elevated soil nutrient concentrations along with a high soil seed bank density suggest that the wetland may still be susceptible to continued invasion by L. camara particularly on the lower slopes of the wetland. Thus, management and eradication efforts should focus on the areas that receive or trap the eroded soil seed bank.