(1) The surface soils beneath trees of five species native to Neotropical savannas have been analysed for exchangeable calcium, magnesium, potassium and sodium, available phosphorus and total nitrogen. (2) All trees showed preferential enrichment of the soil about them, in some cases to levels approaching or exceeding those found in nearby rain-forest soil. (3) Enrichment has been achieved without deep rooting by the trees, indicating that the capture of precipitation inputs has been the major mineral-nutrient source. (4) Neither increased cation-exchange-capacity nor increased moisture-retention-capacity in the soil around the trees can satisfactorily explain their more efficient capture of precipitation inputs. The gradual accumulation of mineral nutrients by persistent genets, and the incorporation of these into an enlarged plant-litter-soil nutrient cycle appears to offer the best explanation of the mechanism responsible. (5) The creation of such enriched microsites may provide nuci for the invasion of infetile savannas by rain-forest trees that appears to have recurred sporadically during Quaternary climatic oscillations