Influence of soil fertility on the physiognomy of the African savanna tree Colophospermum mopane

This study investigated the influence of soil fertility on the physiognomy of Colophospermum mopane, one of the dominant tree or shrub species in savannas of central and southern Africa. The study was conducted in Gonarezhou National Park (GNP) in the south-east of Zimbabwe. Mopane stands at the study site were divided into three physiognomic forms or mopane 'types': short mopane (SM, 1-2 m in height); medium mopane (MM, 8-12 m) and tall mopane (TM, > 15 m). In each mopane type, soil samples were collected up to a depth of 15 cm to investigate the level of soil nutrient concentrations. SM stands were associated with low phosphorus and high levels of calcium and sodium relative to MM and TM. The low levels of phosphorus in SM relative to other mopane types suggest that phosphorus may be an important nutrient limiting growth in dwarf mopane. Alternatively, plant nutrients may be limiting because of interaction with factors such as the high soil sodicity present in the dwarf mopane habitats that may affect nutrient uptake or plant nutrient demand.