Soils and vegetation in a forest-savana transition zone in Southern Belize

A sequence of associated soils and forest types over Tertiary mudstones in the coastal plain of southern Belize is described. The associations range from high stature, diverse. mesophyllic forest over shallow, well drained and fertile loams and clays in gently dissected, rolling terrain through intermediate soils and forest types, to scrubby, sclerophyllous woodland over deep, poorly drained and infertile clays on undissected and almost flat interfluves. The associations are interpreted as resulting from concurrent and interactive pedological and ecological evolutionary developments. The soils are being progressively weathered and leached, and clay translocation contributes to a deterioration in their drainage. The changes in the soils are parallelled by reductions in stature, diversity and apparent vigour of the forest. These contribute to the deterioration in soil drainage by reducing water uptake. The scrubby vegetation is also more susceptible to fire, which appears to reinforce and accelerate the trend towards soil impoverishment and savanna-like vegetation. The evolution of sclerophyllous woodland on potentially fertile soil parent materials like mudstone is thought to be protracted and to require long periods of geomorphic stability. On more siliceous parent materials the process appears to be more rapid, as shown elsewhere in Belize