REALIZED NICHE SPACES AND FUNCTIONAL TYPES - A FRAMEWORK FOR PREDICTION OF COMPOSITIONAL CHANGE

High resolution and comprehensive quantitative plant and environmental data bases permit an iterative screening approach to provide greater freedom from a priori classification of plant functional types. Realiz ed niche spaces are generated at various plant densities for species a cross a wide range of environmental conditions in South Africa. Result ant response surfaces suggest different putative functional types. Det ermination of traits in common within such types provides testable hyp otheses for application to other species from the available species po ol. The approach provides a potentially powerful tool for grouping and regrouping species according to different functional frameworks at re gional level. This includes deriving types that are sensitive to globa l climatic change. Preliminary results are given for an initial set of indigenous woody plant species, i.e. Burkea africana Hook., Euclea un dulata Thunb. and Schotia afra (L.) Thunb. showing that the effects of projected climate change on species depend on their population densit y. Predicted compositional changes at the landscape level confirm the need to allow independence of migrating functional types, rather than modelling the dynamics of existing composite biomes under conditions o f global change.