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. Realized niche spaces are generated at various plant densities for species across a wide range of environmental conditions in South Africa. Resultant response surfaces suggest different putative functional types. Determination of traits in common within such types provides testable hypotheses for application to other species from the available species pool. The approach provides a potentially powerful tool for grouping and regrouping species according to different functional frameworks at regional level. This includes deriving types that are sensitive to global climatic change. Preliminary results are given for an initial set of indigenous woody plant species, i.e. Burkea africana Hook., Euclea undulata Thunb. and Schotia afra (L.) Thunb. showing that the effects of projected climate change on species depend on their population density. 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 of global change.