This study arose out ofthe old question of what actually determines vegetation structure and distributions. Is climate the overriding control, as one would suppose from reading the more geographically oriented literature? Or is climate only incidental, as suggested by more site and/ or taxon-oriented writers? The question might be phrased more realistically: How much does climate control vegetation processes, structures, and distributions? It seemed to me, as an ambitious doctoral student, that one way to attempt an answer might be to try to predict world vegetation from climate alone and then compare the predicted results with actual vegetation patterns. If climatic data were sufficient to reproduce the world's actual vegetation patterns, then one could conclude that climate is the main control. This book represents an expanded, second-generation version of that original thesis. It presents world-scale vegetation and ecoclimatic models and a methodology for applying such models to predict vegetation and for evaluating model results.
This approach also provides a means of geographical simulation of vegetation patterns and changes, which represent necessary data inputs in other fields such as atmospheric chemistry and biogeochemical cycling. It has been fairly well accepted that climatic and other environmental conditions are associated with the evolution of particular aspects of plant form (convergent evolution). The particular configurations of plant size, photosynthetic surface area and structure (e. g. sclerophylly, stomatal 'resistance'), and their seasonal variations represent what one can recognize fairly readily as distinct growth forms.
1. Introduction.- 2. Modeling ecological structure and function.- A. World vegetation models in general.- B. The current model.- C. Model structure and technical considerations.- 3. Ecological classification of world vegetation.- A. Vegetation description and vegetation data.- B. Ecophysiognomic characters of terrestrial vegetation.- C. Life forms of world terrestrial vegetation.- 4. Modeling the effective environment.- A. Climate data.- B. Selection of ecoclimatic variables.- C. The ecoclimatic variables and their significance.- 5. The ecological model: life-form limitation, cover and dominance.- A. Ecological data.- B. The environmental-limitation model.- C. The cover model.- D. The dominance model.- E. Proximity to environmental limits.- F. Interpreting vegetation formations.- 6. Model results.- A. Model output and applicability.- B. Generating and mapping world results.- C. Overview of world ecoclimates.- D. Life-form prediction frequency.- E. Predicted plant-form distributions.- F. Predicting world vegetation types.- G. Physiognomic diversity of vegetation.- H. General observations and problems.- 7. Evaluation of model results.- A. Site comparison of predicted and actual vegetation.- B. Vegetation and climate at unusual sites.- C. Vegetation sensitivity to climatic variation.- 8. Conclusions and next steps.- Appendices.- Appendix A. Description of the plant types.- Appendix B. Predicted vegetation at selected representative and well-known sites.- Appendix C. Predicted vegetation at the validation sites.- Appendix D. Actual vegetation at the validation sites.- Appendix E. The macroclimatic data-base.- Appendix F. The processing and mapping programs.- References.