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.