Concepts for the aggregation of tropical tree species into functional types and the application to Sabah's lowland rain forests

For analysing field data as well as for modelling purposes it is useful to classify tree species into a few functional types. In this paper a new aggr egation of tree species of the dipterocarp rain forests in Sabah (Borneo), Malaysia, is developed. The aggregation is based on the two criteria succes sional status and potential maximum height. Three classes of successional s tatus (early, mid and late successional species) and five classes of potent ial maximum heights (less than or equal to 5 m, 5-15, 15-25, 25-36, > 36 m) lead to a combination of 15 functional types. The criteria of the develope d classification are chosen to suit for applications with process-based mod els, such as FORMIX3 and FORMIND, which are based on photosynthesis product ion as the main process determining tree growth. The concept is universal a nd can easily be applied to other areas. With this new method of grouping a more realistic parametrization of process-based rain forest growth models seems to be possible.