An approach for modelling the effects of changes in hydrological environmental variables on tropical primary forest vegetation

• Developed a methodology to study the effects of the changes in hydrological environment on forest vegetation.
• Methodology involves coupling a vegetation model with environmental variables.
• A vegetation model from the field of biological research was adopted for the purpose.
• Linking the environmental effects with vegetation model was demonstrated in two forests.
• Application of the methodology provided practically useful results for Nee Soon.

SummaryTheories that explain the dynamics of ecological communities are still in the developing stage. Yet, practical problems arise where the effects of man-made alterations in the hydrological environment on ecological communities need to be known. The processes involved in such cases are usually poorly understood and long term data and information are also limited. This study introduced a vegetation model taken from the field of ecology for the purpose of addressing such issues specifically to link the environmental variables with vegetation and to study the effects of changes in the hydrological environment on vegetation. The study was also motivated by the recent findings on species – habitat associations and species distributions on hydrological gradients. The investigation was specifically applied to tropical primary forests. The vegetation model chosen is more general and yet simple in formulation making to a top-down analysis of a system possible thereby reducing the data requirement and computational complexity. The study modified the model to suit the tropical forest modelling and gave analytical solutions to the steady states. The study demonstrated how the general information or data available can be incorporated in the model to produce useful qualitatively appreciable results, without requiring detailed understanding of the processes or comprehensive data records. The model was demonstrated on two tropical primary forests; Sinharaja forest dynamics plot (FDP) in Sri Lanka and Nee Soon freshwater swamp forest in Singapore where the effect of change in hydrological environment on vegetation was studied. The model was shown to be able to produce useful qualitative results.