Simulation of canopy CO2 flux for a rubber plantation: the effect of the regular spacing of trees

Rubber plantations are rapidly expanding to not only optimal but also sub-optimal environments throughout mainland Southeast Asia region. What the environmental problems are induced by this vast land-use change and how the changed environment influences the rubber plantation productivities have been concerned. For this investigation, describing the biosphere-atmosphere exchange in the rubber plantations with understanding the environmental process is essential, and soil-vegetation-atmosphere transfer (SVAT) model coupling ecophysiological and biogeochemical principles at the leaf scale with detailed turbulent transport mechanics is the promising tool. A regular spacing of trees is a marked characteristic of rubber plantations and generate their peculiar canopy structure. The SVAT models, however, have paid less attention to how to account for such a canopy properties in the model and how to evaluate it in the field observation. In this study, we developed the SVAT model applicable to the rubber plantation and an evaluation method for its canopy structure, and examine how the peculiar canopy structure affect the canopy CO2 exchange by comparing model results with measurements conducted at a rubber plantation in Cambodia. The findings suggest that it is impossible to reproduce the observed rubber plantation flux without accounting for the intensive canopy clumping.