PRF/J: Turbulent Exchange at Vegetated Surfaces: Canopy Geometry and Gas-Exchange

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Relations between forest canopy geometry, local physiological characteristics, and whole-canopy gas-exchange will be examined. The goal is understand links between individual- plant and whole-canopy physiological processes. Focus will be on effects of vertical position on plant physiological processes, to provide input values for a higher-order closure model of turbulent exchange at vegetated surfaces. The extent to which 1) canopy position can be used to predict local physiological properties and 2) canopy geometry can be used to predict canopy- level gas exchange will be examined. It is hypothesized that 1) radiation flux is a good predictor of leaf-level gas-exchange within relatively closed canopies, and 2) leaf-level physiology can be predicted by spatial position using a simple structural model. To test these hypotheses and to provide model input parameters. 1) gas-exchange characteristics as a function of vertical position will be sampled and 2) canopy radiation flux/geometry maps using photographic techniques will be constructed. The canopy-level gas-exchange model will be validated using eddy correlation. This research will be conducted in close collaboration with research groups at the University of California at Davis and the New Zealand Forest Research Institute. Field techniques will be tested in an orchard and detailed field studies will be conducted in two well- studied natural forests.