A systemic approach to model radiation interception and gas exchange in whole-tree peach canopies
2002
Giuliani, R. | Magnanini, E.
A model composed of two sub-systems connected in series was employed to represent short-term whole-canopy radiation interception and gas-exchange processes. Different canopy architectures were chosen to modulate the radiation interception rate that represents the input for net photosynthetic and transpiration responses. Whole-canopy intercepted photon flux (300-1100 nm wavelength) and net photosynthetic and transpiration rates were calculated from experimental radiation and gas-exchange data collected at the tree level in a peach orchard. A remote-sensing approach was adopted to acquire radiation data for the ground area, including the shadow cast by the canopies of differing geometry. The radiation measurements made it possible to calculate canopy geometrical attributes such as sunlit canopy leaf area (Csunlit), i.e. the canopy fraction exposed to direct sunbeam radiation, and foliage array index (FAI), as total canopy leaf area/ sunlit canopy leaf area, both of which were used to explain whole-canopy physiological responses. A linear transfer function between whole-canopy intercepted photon fluxes and corresponding assimilation rates were found. The explanation of the transpiration response as a function of both intercepted quantum flux and canopy-atmosphere vapor pressure deficit was also attempted.
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