Introduction of a novel method to model light interception in multi-species canopies.
Simulating light interception by single plant species within multi-species canopies is critical to modelling growth and transpiration. While there is solid theory and empirical knowledge on light interception by plant canopies, the methods used in process-based agroecosystem models to simulate competition for light do not account simultaneously for variations in canopy architecture, leaf area, and height among more than two species. Our objective is to present a new method to simulate light interception in multi-species canopies and to compare it with existing methods. The new method (Cycles) uses a daily time step and accounts for unlimited species with different heights. It assumes that depending on the relative canopy height, the species light interception is between that of a fully dominant and a fully suppressed species. Leaves from different species are assumed to be randomly mixed in the canopy layer. The methods compared with Cycles were: a sub-daily time step model (Campbell), a daily time step model with unlimited species (APSIM), and a daily time step model for two species with different heights (Wallace). The daily methods provided a good balance between complexity of calculations and accuracy of results when compared to the sub-daily method. When compared for two species, the Cycles and Wallace methods yielded similar results. The Cycles method successfully combined the best attributes of the APSIM and Wallace methods: an unlimited number of species with different heights. The simulations show that representing competition becomes important in species with the same light extinction coefficient and leaf area index (L), but different heights, when the total canopy L is larger than 2 m2/m2. The Cycles method allows simulating in a relatively simple fashion the light interception of different species in the canopy. This method can be easily integrated in agroecosystems models to simulate inter-specific competition in multi-species canopies.
Camargo G.G.T. 2015. Modeling light interception in multi-species canopies. Chapter 3. pp. 26. PhD Dissertation. The Pennsylvania State University.