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Complementarity of Light and Water Use in Tropical Agroforests. I. Theoretical Model Outline, Performance and Sensitivity
註釋Agroforestry models are needed to help define the biophysical boundary conditions where agroforestry may be beneficial. A generic, process-based model is outlined which couples light and water use in a tree-crop-soil system. The model predicts the net primary production (NPP) of a uniform overstorey of tropical broadleaved trees, using parts of the model Hybrid [Friend, A.D., et al., 1997. A process-based, biogeochemical, terrestrial biosphere model of ecosystem dynamics (Hybrid v3.0). Ecol. Model. 95; 249-287.] and the growth and grain yield of an understorey sorghum crop, using PARCH [Bradley, R.G., Grout, N.M.J., 1994. PARCH-User Guide. Tropical Crops Research Unit, University of Nottingham, Sutton Bonington, Leicestershire, UK, 122 pp.]. Belowground competition for water is simulated. The model is driven by daily climate, which can be generated for any half-degree pixel in the world. The performance of the model is illustrated for a site in Ghana. The model gives validated output of the NPP of natural forest/woodland vegetation and of potential sorghum grain yield. Tests of the sensitivity of the model to simplifying assumptions are presented and discussed. It is concluded that the model provides a useful tool to explore opportunities for complementarity of light and water use by trees and sorghum in a range of climates.