Competition for light in heterogeneous canopies: Application of MAESTRA to a coffee (Coffea arabica L.) agroforestry system

•The light-absorption module of MAESTRA was checked successfully in a 2-layered heterogeneous agroforestry system•The effects of shade trees on light availability and fraction of diffuse light for the understorey were mapped•Light budgets were assessed with a resolution from resprout-to-plant-to-plot and semi-hourly to yearly•Continuous light budget can be generated as a covariable for numerous types of experimentations•A simpler approach to simulate the effects of tree density on the understorey is also proposed In agroforestry systems (AFS), quantifying the competition for light is a prerequisite toward understanding the impact of shade trees on the productivity of the under-crop. Models for homogeneous canopies and shade/full-sun approaches do not address the intra-plot heterogeneity, typical of AFS. For the first time, MAESTRA, a 3D light absorption model, was fully parameterized in a heterogeneous 2-canopy layers AFS. We quantified competition for photosynthetic photon flux density (Q) between shade trees (Erythrina poepiggiana) and coffee (Coffea arabica), with a spatial resolution from the plant to the plot (2.7ha) and a temporal resolution from half-hour to one full year. The predicted transmittance through the 2-canopy layers was verified against field measurements. The goodness of fit (R2>0.75, RRMSE