Quantifying the impact of pruning on young cocoa trees using a functional-structural plant model

• A new functional structural plant model was developed to simulate pruning effects on cocoa trees. • The model captured short-term pruning effects on tree structure. • Compensatory growth after pruning was partially captured by the model. • Simulated increase in light interception efficiency was lost due to compensatory growth. • Dynamic simulations are needed to predict pruning effects in cocoa. Pruning affects tree functioning by removing biomass and triggering compensatory responses. Functional-structural plant (FSP) models, combining three-dimensional plant architecture with physiological processes, are suitable tools to study pruning effects. We present and evaluate the first FSP model for cocoa trees and we simulate pruning impact on young cocoa tree functioning. We performed two experiments: a parametrization experiment, assessing branching responses to pruning treatments (heading and thinning); and an evaluation experiment measuring the pruning effects on stem radius, leaf number and crown diameter of cocoa trees. We developed an FSP model that simulates tree growth as a result of the interaction between physiological processes, tree architecture and pruning-induced changes in branching patterns. Bud break is simulated stochastically, based on bud position and pruning interventions and was parameterized with field observations. The evaluation experiment was replicated in silico to evaluate model predictions and quantify the effect of pruning on tree functioning. Our model captured the immediate effects of pruning on tree structure and partially simulated the compensatory response in leaf production observed in the experiment. In the simulations, pruning reduced total light interception. The simulated mean light interception per unit leaf area was increased in one treatment. However, this advantage was quickly lost due to induced branch production. Our model is a novel tool to study the impact of pruning, as it explicitly simulates tree architecture and pruning-induced responses. Our results highlight the necessity of dynamic simulations to understand pruning impact.