A Dynamic System Model of Climate-Driven Fruiting Occurrence in Smallholder Duku (Lansium domesticum) Orchards

Agricultural Engineering Study Program, Sriwijaya University, Indonesia

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Abstract

Interannual alternation between fruiting and non-fruiting years remains a persistent challenge in tropical perennial fruit-crop systems, particularly in smallholder orchards that are managed as semi-natural stands in Muara Enim District, Sumatera Selatan Province, Indonesia. This study developed a parsimonious climate-driven dynamic system model to simulate annual fruiting occurrence in duku (Lansium domesticum) under unmanaged orchard conditions. The model operated at a monthly time step and represented two internal state variables: carbohydrate reserve and seasonal fruit potential. Monthly rainy days were used as the climatic forcing variable, with dry-season conditions regulating flowering induction, and excessive wetness during subsequent reproductive development increasing fruit loss. Temporal calibration and validation were conducted in one core sub-district, followed by spatial testing across additional sub-districts without recalibration, one-at-a-time sensitivity analysis, and ±10% rainy-day perturbation scenarios. The model reproduced alternating fruiting and non-fruiting patterns as an emergent outcome of reserve accumulation, induction thresholds, fruit loss, and post-harvest reset. Spatial validation indicated that one parameter set could be transferred across locations, although local rainfall regimes generated heterogeneous sensitivity to modest climatic perturbation. These findings place duku fruiting within a broader class of perennial fruit systems that respond to climate through delayed, threshold-mediated, and internally buffered processes rather than through direct, linear effects. The proposed framework provides a transparent tool for data-limited regions where reliable yield records are scarce, while supporting comparative risk assessment across heterogeneous smallholder production landscapes.