Abstract
Context The global shift toward sustainable agriculture has increased interest in using process-based models to design and optimize intercropping systems. However, these models differ fundamentally in how they represent trade-offs (competition for light, water, and nutrients) and synergies (facilitation, complementarity) in resource sharing between species. This conceptual variation creates uncertainty in model selection and application, particularly since most models were originally developed for monoculture and subsequently adapted for intercropping. Objective In this study, we describe how current crop models represent interspecies resource-sharing mechanisms, analyse their structural differences, and synthesize findings from existing validation studies to understand how their structural differences affect model performance. The models examined include APSIM (APSIM-Canopy, APSIM-Micromet, APSIM-Strip, APSIM-Alternating, APSIM-APSwim, APSIM-SoilArbitrator), DayCent, DSSAT-Mixed, DSSAT-MPI, LandscapeDNDC, LUCIA, MONICA, SIMPLACE Lintul5-Intercrop, STICS-Big-Leaf, STICS-Multilayer, and WaNuLCAS. Methods Through the Agricultural Model Intercomparison and Improvement Project (AgMIP) platform, we engaged with model developers and expert users to collect detailed information on how crop models represent intercropping systems using structured interviews and questionnaires. We then developed a framework that groups models by their core conceptual approaches to simulating resource sharing. Finally, we synthesize findings from existing quantitative validation studies to connect conceptual intercomparison to predictive performance across different intercrop characteristics and environments. Results and Conclusions Our analysis identifies six distinct conceptual approaches for simulating light sharing and four for belowground resource (water and nutrient) competition. Intercrop models show greater structural divergence in canopy than in belowground representation. Furthermore, competitive trade-offs (light, water, and nutrients) are widely represented while facilitative and other complex processes like N₂-fixation, plasticity (shoot and root), microclimate effects or hydraulic lift are often simplified or omitted. Our analysis of model validation studies reveals a critical trade-off: structurally complex models often perform well in simulating intercropping when calibration is done on sole crops, whereas simpler models require extensive intercrop-specific calibration to achieve better prediction performance. This distinction is vital for model application in data-scarce environments, as more complex architectures can leverage existing sole-crop data to effectively simulate intercrop systems. The classification of the structural resource capture differences in combination with the evaluated model performance analysis allowed us to devise an evidence-based model selection criteria framework useful also for for non-specialist , while the unique detailed description provided are highly valuable for the model research community. Significance This study establishes a conceptual framework that provides the necessary foundation for a meaningful quantitative intercomparison of intercrop models, as structural understanding enables the interpretation of numerical differences in model outputs. It also guides hypothesis testing, model choice, priorities in model development and improvements.
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Claims 9
Claim · model-written summary
Six distinct conceptual approaches were identified for simulating light sharing in intercrop models.
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e1“Our analysis identifies six distinct conceptual approaches for simulating light sharing and four for belowground resource (water and nutrient) competition”
Claim · model-written summary
Four conceptual approaches were identified for simulating belowground resource (water and nutrient) competition.
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e1“Our analysis identifies six distinct conceptual approaches for simulating light sharing and four for belowground resource (water and nutrient) competition”
Claim · model-written summary
Intercrop models show greater structural divergence in the canopy than in belowground representation.
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e2“Intercrop models show greater structural divergence in canopy than in belowground representation”
Claim · model-written summary
Competitive trade-offs for light, water and nutrients are widely represented in intercrop models.
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e3“competitive trade-offs (light, water, and nutrients) are widely represented”
Claim · model-written summary
Facilitative and other complex processes are often simplified or omitted in intercrop models.
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e4“facilitative and other complex processes like N₂-fixation, plasticity (shoot and root), microclimate effects or hydraulic lift are often simplified or omitted”
Claim · model-written summary
Structurally complex models often performed well in simulating intercropping when calibrated on sole crops.
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e5“structurally complex models often perform well in simulating intercropping when calibration is done on sole crops”
Claim · model-written summary
Simpler models required extensive intercrop-specific calibration to achieve better prediction performance.
- Outcome
- extensive intercrop-specific calibratione6
- Qualifier
- to achieve better prediction performancee6
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e6“whereas simpler models require extensive intercrop-specific calibration to achieve better prediction performance”
Claim · model-written summary
More complex model architectures can leverage existing sole-crop data to simulate intercrop systems.
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e7“more complex architectures can leverage existing sole-crop data to effectively simulate intercrop systems”
Claim · model-written summary
An evidence-based model selection criteria framework was devised for intercrop models.
- Outcome
- evidence-based model selection criteria frameworke0
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e0“devise an evidence-based model selection criteria framework”