Does higher diversity in cropping systems ensure improved agroecosystem functions over the long term? A 60-year modeling study under future climate-change scenarios

In the context of multiple crises, transitioning from input-intensive to biodiversity-based cropping systems is imperative to improve agroecosystem sustainability and resilience. A key feature of biodiversity-based cropping systems is higher crop diversity. Long-term assessments of such systems are crucial to determine impacts of higher crop diversity, but these assessments remain rare. This study assessed impacts of higher crop diversity on four agroecosystem functions: soil organic carbon (C) sequestration, nitrogen (N) leaching mitigation, soil water availability for crops, and crop biomass production. The STICS soil-crop model was used to simulate three independent cropping systems with increasing levels of crop diversity (low, medium, and high) over a 60-year period (2010–2070) in Brittany, western France. The three systems, two of which were co-designed, were based on annual crops, and their crop diversity differed in the length and crop species of the crop rotations, as well as in the number and types of intercrops. These systems were simulated for three sites (soil type × climate conditions) and two contrasting climate-change scenarios (RCP 4.5 and RCP 8.5). Predictions indicated that higher crop diversity resulted in less long-term soil C loss and greater soil water availability for crops. However, N leaching was higher in the two most diversified cropping systems, partly due to inadequate fertilizer management in these complex systems. Predictions also indicated that higher crop diversity did not necessarily produce more biomass in all soil types and climate conditions, thus highlighting the need to design site-specific systems. The results also highlighted the potential of mechanistic models for exploring long-term trade-offs in agroecosystem functioning. However, it remains essential to address certain model limitations ( e.g. , lack of certain minor crops, complex intercrops, plant-plant interactions, their legacy effects on soil) to improve assessment of crop diversification strategies using in silico experiments.