Agroforestry systems and climate change: could AFS mitigate adverse effects of climate change on crops in temperate areas?
Résumé
Large concerns over the impact of climate change on agriculture in temperate countries have been raised recently. The current stagnation of agricultural yields for most of the major crops in Europe, but also in other temperate areas of the world, has been evidenced. Climate change may be a major explanation for this. Excess heat in spring and increased water stresses seem to be involved in the process. We discuss how alley-cropping systems may cope with such climate changes. We used the Hi-sAFe process-based agroforestry model to analyse the behaviour of some agroforestry systems with various climate change scenarii. The model integrates light, water and nitrogen competition in 3D at the day time step, and allows for adaptive rooting patterns of trees
and crops to cope with water and nitrogen heterogeneity in the soil. Walnut and poplar systems were simulated. The long-term resilience of the system was assessed by calculating indicators of the sustainability of crop yields. Intercrops exhibited a lower yield variability over time than pure crops. The Land Equivalent Ratio of the system was significantly increased with climate change. The model indicated that several processes were responsible for this : the reduction of heat shocks on cereal flowering and grain filling in the shade was expected, but the reduction of nitrogen stresses was more a surprise. However, the model would need to be upgraded to include several processes that are not implemented yet such as the windbreak effect. The model may also allow to optimise the sustainability of the system by adjusting the choice of tree and crop varieties.