How cereal acclimatation under tree canopy affects grain production in Mediterranean agroforestry systems

The increasing global population, in a scenario of climate change, poses the challenge of producing cereals more efficiently and climate-resilient, especially in water-limited regions such as the Mediterranean. The adoption of agroforestry systems has been proposed as a viable solution to address this issue. Tree presence favours a microenvironment under its canopy that facilitates the mitigation of climatic extremes, potentially benefiting cereal development in the context of climate change. However, it remains unclear how cereal production is affected by tree competition and light reduction, particularly in the Mediterranean region, and to what extent net outcomes depend on the type of tree (deciduous vs. evergreen) present. Microclimate, phenological, morphological and physiological parameters and cereal production were analysed in two experimental sites: one with evergreen oaks and another with walnuts as overstory, in 2018. In both experiments, wheat and barley were sown under and outside of the tree canopy. Smoothing in weather conditions (specifically temperature and relative air humidity) was detected under trees in both systems. In the evergreen tree site, barley grain yield increased, and wheat yield was maintained under trees, despite results indicated certain competition for soil water. By contrast, in the deciduous site, cereal yield was reduced under the canopy, partly explained by the competition among trees and cereals for soil nutrients. In all cases, it is recommended to use early varieties to avoid competition for water with evergreen trees and for light and nutrients with deciduous trees.