Winter cereal production in a Mediterranean silvoarable walnut system in the face of climate change

One of the foreseeable consequences of climate change is a reduction in crop yields. In recent years, agroforestry systems have been identified as a strategy for climate change mitigation and adaptation. In this study we assess the potential of a silvoarable system to protect crops against extreme climate events. We studied a 9-year-old hybrid walnut silvoarable system (Juglans x intermedia Mj209xRa) intercropped with cultivars of two winter cereals - wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) - for three consecutive years and compared it with monocrops and pure tree plantations. The parameters studied were grain and total biomass yield, harvest index, grain size and tree diameter increment. Plant phenology and soil and plant nutrients were also examined. Climate conditions and tree presence conditioned cereal yields, and the responses to silvoarable conditions differed among cereal species and cultivars. The silvoarable system with barley had higher production than monocrops in years with early heat events (yield increment of 55% in the first year and 15% in the second year). For wheat, no positive effect of trees in the silvoarable system was found, although grain quality improved significantly (2.56% and 2.76% N grain content in monocrops and silvoarable systems, respectively). Tree growth, measured as diameter at breast height increment, was lower in the silvoarable system (2.06 cm at the end of the study) than in the monospecific plantation (2.83 cm in the same period). The land equivalent ratio was always higher than 1 (1.34-2.08), showing that the silvoarable system was more productive than sole pure plantations and cereal monocrops.