Alley Cropping Mitigates the Impacts of Climate Change on a Wheat Crop in a Mediterranean Environment: A Biophysical Model-Based Assessment

Francesco Reyes,Isabelle Lecomte,Kevin J Wolz,Christian Dupraz,Marie Gosme

doi:10.3390/agriculture11040356

Abstract

Introduction: Climate change (CC) and the increased occurrence of extreme climatic events pose a serious threat to crop yields and their stability worldwide. This study analyzed the CC mitigation potential of an alley cropping system on crop physiological stresses and growth as compared to a monoculture system. Materials and Methods: Growth of winter durum wheat, cultivated alone (agriculture) and in combination with hybrid walnut (agroforestry), was simulated with the Hi-sAFe agroforestry model, as driven by business-as-usual Intergovernmental Panel on Climate Change (IPCC) projections, split into three scenarios, representing Past (1951–1990), Present (1991–2030), and Future (2031–2070) climatic conditions. Crop growth and the occurrence of thermal, nitrogen, and water stresses were analyzed. Results: Cold-related stresses were modest in Past and almost disappeared over time. Heat, drought, and nitrogen stresses increased about twofold from Past to Future, but were reduced by 20–35% in agroforestry, already with medium-sized trees (diameter at breast height (DBH) of about 10–15 cm). Crop yields in agriculture increased from Past to the end of Present and then remained stable. This moderately decreased with tree age in agroforestry (especially in Future). Discussion: The impact of CC on the crop was buffered in agroforestry, especially for the most extreme climatic events. The mitigation of crop microclimate and the increased stability of crop yields highlight the potential of agroforestry as a CC adaptation strategy.

Highlights

Climate change (CC) and the increased occurrence of extreme climatic events pose a serious threat to crop yields and their stability worldwide
Trees started mitigating most stresses after they had reached a sufficient size: high temperature stress on grain filling and water stress on radiation use efficiency were reduced for DBH lower than 10 cm (10-year-old plants); water stress inducing earlier senescence and nitrogen stress on leaf growth were reduced starting with DBH of about 20–30 cm (15–20-year-old plants); and high temperature stress on leaf photosynthesis were reduced starting with DBH of about 30 cm (20-year-old plants) (Figure S7)
Simulations with the Hi-sAFe model show that the complementarity for light use was high between hybrid walnut trees and winter wheat cultivated in Southern France, and resulted in a limited reduction of wheat yield until the trees reached a large size

Summary

Introduction

Climate change (CC) and the increased occurrence of extreme climatic events pose a serious threat to crop yields and their stability worldwide. Crop yields in agriculture increased from Past to the end of Present and remained stable. This moderately decreased with tree age in agroforestry (especially in Future). Whether a crop may benefit or not of such a change depends on whether the site-specific microclimate will increasingly meet optimal crop growth temperatures at each development stage (e.g., by reducing frost risk in the cold season, while increasing respiration costs and carbon losses or the occurrence of drought stress in the hot season) [2]. Temperature increase has been suggested to be the cause of long-term yield stagnation in Europe despite continuing efforts to improve cultivars [6]

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