Abstract Wheat yield potentials under rainfed Mediterranean conditions have been long limited by late-in-season occurrence of enhanced water deficits and high temperatures, coinciding with sensitive reproductive stages. Present study aims to quantify and separate the impacts of two main abiotic stresses (drought & heat) on potentially attainable wheat yields, in a typical Mediterranean environment of southern Portugal (Alentejo) over 1986—2015. We also evaluate how possible adaptation options could mitigate potential yield losses (reduce the gap between actual and potential yield). Previously calibrated STICS soil-crop model is used for these purposes, which has been satisfactorily evaluated herein for yield simulations using additional field data before running at regional level. By coupling with high-resolution gridded soil and climate datasets, STICS simulations reliably reproduce the inter-annual variability of 30-year regional yield statistics, together with reasonable estimations of experimental potential yields. Therefore, the model is useful to explore the source of yield gap in the region. The quantified impacts, though with some uncertainties, identify the prolonged terminal drought stress as the major cause of yield gap, causing 40–70% mean potential yield losses. In contrast, a short-duration of crop heat stress (≥38 °C) during late grain-filling phase only results in small-to-moderate reductions (up to 20%). Supplemental Irrigation (SI) during reproductive stages provides good adaptive gains to recover potential yield losses by 15–30%, while the proposed early-flowering cultivar is more useful in escaping the terminal heat stress (5–15% adaptive gains) than avoiding prolonged drought stress. In addition, advancing sowing date generally favours wheat production with a robust spatial-temporal pattern. Therefore, combined options based on application of SI, using balanced early-flowering cultivar and early sowing date, may contribute to considerably reduce local yield gap, where current yields can account for 60% of potential yields (26–32% without adaptation). Regional impact assessment and adaptation modelling studies are essential to support agricultural policy development under climate change and variability. The recommended combined adaptation may also represent a promising adaptation strategy for rainfed wheat cropping system in other regions with similar Mediterranean conditions. However, the existing spatial-temporal variability of adaptation response highlights the need to address adaptation strategies at a more detailed local scale with better flexible design.

中文翻译：

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评估近期气候限制对葡萄牙南部地中海气候下小麦潜在产量和适应选择的影响

摘要 地中海雨养条件下的小麦产量潜力长期以来一直受到季节后期缺水和高温的影响，这与敏感的生殖阶段相吻合。本研究旨在量化和分离两种主要非生物胁迫（干旱和高温）对 1986 年至 2015 年葡萄牙南部（阿连特茹）典型地中海环境中潜在小麦产量的影响。我们还评估了可能的适应选项如何减轻潜在的产量损失（减少实际产量和潜在产量之间的差距）。先前校准的 STICS 土壤作物模型用于这些目的，在此已在区域级别运行之前使用额外的现场数据对产量模拟进行了令人满意的评估。通过与高分辨率网格土壤和气候数据集相结合，STICS 模拟可靠地再现了 30 年区域产量统计数据的年际变化，以及对实验潜在产量的合理估计。因此，该模型有助于探索该地区产量差距的来源。尽管存在一些不确定性，但量化的影响将长期的终端干旱胁迫确定为产量差距的主要原因，造成 40-70% 的平均潜在产量损失。相比之下，在灌浆后期的作物热应激（≥38°C）持续时间较短，只会导致小到中度的减少（高达 20%）。生殖阶段的补充灌溉 (SI) 提供了良好的适应性收益，可将潜在的产量损失恢复 15-30%，而提议的早花品种在逃避终末热应激（5-15% 的适应性增益）方面比避免长期干旱胁迫更有用。此外，提前播种通常有利于小麦生产，具有稳健的时空格局。因此，基于 SI 应用的组合选择，使用平衡的早花品种和早播日期，可能有助于大大减少当地的产量差距，目前的产量可以占潜在产量的 60%（没有适应的 26-32%）。区域影响评估和适应模型研究对于支持气候变化和变率下的农业政策制定至关重要。推荐的组合适应也可能代表具有类似地中海条件的其他地区雨养小麦种植系统的有希望的适应策略。然而，适应反应的现有时空变异性强调需要在更详细的局部尺度上通过更好的灵活设计来解决适应策略。