Studies have demonstrated that plant phenophases (e.g. budburst, flowering, ripening) are occurring increasingly earlier in the season across diverse ecologies globally. Despite much interest that climate change impacts have on coffee (Coffea arabica), relatively little is known about the driving factors determining its phenophases. Using high-resolution microclimatic data, this study provides initial insights on how climate change is impacting C. arabica phenophases in Tanzania. In particular, we use generalized additive models to show how warming nocturnal temperatures (Tnight), as opposed to day-time or maximum temperatures, have a superseding effect on the ripening of coffee and subsequent timing of harvest. A warm night index (WNI), generated from mean nocturnal temperature, permits accurate prediction of the start of the harvest season, which is superior to existing methods using growing degree days (GDD). The non-linear function indicates that a WNI of 15 °C is associated with the latest ripening coffee cherries (adjusted R2 = 0.95). As the WNI increases past the inflection point of ~ 16 °C, ripening occurs earlier and progresses more or less linearly at a rate of ~ 17 ± 1.95 days for every 1 °C increase in WNI. Using the WNI will thus not only allow farmers to more accurately predict their harvest start date, but also assist with identifying the most suitable adaptation strategies which may reduce harvest-related costs and buffer potential losses in quality and production.

中文翻译：

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温暖的夜晚促使小粒咖啡在坦桑尼亚成熟

研究表明，在全球不同生态系统中，植物物候期（例如萌芽、开花、成熟）越来越早地出现在季节中。尽管气候变化对咖啡（小粒咖啡）产生了很大的影响，但对决定其物相的驱动因素知之甚少。使用高分辨率小气候数据，这项研究提供了关于气候变化如何影响坦桑尼亚的 C. arabica 物相的初步见解。特别是，我们使用广义加法模型来展示与白天或最高温度相反的夜间温度升高（夜间）如何对咖啡的成熟和随后的收获时间产生替代影响。从平均夜间温度生成的暖夜指数 (WNI) 可以准确预测收获季节的开始，这优于使用生长度日（GDD）的现有方法。非线性函数表明 15 °C 的 WNI 与最新成熟的咖啡樱桃有关（调整后的 R2 = 0.95）。随着 WNI 增加超过 ~ 16 °C 的拐点，WNI 每增加 1 °C，成熟发生得更早并且或多或少地以 ~ 17 ± 1.95 天的速度线性进展。因此，使用 WNI 不仅可以让农民更准确地预测他们的收获开始日期，还可以帮助确定最合适的适应策略，从而降低与收获相关的成本并缓冲质量和生产方面的潜在损失。随着 WNI 增加超过 ~ 16 °C 的拐点，WNI 每增加 1 °C，成熟发生得更早并且或多或少地以 ~ 17 ± 1.95 天的速度线性进展。因此，使用 WNI 不仅可以让农民更准确地预测他们的收获开始日期，还可以帮助确定最合适的适应策略，从而降低与收获相关的成本并缓冲质量和生产方面的潜在损失。随着 WNI 增加超过 ~ 16 °C 的拐点，WNI 每增加 1 °C，成熟发生得更早并且或多或少地以 ~ 17 ± 1.95 天的速度线性进展。因此，使用 WNI 不仅可以让农民更准确地预测他们的收获开始日期，还可以帮助确定最合适的适应策略，从而降低与收获相关的成本并缓冲质量和生产方面的潜在损失。