Climate change is predicted to increase temperature and seasonal temperature variance in Great Britain (GB). Sitka spruce (Picea sitchensis (Bong.) Carr) is the most important tree species used in commercial plantations throughout Europe and GB. Frosts that occur outside the winter dormancy period can negatively affect trees, since they happen after dehardening. Damage can be especially severe at bud burst, before emerging needles mature and form protective barriers. Here, we modelled the impact of climate change on frost sensitivity in Sitka spruce with temperature data from five climate projections. The UKCP09 climate model HadRm3 uses emission scenario SRESA1B for the years 2020–2099. The global and downscaled versions of the UKCP18 HadGem3 model use the emissions scenario RCP 8.5. The global model CMCC-CM uses the RCP 4.5 and RCP 8.5 emissions scenarios. The predictions based on these models were compared with results from gridded historical data for the period 1960–2015. Three indicators that assessed the frost sensitivity of Sitka spruce were explored: the total number of frosts between the onset of dehardening and the end of summer, which use three different temperature thresholds (Index 10°C, 1–3°C, 1–5°C); the total number of frosts after bud burst (Index 2); the number of days with minimum temperatures below the resistance level (backlashes) during the hardening–dehardening period (September–August) (Index 3). The indices were validated with historical data for frost damage across GB, and Index 1–3°C, Index 1–5°C and Index 3 were shown to be significantly correlated. The frequency of all frosts and backlashes is expected to decrease with climate change, especially under higher emissions scenarios. Post-bud burst frosts have been historically very rare in GB and remain so with climate change. Downscaled regional climate models detect geographic variability within GB and improve prediction of overall trends in frost damage in comparison to global climate change models for GB.

中文翻译：

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模拟气候变化对英国 Sitka 云杉 (Picea sitchensis) 霜害发生的影响

预计气候变化将增加英国 (GB) 的温度和季节性温度变化。西加云杉 (Picea sitchensis (Bong.) Carr) 是欧洲和英国商业种植园中使用的最重要的树种。冬季休眠期以外发生的霜冻会对树木产生负面影响，因为它们发生在脱硬之后。在新芽成熟并形成保护屏障之前，芽破裂时的损害可能特别严重。在这里，我们利用来自五个气候预测的温度数据模拟了气候变化对 Sitka 云杉霜冻敏感性的影响。UKCP09 气候模型 HadRm3 使用 2020-2099 年的排放情景 SRESA1B。UKCP18 HadGem3 模型的全球和缩小版本使用排放情景 RCP 8.5。全局模型 CMCC-CM 使用 RCP 4.5 和 RCP 8。5 种排放情景。将基于这些模型的预测与 1960-2015 年期间网格化历史数据的结果进行了比较。探讨了评估 Sitka 云杉的霜冻敏感性的三个指标：从脱硬开始到夏季结束之间的霜冻总数，使用三个不同的温度阈值（指数 10°C、1-3°C、1-5 ℃）；萌芽后的霜冻总数（指数 2）；硬化-去硬化期间（9-8 月）（索引 3）期间最低温度低于阻力水平（间隙）的天数。这些指数通过 GB 的冻害历史数据进行了验证，显示指数 1-3°C、指数 1-5°C 和指数 3 显着相关。预计所有霜冻和反弹的频率都会随着气候变化而减少，特别是在较高排放情景下。在英国，芽后爆发霜冻在历史上非常罕见，并且随着气候变化仍然如此。与 GB 的全球气候变化模型相比，缩小的区域气候模型可检测 GB 内的地理变异性，并改进对霜冻损害总体趋势的预测。