Abstract：
Temperature extremes exert a significant influence on terrestrial ecosystems, but the precise levels at which these extremes trigger adverse shifts in vegetation productivity have remained elusive. In this study, we have derived two critical thresholds, using standard deviations (SDs) of growing-season temperature and satellite-based vegetation productivity as key indicators. Our findings reveal that, on average, vegetation productivity experiences rapid suppression when confronted with temperature anomalies exceeding 1.45 SD above the mean temperature during 2001-2018. Furthermore, at temperatures exceeding 2.98 SD above the mean, we observe the maximum level of suppression, particularly in response to the most extreme high-temperature events. When Earth System Models are driven by a future medium emission scenario, they project that mean temperatures will routinely surpass both of these critical thresholds by approximately the years 2050 and 2070, respectively. However, it is important to note that the timing of these threshold crossings exhibits spatial variation and will appear much earlier in tropical regions. Our finding highlights that restricting global warming to just 1.5°C can increase safe areas for vegetation growth by 13% compared to allowing warming to reach 2°C above preindustrial levels. This mitigation strategy helps avoid exposure to detrimental extreme temperatures that breach these thresholds. Our study underscores the pivotal role of climate mitigation policies in fostering the sustainable development of terrestrial ecosystems in a warming world.
摘要：
极端温度对陆地生态系统产生重大影响，但是，这些极端情况引发植被生产力不利变化的确切水平仍然难以捉摸。在这项研究中,我们得出了两个临界阈值，使用生长季节温度和基于卫星的植被生产力的标准偏差（SD）作为关键指标。我们的发现表明,平均而言,在2001年至2018年期间，当温度异常超过平均温度以上1.45SD时，植被生产力会受到快速抑制。此外，在超过平均值2.98SD的温度下，我们观察到最大程度的抑制，特别是对最极端的高温事件的反应。当地球系统模型由未来的中等排放情景驱动时，他们预测，平均温度将分别在2050年和2070年左右超过这两个关键阈值。然而,重要的是要注意，这些阈值交叉的时间表现出空间变化，并且在热带地区将出现得更早。我们的发现强调，将全球变暖限制在1.5°C可以使植被生长的安全区域增加13％，而允许变暖达到工业化前水平以上2°C。这种缓解策略有助于避免暴露于违反这些阈值的有害极端温度。我们的研究强调了气候缓解政策在气候变暖的世界中促进陆地生态系统可持续发展的关键作用。
