Siberia experienced a prolonged heatwave in the spring of 2020, resulting in extreme summer drought and major wildfires in the North-Eastern Siberian lowland tundra. In the Arctic tundra, plants play a key role in regulating the summer land surface energy budget by contributing to land surface cooling through evapotranspiration. Yet we know little about how drought conditions impact land surface cooling by tundra plant communities, potentially contributing to high air temperatures through a positive plant-mediated feedback. Here we used high-resolution land surface temperature and vegetation maps based on drone imagery to determine the impact of an extreme summer drought on land surface cooling in the lowland tundra of North-Eastern Siberia. We found that land surface cooling differed strongly among plant communities between the drought year 2020 and the reference year 2021. Further, we observed a decrease in the normalized land surface cooling (measured as water deficit index) in the drought year 2020 across all plant communities. This indicates a shift towards an energy budget dominated by sensible heat fluxes, contributing to land surface warming. Overall, our findings suggest significant variation in land surface cooling among common Arctic plant communities in the North-Eastern Siberian lowland tundra and a pronounced effect of drought on all community types. Based on our results, we suggest discriminating between functional tundra plant communities when predicting the drought impacts on energy flux related processes such as land surface cooling, permafrost thaw and wildfires.

中文翻译：

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夏季干旱削弱了苔原植被的地表冷却

2020年春季，西伯利亚经历了长时间的热浪，导致西伯利亚东北部低地苔原出现夏季极端干旱和重大野火。在北极苔原，植物通过蒸散作用促进地表冷却，在调节夏季地表能量收支方面发挥着关键作用。然而，我们对干旱条件如何影响苔原植物群落的地表降温知之甚少，并可能通过植物介导的正反馈导致高气温。在这里，我们使用基于无人机图像的高分辨率地表温度和植被地图来确定极端夏季干旱对西伯利亚东北部低地苔原地表冷却的影响。我们发现，2020 年干旱年和 2021 年参考年之间，植物群落的地表降温存在很大差异。此外，我们观察到 2020 年干旱年，所有植物群落的标准化地表降温（以缺水指数衡量）均有所下降。这表明能源预算转向以感热通量为主，从而导致地表变暖。总体而言，我们的研究结果表明，西伯利亚东北部低地苔原常见北极植物群落的地表冷却存在显着差异，并且干旱对所有群落类型都有显着影响。根据我们的结果，我们建议在预测干旱对地表冷却、永久冻土融化和野火等能量通量相关过程的影响时，区分功能性苔原植物群落。