Flash droughts and their ecological impacts on terrestrial ecosystems have recently garnered increased attention due to their rapid intensification. However, research on the response and recovery of ecosystems to flash droughts, particularly regarding different types of flash droughts and their determinants, remains relatively limited. Here we classified flash droughts into meteorological, evaporative, and soil types based on the differences in primary drivers, and identified them in the middle and lower reaches of Yangtze River Basin (MLRYRB) from 2000 to 2022. We assessed the response and recovery time of ecosystems to different flash droughts based on solar-induced chlorophyll fluorescence (SIF), analyzed the factors affecting response and recovery times using random forest models, and identified the spatial patterns of dominant factors through partial correlation analysis. Our results revealed distinct characteristics among different flash droughts, with soil flash droughts exhibiting the highest frequency and longest duration. The average response time and recovery times ranged from 15.7 to 19.2 days and from 59.6 to 69.2 days, respectively, for different flash droughts, with soil flash droughts presenting the longest response time and shortest recovery time. Among all vegetations, mixed forests exhibited the longest response time to meteorological and soil flash droughts, while woody savannas presented significantly longer recovery time from evaporative and soil flash droughts. Analysis of primary drivers indicated that precipitation predominantly determined the response time to meteorological and evaporative flash droughts, while surface soil moisture played a primary role in soil flash drought. Furthermore, surface soil moisture was found to determine the recovery time from all flash droughts in over 57 % of pixels. Our findings could offer valuable insights into quantifying the ecological impacts and drivers of different flash droughts on ecosystems, deepening our understanding of ecosystem responses to flash droughts.

中文翻译：

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土壤湿度和降水主导着长江流域不同类型突发干旱生态系统的响应和恢复时间


突发干旱及其对陆地生态系统的生态影响最近由于其迅速加剧而引起了越来越多的关注。然而，关于生态系统对突发干旱的响应和恢复的研究，特别是关于不同类型的突发干旱及其决定因素的研究仍然相对有限。根据主要驱动因素的差异，我们将突发干旱分为气象、蒸发和土壤类型，并识别了2000年至2022年长江中下游地区（MLRYRB）的突发干旱。我们评估了干旱的响应和恢复时间。基于太阳诱导叶绿素荧光（SIF）的生态系统对不同突发干旱的响应，利用随机森林模型分析了影响响应和恢复时间的因素，并通过偏相关分析确定了主导因素的空间格局。我们的结果揭示了不同突发干旱的不同特征，其中土壤突发干旱表现出最高频率和最长持续时间。不同突发干旱的平均响应时间和恢复时间分别为15.7~19.2天和59.6~69.2天，其中土壤突发干旱的响应时间最长，恢复时间最短。在所有植被中，混交林对气象和土壤突发干旱的响应时间最长，而木本稀树草原对蒸发和土壤突发干旱的恢复时间明显更长。主要驱动因素分析表明，降水主要决定对气象和蒸发突发干旱的响应时间，而表层土壤湿度在土壤突发干旱中起主要作用。 此外，发现表面土壤湿度决定了超过 57% 的像素从所有突发干旱中恢复的时间。我们的研究结果可以为量化不同突发干旱对生态系统的生态影响和驱动因素提供有价值的见解，加深我们对生态系统对突发干旱反应的理解。