Drought, as an intermittent disturbance of the water cycle, profoundly impacts the terrestrial ecosystem. Recovery time (RT) of an ecosystem from drought is an important indicator of assessing drought impacts and ecosystem resilience, yet the spatiotemporal pattern of ecosystem postdrought RT remains controversial in existing studies. Here we investigate the spatiotemporal pattern of postdrought RT across global terrestrial ecosystems using two observation-based gross primary productivity (GPP) data sets: direct flux-site observations and gridded estimates by upscaling flux-site observations using machine-learning approach. For droughts that occur on average once every 5.2 years, the RT typically ranges between 2 and 8 months, with a global mean RT of ∼6 months. Spatially, both GPP data sets show a significant bilinear relationship between RT and moisture gradient, and that ecosystems in arid and humid regions tend to recover from drought more rapidly than semi-arid/sub-humid ecosystems. Additionally, forests show an overall longer RT than shrublands and grasslands. Temporally, global ecosystem RT shows a slight yet significant increasing trend (0.032 months yr⁻¹) during 1982–2010, which is partly caused by the increasing drought for the same period. However, the observed patterns of RT across global bio-climatic zones are not captured by the state-of-the-art land surface models, which exhibit a shorter RT in semi-arid/sub-humid ecosystems but longer RT in arid/humid regions, and a larger increasing trend of RT over time (0.069 months yr⁻¹). Our findings provide crucial insights into ecosystem vulnerability to sub-decadal stress events and ecosystem recovery trajectories among diverse bio-climatic regions and highlight potential model deficiencies that should be accounted for in future model developments.

中文翻译：

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全球陆地生态系统的干旱后恢复时间

干旱作为水循环的间歇性干扰，深刻影响着陆地生态系统。生态系统从干旱中恢复的时间 (RT) 是评估干旱影响和生态系统恢复力的重要指标，但生态系统干旱后 RT 的时空模式在现有研究中仍存在争议。在这里，我们使用两个基于观测的总初级生产力 (GPP) 数据集来研究全球陆地生态系统干旱后 RT 的时空模式：直接通量站点观测和通过使用机器学习方法放大通量站点观测的网格估计。对于平均每 5.2 年发生一次的干旱，RT 通常在 2 到 8 个月之间，全球平均 RT 约为 6 个月。在空间上，两个 GPP 数据集都显示 RT 和水分梯度之间存在显着的双线性关系，干旱和潮湿地区的生态系统往往比半干旱/半湿润生态系统更快地从干旱中恢复。此外，森林比灌木地和草原显示出整体更长的 RT。从时间上看，全球生态系统 RT 呈现出轻微但显着的增长趋势（0.032 个月 yr⁻¹ ) 1982-2010 年，部分原因是同期干旱加剧。然而，在全球生物气候区观察到的 RT 模式并没有被最先进的地表模型捕获，这些模型在半干旱/半湿润生态系统中表现出较短的 RT，但在干旱/湿润生态系统中表现出较长的 RT区域，以及随着时间的推移（0.069 个月^-1），RT 有更大的增加趋势。我们的研究结果为生态系统对次年代压力事件的脆弱性和不同生物气候区域的生态系统恢复轨迹提供了重要见解，并突出了在未来模型开发中应考虑的潜在模型缺陷。