Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing, China.
Institute of Carbon Neutrality, Peking University, Beijing, China.
Glob Chang Biol. 2023 Jun;29(12):3395-3408. doi: 10.1111/gcb.16683. Epub 2023 Mar 27.
Monitoring and estimating drought impact on plant physiological processes over large regions remains a major challenge for remote sensing and land surface modeling, with important implications for understanding plant mortality mechanisms and predicting the climate change impact on terrestrial carbon and water cycles. The Orbiting Carbon Observatory 3 (OCO-3), with its unique diurnal observing capability, offers a new opportunity to track drought stress on plant physiology. Using radiative transfer and machine learning modeling, we derive a metric of afternoon photosynthetic depression from OCO-3 solar-induced chlorophyll fluorescence (SIF) as an indicator of plant physiological drought stress. This unique diurnal signal enables a spatially explicit mapping of plants' physiological response to drought. Using OCO-3 observations, we detect a widespread increasing drought stress during the 2020 southwest US drought. Although the physiological drought stress is largely related to the vapor pressure deficit (VPD), our results suggest that plants' sensitivity to VPD increases as the drought intensifies and VPD sensitivity develops differently for shrublands and grasslands. Our findings highlight the potential of using diurnal satellite SIF observations to advance the mechanistic understanding of drought impact on terrestrial ecosystems and to improve land surface modeling.
监测和评估干旱对大区域植物生理过程的影响仍然是遥感和陆面建模的主要挑战，这对于理解植物死亡机制和预测气候变化对陆地碳和水循环的影响具有重要意义。轨道碳观测站 3 号（OCO-3）具有独特的日变化观测能力，为跟踪植物生理干旱提供了新的机会。我们利用辐射传输和机器学习建模，从 OCO-3 太阳诱导叶绿素荧光（SIF）中得出一个下午光合作用抑制的指标，作为植物生理干旱胁迫的指标。这种独特的日变化信号能够实现对植物对干旱的生理响应的空间显式映射。利用 OCO-3 的观测数据，我们检测到 2020 年美国西南部干旱期间普遍存在的干旱胁迫加剧现象。尽管生理干旱胁迫主要与水汽压亏缺（VPD）有关，但我们的结果表明，随着干旱的加剧，植物对 VPD 的敏感性增加，而灌木林和草原的 VPD 敏感性发展方式不同。我们的研究结果强调了利用卫星 SIF 的日变化观测来提高对干旱对陆地生态系统影响的机制理解，并改进陆面模型的潜力。
