Dryland ecosystems are highly vulnerable to extreme droughts under climate change. Yet, response of vegetation productivity across global drylands to changes in drought stress in a warming climate remains obscure. Here, we investigated future changes in drought stress, characterized by low soil moisture (SM) and high vapor pressure deficit (VPD), under severe drought conditions and its impact on gross primary productivity (GPP) deviations in drylands, based on the Coupled Model Intercomparison Project Phase 6 (CMIP6) Earth system model (ESM) simulations. Under both intermediate (SSP2-4.5) and high (SSP5-8.5) emission scenarios, the dryland ecosystems are projected to experience more intense, extensive and frequent severe drought events owing to increasing VPD. The probabilities of high VPD-dominated drought stress in the end of the 21st century would be nearly double (2.1–2.4 times) of the present-day (39%). Excluding the carbon dioxide (CO) fertilization effect, the annual GPP loss caused by severe drought is projected to further deteriorate over more than half fraction (56.9–70.9%) of global vegetated dryland areas, reaching 2.0 (1.9–2.2) times of the present-day (with an area-weighted total of −21.5 KgC m yr) by the end of the 21st century. Such aggravating reduction is predominantly induced by drought stress with higher-than-usual VPD anomaly. The high VPD-dominated drought stress would lead to approximately 100% (95–102%) of annual aggregated dryland GPP loss by the end of 21st century from the present-day 68%. Our results suggest an increasing risk of high atmospheric aridity-dominated drought stress on dryland ecosystems. It is of great urgency to make adaption and mitigation strategies for the natural and cultivated vegetation in drylands.

中文翻译：

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全球变暖导致大气干旱度升高导致干旱胁迫加剧旱地生产力损失


旱地生态系统极易受到气候变化下极端干旱的影响。然而，全球旱地植被生产力对气候变暖中干旱胁迫变化的反应仍然模糊。在这里，我们基于耦合模型研究了严重干旱条件下以低土壤水分（SM）和高蒸气压赤字（VPD）为特征的干旱胁迫的未来变化及其对旱地总初级生产力（GPP）偏差的影响比对项目第 6 阶段 (CMIP6) 地球系统模型 (ESM) 模拟。在中度（SSP2-4.5）和高度（SSP5-8.5）排放情景下，由于VPD增加，旱地生态系统预计将经历更强烈、更广泛和更频繁的严重干旱事件。到 21 世纪末，以 VPD 为主的高干旱胁迫的概率将是目前（39%）的近两倍（2.1-2.4 倍）。剔除二氧化碳（CO）施肥效应后，严重干旱造成的年度GPP损失预计将进一步恶化，超过一半（56.9-70.9%）的全球旱地植被面积将达到2.0（1.9-2.2）倍。到 21 世纪末，目前（面积加权总量为-21.5 KgC m yr）。这种加剧的减少主要是由干旱胁迫和高于平常的 VPD 异常引起的。到 21 世纪末，以 VPD 为主的高干旱胁迫将导致每年旱地 GPP 损失从目前的 68% 减少约 100%（95-102%）。我们的研究结果表明，旱地生态系统面临以大气干旱为主的干旱胁迫的风险不断增加。针对旱地自然和栽培植被制定适应和减缓策略刻不容缓。