Transpiration, the dominant component of terrestrial evapotranspiration (ET), directly connects the water, energy and carbon cycles and is typically restricted by soil and atmospheric (for example, the vapour pressure deficit (VPD)) moisture stresses through plant hydraulic processes. These sources of stress are likely to diverge under climate change, with a globally enhanced VPD but more variable and uncertain changes in soil moisture. Here, using a model–data fusion approach, we demonstrate that the common empirical approach used in most Earth system models to evaluate the ET response to soil moisture and VPD, which neglects plant hydraulics, underestimates ET sensitivity to VPD and compensates by overestimating the sensitivity to soil moisture stress. A hydraulic model that describes water transport through the plant better captures ET under high VPD conditions for wide-ranging soil moisture states. These findings highlight the central role of plant hydraulics in regulating the increasing importance of atmospheric moisture stress on biosphere–atmosphere interactions under elevated temperatures.

蒸腾作用是陆地蒸散（ET）的主要组成部分，直接连接水，能量和碳循环，通常受植物水力过程中土壤和大气（例如，蒸气压亏缺（VPD））的水分压力的限制。这些压力的来源在气候变化下可能会有所不同，VPD在全球范围内有所提高，但土壤水分的变化却更加不确定。在这里，使用模型-数据融合方法，我们证明了大多数地球系统模型中用于评估ET对土壤水分和VPD的响应的通用经验方法，这种方法忽略了植物的水力作用，低估了ET对VPD的敏感性，并通过过高估计了敏感性来进行补偿土壤水分压力。在整个土壤水分状态广泛的高VPD条件下，描述水通过植物的水力模型可以更好地捕获ET。这些发现突显了植物液压系统在调节大气湿度对高温下生物圈与大气层相互作用的重要性日益增强中的核心作用。