Declining hydraulic safety in a drier world

Forests worldwide are increasingly exposed to soil drought under climate change, with their fates depending on the ability to maintain essential functions like water transport (hydraulics) and photosynthesis. Acclimation is expected to mitigate drought impacts, but the extent to which trees acclimate remains largely untested, which limits our predictive confidence. Here, we examined 24 physiological attributes from 40 globally distributed forest throughfall reduction (TFE) experiments and found no evidence that trees adjusted their hydraulic or photosynthetic systems in response to drought. Key attributes related to embolism resistance, hydraulic efficiency, leaf nutrients, and Rubisco carboxylation capacity remained unchanged, regardless of coniferous or broadleaf trees, local precipitation levels, or the duration and severity of drought treatments. However, drought-induced declines in tissue water potentials, combined with unchanged embolism resistance, led to narrower hydraulic safety margins and thus an increased risk of hydraulic failure. Although net photosynthetic rate declined significantly due to stomatal closure, nonstructural carbohydrates (starch and sugars) remained stable, suggesting a shift in carbohydrate allocation toward storage. These findings indicate that trees maintain their hydraulic and photosynthetic capacities under drier conditions, enabling them to maximize carbon assimilation on favorable periods following rainfall, while facing an increased risk of hydraulic failure during drought. Physiological acclimation is unlikely to mitigate future drought impacts, while tree mortality from hydraulic failure is likely to increase.

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Publication Details

Journal
Proceedings of the National Academy of Sciences
Published
2026-08-24
DOI
https://doi.org/10.1073/pnas.2622754123
Primary Topic
Plant Water Relations and Carbon Dynamics
Type
article
Field-Weighted Citation Impact
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article

Declining hydraulic safety in a drier world

Qiuyu Liu, Nate G. McDowell, Hui Liu, Xingyun Liang et al.
Proceedings of the National Academy of Sciences
Plant Water Relations and Carbon Dynamics
article

Declining hydraulic safety in a drier world

Qiuyu Liu, Nate G. McDowell, Hui Liu, Xingyun Liang, Mujuan Deng, Junwei Luan, Pengcheng He, X. L. Lu, Cuiju Liu, Xiangping Tan, Qing Ye, Weibin Li, Shirong Liu, Ze‐Xin Fan, Zhicheng Chen, Cheng Yang, Xin Tan, Defu Wang, Zhongguo Li, Bo Cui, Bin Liu, Jiemin Chen, Keyi Qiu, Ying Jin, Yuxuan Miu, Qinghai Song, Xuhui Zhou, Junhua Yan, Yi Wang
article en

Abstract

Forests worldwide are increasingly exposed to soil drought under climate change, with their fates depending on the ability to maintain essential functions like water transport (hydraulics) and photosynthesis. Acclimation is expected to mitigate drought impacts, but the extent to which trees acclimate remains largely untested, which limits our predictive confidence. Here, we examined 24 physiological attributes from 40 globally distributed forest throughfall reduction (TFE) experiments and found no evidence that trees adjusted their hydraulic or photosynthetic systems in response to drought. Key attributes related to embolism resistance, hydraulic efficiency, leaf nutrients, and Rubisco carboxylation capacity remained unchanged, regardless of coniferous or broadleaf trees, local precipitation levels, or the duration and severity of drought treatments. However, drought-induced declines in tissue water potentials, combined with unchanged embolism resistance, led to narrower hydraulic safety margins and thus an increased risk of hydraulic failure. Although net photosynthetic rate declined significantly due to stomatal closure, nonstructural carbohydrates (starch and sugars) remained stable, suggesting a shift in carbohydrate allocation toward storage. These findings indicate that trees maintain their hydraulic and photosynthetic capacities under drier conditions, enabling them to maximize carbon assimilation on favorable periods following rainfall, while facing an increased risk of hydraulic failure during drought. Physiological acclimation is unlikely to mitigate future drought impacts, while tree mortality from hydraulic failure is likely to increase.

Proceedings of the National Academy of SciencesVol. 123(35)
International Bamboo and Rattan Organization (CN), Pacific Northwest National Laboratory (US), Beijing Botanical Garden (CN), Xishuangbanna Tropical Botanical Garden (CN), Sichuan University of Arts and Science (CN), Ministry of Agriculture (EE), Experimental Center of Tropical Forestry (CN), South China Botanical Garden (CN), HUN-REN Centre for Ecological Research (HU), State Forestry and Grassland Administration (CN), Forest Research (GB), Institute of Forest Ecology, Environment and Protection (CN), University of Chinese Academy of Sciences (CN), Northeast Forestry University (CN), Washington State University (US), Xi'an Jiaotong University (CN)
Openalex Percentile: Top 12%
Plant Water Relations and Carbon Dynamics
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