Lyu et al. (2026) Warming overwhelms CO2-driven drought mitigation in alpine vegetation on the Qinghai-Tibetan Plateau

Identification

• Journal: Communications Earth & Environment
• Year: 2026
• Date: 2026-02-21
• Authors: He Lyu, Peng Wang, Su Jian, David Wårlind, Jürgen Knauer, Lina Teckentrup, J. Chang, Xiyan Xu, Chen Chen, Tao Zhang, Jian Ni, Stephen Sitch, Yongshuo Fu, Belinda E. Medlyn, Benjamin Smith, Yuanhe Yang, Mingkai Jiang
• DOI: 10.1038/s43247-026-03308-2

Research Groups

• State Key Laboratory for Vegetation Structure, Function and Construction (VegLab), College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
• Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden
• School of Life Sciences, Faculty of Science, University of Technology Sydney, Ultimo, NSW, Australia
• Barcelona Supercomputing Center, Barcelona, Spain
• Zhejiang Key Laboratory of Agricultural Remote Sensing and Information Technology, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, Zhejiang, China
• State Key Laboratory of Earth System Numerical Modeling and Application, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
• Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
• College of Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang, China
• Faculty of Environment, Science and Economy, University of Exeter, Exeter, UK
• College of Water Sciences, Beijing Normal University, Beijing, China
• Hawkesbury Institute for the Environment, Western Sydney University, Penrith, Australia
• Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China
• China National Botanical Garden, Beijing, China
• University of Chinese Academy of Sciences, Beijing, China

Short Summary

This study investigates the combined effects of rising atmospheric carbon dioxide (CO₂) and warming on alpine vegetation drought responses on the Qinghai-Tibetan Plateau. It finds that while CO₂ rise alone mitigated drought-induced productivity losses by 5.7%, concurrent warming reversed this benefit, intensifying drought stress by 5.2% due to increased plant water demand.

Objective

• To disentangle how increasing atmospheric CO₂ concentrations (iCO₂) affect vegetation responses to drought stress across the Qinghai-Tibetan Plateau (QTP).
• To determine the role of background warming in modulating the relationship between iCO₂ and vegetation drought responses.
• To quantify how these effects differ between permafrost and non-permafrost areas on the QTP.

Study Configuration

• Spatial Scale: Qinghai-Tibetan Plateau (QTP), with additional multi-model intercomparison for pan-Arctic permafrost regions (≥ 50°N).
• Temporal Scale: 1979–2018 (40 years) for primary simulations and analyses; 2000–2018 for observational data comparison; 1901–2022 for TRENDY model simulations.

Methodology and Data

• Models used:
  • Customized Lund-Potsdam-Jena General Ecosystem Simulator (LPJ-GUESS) v4.1 (process-based dynamic global vegetation model with enhanced soil freeze-thaw processes and daily grass carbon allocation schemes, locally parameterized for QTP).
  • TRENDY-v12 project (ensemble of 13 dynamic global vegetation models for multi-model intercomparison).
  • Surface Frost Number model (empirical method for permafrost extent estimation).
• Data sources:
  • Climate Forcing: China Meteorological Forcing Data (CMFD) (daily, 0.1° resolution) for precipitation, specific humidity, surface pressure, air temperature, wind speed, and downward shortwave radiation (1979-2018). Climatic Research Unit gridded Time Series (CRU TS) v4.07 (0.5° monthly) for precipitation (1901-2022). National Oceanic and Atmospheric Administration (NOAA) for annual atmospheric CO₂ concentrations (1979-2018).
  • Soil Data: SoilGrids (250 m, upscaled to 1/8°).
  • Vegetation/Productivity (GPP): ChinaFLUX20 (annual GPP over China, 2000-2020), GOSIF v2 (global OCO-2-based solar-induced chlorophyll fluorescence, 2000-2018), NIRv (global GPP from near-infrared reflectance of vegetation, 2000-2018). Monthly GPP observations from 14 eddy covariance sites (39 site-years) across the QTP.
  • Eco-hydrology (ET, Runoff): Global Land Evaporation Amsterdam Model (GLEAM) v3, Simple Terrestrial Hydrosphere Model (SiTHv2). Annual runoff data from 12 hydrological stations (167 station-years) from China River Sediment Bulletin. Daily streamflow records from 4 Global Runoff Data Centre (GRDC) stations.
  • Land Cover: Annual China Land Cover Dataset (CLCD) for vegetation mask.
  • Permafrost Map: A widely recognized QTP permafrost map for model validation.

Main Results

• Observational data and model simulations consistently show that drought significantly reduced vegetation gross primary productivity (GPP) across the QTP, with observed mean GPP drought stress (DSGPP) ranging from -7.7% to -1.2% during 2000-2018.
• Under constant temperature, the 40-year rise in CO₂ mitigated drought-induced productivity losses by 5.7% (95% CI [-6.6%, -4.9%]) across the QTP. This mitigation was more pronounced in permafrost areas (15.3%) than in non-permafrost areas (1.7%).
• In the presence of warming, the drought-mitigating effect of CO₂ reversed, leading to an overall intensification of drought impacts by 5.2% (95% CI [4.7%, 5.6%]) across the QTP. This reversal was particularly strong in permafrost areas (a difference of +18.8% relative to fixed-temperature conditions) compared to non-permafrost areas (a difference of +8.1%).
• Warming disproportionately intensified drought stress in permafrost areas, showing a 13.4% difference in DSGPP between fixed-temperature and warming conditions, compared to 5.1% in non-permafrost areas.
• Warming offsets CO₂ benefits by disrupting vegetation water balance: while warming amplified the positive impacts of iCO₂ on GPP and water use efficiency (WUE), it also intensified ecosystem water loss (evapotranspiration, ET), especially in non-permafrost areas, and constrained these benefits during drought years.
• Grasses, which dominate permafrost areas, exhibited a stronger suppression of the iCO₂ effect by warming (difference = +91.6%) compared to grasses in non-permafrost areas (difference = +50.2%).

Contributions

• Provides a novel process-based perspective, integrating ecological modeling with multi-source observations, to disentangle the interacting effects of increasing CO₂ and warming on alpine vegetation drought responses.
• Quantitatively assesses the relative contributions of CO₂ and warming to vegetation drought stress, revealing that warming can reverse the drought-mitigating effects of CO₂.
• Offers mechanistic insights into how CO₂ and warming jointly regulate vegetation water balance, particularly highlighting the distinct responses in permafrost versus non-permafrost regions.
• Bridges the gap between retrospective correlative analyses and process-based understanding, informing future ecological assessments and guiding localized management strategies for the Qinghai-Tibetan Plateau and other permafrost ecosystems globally.

Funding

• Ministry of Science and Technology of China National R&D Program (2022YFF0801904)
• National Natural Science Foundation of China (32301383, 32471669)
• Zhejiang Provincial Natural Science Foundation (LR24C030001, LZ23C030001)
• Key Research and Development Program of Zhejiang (2024C03244)
• Fundamental Research Funds for the Central Universities (226-2024-00187)

Citation

@article{Lyu2026Warming,
  author = {Lyu, He and Wang, Peng and Jian, Su and Wårlind, David and Knauer, Jürgen and Teckentrup, Lina and Chang, J. and Xu, Xiyan and Chen, Chen and Zhang, Tao and Ni, Jian and Sitch, Stephen and Fu, Yongshuo and Medlyn, Belinda E. and Smith, Benjamin and Yang, Yuanhe and Jiang, Mingkai},
  title = {Warming overwhelms CO2-driven drought mitigation in alpine vegetation on the Qinghai-Tibetan Plateau},
  journal = {Communications Earth & Environment},
  year = {2026},
  doi = {10.1038/s43247-026-03308-2},
  url = {https://doi.org/10.1038/s43247-026-03308-2}
}