Chen et al. (2025) Global patterns and trends of vegetation water use efficiency inferred from solar-induced chlorophyll fluorescence from 2001 to 2020

Identification

• Journal: Agricultural and Forest Meteorology
• Year: 2025
• Date: 2025-10-02
• Authors: Zhichao Chen, Yuefei Huang, Xingan Chen, Chong Nie, Jianguo Wan, Shuo Zhang
• DOI: 10.1016/j.agrformet.2025.110865

Research Groups

• State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing, China
• Key Laboratory of Ecological Protection and High Quality Development in the Upper Yellow River, Qinghai University, Xining, Qinghai, China
• Key Laboratory of Water Ecological Remediation and Protection at Headwater Regions of Big Rivers, Qinghai University, Xining, Qinghai, China
• State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining, Qinghai, China
• Chinese Research Academy of Environmental Sciences, Beijing, China
• Joint Research Center for Yangtze River Conservation, Beijing, China

Short Summary

This study developed a novel satellite-based framework integrating solar-induced chlorophyll fluorescence (SIF) and plant physiological theory to globally assess vegetation (WUET) and ecosystem (WUE) water use efficiency from 2001 to 2020. It revealed distinct global trends for WUET and WUE, attributing them to CO2 fertilization, vapor pressure deficit, and vegetation structure, and projected future changes under climate scenarios.

Objective

• To develop and apply a novel satellite-based framework, integrating solar-induced chlorophyll fluorescence (SIF) and plant physiological theory, for the global assessment of vegetation water use efficiency (WUET = GPP/Tr) and ecosystem water use efficiency (WUE = GPP/evapotranspiration) from 2001 to 2020.
• To attribute the observed global patterns and trends of WUET and WUE to key environmental drivers and project their future changes under climate change scenarios.

Study Configuration

• Spatial Scale: Global (primary focus), site-scale (for validation).
• Temporal Scale: 2001 to 2020 (historical analysis), through 2100 (future projections).

Methodology and Data

• Models used: A novel satellite-based framework integrating solar-induced chlorophyll fluorescence (SIF) with plant physiological theory for simultaneous estimation of Gross Primary Productivity (GPP) and transpiration (Tr). Coupled Model Intercomparison Project Phase 6 (CMIP6) models for future projections.
• Data sources: Satellite-based Solar-Induced Chlorophyll Fluorescence (SIF), flux tower data (for site-scale validation), CMIP6 model outputs.

Main Results

• The novel SIF-based framework demonstrated strong agreement with flux tower data for both WUE (R² = 0.615) and WUET (R² = 0.573) at site scale.
• Globally, vegetation water use efficiency (WUET) increased from 2001 to 2010 due to CO2 fertilization but stabilized from 2011 to 2020 as rising vapor pressure deficit (VPD) offset physiological gains.
• Ecosystem water use efficiency (WUE) continued to rise from 2001 to 2020, primarily driven by increased transpiration-to-evapotranspiration ratio (Tr/ET) linked to vegetation greening (R² = 0.776 with Leaf Area Index, LAI).
• Attribution analysis revealed that atmospheric CO2 concentration and VPD together explained over 70 % of the interannual variation in WUET.
• Future projections using CMIP6 models suggest that WUET will closely follow changes in the CO2-to-VPD ratio (Ca/VPD).
• WUE is projected to increase through 2100 under high-emission scenarios (SSP370 and SSP585), supported by continued CO2 rise and LAI-driven increases in Tr/ET.

Contributions

• Introduces a novel satellite-based framework that integrates SIF with plant physiological theory for simultaneous global estimation of GPP and Tr.
• Provides the first global assessment of vegetation (WUET) and ecosystem (WUE) water use efficiency trends and their distinct drivers from 2001 to 2020 using an integrated SIF-based approach.
• Highlights the significant utility of SIF for large-scale carbon–water coupling assessment.
• Underscores the critical need to jointly consider atmospheric dryness (VPD) and vegetation structure (LAI) when evaluating ecosystem responses to climate change, differentiating the mechanisms driving WUET and WUE.
• Extends the analysis to future projections using CMIP6 models, offering insights into long-term carbon-water coupling dynamics.

Funding

Not specified in the provided text.

Citation

@article{Chen2025Global,
  author = {Chen, Zhichao and Huang, Yuefei and Chen, Xingan and Nie, Chong and Wan, Jianguo and Zhang, Shuo},
  title = {Global patterns and trends of vegetation water use efficiency inferred from solar-induced chlorophyll fluorescence from 2001 to 2020},
  journal = {Agricultural and Forest Meteorology},
  year = {2025},
  doi = {10.1016/j.agrformet.2025.110865},
  url = {https://doi.org/10.1016/j.agrformet.2025.110865}
}